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day the book is kept overtime.

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be collected for eachSENSATION AND PERCEPTION
IN THE HISTORY OF

EXPERIMENTAL PSYCHOLOGYTlie Century Psychology SeriesRichard M. Elliott, Editor

SENSATION AND PERCEPTIONIN

THE HISTORY OF
EXPERIMENTAL PSYCHOLOGY
By

EDWIN G. BORING
Harvard University

APPLETON -CENTURY- CROFTS, INC.
NEW YORl^CoPYRicaiT, 1942, by

D. Appleton-Centuby Company, Ino.
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m iMirls

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PRINTED IN THE^ UNITED STATES OF AMERICA
E-iioogTO

HERMANN VON HELMHOLTZPREFACEIt

was in 1924 that I resolved to try my hand at writing a his-

tory of experimental psyc/iolog/— as that term was then used todesignate human adult normal generalized ‘orthodox’ psychology.
I wanted to start with themen and the schools as an introduction

and then to trace the history of experimentation and thought in
the fields of sensation, perception, feeling, emotion, learning, mem-

When I found in 1929 that theory, attention, action and thought.

introduction on men and schools was a book in itself, I publisheditunder the title originally planned, A History of Experimental

Psychology, realizing only later that this title is somewhat inapt,
since I

had not yet got to the experimentation in experimotrlal

psychology.

At Ural time I had, however, some doubts about my ability
ever to go farther, for the subject of visual sensation seemed tome so vast and complicated that only a specialist might undertaketo assess its discoveries and abstact Us history. In 1935 1 ventured,

nevertheless, to try

my hand at the chapters on vision and subse-

quently concluded that it is not impossible for a layman likemyselfto createa sound perspective of the progress of visualscience. Whetlrer I was ri^t or wrong, the reader of this bookcan now judge; but at any rate I have kept on to finish the othersenses, finding once again that ‘enough to make a book' had to ita certain amount of unity. The fest two chapters of the present

volume I have written last. They are less thorough than the others,
for I present them oirly as

an introduction to the next thirteen,

which constitute the body of my undertaking.
There remains the possibility of a third book, if the receptionof this second one should justUy it. It would recount the historyof experimentation in the other fields—feeling, emotion, learning, attention, action, thought. It could, perhaps,

be organizedabout the ‘dpamic principle' that comes into psychology withthe determining tendency and with ‘choice.’ In that history

TU

itPREFACE

viii

ouglit not tobe necessary to go buck to the beginning of the

sevcntoentli century, Is there any cxperiinenlal p.syehology ofmotivation before 1850? Hypnosis, to Ire sure; but is there anything else? Such a trilogy would inclcacl complete

my original

make no promises. This more leccnt history isnecessarily less secure, less ready for delrrreatiorr, than what is
intention; yet I

older,
It is a nic£ question as to when the past becomes history, as tohow old it needs to be befor'e a first stable perspective of it canbe limned. In 1929 I felt secure in my evaluations up to 1910,
uncertain about tbe penultimate decade, and quite tentative aboirt
the ultimate decade of the 1920 s. Now, ten years later, I find drat
the same relations still hold. The history of sensatioir and perception seems tome clear up to 1920, not quite so certain in the next

decade, and since 1930 definitely confusedby itsteceircy. In

part this sense of certainty about the ante])emiltimate decades

must be due to tire fact that opinions are not yet ci-yslalliz(>(l nor
tire perspective

established by conveutiou. An imporUml discov-

ery of 1912, if still important hi 19-12, is no longer likely to

liini

out to be an artifact, oven dunigU it may need reliilerpretalion.

Thus, in this book, it has been my Intention to sl(»w down at
1920 and to slop at about 1930 except when the

momenlnm of—

discovery is irresistible

as it was in the p.syehophysiology of hear-ing, when seventy-year-old problems

begun to come up for solu-

tion in dre 1930’s. Nevertheless, the reader shoirld not trust•after 1930, since I

mo

do not trust myself. No man can see clearlyso near his face, and writing history is a matter of selection.

Indeed, so much a matter of sdectionisdie preparation ofan historical text, that I am sobered by the resjronsibility. The
text of 1929 has existed long enough forme to see how a moodthat detennined the choice of an afternoon’s exposition cun fix

the ‘trath’ of a certain matter upon graduate students for years
to come. With industry and patience

one may avoid the falsifica-tion of facts, but those virtues are not enough to make one wisein choosing what to ignore. For that one needs also wisdom andthe integrity of objectivity, and who knows for sure whedier hecommands such?

<

In a strict sense neither this bodlfisor its predecessor of 1929isa history—an historian’s history. In both I have written solely

toshow how psychology came to be as it is now. If any event

PREFACE

ix

important in the past has no demonstrable indirect effect lipon
the present, then it should be omitted from a book tliat tries torecreate the past merely to explain the present. As a matter offact,

however, the continuity of thought is such that nearly all

events important in the past have had some effect on the present,
for good or ill or both, as the case may be. The effect may, nevertheless, be small,

Mountains in labor may bring forth mice. One

such mountain was nativism-vs.-empiricism, and another wasWeber’s law. If I were trying accurately to reconstitute the psychology of the late nineteenth century, I should have to drawthese mountains large, letting
fertile objects.

them obscure smaller and more

Actually, I have painted

them in small, and in

the distance as seen by the naked eye from the point of view ofthe present, whereas some other remote details I have enlarged
telescopically. But that, I realize, is not quite History,

For a book of tin's sort the author leads original sources, discusses them, relates them, cites (hem. Thus a question arises about

the original sources which he cannot see; should he citethemat second hand, sharing, in that fasliion, all his knowledge wiih(lierender? Or should he refiain from mentioning what he lias

not rend, since second-hand citations lend, as we all know, toperpcUmlc error? I have resolved this dilemma by distinguishing two lands of references.

AH the originals that I could findin Greater Boston I have seen myself, and many other important
texts I

have had from Washington. Less important items I havecited at second hand, labeling the citation "[n.v.],” a symbol whichmeans “not viewed" and hence “not verified.” I have been conscientious. If the first edition is unavailable to me, I noteitas“n.v.” and then cite, perhaps, the second explicitly. Let the critic

who thinks I should have cited nothing that has not been under

my nose merely imagine that these “n.v.” references are not in
the book. With but a little more undocumented dogmatism, they

could all have been omitted.

Let me observe here that I have been repetitious, bothmallusions to matters discussed more thoroughly in other parts ofthe book and in the reiteration of dates. It is a pleasant fiction tobelieve that most readers start at the beginning of one’s

book

and read through to die end, remembering everything. ActuaUysuch a book as this is consulted more often than it is read, or is,at best, studied in a random order. Thus I have sought to add to)

PREFACEX

the comfort of the adventitious reader while disUubinjf as little
as possible the continuous reader.

When tliere is an hnpoilaiiland extended discussion of a closely related mailer in another partof the volume, I give a cross-referenceby page, On the other

hand, when the related matter is incidental, I allude to it with a
phi'ase that indicates that it is to be found elsewhere (“as we haveseen” let the reader then use the index if he can not guess theplace ), or else I reintroduce die data casually in dependent clauses.

In this way the adventitious reader benefits without knowing it,

and the continuous careful student can perhaps be deaf to theseechoes if he has had this explanation.

Dates I have scattered irough the text with ahnost endless
repetition,tobecause I do not expect the reader to know them orremember most of them. The reader needs, I believe, to be
and repeatedly, explicit temporal

given, constantly

so that he can, if he will, pause to think;orientation,“That was just before

so-and-so published such-aud-sucli; he might have known beltera few years later.” Tlie reiteration ol “Albrecht von Haller ( 1 Ttill“Johannes Miillor (1838),” “K. II. Weber ( ISdO)” may seem tire-some, but at least it makes “Haller (1758)," “Jobunni'.s Miiller(1826),” "E. H,

Wober (1852)” slaiul out with u warning llmt

ihere is something unusual about the eitalion.

In this book there is one pcr.sisU‘nl muieln'mii.sin which 1 haveallowed myself under what I dtink is jnstidalile literary license.
I wi'ite,“Wundt found in 1859

.

.

.

,”

when I mean, “Wundt pub-lished, in the part ol tlie BoUrage that cumc out in 1859, the results of certain experiments wlildi, for all I know,

ho may have

performed in 1858 or even earlier.” When I know there is latency,
however, I indicate it. I would not find Helmholtz doing anything
in 1896 when the second edition of the Optik appealed two years
after his death;nor would I find the aging Galileo formulating

the frequency theory of pitch in 1638 (the year in which he published the finding), when Mersenne, his pupil, had already beenable to refer to the result in 1686 (the year in which he publishedhis finding).

Mv debts ate m;imei'0U3 ^d s^e are vague. Should I mention
here my permanent debt to Titchener, who determined my interests, set

my drives? I wonder if I may not have been unconmy professional life on his, as I think he didsciously modelingPREFACEri

on Wundt’s. Ought I not here to give thanb for Libraries, whopatiently serve all

who come with honest ignorance? When I

think of the Libraries, I know myself for a rewrite man, for thisbook is but an index to a minute section of (he Harvard College
Library and the Boston Medical Library, with addenda for the

Army Medical Library. Libraries stand out as a tremendous reason for the humility of such authors as I. And then what about
the Great Prime Mover of all intellectual activity, the Zeitgeist,
without whom no man wouldtbiirk as

he does, nor have histhoughts make sense? But I have done the Zeitgeist honor throughout the pages of this text and of the other in 1929.

My greatest determinate debt is to Mrs. Katherine Frost Bruner,
who read and revised eleven of these chapters, pushing me measurably toward felicity of expression, even though I have not as
yet attained her ideal. She, Mrs. Dorothy Telfer Delabane andMrs. Jane D. Morgan have slaved in different years on the prepa-

and my wife, Mrs. Morgan and Dr.
my editing friend, have faithfully battled against my errors

ration of the manuscript,
Elliott,

as Ihcy read tlie proofs. The cliapteis on hearing and the sections

on attributes and psydiophysics were read by Dr. S. Smith Stevens

who substituted tmth for my fletion in more places than one. How
many persons have to help when a book is writtenl I am very
grateful to tlrom all.

There is also a debt that I owe to Society-at-Large, which has
giving up a fruitless struggle to have me spend my summer vacations in Maine, left me in happy peace working on thisfinally,

book ill Cambridge through Julys and Augusts. A studentlessmonth in the summer is worih five of Harvard’s winter hurlyburly. Sometimes I fear that, if Harvard does not give up trying

to turn itself from an Institution of Learning into an Educational
Institution, we may have a generation of professors whose duty
it willbe to disseminate information which they have not the timeto acquire. But fortunately they will still have their summers.

No reader of this book will need to ask why I have dedicatedHelmholtz. There is no one else to whom one can owe so

it tocompletely the capacity to write a book about sensation and perception. If it be objected that books should not be dedicated tothe dead, the answer is that Helmholtz is not dead. The organism

can predecease its intellect, and conversely. My dedication asserts

PKEPACE

xii

HolnJioltz’s immortality— tlie kind of inimortalily thal remains tli('

unaoliievable aspiration of so many of us.

E.G.H.

December 6, 1941
Cambridge, Massachusetts

Noten.v,, inlha Notes atllio

owls ofllio eliaplors,means "iiiit viewed'' mid,wmrees lire eilisl

therefora, "not voriflod." It is used wluiii wnavullidili'at second hand.

The abbreviations of tho names of Joiinitils follmv, In uenetid, ibe forms
given by iho World List of Scientijia VrrMli'iik, bul a few iHineesiioiw
have been made for tho less .wphteUeuled reiidens.
The Fhontisheob shows Hchnhollz in W/O, It is reptodiieed, witli pennlasion, from the coppcc-plale reproduction of Fume, von Leulmeh's portrait

in Helmholtz's PhyslotogUial Optics, Eng.
of America.

trails., 1,1024, Optical ijocioty

CONTENTS
PAGE

CHAPTEn 1. Sensation and Febception

3

Sensation

4

Perception

13
19

Ath'lbutes

Natlvlsm and Empiricism

28.

Psychophysics

34

Notes

45

Chapter 2. Physiology op Sensation

53

Ncrvo Conducllon

53

Sensory Conduction

62

Spoclflo

Nerve Energies

68

FrojccUou

78

Isomorphism

83
91

Notes

Chapter 3. Visual Sensation; BECiNNiNiis

97

BoCnro Newton

97

Isaac Newton

101

Thomas Young

107

GoothoI

From Goethe to Holmlioltz

112
113

Alter Helmholtz

119

Notes

121

Chapter 4. Color and Its Stimulds

128

Color and Its Dependence on the Stimulus

126

Aightnees and Intensity

132

Weber’s Law

136

Color Mixture

139

Color Diagrams

145

Notes

149

Ciiafter S. Visual Phenomena

155

After-Images.

157

Adaptation

160

Contrast

165
171

nSjjrect Vision

X/uminosity of the Spectrum and die Puiklnje Phenomenon

,

.

.176

Color Blindness

182

Notes

190

CONTENTS

xiv

r\ou
ItW

Chaptitr G. Colon TimonY
Tlic Young-Helnilinllj ThL'L)ry__

ISM)

Tlic Duplicity Theory

21B

The Hering llieoiy.

21)(iModifiontions ot the Fundiimenlnl Thcniies

210

Modem Visual Theory

2U

Notes

210

.

.

.

Chapteb 7. Visual PERCEP'noM OF BinutiiN.sioNAi. Si- rcE

.

.

.221

.

Tire Retinal Image

222

Singleness ol Vision and the Horopter

22G

Eye-Movements

230

NaOvism and Empiricism

233

Geometrical Optical Illusions

230

Dynamical Gestalten

2-10

Gestalt Psycltology and tire Laws of Form

RiSE

Notes

2.57

/CiiAPTm 8. Visual PmcErTOiN or Dmmh ANrr Di'.i.rNi'K

.

.

.

2fi3

.

203

Secondary Criteria ul Disttuioe

Convergence and Accoininodulloa

271

Stereoscopy

202.

Size and Distance

200

Ttldlmonslonal Dynamlc.s

21111

Notes

illli)

CnApTEn 9, PsYCiioiuiYSKM oi*Tonk
The Origin of Musical Notes

,312

312

Physical Acoustics

321

The Limits of Ilearhrg .

332

Dlfierential Sensitivity

33fl

Notes

8‘IH

Chafieb 10. Aumronv PEncEunoN
Boats and Comhination Tones

352
352

,

Timbre_3,57

Tonal Fusion

359

Noise^

363

Masking

865

Vowels "367

Attributes of Tone

375

Auditory LocalizaUotL

381

Notes

3H2

Chapteb 11. Aunrronv Tnnonv
Before Helmholtz,,,y, 3!)9',400

Resonance Theory of Hearing

404

Other Theories of Hearing

411’

Chapter 1

SENSATION AND PERCEPTION
ET us begin with a£r4cis.

I

The concept of sensation became important in human-^thought by way of philosophical empiricism: knowledge

comes to the mind through the avenues of the senses. For this reason empiricism has always been allied to sensationism and, among
the British empiricists, to tlieir associationism. Physiologists turnedto the problems of sensation after Bell’s and Magendie’s discovery(

1811-1822 ) tliat sensory and motor nerves are different—the Bell-

Magcndie law. Then Wundt, a philosopher ‘founding’ a ‘new"
cxpcrimcnlal psychology, derived die structure of systematic

psychology Irom the British associalionists, making sensation thebiusic ('Icmeul olconsciousness.

Ln the meantime

both the Scottish philosophers and the later

English associatiouisls had come to distinguish perception Irom

sensation— scasatiou as the bare content given to mind, perceptioniis

the upprohcnsioii of an object. An object, they contended, ismore thim a simple ‘given,’ for tlie mind refers to it or ‘intends’ it;
an object is actually a meaning. Thns the empiricists undertook
to explain perception by the association of sensations and images.
It isassociated compounds, they drought, that constitute knowl-edge of an object.

Wundt, consequently, in constructing his system put into it
the sensations as elements and the perceptions as complexes of
sensations, in that way fixing upon psychology for a long time thenotion that the synthesis of elements into complexes is ^e proper
explanation of objective reference and thus of conscious meaning.
Later, however, Kiilpe and Titchener tended to break the sup-posedly elementary sensation down into attributes, which finallyappeared in psychology as the abstracted dimensions of consciousness, ’They added, moreover, space and time to the list of attributes,

whereas Wundt had had only quality and intensity, and in sodoing they did much to erase the distinction between sensation
3>

SENSATION AND PERCEPTION

4

ancT perception, for Wundt luid regartlod nuality and inlonsity as

simple and sensory, but spaco and time as modes of complex perception.

The nativists also, from Hering on, made extension ‘given’ andtherefore simple, and dieir descendants, the Gestalt psychologists,have in the present century denied both the distinction between
the elements and their complexes and also the existence ol meaningless conscious contents, _In Gestalt psychology, therefore, per-igeption has absorbed sensation, whereas in physiological psy-chology sensation has absorbed perception.

The Gestalt psychologists and tliose others who have inherited
the tradition of introspection from Wundt tend in the present day
to speak of phenomena

and phenomenal experience. The physi-

ologists spealc of sensory processes and mcchanitiiis, considering

them either for thch own sakes or as correlates of cxpeiieiice. In
addition Uiere have been the behaviorisls, who later gave place tothe modem positivists, They find that seieulifie ktiowledge about

what used to be called sensation is awpiiied only when the organ-

ism-human or anhnal—makes discTiminatimis, and lints

they

substitute discriminalnry reaction lor stnisaliou.
It is with tho history of all those occurrenuus lluiL the first partof this chapter is concerned,

Sensation

An empiricist is apt to bo a sonsalionist, bcoansn it is by way ol
the senses that themind has experience of the external world,

Both of these doctrines are vary old, Heraolilos (5th century d c ).

said thatknowledge comes to man “through tho door of.

dm souses.”and Protagoras (oa. 485-411 b c .), the first of tire So])hists, ex.

tended this view, maintaining that the entire p.sychic life consists
only of sensations, It was the Stoics who first used the figure of thetabula rasa, the blank wax-tablet of the mind upon which experience writes. Sensations, they held, are impressions of outer
things upon the mind. These early Greek philosophers had thisempiricism, but it was not the dominant philosophy of tho time.

The Greeks also had a theory of perception that still hama^thepresent. Empedocles (ca, 490-ca, 435 b c .).

supposed IhaMPots

give off from their surfaces or pores effluvia, which act

uim diesenses to furnish knowledge of the outer world, Demooritos (ca.

EAHLY SENSATIONISM

54G0-ca. 370 u.c.) iincl Epicuras (ca. 341-270 d.c.) desciibed tBese
projeclioiis as faint images, simulacra or oiclola of the objects which,being conducted to the mind, give it acquaintance with the objects

which they represent, These men wislied to explain why perception is covi'cot, why sensory knowledge is valid. To us tlieir theory

sounds naive; nevertheless it is natural to attempt to explain representative adequacy by similarity. Johannes Miillor was still having
to fight Democritos and Epicuros in 1826 when he argued diat themind, being inside Ore body and thus in dii'eet contact only withits

nerves, perceives not the objects themselves, but merely thenerves which the objects affect. Wertheimer', too, was opposing thisancient view when, in 1922, he argued against the ‘constancy hypodicsis,’ tire insidiousand insistent belief that experience andstimulus arc necessarily alike.

Empiricism came into its own after Thomas Hobbes ( 1651 ). Objecting totire

doctrirre of urnate ideas,

Hobbes wrote; “There isno conception in matr’s mind which hath rrot at first, totally orby parts, boon begotten upon the orgatrs of sense.” Then, after
Ilobbos, ciuno John Locko with his Essay Concerning

Human

UiulmUmding ( 1690) in which ho depicted tire mind as a pieceof whito paper

upon which oxputiouco writes. For Locke thomental olcuicnt was the idea, which comes from oxporictreo by
sousatlou or rclloction. liejlccUan, which “might properly enoughbo called internal sense,” was his ter-nr for the mind’s knowledgeof its own operations. Indeed, it was this belief in an inner sense,
the belief that tho mind always knows what it is doing, tlrat tendedtoprevent empiricists from bocomirrg full-fiedged sensationists,from nssrtraing tlart all knowledge comes from the outside. For
Locko, ideas were such entitira as whiteness, motion, elephant,

army, sheep, murder, gr-atltude; and of these, whiteness is a simple idea, whereas sheep and gratitude are compound, formed, as

Locke presently put it, by the association of simple ideas. Such a
psychology is an cmpuicism, an assodationism and also a partial
sensationism. Sensation is in it the primary source of knowledge.

Bishop Berkeley ( 1709, 1710 ) , with his idealism, followed Locke.

He held that mind is the ultimate reality, that the ideas are primary, that percipi is esse. The ideas he classified in respect of Aristotle’s five senses,

holding that no idea can be common to twosenses and thus establishing the basic classification of sensationistio psychology—sight,

hearing, smell, taste, touch. In his NeuiSENSATION AND PERCEPTION

8

Thhry of Vision lie consiclorod at lenglli the visual pereeplion ofmagnitude, pointing out tlmt one cannot tell ihe si'/e of an object
without taking into account its distance, and that awareiu'ss of distance depends in turn upon awareness oi the separation between
the pupils of the eyes (convergence), the straining of the eyes infocusing (accommodation), and die blurring that occurs

when

the focus is poor. The perception of magnitude would, therefore,
involve all these items which, he thought, come to be united inexperience (association). Berkeley also had a theory ot objects

which closely resembles Titchener’s context theory of perception(pp. 17 f. ) We perceive, he said, one idea, “not immediately of it.

self,” but “by means of some other idea.” Thus the idea of a coachmay come into perception by a visual idea if one secs the conch,
an auditory idea if one hears it rumble up lo the door, or a tactualidea if one enters
sensations,it,

In other words, these ideas arc originallyand sensations arc thus the primary coustituenls ol

mind.
After Berkeley came David ITiime ( 17.80-17*10), who .stmglil to“restore the word, idea, to its original sense,from whicii Mr.

Locke had perverted it,” IIo eallod the .sensory and perceptual dataot mind impressions, using the word Idea for the “laint ixipies" ol

impressions which occur in memory and hnaghuiliou. Like laieko

and Berkeley, he believed in ooinplox ideas, .syuthe.sized by association, whidi is a “gentle force” ot altraclion that unile.s the sim-

ple ideas. Thus Hume, establLshiug the distinction between sensation and image, also furthered the progress of sciisatlonism.

Hartley (1749), the last of the cm'ly empiricists, contributed tothis school a paraUelistic dualism of vibrations in the nervous sys-tem, correlated with sensations and ideas in the mind. The notionthat physical action in the nervous system must be vibratory he got

from Newton, holding further that sensations depend upon grossand ideas, theii' copies (cf.
Hume), upon diminutive vibrations (“vibratiunolcs”) in the brain,
vibrations in the peripheral nerves,

Both the diminutive vibrations and ideas combine. Hartley said,
according to laws of association. He stated these laws in detail forthe vibrations and then repeated them all for the ideas. Thus he

was not only making empiricism associationislic, but ho was also,
by his psychophysical parallelism, making sensation depend ovenmote upon the properties of the nervous system than had Berkeley.
This is not the place for a history of sensationism in relation to—
LATER SENSATIONISM

7

ompirioism and associationisni. Wc must, therefore,
selves at tin's point with but brief mention

content our-of the contributions of

the Fieiich School, the Scottish School and the later

English asso-

oiationists.

Descartes ( 1G62 ) had begun the mechanistic
tradition in F rancB.
The body is a machine, he said, a machine which “can be incitedby the external objects which strike upon its organs of sensetomove it in a thousand different ways " He drew the analogy be-

tween man and certain, dien popular automatons, whidr moved

when an external stimulus actuated a device that released themoving mechanism. Condillac (1754) used a different analogy
establish liis sensationism. He conceived a statue inlocked, one by one, the senses—

towhich he un-^first smell, then touch, and so on
showing how its mind would be generated through this constant

addition of more and more sense-experience. Condillac’s contemporaries,

La Mettric and Bonnet, wrote in a similar vein. La Mettrie(174iS) described f/iomme DMcJiine and Bonnet(1760) conceived

iiidi'peiidently Condillac’s figure of the statue. Cer tainly the French

liad no doubt that knowledge comes from sensation and that sensation occ'ur.s by way of the sonso-organs.

Thomas Reid, the founder of the Scottish school of faculty
psychology, was aiiothor to establish the primacy of sensation inp.syehology, oven though (see next section) he was principally con-cerned to prosorve the God-given perceptual faculties from reduction to mere scusatiou. His Inquiry into the Hitman Mind (1764)has, besides the introduction and conclusion, only five chapters,

troatuig respectively of the faculties of smelling, tasting, hearing,

touch and seeing. Psycliological sensationism of the next century

and a half may well be said to have begun here with Reid, eventhough its materialistic nature echoed the defeat of his fandamental purpose. Dugald Stewart (1792-1827), the second important writer in this school, reenforced Reid, but with less to say

about perception and much more about the intellectual powersof the mind. After him came Thomas Brown (1820), who brought
Scottish psychology into relation with associationism, thus formulating a systematic structure that has many similarities to Wimdt’s

and Titchener’s, at least in respect of the relation of perception tosensation.
It isJames Mill (1829) who begins the later English Schoolwith what is often regarded as the culmination of associationism.

SENSATION AND PEKCEPTION

8

pictured simple ideas as compounded by association into complex, and complex into more complex, and so on np lo tlw' mluctio

ad absurdam diat “the idea called Everylliinj;" may somehow hean associative compound of every idea of a ihiiif'. Hartley's distinction between sensation and idea he accepted, hej'inniuj' his

exposition by a consideration of the sensations as the elementary

data of the mind, The initial eight sections of his book take up, inorder, first Aristotle’s five senses, then sensations of disorganization(pain for the most part), muscular sensations (the book was written just after Charles Bell had ‘discovered’ the muscular sense in1826), and sensations of the alimentary canal, In thus startingwith the elements he contr ibuted to a aislom for textbooks which

Wundt later fixed upon psychology for many years.
Bain, the later associationisl, did not write his The Srimv andthe Intellect until 1850, after physiology had begun to ail'uct thephilosopher-psychologists. Thus ho could ho the first to present a
full account of the nature and functioning of the nervous system, as

an introduction lo his book, which then discussed in detail thesenses—tlie oonvonlional live, to which lie added the anomalmis
oases of the “sensations of organic life.”

Meanwhile physiology had becomo alive to Uio iniportuueo olsensation. Haller's ElemiUa phyaiolo^itm (1757-1766) discussed

the senses fully, but it was Charles Bell’s discuvei'y in 1811 andMagendio’s confirmation in 1822 of what later eamo lo he called
the BeU-Magendie law that provided the effective stimulus forresearch.

They found that the nerves arc of two kinds, sensoiy

which lead to the posterior roots of the spinal cord, and motor

which lead from the anterior roots. Tliis dichotomy of nervous action into sensory and motor reminded the physiologists that themind’s sensations were as much their business as tho muscles’

movements.

Next Johannes Muller (1826) divided the sensory field into fiveby his doctrine of the specific energies of nerves. Aristotle had already made the division, of course, but Muller (Boll anticipatedhim, but that was not recognized at tire time) gave physiologicalmeaning to the difference by asserting that each sense has its own
specific energy and can respond only with its own peculiar quality.

Pressure on the eye gives li^t, light on the skin gives warmth, abbw on the ear produces a sound, (See pp. 68-72.) Here again
classification stimulated research.

SENSATIONS AS ELEMENTS

9

So il ciimc about in the middle of die nineteenth century dial thesense-physiology ol the physiologists and the sensationistic psy-chology of die philosophers were ready lor synthesis. Lotze’s
Mcdicinische Psijchologie (1852) was die first truly physiologicalpsychology, lor we can hardly count Hartley’s speculations about
vibrations and vibratiunclos as physiology. Bain’s was the next. It

was about 1858 that Wundt, then Helmholtz’s assistant at Heidelberg, first conceived the notion of a physiological psychology, a

new and experimental psychology that should apply die mediodsof science to die problems of the mind. Fcchner’s psychophysics(1860)and Helmholtz’s remarkably penetrating resear^es inphysiological acoustics (1863)and physiological optics (1856-

1866) reenforced him. So did all the other sensory researclies before 1870 which the present book recounts. Wundt, therefore, published the first edition of his classic foundation for the new science,
his Grundxiige dor physiologisclwn Psychologic, which became inits six

editions from 1874 to 1911 the standard handbook.

Eor .systematic structure Wundt drew upon the associalionists.
James Mill had overdone the matter of compounding. The idea ofI'lvoiytbing does not still have in it every idea of a thing, There is.synthesis. Tho whole is less, as well as

parts,

more, than the sum of its

John Stuait Mill had corrected his fatiier on this point,

Ideas, he had noted,

combine in a kind of mental chemisby, forthe parts are lost in tho compoimd which also has properties thatwore not contained in the parts, Wundt accepted John Mill’s pointof view. Ilis book takes up in order the nervous system, the psychic

elements (sensations in respect of intensity and quality, and, in the
first

and last two editions, feelings), tlie formation of the sensory

Vorstellmgen (perceptions of space, time and intensity), move-

ment and will, and finally the connections of mental processes(association, apperception, consciousness). Literally Vorstdlungmeans, of course, presentation, but for Wundt it meant a com-pound resulting from mental syndiesis and thus both perception
and idea. His psychology is, dierefore, an associationistio sensationism. Until he introduced the feelings as a second kind of de-ment (1896), aU mind was for him sensations and the results of
their .synthesis. It is small wonder that research on sensation at
first dominatedthe new psychology.

There was some little question in the early days as to the numberof senses upon which the mental life is founded. Of course there

SENSATION AND PEUClEPTlON10

are*at least five, but is touch pcrhups several senses? Charles Bellthought of the muscular sense, when he diaeovered it in lS2fi, as a
“sixth sense.” James Mill, asof sensation.

Weber

we have just seen, listed eight kinds(1884, 1846)

distinguished betvveen the

Tastsim and tlie Gemelngefuhl, dividing the TaMnii into Dntrksim, Temperatursinn and Ortsim(cf. pp.

465 f.). Helmholtz,

however, provided a method for settling this difficulty by defining

moddity as a class of sensations connected by qualitative continua. Colors lie in a single modality because they can bo placed ina single three-dimensional continuum, tlie color solid. Tones forma modality, but touch does not, for at least pressure, temperatureand pain are discrete.

No sooner had Helmholtz shown how to settle this question thanthe problem of the number of separate elements arose. Wundt andhis successors regarded the sensations as distinguished primarily

by their qualities, and Fcchnerian piiychophysics had furnishedthe j.n.d. (just noticeable dilleronce) as a means tor (ractiouating
qualitative coiitinua

and thus of counting sensations. Tht' early

and the early Titcheuer (1896) were tin' chiefcounters. Kiilpe computed tho existeuee ol 696 dlseriininably dif-

Kfllpe (1893)

ferent visual briglitncsses, 150 liuts, 1 1,063 tones, ihrei* touches,four tastes and numerous smells. Tllchouer listed 82,820 colors(presumably meant to bo tho volume of tho color pyramid, al-though the figure comes nearer to tho area of the surfair), 11,600
tones, a huge number of smeUs, fom' tastes, four cutaneous (imilities, two qualities

from muscle, one from tendon, one frcin joint,

three, more or less, from the alimentary canal, one or more fromthe blood-vessels, perhaps one from the lungs, one for sex, and one
for die static sense— a total of “more than 44,435." As against the

sixty-four then known elements of chemistry, themind seemed

pretty well provided for.
It must, however, be said that Lotze and Stumpf had alreadymade it clear that sensation can be regarded as a continuous function of stimulus, that the number of sensations in a continuum, likethe number of points on a line, is really infinite. The j.n.d. must be
an artifact of observation, and there must be more sensations tlian
j.n.d., because, if

two sensations a j.n.d. apart are each increasedby half a j,n.d., they still remain a jm.d. apart. There are, in fact-—

or at least there were then^no demonstrable quanta separated

critical points in the sensory continua.

byDECLINE OF SENSATIONISM

II

Iho iioxl queslion that arose about sensation concerned tlie
number of its attributes and, presently, the nature of an attribute.
Kulpe started this discussion in 1893 and it is not done yet. Since
the issue is, however, important and somewhat involved, we mustreserve its consideration until a later section(pp, 19-27),

Now we must ask this question: What has become of sensationinmodern psychology? For some psychobgists who followed

Wundt’s and Titcliener’s toadltion it disintegrated into attributes.
For Gestalt psydiologists, who have rejected all formal elements,
sensation was absorbed mto perception or at least into the phe-nomena of tlieir phenomenology. But for others it was translated
into discriminative behavior in the following manner.

The rise of animal psychology (1898 et seq.), m the days when
psychology was so sensationistic, meant that animals must be ex-amined as to their sensory endowments. That aspiration was realizable, If an animal can discriminate one tonal frequency from an-other, can learn to take food or to salivate for one frequency andto rojeet the f(K'd-bo.v or not to salivate for another frequency, thenpresumably he hears in the two otisos dilleront pitches. If he can‘teir oni’ color

from another by accepting one and avoiding theother, then he must make that discrimination on the basis of dif-ferent sensory experienws. After aU, this is the best way of working

with man. The language of intraspcctioii is never safe unless theroferenoos of its words are sure. If the color-blind person says thathe sees red, one still docs not know what he secs, especially if heasserts later that a given red and a given green are identical inhue. That is why Arthur Kiinig gave up introspection and hosted

only to color matches in his determinatioirs of color-bUndness. If

every color of the spectrum can be matched by a mixture of a given
pair of colors, tiren and then only is the subject surely color-blind,a didiromat ( see pp. 186-189) In this sense behaviorism antedates.

psychology.
Beliaviorism was invented by John B. Watson in 1913 because hehad been working with animals and had found that all these important problems of sensory psychology can be solved for different
animal forms. lie was tired of asking, after each experiment was
finished;

What sensations and otlier mental processes must thisanimal have if he makes these discriminations, if he behaves as hedoes? Tire facts of discrimination seemed to him enough. He

wanted, moreover, to investigate children, whose use of language,SENSATION AND PEllOEnTON

12

when they have any, is also unreliable. lie noted, in addition, that—the verbal method of introspection^inin Tltcliener’s laboratory, for instancethe Wui'Jibui'f' sehiiol and—seemedunrelialile in that

one laboratory often failed to confirm the findin^.solnnotlier.

Wliy should one not. he asked, throw all these inierences about
consciousness overboard and deal only with the actual data ofverbal behavior? To demonstrate the validity of bis point of view

he wrote in 1919 Psychology from the Stumljmint of a Selmclorisl,
including in it all the established psychological facts of any othertext but avoiding any reference to consciousness or to sensations.

Introspection he presented as verbal behavior.

After Watson America turned quite generally to behaviorism,

while Germany cultivated the ‘introspective’ phenomenology ofGestalt psychology. No one else ever quite succeeded in being ns

simple in his behaviorism as was Wntson, but American psychologists adopted the name and filled in their own specifications,

The growtli of mental testing helped lhi.s movement, lu'eause mental tests are usually little p.syclu)logiciil(‘xperiments nimn petsoius

whoso descriptive use of soioiitillo tenas’ ciuinol he trusted, 'I'he
tested— children, foreigners who cannot S))eiik Vingllsh, the insane, and also dto naive normal native adults— all behave for thepsychologist and thus tell him their minds. Holt, Wei!i.s, Tolmiui,Lashley and Hunter arc the important bcliavlorisis of the decade
after 1917, hut this olmptor is about sensation and not ahhiil .sys-

tematic psychology in general

Behaviorism ultimately disappeared, iu part bocauso in theand in part bccaiiso
modern positivism became the sophisticated substitute for it. The
1930’s it got to be accepted as psycliology,

older positivism of Mach and lirl Pearson—the view that thebasic data of science are the immediate observations and not theentities (light, electricity, sensation, attention)

infcrentially do-

rived from them—was superseded in the 1930’s by tlie positivism
of fhe Vienna drole under Schlick— the view that an entity derives
its

meaning from an understanding of the operations by which it isobserved and any term its meaning by analysis of the language

which gives it significance. This doclrine was called logical positivism in 1931 and is founded on the faith that meaning is secured
for a concept by its reduction to simpler, more fundamental, com-

mon terms. Before 1931, however, fh© physicist Bridgman had
undertaken (in 1928) to resolve t’’'lemmas of mpdorn relativity

SUNSATION AND DKiCRIMINATION

13(Ucoty liy insisting that physical entities, like space, can be undSvslood only in terms of the operations for observing ihcm.
All this was good gospel to the behaviorists, once they learned

about the movement. Tolman, the bohaviorist, now became an
operational bchavioiist. Others, not Bridgman, coined die term

operationism and used it in psychology. Watson’s doctrine was refined, purified, and also complicated. Sensation became nothing

more than the operation by whidi it is got, that is to say, discrimination. Tliis movement was, mm'eover, helped because theGestalt psychologists, Kollka and Kohler, came out against it, call-

ing it positivism and depreciating it, even while accepting some ofthe older positivism of Mach, which was, after all, an early formof phenomenology, Gestalt psychology, of course, wanted to keep

iramedialo experience in psychology, whereas the operationists

wanted to reduce immediate experience to behavior. The logicalpositivists

recognized this principle when they coined the word

heliamrislics. Thu controvoisy—for it remains a controversy—repfftseuts a fiuidamcntul temperamental dilforenco in scientific values

and is not yet cool enough to hasvdlo in an historical text like thepresent.
It

may be said, however, that tho phonomonologists are on se-ouro ground in that no one has a right to forbid thoir use of language, They want to keep immediato experience and could still

have lor use the old Wundt-worn sensations did they not deplore
the artifacts of analysis. The burden of the reduction of sensation
to its operational equivalent Ues, however, upon the operationist,and he claims to know all Hie formulas for the required translation.

Faced with sensation, he simply translates it, as Watson did. into
discrimination. Operationism, so ho claims, can eat sensation andhave it loo.

Perception
It wasThomas Held (1765, 1784) who^first insisted upon the

distinction betw een jensaJipfl and perception.

A sensation, he said,

although occasioned by an impression upon an organ of sense, is
not of the body but of the mind. Only a sentient being can have asensation. Perception,on the other hand, although it depends

upon sensation, is nevertheless much more than sensation, for it
includes both a conception of the object perceived and also an immediate and irresistijjleof the object’s present existence.

SENSATION AND PERCEPTION

14

Tfiis distinction, Reid went on to say, is difflcult only because of

the ambiguity of language; wc use tlie same words for both sensation and perception. For instance, the smell oi a rose as sensationisin the mind, but as perception the smell is in the rose it.self. If

the rose is to be perceived, both the conception of it and also theinstantaneous conviction of its objective exustcncc must bo added
to the sensation,

How dien, we may ask, docs this c.-epansion ol

sensation into perception come about? To this question Reid had

many things to say, yet none of tiiem was more final than that “theSupreme Being intended that we should have such knowledge of
die material objects that surround us.” Such knowledge, Reid
added, must be immediate and not the consequence of reasoning;(who "hardly ever leani towould be wholly“destitute of it.” Happily “God in his wisdom conveys it to us in aotherwise "the greatest part of men"reason"), as well as all infants and children,

way that puts all upon a level.” So sophistication is not a prerequisite of poroeplion. This exegesis of Reids—it is hardly aproof—means that faculties can Iw divscribed but not explulued.
For Berkeley’s and Hume’s .skcpticKiu he was .snbslilnling a faith
in the Ci'cator, a faith

which was, nevertheless, a seientilie ug-

nostioism.

Dugald Stcwai-t (1792) added little to this discussion except toadmit tlie negative diaraolcr of Reid’s ’theoiy’ of perception and to
defend it, but Thomas Browu (1820) brought to the problem thenew principle of association, or, as he preferred to call it, suggestion. Brown had something positive to say ns to how reference tothe external object is added to sensation in perception. An object,

he asserted, is something that has extension and that furnishes resistance,and knowledge of extension and resistance is gainedor, more likely, through those stmsa-—

through the sense of touchtions attached to our muscular frame which are usually considered

to be touch.

When the smell (sensation) of the rose is referred tothe extended and resistant rose (object), the reference ocairs be-cause the sensation “suggests” (by association) die tactual andmuscular feelings of extension and resistance. Certainly this insight into the Creator’s methods was scientifically an advance overReid.

Now we may turn to the assooiationists. In die preceding section,

we saw how the empiricists came to conceive of compoundideas as being built up out of simple ideas by associative fusion.

THEORIES OF PERCEPTION

15

and also how these compound ideas were, essentially, peveeptions,
Berkeley said that any idea is perceived by means of another idea,that a coach, being perceived hy sound, sight or toucli, is nevertheless tlic same coach because *lhe ideas intromitted by eadi sense,.

.

having been observed to go constantly together, are spoken ofns one and the same tiling.” James Mill analyzed the complex ideaof a house into the ideas of bride, mortar, rafters, planks, nails, to-gether with the ideas of position and quantity. That view failed,however, because tiie constituent ideas cannot be shown to be
actually present in the perception. They may be, it is true, poten-

tiaZy present, ready to be realized by associationif

the oppor-

tunity permits, but they are not immediately distinguishable in theperceptual instant.
Tliis point about perception’s being understood in terms of po-

tentialities was grasped by John Stuart Mill (1865). Accepting theevanescent and changing sensations as

ilie

immediate data ofmind, ho was Irying to explain how our belief in an external world

and in ponnaneul objects arises. An object is, after all, subjective,a creation of the mind, John Mill kid down as his premise theprinciplo that the mind is capable of expectation. Then he pointed

out that, though sensations may disappear, Iheh possiMities re-main present to the mind. If one sees, ho said, a piece of white
paper on the table and then goes into anotlicr room, tire sensations
disappear, but their possibility remains, as is evidenced by theirreourronce if one returns to the room to look again at the table.
Sensations are fugitive and transitory, but the T’ermanent Possibilities of Sensations” are enduring.

That is why the physical ob-

jects of the external world are stable, even though generated fromchanging sensations. They are simply the Permanent Possibilities
of Sensations.

We shall meet this notion of potential sensations

again in Titchener’s context theory of perception.
It wason this foundation that Wundt constructed the mental

chemistry of his Physiologische Fsychologie (1874 et seq.). The
sensations are the elements, to be studied in respect of their two
attributes, quality

and Intensity. They are combined into Yor-

sieIZungen—perceptions and the ideas of memory and of imagination.

The perceptual compounds are of three kinds: intensitive,

like the fusion

tones in a timbre or chord; spatial, like the com-bination of visual and kinesthetic elements in the binocular perception of distance;

and temporal, as in the structure of a heard

SENSATION AND PERCEmON

16

rlJythHi. If one asks

Wundt how these eomhinalions are effected,

one gets from him no simple answer. There are first the simple
facts oi fusion, as for tones. Similar to tliem arc the assimiliiHmis

of visual space perception, where the elements arc more alike inthe Vorstellung than they were separately, and also eonfrasts,

where they are less alike. Tliere arc also compliailions—a wordborrowed from Herbarl and established by the complication experiment—in which sensations from different sense-departments

are united. It is a complication to see ice as hard and cold, and theperception of visual distance is also a complication because it combines vision and kinesthesis. The simpler Vorstellungcn of memory
are associations, and indeed the rehanee of Wundt on the associationists is so gi'eat that one scents association often where he avoids

the terra. At the top of the system ai'e the apperceptions, the syntheses that yield agglutinations it they are relatively simple andconcepts when they are maximally complex. There is no refuting

Wundt. Half of his system consists ol sturdy facts, described by his
special terms. The rest is an army of arguments that iiisi.sl and ad-vance, tolei'ating no intorforeneo. If oiio slop.s to ponder Wundt

and then to question him, ho is alroady fiu' away, ihuiah'ring overthe horizon of his next chapter.

We do not need to mention hero Urentauo and the ael p.sychologists, who held that all conscious data are acts which vetor toa content tliat 'incxists’ logically witliin them, because this .school
did not greatly affect cxporimculal psychology, except in so far as
it is

one of the antecedents of Gestalt psychology. We must, how-ever, note briefly tltc riseand decUno of another antecedent ofGestalt psychology, the school of fom-quolitij. Von Ehrenfols in1890 pointed out that the fact of melodic transposition means thata melody exists independently of the tones which constitute it. If

you change all the tones and keep tlieir relations the same, youhave stfll the same melody. So with other temporal and spatial
forms.

A square is a square, whatever the length or color of thelines which form it. Such elements—the tones, the lines—ate theFmdamente of perception, von Ehrenfels said. Tliey form aU together

its

Grundlage, When diey are put together, however, aGestaltquaMtdt emerges, a form-quahty which is what is actuallyperceived. This form-quality

isreally a secondary element ofhigher order. Von Ehrenfels did not say much about the relations

among the Fmdamente, but Meinong (1891) did. He made it

PERCEPTION AND MEANING

17

among the founding contents which
detonnine the form-quality, which he called the founded content.
clear that it is the relations

His whole discussion has, however, a bias toward logic. Renaming
the founding contents infeitom and the founded content a supeHus,

he noted that superiora can come to be die inferiom of a still higher
superius, and so on up to higher and higher levels of complication,

Cornelius ( 1892-1893), who came next, objected to von Ehrenfels’
notion of emergent elements and argued that the fom-quality is

only a founded attribute. Since lie doctrine of attributes (see thenext section) was not clearly established at that time, his conception seemed safe and was a wise step away from Wundlian ele-mentism. After Cornelius the problem slipped back into experimental psychology with Schumanns researches on visual shape.

The next event ol importance was Titchener’s context theory in
1909. This was really a context theory of meaning, and Titchenerinvented it to combat the inEuenco of the imageless thoughts in
Kiilpo’s school at

Wiiraburg. Can one have an imageless unan-

schaullcho Bemssiheit, as Ach claimed at Wurzburg, or must themeaning of an awareness—a perception, for instance—always begiven in palpable imagery? That was the question. Titchener an-

swered it by saying that there are two stages to perception. A newperception has its speoiflo moaning only if appropriate imagery isadded. Recognition shows this relation. I learn that this face isVoltaire’s, and for a while the visual core of sensations, which are

the seen face, receives the Voltaire-meaning only if some image ofthe name—visual, auditory, vocimotor—is added as a context to thevisual core.

A hoard rhythm may be a rhythm only because it re-—anceives accentuation by the addition of a kinesthetic context

intermittent strain in a muscle somewhere. Kinesthetic contexts—or at least

may provide the cues to the visual perception of depth
so Titchener thought.

When the perception becomes old, how-ever, when it is habituated, then tire context may drop off and themeaning “bo carried in purely physiological terms.” By that phrase
Titchener meant that the meaning is there but unconscious.

A

conscious context may be needed before Voltaire’s face is recognized, but the familiar face of one’s wife is recognized instantly

before any context can accrue to tire sensory core. The unfamiliar

words of a now language may need tire conscious contexts of theirequivalents in the mother-longue, but it is not so for the words ofthe mother-tongue. The accomplished reader reads rapidly, get-

SENSATION AND PERCEmON

18ting the meaning of every word with no lime out lor contexts. Tims

Titohener argued, as had Berkeley, that it takes at least two .sensa-— any

tions (or images) to make a moaning

atrate at first. Later,when the perception is old, one sensation may be enough.
This dual theory of meaning was quite coiiviucing in roiipcet of

new perceptions. The pliilosophem had already decided that meaning is a relation, so why should not a conscious moaning be a conscious relation, the relation of perceptual core to context? Trouble
arose, however, for the unconscious meanings of the old percep-

By what right does one say that the meanings are ‘there’
when they are not consciously realized? John Stuart Mill could

tions.

have helped Titchener here, for he could have said that the meaning of the core is the Possibilities of Context, and tliat the test forthe meaning's having been ‘there’ is that the conlc.xt will arise if

given opportunity. A reader knows all along lire meanings of tirewords ho reads so rapidly, simply hccause he ean state each mean.
ing later if asked. The meanings arc potentially present. Titchener

did not, however, appeal to Po.ssibilitie,s. Jle relied rather on indirect tests. If a reader, having forgolUni the exact wortLs, can .still
state In all Its details llio mcaniug of the pumgmph, he imi.st have

known iho meanings of all the words as he rend. Ilis .siihs('(iuent
perfoi-mance shows it. To the piano player e.ieh note on a lint!

moans a natural, a sharp or u Hat, according to the signature inwhich the piece is written, but the player fe not conseious as heplays which of these three meanings each perceived note has forhim. The evidence tliat he had the meanings correctly lies in his

performance.

Telman (1918) was the first person to recognize the fact that
adequate behavior thus carries meaning and may be the effective
context in a perception. Titchener, never reconciled to behaviorism, would not liave accepted that principle, but of course opera-

tionism did. For it meauiug can have no meaning apart from themeans of testing it. The person or animal who responds in a specificfashion to a particular stimulus shows what moaning he attaches
to the stimifius—and to the sensation,if

one is talking also about

consciousness. The stimulus-object that an animal eats is food—tothe animal. Thus, although psychological operationism has had little to say directly about perception, its theory of perception is thestimulus-response relation. Response is the context that gives thestimulus its meaning for the responding organism. One sees, there-

ATTRIBUTES OF SENSATION

19*

fore, tliat a theory ol perception lies implicit inmodem psycho-

logical positivism.

The other modern school, Gestalt psychology, wliich abhors current positivism, does not have a theory of perception because it

holds tliat meaning is given immediately in phenomena. You can-not have a theory of the a priori. Lotze said that nativism is not atheory of space perception, because to say that space is given is

not a theory. No more did Thomas Reid have a theory of perception when he rejected Locke, Berkeley and Hume to say that per-ception is a faculty with which man is endowed by the Creator.

The phenomena of Gestalt psychology are intrinsically meaningful, as meaningful as

were Brentano’s acts and Kiilpe’s Bewusst-

hetten from which the Gestalt phenomena are descended.

To

perceive an object is simply, for Gestalt psychologists, to perceive

an object, a whole that is both more and less than the sum of its
parts, a datum that is not to be understood by analysis or by its

genesis in experience. Let us take an example. This table I per-ceive with dial book on it. 'Fhe perception of the book does notcover, so the Gestalt psychologist say, a hole in die perception of

the table. One can see that the table is continuous and that there isdouble representation—book and table—where the book lies. Nor
is the case different it I perceive honesty in a face.

Phenomenology

lakes what it finds and is content—as does aU science when it getsto its ultimates.

Attributes
Description is necessarily analytical. One cannot open his mouth
to describe anything without saying something about parts or as-

pects or properties in relation to one another.

A house is walls,door, windows and roof, with the roof on top and the windows anddoor in the walls and not in the roof. A stone is shape, color, wei^tand kind of substance in complicated relations. When such descriptive ultimates are general properties which can vary continuouslyor discretely, when they are, in short, parameters, they may, it one

chooses, be called attributes of die object described.
It is doubtful if Wundt meant much more than this when he'characterized sensations as having two attributes, quaUiy and intensity. Because he was immutably a systematist, he put these at-tributes into the structure of his psychology, yet he never formal^

ized their systematic position by giving them a name and stick-20 ^SENSATION AND PERCEPTION

ing to it, Merhnal, Ei^enschaff, Stimmimgsrharaktcr imd rvcn
BestondtheS, each in proper context meant allrihtilr for him. Th('
index of his Physiologische Psychologie contains no word meaning
attribute and referring to sensation or feeling, It was Kiilpe wholater began the formal doctrine of atlributos, employing the word

Eigens^oft. Wundt’s important elements were, then, snis.itions
with the attributes of qrrality and intensity. Feeling,

iwevor,1

varied in his system. At first (1874) it entered as a second elementwith its own attributes of quality and intensity. Then ( 1880-1893)

Wundt turned feeling into a Ihirf attribute of sensation hut left its
qualities and intensities intact, so that feelirtg appeared as an at-tribute with other attributes of its own (as Krrlpe later objected).

Finally (1896 et seq.)

Wundt changed feeling back irrto an ele-ment with intensitive variation in three (puditativc dirncmsioris.

The point about Wurrdl is tliat he did not care; lh{> attrilmU' forhim was not a formal term in tire system, like EJrmcnl, Vargang,
Vorslellung, Verbindung.
It remained, then, for Kiilpe in 1893 to give lonmil ri'eogiiilloii

to the attribute. First, he lislod the mirilnrtt's olseii,saliori.

They

are, he said, quality, Inkmlkj turd dumlioit for all live .seiisi's. withexiensiori added for vision and touclr. By atUling dui'nlloii ami ex-

tension to Wundt’s qrrality

and irtter),sity, Kiiljre ineveased ilie
number of attribrrtes to four, thereby making a eoucession Ur thenativists who beUeved that the basic data ol experienced space andtime are immediately given and not generated iir expt'rieuee( ef,

pp, 31 f., 234). Kiilpe kept Wundt’s spatial and temporal Vorstellungen, calling them colligations, but the poirrt here is that, notseeing how spatiality can be generated out of the notr-spalial, he

had to make extension primary as a sensory attribrrte.
Kiilpe defined the attributes in terms of their two properties.
They are inseparable from the sensation. A sensation that has

no qualify or no intensity or no duration simply does not exist.

Reduce any attribute to zero and the others disappear. The attributes are also independently variable; how else could they bo distinguished? It must be said, however, that Kiilpe did not give toindependent variability the same formal status tliat ho gave to inseparability.

He merely used the principle in his discussion of theattributes, and Miss Washburn stressed it later (1902).

Finally, Kiilpe denied that feelingcan be an attribute (Ge-filMston) of sensation, because it has attributes of its own(

quality.

THEORY OF ATTRIBUTES.21

intensity, duration), and because the fact that a sensation may beneither pleasant nor unpleasant, quite uncolored by feeling, showsthat feeling is separable from sensation, thus contradicting the pri-mary ciiterion of an attribute. Titchener thought that this argument of Kulpe’s was the occasion for Wundt’s changing his views
about feeling (between 1893 and 1898), but Wundt, Sie polemicist,
never admitted that.
This doctrine of attributes was clear but it did not prevail atonce. G. E. Muller helped to establish it by his formal distinction in1896 between intensive(i.e.,

intensity, durationand extensity)and qualitative sales. Nevertheless, four difficulties arose, as follows.
(1 )In the first place, it was not clear diat vision has the attrib-

ute of intensity. Colors have tlrree attributes, supposedly all qualitative;

hue, brightness and saturalion. All the colors, moreover,

can thus be placed in a three dimensional figure wliich employs
those attributes for its dimensions. Where is intensity? The blaok-gray-white series should be qualitative because it resembles the

red-oraugc-yollow scries, yet this series can bo created by changing
tlie

intensity of the illumination and Webor’s law (a law of in-tensity) can be tested out in respect of it, Tills matter is discussed
later (pp. 132-136).

(2) In the second place, Titdiener (1908), taking the com-

mon observation of Stumpf and others that low tones appear to belarge and high tones small, had added an attribute of volume totone. Although this addition might seem to be allowing tones toshare with vision and touch the attribute of extent, Titchener

thought of volume as qualitative because it varies, like pitch, withfrequency of the stimulus. If pitch and volume vary together, how

can they be independently variable and thus satisfy the second
criterion of an attribute? Titchener appealed to their manners ofvariation. Tonal volume seemed to him to change less rapidly thanpitch, at least in the middle of the musical scale. Later Rich verified this supposition by working out the differential volumic limens

for volume and pitch. Since die limen for volume is the larger, asmall change of pitch can occur without any change of volume.

That

is

independent

variability.

(See pp, 378 f.)

Still

later

Titchener got Gates to try to find a similar relation in the gray series

between visual brightness (quality) and visual
without much success (p. 134),,

intensity,

but

22.
(8)

SENSATION AND PEllClEFnON
The diird diflSculty is that psycholo[i;isls did not wish to hp

limited by foimal consideialions. They wanlcd freedom in Ihe useof descriptive terms. Especially did Ihis need appear in the woik

on tonal attributes that began about 1913. II tone.s, besides being
high and low, loud and soft, big and little, of long and short duration, are also bright and dull, they wanted to say so, without having

to decide whether brightness is a different attribute from pitch andfrom all the others. If tones resemble vowels, they wanted to saythat tones have the attribute of vocality, without settling the question as to whether vocality is simply pitch, or pitch

loudness -j-

volume, or what. (See pp. 376, 380.) This movement was the stirring of the new phenomenology in embryo, wanting freedom of description, objecting to analysis.

(4) Tire fourth difficulty was the mast serious of all, for it was
the raising of the question as to whether the attributes arc not,after all, the conscious elements, whether they arc not really separa-

ble in experience. Miss Talbot ( 1805)

had said that tlu'y arc not.

Miss Calkins (1899), however, pointed out that llu' atlrilmte.s are
the ultimates ol analysis and must, llierefore, be the elemenl.s. Miss

Washburn (1902) had composed this dilleren.’ii' by showing lluil
the argument is but one of deflnilion: because the attrllmti's' areinseparable from sensation and one another, sensation is the conscious ulliinatc; nevertheless tho attributes remain the logical nlti-

mates of description. It all depends on whether you are talking
about psychological analysis or logical analysis.

At this point (1904) Kiilpc himself turned on his own doctrine,
but first we must mention Titchener’s fifth attribute. Titchenor wasbothered by the concept of attention. It seemed to him a loose concept,

used without rigor as a catch-all for seemingly dynamic

events that could not be accurately described. lie said of it (asKrilpe had said of thought ) :Why not let observers simply describe

what it is like to pay attention? That was good positivism of theMachian kind. Whenever the observers attended for Titchenor,
they reported that attention is merely the division of the field ofconsciousness into the clear and the less clear (focus and margin,

Wundt’s Blickpunkt and Blickfeld). Consequently Titchener introduced (1908) the sensory attribute of clearness (later named
vividness, then attensUy) to psychology. A sensation can be clear(attended to) just as it can be loud or yellow or big.

Now we can go baok to Kiilpe. There is an early Kiilpe and a

KCLPE and TITCHENER on attributes
later Kulpe. Hie early Kiilpe {ante 1900),23

was the young man re-modeling Wundt’s system by substituting rigorous simplicity forwhat seemed to be Wundt’s ambiguous complication. It is to thisKiilpe that the doctrine of attributes belongs. The later Kiilpe(post 1900)

was the sophisticate of Wurzburg complicating his

own system and coming around to the less rigorous^^gative belief that thoughts, whatever they are on the positive side, are cer-tainly imageless. This was the Kiilpe who, with a freedom almost

phenomenological, commented in 1904 on certain experiments on
abstraction that W. L.

Bryan had performed in his laboratory.

Kiilpe and Bryan had shown their subjects, tachistoscopically, setsof four nonsense syllables. Each syllable had three letters (twelve
letters in each set)

and the colors of tire syllables varied at ran-

dom among four hues. 'The spacing of the syllables was not regular
but formed different patterns in die different sets. Four different
instructions were given to the subjects; to report (a) on the total

number of letters visible, (b) on the colors of the syllables, (c) on
the pattern formed by the syllables, and ( d ) on the identity of theletters seen. These four aspects of the perception are not the true

sensory attributes that Kiilpe listed in 1893, but they are attributes
in the sense that they were inseparable from the total object andcould be varied independently, Kulpe and Bryan found that theacceptance of one task meant abstraction from the others, that the
subjects, set to observe letters, for instance, might be whoUy un-

able to report immediately afterward on the colors, and that in sucha case they “believed that they had actually perceived no colors” at
all.

in

Thus Kiilpe concluded that ihe attribute may be all fliat exists
mind at the observational moment, that it is &e “conscious

actuality,” whereas the sensation or perception, the sum total ofthese attributes, must be regarded as the "psychic reality,” a scientific entity that is built

this

up upon many observations. In coming tooondusion he went a long way to justify Miss Calkins’ con-tention that the attributes are the true mental elements—the “ac-tual” elements, if not the "real” elements.

In 1913 Rahn published from Chicago a critical monograph dealing with the concepts of sensation and attribute in contemporary

psychology. He had worked with Kiilpe and was favoring Stumpf

and the later Kiilpe as against the earlier Kiilpe and Titchener, He
attacked Titchener’s attribute of clearness with the argument that
Kiilpe himself had used against Wundt’s attribute of feeling. Clear-

SENSATION AND PERCEPTION

24 .

ness, he said, can be olMorved— is, in fact, oliscrvcil in (“vpL'i'iiiicnls

which measure it; but observation depends upon attention, and attentionis,according to Titchoner, clearness, Hencetoobserveclearness is for the clearness to be clear, for the clearness to lave anIattribute of clearness. In respect of the other attributes he ap-

pealed to logic and to Kiilpes experiment on abstraction. Mveiy
psychophysical experiment on sensationisaceomplLshcd nndei

some set to observe and to judge a particular attribute. All that theobservation shows is the attribute, which must, therefore, be regarded as die observed dahun. The sensation, on the other hand,consists of aU the attributes wliich might have been observed un-

der all die possible instructions; in other words, it is a phi/siiilofiicalentity, a total excitation which carries

with it these potentialities

for attributive report.

After that—in 191

5—Titclicner altered his .system. The attribute,he said, is iho dcteminatioc factor in observ.ition, that whichcomes out as the result of the parUculav observational ,sel, 'I’he
sensation is die sijslemailti term, the eoiistniet thati,sbuilt up by

logic from many obsemtious. lie did not meiition eh'ineiits al ihut

time, and prcsontly (1924) we lliul him diseus.sing, not sen.sations

and attributes, but the diniciLsions of experience, 'Hk* dbmmlitm
were the old attributes widi new Hame.s (or smne;

ipiality,in-tensity, protensity ( duration ),exteiisity and attensity (elearuess),

He had used the word dimension in tin’s sense hack in lOtiH, ami
now his intent was to describe consciousness as a changing patternin respect of those five dimensions. lie never published fully on
this matter, and it was loft for the present author(19.'3,‘5)

to givethe idea explicit form, a foim of which Titchener would undoubt-

edly have disapproved.

That Kiilpe’s experiment is valid for the conventional altiibutcsof sensations was shown subsequently by Yokoyama ( 1924), Wil-cooks (1925) and Chapman (1932)—at least they found that sub-jects can report more adequately on attributes for which they arc

observe before the exposure than on the other attributes
which they have to judge after die exposure from the immediate
set tomemory of the stimulus-field, ZoU (1934) showed, however, thatseveral attributes can function at once.

He asked his subjects toreport some or different for pairs of colors that might differ in respect of hue or brightness or saturation, finding their reports ac-

STEVENS ON ATTRIBUTES

25

curate aud immediate even when they did not know in advancewhicli of the throe attributive differences to expect.

Recently the problem of attributes has entered a new phase. ( Seepages 377.^ 81 .) Halverson (1824) showed that tonal volume varies
with the intensity of the stimulus as well as with the frequency.

Fig.

1.

IsopnoNtc Conkiobs von Foun Tonal AtiibbuteS!

Stevens (1934)
Tlio standard lone (corresponding to the center of the diagram) has a

Etoquenoy of SOO

c.p.s.

and an intensityof flO db.

The ‘oqnai-loudiiesa’contour shows thelocus of those combinations of frequency and inwhich will give tones equal in loudness to die standard tone. The
contours for pitch, volume and density are similar. Tliese graphic relatensity

tionships are considerably altered for standard tones of different Ireqnenoy

and intensity.

Soft tones, as well as high tones, tend to be small. It ought, therefore, to be possible to equate a loud high tone to a soft low tone inrespect of volume, and Stevens ( 1834) finaRy succeeded in finding
the method by which such equations can be made. Fig. 1 shows

the isophonic contour along which one set of tonal volumes would
be equal; if frequency and intensity decrease together in the rightmanner, volume can stay constant This figure also exhibits isophonic contours for constant pilch (which varies somewhat withintensity as well aswith frequency), constant loudness (wellknown to be a joint function of frequency and intensity) and con-

26

SENSATION AND W-IRCEPTION

slant density, a new attribute which Stevens iliscnvrred (1964)

and which shows a function different from the other three. These
functions indicate that the criterion of independent variability is
too simply stated: it is nut passible to vary one of these four attributes while keeping the other three constant. It is pos.sible, on

the other hand, to keep

one eouslant while the other three arevaried, and the curves of Fig. 1 show just how the stimulus must

be changed if this end is to be accomplished. Stevens, therefore,suggested that, in addition to iiiseparahilittj, an attribute mustsatisfy the criterion of independent constoiicy.

Several other consequences follow from Stevens’ conclusions.

Ever since Galileo correlated pitch with frequency, it has beencustomary to look for one-to-one relations between Iho dimensionsof the sensation and the dunensions of the stimulus—pilch goeswith stimulus-frequency, loudness with slimulns-iiitciisity. Fig. 1

shows dial tliis relation is uot true. All lour attributes arc joint
functions of changes in both the dimensinns of the sliuinliis. It has
also been conventional to seek in the sense-organ exjdanalions of

the atti'ibulos, such ns the dependence of plleli

upon place ofstimulation in the oar, and IoikIik'ss upon amplitude (or later total

amount) of excitation. Tliere is at present no known way of loealitt*ing the physiological coiiditions for allribtilive analysis in the sen.st'organ. The attributes express lire capacity ol llie orgaiiisni to mak('judgments about ceiiain relationships of exeilalimi. They mighteven be learned, as would be the case if low ami loud tones werecalled large because drey usually come from large instruments orother objects. The only reason to believe that they arc not leanicd
isthe dose agreement ofmany persons with respect to tlieirmeasurements, and the ease and immediacy with which they are
judged. All that can be said is that they depend upon properties of
the nervous system, either congenital properties or, conceivably,properties acquired in experience,lire present author has shown (1935) that there is theoreticallyno limit to the number of possible attributes, except tho nature of
the nervous system, which must furnish some limit, although there
is at present noway of saying in advance what it is. Even if attri-butes were learned, there would be, however, a practical limit.

No one could learn to make accurate discriminations in accordance with a large number of superimposed functions in Fig, 1. If

we were, for instance, to start inventing new attributes by making

UNITY OF THE SENSES

27

up new arbitrary functions for subjects to learn, tlien we shouldhave to slop very soon, for the limits of judgmental differentiation

would soon be reached,
Unify oj tlie senses. There has always been a question as towhether quality is a primary attribute, whether the other attributes

depend on quality in such a way as to make it sensible to say that

we have an intensity of a quality, the dm'ation of a quality, the extent of a quality, but never the quality of an intensity or the extent
of a duration. There is, of course, sense in speaking of the durationof an extent when size is changing, of the extent of an intensity

within a spatial pattern of intensities. Titchener was indined ulti-

mately (1915) to have aU the attributes coordinate contributors to
the sensory whole. Such a view seems to imply that each attributeexists in its

own right, and that for tire intensity of a tone an idenWundt in 1858

tical intensity can be found associated with a color.

showed that a tactual extent can be equaled to a visual extent.
Miinsterberg in 189Q tried equating the intensity of a sound to theintensity of a woiglit, but concluded that the judgment is made interras of kinesthetic slraius which function vicariously for the in-tensities of both prcssuio

and .sound,

Nevertheless the problem has persisted, It was one of the argu-

ments Cor ioucs’ (and smcllsT) having volume, since extensity applies to visual, tactualand perhaps gustatory sensations. Von

Hornbostel in 1931, having regard to the fact that colors havebrightness and that brightness is one of the vigorous candidates
for attributohood with tones (pp. 376-378), undertook to equate

the brightness of a giay to the brightness of an odor, and then thebrightness of a tone to the same olfactory brightaess. He founddiat things equal to thesame thing equal each other, that thebrightnesses of the gray and tone appear equal when both equal

the brightness of the odor, but Cohen (1934) came to the conclusion that von Hornbostel’s triangular equivalence was an artifact of

method. Thus the question remains open. Von Hornbostel (1925)
coined the phrase unity of the senses to express the conception thatall senses are alike in respect of their attributive dimensions, andindeed the physiological similarities of the ways in which the different fields of the sense-organs are projected upon the brain creates an initial presumption that diey might resemble one anotherin respect of their discriminable aspects.

SENSATION AND FlSllCKPTtON

28

Nativism and Empiricism
The two ‘dreaiy’ topics in the lustovy oC expciimeutiil psychology, so convention has it, are nativism and empiricism, on the one

hand, and psychophysics, on the other. CerUiuly the endles.s pagesof futile tallc— one of psychology’s least happy inherilanees fiom
itsparent philosophy—are dull, but psychophysics, which got

somewhere, is not dreaiy, if one ignores the futilities, nor is theinterminable argument about nativism and empiricism tiresome, if

one forgets the talk and studies the events as an example of man’seffort to see himself clearly in the dark.

Psychophysics’ successes

are considered in the next section, and the problem of nativism andempiricism comes up again in tire chapter on the perception ofvisual space (pp. 233-238 ), where it appears that every empiricist
is alsosomewhat of a nalivist, and conversely. Here we need only

a prospectus of the debate about the origin ol ibe knowledge ol
space.
Tlie background is clear. Deseiule.s( i(i37)

held a lieliel in in-

nale Ideas, Leibnitz (1714) in pree.slahlished liarmony,

Kaiil(1781) in a priori intuitions, of which .‘ipaee was oiii', 'Hie I'liiglMi
empirioists, from Itobbcs(1651) and Uieke ( 1B!)1)) on, wt>re on

the side of the tabula rastu mind is not ‘given’ bnl i.s genenUed inexperience. Berkeley (1709) was the (Irst empivieisl lo argue llwt

the perception of extension is origuudly founded on the iiereepliouof the body’s own movement, which becomes associated iu experi-ence with tactual and visual impressions. Tliomus Brown ( 1820)
insisted further on this same point, reducing visual .space to movi*-ment, and thus perceived extension lo perceived succession, since

movement is serial. Tlie notion dial spatial localization is given iu
perception by movement or kinesflicsis, assooialively compoundedwith the sensation localized, was already in assooialionistic psychology beMe Lotze reenforced it.
After Kant and Thomas Brown there arc to be traced four linesof development, two on each side of this dichotomy.
all but the famous names. First there is

Miiller, Bering,

We may omit

nativism; Kant, Johannes

Stumpf. Closely allied willi nativism

tliere isphenomenology: Goethe, Bering, Stumpf, Gestalt psychology. On
the other side, empiricism: the assooiationists including Brown,

Lotze, Helmholtz, Wundt. A synthesis of nativism and empiricism

was offered by Kiilpe and Titchener. Allied to empiricism is theNATIViSM
line whicli, from the perspective of the present, looks like opera-

tional behaolorim, the views of those men who regarded actual

movement, not the sensations of movement, as die key to the perception of space.

Natioism. Johannes Muller is regarded as having given formal
status to the nalivistio theoiy in 1826. His theory of tlie specificenergies of nerves (pp, 68-72), a theory of sensory qualify, as-sumed that the mind, being in the brain, can have direct contact
only with the nerves and thus is directly aware only of fhe states of
the nerves, never of the external bodies themselves. It learns about

the states of external bodies, because fhe bodies affect the nerves

and the mind perceives the slates of the nerves. Midler’s theory ofvisual space perception was related both to this theory of specificenergies and to Kant’s a priori intuitions. Thus the mind direcdy

perceives tlio spatial relations of the retinal image, because these
relations are preserved in the arrangement of die optic nerve fibers

with which the mind has a direct apprehending contact. That theretinalimage is upside down caused Muller no trouble, foi' thespatial relations within an inverted image arc, of course, identicalwidi diose of the erect image.
Iloriiig,

writing in 1861-1884 after Lotze had invented local

signs, attached the signs lo every retinal point. With the facts ofstereoscopic vision in mind, he sought to account for tridimensional space in terms of the retina alone—without tire empiricist’s

appeal to movement of the eyes and body, Thus he posited three
local signs for every point— one for vertical position, another forhorizontal position, and a third for depth and distance. He heldthat this third sign might be positive or negative, contributing thus

algebraically to the binocular perception of depth. Such a systemof primitive spatial labels was fully enough to classify Hering as anativist, but. hke all the nativists, he was also somewhat of an empiricist, for he had agreat deal to say as to how the concept ofsolid space gets built up in experience out of these primary localizations.

Stumpf, a student of Lotze's and Bientano’s, carried this tradition further, writing his Usher den psychologischen Ursprung der

Raumoorslcllmg in 1873 and getting called, on account of it, tosucceed Brentano in the chair of philosophy at Wurzburg. Stumpf

had once met E. II. Weber, who had, with his compasses, demonstrated the sensory circles on Stumpf’s

ow« skin. Weber’s circles).

SENSATION ANO PElICia'TTON

Sa(pp. 476 f. ) suggested local signs, first to Ltil/c> and now to Htumpf\i^ether a belief in local signs niatk oiu’, in tboso days, a uativist
or an empiricist depended entirely upon whcllier one thought thesigns were in themselves spatial, consciously labeled as to theirloci, or whether one thought die signs

qualitative

were intensive (Lotze) or(Wundt), coining only after experience

to indicate

Spatial relations, Stumpf thought, of course, that the spatiality isnative in the signs. He is chiefly important in this tradition, however, because he forms a link between tlie older nativism and theGestalt psychologists, who are also, in a sense, nativists.

Empvtioism. Johannes Muller’s nativism might never have be-come so important, had not Lotze in 1852 been so persuasive about
the empiricistic view. Muller thought against a Kantian back-ground. Lotze had die assooiationists, Uieiv conception of complex
ideas’ being intimate fusions ofmany sensmy ctmipoiunils andalso their notion that all space pcrct’])lion dcpc'iids upon nuisciilar

sensations. Webei'’s sensory circlw (tinii.sla’d him with evidence ollocal signs. He did not, however, believe that spatiality is given in

the local signs thcrasolvos. lie argued rather that
intensltive, that the idea olqualities as

ihi' .signsarespace Is btilU, nut out of nm.scu1ur

Brown had said, but out of inlensilies, 'I’Ue lueUml

signs exist because any stimulus fct'ls dilfereiitly on dill’i'i'ent partsof the body, depending upon whothcr it is near a tendon or fatly
tissue or some other special conConiiation which makes the intensitive pattern of sdmulation specific for the .spot touched.

(Muchlater, after Lotze was dead, Kiilpe said that this Ihcuty would re-quire the maximal confusion of localization to occur between symmetrically opposite points on die body, because such places are themost similar in conformation, even though also die most remote.

For vision Lotze appealed to the tendency of the eyes to move so
as to bring to the fovea any stimulated point thatcomes underattention. Every retinal point might thus have associated widi it

an intensity of a particular sensation of movement, Such signs,
both visual and tactual, Lotze drought, gel themselves ordered byexperience: we learn that h is between a and c because with con-tinuous movement the signs are experienced in the order abc.

In that way we form the concept of lines, and from lines comeareas. This was a positive theory, and Lotze asserted that nativism
isno theory at all but rather a petitio princlpii, “the confoundingof the solution of a problem with its data.”—
EMPIRICISM

J31

To Lotzc's llicory Helmholtz added the clarity of his thought
and the cnlhusiasm of his exposition. He did not accept the intensitive pattern as detenniuing lire local specificity, but thought

rather drat difference of nei’ve-liber would itself be enough to

explain perceived difference of locus. He left open tire questionof conscious local signs. Thus he added little to the theory except—and it was no mean addition—^the force of his insistent exposi-tion as he defended empiricism again and again from 1855 to 1894.
It was he, for instance,

who argued so effectively that the geo-

metrical axioms are not innate, are not a priori intuitions, butlearned relationships. He explained how people who lived only

on a spherical surface would learn that all parallel lines intersect
in two points, how people on an egg-shaped surface would eventually realize that circles of the same radius may have different cir-

cumferences, how men confined to a piano would never be able
to get out of a square, and how beings who had four dimensions attheir disposal could step out of a sphere as easily as we can stepout of a circle. Ilis views became so popular that Zdllner, the astronomer', perhaps mixing sense with nonsense, suggested tliat

astronomical .space must be curved and finite, else all matter would

long ago have boon volatizod, and that Slade, the medium, probably was able to got objects out of a closed box by using the fourth
dimensioni

The tliorough Wundt was less deft but equally insistent—from1859 to 1911. Every tactual and visual point, he said, has a qualita-—not a spatial nor an intensitive one but a bcal

tive local sign

Out of these qualities spatial continua get themselves
built up in experience by movement Eye-movements establish thevisual continuities, bodily movements the tactual. Movement,
moreover and here Wundt was reverting to the assodationists
continues to give the meaning of extension. The optical illusions
deceive because they induce eye-movements that do not accord
with the dimensions of the part judged, as when the eye moves too
quality.

—

far with the obtuse angles of the Miiller-Lyer illusion, or too little

with the aaito angles.
Kiilpe and Titdrcner count as empiricists, but they were reallyachieving a synlliesis of the empiiidstic and nativistio views. Kiilpe(1893) was accepting nativlsm when he added extension to theand vision. You cannot, he tiiou^t, getlist of attributes for touch

space out of the non-spalial. Man would eevei have conceived

SENSATION AND PEUCiaTION

32.

of space had it not been given him in the First place— but then even

Lotee had held that the general conception oi spac(‘ must be inherent in the natae of mind. Kulpe made spatiality inherent in thenature of sensation. The local signs, he thought, are uneonscious orconscious, depending upon what you mean by the term. The local
differentiae among sensations are unconscious, for they are merely

the physiological potentialities for different localizations, merely
the neural connections of different points on the skin or retina withdifferent points in the brain.

identical with a touch

A touch on the right hand may heon theleft,

as far as the qualitativc-

intensMve-durative-extensitive pattern of die sensation itseli goes;

yet the two points may have different potentialities for conscious
localization, as appears when one stimulation leads to the visualiza-tion of the one hand, and the other stimulation to an image of theother hand.

Titchener ( 1910 ) followed Kfllpo in ;ill ihe.se mailers and added
the context theoiy of perception. There is no inysleiious extra local

qude to the extended sensation itseli, hot a conseimis eonlexi ol
imagery or kineslhosis provldt's llic localization. Most ptsiple know
where they are touched bccuuse ol added visual imagery, tliough
the blind localize by kine.slhosis. Even lociiHzatlon in llie third visual dimension is contextual, Tilchoiicr thought, eousisling of tlie
addition to the visual core of a kinisilhetie emitext derived I'lom

accommodation or oonvorgonco.
Such ate the main points between which may be plotted these

two historical lines. The argument is clear, yet what, we may ask,
has become of these linos now? Why did naUvism and empiricism

seem to disappear in the twentieth century? The answer to thisquestion is that they did not exactly disappear, but that each ho-oame something else, Nativism turned into phenomenology, andempiricism into habits of thought of the bebaviorists and operntionists.

Let us see.

Phenomenology. If the givens are the important things, tiion all
one does is to describe; he does not tlieorize. In spite of Lotze’s

remark about theories being necessarily positive, one is not begging the question if he finds it better merely to describe events andto create no theories about them. Thus the phenomenologisls, insticking to the immediately given, tend to( 1810; see pp.

be nativists. Goethe

112-116 ) makes a good starting point for phenome-

nology, with his inniraerablc observations about colors

and liis

MODERN THEORIES OF SPACE,33

implausible classifications which he called (heory. Purkinje (18191825), lliat other excellent observer, perhaps also belongs at thestart of this line. At any rate, with two such examples before him,

Hering could well become the later exponent of what we now callphenomenology. His texts on bri^tness and color are replete withgood observations. His theories, which of course he had, are lessfrequent and less important Of elaborate experiments he had few,

hut of expeiiTtienta ciucis he had many. The experimentum crucis,
the litde critical demonstration which makes a point, is a special
tool of phenometrology, of Hering as it is now of the Gestalt psychologist.

Stumpf at Berlin was also a phenomenologist, both hy

systematic convretion and, in music, by observational habit It was
at Berlin that Gestalt

psychology began, with a small debt toStumpf and a larger debt to liering.
Tints it would seem that the Gestalt psychologists have a goodchance of being the modern nativists. Are they? Well, they ask you
to look and see, prirrtmg a little diagram upon the page—an ex-

perimenhim ci'ucis-~lo make the point They do not analyse thephi-phenorneiton of seen movement into attributes; they merely ask

you to see it. They do rrot tell you what organization is; they ask
you to examine a diugrara and to see how some parts of it stand together to constitute a whole. It was they who showed that a perceived lino is trot a row of perceived poirrls, or a square four lines

when it can just as well bo given by four points. A line, for them, isa line, a square a square, an organization an organization, and phi
is phi, Tire

givens are not to be explained. That is nativism, and, as

Lotze imph'ed, it is a faith and not a theory.

Behaoiord opemtionim. If the Gestalt psychologists are themoder-n nativists, then the behaviorists, operaUonists and positivists

must be die modern empiricists. Their sort of thinking is very old,but it does not lie in a self-conscious school. The men who said thatthe invei-ted image on the retina is seen light-side-up, because animage on the bottom of the retina leads one to orient his body
toward the top of the perceived world (pp. 237 f,), were thinking behavioristically and operationally. So were the ‘capacity psychologists,’ the earlymental testers and the functionalists, whothou^t that you can tell what a man knows by what he does. So
too the animal psychobgists, who thought that you can tell what
any organism knows by what it does. All these men are the modern
empiricists simply because so much of behavior is learned. Not all

34 .

SENSATION AND PEECF.PTION

of it, but most of it. If sensation 4s discrimination and if iho consciousness oi space is tlie capacity to behave adei|uale])’ in space,then experience must play an important role in space perception.

So it would seem tliat empiricism dLsappeared because it was absorbed by behaviorism and its later sophisticated substitutes, just
as nativism disappeared because Gestalt psycliology kept

itbyswallowing it,

Psychophysics
Fechner created psychophysics, making it secure by the publication of his Ehmente der Psyctiophijsik in 1860. We must ask now
how this achievement of his was possible. What was tho intellectual
situation in the 1850’s tliat made the moasuremont of sensation an

appropriate and reasonable undertaking? Creative imagination ismore than spontaneous generation; always is it fathered by tho
Zeitgeist.

In the first place, then, tlicro was in the nineteenth century the.
general awakening of scionco, tho oxporimeutal investigation of
everything, tho invention and improvwneul of instruments of observation, like the lolosoope and the microscope, In short all thatmarks tliat century as tho beginning of the age of sei(‘nee. Witl>
science comes die refinement of oliservution and, of course, meas-

urement. Astronomy and phy.sics won! full of niea.sur('nH'nts, andthe new experimental physiology—not .so much older than exp('ri-mental psychology, for Johamies Mliller was called its father-had been measuring whatever it could find about the organism tomeasure. Sensation was simply one thing to be moasurod, since theBell-Magendie law showed it to be half of the function of theperipheral nervous system.

To some extent it is true that sensation already had been measand sensations had beenshown to be equal, or just noticeably different, a demonstration that

ured. Its stimuli had been measured,is the beginning of measurement. Fraunliofer in 1815

p, 177) had(
shown what must be the intensities of different spectral liglits if

the colors are to be equally bright Bouguer in 1760 (pp. 136 f.

)

had

anticipated Weber by showing what must be the relative illumi-

nations of a shadow and its background if the shadow is to bo justnoticeably different from its background. There were dozens ofsuch observations, and then E. H. Weber in 1834 by numerous
experiments establislmd—or atleast

seemed to ostalrlish—whatFECHNEH’S PSYCHOPHYSICS,35

Fechner later christened Weber’s law ( p. 495) Weber s point was,.

of course, that two sensations are just noticeably difierent as longas a given constant ratio obtains between the intensities of theirstimuli,

So sure was he of this fact tliat he spoke of the barely

discriminable difierences in terms of ratios, without always mentioning the absolute intensities: the skin, he asserted, can appreciate a difference of %o, be that 14% and 15 half-ounces or ounces

or drams, or 29 and 30 half-ounces or ounces or drams. Fechner did

not start from scratch.
Against experimental measurement were dualism and Herbert.
Cartesian dualism was against the measurement of sensation be-cause it held that mind is incorporeal and does not occupy space.

Even psychophysical parallelism, which was coming more andmore to represent the thinking of experimental physiologists about
mind, seemed to leave sensation on an unmeasurable side of adicholomy. Hcrbart, on the other hand, favored the measurementof ideas

and tho application of mathematics to psychology, al-though ho denied the possibility of psychological experimentation,
life lfe(/c/i(j((igl« ah Whsetischaft in 1824-1825 is filled with argu-

mculs, malhomalically explicated, as to how ideas of different
strengths iuteracl with one another. Ho ‘measured’ but did not ex-

periment, Perhaps that was Wisscnscliafl, but it was not science.

Thus llerbart, while hindering Fechner, also helped him. He
helped him because ho made the notion of measuring and malhemalizing mind rospootable, even though he believed withal thatthe method of measurement should be metaphysical. He also supplied for Fechner the concept of the limen, which he himself had

from Leibnitz. A weak idea, in competition with stronger ideas,
does not, Heibart thought, enter consciousness, is not apperceived,
but, being inhibited, remains in a state of tendency. This conception of a limeu for consciousness is basic to psychophysics, eventhough Feolmer’s consequent belief in the existence of “negative
sensations” below the limen remained too vague to become scientifically useful.

The rest of psychophysics Fechner got from himself. A man withthe broad intellectual interests of the German GeMirter, he wastrained as a physicist, resigning his chair at Leipzig in 1839 on

account of a nervous breakdown. During the long period of illness

which followed, his interest turned to philosophy and, more specifically, toward a campaign against the current materialism.

TheSENSATION AND fEUCliPTlON

36 I

last thirty-five years of his life

(1842-1887) he devoted, it is not

too much to say, to promoting a philosophy of paupsyeliisni, theview that mind and matter are one and thus that mind is all. Ilis
psychophysics was but an incident in this eanipaigii, for Feehner
regarded die Fwidamentalfonnel of “Weber's Law,” wliieh expresses, at least in respect of sensory intensity, the relation ol matter (stimulus) to mind (sensation), as the paradigm for the trans-

lation of the material into the spiritual. Even here, however, we seethat Fechner’s soul was not entirely his

own but subject to theZeitgeist. His philosophy the world for the most part ignored; his

psydiophysics it took very seriously indeed. Fiist llicre appearedexperiments based on the conceptions of the Fsijchophysik of 1860;
then there was criticism of them, and in the criticisms came also
the recognition of their importance.

The Psijchoplnjslk made the following important contributions
to experimental psycliology.

(a) It c'stablishcd and worked nut details of wliiil have .sincecome to bo the tlwoc ftiudiuncutal iwychophysical umtUods of the
making of basic inoasurcmonU and the coinjmlalion of the jtsyohophy.sioal constants: the tnethod of liinils, the inctliod of rigid

and wrong cases, Ihe method of average error,(b) It showed how Ihveo of the five fnodamental inea.sures are

obtained and what their meanings are: the ab.solute limen. thedifferential limen,

and sensory equivalence. ( [t did not con.sider

the problem of the delenniuatiou of sense-distances or of .senseratios.)(o)From the facts of the differential limen, it established themeaning of what we now call Weber’s law, and from Weber’s law
itderived Fechner’s law (which Fcchnor called “Weber’s law”).

Weber’s law gives the relation of the just noticeable difference(j.n.d.) to the stimulus; a j.n,d. is given by a constant dotonninableratio of two stimuli.

Feehner, assuming further that all j.n.d, arc

equal and tliat the j.n.d. may therefore be used as the unit of asensory scale, integrated We'ber’s law to get Fechnet’s law; tliat is
to say, be counted up j.n,d. from the absolute limen in order toobtain the points on a scale of sensation ( S ) that is correlated withthe scale of the stimulus intensity (1). Fechnei's law is, in these=k log I. Feehner began by asserting that you cannot
measure sensation directly, but only sensitivity, (The measure ofterms, Ssensitivity is simply th^ reciprocal of the limen,)

By the assumption

PSYCHOPHYSICAL METHODS

37

of equality among j.n.d. and by Integration, be thought, however,lliat hehad succeeded in measuring sensation indirectly, and thus

in achieving his goal of stating the relationship of mind to body.

In addition to all these matters the Psychophysik contains (d) agreat many results of actual measurements and (e)many pages

on the problems of "inner psychophysics,” a phrase which Fechnerused to designate the relation of sensation to neural excitation, in
contradistinction to “outer psychophysics,” which deals only withthe relation of sensation to stimulus.

Before we take up the more important lines of discovery to which

Fechners work led, we must mention the later outstanding books.''
Dclboeuf, who established the concept of sense-distance, published

two important monographs, one in 1873 and another in 1883. Inthem he gave status to the method of equal sense-distances. G. E.
Muller,who criticized Fechner and in particular modified andcoirecled the method ol right and wrong eases, published one bookill1878 and another in 1903. Meanwhile Wundt kept discussing

the mclhods and their results in the successive editions of his

Physlologischo I’sycliahgle, and his students, especially Merkel,

wove pttblishiug in the Philosophlschc Slmlien, Titchener’s incomparablo p,syehophysicul inauimls came nut in 190S, with 281 pages
out ol the 587 of the second volume devoted to the history ofpsychophysics, lire book was just late enough to take account of
Muller’.s contribution in 1903, but too early for Urban’s in 1908.

Urban corrected the tables for the method of right and wrong
cases and contributed the concept ot the psychometric function.
Later, psychophysics got itself tied up witli the statistical methodsof mental measurement, as Guilford’s book ( 1936 ) shows.

Now for the scientific developments.
Methods, No one of the three fundamental methods was quite
original with Fochner, Fechner established them; he did not invent

them. The history of thought is nearly always continuous. Every
important ‘new’ idea has its less important, often obscure, anticipations.

(1 )
in

The method of limits (minimal changes) is the procedure

which the stimulus is changed by successive, discrete, serial

steps until aci-itical

point is reached, a point where the subjectchanges his judgment. One starts with a supraliminal intensity anddiminishes it until the subject reports no sensation; or one starts

with a .Subliminal intensity and increases it itnlil the subject reports

SENSATION AND PERCEPTION

38

sensation; or better, one does both und averages llie results. Thnt
gives an absolute limen. A differential limen is got by taking two
stimuli, a standard

and a comparison, and by varying the eoin-

pai'ison stimulus until a report of diffei'enci’ ehunge.s to no dlffcr-

ence, or conversely, or both. That is the most natural way to locatea critical point, to approach it gradually iiom one side and thenfrom the other. Consequently, it is no wonder that various iirvcsti-—Sau-

gators should already have used diis procedure incidentallyveur in 1700, Bouguer in 1760, Delezenne in 1827. ( Sec pp. 136 f.,
339 f. } Titehener was inclined to give Delezenne tiro credit asoriginator.

TOen this method is used to determine the differential limen it
becomes the method of just noticeable differences {least perceptible differences). The j.n.d. is the average oi the mean first notice-able difference when the difference incrcuses and the moan first

not noticeable difference when the differonce decreases. Although
there is a good deal of variability about litis average, tlu' j,n.(l. citirre
to be regarded as a fixed unit, largely becaust' I'celuier startl'd llie

custom of counting up j.rr.d. in order Ui place lire niciwui'i' of asensation on a sensory scab. Later, iw we bave seen (p. 10), psychologists like Kiilpo and Tllohcucr counted ].n,d, for Ihe purpi).si'of determining the tolal tale of smuinry eleuients, Tlii' eomiler-

argirmentol Lolzc and SUunpf (p. 10) that seiisalion car: jii.st a.swell bo regarded as a continuous function of slimrtlus, lhal its mag-nitude is not made up of discrete quanta, wrrs couviueing but
neverthelessnever oonsislerrtly accepted. Only recently have

Stevens, Morgan and Volkmann (1941), with a mclhod of rightand wrong oases and but little variability about the average, presented evidence that the sensory scale may, after all, be quanlal

and not continuous. Indeed, one rather expects that finer analysis—^molecules, atoms, elec-

will ultimately come up against quantatrons in the case of matter, and discrete nerve-fibers or the

all-or-none nerve-impulses in the case of sensation.
(2) the method of right and wrong cases {constant stimuli, constant method)

presents the stimuli or stimulus-differences in quasi-

random order, and, treating each stimulus ( or stimulus-difference)as a constant, determines tire relative frequency

with which every

category of judgment has been used for each stimulus
difference). The constancy appears in the(or stimulus-

treatment of the data,

not in the experimental presentation. One gets in thisway whal

PSYCHOPHYSICAL METHODS

39

Fio. 2. PsYcnoMiTnio Functions and the Method of Constant Stimuli

For comiiorison of lifted weights (one of Urban’s subjects). The plotted
points .show the ohsorved relative frequencies oftito judgments less (openand gfcoiec (solid circles) at five constant values of the compari-circlc.s)

stimulus. The oLserved psychometric fimclious could be shown os lines
oonnooting tlicso points. Tho psycltomclrie functions of the figure are, how-sutiever, ihu nociniil ogives fitted to tho points by the moOiod oi least squares.
Tho function for tho Jndginonl eqim need not liave boon drawn, since itshows only tho residual frequencies (for tho Judgments that are nellber
greater nor Im). S =- lOO grra. is the standard stimulus, benoo objective
oqiuility. Li,
lower Uininal point
81.B8 grin, La
upper llminal point•
98.9, gmi. Ui
Lj,interval of uncertainly
7.27 grm. Tbe ailler-==
ential limens could be tnlien as (S — La) and (La — S), but ibere

™

—

=

=

the usual oonslnnl error(

time-error) with

is

here

La lying below S, maldng theupper liraen negative. It is, therefore, better to use the interval of uncertainty(

or hall of it— 3.63 grm.) as the measure of differential sensitivity.

The point of subjootive equality, E, is usually token as the stunulus ditforcnco for which the judgments less and greater are equally frequent (in-=tbe two psychometric functions
95.24 grm.). Sometimes,
however, E is taken ns tlie miifeoinl between Li and La (95.31 grm.), or
tersection of

as

the

maidmum of the cqunr function (95.52

gnn. ). 'Ihese points are

identical when the functions are symmelrical.

For an absolute Ilmen Uie equal category disappears and the functions
and greater, being then necessarily symmetrical, intersect at S0%,

for lessthus fixing there the position of die absolute Ilmen.

The steepness of the normal ogives is expressed by the measure of precision,h (.481 for less, .444 tor greater). Sensitivity varies with h, whldi

has in a normal probability function a constant ration to the probable

Urban in 1908 called a psychometric function, a curve of percentages plotted against stiinulus-valiies. An absolute limen is the point
at which sensation is reported as frequently as not, the fift)t-per-SENSATION AND I'l-UlCEmON

40cent point on the function. For the tliilorcnlinl limoii tlirvp nrc
usually three functions, ono for each of the tluvi' eatejtorie.s of

judgment, greater, equal and less. Ordinarily two limeiis result, an

upper and a lower, Tlie upper limeu lie.s at the lilty-per-ei'nt point
where greater is reported as oiten as not. The lower limeu lies

where less is reported as often as not. Urban called the distance
between those two liminal points tire inlmal of tinfertaliiUj,
which can be regarded as twice the limen, See Fig. 2 and its legend.

Some psychologists have argued tliat the equal category is essentially a doubtful category and should be e.vcluded, either by divid-

ing the equal reports between the greaters and the lews, or by
instructing the subject to avoid saying equal and, when uncertain
as between thetwo remaining categtiries, to guess. Peirce andJaslrow (1884) and Fullci-ton and Caltell (1802) reeotnmended
this

procedure, Bolh

Wanier Brown (1910) andFeriiherger(1914) found that the equal judgments are rediiw'd it\ Iteiiuency
or even eliminated if the subjecls assume the attitude' ol trviug inperceive a differeiicc. Of course, it the equal ealegurv is elimiimlt'd,there remain only two i).sycluimotric fmielinns, .syuimeliieal witheach olhev and oro.ssiiig ul the flfly-per eenl point, 1 l(’uet‘ lliere isno limoD. The iiwosligalors who use this nii'llmd hiive. ihevelore,
taken the probable error ( the 7l)-pep-eenl point ) as imliealiiig thelimeu. This is the point that is lialC-wny belween 'elmiiei'’

(fStl

per

cent) and ‘certainty’ (0 or lOO jier cent). Kimic olliei's have meu.s-

ured sensitivity by h, a mathematical conslaiit lluil r'uries with thesteepness of the psychometric luuclion.

The method of right and wrong cases, us it was called in Iho
beginning, was first used by Vicrordl and his pupil, Ilegchnaicr, in1852. Feclmer developed it, passing a nonnal ogive(

the integral

form of the normal probability curve) through only two stimulusvalues, and computing the limen from this hmetiou, Milllcr in 1879

used more stimulus-values and fitted the iionnal ogive to them byfire

method of least squares. lie also figured out the dillerent

weights to use for dillerent frequencies in accordance with probability theory. Urban, as

we have remarked, shifted the emphasis in

the use of this method from the iimens to the form of lire function,

which he named the ‘psychometric function. He also corrected
Muller’s weights for ihe different frequencies, prepared tables toreduce the labor of the computations, and raised the question as towhether the normal ogive is the right funation to use. This ques-PSYCHOPHYSICAL MEASUEES
tiou, after

41

some trials with other functions, he answered with aYes, but it is not yet clear how snch a broad generalization cansafelybe made. The validity of fee o piorl use of the normal

probability function, both in statistics and in psychophysics, seems,
at least to the present author, still to be an open question.

(3) The method of average error (production method, Herstelhmgmethode) provides fee subject with a standard stimulus andwife the means of varying a comparison stimulus. He must change
fee comparison stimulus back and forth, until it is subjectively

equal to the standard stimulus. This is a production method because fee subject himself produces fee significant value in thestimulus. It is a method of average error, because in the treatmentof results the average constant error and the average variable error

are computed, The method was popular in America with the prebehaviotisls because it depends upon the behavior of the subject
aird not upott his introspective judgment. It measrrred his capacity
to be ‘right,’ not the frcqrrcncic's of his sensory experiences. Fromthe point of view of the subject’s rclalioir to the external world ol
stiinulrrs,

moreover, every jrrdgment of equal is ‘wrong,’ bocansono two stirnrrU ever rrre exactly orjtral. He might as well giress when
he thinks tiro stirnrrU are equal, and fecn ho can have the degree ol
his otTor dotormirrod. Tlirrs

the subject aims at no-differonce inorder to have his inevitable differctrcc moasm'ed. It is also true that
fee subject finds it castor to adjurt a stimulus by continuous trial

and error than to jttdgo fixed stimuli. It was for this reason that
Stovens (1934; see p. 379) was able wife this method to get consistent results on tonal volumes when others had failed wife themethod of constant stimuli.
Tiro method of average error was

firstused by Fechner andVolkmann ( 18S0) in an experiment which Fechner later reported
in fee Pstjchophyslh It may be becoming popular again with fee
positivistic reaction

away from fee uncertainties of ‘verbal be-

havior.’Measurement. Just what values were fee psychophysical methods used to measure? There are at least five basic items, any one ofwhich could be obtained by any one of fee duee methods.
is the critical point marking fee end of( 1) The absolute limen
a sensory scale—the threshold for intensity, the limits of audible

frequency ior .sound, the limits of visible spectral wave-length forlight. Fechner made fee absolute hmen basic to his system. In fact,SENSATION AND PERCEPTION

42
S= log Us true onfehis

own itssumption only if the absolute in-tensity, I, is measured with the absolute linien as the unit.

(2)

The differential limoii is siippased to be a just noticeable

difference, but we have seen tlmt it is necessarily a statistical quantity,that no stimulus-difference is always just nolieeable, that aliminal difference is noticed only as often as it is not. Fechuer’s useof the j.n.d. as a constant unit of sensory magnitude has, however,
persisted up the present. The fact is that counting j.n.d. may or

may not give us a scale. If Fechner’s critics are right, if the j.n.d.
as measured in relation to some other ‘truer’ scale are unequal, thenwe have only an ordinal scale of sensation, a scale in which theorder of sensations is determined but not the relative distances

between them. On the other hand, if we make all j.n.d. equal Inj
definition (a j.n.d. equals another j.n.d. because both are j.n.d.),then counting differential limens does give us a ratio scale, with anabsolute zero and relative distances significant in terms ol the unitof the count.

(3) Equivalents can be determined as between a point on one
scale and a point on another. For instanc(', Weber in 13.34 deter-

mined lire fact that a pressure of four ounces on the forehead isapproximately equal to aprc.ssuro of one ouiiee on the lijM. Wruidt
in 1858 detei’inined

lire

equivalents of tactual to visual

e.vteut.

Feohner called tho determination the mclhoci of ('(/iiloalnils, comparing tactual distance on one part of the .skiii with tactual distanceon another. Recently the method has been applied to the problemof the unity of the senses, the detcrraiuatioii of tho brighlne.ss in thescale of grays and in the tonal scale that is equivalent to the bright-

ness of a standard odor (p. 27).
(4) Sense-distance is measured when equivalence of two supraliminal stimulus-differences in the same sensory series
lished. This determination was called byisestah-

Wundt tlic method ofmean gradations, by Miiller the method of supralimind differences,by Titchener the method of equal sense-distances. The motliod was
first usedby Plateau in the 1850’s, altliough he did not publish his

results untfl 1872.

He provided artists with a black and a white

piece of paper and had each of them paint a gray which seemed tolie half-way between the black and the white. ( They agreed pretty

well.) Then Delhoeuf, at Plateau’s suggestion, took up the problem

in 1865 and finally published his results in 1873 in his Etitde psy-ohophysique, He used the term contraste sensible (sensible differ-

PSYCHOPHYSICAL MEASURES

43ence) for the sense-distance, whereas Muller spoke of the Kohdr-

enzgmd (degree of approximation)of the diffeiences. It was

Titchener who coined tire term sense-distance and argued, against
the objection that sensations do not have measurable magnitude,that tliey can be measured because they can be placed on a scaleof sense-distances.

Ever since Plateau it had been customary, because easier, to use
bisection to establish this scale. One takes the series of stimuli ohc

and varies the serial position of b until ab=

be. Then one bisects

ab and keeps on until the scale is as finely divided as may bedesired. Titchener held that the resultant scale represents truemeasurement, and was right to the extent that physical measure-ment reduces ultimately to judgment of equality. Sucli a scale,
however, having no absolute zero point, is what has been called aninterval scale, which is not as potent an instrument of measurement
as a ratio-scale, like the physical scales of weight or length.

There is a large literature on the use ol this metliod, but it was
not so large in the oiu'ly days as to answer conclusively lire questionof whetlior Fochner’s law holds for supialiminal differences. Haditboon found that the law applies to both j.n.d. and suprahminal

disbmeos, then it would have boon possible to argue that all j.n.d.
arc truly equal sonso-disUinoes, and Fochnei'’s assumption of equality would have been supported. Only recently have

we been com-

ing to a solution of this eighty-year-old problem. The establish-

ment of subjective ratio scales for pitch and loudness indicates thatj.n.d. for pitch are equal, j.n,d. for loudness not.

(S) It is also possible to determine sense-ratios. Merkel (1888-

1894) tried having the subject make one intensity just twice as
great as another.

He called the procedure the method of the

doubled stimulus, although it was the sensation, not the stimulus,that was doubled. Nothing much was done with this method, however, until

it

was applied to tonal loudness in the 1930’s. Then

Richardson and Ross ( 1930) had subjects estimate the loudness of
tones on an absolute subjective scale, assigning to a heard loudness

a number representing the ratio of the loudness to an imagined
standard loudness, and plotting these ratios against the relative
intensity of the stimulus, Laird, Taylor and Wine ( 1932) had thesubjects adjust a comparison tone to make it halt as loud, and also

twice as loud, as tire standard. Ham and Parkinson (1932) asked
the subjects to select from several comparison tones the one that

SENSATION AND PEllCEFITON

44

they judged to be one-hall, one-third and oiie-lillli, and also hviee,thriceand five times, as loud as the slaudaul tiine. tloiger andFirestone (1933) used the method of adjuslment to establish nineratios of paired loudnesses,

ranging Iroinl()0;lllnongh I;1to1:100. Churcher, King and Davies (1034) hud the loiuliu-.ss halved

and quartered by the subjects, and also the halves halved. Fromsuch data Fletcher (1933), Churcher (1035) and Hloren.s (193(i)have constructed true ratio scales of loudness, scales with an absolute zero and all the metric power possessedby any physicalscale,

Weber’s Late and Fechno/s Law. Weber’s law is AZ/1
stant,= a con-when AZ is the stimulus increment for the j.n.d. and I thestimulus from which the inoi'ement is measured, Fcchner’s law, got,as

we have seen, from assuming all j.n.d. .subjectively equal andS~k log I, when is the rnagiiitude

integrating Weber’s law, is.S’of seirsation in appropriate units aird / the sliintrlus measured interms of the absolvrte limou as the urril. Tlu' iutmrihrable avgmneirlof the late nineteenth ccirtury, the argitntenl which miuli’ psyr'lio-

physics seem to William Jatrtes so sterile, Wiis cmitercd upontlii'

validity of these two laws. There wtuv two ohjr'ctioiis to l''eehu(‘i'’.skw, 'Tire first, the “qrrantity objeetiuu,” was th.it yrtu e.iuuot
measure sensation anyhow, Thosmrrtd was that tire narMii'einetits
when made do not sitpporl lire kw. Wc nrust deal cavalierly withboth complaints.

The quantUy objection was based upon introspect iott. A grerrt
intensity does not seem to corrtain within itself ittatry small intensities,"Our feeling of pink,” said James, “is surely not a portion of

our feeling of scarlet; not does the light of an electric are seem tocontain that of a tallow-candle within itself.” “This seusatiou of‘gray,’ ” remarked Kirlpe, “is not two or tliree of that otlrer seirsartionof ‘gray.’ ” These sentences ore but samples ol what was debatedin extenso. Greater

magnitude is not greater complexity, theirauthors said. Stimulus-magnitude, however, is also not in immediate observation a matter of complexity,

A kilogram weight is not

one thousand gram weights, except as it can bo shown to be equivalent by the technique of measurement witli a baknoe. Simikrly

magnitude of sensation is only a statement of relation between
sensations obtained in accordance with certain operations of meas-

urement. Those operations were pretty well established by Del-

WEBER’S LAW

45

boeiif, and have been developed one stage further in themodem

ratio scales of sensation.

—althoughThe other complaint was valid if you speak strictly

there is a rough sense in which Weber’s law is true. Tliere is, truly,

a law of diminishing differential limens with increase of the stimulus intensity. It is more nearly correct to say that the differential

limen is proportional to the stimulus than to equate it to any constant stimulus-difference. This gross fact it was that the defendersof Weber’s law could never get out of mind. Presently, however,they came to realize that Weher’s law does not hold at low intensities and often not at high intensities. It then became customary forthem to say that it is true, but only in the middle ranges of intensity.

The question of the degree in which Weber’s law is factually

verified is taken up in the proper places in this text (pp. 136-139,

Fig, 10; pp, 339-346, Fig. 55; p. 443; p. 458; pp, 495-498, Fig, 83).

The final generality is that the function plotted between il/f and I,
which should be a straight line if Weber’s law is true, is really acurve, with values of Al/I decreasing rapidly as the low intensities

increase and often rising a little again with increase of the lilghintensities.

No part of Qio curve is indicated to be truly straight.

Fodmor’s law, being Jupendent upon Weber’s law as well as onsome other assumptions, naturally cannot be any more correct thanWeber’s law.

Notes
A

great

many

touehed upon in

of
tins

tho

matters

chapter havebeen considered in exlanso in E. G.
Boring,

A History of Expeiimenlal

Psychology, 1929, to which appiopriaUi rciorenco

which

cites

is

made below, andmany of the secondary

sources and criticisnis.

Sensation

On Grock empiricism and sensation
as the means of knowledge, see anylarge lilstoty of philosophy, using theindex.

On the early English empiricists,
see Boring, op.

impoitant

cit.,

hooks

168-206. The
are:ThomasHobbes,HumaineLeolaHian,

Essay

1851;

Concerning

Nature,

1650;

John Locke, An
Human Under-

standing, 1680; 4 ed., 1700, wiih theon association of ideas;
George Berkeley, An Essay towards
a New Theory of Vision, 1709; A
Treatise Concerning the Principles of
Human Knowledge, 1710; David
Hume, A Treatise on Human Nature,1739-1740; David Hartley, Ohservations on Man, 1749.
For the French School, see Beni
Descartes, De homine, 1062, orL’honane, 1664;-E. B, de Condillac,
Traiti des sensations, 1754; ), 0.
de La Mettrie, L'homme machine,
chapter1748;

C. Bonnet, Essai analytlqae

SENSATION AND PERCEPTION
mr hs facultds de Idme, 1760. See
also die other citations in Boring, op.
ctt.,trans,, 1895; E. D. Titehoni'i, Outlina

207.

For

the

ThomasSchool,ScottishInquliy

Reid,

into

see

the

Human Mind on the Principles ofCommon Sense, 1764; Esscys on tlie
InteUectml Powers of Man, 1785;
Dugald Stewart, Elements of the
of

1702,

1814,

II,

Human

the

Philosophy
I,

6 od., 1908-1011; 0. Klilpe, Gmiidtiss
der Psychologic, 1893, Eng,

III,

Mitul,

1827; Thomas&own. Lectures on the Phihsophij
of the Human Mind, 1820, esp. Lects.

of Psychology, 1896; I'cxt-Book of
Psychology, 1910.

On modality .and quality, see Boring,

Physlcii!

sciousnm,

Dimeuslmis of Gon150-186, and in

1933,

Die ThatWahinemung, 1878,

p,articulnr II. llclmhulti:.

sttohen in dor

8-13, reprinted in his Vorfrage und
Beden, 1884, II, 223-226.

For die counts of discriminahlc

22-24 on muscular sensation; also thenumerous writings of Sir William

sensations, see KuIpe, op, cit., 1893,

Hamilton.

trans.,On the later English associotionlsts,
see Boring, op.

oif.,

208-236. Tire

109 f., 1251., 131 et passim, Eng.
106, 1211., 127 et jmssim;

Titchener, Outline, op. pit,, 74 f.

On sensation as a continuous func-

Mill,tion of stimulus, see, iu general, E. B,

Phenomena of the
Ilumen Mind, 1829, or the cd. witli
notes by J. S. Mill, 1869; John Stuart

Titchoucr, ExpcriincnitS Psychology,

important

books

are;

James

Analysis of theMill, op.

cif.j

Logic, 1843; Exenilno-

II, 11, 190.5, exlvi-cxllx

and the scoreol refeicneos there cited; and, in piir-K.

ticular,II,

I,»t'/,e,Mctnplmlk,

tion of Sir William Hamilton’s Phi-

1879, .5131, Eng.

losophy, 1865.

212-214; (). Fnuke, in L, llermuun's

On the contribution ol physiology

858 1.; C.

1881),

35-48 (general physiology), 77-94(specific nerve energies), 95-114

ehologla,

sensation).

Thebooks cited in the text are; Albrecht
von Holler, Elementa physinhglaa
corporis humani, 8 vols., 1757-1766,

II,

Umullmch dor Physiologic, III (2),to sensatlonism, see Boring, op. cli,,(early research in1887,

tmn.s.,

I,

Slmnpf,Toiqnij-

1883, 351-453. .SlninpC

did not render flnnl judgnient on tfio
matter,which hasllmos hoeii called

Iherefiiri'

snme-"Slumprs para-

dox."

On

hehiiviorism

ingeneral,

soo

era.

V, 1763; Pritna lineao phjsU
1747 et seq., Eng. trans.,
17W et seq.; Charlos Bell, Idea of a
New Anatomy of the Brain, 1811
(privately printed edition ol only
100 eopiesL reprinted, J. Anot.

Boring, op. cll., 1929, 58(1-1589, 594 f,

atagiae,B. Watson’s invention of hehaviorJ.

Physiol, 3, 1869, 154-lOT; Johannes

chology, 1914; his human psychology,

Zur vergleiohenden Physi-

Psychology from the Standpoint of aMiuler,ism is Psychology as the beUaviorisl
views it, Psychol Bet),, 20, 1913, 158177; his anlm,al psychology, Bcimlor,
an introduction to Comparative Psy-

ohgie des Gesiohtssinnes, 1826, esp.
44^5; Uandbuch der Physiologic
des Mensidien, H, Bk. v, 1838, intro-

ism, logical behaviorism

ductory section, or Eng, bans., 1842.

cahsm, see S, S. Stevens, Psychology

Bmaviorist, 1919.

On operationism, logical posillvand physi-

For the Wnndtian tradition in sen-and the science of science, Psychol.

elementlsm and associa-

BuU., 36, 1939, 221-263, with its an-tionism, see Boring, op, alt., 310-344

notated bibliography of 66 titles. The(Wundt), 381-430 -(G. E. MUUer,
Ebbinghaus, Klilpe, Tltchener andsome others). In particular, see W.
Wundt, GrmdzUge der physiologbohen Psydtologle, 1 cd., 1874, up tobook that influenced psychologists
most is P. W. Bridgman, The I^gioof Modem Physics, 1928. For die
first ways in which the psychologists
were influenced, see Stevens, The op-

satianlsm,

,

NOTES
emtional basis of psychology, Amer,J.

Fsychol, 47, 1935, 323-330| Tlie

operational definiUon of psychologi-

concepts

cal

FsijcJiol.

(includes

Rev.,

42.

Phil.

Sci.,

S.

On form-quality, see Boring, op.
dt.,

433-440, 448-450.

6l7-527jtant

papers are:

1935,

E. C.

1938, 90-103|

An operational analysis of‘demands,’ Erkenntnis, 6 , 1936, 383-

andOperational behaviorism

392;

cit.,

sensalion),

Psychology: the propaedeutic science,

Tohnan,47

345-351, 380 f.,
393-402, 427, 431-451.
see Boring, op.

C.

The imporEhrenfels,v.

Ueher Gestaltqualitalen, V;schr. toiss.
Phil, 14, 1890, 249-292; A. Meinong,
Zur Fsychobgie der Eomplexionen
und Helationem, Z. Psychol, 2, 1891,
245-265, H. Cornelius, Ueher Ver-current trends in psychobgy, Ftoc.

schmelzung

und Analyse,

25th AniUv. Celeb. Univ. So.

Calif.,

rote. Phil.,

16,

1938, 89-103; Boring, Temporal per-1893, 3-75.

Vjschr,1892, 404-446; 17.

ception and operationism, Amer. I.

On the context theory of percep-

Psychol, 48, 1936, 519-622. Against(meaning), see E. B. Titehener,
Lectures on the Experimental Psy-

positivism

inpsychology,

see

K.

tion

Fiinclples of Gestalt Fsachology, 1935, passim and esp. 684 1.;

chology

W. Kdhler, The Flace of Value in achology, 1910, 364-373; and, thus

World of Foots, 1938, passim andesp, vll, Movements gam strength,daiificallon, point and interest by
opposition. Ccstnlt psychology, which
got lls Stan by sticssiug the opposi-

incidentally. Boring, op.

tion against itself, similarly now helps

1912, 165-182. There

Kofflca,

to clarify positivistic

psychology%

opposing it.

An excellent discussion of tlie older
theories of perception ante

1785 isgiven by Tnomas Held, Essays, op.
1785. Essay II, Chap. 5.
For the Scottish School on per-alt.,

ception and sensation, see Reid, In-

dt

of the Thought-Processes,
174-194; Text-Rook of Psy-dt.,

185 f.

428 f,
411 f.,
408,(Titehener). For Titohenor on mean(Berkeley),ing, bee his Desciiption vs. statementof meaning, Amei.

J.

Psychol, 23,

an experimental literature on this theory. T. V.
Moore, The tempoial rebtions of
meaning and imageiy, Psychol Rev.,is22, 1915, 177-225, publishing work

Perception

quiry, op.

1909,

1784, Chap. 0. sects.

from Kiilpo’s laboratory, llien at
Munich, and thus defending imageless thought, showed that, in getting
the meaning of a pbture or a word,
sometimes the image precedes themeaning and sometimes the meaning
the image, a result which Indicatedthat imagery is not essential tomeaning. E. C. Tolman, More con-8;

cit., 1785, Essay
D. Stewart, Ele-I,

1792, 63-97; T.

meaning and Imagery, ibid., 24, 1917,

Brown, Lectures, op. cit., 1820, Lect.
25, esp. 564-571.
On the two Mills, see E. G, Boring,

ment and concluded that there are20, 21; Essays, op.
II,

Chaps. 4, 7.

ments, op.

cit.,

A History of Experimental Psychology,

1929, 208-223, 234 f.,

wherediese matters are more fully considered; or die original sources,
Mill,

Analysis,

op.

cit.,

James

18^,

esp.

Chap. 3; J. S. Mill, Examination, op.
dt., 1865, ero. Chap. 11.

On Wunfi,

see Boring, op.

cit.,

310-344, and references there cited.
On Brentano and act psychology,

cerningthetemporalrebtionsof

114-138, repeated Moore’s experiindividual differences as to whether

meaning or imagery comes first. H, F.
Weld, Meaning and process as distingulsbed
Studiesinby the reaction method.
Psychology(Titehener

Commemorative

Volume),1917,
181-208, publisliing from Titchener’sbboratoty, sliowed that

it

all

de-

ends upon how much meaning andEow much imagery, and on whatkind of mining and what kind of

SENSATION AND PERCEITION

48

imagery, are required. A little mean-

Atlributeu

ing may precede a complete image,In gent'ial on the dnetrine of al-

and a meaning carried in one Icbid

mayof imagery (e.g., kioostlietic)

faibntes,see E.

1),

Aec-

Titeliejier,seem to precede imagery when thetures on the Kh'inmlimj lh|/e)in/(igi/

instructed to report onlyof Fooling and Altnitinn. ltli)8, 1,eel.
Ij E. O, Holing, Phy'iioal Dlmonhlons

subjectis

another kind of imagery

vis-

The remainder of this discus-

ual).

sion

(e.g.,

inis

Moore, Meaning and im-of Conscloumoss, 1933, esp. tihap. 2,
Altogether tme finds in Wundt,

agery, fsijchol. Reo., 24, 1917, 318-

given the light context, the follow-

mem-

ing words that mean attiihyto: Mink-

322j Image and meaning inory and perception, FstjchoJ. Monogr.,mtii,

Eigonschaft [dor Emp/indioigj,

McDonough[Ge/ii/dsjton,

Baliininungutiioko,(who worked under Moore’s direc-

Bestandtheil,

Stlmmungscharaktcr,

27, 1919, No. 2; A. R.

ibid., 27, 1919, No. S; R. H. Wlreeler,

hut not the uncommon
German word Atttibiit. On fooling in

J.

The development of meaning, Amer.
Fsychol, 33, 1922, 223-233. The

witliexperiments have point in respect ofcU.,tion ).

The development of meaning,

Farbung,

Wundt’s system as an attribute andTitchener’s theory only because they
dealt withnew pereeptioas. Titeh-

oner agreed with the school of image-see Titchener,

attributes,

op.

125-133.
On the [loclrine ol nltrihntes, in Us

firstphase, see 0. Kiilpe, Grunthhs

less thought that old perceptions eon

der Psyrhologlr, 1893, 39-3,3 (doe230-23« (fc'ling), Eng.
trine),

have meaning without imagery.
For E. C. Tolmau’s syalemiilto

ler'sviews on the way in which alimulns-

and-response

andaituulioii-and-l)e-

imiis.,

20-32, 225 230;

lenslvii series, 7,ur I’syehnpliy.sik tierGcsiehlsempnndimgwi,
iHOO,

havior account for peremtion, wig-

10,

and moaning, .see llrst his liiitial paper. Nerve process and cogni-

Tllcheiii'r,

nlllontion,

Psychol Rev.,

2.'5,

1918, 423-

K, Miil-(1,

discussion ol' ijniilllalive and lii-

E.

li.

1-82,
foe,

Tiilhol,

esp.

rll.

'/,.

Psi/ohol,
2,5 3(1;

21'.,

Then

sea

also

The ilnclriite of enn-scions elemenis, Phil. Ren., 4, 180,5,

M. W. Galkins, Allrilniles

442; then the six other papers cited

1,5.1-160:

in Boring, op. oil, 594, which showof scnsallou, I'.tychol Reu,, (I, 1809,

views developing; then their cul-506-514; M, i’. Washhnni, Soniu
examples of the use of psychologicalliis

mination in PurpoSoe Bchmior in

Animals and Men, 1932; and finally
the notes of the preceding section
which cite the articles in wlilch he
was becoming an operational he-analysis in system-making, Phil Rev,,

baviorist.

oil.,

11.

1902, 445-402,

For E.

B, Titcheneron attention

as attrihulivo clearness, son his op,

To see why Gestalt psychologists
think tliat phenomena ate given as

1908, 171-200; Teat-Book of
Psychology, 1010, 20,5-281; Beginners Psychology, 1915, 90-103 (viv-meaningful, one has but to read ahnost

idness).

any paper by Wertheimer, Koffka or

tenstty, see

Kbhler since 1920. W. Kohler's(with W, L.
Versuche uber Absiraktion, Ber. I Kongr. exp. Fsychol,
1904, 68-68. C. Run’s critique, built

The

Place of Value in a World of Facts,
1938,

is

founded on this concration.

Seealso K. Kofika, Principles ofGestidt Psychology! 1935, esp. Chaps.

On his usa of the term athe. cU. infra, 1024.

Kiiipe's experiment

Bryan)

isin part upon this experiment,

is

Tile

1, 15, an4, on double representation,

relation of sensation to other cate-178-183,

gories260-264,

scious meanings
is still

debatable.

Whethercon-

do or do not 'exist'

in contemporary psychology,P^chol Monogr., 16, 1913, No, 1.
Titdiener’s lepy and rcorionlation

NOTESof his system toward dimensionsisand system, Amer. J.

his Sensation

Psychol, 26, 1915, 258-287. Titchener never publislied on his dimensionalism,

eicrat a tiny note, Theis49
M. von Hombostcl, Die Ein-

E.

hoit

dec Sinne, Melos:

Z Uusik, 4,

1925, 290-297, [n.v.], Eng. Irons.,

Psyche, 7, No. 28, 1926, 83-89. See
also C, Hartshome, The Philosophy

term attensity,‘^iiiii, 35, 1924, 150.

and Psychology of Sensation, 1934,

The present anthor’s reinterpretationesp. 29-80, 209-242, 277. Von Horn-ofbostel’s triangular equation of biight-

dimensionalism,

Titchener’scit„ 1933, isop.

the work of a younger

man trying to make his master clear
and simple, and would probably havebeen no more accepted by the master than was Kulpe’s sunilar attempt(1893) to clarify and modify Wundt.
For tbe repetitions and modiSca-

lions of Eulpe’s experiment, see

M.

Yokoyama as reported by E. G. Borand sensation, Amet.

ing, Attribute1.

Psychol , 35. 1924, 301-304i R. W.

nesseswMch was not confirmed
by N. E. Cohen, Equivalence of
517-538,

brightnesses across modalities, Amer.
;.

Psychol, 46, 1934, 117-119.

For older comparisons, see, in general, E. B. Titohener, Experhnentd
Psychology, II, ii, 1905, 190 f.; and,xur Theotie der Sinnesmahtnehmung,(1858)

experiments on abshaction, ibid., 30,berg,

324-340; D.

W. Qiapman,

W. Wundt, Borage

in particular,

Wilcocks, An examination of Kulpe’s
1925,

Ueber GeruchsheDig-

his

is

Arch. ges. Physiol, 227, 1931,

keit.

1802, 33-40; H.

BeitiagemiMiinster-experimontellen

Psychologic, m, 1890, 56-91.

Relative effects of determinate andAufgaben,indeterminate

ibid.,

44,

Nativism and Empiricism

1932, 183-174; P. M. Zoll, The pluri-

dimensionality
ibid., 46,ofIn general, on the nativistio andconsciousness,

1934, 821-626.

empiricistie

theories,

see T. Ribot,

For S. S. Stevens' determinations

Lo psycholode allemande contempo-

of isophonio contoura for tonal vol-mine, 1879, Eng. irons., 1886, Cliaps.

ume and density and his conception

8,of an attribute as a sensory para-

Helmholtz’s Handbuch der physlolo~

meter, see his The attributes of tones,

gischen Optik, 3 ed.. Ill, 1910, 497611, 620-534, Eng. trans., IH. 1925,

Proc. not. Acod.

Sd Wash, 20, 1934,457-459; Volume and intensity of
tones, Amer. J. Psychol, 40, 1934,

397-408; Tonal density, 1. exp. Psychol, 17, 1934, 585-592. For a similar

conception of the attributes of

4 (dreary);

von Kries,

J.

in

H.

607-625, 635-652 (best reference);
0. Klemm, Geschichte der Psychologie, 1911, Eng. trans., 1914, Chap.
11; G. S. Brett,chology,III,

A History of Psy-

1921, 110-116. James’

color, see £. G. Boring, Isochromatic

chapter on space perception is clas-

contours, Amer. J. Psychol, 39, 1937,

sic

130-134. On the general relation ofend discussion of, this literature: W.

attributes

numbertothe stimulus and die

and replete with references to,

James,

Piinciples

oj

Psychology,see1890, n, 134-282. See also the fur-Boring, The relation of the attributes

ther discussion in this book, esp. pp.

of sensation to the dimensions of the233-238, and also pp. 475-^3.

ofpossible

stimulus, Phil.

attributes,

Scl, 2, 1935, 236-

For Johannes Muller’s nativism,
Zur verglelchenden Fhysi-

see his245.

oiogie des Gesicltssinnes, 1826, esp.

Unity of the Senses

71-90.

For Ewald Herlng’s nativism, see
In general, see G.

W. Hartmann,

Gestatt Psychology, 1935,

141-151.

The basic, if somewhat poetic, paper

esp.
(

his

Beltrdgezur

Physiologle

which is all Zur Lehre uom OrtsinnederNefahrtut),

1861-1864.

Von

SENSATION AND PEIICEI'TION

so
Kries

has

noted

that

ad-

Ilering

On Kiilpc and Tilchem'r, see 0.

mitted Ills sympathy with Jnhanut'S
MiiOei’s views. In Ihls inslanro, Hi't-

Kidpe,

ing followed Miillei, and Helmholtz
rejected Muller, tliougli Helmholtz

379; E. B. Titehencr,

applauded Mfillor’s dootrme of sixj-

326, 330-332, 36-1-171.

tjfnin/ii.s*

316-393,

1893,

Psychologij,

cinc nerve energies os llie greatest
psycluilogicnl law of that day.

For C. Stumpf’s nalivism, see histleisf dm psycholo^schen Vrsprung
der RaumvoTstellmg, 1873. See also
E. G. Boring, A Hittory of Ezjicrimental Psychology, 1929, 3S2 f. Fur

brieflyof the mattersgreaterThe

321-

mcntiiiiuxl

are discussed atelsewhere

this

in

Incnmparaiile

secondaryhistoryof p.syehn-

physiesis

S2S-4S2, and soattored reforenoes inte.\llengthpmm, Akad, Wtss.,

1906, No. 4,
For R. H. Lotze’s empirielsm, see
his Uediclnische Fsijchmtgle, 1852,

331

lUnik ofbook; see text for eioss-referenees.
for

Ai/i.

'I'i'v/

303 306,

191(1,

in thesourcephil-hist. C!.,l'.vi/i7iii/i)gli',

Ir.in'.,,

Psychophysics
Many

Stumpfs phenomenology, see Erscheinungen und psyohische Funktionen,i/it
I'hig.

theE. B. Tiichener, Experi-mental Fst/chology, II, ii, 190,5, .xiiielwi, 99-121,
109-187, 191-19-1,
210-232, 37.5-318. Knlpi- (-.illi-d thisIxiok the niosi eintliie psveliologieiil

his

Ixiok in Englisli. On 0. T. Fo'liiier’s

also Boring, op,ut-i'omii

lata philosophical works. .SeccU„ 2.50-2.59, 261 f.
For II. lielmholtz’s ompiricism, Siv

his

his

III

own aiitri'cili'uls. see

E/i’meilletier

I'o/ehirplii/dk,

Ihe 1889 repilnl, .5(8 ,560,

primarily his Die Tlwlsaclwn In der

186(1 orWahmcnmmg, 1878 (or 1879), r<>-On Feelmi'r, see E, 0,

lnted in VorMigo iitid Itedi'ii, 1884,

S 217-271, Ilolniliollz Ilnd had

ilils

idea in 18SS, It

llic

.

Is

iinplleil inthought of the Optik,

1856-1800,

Hoiiiii',

A

lIMtrri/of Experlineiilrd /’si/i7iii/iiijK,1029,26,5 287,J.

F,

rierliiirl'.s

Fsyriiiilrigli'

id.ielussie,ilwiii).

H’I.s.mti.sc/iii/I,

Is

iieii

Hi/ii/ii wig,
Mela
attf
phy.dk und Mnlhemallk, 182-1 182.5.

and explicit, for insianee, in his discussion ihorc of perceptual nneon-

grgriimh't

scious inference as karnodi sec the

On llerhurl, see Ihiriiig, up, ell,, 238

Optik, op, cll,, 1 ed., 1866, or 3 ed,,250, 259-261! inul on I.eil)nit/, 165

or Eng. trans,. III, sect. 26. Tliieo

168, 177 f. The birth of Weher'-s law

papers on die axioms (1806-1878)

oceni's In

are reprinted in Helmholtz’s Wlssen-

rpsorpilonc,

schaftUche Abhandlungon,

tnllonc,s

II,

1883,

II.

F..

Weher, He

auditu ettiirltu-

ptiLw,

anno-

anatmniaic et physlirluglae,

610-660. See also J. G. MoKendrick,1834,

Hermann Ludwig Ferdinand oon

Der Tastsirm und das Clenwtngefuhl,

Helmholtz,

1899,

250-207i

G.

S.

Modern Psychology, 1912, 256-259; von &ies, locc,oiti,; Bating, op, cit,, 296-303, 308 f.

Hall, Founders of

Pox W. Wundt's empiricism, see its
beginning in his Beitriige xur Theotie
der Sinneswohmehmung, 1862, esp.

66-104(1859), 376-451 (1862);
Vorlesungen iiber^ die Menschen-

und Thierseele, 1883, Leot 17 (notin 2 ed.). For the final form of his
views, see his Grmdzilge der physio-

logischen

Psyohologie,

6

ed,,

1911, 530-788, esp. 70^736.

III,

86-03,

132-142,

1,59 -161:

in B. Wngner’s Hwidiefirler/jiie/i derIII, ii, 1846, 546 -.5-19,
or 96-100 in the 1905 reprint.

Physlologle,

J.

B. L. Delboeuf’s ehief eontiihu-

Uons to psychophysics are as follows:
Elude psychophyskpie, Mem Acad,
Sci, Belg,, 23, 1873, No. 5: I'/ieoiio
gendrolo de la senslIillUt’, 1870;
both reprmled together with slightabridgment ns Elements de psijchonhmiquo, 1883; lixamen riUhpie

de la hi psijdhophysique, 88.3. G. E.
Muller’s iiooks are Zur Crundlagiing
der Psrjehophysik, 1878; Die Ge1

NOTESsichtspmhe uni die TaUaohen det

nclwphusischen

MethodlJt,

L.

in

51

tions, see Urban, Tire method of con-stant stimuli andits

generalizations,and K. Spiro, Ergahnlm der
Physlologle, ]hrg. II, abth. ii, 267-

Boring, Is there a generalized psy-

516, which is more often seen as thechometric

reprint with separate paging of 1904.

atPsychol Rev.,

1910,

17,

229-259;

Amer,

functiorm,J.

W. Wundt’s discussions of psycho-

Psychol, 35, 1924, 75-78.
On the elimination of die equal

physics are scattered through the six

category and the use of the prob-Pm-

able cnor instead of die limen, seechah^e, 1874-1911. J. Merkel published 14 articles on psychophysics
in the Phil. Stud,, vols. 4-10, 1887-

C. S. Peirce and J. Jastrow, On small

1804. Titchener’s text is cited above.

Fullerton andeditions of the Fhystohgische

M. Urban's classic is The AppU-

F.

oatlon of StatiMcol

Methods to theMem. nuf.

difierences of sensation,

Acad. Sci., 3 (1), 1884, 75-83; G. S.

McK.

J.

CattoU,On

the Perception of Small Differences,
1892, esp.

150-152,

1-20,

On theProblems of Psychophysics, 1908;but see also opp. citt. Infra. A mod-way in which instruction and atti-

em text combining the psychophysi-

judgments, see Warner Brown, The

and statistical methods

cal

Psychometric

Guilford,P.

judgment of difference. Unto. CoUf,

Methods,

PuSl Psychol, 1, 1910, No. 1, esp.

isT.

41-51;

28-84,

1936.

On die history of tire method of
see TUchener,

limit!,

121.

tude reduce or eliminate the equal

op,

99-

cit.,

On sensory quanta, see S. S.

Tlie

effectsubject
tivity,

of

S.

W.

Fomberger,

the attitude of theupon the measure of sensiAmer. }, Psychol, 25, 1914,

Stevens, C. T.

Morgan and J. Volkmann, Tlieory of the neural quantum

538-543. That, when attitude is con-in ihe discrimination of loudness and

ftd

Amcf.

pilch,

J,

Psiicliol.,

54,

1941,

hS-33S.

trolled,equal need not moan doiibt-

has been shown by D.

Cart-wright, Relation of decision-time tothe categories of response, ibid,, 54,

On the history of the method of

1941, 174-196.

(constant

On the liistory of the method ofsiinuli), see Tilchener, op. cit., 275-

average error, see Titchener, op. cit.,

right

and wrongoases

318. K. Vierordt inspired the Brst,
ifcrude, use of this metliod by his

F.

pupil,

Hegehnaier,

Ueher das

100-187. On die mediod, see Feohner, op. cit,I,

120-128.

On die history of the method ofGedhclitniss fitr Llnearanschnuungen,equivalents, see Titchener, op.

Arch, physiol. Heilk, 11, 1852, 844-

On the early use of themethod, see Weber, De pulsu, op,853.

Then came Fecbner, op.

cit,

93-120; Muller, op. cit, 1878. 765; Ueher die Massbestimmungencit.,

191-194.

1834, 94-113; Der Tastsinn und
das Gemeingefufd, in R. Wagner’s

I,

cit,,

dcs Ortssinnes der Ilaut mittolst det

HandwSrterbuch der Physiologfe,
in, ii, 1846, 548 f., or 98-106 in the1905 reprint; Wundt, Beitriige zur
Theorte der Sinneswahmehmvng,(1858) 1802, 34-43; Fechner, op.

Melliodc der lichtipn und falschen
FBfle, Aroh. ges. Physiol, 19, 1879,

191-235 (weights for frequencies,

method of least squares); op.

cit.,

1904, 12-163; Urban, op. cit., 1968,

cit., II,

315-322.

Die psychophysi-

On the history of die method of

schen Mussmethoden als Grundlagen
empirisclierequal sense-distances, see Titchener,
op. cit., 210-232. ‘The early experi-

psychometric functions really are in-ments are J. A, F. Plateau, Sur lamesure des sensations physiques.
Bull. Acad, Sci. Belg., 2 ser., 33,

19-39,

99-171;

Messungen, Arch, ges,
Psychol, 15, 1909, 261-355; 16,1009, 168-227. As to whether thetegratednormal prohabili^

func-

1872, 876-888;

J.

R. L. Delboeuf.

SENSATION AND PERCEPTION

S2

Htude psycliophysiquc, op, cit,, 1373,
50-101, reprinted in Eidmenfs de

ness,

its

and

calculation,

psycJiophjsique, 1883, 50-91.

Amcr.,On me equality of j.n.d. for pitch,see 8. S. Stevens, J.

Volkmann andmeasurement

dednition,

iicnimt,

J,

Soc.

82-108; Fletcher,
Newer concepts of the pitch, theloudness and the timbre of musical
1933,

S,

E. B. Newman, A scale for the meas-

tones, J.

urement of the psychological magnitude of pitch, /. acoust. Soc. Amor.,
8, 1937, 185-190; Stevens and Volkmann, The relation of pitch to frequency: a revised scale, Amer. J.
Psychol, 53, 1940, 329-353; seealso Stevens and H. Davis, Hearing,41^429; Churcher, A loudne.s.s scale

1938, 84-89, 95-07. On the inequality of j.n.d. for loudness, see Stevens,

Fletcher andFmnklln Imt,, 220, 1935,

for industrial noise measurement,

Amcr., 6],

1935, 210219 f,); Stevens, op.
cU., 1930; Newman, Volkmann andStevens, op. cit, 1937; Stevens andacaust.

226

Sac.

,

(history,

Davis,

op.

cit,

1938,

112-122.

Munson did not makeA scale for the measurement of aa ratio scale from their own data,
which demonstrated only the rela-magnitude: loudness,
Psychol Boo., 43, 1930, 405-416;

They

psychological

Newman, Volkmann and Stevens, On
the method of bisection and its relation to a loudness scale, Amcr, J.
Psychol, 49, 1937, 134-137; sec also
Stevens and Davis, op, clt., 147-152.

mtiwd a/ scnso-mtlos began

Tliotion of diotie toassumedmonotic loudness.
onphysiologicalunds that diotie loudness would
twice the loudness of monotic
stimulation, but the point could not
be cstablislicd until there wore thc.seother ratio data by which io conthelimi

On scales ofhypothesis.

Volkmauu andwith J. Merkel, Dio Ahhiingigkelt
zwischen Rate und Enipllndung,Phil Stud,, 4, 1888, 545-547, 502-

pilch,

505; 6, 1889, 245-291, 499-557; 10,1894, 203-248. For Us application to

Stevens and Davis, op.
054)7.

seo Stevens,

Newmann,
andup.

Volkmann,

1937; Slovens

clt,

op,

clt,

1040;

alt.,

84-80,

loudness, seo L. F. Richardson andTlic ohmlllenllon of iho scales ofRoss, Loudness and telephoneraonsurcmienl ns ordinal, iiUervnl andcurrent, J, general Psychol, 3, 1930,

ratio scales is dno to S. S. Stevens in

288-306; D. A. Laird, E. Taylorand H. H. Wllle, The apparent re-a MS. as yet unpubltshod (VM Intcrnal, Congr. Unity Set, 1941).

J,S.

duction of loudness,I,

acaust. Soc.

L B. Ham

Amer,, 3, 1932, 393-401;

and J.

S.

On the quarttltij objection, see BorThe stimulus-error, Amer. 1.

ing,

1932,

Psychol, 32, 1921, 449-471, esp.
461-400. For W. James' account of

H. Geiger and F. A.

psychophysics and his opinion of it,

Parkinson, Loudness andintensity

relations.

511-534;

P.

Firestone,

The

Ibid,,

3,

estimation of

frac-

see

his

tional loudness. Ibid., 5, 1933, 25-30;

1890,

B. G. Churcher, A. J. King549).

and H,

I,

Principles

of

Psychology,

530-649 (contempt, 533 1.,

perceptible

On Webers law, besides the cross-change of intensity of a pure tone,references in the text, see the sum-

PM,

Mag., 7

ser.,

939.

On dieconstruction

of

ratio

mary ol tire results of A. H, Holway
and C. C. Pratt, The Weber-ratio

scales

from

these

see

H.

Davies,The minimum
18.

1934,

data,

927-

Fletcher and W. A. Munson, Loud-forintensilive

discrimlnatton,chol, Beo., 43, 1830, 322-340.

Psy-

Chapter 2

PHYSIOLOGY OF SENSATION

N this chapter we consider the history of the general problems

Iof the physiology of sensation; conduction and its relation to

the perception of quality and intensity, specific nerve energies

and die general theory of quality, projection in its relation to theperception of quality and extension, and the problem of mind andbody as it appears in the theories of psychophysical parallelism
and isomorphism.

Nerve Conduction

How does the incorporeal soul, residing within the brain, movethe muscles of the body to wliich it is attached? One answer to thisquestion was the following. The inspired air of the lungs passes tothe heart, where it is distilled into the vital spirits which, distrib-

uted to the body through the arteries, constitute the breath of life.

Coming to the brain, the vital spirits are tliere, however, changed
into animal spirits,

which are stored in the brain’s ventricles orconveyed to toe muscles through the nerves to produce motion.

These animal spirits, entering toe muscle, distend it, causing it toshorten and to move the member to which it is attached. Anyone
feeling the contracted biceps knows that a muscle swells when it isactivated by the soul, The soul itself is these spirits, a Pneum.

That was toe pneumatistic doctrine of Erasistratos in the third
century before Christ (ca, 258 b.c.), a doctrine which lasted along time.

Galen (ca. 175 a.d.) accepted Erasistratos’ doctrine, complicating it. The natural spirits, necessary for growth and nutrition, aredistilled, he believed, in the liver. In toe heart, however, they are

combined with air from the lungs to produce the vital spirits, essential to life, which in turn are transformed in the brain into theanimal spirits for distribution through the nerves to the body.

Mankind seems always in civilized ages to have needed the concept of spirit, an incorporeal substance which constitutes toe es63

PHYSIOLOGY OF SENSATION

54

sence of a corporeal object. In man it was plain that life and thesoul are contained in tlie body without ocaipyiug any space there,
tlvat they are in character spiritual.

When Descartes (d. 1650; published, 1650, 1662) came to thisproblem ot neural conduction, he followed Erasi.sliatos and Galenin accepting the animal spirits as the essence ol the soul, and theirpenetration of the pores of the brain and conduction through thenerves as the reason for movement. The muscles contract, he repeated, because the animal spirits inflate them. The soul, conter-minous with the body, is inextended substance; the spirits are a"very quick wind,” “a very active and pure fire." One begins to getat this time the notion that the animal spirits have in themselves
force, are, as Huygens put it in 1669, a uis vim; the soul directs theactive spirits to the muscles and does not have to pump the muscles
full of tlrem.

Willis in his important De molti animaliiini ol 1670 accepted thedoctrine of animal spirits, as did Bnerhaave later in 170(1; yet al-

ready die paradox of an incoiqwcal substance was beginning totrouble the theorists.

The trend toward a more substantial ino-ohanical action began early.
It was Glisson in

1077 who perfonuod an experiment and also

invented an important concepL The experiment consisted in theuse, obviously the first, of a ‘pldhy-smometer’i the arm was iiUievlod

downward in a long glass vessel, wliieh was filled with water
fluough a funnel at die top; when the muscles of the aim wore
contracted, the water' did not rise in the funnel. In olhor words, themuscle, though it may change shape on contracdon,isnot en-larged; nodiing is added to it to make it swell. Glisson’s importantconcept was irritability: muscular tissue is in itself irritable, he
said;

it

contracts when stimulated, not because it is inflated byanother substance, but because contraction is inherent in its nature.

With this word Glisson introduced into physiology the notion diat
serial bodily action results not from die transmission of any sub-stance, fluid or spirit, but from the release of action inheient in

the nature of the tissues themselves.
Borelli (1880) folbwed Glisson. He held that a corporeal agent,

the sucGUs nerceus (not the incorporeal animal spirits), is trans-mitted through the spongy ducts which are the nerve fibers; yet

he left the matter open as to whether the transmission might not
be the conduction of "some emotion” along the nerves rather than

ANIMAL SPIRITS AND ELECTRICITY

55

a material succtis neneus. In any case, he asserted, something new
must, in contraction, be added to the muscles; “on the arrival of
the influence transmitted by the nei'ves there takes place [in amuscle] something like a fermentation or ebullition, by which
the sudden inflation of the muscle is brought about.” He did not,therefore, settle the question as toinflates or merely irritates

whether the mcous neroeus

the muscle.

There was another important experiment performed by Swammerdam (d. 1680) about 1680, although it was not published until
1737, bng after its author’s death. Swammerdam used a nerve-muscle preparation to show that the muscle contracts when thenerve, thus separated from the central nervous system, is stimulated by pressure. That result certainly tells against the animal
spirits

and for irritability.

Swammerdam also showed that thevolume of the muscle, when thus contracting, does not change,
thus anticipating Glisson, although his failure promptly to publish
his resultsrobbed him of the immediate influence that his dis-covery might otherwise have had.

In the eighteenth century the notion of animal spirits or vis viva
persisted in tire common thought of physiologists but was looked

upon askance by the sophistioat®, who, if they used tire terms,
gave them a more mechanical connotation. Robert Whytt, a pioneerin the study of reflex action, spoke of animal spirits in 1751 but
specified that he meant only "the power or influence of the nerves.”

Unzer in 1770 substituted the phrase iris nervosa.

Meanwhile the knowledge of electricity was growing. Gilbert

worked out the laws of electrical attraction and repulsion in 1000.
Guericke invented the friction machine in 1672. The Leyden jar
dates from 1745. Benjamin Franklin reported his experiments onelectricity in 1774. It was at some time before 1780 that Galvani

started his experiments on the stimulation of frogs’ legs (nerve-muscle preparations) by electric discharges. Thus by 1791 he hadconstructed the first electric battery out of a frog’s leg and two

metal rods. These experiments are the reason that direct currents

from a battery were later called galvanic currents—although thereally effective pioneer in the invention of the battery was Volta(

1800 ) The first galvanometer was made in 1811;'the first one sen-sitive.

enough to be practicable for measurement, in 1821. Ohm

formulated his well-known law for galvanic currents in 1827, andF echner, then a promising young physicist, made his first important

PHYSIOLOGY OF SENSATION

56

contribution to science in 1831 on n problem of the galvanic chain.
It was also in 1831 that Faraday discovered electromagnetic in-duction, a discoveiy whicli resulted in the invention of the in-duction coil and the consequent availability of taradic currents forthe stimulation of nerve and muscle. In these years physiology andphysics helped each other: the first battery was a live frog’s leg,

yet without faradic currents to stimulate nerve

arrd

muscleand without galvanometers to measure physiological poterrtials,

du Bois-Reymond would never have published in 1848 the first
volume of his famous work on animal electricity. Now let rrs goback to Galvani.
Galvani worked mostly with frogs’ legs to which the nerve andlower section of the spinal cord had been left attached. His initial
discovery was that lire legs, when hung from an iron trellis by brass

hooks passing through the attached section of the cord, worrld
twitch when discharges from an electric machine or a Leyden jar

occurred in the neighborhood, or when lightning flashedinathunder storm. Later he found that he could cause a log to kick at

any time by completing a circuit from the loot to the nerve throughtwo rods of dilloront molals, Tho end of one rod was jrlaeod incontact with the foot; lire cud of the other tod touchod the nerve.

'When the free ends of the two rods wore hronghl together, themuscles contracted, the log kicked.

A coinroction from foot tonerve by a single rod would not work; two metals aro requited.

A leg, suspended by iho nerve from a brass hook connected to theground and with its foot touching a silver plate, would continue
Idcking indefinitely, since each kick broke the connection, allow-

ing the leg to drop back into contact with the plate. From dieseexperiments Galvani concluded that animal tissues generate electricity.

He presented this theory in De viribus electricAtaUs in motu

musculari, published in 1791, He was, of course, right in his belief inanimal electricity: a living organism establishes potential

On the other hand, he waswrong in assuming that his experiments proved the point conclusively. Why was one metal not enough? Why did he have to complete the circuit with two? What he had here was simply thedifferences in different parts of itself.

world’s first moist battery, with the frog’s tissues providing theelectrolyte.

Volta was prompt to make this criticism. He verified Galvani’s
experiments, emphasizing the dependence of the contraction upon

ANIMAL ELECTRICITY

57

there being two different metals in oontaot in the oircuit To prove
his point he substituted paper moistened with water, brine or lye

for the frog’s leg

and nerve, connecting many of these units inseries to get a very considerable electromotive force.

His first ar-rangement, described by him in 1800, was the Voltaic pile, as itcame to be called; he stacked in a pile a disk of silver, a disk ofmoist paper, a disk of zinc (these three make the first unit), andflien more disks, silver, paper, zinc, silver, paper, zinc. Between
the topmost zinc and the bottommost silver a very considerable
electromotive force existed, He also got the same effect with aseries of cups, eacli containing a liquid electrolyte, a silver plate

and a zinc plate—with the silver of one cup fastened, outside thecups, to the zinc of the next.

Such series were presently oaUed

galvanic chains. Volta finally clinched his argument against Gal-

vani by making out a list of pairs of metals in the order of theirelectric effectivenesses.

He was able to arrange the metals in sucha series that the remoteness of the metals in tlie series predicted
their joint effectiveness in the galvanic cliain. Thus he built upon

Galvani’s discovery to invent the electric battery and series connection, turning attention

away from animal to inorganic elec-

tricity.

Just the same there is ‘animal electricity.’ Johannes MUller, dis-missing in 18S4 the animal spirits as the nerve-theory of the ancients, nevertheless suggested that the nervous Impulse might beelectrical Its speed, which he drought too rapid ever to be meas-ured, seemed to him to imply that eleefrioity might be the agent.

Several men were working on these problems. It was in 1841
that Matteucoi presented to the Aoaddmie des Sciences a paper

which showed that a galvanometer indioates a current when connected between the surface of a muscle and a wound in the muscle,
a current that was later called the “current of injury” and also
the “current of rest,” for it flowed without observable muscular
contraction. Muller showed this paper to his brilliant pupil (later
his successor at Berlin), du Bois-Heymond, whose interest was atonce captured by the topic, Du Bois, publishing his first paperin this field in 1843, had advanced so far by

1848-1849 that hecould then issue his two—now classical—volumes on thierische
ElektHcUat. In them he formulated what amounts to a theory of
the polarization of animal tissues, for he suggested that muscle

and nerve consist of electrically charged molecules, with a posi-

PHYSIOLOGY OF SENSATION

58

tive charge on one face and a negative opposite. Tlie.se molecules,—^miichhe argued, must orient tlicmselvesin theway that ori-

ented magnetized partieles make up a big magnet with a uortli
pole at one end and a south at the other. Obviously this theory was

not correct; yet it was an advance in the right direction because
it ledtoward the notion of polarization.

It wasdu Bois-Reymond’s experiments that led Helmholtz in1850 to attempt to measure the velocity of the ncivous impulse—

and to succeed. Haller had estimated the speed at somewhere
near 150 feet per second, but Johannes Miiller, already suspecting

a relation between neural and electrical conduction, had thought
the velocity so great, perhaps comparable to the speed of light,that it might never he measured—since it would never be possible,

he said, to have a single length of neive stretching through ns greata distance as is required for the measurement of tho velocity oflight. Muller, nevertheless,made some resomtion on tliis matter,for he noted that the experiments of tlie astronomer Bessel on the

personal equation (reaction times lor the olrservatiou of stellartransits)

show tliat impulses can Ire slowed up in .such iiuuiimr

that a visual impression, starling bclnre an aiulilory one,may

nevertheless be perceived after it. Anyhow Helmholtz, inventing

Iho myograph (a smoked gla.ss plate on a lalling pendnlnm whicli
records tracings of muscle twitches and instants of stimulation;

the antecedent of the kymograph), did measuru the speed of theimpulses .it about 27 meters per second in tho frog’s nerve. He

merely determined the dilTcrcncc in lime between stimulus andconti'action for stimulation at each of two different points on thenerve, dividing this difference in time by tire distairoo belweerr

the points. At first there was great skepticism, but Helmholtz wasright.

As research went on, it became apparent tliat the nerve impulse
is electrical in nature and also that it is not simply an electric cur-rent. Bernstein, a pupil of both du Bois-Reymond and Helmholtz,

showed in 1866 that tire impulse is a “wave of negativity” passing
along the nerve. He placed electrodes at successive points along
the nerve, finding that the surface of the nerve in the region of
the rapidly movmg impulse is always electrically negative withrespect to the surface ahead of the impulse and behind it. It is asif

the impulse were an injury passing along the nerve, for an

injury is negative with respect to the uninjured surface; or, to put

NEURAL IMPULSE

59

the same idea in other words, it is as if the impulse were a moving

region where the negative inside of the nerve spreads to the outside. It was

only a short step from this position, which Bernstein

amplified and expounded fully in 1871, to the membrane theory

which he helped to establish much later in 1902, Tlie wave ofnegativity in 1871 became in 1902 a wave of depolarization.

Since the wave of negativity has a measurable duration, one

would expect some limit to the rate at which impulses can succeed each other. Kroneclcer in 1874 found this limit for heart muscle;if

a second stimulus comes

too soon after a first, it does not
excite at all. In 1876 Marey, wellknown for his development of
the graphic methods, coined theterm refractor]) phase to designate the interval during which

the second stimulus is ineffective.

Ho,

too,

was working with themuscle of the heart. It was Gotdi

and Burdi who, in 1899, showedthat nerve,

likemuscle,isre-fractory. "A second electrical re-sponse does not occur if a second

Fk. 3. Excitaeiutx and RsniACTODY FiUSEi AoBUN AND
Lucas (1912)
Excitability of neivc (reciprocalof ihiesbold value; see Fig. 4) as

stimulus succeeds a predecessor

a function of the interval by which
the stimulation follows a previous

at less than a certain interval.”stnnulation.

This interval, they showed, varies
greatly withtlie

temperature ofdie nerve. Gotch was not siuein 1899 whether their experimentbility.

The

100= normal excita-

supernortnal

phase(above 100) turned out later tobe an artifact; the function should
approacli normal excitability as an
asymptote. From Adrian and Lucas, J. Fhysiol,, 44,

1912, 114.

might not have involved an artifact resulting from an inadequate means of measuring the pres-ence of the impulse, but in 1902, with a capillary electrometer, heclinched the matter. A decade later (1912) Adrianand Lucas

plotted the curve of the recovery of excitability after an initial
stimulation (Fig. 3), showing that there is at first an absoluterefractory period during which no stimulus is strong enough toexcite the nerve, and that it is followed by a reiative refractory

period in which excitability returns gradually to normal. (Theirinitial finding ofsupernormal excitability just preceding normal.

Fig. 3, was not born out by later research.)

PHYSIOLOGY OF SENSATION
The facts about refractory phase are best shown by the curvefor the threshold of excitation during recovery after initial stimulation (Fig, 4). This function, however, tells us nothing at allabout the magnitude of the tlmeshold response, which is, of course,

governed by the aU-or-none law.

Hiat law dates from Bowdiloli’s
research in 1871, when he foundthat

any stimulus produces inheart muscle either the maximal
response, or,if

die stimulus

istoo weak, no response at all. An
intermediately

strongstimulus

does not produce an intermediTime Inieml eTHr iniml exetnrion

ately
Fks, i. TuEuaiiQLD

TOST Piiasb;

AND Refrao-

Adbun (1913)

Absolute and relative relractory
periodsasshown byfunction

the function ofparllcularisthe basis

mg,

3,

the

irritability inherent in the muscle
fiber. Lucas in 1905 extended thisbutfinding to skeletal muscle, show-foring that a cmitinuous iuorouso in

this

tho Strength of tho stimulus at the

curve shows no super-

normalphase

Phi/sloal

Dimensions of Comlous-

docs Fig, 8.
Adapted from Adrian by Boring,
ncjs,
nets,

for

throsholdvalue of a second stimulus. This
sort ofstrong response,

slimulus acts only to release the

as

” la

i

,

results in aof r&sponSt'S

illi

graded senes

the musclci thein ,. espouse Is stepwise,

1033. 39.
1933,

ship Ihe aU-or-none principle. Working at tiiat lime on a very small

muscle supplied by a nerve with only eight or nine fibers in it, ho
discovered tliat ihe muscular response was stepwise and that there

were never more steps than there were fibers in the nerve.
Actually this finding ImpHed that the all-or-none principle might
reside in nerve as well as in muscle, but the matter was not fully
settled until Adrian, Lucaa’ pupil, showed in 1912 that an impulse,
after passing through a region of the nerve where its strength has

been decreased by a narcotic, spontaneously recovers

its

full

strength, provided only that it succeeds in getting through thenarcotized region at all.

He passed the nerve through a smallchamber, within which it was exposed to alcohol vapor, measuring the action current (Bernstein's wave of negativity) before thedhamber, in the chamber and after the chamber. He was vvrong
in supposing that the strength of response diminished progressively within the chamber (conduction with a decrementj Kato in

MEMBRANE THEORY

61

1924 showed that to he an artifact), but right i? concluding that

normal nerve gives its aU, if die stimulus .is strong enough, or
nothing if the stimulus is too weak. If any doubt remained about
this matter, it wasremoved by Adrian’s second paper in 1913.

It is hard to say wheiher Lucas or Adrian, the master or his pupiland successor, established the all-or-none law for nerve. Lucas’

NormalRelativejexcitable fiber refractory periodjFio, 5.

|'3£olNormal1||

excitable fiberjMemebane TuEoKy or Nebvb-Comduotioh

See fast for explatiolion.

permeable membrane

The senii-penneiible membrane is black; theat theregion or the impulseiswhite; continuous

recovery of partial impermeability during the relative refractory phasecross-hatched.

is

Adapted from Forbes by Boring, Physical Dimensions ofConsciousness, 1933, 40,

untimely death in 1916 cut short his work, and it was loft for Adrian
to publish Lucas’ lectures summarizing theknowledge about.

nerve-conduction as of that time.
Closely connected with the facts of refractory phase and aR-ornone response is the mernirane theory of nerve-conduction. This

theory supposes that the nerve is covered with a semi-permeable

membrane (see Fig. 5), and that it is polarized—-with the small
positive ions penetrating die membrane and rendering the surface
electrically positive, and the large negative ions bound electricallyinside themembrane. Stimulation breaks down the partial im-permeability of the membrane, initiating a local eddy current,

which is the impulse. This local current itself destroys the impermeability of the adjacent membrane, thus extending itself tothe next region, leaving the membrane fuUy permeable and thus

PHYSIOLOGY OF SENSATION

62

depolarized and relvactory. Tire nerve, however, soon recovers excitability,

passing through a phase of relative refractoriness midpresently reestablishing its normal polarization. Such is the mem-brane theory.
It wasthe chemist, Ostwald, who, in 1890, first proposed thistheory. He worked out the olectrochemisti'y of the process without

experimentation upon actual tissues. The theory was fairly wellestablished by Bernstein in 1902, who found that the facts of con-duction in both muscle and nerve vary with temperature after themanner in which membranous permeability ought to vaiy. He
called the impulse a concentration current. The weight of evidence
for the membrane theory was, however, accumulated by K, S. Lillie in a long series of publications

beginning in 1909, In 1920 heduplicated the neural phenomenon with an iron wire immersed
in nitric acid. Such a wire has a membrane of oxide formed uponit.

The acid supplies the positive ions on the oulsidc. Any stimulusthat breaks the fihn of oxide, like, a scmlch or an eli'cttic shock,sets up a concentration current which travels in both cliroelions,propagating itself by destroying the film ahead of it. Then the wire

remains relraotory idtor the passage of the. impulse, until the acidreform.s the polarizing film.

Tho ndotpiuey of such a model in

duplicating events that ai'C proper to a nci'vc fiber lias gone a long

way toward seeming the acceptance of the membrane theory.

Sensory Conduction
In the days of the animal spirits and the vis twrvosa tliere wasno very special theory of sensation. The spirits wore supposed togo through the nerves from the brain to dro muscles to produce
motion, or from the sense-organ to the brain to produce sensation.
Haller (1747), who thought of the nerves as tubes and the spirits
as a watery, albuminous juice, noted that muscular motion, as seenin convulsions, can be more violent than sensation. He suggested

that this difference occurs because the brain is at the top of theorganism, so that the course of the spirits is always downward formotion, whereas in sensation Ihe organs of sense have to force
tile spirits upward. There might sometimes, hethought, be con-

downward movement would prevail; sensation
occurs only when “it is resisted by no sensitive torrent coming

flict and then thfe

from the brain in the opposite direction.”
Sensation came, however, into its own as a separate physiological

SENSORY NERVES

63

problem with the attention gained for it by the Bell-Magendie law—the rule that the sensory and motor nerve roots at the spinal
cord are separate. It was, of course, not entirely a new notion of
the nineteenth century that movement and sensation should haveseparate nerves. Erasislratos had said that they do. So had Galen,

Descartes and Whytt. Beliefs without experiments are, however,

not always convincing, Certainly they did not convince Haller,

whose appetite for bodi evidence and the opinions of others wasomnivorous. Bell it was who, in an obscure pamphlet privately
printed for his friends in 1811, described how he sectioned theposterior nerve-root at the spinal cord without convulsing themuscles, whereas touching the corresponding anterior root withhis knife, after hehad cut the posterior root, produced violent

movement. From such evidence he concluded that the posteriorroots have only a sensory function, and the anterior roots only a

motor function. Magendie, in 1822, not having seen Bell’s private
publication, described a much more convincing experiment.

He

sectioned the posterior root to find that the limb supplied by it

was quite insensitive; no pricking or pressing could get it to move.

He was just about to conclude that it was paralyzed, when the
animal moved the limb spontaneously, proving to both Magendie

and us that the limb was not paralyzed, but only anesthetic. Section of the anterior root, on the other hand, destroyed all move-

ment, whether the dorsal roots were cut or not, except, of course,when Magendie applied the stimulus to die distal side of thecut. Thus Bell had die idea first, but Magendie made the same
discovery independently, performing a more convincing experi-ment. History has setded the controversy that arose about priority

by naming this law of the spinal roots for both of these great physiologists.
It was in thissame obscure paper that Bell noted that every

sense has its own peculiar quality, that pressure on the eye gives

a sensation of light and that a touch on a taste papilla gives agustatory sensation. Johannes Muller in 1826 expanded this kind ofargument into what became presently ( 1838 ) the famous doctrine—a doctrine which we must con-of the specific energies of nerves

sider in the next section of this chapter. Here we may note onlythat the doctrine represented a five-fold subdivision among thesensory nerves. Instead of a single vis nervosa for aU motor andsensory nerves, Muller asked us to believe in five. sensory vires

—
PHYSIOLOGY OF SENSATION

64

neroosae— call them what you will

vis,

—

Kraft, force, Energle

there was not much difference in the use of those words in the days

before the tlieory of conservation of energy became important.
Later, of course, Helmholtz and others hypothesized a different en-ergy for every quality within a sense—^but see the next section.

The character of die nerve impulse was detemined almost entirely, as we have seen, by experiments with motor nerves. Galvani
could see die frog’s leg kick. Gotch could record muscle twitches

on a kymograph. Ultimately it became quite clear that the principles of refractory phase and of the all-or-nonc response apply
alike to muscle fiber and to motor nerve fiber. The facts, worked

out for muscle first, were then found true for nerve. It was sup-posed that sensory nerves must be like motor nerves, but at first

no one was sure.
Knowledge of the nature of sensory conduction had to wait,
however, not only until motor conduction was imdei'stood, but also
until the advances in physical science provided suitable apparatus

for measuring action potentials in nerve. In iho nincleonth cen-tury one could learn something about motor conduction because

one had a muscle at the end of iho norvo to glvo observnblo
twitches. At the end of a sensory nerve there was only introspec-tion and no one could tell whether die diffcroiioes between stimulus and perception ocaurod in the peripheral or the central nervous

system, It is true drat the nineteenth century had galvanometers

but they were not sensitive enough. In the twentieth century
there appeared first the sensitive string galvanometer, dicn thecapillary electrometer, then the method of thermionic amplification,then the cathode ray oscillograph, and lately all sorts ofmethods for observing and recording the frequency, amplitude andwave-form of amplified currents. For these later techniques physiology owed its thanks to the development of the radio.

Thus it has come about that the great advances in the knowledgeof afferent conduction—not the very beginnings but most of theimportant insights—belong to the 1920’s and 1930’s. The literatureis large, but

we may summarize it under three topics. Adrian andForbes were the pioneers,
1.

Sensory action potentials. Steinach in 1896 seems to havebeen the first to measure sensory action potentials. He found thatthe wave of negativity in frog’s nerve varies directly with thepressure of the stimulus on the frog’s skin. After Steinach there

SENSORY CONDUCTION
were two or three other measurements of potentials in active
somesthetic nerve, and then in 1910 Buitendijk recorded, withelectrodes on the auditory nerve, potentials that were synchronouswith a heard percussion shot, We now know tiiat these measure-ments were probably not action potentials from the nerve but in-

duced effects derived from the microphonic action of the cochlea(the ‘cochlear response’; pp. 420-423), but at that time the artifacts of electrical induction were not well understood.

The nerve physiologists, especially Forbes and Adrian, all had
the problem of sensory conduction clearly in mind; yet theyneeded the discovery of the thermionic amplification of small
potentials before they could make the necessary observations. It

was, therefore, not until 1924 that satisfactory records of afferent

by Forbes, Campbell and Williams who

potentials were obtained—

used amplification widi a string galvanometer to record action
potentials initiated in somatic nerves by muscle receptors. In thenext few years, however, research accumulated so rapidly that wemust content om'selves here with a simple list of the kinds ofsensory potentials recorded or measured.
1924 Forbes, Campbell and Williams
1926 Adrian
1926 Adrian and Zotterman
1926 Adrian and Zotterman
1926 Adrian
1928 Adrian and R. Matthew:
1929 Adrian and Umralh
1930 Waver and Bray
1931 B.H.C. Matthews
1931 Davis and Saul

muscle; tension
skin, muscle, lungs, heart

isolatedmu^c spindle: stretch

skin: light touch and heavy pressure
skin: penetration by a needleaye (eel): light
Pacinian corpuscle: pressureear; speeoli and tone

isolate muscle spindle; contractionear;speech and tone

Perhaps Wever and Bray do not belong in this list as of 1930,
for certainly much of the speech and the higher tonal frequencies

that they put into the cat’s ear and then heard in a loud speakeras potentials amplified

from an electrode on the oat’s auditory

nerve came not from the nerve itself, but, like Buitendijk’s, as a

spread of biomicrophonic action in the cochlea. Davis and Saul

were first to make this correction, and soon, after appropriate controversy, the fact was admitted generally.

The discovery of the

Wever-Bray effect was, however, important in that it set off aseries of investigations in whidi the action potentials of the audi-

tory nerve became quite as common an object of observation as

had been the potentials of motor nerve. Thfe bit of history is discussed elsewhere in this book (pp. 420-423).

PHYSIOLOGY OF SENSATION66

We must, however, note hero also the fact that Forbes, Miller
and O’Connor in 1927 observed in the medulla aelion potentials
synclironous witli tlie clacks of a waldiman’s rattle or the Inirr ofa card held against a moving toothed wheel— obscivcd them up
to frequencies of two hundred per sc'coiid. Faster sequences theirstring galvanometer could not record.
2.

All-or-wne and refractory phase. Before 1912 tho fact that

sensations vary in intensity made no trouble for psychologists orphysiologists,

A «is nervosa would presumably not bo fixed inamount; the greater the vis, the stronger the sensation. A wave ofnegativity might have any amplitude. Nor did the discovery of

the all-or-none principle for motor fibers suggest at once that
there ought not to be continuously graded strengths of sensation
if the sensory fiber can give only its all or iiotliing.

Forbes and Gregg in 1915 were lire first to empha.size this difficulty. Oblaining continuously graded rcllcx responses irom a con-tinuously incrca.sing strength ol stimulus, liny asked

how thecontinuity ol the stimulus can be represented in lh(> relk'x, if theafforont link in the chain can vary only by discrele slejjs sus each

new fiber enters tho field to add its all to the total exeilaliou. They
answered their own question witli the frequency Iheoiy, whicli

wo must consider presently.
Ti'oland also saw this problom for vision in 1920, when he un-dertook to show how the facts of physiological optics are not necessarily inconsistent with the application of tlie nll-or-aonc princi-

ple to the optic fibers. This mritter was not, however, settled until
the researches of Adrian (1926-1929) .showed that a continuous
stimulation of a sensory organ at a fixed intensity gives rise to aseries of impulses which are all of the same magnitude.
If further

evidence than Adrian’s wore needed, tho history oftheory of hearing furnished it. In 1928 the present author suggested that the all-or-none law might mean tliat the pitch of tones

depends upon the frequency of neural excitations and the loudness upon the number of fibei-s excited, but Forbes, Miller andO’Connor at once objected (1927) that the refractory period, apparently being no shorter in auditory fibers tlian in other nerves,

would not permit the passage of the higher audible frequencies.

They were right. The auditory “volley thcoiy” of Wever and Brayin 1930 presumed the all-or-none law and normal refractoriness,and finally Derbyshire in 1935 got the most direct evidence. He

INTENSITY OF SENSATION

67

deteimined the maximal potential that can be had from theauditory nerve of different frequencies of tonal excitation, findingthat the maximal potential obtainable is constant for frequencies

below 800 c.p.s., a rate at which &e refractory period permits every
fiber to respond to every wave of the stimulus. At rates too fast

for the refractory period ( e.g., 1000-1500 c.p.s. ) a fiber can respond

only to every other wave and the maximal potential is, therefore,
cut in half: only half the fibers respond to every wave. When therate is more than three times the refractory period (e.g., at 2000
c.p.s.)

the maximal potential

iscut to one-third. (See Fig. 86,

p.424.)
3.

Sensory intensity. It has turned out that sensory intensity de-pends upon the number of afferent fibers excited or upon the fre-quency of impulses in them or upon both factors working together—thatis to say, sensory intensity is a function of the total excitation

within the fibers that contribute to the sensation during some
limited period of time, Both the successive impulses and the im-pulses concurrent in different fibers may be summated into a single
potential in the apparatus tlrat measures potentials; and they must,

moreover, be similarly integrated in the organism whenever the
total excitation determines eitlrer the strength of a reflex or the ob-served magnitude of a sensation. The question is: how did wo cometo accept this duplex theory of sensory intensity?

The theory that intensity of response results from the multiplication of innervated fibers
reflexes.

grew up in the investigations of the

A shonger stimulus excites more nerve fibers, which inturn excite more muscle fibers, resulting in a stronger contractionof the muscle. Stellar brightness, moreover, is measured by stellar

magnitude: the brighter stars look brighter (sensory intensity)and larger ( more fibers innervated). Strong stimuh are ‘irradiated’;
they spread on tho skin, in the retina, and, according to both

Helmholtz and recent investigators, in the organ of Corti in the
inner ear. There was plenty of ground for belief that sensory intensity depends upon multiplicity of fibers innervated.

But why

did magnitude of sensation seem then to be a continuous functionof intensity of stimulus?

Why was it not quanta!, showing step-

wise increase for a continuously increasing stimulus, like the reflexes under certain conditions? (Cf. pp. 38, 59-61.)

Forbes and Gregg found the answer to this question in the fre-quency theory of intensity. They argued in 1915 that a continu-

—
PHYSIOLOGY OF SENSATION

68

ous stimulus of constant sti'ength, having rendered the nerve fibers
refractoiy by discharging them once under the all-or-nonc principle, would then discharge them again after the refractory period

had passed, and that, witli tlie continuation of tliis cycle, the stimulus would establish a frequency of impulses whose rate would bedetermined by the duration of die refractoiy period. A stronger
stimulus thus would yield a faster frequency, because then therefractory period, lying within the interval of relative refractoriness, would be less. (Fig. 4, p. 60.) The stronger the stimulus, theshorter the relative refractory period; hence the more rapid thefrequency.

This plausible hypothesis was amply confirmed by Adrian’s researches (1926-1929). He found that a constant strength of stim-

ulus always gives rise to a series of impulses, whose frequency
increases with the strength of the stimulation. He also found thatthe frequency for a constant stimulus diminishes rapidly as thestimulation persists, and he explained this plicmomeuon as evi-

dence of adaptation in the sense-organ: tho receptors in use rapidly
lose their efifectiveness; thus the resultant frequeiiuy diminishes
too.

All told the 1920’s

were a profitable decade for increase ofknowledge about afferent conduction. In 1920 tlierc was reallymore than a belief in parsimony; nature, it seemed, would not
make sensory nerves different from motor, nor give them different refractory periods. The biochemistry of die two kinds oflittlenerve, moreover, appeared to be the same. In 1930 psycliophysi-

ology had taken a long step toward Fechner’s goal, the substitution of 'inner for ‘outer’ psychophysics. Sciendfle knowledge ofsensory stimulation has always thus progressed from without inwe have learned first of the nature of the external stimulus; next
have come fact and theory about the processes in the sense-organ;

now we know something about afferent conduction.

Specific Nerve Energies
In order that we may understand the thought which lies beneadi Johannes kliiller’s doctrine of specific nerve energies, let us
try to comprehend the epistemological principle involved. Not all

the men who discussed diis problem understood it.

SPECIFIC NERVE ENERGIES

69

The classical view of the mind is that there exists within thebrain a sentient being, a Sensorium, that seeks knowledge of theexternal world and can never come closer to it than the direct contact provided by the nerves, Suppose I was permanently impris-

oned and wanted to know what the Venus de Milo looks like.

How could I find out? (a) I might have the statue itself brought
to me for inspection, (b) If that were impossible, I could havecopies, pictures, images, eidola of it brought to me. (c) Failingthem, I could acquire a verbal description of it. The &st plan is
impossible for the mind: it cannot get at the objects themselves.

Thus the ancients chose the second principle: the objects give off
images of themselves, which are carried to the mind by the nerves(pp. 4f.). In other words, representation of the objects to themind is in kind. If, however, there are no copies of the objects
or if the neives cannot carry them, it is still possible to have asymbolic representation in wliich the data furnished the mind do
not resemble die object—any more flian the words of a description themselves

resemble the object which they describe. Suchsymbols must have to the object a /ked functional relation, if fromthem the mind can loam to infer the nature of the object to which
they refer or are related. The specific nerve energies are just such

symboho data. Having a fixed relation to their adequate stimuli,
they imply die stimuli, thus providing information about diem.

The distinction here lies between direct representation and functional implication.

Put in this manner diere is not enough difference between the

two theories for them always to remain distinct. It is no wonder,
then, that the representative theory (eidola) could persist so longthat the sophisticated supporters of the theory of functional ade-quacy had repeatedly, throughout two centuries, to win the battle
against it over and over again.

For instance, John Locke’s dieory of the secondary qualities(1690) was a clear enough argument against the image theory.
The objects have “powers” to produce these qualities, yet die

powers in the objects in no way resemble the secondary qualities
in the mind. The power of an object to produce the quality red does
not, he said, look red,

A tone is not a vibration, even though there

never was a tone without a vibration to cause it. Always somereliable causal connection intervenes, changing the nature of thePHYSIOLOGY OF SENSATION

70

event and making sure that a tonal sensation implies, when knowl-edge is adequate, the prior vibration widiout the tone’s ever being
itself a copy of a vibration.

Thus it comes about that the functional relations which makecorrect perception possible lie, in part, in the properties of thenerves. The mind, hearing a sound, is perceiving that the auditory

nerve is excited and tluis knows that some object, capable of vsciting that nerve, is without. Not all objects are sonorous, To heara sound is to perceive the presence of such an object as has thepower of stimulating the ear,This logic was quite clear to the thoughtful men at the begin-ning of the nineteenth centmy who reasoned about those matters,

although the image theory of perception still pervaded common
sense. Thomas Young, convinced in 1801 that there Is an infinitudeof perceivable colors and that they can all be composed of mixhiresof three primaries, suggested that llicro must, tliorelore, he Ihvee

kinds of optic nerve filrors ( pp. 110 f. ).

A sensation of purple would

mean that the rod and blue nerves were excited and tlie yc'llow
not at all; a while that all three nerve.s wc'ro ('(pially (‘xeiU’d. He

did not picture theMind in the brain, weigblng Ibe relative

amounts of the throe exoilalionsj yet lliat wa.s the iinjrlicalion of
his thought.

Charles Bell in 1811 anticipated Johannes Mtiller’s theory inconsiderable detail, pointing out that one perceives sensory quality according to the nerve lhat is excited, not according lo the ob-ject that excites. If a pressure on the cyo-ball stimnlalcs the retina,
light is perceived, not pressure. Electricity may excite many senses,

yet we never perceive electricity as such, but as light or taste or
touch, depending upon what nerve is excited by it. Bell’s argu-

ment was brief but explicit; it is possible lo cite from him sentences that explicate every one of Muller’s more imporlant laws.
Bell, however, enunciated no formal doctrine, It was, nevertheless,obvious to him “that neither bodies nor tire images of bodies enter
the brain."

The image theory was, however, so well grounded in common
thought that Johannes Miiller was constrained to combat it withhis formal theory of “specific sense energies" (1826), or “specificenergies of nerves" (1838). He laid down ton laws with elaborate
illustration and discussion, but

we must content omselves with aMOLLER on specific energies

71

simplp rcslalomcnl of the five most important principles which
his laws include. Tlicso arc they.

(1) Tire Sensorium is directly aware of the states of the sensory
nerves, not of lire external objects.

How could it perceive objects

directly, when only the energies of the nerves come to the brain?

(2) There are five of tliese spedfle energies, one for each of thefive senses. Miiller did not go even so far as Young who thoughtdrat there might be three different kinds of optic nerve fibers.

When he called the nervous essential an energy, he must havebeen influenced by such doctrines as the vis viva and the vis
nervosa in his choice; yet he remarked in one place that qudity

would do as an alternative term for energy.
(3) The same stimulus acting on different nerves gives rise todifferent qualities; different stimuli acting on the same nerve giverise to the same quality. It is the nerve, not the stimulating object,that matters. Muller’s text is replete with instances too well known
toneed repetition here. In 1888, it was possible to argite thatelectricity is a stimulus to all five of the senses, arousing in eachits

own peculiar quality.
(4) The Sensor-ium gains correct information about external ob-

jects, because, in gonoral, only particular objects excite particular

ticrves,This is the doctrine of what Sherrington later called theadcqmle slimnhs. IlaUcr actually had the idea in 1752, when hesuggo,stod that the seeming insensitivity of the internal organs is

duo to tiro fact tlrat their manipulation is an irrappropriate or unnatural stimulus. Muller spoke of the specific irritability of theorgatrs of sense and of the “adaptation” of the stimulus to the sense-

organ, He also said that the sense-organ and its proper stimulus
are “homogeneous”— a lem which seems, however, to imply thesimilarity implicit in the old image theory which Miiller was fighting,Bering named the effective thermal stimulus the “adequate

temperature" in 1880, leading Sherrington to attempt a definition
oj the “adequate stimulus” to thermal sensation in 1900. In 1906

Sherrington gave this term adequate formal status: “the main function of a receptor is therefore to lower the threshold of excitabilityof the [reflexl arc for one kind of stimulus, and to heighten it foi
all others.” Later others began to speak,somewhat ambiguouslyof “inadequate stimuli,” meaning stimuli which, being only ad
venlitiously adequate, were unnatural or inappropriate, like a pres

PHYSIOLOGY OF SENSATION

72

sure on the eye in arousing color, or heal on a cold spot arousing
cold paradoxically, Tlie principle was clear in Miiller, though thewords have changed.
Miiller had, of course, to stress the specific irritability of sense-

organs in order to show why perception is usually reliable. The oldtheory had explained this reliability by the similarity of the image
to its object. Muller substituted functional adequacy. The specificenergy of the optic nerve means light to the Sensorium becausethat nerve is specifically irritable by light. It is the exceptions thatprove this rule: a less weU-adapted stimulus nevertheless produces
the quality proper to the nerve if it succeeds in exciting die nerve
at all.

(5) Finally, MiiUer held that the locus of the specificity lies
either in the central portion of the nerve or in its termination in thebrain, It cannot lie in the peripheral portion, because direct stimulation of the nervo beyond the sense-organ gives rise to its poailiar
quality. Muller’s critics from Lotze, who was one of the first, all theway down into the twentieth century have forgotten this proviiio.

They have argued that sensory nerves nro all alike, that there is,therefore,

no evidence for a difference in thoir energies, forget-ting that sensory nerves, even though their impulses may be identical,

are aU different inasmuch <as they end in different places. It

was much too early for Miiller to have espoused the docirino of
sensory centers, and only natural for him to speoulnlo about specificsensory oires naroosac. He left open, nevertheless, this possibility
that the specificity is, after aU, the place where the nerve ends, or,as we think now, the connections that it makes there.

Of Muller’s doctrine there was criticism aplenty, criticism which
turned mostly upon the point that the nerves are passive conductors and all alike. Mviller’s choice of a name for his theory was
responsible for this objection. It was not likely that the sophisticates would object to his underlying principle, which, as we haveseen, they accepted even before he built it into a formal doctrine.

Nor did they want to go back to the image theory. Instead they
accepted the main thesis and extended its use.

They extended it to the qualities within each sense-department.
As we have just observed, Thomas Young had already madethat application when he suggested three kinds of nerves for thethree primary colors. Natanson in 1844 took up the question fornally. arguing that every neural organ must have a function andEXTENSION OF SPECIFIC ENERGIES

73

every function an organ, He thought there might be three specificenergies for touch, three for taste, three (of course) for vision,and an indeterminate niunber for smell. He made no proposal
about hearing, for the tonal series does not appear to be a mixtureof a few primaries, and he lacked Helmholtz’s courage to suggest
several tliousand specific auditory energies. A. W. Volkinann, laterin the same year, criticized Midler—somewhat paradoxically—on

the ground that the theory would require, not merely five specificenergies, but one for every sense-quality, and then went on to saythat surely every nerve

must have its specific excitability, that

diore must, therefore, be separate nerves for pressure, temperature, tickle,

every color, every taste. In a way he was ri^t in

criticizing Muller: specific energy implies a difference in content

of the nerves, whereas specific excitability implies only a different

functional relation. Volkmann was accepting what Muller called
specific Mtability, not specific ‘energy.’

Helmholtz seems to have taken this extension of the theory for
granted (p, 199). He praised Miiller, said that the theory was forpsyclrology as important as the theory of conservation of energy
for physios. Indeed, it was the only theory of sensory quality that

there had been— or that there is now, if one thinb only of the basic
principle. In 1852, when he first adopted Thomas Young’s tlieoryof color, Helmholtz posited three specific visual energies. In 1863,

when he first put forth his famous flreoty of hearing, he assumed
the existence of enough thousands of specific energies to accountfor all the discriminably different tones.

One can see here why

was both criticized and accepted. To posit a thousand
different energies for a single sense seemed extravagant, if theories
should be parsimonious and if the waves of negativity in the

Miillernerves appeared all to be alike; yet to posit a thousand specificirritabilities

was hardly to do more than to describe Ohm’s lawof tonal analysis.

A thousand fibers, must, moreover, have a thou-sand different terminations. The distinctions here are slight. Lotze

and Volkmann saw a difference; MiiUer and Helmholtz did not.
Helmholtz did not even show that he knew he was extending Miiller’s theory until he added a paragraph about it in the posthumous

second edition of his Optik in 1898.

The effect of the theory was tremendous. Thus extended, it indicated that there must be spatial differentiation of qualities inthe sense-organ, that theories of sensation must show how ele-.

PHYSIOLOGY OF SENSATION

74

mentaiy sense-qualities are got ontQ diEoient aflereut nerve fibers.
Hering’s theory of color vision thus required six specific energies,

one each for black, white, blue, yellow, green and red ( pp, 2()iS 1. )The theory of specific energies lay back of the search lor the final
elementary qualities of taste (pp. 450, 453 f.), It led dircclly to thesearch for spatial difierentiation of fire tactual qualities and thediscovery of the waitn, cold, pressure and pain spots (pp, 4G7469). Even where the dieory could not be applied, its terms wereused; a chapter on smell wmdd end with a discussion of the prob-

able number of olfactory specific energies.

The theory also led, in connection with other discoveries, to
had loft

the localization of sensory centers in the brain. Muller

open the matter as to whether the specificity might not lie in theterminations of the nerves in the brain. After 1870 the advancesin the knowledge of brain loeah'zalions

made it appear that theessential condition of sensory qualities

might eonsi.st ol the e.x-

istenoe of specific sensory centers—al least for the five senses, since

no one ever' proposed the separate exislmiei’ ol red, green andviolet centers. It is not possible, however, tot'lili’i'anb('re iiilo

adequate account of the history ol brain loeali'/allon, and Indeed
die localization of sensory centers has thus lar belpi'il irsycliology

very litde.

We may, nevorthele.ss, sketch die iinporlanl ivi'iits.

It was, of course,

no now idea of lh(> nim'li'eiilh et'ntiny thatevery bodily organ should have a lunclion and eviny inenUilfaculty a bodily seat. Analomy liad invenloiied tbi' organ.s,andfaculty psychology—notably Thomas Reid and the Scollusb .School—the faculties. About 1800, it was, that Gall, presently assisted by
Spurzheim, created phrenology by tiying to find scats lor thefaculties. Gall was an excellent brain anatomist, Ilis Amimnia etphysiologie

du systdme nenetix en gdndmlo, ct du ceiveau en

partietdier,avec observations sur k posslbllitd da rccomiaUiv

nmdes de I'hommo et desanimaux par la configuration de lews tdtes appeared in 1810-1819.
plusieurs dispositions intellecltieUes el

The public fiked dris doctrine that the faculties and propensitiesof men should show in ‘bumps’ on die surfaces of theu- skulls, but
the Church got the government to stop Gall’s lectures in Vienna in
1802 and, when he shifted the scene of his activities to Paris, the—

Acad&nie des Sciences

in a report signed by

Cuvier but insti-

gated perhaps by Napoleon—refused election to Gall.
Flourens, a prot4g6 of Cuvier’s, was a pioneer in die method olLOCALIZATION OF CEREBML FUNCTION

75

ablation for lire study of the functions of the brain.

( See also pp.
538 f. for his work on the semicircular canals.) He interpreted his

experiments, published in 1824-1825, as signifying that localization is limited. Every part of tlie brain has its specific function yet
acts as a whole in respect of this function, just as the total brain
also acts as a whole. All the perceptions, for instance, occupy, heasserted, tiresame seat in the brain concurrently. We shall see

presently, in connectfon with the work of others, how he could

come to such a conclusion. Flourens fought phrenology, and theesteem in which scientists held him, added to the disesteem they

had for Gall, helped to delay for a long time any assured bchef inexact localization of cerebral function.

In 1881 Broca, though anticipated by two lesser men, discovered
the speech center. At any rate, he discovered degeneration of tissue
in the tim'd frontal convolution of thei£t cerebral hemisphere of apatient who for thirty years hadbecnl

Ifisjrcak, although his

vocimotor organs were normal. Win

b'e to supple-

ment this case with others, the pen

aing awayfrom Flourens, although hardly low
Then, in 1870, Fritsch and Ilitzig f
stimulation of tv limited region of t

get specific movcinont.s' of dillcreu'
for five groups. Strong current spretweak determined the position of nr
the cortex produced, with eleclrica
all,This experiment started physioformotor and sensory centers, ayet.

Just as it had been more diffleui

duction than about motor, so nc
sensory centers tlian the motor. Vi

cannot often be combined. Ther
gators,but the pioneers in thisGoltz, whose papers date from 18'
izations did not always agree, wl

Flourens, held that specificity olized.

The position of the visual cen
Fovrier found that monkeys, wit'

subject to abnormal eye-movemi

PHYSIOLOGY OF SENSATION

76

eye on the side oppasite to the side of the iiblation. Munk sliowedthat the removal of an occipital lobe does not entirely blind eithereye,

but produces hemianopia,

vision in each eye, Goltz
right.

a blindness of half the field of

doubted these facts, but Munk was

Hearing they localized in ihe temporal lobe, though lesscertainly.

The somesthetic sensations wore placed in the post-

central region of the cortex. About the centers for taste and smell

there was considerable uncertainty. It was altogether a confusing

period with much outspoken disagreement.

From the point of view of the present we can see how there
had to be disagreement. Here are five reasons why reliable localizations were—and are—hard to secure, (a)The stimulation, asHitzig had noted, tends to spread. Luciani’s maps in the earlydays showed huge centers—with the midregions, nevertliclcss,

most effective. ( b ) Spec%.Iocalizalions lend to be instable. Other
conditions may shift tl**mporaiily. (c) Localization becomes

more exact and^tiro higher neural levels

zation) ir

itioiiary scale. Hence il is diffieull toargue\otber, orn>'or ctpiiixiioulialily is eoiiiinmi. Il is(euee))hali-from lower verleljmU'.s to!suc tlie animal can get along with*n after ablation is al.so common, ins

arc not final.

ional shock

Some of Ihe iuilial

and not to the loss ofacts of reslitutlou of funollon after

m thefirst,

but some, of tire otherr gradually. It is

no wonder, then,the early experimonts,'itb a swing hack toward Flourens

7 .)and Lashley, Franz’s student

ariable,how temporary, how in-metion may be. In 1929 Lashley

and Franz’s work under the priniss action. EquipotenHalUy

means

good as any other in contributing
gent’ action.

Mass action means

ribute together and that the loss

iency proportionately to the loss,,

Hunter, however, in 1930 sug-r

be merely vicarious function.

MODERN AFFERENT SPECIFICmES
that ‘intelligent’ activity, at least,77

may be possible by a great

variety of means, and -that the removal of one means leaves theothers, and thus the function, intact, Lashley, on tire other hand,

never denied some specificity. Pattern vision in Ihe rat he foundto depend absolutely on the preservation of a particular occipitalregion, a region specific for the visual perception of shape, yetequipotential with others in its contribution to ‘intelligence.’ In

the rat, moreover, it turned out that discrimination of brightness

does not require the cortex at all—a finding which cannot be extended, however, to man.
Certainly it will he a long time before the final word on the
cerebral localization of sensory function has been said.

We know

as the results of many experimental ablations and clinical observations that there is a visual cortex in the occipital lobes, essential

to any kind of vision in man, that tlrere is an auditory region in thetemporal lobes, that the post-central portion of the parietal lobes
plays an important, if not essential, role in someslhetio perception, that smell involves the olfactory projection.
Miiller’s

Of Johannes

two hypotheses—the one that the specificity might lie

in the central portion of the nerve, the other tliat it might

localized at the nerve’s termination in thebebrain—the latter ismore nearly correct.

The nerves themselves are now known to be passive conductors
in which all impulses are alike—or nearly alike. Thus far only one

difference has been found among afferent impulses, Gasser anf

Erlanger (1924r-1930) discovered that somatic nerves may haat least thi-ee kinds of fibers, fibers of different sizes in which

impulse travels fastest in the largest, slowest in the smallest. Adria(

1931 ) added to this distinction the argument that the slow, smal

fibers, for the most part, mediate pain. This discovery came, how-ever, long after it had been seen that the important kind of specificity lies not in the nature of the impulse, after all, but in the loou;of the terminus and in the connections that a fiber makes incentral nervous system. Miiller could have imagined the Senso*

recognizing a stimulus as painful because fte impulse
slowly on a small nerve. Today we ask merely: what
neural events does such an impulse set up?

Thus Johannes Midler’s second hypothesis is goi"'
about twenty years after his first Specificity seen
not in the nerves, nor even in their terminations, bu•^

PHYSIOLOGY OF SENSATION

78

active pattern. Centers arc already a little passA Tlie positivisls

claim

to sensationis,so far as it is knowable in inlvospection,

discrimination or differential response.

A light differs from a sound,they say, because it is possible for the organism to discriminate
the one from the other, to react in one way to light and in anotherto sound. This statement means that the reacting system ‘knows’

the difference between impulses that have come along the optic

nerve and those that have entered by way of the auditory nerve.
Muller’s Sensorium is reaction—for the positivist. The phenomenologist can still get along, it is true, with centers whose activationis thephysiological substrate of the sensation; but the positivist

needs, not centers, but tracts. The impulses, not being caught in a
cerebral pool, are but photographed as they pass. The positivist,
therefore, gets

some comfort out of the difflailty of localizing

centers, because what he needs are routes, not stations.

A routecannot be marked on a map witli a push-pin. It can, indeed, be
destroyed by being cut at some particular place, but ihen in manycases there turn out to be alternative routes; ablation does not,then, completely block the traffic but only hinders it by recjuiriiig

a detour. (But aide infra, pp. 78-83.)

Projection
The receptor-fields of the .sense-organs arc ‘projected’ upon themtral nervous system in the sense drat the afferent fibers lead to’central system. Indirectly by way of synaptic connuoUous in
levtiie tracts of all five senses establish in man connection withe cerebral cortex, although tiicy also
.t subcortical ‘reflex’ levels

make odior connections

which do not involve Iho cortex. Thus

leural anatomy has come to support Johannes Muller’s 1110017 of

spedflc nerve energies, which eventually became, as we have justeen, a projection theory of sensory quality. Sight is not hearing"ause the optic fibers are projected upon the occipital lobes andluditory upon the temporal lobes. If you could cross-couiioot
otic and auditory nerves, you could,'

du Bois-Reymond im-

tones and hear colors.

'eruhow easy it was for Helmholtz and the otliers totheory of specificities from the differentiation of
to the differentiation of1,

the qualities within eachdie theorists accepted a principle of parsimony.

SENSORY PROJECTION

79

They did not suppose that there are 300,000 specific energies forcolors, more or less, hut,by appealing to Newton’s law of color

mixture, assumed that there may he three specific visual energies,

capable of 300,000 specific combinations. Taste and cutaneous
sensibilily

were got down to four primary qualities each, andsmell, it now seems, might perhaps have as few as six.

A thousand

energies for hearing constitute simply the unavoidable extravagant

exception to die rule of parsimony.

We might expect, therefore,that the extension of Muller’s doctrine to qualities would have led
toan extension of the parallel theory for the brain. The sense-

physiologist might have sought cortical centers for red, green,
violet, sweet, sour, salt, bitter, warm, cold, pressure, pain, fragrant,

ethereal, resinous, spicy, putrid and burnt— eighteen centers plus
some more for hearing. They did not. Why?

They did not seek to establish a projection theoiy for theseeighteen and more primary qualities because the qualities belonged, at least in the cases of vision and touch, to spatial senses,
for which projection had already been preempted as the theory ofextension, of the Ortsinn. It is strange that there has been so little

recognition of this potential conflict that arises from the use of

the principle of projection to account for qualitative dillerencein the large and extensitive dillerence in the small.

In vision spatial differentiation in projection had long been recognized as the basis of spatial perception. The anatomy of the
optic chiasma was known even to Galen (ca. 175 a.d.)

who ex-plained the singleness of binocular vision by assuming that someof the optic fibers from each eye cross at the chiasma and joincorresponding fibers from the other eye. The discovery of thehoropter(the locus in space of points seen singly in binocularby Aguilonius in 1813 certainly supported some suchview, and Newton in 1717 assumed that half the fibers cross atvision)the chiasma to join the corresponding fibers from the other eyeeither at the chiasma or at the brain. Wollaston in 1824 observed

hemianopia in himself; half the field of his vision disappeared when

he was greatly fatigued, indicating that Newton’s notion of visualprojection was correct, that the fibers from tbe left halves of both
retinas lead to ihe left half of the brain,

and conversely. Thus,

when Muller came to the problem of vision in 1826, he had little
choice about the matter. His nativism, furthermore, also led him toassume that spatial difference on the retina must mean spatial

PHYSIOLOGY OF SENSATION

80

difference in ffie Sensorium. It is true that ho might have envisaged

three superimposed systems of fibers, such as Thomas Young musthave had in mind, but Muller did not. Tlie weight of the Zeitgeist

was against him. (See pp. 234-236.)
The projection of optic fibers was also implicit in the conceptof the retinal image. Kepler, arguing in 1804 that the crystalline
lens is not the visual percipient organ but a true lens which focusesan Inverted image on the retina, was fui-fliering visual theory bygetting the image into the eye, onto the retina and thus one stepnearer the Sensorium. That theory would have been no advance

had it not also been supposed that the spatial relations would bepreserved by projection upon the Sensorium. Thus visual projection was alreadygood doctrine in the early nineteenth century,even though Flourens’ ideas were against it. (Sec pp. 226-228.)
After Muller had first pul forth the theory of specific sense energies,

Weber entered the field with his proposals about the Ortsiim

in 1834 and 1846.

He had invented tiro compass test to measure thecapacity of a subject for tiro discriminatiou of two udjucout simul-

taneous touches. He pictured the skin as divided up iulo “.s('nsory
circles,” such tliat the stimulation of two circles next bul one would

give rise to tiiie perception of duality. That conception implied
projection for the skin. In 1852
circlesWoW oven suggested thattlio

may not be ch'cular, that on tire forearm they would be

elliptical because there disaiminaiion is finer in tiro Irau.svcrsc di-rection than it is parallel to the axis of the arm. (See pp. 475-477;
also Fig. 79.)
It was in1871 that Jrdius Bernstein, having especial regard to

die theory of the sensory circles, took all tliese assumptions andimplications and made them into an explicit projection theory. His
figure, often

reproduced in modified form, is shown in Fig. 6.

There aa is some sensory surface, like the skin or the rethia. It isprojected by the nerve fibers upon the brain centers at the line

gg(ganglion cells). If the point at e and the cell at o are stimulated,
the intensity of excitationismeasured in the diagram by theheight of the ordinate cn. This excitation is, however, “irradiated”;
it spreads from the center c, diminishing in intensitywith the re-moteness of the irradiation, as shown by the curve of excitation.
Finally, it is reduced to a threshold value cim> or Cftn,, beyond

which it is not effective. The radius coj=

cce is the radius of the“irradiation circle,’’ a drcle of dispersion which in the brain re-SENSORY PROJECTION
senibles in funcUon

81

and nature the “sensory olrdes" at the pe-riphery. Bernstein also drew the diagrams for dual stimulation;

the case where two stimulations close together summate, as they
are known to do in vision and were later found to do in touch,Fra, 6. Fiiojection

and iBHAraATioN! Bebnstbm (1871)

StlmuUitum ol e excites tlic gmgiioii-cell c, pioducing excitation of inIcnbity on, The cuive shows the intensity of excitation iiiadiated about c
as iai as Ci=

and Ci, where the excitation fails below the thiesdiold value
Projection is shown

ami = c^n,. Badius of uradiation circle = cc, = coi.
by thepoint-to-point

coirespondenoe of peripheral

field,

aa,

witii

the

ganglion field, gg, e being projected upon c, e, upon Ci. si upon Ci.

and the case where the stimulations, being somewhat more re-mote from each other, produce a total excitation which has twomodes with a ‘saddle’ between them. This latter situation fits the‘dumb-bell’ case that Weber and otliers after him found as inter-mediate between the perception of one tactual impression and two
separated impressions. Altogether the theory was convincing in

1871 and remains plausible today after seventy years.
It cannot be said, in tact, that

we have advanced much beyond

Bernstein. It is no longer necessary to assume sensory drcles atthe periphery or irradiation at the center, for it is dear that all

stimulation spreads in the peripheral organ, much or little accord-

PHYSIOLOGY OF SENSATION82

ing to its degree. In vision the spread is partly optical dispersion

and partly retinal and neural spread; the brightest stars have tire
greatest magnitudes. On the skin, the dispersion comes about by

way of pressure gradients or thermal gradients. In the hmer ear,a loud tone affects more of the organ of Corti dian does a weaktone.

Thus central irradiation may be given up; but projection

stands.

Projection is, of course, in this sense one-to-one. The receptor
field

and the cortical field are held to be isomorphic, that is tosay, the spatial orders at the periphery are supposed to be recon-

stituted topologically in the brain—not the exact shapes, but theorders. (On the nature of isomorphism, see the next section.)

Isomorphic projection is implicit in the notion that the singleness of binocular vision arises from tho community of projectionof identical points of the two retinas ( pp. 226 f ) It lies back of any.

.

attempt to explain stereoscopic vision in tenns of small retinal
disparities (pp. 285 f.). It gives meaning to the fact that injury to

the visual cortex produces a scotoma (blind area) in the ficUl ofvision, and that larger lesions produce loi'ger sooiomalu. If it canever be shown that the shape of tho lesion lias a dollnile relation
to die shape of the scotoma, then the 1110017 of visual projcclion

would be finally established.
Projection also furnishes a satisfactory explanation of tho factsof the cutaneous two-point limen (as Bernstein .showed)

and ofthe error of localization, and it makes these two measurements
consistent with each other (pp. 484 f.). It provides a sensible

meaning for the abnormal errors of tactual localization which
occur after injuiy to a cutaneous nerve (p. 475). It explains also—that large

the fact—so obvious as almost never to be mentioned

errors of localization are less frequent than small—for, if projec-tion did not approximately maintain the spatial order, why should

not two near points at the periphery often be more readily discriminated than two remote points, since, unless projectionisisomorphic, remote points at the periphery might be projected

upon adjacent points in the brain?
In hearing, as the place-resonance theory becomes better established ( at least for high tones ) , it would seem that position in thesense-organ is correlated with perceived pitch. Are the pitches
projected? Culler has presented direct evidence of their projection at an immediately subcortical level, and there is considerable

.

ISOMOBPHISM

83

Why else does one hear a single pitch binaurally

indirect evidence.

when the two ears show a difference of pitch in monaural stimulation? There must be community of binaural projection to explainthat fact.

Why else does the localization of a binaural tone shift

when the intensitive difference or the phase difference between
the two ears is changed (pp. 387-391)? Why does one hear a beating intermediate pitch (the intertone) between the pitches properto

two low tones which are adjacent in pitch and generate thebeats? The fibers from each ear pass to both cerebral hemispheresand it looks as if the spatial orders in the organ of Corti were
preserved in the brain.

Some degreeof isomorphic projection

is

also

required by

Xohler’s theory of the isomorphic relation between perception andthe patterns of excitation in the brain (see the next section). If thepattern of perception, being, in general, correct in spite of all the

exceptions which Gestalt psychology has exhibited, resembles thepattern of stimulation,and if, as Kohler’s theory asserts, it also

resembles the brain pattern, why then the pattern in the brain mustalso resemble the pattern of stimulation.

Brain anatomy— as far as it has gone, and recently it has gone

forward rapidly—supports psychology in most of tiiese matters.

The sensory tracts arc well established. Point-to-point correspondence is accepted for vision, but exact correlation is somewhat disturbed by the fact that axons in the cortex arborize at their terminations. The problem here is no greater, however, than the problem

created by the spread of excitation in the inner ear where exact
localization is nevertheless taken to be effective ( pp. 408 f ., 480 f. )Perhaps a mechanism will be found by which the spatial relationsof the receptor-field are precisely maintained by intercoimections

or field-forces, even fhou^ the correlation of a particular receptor-

point with a particular cortical point is not permanently fixed.

A spatial neural transposition, analogous to the transposition of
pitdies in a melody, might be possible, with the peripheral relations maintained in the brain even when aU the exact connections

had been altered.

Isomorphism
One system is said to be isomorphic with another in respect of
their spatial relations if every point in the one corresponds to apoint in the other and the topological relations or spatial ordears

,

PHYSIOLOGY OF SENSATION

84

of the points are die same in the two. If a system of points

ismarked on a iat rubber membrane and the mombniue is thenstretehed tightly over some iraegulat suriace, then the points inthe stretched membrane are isomorpliic with the points in the flat

membrane. As we have just noted, perception and stimulus are
spatially isomorphic in as far as the perceived spatial orders cor-

respond with the spatial orders in the stimulus. Projection ol thestimulus field upon the cortex tends to be isomorphic, at least to

the degree which we have discussed in the preceding section. If

perception and brain field are both isomorphic widi the stimulus
field, they must be isomorphic with each other. It is to this solu-

tion of the mind-body problem that Kohler has applied the term

isomorphism—meaning psychoneural isomorphism. The simplest
test of sucli isomorphism is to see whelbcr adjaccncie.s and inbe-

tweennesses are picserved from one system to the other.
This woid has sometimes been extended to oth(‘r .seiwory attributes than space. There would be temporal jisyehoueural Iso-morphism if the time-ordw of perceived events is the saint’ as tlie
time-order of the neuial events midorlying them, lutensitive iso-morphism would mean that scasory intensity alw.iys eon'espoiuls
with degree of tlie total underlying cxeitatiim.

(^)ualitalive iso-morphism, at which KShler luis hinted, implies that (lillerence insensory quality implies difi'orenco in e.xcitatory quality, as if different kinds of ion-concoutrations in tlie brain could explain thedifllerenoe between yellow and blue or between .sweet and simr—a rather improbable assumption inview of the uiiiiormity ofnervous action.

Psychoneural isomorphism, however, is a special case of psychophysical parallelism and of the mind-body problem in general.
It was believed to

be axiomatic long before the anatomical andphysiological knowledge of projection was sufficient to justify it.

How did psychologists come to hold to this view? Why did it seem
axiomatic to them?

In a way this whole matter goes back to Empedocles, to theimage theory of perception and lo representation in kind pp. 4 f )(If the nervous system were to pass along to the.

Mind an eidolonof the object, then the Mind in the brain could perceive directly

the nature of the object in as far as the eidolon is a correct copy.

Locke’s theory of secondary qualities, Muller’s theory of specificISOMORPHISM

85

nerve energies, substituted functional implication for this representation in kind, yet left ihe Mind to perceive directly the stateof the brain. Even for Miiller’s objectivity the Sensorium was an

intraa'anial homunculus witli discriminatory capacities.

That there should be difficulty about the way in which the immaterial mind perceives materM states is the reason for dualismof mindand body. We need not go back to the origins of the

dualistic conception in Plato, but content ourselves with notingthat Descartes (ca. 1650)

made the belief in an insubstantial

mind axiomatic in psychology. The consequent easy view about
the relation of mind to body, the view that results from such adualism,isinteractimism:

mind affects body and body affects

mind. The instances of both these relations are innumerable, andthe theoiy remains irrefutable as long as there is no exact observational knowledge

about the functioning of the brain. Descartes

was an inleraelionist; so was William James as late as 1890, when
he refused to accept the automaton theory of human conduct andappealed to common sense for the evidence of interaction.
Parallelism, however, entered the field against interactionism.

This theory bogius with Leibnitz and his isolated, non-oommunieating monads. The orderliness of nature in suoli an individualistic

universe comes about, Leibnitz thought, by way of proostabUshedharmonica among the developing monads. If nothing interacts,
then, of course, mind and body would not interact. One would ap-

pear to depend on the other only because the preordained events—in each would harmoniously coincide^like

two clocks which tell

the same time without either being able to affect ffie other.

The first thorough theory of psychophysicalphysiological) parallelism was Hartley’s (1749).

(really psycho-

He seems to have

—Newton’s

come to it by trying to combine Newton with Locke
theoiy drat the transmission of physical impulses

isvibratory(Newton did not always hold to tiie corpuscular theory of light)
and Locke’s theory of association. At any rate Hartley described

mind as formed by associations of ideas which parallel associationsof diminutive neural vibrations in the brain.

For a century after Hartley parallelism and interactionism wereequally plausible views. Theologically minded psy^ologists might
prefer interactionism as leaving more scope for the operation ofa free will. Scientifically minded psychologists might prefer paral-

PHYSIOLOGY OF SENSATION

86

lelism as leaving the paradoxically insubstantial mincl-slull oil at

one side in the picture of self-sufficient physical action

in lirebrain.

In the middle of the nineteenth century, however, the theoryof the conservation of energy came of age. Notions about equiva-

lences of work go all the way back to Archimedes and the lever.

Newton is said to have glimpsed the general theory of conservation
for mechanical action. Joule’s memoir, summarizing the history of

the theory and bringing together his

own contributions on themechanical equivalent of heat, was written, however, only in 1849.

Then, in 1851, William Thomson, later Lord Kelvin, formulated
the law of the conservation of energy and also the second law ofthermodynamics (the law of entropy). For at least two centuries

men had been scheming to devise instnimcnts for the productionof perpetual motion.

These laws put an end to that dream. Al-

though the law of the conservation of energy did, in fact, as-sortthat all motion is perpetual, the law of entropy denied its practicability, showing that the transformatiou of energy is always directed

toward a dissipation in heat and that the universe ought, tlicrofore, eventually to ‘nan down,’ hocoming an inaolivo coustcllatlou

of matter all at the same tcnipcralurc.

These laws, which transformed physical thought, also affectedpsydaology. Because of them it became impossible to think of thetransmission of activity without a transfer of energy. Hume had

defined cause as recurrent concomittance. Now it was necessary
to find an energetic equivalence between acause and its elfect,

or else, if there is a heat loss, to find less, not more, energy in theeffect than there was in the cause.

How was the interactionist tomeasure the energy in the mind, when the body effects a change initor when it moves the body? It was clear, moreover, that thebrain, being material, must be regarded as a closed system; what-ever energy is delivered to it must be given up again in motion orlost in heat. There seemed, indeed, to be no way of breaking sucha system open to introduce within it mental links.

Thus the theory of the conservation of energy told for parallelism and against interaotionism. The action of the nervous system

must be complete in itself, explicable, when all the facts are known,
under the energetic laws. Mental events mi^t parallel its action
but could not cause it or be caused by it, By 1872 this conception

was so well established that Bain could base his Mind and Body

PSYCHOPHYSICAL PARALLELISM

87

upon it, and two years later add a chapter on the matter to Balfour
Stewart’s The Conservation of Energy.
It was natural, then, for the hard-headed, physloalistio, physio-

logical psychologists to accept the limitations of the conservationof energy and to become parallelists. Wundt was a parallelist, as

were G. E. Muller, Kiilpe, and practically all of the pioneers in the‘new’ psychology which sought to be scientific and experimental.

Fechner was

also a parallelist,

but for a difierent reason.

He

wanted to show that the spiritual and material are not different
worlds, but simply different aspects of a single world. The Nachtansicht shows matter, the Tagesansicht mind. Thus Fechner metaphysically was a monist, but epistemologically he was a dualist.
Parallelism could

be accepted by all these philosophically so-phisticated German psycliologists because it did not have to prej-

udice their metaphysics. They could believe in a parallelism eitherof two substances (metaphysical dualism) or of two aspects of thesame substance (metajdiysical monism). Nowadays the Gestalt
psychologists assert only an epistemological dualism, letting themetaphysical problem rest for separate consideration.
That, then, is the atmosphere of conviction in which the explicit

axioms of isomorphism developed. How did they become established?

In 1852 Lotze recognized and discussed this problem. He notedthat sensory series correspond to stimulus series, although thereisno exact proportionality between. He discussed what were to

become later the four basic attributes: quality, intensity, extension and duration. He laid down certain general principles about

mixture or simultaneous stimulation.

Two stimuli of the same

quality acting on the same nerves summate, he said, yielding astronger sensation. Two stimuli of different qualities may or may

not arouse an intermediate quality; colors usually do (red andyellow, though not blue and yellow), tones do not. These differ-ences must depend upon the different ways in which stimuli affect nerves. Qualities from different senses, however, never yield

an intermediate quality, he added, but only a division of attention.

In the next year ( 1853 ) Grassmann, a mathematician, solved the

problem of color complementaries by an application of a priori
logic, Newton had been unable to get perfect grays from the mix-

ture of onlv two colors. Helmholtz had succeeded only with bhie

PHYSIOLOGY OF SENSATION

88

and

yellow.

For most

pairs

of approximately

complemenlai-ycolors they got grays tinged with some hue. Grassmiuiii laid down

the axiom that a sensory series is con'clated with a stimulus series

and that change in one must indicate a change in the other. 'I’lins
he could show that, for every color, there must, within the seriesof nearly complementary colors, lie an exact

compleineiitary

which, mixed with the original color in the right proportions would
give a perfect gray. Heltnholtz accepted this logic and presently,

with improved apparatus, verified

itexperimentally.

(Sec pp.

141 f.)The efiect of Fedmer’s Psychopkysik in 1860 was further- to
establish this correlation of sensory continuities with stimulus
continuities. Psychophysics, as a matter of fact, is little other thanthe determination of critical points in die scales of stimulus as
the conditions ol critical points in tire scales of sensation. Feehners
aspirations, however,went further, for he argued that the lawsof outer psychophysics (sen-salion and stimulus) should be trans-ferred to inner psycliophysics (sensation and In-aiu jn-oim-),

Then Mach wrote in 186.5: “To every p.syehleul tluTc' isn'vespends a physical, and conversely. Lihe psyehieal proee,s.ses eon'c-spond to like physical, unlike to unlike, li a p.syeliii’al process canbe resolved, in a purely paychologicid manner, into a multiplicity
of qualities, o, b, c, then to these there correspond an equal numberof different physical processes, a,y. Particularsof the physicalcorrespond to aU the particulars of llio p.syohic." Similarly lloriiig,
formulating his theory of color vision in 1878 and returning to

Grassmann’s conception of serial relations, wrote: “To two qualities of sensation,

which we designate as white or bright and as

black or dark, there correspond two different qualities of chemical
events in the visual substance; and, to the different relations ofdistinctness or intensity with which these two sensations appear in

the unitary transition between pure white and pure black, or to
the relations in which they appear to be mixed, there corresponddifferent relations of the intensities of thetwo psychophysicalprocesses.” (See also the further discussion of this problem, pp.

206-209.)
It is clear that psychologists were confronted with certain prin-ciples inherent in psychophysical parallelism, principles

which
were axiomatic in that they commanded universal assent. No direct proof was then possible since the physiological proco.ssos in

PSYCHONEURAL ISOMORPHISM

89

the sense-organs and the brain were not yet open to immediate
observation. Thus G. E. Muller, recognizing this situation in 1896,

undertook to clarify

itby laying down

five“psychophysicalaxioms.” The first three, die most important, are as follows;“1.

The ground of every state of consciousness is a material

process, a psychophysical process so-called, to whose occurrence

the presence of the conscious state is joined.”“2.

To an equality, similarity or difference in the constitution ofsensations

.

.

.

there corresponds an equality, similarity or dif-ference in the constitution of the psychophysical process, and conversely.

Moreover, to a greater or lesser similarity of sensations,

there also corresponds respectively a greater or lesser similarityof the psychophysical processes, and conversely.”“3. If thechanges through which a sensation passes have thesame direction, or if the differences which exist between series ofgiven sensations are of like direction, then the changes throughwhich the psychophysical process passes, or the differences of thegiven psychophysical processes, have like direction. Moreover,
if a sensation is variable

in n directions, then tlie psychophysicalprocess lying at the basis of it must also be variable in n directions,and conversely.”

Only by way of such axioms could Hering have formed his color
theory, or could G. E. Muller have added to it the cortical gray.

Hering had no direct evidence about the retina, nor Muller about
the cortex. Yet there was some observational ground for the axioms—the observations of Bell and Johannes MMer that lay back of
the theory of specific nerve energies.

Grassmann, Fechner, Mach, Hering and G. E. Muller were all
analytical in their approaches to this problem.

They dealt withsingle attributive dimensions of sensation and stimulus. It seemedat the time the best way to proceed.

linear series

By limiting sensation to aand specifying the corresponding stimulus-series, it

was possible to control variation in the one and to observe the corresponding variation in the other. Out of such analysis grew thefalse belief that every simple dimension of sensation is correlated

to a simple dimension of the stimulus—^brightness or loudness toenergy, quality to wave-length or frequency.

We Ijnow belter now(see pp. 25 f.). Any attribute of sensation is likely to be a joint
function of several dimensions of the stimulus, yet the simpler correlation of dimension to dimension has persisted for a long time,

90

PHYSIOLOGY OF SENSATION

only because il began thus and seemed lully as iixiomatic as thepsyclioneural relationship itself.

When Kohler participated in the founding oi Gostall psychology(

1920), he made over Muller s axioms in accordance wilh the newunanalytical dynamic concqrtions. It was he, indeed, who applied

the term isomotfhism to this psychoncural relation, he and hiscolleagues who made the concept so important in Gestalt psychol-ogy that it is not always possible in their writings to distinguishbetween the phenomenal field and tire correlated brain field. He
was, nevertheless, explicit. The relationship is one of topologicalorder, not of identity of size or shape. “All experierreed order inspace,” he wrote in 1929, “is a true representation of a correspond-ing order in the underlying dpaniical context of physiologicalprocess.” "All experienced order in time,” moreover, “is a true

representation of the corresponding concrete order in the underlying dynamical context.” Arrcl the law ior phenomenal organization is similar: “to a context, experienced a.s ‘one thing’ belonging

together, there corresponds a dynamical unit or whole in the un-derlying physiological jn'occssra.”

The criticism of psychonciu'al isomorphism has conn* from thephysiologists and lire positivistic psychologists. ’The physiologists

said drat the braiu is, in general, a net-work ol conm'Ctions, not afield where dynamic forces, sudi as the Gestalt psychologists findin perception, can exist. Tire future will decide that point. Even

the physiologists know little as yet about the action of the braiu.

The positivists said tliat a mere statement of correspondence between mind and body is not enough, that they wished to know

how the one affects the other, and that operational analysis of thenature of the available evidence lor isomorphism shows that dre

axioms should be rewritten so as to state relationships between
neural events—between events in the brain and the other physiological events involved in the description of experience. In thiscontention they are expressing a taste in scientific logic, and again
it is the future that will decide whether their preferences will be

fruitful enough to prevail.

NOTES

91

Notes
tary Motions of Animals, 1751, 2 ed.,Nerve Conduction

1763;

For the moctem fads and theoryof nerve conduction, see the modem

Unzer,A.

J.

Medicinisches

Handbuch, 1770; 5 ed., 1794; Eng.
bans., 1851 [n.v.], (vis nervosa).

physiologies, or more specifically. A,

On tlie history of eleotrictty in theForbes, The mechanism of reaction,

18th and early i9th centuries, see A.

A Handbookof General Experimental Psychobey, 1934, 155-203(bibliopaphy of 187 titles); or,more bridy, E. G. Boring, The

Wolf,

Dimensions of Consciousness, 1933, 38-61; also Adrian, Fulton and Lucas, opp. citt. infra.

Galvani,motu

On the animal ^Irits and the vis

atquePhysicalviva of the ancients, seeton,F. Ful-J.

Muscular Contraction and theReflex Control of

Movement, 1926,
1066

of

3-55,

also

lilies;Physblogy of thebibliography

Nervous

System, 1938, historical notes at the
beginnings

chapters,

theofbibliography of 1381

titles;also

F. Fear-ing, Reflex Action, 1930, passim, esp.

35-58,

bibliography

also

of

5

m

A History of Science, Tech-nobgy and Fhlbsophy in the Efghfeendt Century, 1939, 213-273.

On animal electricity, see first L.
De viribus electricitntis in
De Bononlensi

muscnlarl,elArtium Instttuto
Academia
Commentarii,(which is a part of Accad. Sd. Inst.

Scientiarum

Bologna),A.

were mostly inwhich have been brought

letters,

together

in

Bdefe

zur

German bans,
thierische

1900(1792-1795),

in

his

Elektricitdt(against

Gal-vani); Galvanimus und Entdeching

Situbnapparates (1796-1800),
1900 (invention of the battery); seedesUtlos. Less satisfactory is M. Foster,also his letter,

Lectures on

cited

the History of P/iysi-

863-418.

1791,

7,

Volta's contributions

On the electricity ex-by the mete contact of con-abey, 1901, 255-300 (Vesalius to
HaUer; bibliography of 40 titles).

ducting substances of different kinds,

The discussions in Fulton, 1926, and(Voltaic pile, galvanic chain).

Fearing are excellent, and the pres-

Galvani and Volta, see Wolf, op.
e#., 257-287; on Galvani. see F jton,

ent text

is,in comparison,

only abrief abstract. In view of their com-

Phil

For

mere list-about

ing of nine of thebooks

more important

mentioned in the

text;

K.

Les passions de I'ime,
1650; Traite de Vhomme, 1682, orDe homine, 1684; T. Willis, De motu
Descartes,

anlmallum

of

(part

Affectlonem,etc.),

1670; H. Boerhaave, Institu-

tionesmedlcae,

1708;

F.

Glisson,Tractatus de ventrieulo et Intestinis,A.

BorelH,De motu anlmallum, 1680

(succus1677(irritability);ncTOOUs);J.

G.

Swammerdam’s(d.

1680) Vcrsuche, published posthumously in H. Boerhaave’s Biblia

90,

1800,

403-431

On

op. cit, 1926, 34-38.

plete bibliographies, we may content

ourselves here with theTrans.,

Johannes Muller’s
nerve conduction,

Handbuchderopinionssee

Physbbgfe

his

des

Menschen, Bk. Ill, Sect. 1, Chap. 3;
and Sect. 2, introd., 1834 (or Eng.
bans.). The paper which Miilla
showed du Bois-Beymond in 1841
is C. Mattencci, Note sur les pb4nomhnes 41ectriques des animaux,
C.R. Acad. Soi. Paris, 13, 1841, 540 f.
E. du Eois-Reymond began his workin elecbophysiology with Vorlaufiger
Abriss^er Untersuchung tiber
BDgenannten Froscdisbom und ilber
die elekbomotorischen Fiscbe, Ann.
Phys. Chem., 134, 1843, 1-30. His

work

naturae, II, 1738; H. Whytt, An Es-

classical

say on the Vital and Other Involun-

abet thierische Elektricitid, I, 1848;

isUntersuchungenPHYSIOLOGY OF SENSATION
1849; II (2) was published
1860-1884. On du Bois' work, sac
Fulton, op, ctt; 1926, 89-41.
II (I),

On tlie vehcitu of the nerve im-desMuskeltascrn
Ber,

Herzens

zeigen,Ges. Wto., niath.-phys.

siicbs.

CL, 23, 1871, 052-089; K. Lucas,
the gradnllim of uetivity in aOn

H. Helmholtz, Messungenskeletal musele-fibre, J. Physiol., 33,

liber den zeitlichen Verlaul der Zuck-

1005, 125-137; lire ‘all nr none' coii-

pulse, see

ung animaliscber Muskeln und die
Fortpflanzungsgeschwindigkoit

derHeizung in den Nerven, Arch. Anat.
Thysiol,, 1850, 276-304 ( Helmholtz’s
Wissenschaftliche Abhandkmgen, H,
1883, 704^43); Messungen liber
Forfpflanzungsgeschwlndlgkeit

derHeizung in den Nerven, Ibid,, 1852,
199-218 (Wise. Abhl, II, 844-861).
See also E. G. Boring, A History ofExperimentd Psychology, 1929, 4246, for the story ^liow Miillcr andvon Humboldt at first refused to—

traclinn ofamphibian skeletal mus1909, 113-133; E. D.

cle, ibid., 38,

On the conduction of sub-Adrian,normal disturbance in normal nerve,
ibid., 45, 1912, 389-412; Weden.sky

ciple, as of its date, seo Lucas,

Condticiioit of theOn iho mcmhmic ihiwy, seu W.
halbdurchlii.sslgi'f
phijs.

triumphed.

Thermodynumlk dev

Vie

see

Berusteln,

JuliusVaiipflamtingsgesoluoindlglcolt

V.lwm.,

71-82; Jul-

Unlersiichimgeii

521-562;

11.

S.

Lillie,Trimsmisslonof phy.sit)lngit';d Inllm'm'o in proto-

phtsmiu

Physiol. Boos., 2,

Erremngsoorgmg im Noroen- undUusmsysteme, 1871.

rcfcTeuci'.s lliere eliial; Ilia

charakteriache Meckmal der Herzmuskelbewegung, Beitrilge ear Ana-

tomie undCarl Ludwig,

Physialogie als Festgabe

63-88,

72-82, 851.;
F. Gotch and G. J. Burch, The eletyas

two stim-

Phydol, 24, 1899, 410-426;
Gotoh, The submakimal electric re-

uli,

J.

sponse of nerve to a single stimulus,
ibid., 28,
1902, 395-416; E, D.
Adrian and K. Lucas, On the summation of propagated disturbance innerve and musmd, ibid., 44, 1912,

68-124.

On the aJLor-ncme law, see H. P.
Bowdlteh,

Ueber

die

Eigenthiim-liohkeiten der Reizbarkeit welohe dje

1922,

nerve,

1-37, andvvvtmvya model of recovery processes insystems, 1. gen. Phys-3, 1920, 107-143; Pivtoplashiie
Action and Nervous Action, 1923, oriol.,

2 ed., 1032, Chaps. 14 and 15.

Sensory Conduction

On die Eell-Magcndia law of theesp.

trlcal response of nerve toespeclully

irrilidile living

traoaux du laborstoire de M. Morey,
1876,

systems,of transmissivity in passive iron wires

1874, 173-204; E.
Marey, Physiologic expirimentale;
J.
2,

ziir

bioiOi’klrisehen

Striime, Arch. grs. I7ii/.do/., 112, 11102,

der negutloen So/itunnkting iin Ner-

On refractory phase, see II. Kro(with W. Stirling), Das

Z.

.Seheldi’Wiindc,(I,

Beiaslcin,

ias

Eigeasohultcn

F.h'ktrlseheven, 1866; UntarsMo/tungen fiber den

neckerThe

1917.

and persuaded von Humboldt
to present the results to Ihe Aead4mie dcs Sciences, how Ilohnboltzof negaHoifu,

46,

Nmaus Impulse,

Oslwald,

On the nerve impidse as a tuaoe

ibid,,

1913, 384-412. In general, on refractory phase and the all-or-none prin-believe, how du Bois stood by Helm-holtz

to the 'all-or-

inlribition in rcLition

none’ principle in nerve,

spinal nerve roots, see Charles Bell,

Idea

of

a

New Anatomy

of

the

Brain; submitted for the Observations of his Friends, 1811, private
printing of 100 copies; reprinted in;.

Anot, Physiol., 3, 1809, 153-166;

and again with German
Idee

elner

netiantrans.

as

IHrnanatomie,

1911; Franccls Magendie, Experiences sui les fonctlons des lacincs

des nerfs rachidiens, J. Physiol, exp.
1822, 276-579, 306-371.
See also L. Carmiohaol, Sir Charles
path., 2,

NOTES

93

Belli a contribution to the history of

61, 1926, 151-171; The impulses pro-physiologioBl

duced by sensory nerve-endings; impulses set up by touch and pressirre,
ibid., 61, 1926, 465-483; Adrian,

psychology,tsijchoL

Rev., 38, 1B28, 188-217, esp.

191-

198 (favors Bell over Magendie);A History of Experi-

The impulses

setmental Fsyohologij, 1929, 35-38, 44

nerve-endings;

impulses from pain

(favors Bell); Fulton, op. clt, 1938,

receptors,

20 f. (favors MageniBe).

Forbes, R. H. Miller and J. O'Connor,

E, G. Boring,

The modem research on

sensory

ibid.,

up by

62,

sensory

1926,

38-51;

Electric responses to acoustic stimuli

conduction has been excellently sum-in the decerebrate animal,marized by E. D. Adrian, The Basis

Physiol, 80, 1927, 363-380; Adrianof Sensation, 1928; The messages in

109, 1931, 1-18; The Mechanism ofand H. Mat&ews, The action of lighton the eye: the interaction of retinal
neurones, 3. Physbl, 65, 1928, 273298; Adrian and K. Unuatli, The

Nervous Action, 1932.
The discussions and experiments

impulse discharge from the Pacinian
corpuscle, ibid., 69, 1929, 139-154;

cited in the text are, in chronologicalE. G.

order, as follows: £. Sieinach, Ueber

nature of the acoustic response: thedie elelctromotorischen Ersclieinnng-

relation

sensory nerve fibres and their interProa. roy. Soc., Sect. B,

pretation,enanuillerAmer. 3.

Wever and C. W. Bray, Theade-between sound frequency
and frequency of impulses in the

Rcizung, Arch. gas. FhysioL,

auditory nerve, 3. exp. Psychol, 13,

Hautsinnesnervenbel

3, 1896,

49S-S20; F. J. J. Buiten-

1930, 373-887; Present possibflities

dijk.

On

the negative variation ofof auditory theory, Psychol. Rev., 87,

thenervuscaused by a1930, 365-380; B. H. C, Matthews,

sound, Akad. Weltensch. Amsterdam,

The response of a single end organ,
3. Physiol, 71, 1931, 64-110; Theacusticu.s

Proe. Sect. Soi., 13, 1010, 649-652;

and A. Gregg, Electricalmammalian reflexes the

A. Forbes
studies in:

response of a muscle spindle during
active contraction of a muscle, ibid.,

McK.

cmrolation between strength of stim-72,

and Ihe direct and reflex nerve
response, Amer. I. Physiol, 39, 1915,

Cattell

172-235, esp. 225-232; L. T. Troland. The ‘all or none' law in visualfibres,tcll

and Hoagland, Response of tac-

response, 3. opt. Soc. Amer., 4, 1920,

tile

receptors to intermittent stimula-161-188; E. D. Adrian and Forbes,
The all-or-nothing response of sen-

tion,

uli

sory

nerve

fibres,3.

Physiol,

58,

1922, 301-330, esp. 315-329; Forbes,

1931,

153-174; Adrian,and H. Hoagland, Sensory

discharges in single cutaneous nerve
Aid., 72, 1931, 877-391; Cat-ibid.,

1931, 393-404;

72,

Davis and L.

J.

Saul,

rents in the auditory tracts

midbrain of tbe

cat.

H.

AcHon curof the

Science,74,

Campbell and H. B. WiUlams,

1931, 205 f.; Saul and Davis, Electri-

Electrical records of afierent nerve

cal phenomena of the auditory mech-from muscular receptors,

anism, Trans. Amer. otol. Soc., 22,Amer. 3. Physiol, 69, 1924, 282-303;

177-183; Adrian, The impulses pro-

1932, 137-145; A. J. Derbyshire and
H. Davis, The action potentials of tireauditory nerve, Amer. 3. Physiol., 113,
1935, 476-504. For further discussion of auditory action potentials andreferences to tne literature, see Chap.

duced by sensory nerve-endings,

11

C.

J.

impulsesE. G. Boring, Auditory theory withspecial reference to Intensity, volume

and localization, Amer.
37,

1926,

Physiol,

3.

Psychol,

157-188, esp.

158-181,

61,

1926,

3.

49-72; Adrian.

Specific Nerve Energies

and Y. Zotterman, 'The impulses produced by sensory nerve-endings: theThe

response of a single end-organ, (bid..

for thetopicsof thissection have,most part, been more fully.

PHYSIOLOGY OF SENSATION

94

considered in E. G, Boring, A Hhtorij

Ahhaiidhingni

of Experimental Fmjcholo^ij, 1929, as8f.); Handhuch der phystohgisclwn

cited below.

Optik,

On tile doctrine of specilic nerveII,

1883, 2-23, esp.

If,

1860, sect. 17 (aanio hrenergies in general ( antecedents, Ball,

3 od., aird Eng. trau.s.); also 2 cd.,
1896, 349, where Helmholtz notes

Helmholtz), seethat his USB of Miiller’s principle isextension,

Muller,Boring, op. cit., 77-96 and referenceson exteusion of it.

there cited. See also H. Weinniann,

On phrenology, see Boring, up. cit.,

Die Lehre von den Sinnesenergien,

47-57 and rcferencos there cited. F.
Gall’s classics are Anatomic ct
J.

1895; W. Nagel, Handbuch det Fhijstohgie des Menschen, III, 190S, 1-15;

physiologle (fulltitle

in the text),

A. J. McKeag, The Sensation of Painand the Theory of Specific Sense En-

1810-1819 (Spiirzheim was collaborator in the first two volumes); Siirargument for theles fonctions du oeroeau et sur celles

principle is in his broclinre of 1311,

peceding section of these
For Johannes Muller on thede chttcune de ses parties, 1825. Opposed to Gall was M. J. P. Floiuens,
Examen de la pkrcnologie, 1842, On

doctrine, see his Ztir vergleichenden

Iho antecedents of phrenology hi the

Fhysiologie des Gesichtssinnos, 1826,

faculty psychology of tho

44^; Ilandbuch der Fhysiologie desSelinol, see H. 13. Spoerl, Foeultles vs.

Menschen, II, 1838, Bk. 5, inlroditotory section ( or Eng. Irons. )On adequate stimulation (speeide

traits; Gall's solution.

ergies, 1902. Bell's

op, cU.,
notes.

irritability ),

sec

A.

v.

Haller,On loeidlsallon of Imln funrtlonin geueml, .seeJ.

.Soury, (lerviun, in

Soc, reg.

C. Uiehet’s Dti'llonnnire do Physiol-

GatUngensls {GeseU. Wise, G6(-

ogle, 11, 1897, 5.17 •670, 788 '.952;
Boring, op. eU„ 58-7(1, 5,59 1„ 568 f,

irrllabilibns.

Soi.

Comment,

Character and1936, 210-231, esp.

219-225.

Oo

partibus corporis humani sonsibililwei
etPcrsimallty, 4,

Scottishtingen), 2, 1752, 114-158; Miiller,foe. ait.; E. Iloring, in L.

Hermann's(Uohuido, Klimtens,

llroea,FtllsehHandbuch der Plujsiologie, III (2).

luid Hitzlg, Fninz, Lashley), In pnr-

1880, 430-433; C. S. Sherrington, in

ticnlnr, see

E. A. Schafer's Text-Book of Physiology, 1900, II, 950-954, 960 {.; Tite

cherches cxirMmcnluh's sur Irs pro-of the Nervous

neroctix dans les aniinaux oertfbrds,

System, 1900, 12 f,; McKeag, op, cit,,

47-50. The unfortunate word jnode-

1824; Experiences sur Ic systdme ncrveux, 1825; 2 etl, of both under title

quate is used by McKeag (1902) inofdouble quotation marks, ns if (incorrectly) Muller used it. Sherrington(1906) does not use it, but it seems
to have drifted into modem texts. In
1911 Luelanl used it but Ladd andgage arliould, sulvi d'nne observationd’aphcmio (parte de la parole). Bull,
Soc. anal,, 2 ser., 6. 1861, 33(1-357;
G. Fritsch and G. Hitzig, Ueber die

Irstegratioe

ActionWoodworth did not.

jirivtos et

M. J.

P,

Flmirens, llo-

les fonctions

du systdnie

first, 1842; C. Broca, Remarques
sur lo si6ge de la facultd du lan-elektrische Errcgbarkeit des Gross-On the extension of the doctrine to
specific qualities within the senses,

see Nntanson, Arch, physiol. Heiffc,

W. Volkmann,hints,

Arch,

Anal.

Physiol,

1870,

300-332; K. S. Lashley, Brain Mechanisms and InlelUgence, 1929, esp.

olope, II. 1844, 521-528; H,

23-26, 88-89, 157-174; W. S.
Hunter, A consideration of Lashley’s
dioory of the equipotontialily ofholte, Ueber die Tbeorie der zusam-

cerebral action,

3, 1844, 515-535; A.

in R, Wagner’s Handhuch der Fkusi-

mengesetzen Farben, Ann, Phys,
Chem., 103, 1852, 45-86, esp. 47-

49 ( reprinted in his Wissenschaftllche

3.

J.

general Psychol,

1930, 455-488.

On sensory centers, sec Soury, op.
cit.,

pp. 898-952; also the excellent

NOTES95

elementary diacussion os of its date in

Julius Bernstein’s theory of pro-W. James, Prtnchles of Psychohgy,

jection and irradiation is in his Unter-

41-62. For the oiMnal experiments and discussion of me tliree

suchungen iiber den Erregungaoorgang im Newen- und Maskekystem,

men especially mentioned in the text,

1871, 165-202.

1890,

I,

The Functions of the

For the modem status of the anat-

Brain, 1876, 2 ed., 1886| F. L. Goltz,

omy and physiology of projection, see

see D. Ferrier,

F. Fulton, PhySabgy of the Nerv-

XJeher die Verrichtungen dea Groas-J.

hima, 1881 (4 papers, 1876-1881);
H. Munir, Ueber die Functionen derous System, 1938, 291-^98. On auditory projection, see S. S. Stevens andCroashimrhide,of research and opinion in this com-

H. Davis, Hearing. 1938, 413-418,
481-433; and, in pardoular, H. W.
Ades, F. A. Mettler and E. A. Culler,
Effect of lesions in Ihe medial genicu-

plicated and disputatious field. As an

kto bodies, Amer. J. Physiol, 125,

introduction to that history, see the1939, 15-23.

1890 ( 17 papers,
1877-1889). The text malces no attempt to treat adequately the history

discussion of it and the 52 references

On the possibility of functionallycited by J. F. Fulton, Physiology of

precise point-to-point projection in

the Neroous System, 19S8, 840, 347 f.,

smte of cortical end-ar^rizations of

365, 3761., 397 f.

the neurons, see die discussion in

On specificity of afferent somatic
fibers(size

of fiber, speedof im-

C. T. Morgan’s forthcoming Physiological Psychology.

pulso), see J. Erlanger, 11. S. Gassor

and G.

II.

Bishop, Tlio

compoundIsomorphism

nature of tlie action cuirent of nerve
ns disclosed by Urn cathode ray oscil-

On die views of four of the men

lograph, Amet. 1. fhystol, 70, 1924,

624-866; Gasser nnci Erlanger, The

mentioned in tliis section, see E. G.
Boring, A History of Experimentalrole played by the sizes of oonstituent

Psychology,

1929,

and

references

fibers of a nerve Irunk in determining

there

as follows:

Descartes,the form of its action potential wave,

dualism and interactionlsm, 158-164,
177; Leibnitz and parallelism, 165-

ibid.,

80,

1927, 522-547; Erlanger

and Gasser, The action potential infibers of slow conduciion in spinal
roots and somatic nerves, ibid., 92,
1930, 43-82. On the possibility thatthe small slow fibers may mediate
pain, see E. D. Adrian, The message
in sensory nerve fibres

and dieir in-

188,

cited,

177 f.; Hardey, associationism

andparallelism,
195-202,
206;
Fochner, psychophysics, parallelism,

Nachtonsicht and Tagesansicht, 265287.

For the history of psychophysicalsee R.

parallelism,

Eisler,Worter-109, 1931, 1-18; The Mechanism ofbuch der phdosophischen Begfiffe, 2ed., 1929, II. 377-386 (art Poral-

Neroous Action, 1932, 22-60.

lellismvs).

terpretation, Froc. roy. Soo., Sect. B.

For a representadve pre-sentadon of the view as of the latenineteenth century and influenced by

Projection

the theory of the conservation of enIn a large measure this section isan anticipatory summary of many
matters

wWh are discussed in detaillater in this book. See, therefore, theergy, see A. Bain,

Mind and Body,

1872 el say., esp. Chap. 6; also his
The correktion m nervous and mental
forces, in Balfour Stewart, The Con-

cross-references in the text and dren,

servation of Ertergy, 1874, 205-286.

appropriate citations of the

For a fairly kte draense of interac-

for

tlie

literature,

the

notes

for

topicswhich cross-reference is made.

to

W. James, Principles of
Psychology, 1890, I, 123-144.

tionism, seePHYSIOLOGY OF SENSATIONThe classical papers on the me-155-223; G, E, Miillor, Zut Psycho-

chanical equivalent of heat (Joule)physikand the laws of the conservation ofenergy and of entropy (Kelvin) are

Z Psychol, 10, 1896, 1-82, rap, 1-

On the mechanical equiv-

Studion ubor das Schen von Betve-J.

P, Joule,

25;

dor

Gesiehtscinpllndu’ngen,

M. Wertheimer, Experimeulelle

alent of heat, Fh{L Tnms., 140, 1850,

gung, ibid., 61, 1912, 161-265, esp.

61-82 (read Juno 21, 1849); William Thomson (Lord Kelvin), On the246-252; W. Kohler, Die phy.dschen

dynamical theory of heat, Tr/ins. toy.
Soc. Edinburgh, 20, 1851, 261-298,

Zustimd, 1920,

475-482,

The Place oj Value in a World of

For the development of the psychophysical axioms into the isomorphic
principle,

see R.

H. Lotze, Medi-

Gestallen in Riihc nml Im statlonilren

Facts,

230-232; H.

Grassmann, Znr

1938,

Principles

58 69;

1929,

185-232;

K.

Gestalt

Psychology,

of

KoJIka,1935, 61-67.

One criticism, as well as a posi-

cinische Psychologle, 1852, 206-232,
esp.

173-195, esp. 193;

Psychology,

Gestalt

tivistic

restatement of isomorphism,

to he found in E. G.

Theorie der Farbenmischung, Arm.

is

Phys. Chem., 105, 1853, 69-84 (Eng.

chophysical systems and isomorphic

trans.,

Phil.

Mag., 4

act,,

7,

1854,

relations,

Psychol

Boring Psy-lieo.,

254-264); E. Mach, Ueber die Wir-

565-587, asp, 579-,586;

kung der rSumliehen Vertlieilung deslogical

Lichireizes

auf

dor Nelzlmut,

Sit-[unction

is

thi'

48,

1930,

A psyeliorel.illonofsneeessivo dilferentliillons of eventsM,zimgsbar. Akad. Wiss, Wien, math.-in the orgimlsni,

naturw, Cl„ 52 ( 2), 1865, 303-322,

401, osp. 4.541,;

esp, 320; E, Hering, Ztif Lelire win

slateinent ot

Lfehtskne,

77;pliysieul iixloniN, Ihlil, 48, 1941, 4.57-

F. C, Donders, Ueher Farhonsyslcme,

464. The issue flntilly redueas itsell to

Araft. Ojjthal Berlin,

niitivism vs. empiricism.

1878,

74-80,os]).

27 (1), 1881,(1.

44, 1037, '14,5-

An I'lJeisttlimnl re1!.

Mlillct's

psyeho-Chapter 3

VISUAL SENSATION: BEGINNINGSA S WE turn now to the history of the psychology of sensa-l\ tion, we see how recent has been the emergence of the

A ^separate sciences from natural philosophy, The formal distinction

between psychology, physiology and physics is but a

product of the scientific specialization of the nineteenth century.

Only recently could it be said that psychology deals with immediate experience and physics with radiate experience, for originallyallscience bore dhectly tire stamp ofits

own empiricism. The

natural philosopher was interested simply in the natural world as

he knew it or could come to know it, and he knew it first, ofcourse, in immediate experience. Thus light is a concept invented
to explain vision, since it was perception that set the first problems
for physics. In fact, three ot the dassieal chapters ofphysics-

light, heat and sound—were fixed by the nature of perception; it

was only muoli later that iraperceptibles like electricity, magnetism, invisible

liglit,radiant energy

and wave-motion became

equally important. For this reason, then, the first important knowl-edge of color and its stimulus was contributed by Newton, ofvisual space per-ception by Kepler, of the tonal stimulus by Galileo.

These problems, which the psydiologists now claim, had

meaning and importance for the great natural philosophers of theseventeenth century. They were neither physics nor psychology
then; they were philosophy,

Before Newton
The early knowledge about light consisted of certain simple
laws of its behavior and control. The Greeks knew that burning

glasses—usually glass spheres filled with water—piagnify the objects seen through them. Euclid laid down the laws of optics—that

light travels in straight lines, that the angle of reflection is equal

to the angle ot inddence. Althou^ refraction was Icnown, philoso-—98

BEGINNINGS OF VISUAL SENSATION

phers erroneously believed that the angle of refraction equals theangle of incidence; only in 1621 did Snell formulate the exact law,

Lenses could be ground, however, and Roger Bacon in using themas an aid to vision may be said to have hi vented spcclnelcs (1266),

By the sixteenth century spectacles were being made commercially, and it appears to have been a Dutch spectacle-maker who,

in 1608, made lie first telescope as a curiosity. Galileo seized atonce on this principle, built a better telescope in 1609, and, byuse of it, observed the satellites of Jupiter early in 1610, Indeed,
the practical scientific need for the perfection of the telescope didmore than anything else to stimulate an intei'est in optics at thistime. Thus Kepler, the astronomer, published in 1604 and 1611 twoimportant works on optics, dealing with the refraction of light, theproperties of lenses and the theory of vision.

Meanwhile there was no adequate conception of the nature oflight. The ancients had thought of light as an emanation from theeye, one which mingles with anoilicr emanation from the object

a partly subjective view whicli is natural enough when one considers how voluntary is vision. Tlie Epicurenn.s, for raamplc, be-lieved that objects emit images which cuter tho eye and give viseto the perception of tho objects. It was this view,a,s

wc have,seen, which Johannes Muller was combating (1826, ISBS)

when

he argued that the sensorium perceives, not the Iraasmillcd properties of objects, but the specific energies peculiar to the oxoitod

nerves. These ideas show us how tho physical problem was originally psychological; the concept of lightcame into existence toexplain the correct perception of objects at a disUmoo. Aristotle

came nearer the modern view in supposing that light is a qualityof a medium intervening between the object and the eye. Descartes (1630 ef seq.) held light to be a thrust or pressure of theseen object upon the eye through the intervening medium.

During the seventeenth century the two classical theories ofli^t became established as alternatives, the one holding light tobe a wave-motion of an all-pervading medium (undulatory theory) and the other asserting light to be the projection of particles

by luminous bodies (corpuscular theory). The corpuscular theory
was consistent wjth the traditional view that objects give off something which enables them to be perceived. The undulatory theory,on the other hand, seemed better to agree with the speed of lightand the fact that bodies do not become exhausted by remaining•

NATURE OP LIGHT AND SIGHT

99

visible. Though there are said to be hints of the undulatory con-ception in the writings of Leonardo da Vinci and Galileo, the thefirst definitely kid down by F. M. Grimaldi (1665).
Huygens too ( ca. 1678 ) effectively promoted the theory; but, since

ory washe and the others of his time thought of the waves as bngitudinal—for that is the natural way in which a wave could exert a thrust—or pressure upon the eye^he could not explain double refraction

and the facts of pokrization when these phenomena came to his
attention.

Newton, however, after weighing both views, finallythrew the weight of his opinion to the corpuscukr hypothesis. He
could reconcile it better with the phenomena of rectilinear transmission of light, of pokrization, and of the colors of thin films.

With such uncer tainty about the nature of light, there was, ofcourse, no assurance about the rate of its propagation. Tradition

held the transmission of light to be instantaneous, a conception

which has the advantage of according with the common belief
that we see objects as they exist at the moment, not as they werein the immediate past. (Tlie same belief was to lead physiologists

before the middle of the nineteenth century to believe that thetransmission of the nervous impulse is so rapid as to be practicallyinslanlaireous, else perception

event. It seemed evident towould kg behind its perceived

common sense that there is no suchlag. ) In tliis matter of the velocity of light Kepler held to tradition.

Descartes, however, who thought of fight as a pressure-thnrst in
tiro intervening medium, could conceive of its speed as infinite, andit did notseem to him that time would be required for a pressure

to be transmitted when no body had to be actually displaced. It

was Rbmer (ca. 1676) who fovmd a difierence in the time of theeclipse of one of Jupiter’s moons according as the earth was moving toward or away from Jupiter, and who thus computed a finite
velocity for light at a value which is about two-thirds of its true
value.

The development of the physiological optics of the eye is thenecessary prelude to' the psychology of visual space perception.

Before Kepler there seems to have been no adequate conception of
the functioning of the eye. The traditional view was derived fromthe Arab, Alhazen (d. ca. 1039 aj5.), who consi;Jered the lens as
the sensitive perceptive organ. Kepler (1604, 1611) noted, as had

Leonardo da Vinci before km, the similarity of the eye to a catnent
obscura. Concluding that the lens of the eye forms a small in-BEGINNINGS OE VISUAL SENSATION

100

verted image of a perceived abject upon the retina, he decided,
therefore, that "sight is a sensation of the stimulation of the retina.”

In addition, he noted the fact of after-image as showing that theretinalimage persists after the stimulation has ceased, and heespoused a chemical theory of stimulation by suggesting that lightaiects the retina in the way that light from a buiiiing glass affects
a combustible substance. Accommodation ho explained as due tochange in the relative displacement between tire lens and theretina, noting too that beyond the retina it

isnecessary for theimage to be transmitted by a “spiritual current” to the sent of thefaculty of sight in the brain. Thus he raised, and for the first time,that constantly recurring question as to why,

when die retinal

image is inverted, we nevertheless see the world as upright. All
told, Kepler

may he said to have f oimulnted the essentials of physi-

ological optics as they still existed for Johannes Muller two centuries later.

Descartes helped to establish Kepler’s view. Having demonstrated the formation of retinal images inan eye from a hull, he

described the fact of varying couvcrgoiicc in the poreeptiim of objects at different distnneos. It

was only a little liitet (1B68) that

Mariotte discovered the blind spot, and localized it at the point ofemergence of the optic nerve from the retina, This speolaculai' disoovciy was even demonstrated by tlic floyal Society to Charles 11.
It clearly established the retina, and not the lens, as the peroeptivo

surface.

The physios of hght, however, had still not caught up with theobvious facts of visual perception. Tlicro was before Newton nosatisfactory theory of color. The infinite variety of die visually per-ceived world was np to that time explained only as to its spatial
characteristics; light travels in straight lines and, following therefractive laws of the ocular optical system, foims an image on thesensitive retina. Yet without color the world would lose many of itsdistinctive perceptual eharaoteristics. The ancient theory was thatcolor results from a mixture of light and darkness— as indeed might

be said to be true of the grays, tiiough not of the chromatic qualities.

Kepler tried unsuccessfully to ascribe color to different prop-

erties of the perceived object. Descartes for his part suggested thatcolor depends upon different rates of rotation of the particles of

the transmitting medium. That bodies modify light in acooidancewith their structure, in the way that different bodies give off dif-il

NEWTON101

ferent musical notes, was the proposal made by Grimaldi. Finally

Hooke ( 1605 ) held that there are two primary colors, red and blue,that tile other colors are intermediate between these two, and thatthe color depends upon the obliqueness with which the ray strikes
the retina— one oblique angle inducing red, the opposite angle
blue, and intermediate angles intermediate hues. He came to thisview from a study of the colei's produced by thin plates. Althoughthese last three theories all suggest that color is a special propertyof light, they are vague, speculative and unsatisfactory. It took the

genius of Newton to discover that color is simple and fundamental,

and white light a special case (a mixture) of colors.

Isaac Newton
Tlie formulation of the first correct tlieory of color is due to Sir

Isaac Newton (1642-1727). Newton, whose name is one of themost distinguished in the history of science, had already entered

upon almost all of his important lines of thought before he wasthirty. In the years 1605 and 1666, the years of the Great Plague,

Newton, then in his early twenties, a student but not yet a Fellow
at Trinity College in Cambridge University, achieved the follow-

ing ideas: (1) he discovered the binomial theorem; (2) he in-vented (except for an anticipation by his teacher, Isaac Barrow)both the difl^erential and the integral calculus; (3) he conceived
his theory of gravitation,

and applied it to the behavior of themoon, being prevented for twenty years from public announce-

ment of the law only because his calculations, based upon an incorrect measure of tlie size of the eai-th, were not consistent; and(4 ) he purchased at the Stourbridge F air a prism for the purpose of

studying the refraction of light The experiments with the prism,

postponed by his absence from Cambridge at the time of the
Plague, he took up shortly thereafter. It was by way of these researclies on optics that Newten first came to scientific fame.

Newton’s discovery was that the refraction of white tight by aprism breaks it up into the different spectral colors which can bedifferentiated from one another, each by its specific degree of refraction. At first this discovery was primarily important to him be-cause of its bearing on the improvement of the telescope. That
spherical lenses entail an aberration due to tlieir shape had beenshown by Descartes. Now Newton, seeing that lenses must also in-BEGINNINGS OF VISUAL SENSATION

102

dues a chromatic aberration, decided, because of his erroneous
conclusion that all glasses have the same refractive power, that it

would be forever impossible to correct for this distortion. Thus ho
was led since tliere is no diromatic dispersion in the rcllcction of—light—to invent the reflecting telescope. He constructed with his

own hands, polishing the mirror himself, a small model whicli waspresently shown to tlie Royal Society and caused him to be elected
to its membership in 1672.

Surprised at fte favor with which his telescope was received,

he offered to present to the Society a discovery which, as he put it,“I doubt not will prove much more grateful dran the communication of that instrument [the telescope], being in

my judgment theoddest if not the most considerable detection which hath hitherto

been made into the operations of nature." This odd and considerable detection was his research on color, which he presented in apaper in 1672, when he was twcniy-ninc. The paper drew great
attention and also mucli criticism, e,specially from Robert Hooke,

Controversy about facts, which, being hardly more than the description of experimental results, seemed .scarcely eoutrovcrtiblo,

lasted for three years. Nowlon haled the controversy, Ho sakb “I

was so persecuted willi disaissions ittisiiig out of my theory of lightthat I blamed my own imprudence for parting with .so substantial
a blessing as my quiet to run after a shadow,” Thi,s bitterness about
scientific quarrels lay heavy upon him for over twenty years, load-

ing him to avoid and delay publication. Tlic full account of his

experiments on light he withheld until after

all hisother im-portant work, for it was thirty-two years after his youtliful paper

before the Royal Society in 1672 that, as president of the Society,he published in 1704 the Oplicks, with three later editions following on (1717, 1721, 1730).

Newton’s contributions to the theory of color

may be enu-

merated as follows.
1.

He showed that every color has its specific degree of rofrangi-

bility, and that every degree of refrangibility has its specific color.

Thus he established refraction as the fundamental operation for
chromatic analysis.
His simple experiment is shown in Fig. 7. A beam of white lightfrom the sun in being refracted by a prism, P, was dispersed on thescreen, Sj, into the spectral band of colors, vihgyof. There was nodispersion in the direction of the axis of the prism; the band of

NEWTON: COMPLEXITY OF WHITE LIGHT

103

colors was just as wide as the round hole, A, through which thelight came. In the direction of refraction the band was, however,

never less than five times as long as the diameter of the hole, and,of course, the colors always fell in the same order, with the violeton the side of the base of the prism. Newton complicated this experiment in various ways, always with the same general conclusion. For instance, he introduced (Fig. 7) a second prism after theprism, P, and at right angles to it, so that the light was refracted

Fio. 7.

Newton’s Expehment on the Pbodcction of Colors bt

RE miAcnoN (1704)

A boom ot whila light, passing ihtongh the small cireular aperture, A,
ill

tlio

sliullcr,

Sr,

isrefracted

by the prism, P, producing the spectrum,

VIBGYOR on llio sooen. Sa. The spectral band is as wide as the aperture,A, but mucli longer, because of the diilcreet refrangibility of the Cerent
colors.

Newton thought that only seven colors could be distiuguisbed in

the spectrum.

horizontally as well as vertically on the screen, S,. He wondered

whether ho would obtain thus a square spectrum, but the eSeot

was that the band on Sj was rendered diagonal on the screen instead of vertical. In other words, the “homogeneal” violet at « was

not dispersed, being homogeneal, but was refracted most to theside, and the “homogeneal” red at the other end, r, was not dis-persed but was refracted least to the side. This experiment showedthat pure light, while still obeying its law of refraction, cannot be
split up furdier by refraction, but is bent an amount that is properfor its color.
2.

Thus Newton also showed that the white li^t of the sun is

not simple but is compounded of all the colors.

While this conclusion follows from the experiment of Fig. 7, it isshown more convincingly by the experiment diagrammed in Fig.
8. Hero the beam of white light, W„ dirough a round hole, A, is104

BEGINNINGS OF VISUAL SENSATION

dispersed by the prism, F,, into the speolmm, vr, which falls upon

the lens, L. The lens collects the dispersed colors and focuses themupon the prism, Pa, which is placed so as to reverse the refractive
action of Pj. Thus at W. we gel a beam of white light again, exactly like the beam at W,. If a third prism, Pj, is introduced, thenthe beam at Wj is again refracted and dispersed to give the spectrum, tv, on the saeen, Sj. In this pairicular arrangement, thespectrum at S* is revei'sed from the spectrum at L, since red isFw. 8. Newton’s Expehiment on Colou Mixtohi! (1704)

Wi Is a beam of wbilo llglu whldi passes tlirmigh the apcrlure. A, latha ahutler. Si, and, being lolrnolud by Inc pilsm,
as a spooUum, or,

I’l,bus Us color tlispcrscd

mon Iho Ions, t, I'bc 1ms brings the oolois lugclbur

again on tho prism. Pi, which, icvosing tlic iciracllon al Pi, rcoombinra Ibo
colors into n beam of wbilo llghl,

Wj, which is like Ibc laiglnal Wi, Tlio
white light of Wi can again bo lofiocicd and dispersed by iho prism, Pj.
so tliat uro spectrum, ru, is tlirown on iho soicon, 8j.

above violet in the one case, and below in the other. That the light
could be so completely mixed up and then sorted out again byrefraction must have been to Newton one of those "oddest if not

the most considerable detections” which he said his early researches had accomplished.

The optical system of Fig. 8 also showed Newton that whitelight is a particular combination of colors. If he eliminated one orseveral colors by intercepting them near L, the light at

Ws was ingeneral no longer white, but of a hue corresponding to a mixtureof the remaining colors.
3.

Newton concluded enoneously that there are only seven sep-arate homogeneal cobis: red, orange, yellow, green, blue, indigo

and violet To account for this error we have to consider the psychology of the scientist. White light had always been regarded as
simple. To ask natural philosophy to believe that it is a combinattan of even as few as seven colors was to strain credulity, as in-NEWTON’S LAWS OF COLOR

105

deed the bitter opposition to Newton s theory showed. To proposea very large number or an infinitude of colors would have seemed

an absurdity; in asking for seven colors Newton was already asking
for more adjustment of thought than he could easily get. Nor was

Newton liiinself ready to find a finer analysis. He became convinced, in fact, that lliere ought to be some similarity between thecolors and the musical intervals of an octave. There are seven dif-ferent tones in an octave; why not seven colors in the spectrum?
If the spectrum, he said, were spaced off by divisions placed so as

to be proportional to the numbers 1, %, %, %, %, %,% b and Va,,

the spacing representing "the Chords of the Key, and of a Tone, adiird Minor, a fourth, a fifth, a sixth Major, a seventh and an eighth

above that Key,” then “the Intervals will be the Spaces which theseveral Colours (red, orange, yellow, green, blue, indigo, violet)

take up.”

In view of Newton’s great caution in drawing conclusions andhis careful use of experiment to constrain opinion, it is natural lor

us to wonder how ho arrived at this correlation between the spec-

trum and die octave. Newton wrote: “I delineated therefore in a
Paper the Perimeter of the Spectrum,

.

.

.

and I held the Paperso lhal Ihc Spectrum might fall upon tins delineated Figmu, andagree with it exactly, whilst an Assistant, whoso Eyes for distinguishing Colours were more critical than mine, did by right lines

drawn cross the Spectrum, note the Confines of the Colours.

.

.

.

And this Operation being divers times repeated both in the same,and in several Papers, I found that the Observations agreed wellenougli with one another.” Did the assistant just chance upon
seven divisions as convenient with the spectrum that was presented
tohim? Did he have the nature of the musical octave in mind

when he decided where to put his lines? Did Newton suggest any
pincdple of division to him? We shall never know, but we seem
here to have a case of what has since been called the effect of laboratory atmosphere.’

The observation was much more sensible

than die truth.

Newton could not test this part of the theory further by refractive analysis. With enough refraction he might have expected todivide thespectmm into seven separate patches. A spectrum

spread so long, however, becomes too faint to observe. The samething happens if the aperture, A (cf. Fig. 7), is made very small.

The spectral band, or, consists of a series of overlapping images of

106

BEGINNINGS OF VISUAL SENSATION

the hole in tlic screen, S], If the hole were very smiill, one might ex-pect to get seven small circular spots for a spectrum; but actually,
if the hole is very small, thespectrum is too faint to be observed

clearly. Newton tried a tiiangular hole, which gave a bright con-tinuous spectrum on the side corresponding to the base of the triangle, but only a very faint band on the side corresponding to theapex. Even though he never got seven spots of color, it was to be

more than a century before anyone realized that the spectrmn includes an infinitude of wave-lengths.
4.

Newton formulated two of the laws of color mixture.

(I) “Colours may be produced by Composition which shall belike to the Colours of homogeneal Light as to the Appearance ofColour, but not as to tire Immutability of Colour and Constitutionof Light. And those Colours by how much they ai-e more com-pounded by so much ate they less full and intense, and by too
much Composition they may be diluted and weaken’d till Qiey
cease, and the Mixture becomes white or grey. There may be also

Colours produced by Composition, which arc uot

My like any of

the Colours of homogeneal Light.”(II) “Whiteness and all grey Colours botwoen while and black,may be compounded of Colours, and the whUcne.ss of the Sun’s
Li^l is compounded of all the primary Colours mix’d in a duo
Proportion.”

The greater number of experiments supporting these laws wasmade with the optical system of Fig. 8. By allowing only certain
colors to pass at L, the resultant mixture can be seen by placing ascreen at Wi.

Newton found that, with proper combinations oflights, fewer than all the primaries can produce wliite.

He foundtoo that, the more complex the mixture, die lesser the saturation of

the color. The rapid succession of colors, he showed, produces thesame result as their simultaneous mixture. This last discovery hemade by fashioning a cardboard comb with teeth as wide as thespaces between them and moving the comb rapidly up and downat the lens, L ( Fig, 8 ) In this case some of the colors were always.

intercepted at any moipent but die rapid succession gave while at

Wj. His reference to mixed colors, “which are not fully like any of
the Colours of homogeneal Light,” was, of course, to the purples.

He also showed that gray is simply a less “luminous” white.
After rubbing gray powder on the floor of his room and lotting thesunlight fall upon iL he placed a piece of white paper of the same

NEWTON’S LAWS OF COLOR

107

size as the patch of gray alongside the gray but in Ihe shadow.

When he viewed these two stimuli at a distance too great for him
to identify the objects by their texture, the gray powder looked

whiter than the white paper. Then he adjusted the intensity of thelight until theylook^ alike. He chedced the observation. “A

Friend coming to visit me, I stopp’d him at the Door, and before
1 told him what the Colours were, or what I was doing; I asked

him, Which of the two Whites were the best, and wherein theydiffered? And after he had at that distance viewed them well, heanswer’d, that they were both good Whites, and that he could not

say which was best, nor wherein their Colours differed.”S.

Finally we must note that Newton by these experiments wasable to advance what was at once the first and the correct theory
as to why objects are differently colored. The color of objects, hedecided,isdue to their selective reflection of the homogeneal

lights. “They become colour’d by reflecting the Light of theirown

Colours more copiously, and that of other Colours more sparingly.”

For instance, he found that dimabar, placed at W, (Fig. 8), be-came more red when the blue and green light was intercepted at
L, and that it appeared not red at all when the red light was intercepted, but a dull yellow-green.
It was in these ways that Newton

discovered and establishedwhat is in its essentials the correct theory of color. The discovery is
an instance of the unusual case where an apt experiment under theattention of a keen mind establishes a positive body of fact where

only vague and inconect guesses had existed before. Newton’s
theory of color had no anticipators. There has been no argument

about priority in respect of it. It was all too absurd a truth to havebeen guessed—that fact that white or gray, which appears as

primary, fundamental and prior to the colors, should be, in contradiction of immediate experience, nothing but a mixture of all

the colors instead of the absence of all of them. Of the advantageof experiment over intuition there could be no better illustration.

Thomas Young
During the eighteenth century there was very Jittle advance inthe psychophysiology of vision. Research in optics had mostly to

do with the development of the reflecting telescope, which avoids
chromatic aberration, and of the achromatic lens, which corrects

108

BEGINNINGS OF VISUAL SENSATION

chromatic aberration in the refracting telescope. Huygens Iwcl

sponsored the wave-theory of light, but Newton had come overgradually to the corpuscular theory, and so indelibly was Newton’sview impressed upon the scientists of the century that an t'ditor
could assert in 1792 that the wave-Uicory was not hold by a single—although actually Euler and Benjaminphysicist of importanceFranklin had supported it. The shift back to the wave-theory wasbrought about by Thomas Young in England, by Fresnel andArago on the Continent. Young, working with the colors inducedby thin plates, developed tire theory ol interference, which requires a wave-hypothesis of light for its validation.

There was during the century some interest in the mechanism of
the eye, and William Porterfield published in 1759 A Treatise on
the Eye, the Manner and Phaenoinena of Vision. Particularly was
there an interest in the moans by which the eye accommodates its

focus to diflcrent distances. There were three chiel tlicories of ac-

commodation; (1) that the cornea changes its curvature; (2) thatthe eye changes its length so that the distuacc between the leius andthe retina is altered; arrd (3) tlrat tho lens changes its eiirvaturc.

(See pp. 272-279.) A fourth iurplausible view was (4)

tliai

the

refractive index of the media of tiro eye might bn altered in ac-commodation. Thomas Young, ns wc shall see presently, performedexperiments that led Irim to tho correct theory, viz., that tho lenschanges its shape.

Aldiough the chief interest in color lay in getting rid of it in telescopes, still there had been a gradual change of view .since Newton. It became clear that, although the number of perceived colors

may be limited (of. Newton’s seven), there is nevertheless an infinitude of degrees of refraction within the spectrum, that is to say,the spectrum is continuous and there are many more Oran sevenkinds of homogeneous light. The discovery by W. H. Wollaston in1802 of fixed black lines in the solar spectrum ( tho lines described

more fully by J. v. Fraunhofer in 1814 and named after him ) served
to differentiate successive parts of the spectrum much more finely

than could be accomplished by any process of immediate observation and color naming. (See p. 177.)

This distinction between the color of light andtirecolor ofsensation was enhanced by the discovery of color-blindness, orDaltonism as it came to be called. John Dalton, the distinguishedchemist who discovered the law of multiple proportions, describedTHOMAvS YOUNG: ACCOMMODATION

109

in 1794 his own case of color-defect and sovoral other similar casesthat had come to his attention. Tlie discovery aroused a great dealof scientific interest. (See pp. 184-18S.)
Into this scene Thomas Young (1773-1820) entered. By training

and subsequent profession he was a physician, but his tempera-

ment and interests made him one of Ihe brilliant natural philosophers of his day. His scientific contributions, according to the list

drawn up by one biographer, covered “fields as diverse as thephysiology of the human eye, hydrodynamics, music, paleography,

atmospheric refraction, theory of tides, tables of mortality, andtheory of structures.” His greatest contribution, as we have seen,
lay in the reestablishment of the wave-theory of light. For us hebecomes impoi1:ant because of his theory of ocular accommodationand his theory of color, both of them theories that failed to gain
proper recognition until Helmholtz established them half a cen-

tmy later.
Thomas Young sought to prove experimentally tlrat the accommodation of the eye is due to a change in lire curvature of thecrystalline lens. His first paper on this subject, presented to theRoyal Society in 1793, resulted in his election to its membershiponly a few days after his twenty-first birthday. Ocular accommodation was a suitable topic for a medical student who

wished toundertake research. His principal paper on this subject, however,

was read to the Society in 1800 and published in 1801. In it he described a simple optometer by which he could measure the focal

length of the eye. He also presented compulations to show the refractive power of the ocular media, and concluded that the ratio of

the refractive power of the lens to the refractive power of water isabout “)4o'He then undertook to dismiss the alternative theories of accommodation. That the cornea does not change its curvature inaccommodation he decided on die basis of two pieces of evidence.
First, he failed to find, even with microscopic observation, anychange in the distance between die images of two candles refiectedfrom the cornea while accommodation was being altered. Secondly, he found that his power of accommodation was in no way
impaired by attaching a small glass lens by wax to his cornea infront of the pupil and filbng the space between the lens and thepupil with water. With water next to the cornea, the curvature of
the cornea could have little rehactive power, and the glass lens

110

BEGINNINGS OF VISUAL SENSATION

really acted as an artificial cornea, tlie shape of whicli could not

be changed. It is doubtful if die eye-ball could be elongated fornear fixation (thus bringing the lens farther from the retina) without the cornea’s being altered in curvature, but Young supple-

mented the argument against this theoiy of accommodation byanother experiment.

Turning his own eye as far as possible inward toward the nose,

he pressed an oval iron ring against the front of the eye-ball sothat he could look through the ring, and then pressed the “ring of akey” at the outside of the socket in behind the eye-ball as far as hecould without too much pain, so that the key was “wedged be-

tween the eye and the bone.” He assumed that in this manner theeye was constrained mechanically so as to prevent its elongation,and yet he found accommodation unimpaired, although the pressure upon the retina created ‘phantoms.’

There remained tlic possibility that the refractive power of theocular media might change. This tlieory he ruled out by tho observation that persons from whoso eyes tho lrn.s has been removed
lose the power of accommodation. Tims there sct'im'd to ho loft

no possible mechanism for accommodation otlicr than a change inthe shape of lire lens. Young made computations as to tlic form of
the change in the shape of lire lens by studying the aborraliou ofrays of light that enter at tlic extreme sides of the pupil and fallupon the edges of the lens. In this way ho arrived at a solid conclusion concerning the nature of accommodation, although it re-mained for Helmholtz to establish the theory and to show how Uie
ciliary process affects die change,

Thomas Young’s theory of cohr sensation appears in four paragraphs incidenttLl to his general discussion of the physical theoiyof colored light. Inasmuch as the theory is purely speculative, it isdoubtful if it could have interested Young so keenly as his experi-mental demonstrations of fact. He first presented his views in 1801,
putting them forth as a modification of Nowton’s theory.

Newton had suggested in a communication to the Royal Societyin 1675—before he had accepted the corpuscular theory of light—that the various rays of light excite vibrations in the retinal termi-

nations of the optic nerve, “the biggest, strongest, or most potent
rays, the largest vibrations; and oAers shorter, according to theirbigness, strengfli, or power”; and these vibrations, he had added,

THOMAS YOUNGi COLOR THEORY"will run

.

.

.

111

through the optic nerves, into the sensorium; andthere, I suppose, affect the sense with various colours, according
to their bigness and mixture; the biggest with the strongest col-ours, reds

and yellows; the least with the weakest, blues andviolets; the middle with green, and a confusion of all with white-much after the manner that, in the sense of hearing, nature makes
use of aerial vibrations of several bignesses to generate sounds ofdivers tones, for the analogy of nature is to be observed."

Newton was thinking about seven colors analogous to sevenmusical tones in the octave. Young, on the other hand, had to consider a very large number of wave magnitudes in the spectrum.

Moreover, Newton was thinking in terms of die traditional view ofperception, to the effect that properties of objects (in this case,vibrations) get themselves transmitted to the sensorium. Young,however, saw that some physical mechanism must be interposed at
the retina, if only because it would not have been possible for asingle retinal point to transmit all the infinitude of vibrations thatmake up the white light which is perceptible at a single point.
With the suggestion diat the taking up of the vibrations by the“must be dependent upon the constitution ofYoung created a necessity for separate retinal

retinal substancethis substance,”

particles with a nervous connection for each. This assumption led

to further consequences. He said; “As it is almost impossible toconceive of each sensitive point of ihe retina to contain an infinite

number of particles, each capable of vibrating in perfect unisonwith every possible undulation, it becomes necessary to suppose
the number limited, for instance, to the three principal colours, red,
yellow, and blue, of which the undulations ore related in magni-

tude nearly as the numbers 8, 7, and 6; and that each of the particles iscapable of being put

m motion less or more forcibly by

undulations differing less or more from a perfect unison; for instance, the undulations of green light being nearly in die ratio 6 %,will affect equally the particles in unison with yellow and blue, andproduce the same effect as light composed of those two species;and each sensitive filament of die nerve may consist of three portions, one for each principal colour." This was in 1801. A year kternew measurements of the spectrum by Wollastop led Young tomodify these remarks “respecting the proportions of the sympathetic fibres of the retina; substituting red, green, and violet,BEGINNINGS OF VISUAL SENSATION112

for red, yeUow, and blue, and the numbers 7, 6, and 5, for 8, 7,

and 6.” These numbers arc, of course, approximalcly proportional
to the now known wave-lengths of their respective colors.

Young’s theory is really a resonance theory ol color, which, byappealing to Newton’s laws of color mixture and their corollarythat all colors can be got from a mixture of three widely separated

hues, was able to take account of the sensitivity of a single retinal

point to a very large variety of colors. Tims naturally did Youngespouse a theory in which color is represented physiologically by
the particular nei-vous elements excited. In so doing he abandoned
the traditional theory that the properties of objects are conductedto the sensorium,

and anticipated Joliannes Muller’s theory of

specific nerve energies (1820, 1838)—a theory which holds thatthe sensorium perceives, not the exciting objects, but the state of
the excited nerves. Had Young realized the importance ol his conception, instead of leaving it for Miillor and Ilclmholtz to discover,he might have had more cfTc-cl upon the history of the psychophysiology of sensation. As it wius, he received crcilit eventually,

but not until long after his death.

GoetheThe poet Goethe (1749-1832) enters Lliis picture because of his
intense and aggi'ossive interest in the theory of color, an interest
that caused him to publish a book of two volumes, Ztif Farhenlehre, in 1810. Goethe was one of Iho great Gormans of his generation, aman of exceptional genius, ambition, power, vanity and in-fluence.

A keenly intuitive observer of life and the world, ho ad-

vocated observation as the primary means of gaining insight into
truth. His faith in the validity of intuition,acteristic for a poet, stamps

an appropriate char-

him as more nearly the philosopher'by temperament than the scientist, making him impatient, as it did,of the intricacies of an experimental method whiclr may yield results at variance with thedata of intuitive observation. Science

adopted the experimental technique because it mistrusted theadequacy of immediately intuitive obseiwation, but to that view

Goethe placed,himself vigorously in opposition. His b6te nolr was

Newton, whose theory of color he reviled in bitter tirade. Presently we must speculate upon the reasons for Goethe’s aversion to

Newton’s theory and experiments.

GOETHE AS SCIENTIST113

To some extent Goethe made good his claim to the scientificvalue ol intuitive observation, He contributed to biology the doctrines of metamorphosis and homologous parts, views that gained
gi'eater significance later in connection with the theory of evolution. His concept of metamoi’phosis was that parts of an organism

change, according to need, so as to assume other functions. AlmostaU vertebrates except man have two upper Jaw bones. Goethe in1786 had discovered that the upper human jaw shows traces ofsutures, as if it had been formed from two bones. The doctrine ofhomologous parts is closely related. Goethe’s intuitive observation
here was to note that stamens, petals, sepals and some other partsof plants bear the same relation to the stem as do the leaves, so thatthey can all be regarded as forming a single class of appendages,

and may have been created by metamorphosis. Wings, forelegs
and arms are homologous. Goethe, seeing a broken sheep’s skull ontirebeach, perceived it as the modification of several vertebra.

Mucli later Helmholtz remarked that there is very little exact

moaning to such a vague concept, for there is not much more to—apart from metamorphosis andthe doclrino of homologous parts

evolution—-than tire statement that plants have many lateral ap-

pendages of various forms. Yet Goethe, the poet, was never shaken
in his belief that the fundamental scientific method is this intuitive

observational insight.

Zur Farbenlehrc consists of three parts. The first half of the first
volume includes the description of many subjective phenomena ofcolor and brightness, observations which before had neither been

made so systematically nor set down so fuUy. They represent
Goethe’s useful contributions to the psychology of vision. The second part of the volume is devoted to a long unreasonable polemic
against Newton, and also, incidentally, to Goethe’s color theory, if

the result of this intuitive method can be called a theory. The sec-

ond volume is a full and detailed history of optics.
Let us see what were the subjective phenomena that Goethe described under the caption “Physiological Colors.” To avoid circumlocution we use modem terms. Goethe particularized the phe-nomena of irradiation, the spreading of white upon black, and its
appUcation in practical life. He described light and dark adaptation, but not duromatic adaptation.

He gave accounts of positive

after-images and of the flight of colors, along with statements

about the times of both of these phenomena. He stated conditions

114

'

BEGINNINGS OF VISUAL SENSATION

for negative after-images of black and gray and colors, comment-

ing on the nature of complementary hues and the complementary

halo that is seen about the stimulus-object during fixation. He also

noted the complementary after-effect of general exposure to darkor light or color. He suggested the effect of illumination of back-ground upon positive and negative after-images, in a ease where
he viewed bo& images after exposure to a single stimulus. lie described contrast effects of black and gray and colors. He discussed
the coloring of shadows in relation to after-images and contrast.
Finally he gave accounts of cases of color blindness. It is, of course,
in such a marshalling of simple data that intuitive observation is at
itsbest; thus

we may note that the addition of Goethe’s facts to

Newton’s gives us some correct information for almost every topic
about color that is nowadays worth putting into an elementary
textbook of psychology,
In Goethe’s theory of color, on the other hand, observational
intuition appeai-s at its worst. Goethe was s'h-uck by the fact thataU colors are darker tlian while. Thus it bcicauio innncdiatcly apparent to him that colors must Im a mixture of dark with light.

Noting that blue is darker than yellow, he established as his main
thesis the principle that blue and yellow aro two primary colors towhich all tire rest may bo related. Purthormore, knowing only
about the mixture of pigment colors, he pointed out that grocn isa mixture of blue and yellow. Hod (Fiirpur) he dosoi'ibod ns a“condensation” of yellow, the way yellow looks when it is very
dense, like the sun through a mist or smoke or the atmosphere atsunset. Although Goethe elaborated tliis tlieoiy with furtlier ob-

servational and argumentative detail, he added nothing that simplifies or clarifies his view.

The theory boils down to a two-color

hypothesis based on yellow and blue. To illushate the polarity ofyellow and blue Goefhe compiled the following list of comparable
dichntonv.os!

Plus

Minos

Yellow

Blue

Brightness

DarknessLi^t
WarmthShadow

ActivePassive

Force

Weakness

Bepulsion

Attraction

Iwidmity
Acid

Distance

Cold

AlkaliGOETHE’S THEORY OF COLORS

115

Goethe’s violent and unreasonable opposition to Newton wasostensibly based on his belief that Newton’s theory contradicts observation. That white is not a mixture of colors was so obvious toGoethe that he was shocked at the absurdity of any experimentleading to an opposite conclusion; sudi a conclusion, he could tellin advance, must be based on fallacy. Goethe’s behavior, nevertheless, needs more to explain it than his faith in observation andhis mistrust of experiment.

He had got interested in color quite

early. Struck with the absurdity of Newton’s view he borrowed aprism in order to test the theory, neglected the test, and then,when the owner wanted the prism back, held it up opposite a whitewall to find, to his astonishment and delight, that the wall still

looked white except at the boundaries of dark objects upon it. At

once he was certain that Newton was wrong. So shocked was hewhen a physicist assured him that Newton’s theory would indeed
require the expanse of the wall to appear white through a prism,that he set to work at once to prove Newton wrong. Hence he kept

the prism and performed various experiments of viewing through it
small black objects on white grounds and small white objects onblack grounds. Finding colors only at the boundaries and different
colors at opposite boundaries, he concluded that both white andblack yield colors on refraction, and thus anived at his notion ofpolarity which we have just noted. Newton’s experiment he nevertriedlInstead he published two brochures on the matter in 1791

and 1792, and then 1411 pages of discussion in 1810. Though Helmholtz tried to explain this strange behavior as a natural conse-

quence of the poetic temperament, that reason can account only
for Goethe’s original distrust of Newton’s theory. The intense drive,

which closed Goethe’s eyes to the logic so obvious to every physicist

whom he consulted, and which led him into this huge under-

taking in observation and publication, must have been founded

upon the wounded pride of an irrepressible ego.

Even when he was known to be wrong in his main commitment
Goethe was too important a man to be ignored. His sterile theoryof colors was cited during the first half of the nineteenth century,

while the fertile theory of Thomas Young remained unknown. It
was, moreover, Goethe’s careful observation of subjective phe-nomena that opened the way for Purkinje and Johannes Muller,
When Goethe was rebuffed by the physidste, he found a friendfor his theory in Schopenhauer, who both accepted his views about

116

BEGINNINGS OF VISUAL SENSATION

the polarity of colors and shared his dislike of Newton. Presently

Schopenhauer evolved a somewhat different theory of his own,
one which he published in 1810. He asserted that the comple-

mentaries—red-green, orange-blue, and yellow-violet—show thepolarity of colors, and that red and green arc tlie principal colors

upon which the others are based. This theoiy was admittedly intuitive, and it had little influence upon scientific tliouglit.

From Goethe to Helmholtz
While the excursions of a poet into science would seem almost
preposterous in the twentieth century, Goethe’s adventures withcolor were not so absmd in the Germany of the early nineteenth

century. In the German culture of that day philosophy and literature, not science, held the center ol Uic stage. Idealism dominatedphilosophy, and the poets Goethe and Schiller were half philosophers. hi such an environment Ilorbart could wi'itc a f’si/c/to/ogie

ds Wissensohafl (1824-1825) founded upon (‘xporicnco but not,as he explicitly insisted, upon experiment. To the modern person
outside of Germany it seems impossible Hint a Wimmcimit could

be held to be non-exporimonlal, but then Wissensclwll, never has

meant exactly science; it is a broader tci-rn for a field of syslematic
knowledge. Perhaps the lack of a German equivalent for the word
science explains in part why intuitive empirical disciplines exist

without the benefit of precise experimental control more readilyin Germany than in America. At any rate, the more one knows of

the ttmes, die more one sees that Goethe did no violence to theZeitgeist in addressing his own self-confident, egoistic insight tothe problems of evolution and of cobr.

Goethe may tiius be said to head a phenomenological tradition.
His immediate successor was Purkinje, followed shortly by Jo-

hannes Muller. Perhaps all German psychologists—

Fechner and
Wundt, for instance ^belong somewhat in diis line, yet the great
phenomenobgist of the latter half of the century was Hering.

—

Stumpf followed liim, and finally Wertheimer brought phenomenology to the world as Gestalt psychology. Tlie whole phenomeno-bgioal tradition, from Goethe to Weriheimer, is characterized bya belief in the value of the direct observation of experience and a
mistrust of the mediation of psychological fact by elaborate ex-perimentation.

PHENOMENOLOGY AND EXPERIMENTALISM

117

Thus experimentalism finds itself opposed to phenomenology.

The two are not incompatible, for all recent phenomcnologists havebelieved in experimentation and have experimented too. The tempers of the two are, nevertheless, opposite, Thus in Germany itself
a growing experimentalism largely, though not entirely, replaced

phenomenology. Johannes Muller, who began his career with somephenomenology of vision, was also an experimentalist from thestart.

Fechner was mostly an experimentalist in his founding of

psychophysics, althougli his motivation was philosophical (hewanted to relate materialism to spiritualism by psychophysics),
but he also published considerable phenomenological observationof scientific significance. Helmholtz, the greatest scientist to contribute importantly to experimental psychology, is representativeof experimentalism at its best and purest. The differences between

the visual researches of Hering and of Helmholtz are typical of thedifferences between phenomenology and experimentalism. Where

phenomenology is egoistic, asserting the validity of individual observation and insight, experimentalism is diffident, mistrusting in-dividual observation and relying upon controls, procedures with-out knowledge, and the other techniques that have been devised toacliieve assurance in the face of the unreliability of human obser-

vation.

Nowhere is the changing balance between phenomenology andexperimentalism belter illustrated than in the history of visualsensation.

Johannes Evangelista Purkinje (1787-1869), an Austrian physiologist, represents the phenomenology of vision in its best and mosteffective form. He wrote in 1819 a first volume. Beitrage zur Kenntniss des Sehens in mbjectiver Hinskht, and then in 1825 a second

volume, Neue Beitrage. This second volume contains his appreciation of Goethe, the phenomenologist. After two paragraphs eu-

logizing Zur Farbenlehre, he dedicated his own work to Goethe:“Nehmen Sie, grosser Mann, diese treue Huldigung von einem
Ihrer kleinsten, aber innigsten Verehrer." Tliat, from the lesser tothe greater man, but from the better to the poorer scientisti
Purkinje’s observations of visual sensation “in its subjective as-pect" supported and supplemented Goethe’s.

He described thephenomena that result from ‘inadequate’ stimulation of the retina
by pressure on the eye-ball and by electric currents, thus supplying
data for Johannes Muller’s doctrine of specific nerve energies. He

BEGINNINGS OF VISUAL SENSATION

118

examined the effect of dazzling li^t and its icsnlts in after-images
and the flight of colors, the effects of dark adaptation, the facts
about the blind spot, tlie relation of fixation to the size of the pupil,the phenomena of single and double vision witli the two eyes, andthe general facts of after-images and of the images of imaginationand memory. All tliis is in his first volume. Although his second
volume is somewhat more physiological, it includes phenomenological accounts of the changes in color sensitivity in indirect vi-

sion from 0° to 90° from the fovea, of true and apparent movementin the visual field and why the moving eye does not produce theperception of movement, and of the effect of strong light uponcolors.

His observations on indirect vision were potentially im-

portant, although as a matter of fact notliing much was made ofthis problem until Aubert mapped the color zones in 1857.

In the second volume (1825) tliere are throe paragraphs that
describe the change of hue and of relative brightne.s,>i of tho different colors as illumination increases from very faint light to nor-mal vision. This observation, one among hundreds and not regarded as especially important by the obsoivor himself,i.s

Iho onethat perpetuates Fuikinje’s name. Today every p.sychologist knows

what is meant by the Pwklnja plwiwimwn. wSo familiar is tho termdrat the pronunciation of tho proper narao has ovon boon anglicized. In general,

however, phenomenology docs not make forfame. The greatest discoveries are linked with hypotheses that go

beneath the level of immediate phenomenological observation.
It was the growth of experimental physiology that forced expori-mentalism upon the study of the sense of vision. Even a hundredyears after Goethe, toTitchener,

be sure, tliere were psycliologists,

like

who thought that trained observation is more im-portant than carefully devised experiments; neverdieless the big
generalizations that make up the body of scientific knowledge waitin general upon the complication of experimental technique. The

most distinguished German physiologist of the early nineteenth
century, Johannes Muller(1801-1858), began his professional

career by attacking problems of vision. In 1826 he published alarge book on the comparative physiology of vision, abook inwhich he consjdfeted the general problems of human and animal
vision, and in which he also gave his first formulation of the famous

doctrine of the specific energies of nerves. Later in the same year

he published a small phenomenological book, Ueber die phanta-.

PUEXINJE TO HELMHOLTZ

119

stischen Gesichtserscheimngen (with a quotation from Goetlie

printed before the preface)

There were half a dozen important texts in the field before
Helmholtz. Treviranus published an elaborate comparative anat-omy of the eye (1828) with exact data as to the formation ofretinal images in a wide variety of animal eyes, Heermann had atext on visual pei'ception and sensation (1835), and A. W. VoUc-

mann published a general physiology of vision (1836). In 1838came Johannes Muller’s chapter on vision in his Handbuch der
Phjslologie des Menschen, a chapter that rounded out the in-formation as of that time and cited Volkmann extensively. There

were in addition Burow’s physiology of the eye (1841), the bookthat considers the mechanisms of accommodationand conver-gence, and Szokalsky’s study of color sensations ( 1842 ) After that.

came Volkmann’s and Listing’s general accounts of vision in Wagner’s Handwarterbuch der Physiologie (1846, 1853). Helmholtz’s

researches began early in the 185ffs.

Helmholtz ( 1821-1894), as we have just noted, represented experimentalism at its best, His career as a physiologist was launchedby his measurement of the rate of the nervous impulse ( 1850) that
preposterous fact which the intuitionists of his day protested could
not be true, just as the intuitionist Goetlie had denied Newton’s,fact that white is heterochromatic, Helmholtz accepted Muller’s

principle of specific nerve energies as a fundamental psychological law of paramount importance, extending it to account for dif-ferent qualities within a single sense. Quite early(1852) hebrought forth and championed Thomas Young’s theory of color,developing it as a theory of three specific nerve energies. Then too

he reviewed the Hterature as well as accomplishing a great deal oftechnical research in physiological optics. The outcome was the

publication of the three volumes of his classical Handbuch derphyslologischen Optik in 1856, 1860 and 1866. ’The value of thisbook is attested by its translation into English almost sixty years
later(1924-1925)—

incelebration of the centenary ofHelm-holtz’s birth.

After Helmholtz
Because the great expansion of the psychophysiology of visionfrom Helmholtz to the present time prevents the subject from being traced as a whole, we must study—^inthe next chapters—the

BEGINNINGS OF VISUAL SENSATION

120

separate histories of some of the principal problems.
first, however,Wo maynote briefly a few of the major Ireiuls.

(1) There has been a huge multiplication of fact and rcsearoli.

To the second edition of Helmholtz’s Hanilhiich (1896) Kouig
added a bibliography of 7,833 titles, and no bibliography was considered any longer possible in the English edition oi 1924-1925,

Evidence of the eventual wide expansion of interest may be seenin the formation of the Optical Society of America and the many
investigations published in its Journal. There has also been some

support from American industry for research in psychophysiological optics.

(2)

The phenomenologicalattitudein visual researchwasmaintained by Ewald Hering (1834-1918). liering and Ilchnholtz, representing

phenomenology and cxperimentalism, were

the two greatest names in visual science of the hitler halt of the
century. Although later G. E. Muller came to hold lloring’s atti-

tude toward visual problems, phenomenology in the twi'ntlt'lh century has been lost in a mass of technical experimentation. It exisl.s

only in the problems of visual imrocplion that the Gestalt psychologists consider, and they owe uiudr of tlicir orientiiliou to Ilering.

(3)

The point of view toward jiroblcms of vision has

thus

shifted from the phenomenal to the physical. Ilering, G, H. Miillor

and Titohener sought to study the attributes of immodiato vi,suttl
experience, and then to find out what dimensions of the stimulus

are correlated with these attributes. Nowadays wo consider firstthe dimensions of the stimulus, and then seek to discover what
phenomenal consequences they yield. We used to inquire into thephysical cause of hue; now we ask about the effects of monochro-matic light. We used to be concerned with the crilei'ia of visual
depth; now we study the properties of binocular vision. Since weknow that the correlations between stimulus and phenomenon are
not simple (hue depends on more than wave-length, briglrtness on

more than energy), this shift to dassifleation in terms of the physical properties of stimulus

sometimes leads to a radicallynewgrouping of facts.
(4) Quantification has led to calibration.

Many facts are sosurdy and so accurately established that norms for them can beused in the computation of other results. The luminosity curve forthe brightness of spectral colors and the difforonccs between conevision and rod vision are facts which no one questions, and which

NOTES

121

modern investigators like Hecht use as the basis for quantitative
theorizing.

(5) In the late nineteenth century the chief interest in vision

was centered in the theories of color, like the Young-Helmholtz
theory, Hering’s theory, Ladd-Franklin’s theory. Almost dwindledaway now, this interest has been supplanted by a concern with theexperimental establishment of functional relations which show thedependence of a phenomenon upon its conditions in the stimulus.

A graph or an equation is the law and takes the place of a theory.
(6)

The stimulus has, in general, migrated from the external

world to the retina. In the nineteenth century the stimulus wasusually some variable object, like the papers on a color-mixer. In

the present century the optical properties of the eye are so wellunderstood that the nature of the proximal stimulus at the retina

can be predicted and used as the independent variable in experimentation. Thus Troland took as a measure of stimulus intensity
the photon, which is a unit of intensity at the retina after pupillaryaccommodation has been talccn into account.
In the next chapters we shall consider the histories of specificproblems of visual sensation and perception.

Notes
Before Newton
Here follow the more important
names, dates and works mentioned or
Implied in diis section of die text.

Alhazen is the Latin name of the
Ibn al Haitham (ca. 96S-

Arab,
ca.

losg).

Johann Kepler (1571-1030),
oUelllonem•pamUpomma,

Ad

1004;

Vioptrice, 1011.

WiUebrord SneU (1591-1826) formulated the law of retraction in 1621.

He did not publishit.

Ren4 Descartes (1598-1650), La
dioptrique, published with

DlscomcolorSms, et iride, 1685 (posthumous),
Robert Hooke (1035-1703), Miemgtaphia, 1665.
Ole Christensen R6mer (10441710) determined the velocity oflight in Paris in 1672-1676 and communicated his results to the Acaddmie

des Sciences in 1676.
Christiaan Huygens (1029-1695)
communicated his researches to the
Academic des Sciences in 1678 andpublished them inde la luTTiUre, 1690 (Eng. trans. 1912).
Edm6 Mariotte (1620-1684) de-TrM

scribed the blind spot in 1668.

de h rndthade, 1637; Piincipia philoeophiae, 1644; Le monde, written
ca. 1830, published posthumously in

the

1664.

Considemftons

There was also a book on color by
distinguishedsoientist,

RobertBoyle ( 1027-1691 ), Experiments andTouching

Colours,

1618-

1664, a date which is two years be-1663), Phystco-mathesis de lumina,

fore Newton bought the prism which

Francesco Marla Grimaldi(

BEGINNINGS OF VISUAL SENSATION

122

started his experiments. Goethe said

(1810) tliat only Theophrastos (butperhaps ho meant Aristotle) andBoyle had attempted before himself

89-93; Wolf, op. cit., 1935, 204-271;
Matdi, op, clt., Clmp. 6.

Porterfield

to describe and classify the phenom-

Some mention must be made hereena of colors, Boyle, however, although presenting a great mass ofof William Porteifielcl, A Treatise on

casual Information and opinion, seems

the Eye, the Manner and Phaenain-

to have had no great InHuence, pre-cna of Vision, 1759, 2 vols., 450 and
435 pp., respectively. This book wastlie standard and most complete workon the physiology and psychology olsumahly because he lacked a central
idea that would give significance tohis facts.

The histories of physics detail thehistory of optics

and thus the be-vision

in

tire

it as

Excellent brief English accounts arethat time

E. Mach, Trinciplea of Physical Op-

periments.

[1013], Eng. Irans. 1920, Chaps.

century,summarizing the knowledge atand contilbuUng new ex-

ginnings of ihe psychology of vision.

tics,

eighteenm

Thomas Young frequently referred to

The author miule, howno now histoiicidly importantever,

4 and 7; F. Cajori, History of Physics,
2 ed., 1929, S3-97i and esp.
Wolf, A History of Science, Technology, and Philosophy in the 16th

discovery and urged no new signifi-

and 17th Centuries, 193S, Chap, lliitems of Its p.sycluiphysio!i>gy can bo

A History of Science, Technology,

abstraoted ns follows;Acant view. Tho honk pimotmites thegap botweou Newton and Young, but
wot nut ornoial. Tho more imporiaul

and Phiasophy in the 18th Century,
Soo also Thomas
Young's lecture on tlte history of
optics, A Course of Lectures on Nalum! Phdosaphy and tlte Mechanical
1939,

Chap.

7.

1.

lleiinal image, The optics of ils

fommlioucited.

aredta'iisscd.

Keplerto

The problem of the inversion

iho imago to dismissed on llio
ground Ihnl iho mind does mil seu theofW. Wliowell,reilna 1ml coneliides ns lo lli(‘ nnliire

History of the Inductive Sdcnces,ol ohjools on the hnsis of nil the inlor-

On the anolenl^malion fiimlslied it.
2. Accommodation, Tim “ndaplntion" of tho eye lo clear vision at dif-Arts, 1807, 1, 472-483j

1847,

II,

views of371-42S.
light,

see H. Crew, in F.

Photisme

Maurolycus,

delumine,ferent distances to duo not Ui elonga-

Eng. bans,, 1940, vii-xvii.

tion of the eye-ball nor to change in“the figure of the crystalline,” but toconbaction of the

NewtonSirIsaacpublished

Newton’s Opticks was

In

1704;

and, with additions

2 ed., 1717,
end corrections,

1718; 3 ed., 1721; 4 ed,(posthu-mous), 1730; reprint, 1931.

Much

has

been written

ciliary

near vision.
3.

The two

Convergence,eyes

judge dtolanoe in terms of "llie Angle
that the Optic Axes

about

ligament

which moves the cryslalUno back andforth, being maximally conbacted formakeat thatpoint of the Object to which die

Newton and his work. The classicalbiography is D. Brewster, Memoirsof me Life, Writings, and Discoveriesof Sir Isaac Netpton, 2 vols., 1855.
See also L. T. More, Isaac Newton,

Eyes are directed.”

1034; the symposium of the History

paroni4.

Perception of distance. Six cri-teria

are ^ven! (a) the dispositionof the eye(accommodation),(b)

the angle (convergence), (c) the apsizeof Science Society, Sir Isaac Newton:(d) the"force" or sbength of color, (e) the

1727-1927,

confusion of small parts

1928; Cajori, op,

dt,.

of

objects,(acuity).

NOTESand (f) the occunence of intennediate objecta.
5.

Single field of binocular vision.

The phenomenon is not due(

Porter-123

nism of the eye (read Nov. 27, 1800),
Phil. Trans., 91, 1801, 23-88; Miscellaneous Works,

I,

12-63.

On theeighteenth century theories and re-field thought incorrectly) to a "mix-searches on accommodation, see theture” of the optic nerves, but rather

citations in the second paper.

Whilemind localizes

Young used the word accommodationa sin^ein this sense, he more often spoke ofplace in apace. This result does not

the “focal length of the eye" or used

to the fact that theanobject, seen double, income about by custom and experi-some similar

ence; Porterfield opposed Berkeley.

ploys accommodation to avoid con-0.

Adaptation.

The eyes"accus-tom” themselves to Ught, darkness
and color, although to be noticed
the change must be considerable andsudden. The after-effect for light andphrase.

The text em-

stant circumlocution.

There are four references to thecolor llieory:( 1 )On the theory ofand colours (read Nov. 12,1801), Phil Tnms., 92, 1802, 20 f.;

lidit

146 f.; (2)darkness is sensitivity to the opposite

Miscellaneous Worla,

illumination, an effect which may be

An account of some cases of the pro-due

duction of colours not hitherto de-tochange In thesizeof thepupil.
7.

I,(read July 1, 1802), Phil
Tnms., 92, 1802, 395; Miscellaneous
scribedColor. Colors depend upon vi-

brations in the retina set up by light

This is the Newtonian die^, which

Works, I, 176 f.; (3) Lectures (de1802-1803), I, 1807, 440;

livered(4) Lectures, II, 617. The reference

Tliomas Young took up.

to Newton’s theory of retinal media-

tion of the vibrations

Thomas Youngistranscribed1875 by T. Birch, Uistory of
the Royal Society, HI, 1677, 262; itis also quoted in Young ( 1 ), supra.
as of

Sir Thomas Youngs papers havebeen collected by George Peacock

Works of theLate Thomas Young, 3 vols., 1855.
These first two volumes include thescientific memoirs. In 1802 and 1803
in tlie Ulicellaneous

Young,

appointed

asProfessor

On specific nerve

vide

A History of Experimental Psy-ing,chology, 1929, 77-94.

ofNatural Philosophy at the Royal InstituUan, gave lectures

which were

published four years

laterin thelarge volumes of his A Course of Lectures on Natural PMosophy and the

Mechanical Arts, 2 vols., 1807. These
lectures are not included among theMiscellaneous Works. There Is a detailed biography:

energies,

supra, pp. 88-74; also E. G. Bor-

G. Peacock, Lifeof Thomas Young, 1855. There is aim
an incomplete reprint of three papers

GoetheJohann Wolfgang Goethe’s chief
work on color is Zur Earbenlehre, 2
vols. and plates, 1810. There is anEng.

trans.

of the first part of thevolume by C. L. Eastlake,
Goethe’s Theory of Colours, 1840.
The data as to now Goethe went towork, borrowed the prism, was rebuffed by physicists, etc., come fromfirst

"Confession”

on the wave theory: H. Crew, ed..
The Woos Theory of Light, 1900,

Goethe’s

45-78.

papers on color were separate bro-

The early paper on accommodationis:Observationsonvision,Phil

n,006-692.

chures,II,

Goethe’s

in

op.

two

cit,

early

RMr&ge xitr Opttk, I, 1791,

1792. These and Zur Farberdehrer«ms. 83, 1793, 169-181; Miscellaneous Works, I, 1-11. The impor-

can be found in various editions ofOn the mecha-

For H. V. Helmholtz’s analysis oftant later

paper is;his collected works.

BEGINNINGS OF VISUAL SENSATION

124

and olv

Johannes Muller, Zui vcrf’li'ii'lim-

atinacy, sco his leotwo of 1853On

researches,re-den PhjsioloM dcs Gnichtisinnes
des Mcnschen und dor TIrre nehst
ehwin Veisuch tiller die Scriiegiingon

Goethe’sscientific

Goethe’sscientificvisionprinted in Eng. trana. in Popular LeciuTSS on Sclentifio SubjeotSp 1873,

der Augen idwr

dm menschlio/wn

Blick, 1820; Vcher die phantastlscben

33-59,
pi. i, of Zur Faibmlehreof 920 consecutively numbered dicta. It is not easy without

Vol.

I,

consists

how dic-

lengtliy quotation to show

”839.

tatorial these dicta are. ’Thus:

we

In dress

associate the characterof tlie color with tlie character of theGesichtsenclwlmingcn, 1826; f/niid-buck dor Physiologic dcs ilensdien,II,

1838, Bk. V, sect. i.
R. Trevirnnus, Beitrdgo

G.

zur

Anaiomio und Physiologic dor Sinnasuierkeuge des Mcnschen und derThlere, 1828.

840. The female set in

Heermnnn, Die Bildung der Ge-

attached to rose-color andsea-green, in age to violet and dark-sichtsoorstelhingcn aus Cesichtsemp-

person.

.

.

youth

is

green.

.

.

.

.

People841.

ofrefine-findungen, 1835, [n.v.].
A. W. Volkmann, Nctie Bcitrdge

ment have a disinclination to colors.”
Or this! ‘Xivcly nations, the French

zur Thysiohglo des Geslehtssinues,

for instance, love intense eolors, es-soditcrbiich

peoiallyon the actlvo

nations,

like the English

side;

sedateand Ger-

und

1836;

184(1,

dark blue. Nations aiming at dignity

V.

tho

Spaniards

andllehni Atiges.

gtscJier

1842,

Soboponhauer’s

J.
(

1788-

1830] B3-page monograph on color
Is Veber das Selin und die Farbcn,
1816; later eds., 1854, 1870; Latined., 1830.

From Goethe to Helmholtz
A fuller general description of thisperiod is to be found in E. G. Sor-A

IHstoTy of Expeiimental Pauchology, 1929, 97-105, 293-295.

ing,

The books mentioned In the text
are the following!
J.

E. Furkinje, Beobaohtungen und

i,

841.

Voher die Kiiijiin physMo-findimgcit dor Fiirlion

color of their mantles to inollnc to tho

Arthur1

Szokahky,Italians for instanco, sulTcr the rod

passive side.”III,

C. A. Burnw, Brltriigc sur Phyund Physik des mensch-stahgio

appearanco,

Wagner’s Hand-

11.

der Physiologie,

264-351.

mans, went straw-colored or Icathcreolored yellow aooonipanli'd withofin

und niidmhgtsrhvr llinsleht,

B. Listing, in 11. Wngner’.s Hand-

toSiterhuch

dvr

Phijslohglo,IV,

1853, 451-504.
If. L. F. V, Ilclmhnllz, Ilandbnch
der iiliyslnlogisclwn Ojilik, 3 vols.

1807; 2 ed,
3 ed.. with
1909-1911; Eng,
trans., with furtlicr additions, 10241925. See also E. G. Boring, A History of Experimental Psychology,
42 f.. 45 f., 288-309,
For Purkinje’s life and work, see
1800,1886),(1885-1804),

1890;(1856,

editorial additions,

0. V. Hykes, The life of J. E, Purkyne,
Osiris,2. 1936, 464-471; F. K.
Studnicka,

J.

E. Purkinje’s “physi-Veriuche zur Physiohgle der Sinna,

ology” and his services to science,

2 vols. The first is BeitrUge mr Kemtniss des Sehma In mhjeoUoer lUnslcht, 1819; 2nd unaltered and more
frequent ed., 1823. The second volume is Neue Bettrdge, eto,, 1825, andcontains the brim account of the"Purkinje phenomenon,” pp. 108110. On Purkinje. the man.
(n/rd.

ibil, 2, 1938, 472-483; V. Robinson,

Me

Johannes Evangelista Purkinje. Sci.
Mon,, 29, 1929, 217-229. Purkinje’s
scientific contributions tophysiology

were noteworthy; these papers on thephenomenology

ofvisionore

only

tho first publications of a man who

had not yet

attainedrecognition,

NOTES
There

isa story that Goethe,

iin>

125

findungen:psychophysische

Unter-

monograph,suchmsen; but he wrote from thehelped him to his first position, andpoint of view of his own generation,

It iscertain that later personal ac>
quointance between the two reen-

and the book made little impression
upon the changed world of psycho-

forced a bond which at first had been

pnysiologicai optics.

bypressed

his

first

For an example of modern visual

purely scientific.

The text depicts Helmholtz andGoethe as at opposite scientific poles.
That Helmholtz also had this viewisindicatedbyhiscriticismoff^ychophysiology as classified in accordance with tlie dimensions of thestimulus and as consisting of statements of functional dependence, see

L. T. Troland, The Principles of Psychophysiology, 11, Sensation, 19^,
51-205. On the photon, see ibid.,

Goethe, cited above.

After Helmholtz

621., nof.

Haring wrote extensively on
tlie problems of visual sensation, but
his two most important boolcs are
Zur Lehre uom Lichtsinne, 1872E.

The

reason diat phenomenology

perpetually loses the battle to experiis that toe developmentof science is always toward conmll-

mentalism

1874j reprinted, 1878, and Gmndfsiigs der Lehre ooni lAchtainn, 1920

tion by abstraction. Goethe’s or Her-

(posthumous),

ing’s insightful apprehension of theG. E. Midlers

cliiefcontribution

cationand a subsequent simplifica-

visual world might yield a convL-tion

Zur

that there are four principal colors,

Psychophysik oer Gosichtsempfiodungen, 2. Pstjchol, 10, 1896, 1-82,
321-413; 14, 1897, 1-76, 101-196.

but it could never show that relative
intensltive sensitivity is minimal atan intermediate intensity and in-

In 1930,

when he was eighty years
Muller published the two large
volumes of Ueber die Parbenemp-

creases for greater and lesser intensi-

old,ties, i.e.,

to die psycholocy of vI.sion isthat toe Weber function is

so-and-so and not as Fechner thought.

Chapter 4

COLOR AND ITS STIMULUS
N this and the next four chapters we shall consider the histories of the more important problems of visual sensation, dis-I

tinguishing the problems as Aey were understood in die earlypart of the present century. At that time phenomenal experience

was believed to be the primaiy subject-matter of psychology, andphysiology a secondary consideration useful only later for the pur-pose of explanation. For this reason classifications were based upon

phenomenal characteristics, with only subordinate consideration
for the dependence of tlie sensations upon their .stimuli. In thisattempt the psychologists were not, it must be admitted, .suece!i.sful;no laws of visual sensations were ever lormnlated .solely interms of consciousness without reference to the stimuli or the

nervous system. NeverQicless, phenomenal color and brightness

remained tor a long time the important terms of visual spn.sation;and to determine tire laws of dependence of these two aspects ofcolor

upon the different dimensions of variation ol the visual

stimulus was the aim of most research.

Color and its Dependence on the Stimulus

We have seen in the last chapter how an understanding of thenature of color suddenly emerged from Newton’s discovery thatdifferent colors are immutably associated with different degrees of

the refrangibility of light, and that white is, in this sense, not acolor, but the consequence of a mixture of lights of many different
refrangibilities.

By a false analogy with tones Newton, however,supposed drat there were but seven colors, a view which seems to
imply that he believed in but seven refrangibilities. Mach thought
later that Newton must have known that the seven colors are cor-

related with an infinitude of degrees of refraction— as indeed theseven musical notes are related to an infinitude of vibration frequencies even within the single octave. At any rate, Newton did
120

ANALYSIS OF COLOR

127

not express himself clearly, and the matter went over for a century.
In 1801, however, Thomas Young, as we have also seen, realizedthat there must be an infinitude of kinds of lightand thus, as

he thought, of colors too. He conceived the necessity, therefore, ofreducing die perception of colors to a few (three) nervous processes. It

was later, about 1815, that Fraunhofer described ac-

curately the spectral lines which now bear his name. He measured

the position of more than five hundred of these lines, naming themost important ones by the letters A to G. Since the refraction ofsuch lines can be accurately determined, he used them to study the—^knowledge essential in the manufacture ofvariation of refraction

achromatic lenses. After Fraunhofer it was not possible to think of
the kinds of light as less than an mfinitude’j yet it was still not
clear how many seen colors correspond with the light continuum

that is the spectrum.

There are really three different ways of answering this question
about the number of colors, although the three were not dearly
distinguished until much later, (1)One may ask how many dis-tinguishably different colors lie within the limits of the spectrum.

Here is the problem of the number of just noticeable color differences. (2)One can, on the other hand, equally well inquire as

to how many pure colors can be seen in the spectrum. This ques-tion implies the existence of pure or elementary colors (e.g., red,

yellow), and intermediate colors (e.g., orange) that are mixturesof the pure colors. (3) Finally, one may argue as to how many

elementary physiological processes in the retina or optic nerve arenecessary for the radiation of all the discrlminably different colors. This is the problem of physiolo^cal elements. The

confusionof these three problems results from the supposition, taken for

granted by the early investigators, that phenomenally pure colors

would be the correlates of elementary physiological processes andalso the most noticeably different colors in the spectrum.

Newton thought, as we have seen, that there were just sevenpure colors, corresponding to seven kinds of light. Although heknew about the intermediary colors, as his laws of color mixture
show, he also knew that the prismatic spectrum consists of manifold overlapping images of the aperture through jvhich the lightcomes, and thus it was natural for him to suppose that the inter-mediate colors are due to mixed light.

W. H. Wollaston in 1802 was fire first person to observe andCOLOR AND ITS STIMULUS

128

describe the black absorption lines in the solar spectnim. lie meas-

ured tire position of seven of these lines, and subscribed to a belielthat the ihree most prominent divide the spectrum iuUi our fundai

mental colors; red, yellowish green, blue and violet, lie seems tohave thought of the black lines as breaks between the colors, al-though it is strange tliat “yellowish green,” a name which indicatesa mixture, should have seemed to him a simple color ^for Wol-—laston knew that the spectrum presents an infinitude of refrangibilities, and he was discussing perceived color, not light.

It was in 1802 also that Hiomas Young argued for three primary

physiological processes. Wollaston thought of his theory of four

primaries as contradicting Young’s theory of three; nor should we

expect at that time to find the physiological analysis of colors distinguished from the phenomenological analysis. Even a century
later there were those who believed that

Young’s view of threephysiological primaries must be incompatible with llie introspective observation of four fundamental hues.

In laot, most psycho-

physiological theories assume that the mind perceives only whatlire

nervous system brings oillior to It or to its part ol llu' bruin,

and thus that diero could not bo four primaries in perc(‘plicm itthere are only three in the optic nerve. (Cf, pp, (10-72, 200-200,)

Goethe’s phenomenological tlicory of color appeared in 1810. It
is,according as one interprets it, a two-color (yellow-blue) or afour-color (red-yellow-green-blue) tlieoi-y. It posits only two ele-mentary colors, yellow and blue, from which the other two colors,
red and green, are derived. Thus it has come to be regarded as theforemnner of the phenomenological four-color theories, ol which
Hering’s is the outstanding example. Goethe’s phenomenologicalfour, at any rate, helped to obscure Young’s physiological tlrrce.

About 1815, when Fraunhofer rediscovered the black spectral
lines that Wollaston had first observed, he named nine prominent,

well-separated lines by the first letters of the alphabet, charting

the positions of 565 others. His determinations meant that'there
ate more than five hundred kinds of light for each of which therefrangibility

isspecific

and accurately measurable, with pre-sumably many more degrees of refrangibility in between. Thus itbecame necessary to admit that the number of perceptible colors
is less than thenumber of differently refiungible hghts.

In the latter half of the century the problem of physiologicalprimaries became the central problem of color theory, Helmholtz

PURE AND MIXED COLORS

129(1852), in reviving Young’s theory, threw the wei^t of his opinion toward three physiological processes, a principle accepted bymost theorizing today as fundamental. Hering ( 1874), on the contrary, believing that the number of physiological processes

mustbe the same as the phenomenally primitive colors, argued for four,that is to say, two pairs, yellow-blue and red-green. Ladd-Frankhn(1893), also for phenomenological reasons, hypostasized four retinal molecules, existing at two stages of chemical decomposition,

to explain the four principal colors. After Helmholtz, however,

the theories of the perception of color and of brightness became
related and many other special phenomena were considered as

bearing upon them. As a consequence we must defer this consideration until a later chapter (pp. 219-214).

The problem of the phenomenally simple colors achieved importance because Hering based his theory on the distinction. Hering knew, for instance, that pure red is not spectral, that the best

red in the spectrum is somewhat yellowish, and he determined(1885) the proportions of spectral red and spectral violet lightsthat would have to be mixed to give pure red.

Donders (1884)
had already placed pure yellow at 582 mp, a mean of determinations tor 111 eyes tliat ranged from 572 to 594 mp.

Hess (1889)
determined the wave-lengths for the other pure spectral colors:
yellow, 575 mp; green, 495 mp; blue, 471 mp. The standard de-tenuinations wei-e made much later by Westphal ( 1910 ) : red, nonspectral; yellow, 574.5 mp; green, 505.5 mp; blue, 478.5 mp. These

are average values, subject to considerable individual variation.

The capacity of observers, however, to make such accurate ‘absolute’ judgments of the purity of the four crucial colors has beentaken to mean that these colors have a special place in the color

system and that special account should be taken of them in any

complete physiological theory.

The problem of the number of discriminable color differences
did not arise until tlie psychophysical era when Fechner had madedifferential sensitivity the fundamental problem of mental meas-

urement. Actually the number of colors could not be determinedby inspection of the spectrum; psychophysical methods were required for it. Mandelstamm (1867), the first person to experiment

upon differential thresholds for color, was followed in 1872 by
Dobrowolsky who made determinations which were cited as standard for many years, Before the end of the century there were at

COLOR AND ITS STIMULUS

130

least four other determinations. Tlie data of L. A,
ai-e

Jones (1917)

standard today. All die determinations have shown that dis-

criminability of hue is a variable function of tlie wave-length oflight, that diEerential sensitivity ispoor at tlic extremes of the

specb'um, and that there are several maxima in the middle region.
Jones found throe maxima at 588, 507 and 489 mp, where tlie differential litnen readies a minimum of 1 mp.

Their interest aroused by the charting of the differential limen

throughout the course of the spectrum, psychologists immediately

proceeded to 'count the total number of liminal steps throughout
the spectral range. This

number of sensations, which are justdiscriminably different under optimal conditions of observation,

came to be regarded as the total number of sensations. Von Kries(1882) computed that the results which are usually accepted from
Dobrowolsl^’s work imply the existence of 208 discriminably different spectral hues.

The limens found by Kiinig and Dietcrici(1884) yield a count of 235. Kiilpc (1893), however, came nearer
dio truth in his estimate of 150. Tlic high valui's of the early invosligators undoubtedly include some discriminations duo to dif-ferences in brightness, since in some parts ol

the.

spectrum thechange in brightness is more rapid than the change in hue. Jone.s’figures of1917 show 128 discriminably different hues for the

spectral scale.
Tliat the concept of a simple color had become ambiguousisobvious. It is one thing to say that there are seven different colors

or four pure colors or three elementary colors, and quite anotherto say that there are 150 discriminably different colors. Out of thisdiscrepancy there arose the question as to whether the colors tliat
lie between the principal or pure colors

are themselves simple orcompound. Is an orange from homogeneous light a psycliological
mixture of red and yellow, or is it psychologically as elementary as

red and yellow? There was a long controversy on this matter.
Kiilpe (1893), Titchener (1896)

and Ebbinghaus (1897) heldthat the intermediate colors are as simple and elementary as thefour principal colors (Hauptfarben), which form a frame of ref-erence to which the others are referred when arranged in orderaccording to their similarities. Mrs. Ladd-Franklin (1893) andlater Brentano (1907), on the other hand, were among the more

articulate sponsors of the complexity of the intermediate colors.

Bentley (1903) argued that an orange is similar to rod and yol-a

PURE AND MIXED COLORS

131

low but not composed of red and yellow. Much later, at a meeting of the American Psychological Association, Ladd-Franklin

appealed to the consensus of expert opinion by exhibiting disks

and asking for the judgments of psychologists. The problem wasnever settled. It simply disappeared. From the perspective of thepresent it is dear that the proposition was never clearly formulated, Since simplicity and complexity were supposed to

be im-

mediately apparent to introspection, no rigid criteria for either

concept were ever put forth so that the issue could be determined,or at least be given sense with reference to definitions of analysis,complexity and simplicity.

An even more famous controversy of this kind had its inception in Brentano’s contention (1907) that green is phenomenallya mixture of yellow and blue. Yellow and blue light do not give

green when mixed; Helmholtz had aheady explained why yelbw

and blue pigments, because of their physical properties, actually
do give off, when mixed, a predominance of green light. Botih

Goethe and Sir David Brewster, however, had held that the mixture of yellow

and blue is immediately obvious in a green—view which Brentano defended, supported later by E. B, Holt(

1912), This special problem has gone the way of the

mwe general

problem without solution. With the essential concepts undefined,

no experimentum cruets could be arranged. The author was once
present in a group of psychologists which included Titchenei

and Holt when this question of Ihe complexity of green came up
for discussion. These two men fiatly disagreed as to the evidence

of introspection, and there was nothing that anyone could pro-pose to bring about agreement.
In nearly all of the many researches upon color, from Helmholtz
to the present time, it has been assumed that for a given eye ffie

hue is determined when the wave-length is specified. That generality, however, has to be modified in accordance with the prin-ciples of the

Bezold-Brucke phenomenon. When illumination isdiminished, the spectral hues, if wave-length is kept constant,tend to shift away from yellow or blue, and toward red or green.
Small wonder, then, that the wave-length correlates of hue, forthe principal colors and for the number of discrkninable colors,
vary, since they have been determined without strict control of

the intensity of the spectral light.

Helmholtz noted incidentally that hue alters with intensity when

COLOB AND ITS STIMULUS

132

wave-length is constant. BcmIcI in J873 described the phenomenon

but briefly, since his cliicl interest lay in the deleunination of the
primary colors {Grundj urban) by noting which hues remain when
the spectrum is darkened. At low intensities of the spectrum it
isobvious that yellow ordinarily disappears. Brucke a little later(1878)

made a thorough study of the phenomenon for the same

purpose. Both these studies, hy emphasiziirg the fact Urat there

can be no very dark yellow, told against yellow as physiologicallyelementary. The best modem determination of that variation ofhue which is the Bezold-Briicke phenomenon is Prudy's (1929),

Brightness and Intensity
Newton, as we have seen (pp. 102-107) identified whiienesswith intensity. The gray powder, mbbtd on the floor ol his chamber and lying in tire direct sunlight, lookc'd whiter than the white
paper in the shadow rrenr it, provided the two were viewed at sucha ^stance as to render impossible their idr'iilifleation as objects.

By adjusting the Illumination the two could be ecpiuti'd. Nr'wlon
was thus entitled to group togetlier itr hi,s laws of color mixlrtro"Whiteness and all groy Colours between white and black,” lorhe had shown that position in die series black-gray-white dejreiMls
on the intensity of tire light, and that all parts ol this swies are alikein respect of dependence upon the mixture of colors.

The first effect of Newton’s airalysis of white light irrto colored
light

was to diminish the interest in white for drose who wereconcerned with the account of the nature of visual experience. It
soon became obvious, however, that, sirree a great deal of visualexperience is colorless, there are laws to bo worked out for theblack-gray-white series. Fechner established a general interest in
intensify, including the visual intensity whidr Newton had identi-

fied with the series of grays.

We find Helmholtz (1860) talking
We findseparately about light sensations and color sensations.

Bering (1874) talking about a light sense and a color sense, andnearly all of his Zur Lehre vom Lichtsinne was, as its title implies,

about the light sense. That black is a seirsation, not the absence ofsensation, was^plain to Helmholtz;

Bering too was at pains toestablish the positive sensory nature of black, since blade in his

theory is functionally symmetrical to white. The status of black,indeed, was cmdal. If black is nothing, then white is only a mix-

BRIGHTNESS VS, INTENSITY
ture

—that

is the verdict of133

Newton and of modern physics. But if

black is a sensation, as introspection seems to assert—if there canbe even such a thing as an intense black—then the light sense, theachromatic visual sensations, possess a claim for independent psychological status.

The very arguments, however, that established the blacks, grays
and whites as a qualitative series, told against the status of visual
intensity as an independent attribute. If the grays form an intensitive series, like faint-medium-strong, then black must be zero in-tensity; it must be a visual silence.

On the other hand, if the grays

constitute a qualitative series, like red-orange-yellow, then what

becomesof intensity?

Do visual sensations have no intensity?

Of this matter common sense could not judge. So much seemedobvious, however: (a) that one perceives intensity in perceiving

the degree of illumination, (b) that an extreme black is as positive an experience as an extreme white or a color, and that black

may even appear intense, and (c) that these two statements arecontradictory.

Though Helmholtz made no attempt to solve this problem,
Hering met it by the denial of intensity (in the usual meaningof the word) to visual sensations, a view which was accepted by
Kiilpe and others. To avoid the apparent absurdity that a class of
sensatioirs should exist without any degree of intensity whatsoever,G. E. Muller (1897) proposed that visual intensity exists, but is
not recognized because it is constant and never varies, MtiUer had

modified Hering’s theory by suggesting that black and white ate
given respectively by the action of antagonistic retinal processes,

and that added to them there is a constant gray, generated in thebrain, which is seen alone when the black and white processes are

in exact equilibrium (pp. 212-214). As a consequence, if intensity

were to be distinguished from the quality gray, it would be necessary for intensity and quali^ to vary independently. Muller

argued, however, that a gray could increase in intensity withoutchange of quality only if the amount of the black and white components in it can be increased together. Since there is no way of
increasing both of two antagonistic processes simultaneously, andsince the brain gray is constant, the intensity, ajthough extant,cannot be recognized.

Modem science, of course, would notcountenance the argument that a necessarily unobservable datum

can nevertheless exist, but forty years ago such an assumption was,

COLOB AND ITS STIMULUS

184

not absurd. Titchener rejected it, not because it was unreasonable, but because it was a matter of physiological speculation
rather than a direct datum of introspection ( 1908 )Titchener seems at that time (1910) to have believed, without

much evidence, that intensity and the quality of the gray scries
exist and vary together from black to white. lie even put Gates(1915) on to determining die differential thresholds for intensityand quality for the same stimulus variables (different illuminations of a white surface) in hopes that different limens for the two
attnbutes would be found for the same illumination, thus show-

ing a change in one without a change in the other. The results,

however, were inconclusive.

Then Stumpf (1917) suggested that intensity is found to increase with any excitation of the dark-adapted eye; in other words,

the zero-point is the gray of dark adaptation, and a change to awell-saturated color or to white is an increase in intensily, whereas
is represented by the dcvialion among theDimmick lound experimentally (1920) thatabsolute thresholds for black and for while can be dotmuiued in
the middle of the bkek-gtay-white series, so that this serii's may bequalitative change
colors.

Alter

tliat

regarded as having a zero at middle gray with increasing blackin one direction and increasing white in the oilier, just ns Ihi' lilue-gray-yellow line of saturations lying between these two comple-

mentaries has a zero in its middle. In the scries of gi'ays‘loss

white’ does not moan ‘more bkek,’ nor conversely.

Thus Titoliener (1923) was able to propose as a now solutionthat Muller’s constant gray is the minimum ( arbitrary zero ) of thevisual system, and that all lines from gray to white, black, rod,orange, yellow, or any other hue represent intensitive increases atthe same time that they show quahtative changes. If gray could

be taken out of the color solid (pyramid), Titchener said, then the
figure would become a hollow surface oriented with respect tothe six principal colors—^bkek, white, red, yellow, green andblue. The center could then be thought of as zero-intensity, andintensitive lines could be imagined drawn radially from it in every

direction within the solid, like a pin-cushion with pins

on top,underneath and all around. This view almost amounts to a resolution of both saturation and brightness into intensity, except that

Titchener clung to his belief in a covariant quality which appears

because the constant gray is added to the intensitive series,

DOUBLE REPRESENTATION

135

After Titchener the problem evaporated. The analytical phe-nomenologists lost faith in introspection as a means for deter-mining the nature of the sensory attributes, and more technicalmethods came into use. Most psychologists, surrendering phenomenology and coming nearer to Miiller’s point of view, regarded intensity simply as the correlate of degree of excitation.

For a three-color theory the intensity of a white would be thesum of the intensities derived from the three excitatory processes.
In a four-color theory, an orange would depend for hue on therelative intensities of red and yellow excitatory processes, and forsaturation on the total intensi^ of the two processes.

While all this was going on, the German phenomenobgists werecoming to a different solution of the problem by turning their attention from the simpler problems of sensation to the broader
field of perception. Katz

(1911), working in Mullers laboratory,brought out the distinction between surface colors and film colons,
along with the fact that surface colors designate an object and tend
to remain constant in the proper character for the object in spiteof changing illumination. The observer, Katz showed, may also

be aware of the intensity (or the color) of the illumination; inshort, hemay perceive an object of one bri^tness and hue illu-

mined by another intensity and hue. This dual perception comes
about when there are sufficient additional cues to give the observer
object-knowledge and to throw him into the attitude which helps
to maintain constancy of perceived color. When, however, he loses

these cues by viewing the object through a small hole (“reduction
screen”) so that the perceptual datum is no longer an object ora surface but only a patch of film-color, then the separation of
constant color and intensity of illiunination fails

and the per-ception is unitary. Seen through a reduction screen, the illumi-

nated black lies above the shaded white in the series of grays,
as Newton had found when he destroyed the object-character of
his gray and white by viewing them at a distance. Buhler (1922)

achieved a very convincing validation for this kind of perceptual
analysis.

The phenomenobgists did not, of course, bring intensity badk
to vision as an attribute of sensation. They had little use for at-

tributive analysis,

They showed, nevertheless, why it was neverpossible for most psychologists to accept Bering’s dictum that

there is no visual intensity. Intensity of illumination is actuallyCOLOR AND ITS STIMULUS

136

perceived, and so arc blacks and whites.

It ispos.siblc to .sec a

shaded white and an illuiniiiod black, in which the shade is daikcr
than the illumination and the wliite lighter than the black. Sucha double peiception depends on the altitudes and knowledge ol
the observer and otlier factors which enter into perceptual con-The

stancy.

attributive duality ol quality

and intensity that

Titcliener tried to save lies really, not at tire sensory level, birt at—

the perceptual level

^the

level

concerned less with immediate

sensory experience than with the organism’s awareness of its en-

vironment and its adjustment to it.

Weber’s Law
While the phenomenologists were fussing over the question as
to whetiier visual sensations have any intensity, the psychophysioists were busy measruing visual iiitciisily

law

Weber’sofintonsitivc

and deciding whether

discrimiiiatioii

appliestovision,Weber’s law by its essential nature imjilics u quantitative scalethat has zero at one end, and that is irreversible in respi'ct ol ‘more’or less.’ Such a statement is not tnio ol a quanlitallvr' .scale likethe oranges, where what is called ‘more yellow’ could equally well

be called ‘less rod.’ For the grays it was not doubled that thedirection of white is the direction of “more,’ and that the zero endof the series must be in the blacks. It was, at any rate, easily estab-lished that the differential throsliold increases as

one proceedsfrom black to white or from lass illumination to more, so that tireessential princrplo of

Weber’s law can be seen to apply. Evencasual observation serves to show that one candle added to two

makes more change in the illumination than one candle added
to ten.

Thus it was natural enough, with the great interest that

Fechner had aroused in Weber’s law, tliat the psychophysiersts
should take the Intensity of visual sensation for granted and inquire into the validity of the law.

The initial research on differential sensitivity to brightness, how-'ever, antedates Weber’s law. Bouguer in 1760 was the first to per-form the shadow experiment. Two candles project shadows of arod upon a wlrite screen.

One candle is moved away from thescreen until the shadow that it projects

isonly just noticeable

against the background of the screen which is illuminated by bothcandles. Since the difference

between the illumination of theWEBER’S LAW

187

shadow and the illumination of its surroundings is, of course, theillumination given by ibe more distant candle that projects the

shadow, it is easy thus to express the just noticeable difference as
the ratio between these two illuminations. Bouguer discoveredthat this ratio is approximately constant for any pair of distancesat which the two candles are adjusted, and his observation set theratio at Yu; that is to say, the shadow was just noticeable when

the far candle was eight times as far from the screen as the near

A As used by Masson 1645). The sector as drawn(

is

6° and would make ating tliat difiored from its background by 'Ao
B.

As used by Ilelmhollz (18G0). The three radial lines would, as drawn

here, give Weber flections of about ym. Vino and Vino. The outside ring would

be invisibici die inside ring should be clear under most circumstances
C. As recommended by Tilobenet (1901). The disk has more rings, more
finely scaled.

candle. Ho concluded: "the sensibility of the eye is independentof the intensity of the light,” thus anticipating Weber’s law by

seventy-four years,

Foohner (1858), repeating this experiment with Volkmann,made the fraction only %oo' He also described the cloud experiment, in which the observer finds a just noticeable difference be-

tween a bit of cloud and its backgi'ound and then observes it
through various densities of gray glass to find that what is justnoticeable at one Intensity is likewise just noticeable at another.

With a fixed ratio' for the stimuli the differences in sensation remained the same. The astronomer Arago had also repeated the
shadow experiment (1850), finding under optimal conditions,which involved a moving shadow, a fraction of only
Another experiment had been made by Masson in. 1845 with thedisk that is named after him. (See Fig. 9.) Helmholtz later de-signed this disk with an interrupted black radial line. The parts ofthis line, mixing with the white of flie disk, darken the field slightly.

COLOR AND ITS STIMULUS

188

The effect is greatest near the center, where the width of theblack line is greatest in relation to the circumference with which
it is mixed. If the conditions are right,

the observer finds the outerring invisible, and some inner ting that is just visible. With theFig. 10.

Kamo’s Data fob Diffeuiintial Sensitivity to Bbigiitness(1888)The graph is plotted from the data for Kbiiig’s eye for just noticeable
differences, Jr, for intensity ofwhite Hght, r. The values of r run from0.0082 to 34580. meter-candles and are plotted against log r in ordertoget them within the compass of a igraph. Weber’s law requires a horizontal
straight line and Is

apmoximated between 1 and 3 for log f, and roughly

breahs down entirely between —2 and0, and we
now know that the slight rise between 3 and 5 is to be exiiectcd withmany different kinds of data.

between 0 and 5.

It

disk of Fig. 9A Masson found that sensitivity varied fromtoyiao according to illumination and other conditions of visibility.

Helmholtz (1860) “on bright summer days near a window” usedthe disk of Fi^. 9B to get, "for a single instant” on shifting
to the ting in question, a fraction of only

his gaze

More consistently

he could see at the window the ting for which the ratio

was K 33

or in the interior of the room the ring for which the ratio,wasCOLOR MIXTURE

189

It was plain that Weber’s law does not hold exactly, sincedifference in illumination alters the ratio.

Aubert in 1865 showed how great the variability in the ratio
can be, when he obtained valuK from Ys at low intensities to

Yus at higli intensities. Much later (1888) Kiinig and Brodhun
undertook a very thorough study for white light and various
monochromatio lights, in which tie average ratios vary from alittlemore than % for minimal intensities to about Y^o, a minimum

fraction that occurs at less than the maximal intensity. For greater
intensities

the ratio increases slightly again. (See Fig. 10.) In

general these data have been shown to agree surprisingly wellwith Aubert’s and also with the recent investigation by Blanchard(1918). The shape of this function has led to the common statement that Weber’s law does not hold for the extremes of intensity.

The most recent view, however, is that Weber" s law does not holdat all; the middle portion of the function which, being horizontal,

approximates Weber’s law, is after all a consistent part of the total
curve, which in no way could be said to approximate horizontal
linearity.

Color Mixture
The facts of color mixture assumed importance in the 1850’s
because Helmholtz and Maxwell made them the basis for thetheory of color vision.

As we have seen (pp. 103-106), Newton established the fundamental principles of color mixture—that every color has a comple-

mentary, with which, when mixed in the right proportions, it gives

white ( gray);that the mixture of other colors gives an intermedi-

ate; that the intermediate is poorer in saturation the farther themixed colors are separated in the color series. As a schema for
determining mixtures

Newton constructed a color circle(Fig.

11). The seven colors are arranged about this circle subtending

distances proportional to the musical intervals of the octave. The... G are analogous to the musical notes of the octave.
Newton said that the non-spectral purples lie at the end of theletters A.

violets and the beginning of the reds, a remark which shows theconfusion in his bought as to whether there ware only sevencolors or more than seven.

White (gray) lies at the center, 0,from which the radii measure the ‘stren^h’ of the colors. Newtonthou^t of the pure spectral colors as concentrated at p, q, n,

.

.

.

COLOR AND ITS STIMULUS

140

a circle proportional to the

If a red is to be mixed witli a green,amount of red should be drawn at p, and another circle proportional to the amount of gi'een at s; tlicn tlie center of gravity ofthe two circles on the line ps represents tire color of the mixture.

In tliis way the schema suminarizes botli of

Newton’s proposi-tions; themore remote tlie col-ors mixed,

the weaker (nearer

thewhite)

resultantmixture;when tire colors are max-and,imally remote (complementaries,
opposites in the circle), they may

be “weaken’d till they cease andthe Mixture becomes white or
grey.”

Fio. 11,

Newton’s Coton CinouE(1704)

The

A

practice,

cotG,
respond to the notes of iho musicaloctave, and the seven colors ate
letters,

Newton conceived of this diagram as accurato enough lor

.

.

.

proportional to the seven intorvals
In the octave. Tlie purples near

doubtful about getting tut t'xact
,

»

i

.

.

,

wlillO from tWO COmplemeutaiTeS,

D Ho said; "If only two of tlte pri-cre not in the spectrum. Hie cm^

0, IS white or gray. In mix-ler,though not matheiiiali-«illy ttcciiralo.” lie was, in fact,

Colours which ill the circle.11,tuie Uic amounts of tho diiFcrcut

opposite to one another bobymixed in equal proportion, thecomponents

arerepresented

cirofes ol proportionate.

.

,

ste at p

X respectively, and the result-ant is supposed to he at the ecuter of gravity of the set of

com-

^

mixture] shall faU
^

r\

^

1

upon the center O, and yet the
Colour compounded of those twoponents.

jjg perfectly white,butsome faint anonymous Colour. For I could never yet by mixing only
two primary Colours produce a perfect white. Whether it may becompounded of a mixture of three taken at equal distances in thecircumference I do not know, but of four or five I do not muchquestion that it may.” And there Newton left the matter.

With these remarks of Newton’s in mind, Helmholtz in 1852
undertook to test the laws of color mixture, thinking that he could
thus establish- a basis for a physiological theory of color along tlie

He arranged to view througha telescope two complete spectra, at right angles to each otherlines suggested by Thomas Young.

and superposed one upon the other. Such an amingement gives a

COMPLEMENTARY COLORS
field which includes

141

every possible paired mixture of all mono-

ohromatie lights, and, except for the fact that relative intensities
are not controlled, it might have been expected to show a plotof the oomplementaries as a gray curve in the field. Helmholtz

varied the intensity and, by removing his eye some distance fromthe eye-piece of the telescope, was able to limit inspection to avery small bit of the entire field. In this fashion he observed thata yellow and an indigo, both exactly localized with respect to the

Fraunhofer lines, give a white, although all the other dual mixturesthat he examined seemed tinged with color.

Although this experiment failed to establish the law of complementaries, the discovery that yellow and indigo mix to make whitebrought up the question as to why the mixture of yellow and blue
paints makes green, a fact which had been known to painters for
centuries and which was an outstanding example of the inexact-

ness of Newton’s laws, for Newton had not distinguished between

mixtures of pigments and of lights. In this paper Helmholtz gave
for the first time the correct reason why yellow and blue paints

mix to give green. He noted that, in the mixture, most of the light
penetrates a little way below the surface passing through particles of each of tlie pigments both before and after reflection. The

yellow particles let through red, yellow and green light, whereas
the blue particles let tlnough green, blue and violet light, withthe result that die blue particles eliminate the red and yellow fromthe yellow particles and leave the green, and the yellow particles
eliminate the blue and violet from die blue particles and leave thegreen. Since the green is the only light that will pass through bothkinds of particles, there is a great excess of green, diluted by whatever white is produced by the small amount of yellow and bluethat finally get reflected. This conclusion led iHelmholtz to lay

down the general rule that the laws of color mixture cannot bedemonstrated by pigments but only by lights, a rule that for the
first time made possible the establishment of Newton’s laws withexactitude. In his first paper, however, Helmholtz found only thisone pair of complementaries, yellow and indigo.

The next year, 1853, Grassmann pointed out that Helmholtz’s
data implied the existence of exact complementaries for all colors,even though Helmholtz himself had experimentally establishedonly one pair, yellow and indigo. Grassmann showed that Helmholtz had gotten mixtures according to the principles expressed:.

COLOR AND ITS STIMULUS

142

in Newton’s color circle, and, that although Hehnholtz did not
ordinarily get exact whiles, still his results indicated the directionof change in the mixture which would

have been necessary to

make the mixture pass through white. Grassmann posited as a law
this: "that, if one of two mixed lights is steadily changed while theother remains unchanged, the impression of the mixture itself isalso steadily changed." Thus, wi&out any

new experiments, hecould apply a principle of limits to Hehnholtz’s data to establish

Newton’s law of complementaries.
Helmholtz, accepting Grassmann’s criticism, in 1855 worked

out the first table of exact complementaries (see also Fig. 12)
Complenientaru
Color

Red
OrangeGold yellow
Gold yellow
Yellow

Yellow
Green yellow

Wnoe-lengi/r

Color

2425
2244
2102
2120
2095
2085
2082

Green blue

Wave-length

Blue
Blue
Bluo
Indige blue
Iiullgi)

bluo

Violet

1818
1809
1793
1781
1710
1700
Irmu 1000 on

The figures for wave-longlhs arc in millioiilhs of a Paris inch, Themillimicron as a unit came into Gomiany with the inolrie systema few years later. In the second edition of his OpUk (1806) Helmholtz could show that these original detonninalions of his werevery close to the later and supposedly more aeairale ones by

von Frey and von Kties ( 1881 ) and by Konig and Diotorici ( 1887 )In fact, there is little dillerenco in these results from the mostrecent figures founded by Sinden (1923). Differences between

observers are greater than any error which tliere may have been
in Helmholtz’s measurements of 1855.

Various authors have staled different sets of the laws of color
mixture. In general, however, there is agreement that the important laws are the two of Newton’s: ( 1) the law of complementaries

and (2) the law of intermediates. What is sometimes called thethird law is the principle diat (8) colors enter into composition

no matter how they are composed. This law is due to Grassmann(1853):“Two colors, each of which has a constant color tone[hue], a constant color intensity [brightness]

and a constant in-tensity of intermixed white [saturation], also give constant mixed
colors,no matter of what homogeneouscolors they arecom-

posed." Helmholtz said, less generally. "Colors that look alikeCOLOR MIXTURE

143

mix to give mixtures that look like them.” Tilchener said, “Themixture of mixtures that match will match either of the original
mixtures.” The law is important since the stability of the world ofFig. 12.

Helmholiz’s Graph of Complementary Colors ( 1855 )The corves show the relation between pairs of complementary spectral
colors. The scales are in millimicrons, the later unit or wave-lengm. The
complementaries of the greens are the purples which, being non-spectral,
do not appear on the chartcolored objects depends upon it, although its validity is, of course,
limited by the Purkinje phenomenon.

Grassmann also laid down what might have been galled a fourth
law of color mixture: (4) "The total U^t intensity of the mixture
is thesum of the intensities of the mixed lights.” This law is rec-ognized as valid today to the extent that the addition of any

COLOR AND ITS STIMULUS

144

colored light to a mixture always increases—never decreases—thebrightness.

Although Helmholtz’s name stands out in the researches upon

to time, very important is the work of the brilliant andcolor atyoung J, Clerk Maxwell (1831-1879), who conflnned llclmhollz's
findings

on color mixture (1855, 1860), repealed Helmholtz's

argument about the mixtiue of yellow and blue pigments to makegreen, espoused with Helmholtz the tluree-color theory of Tliomas

Young, worked out a practical system for predicting color mixtures, and developed tire method of mixing colors by the rotationof colored sectors on disks.
Altogether there were at that time three principal methods of

mixing colors. The best method, advocated by Helmholtz, consisted of mixing

pure spectral lights. An optical system with aprism, similar to the one shown for Newton in Fig. 8 (p. 104)

was so arranged that most of the colors could bo iiilerriipted, thechosen colors be loft, allowed to recombine, and viewed projected
upon a sercon or through a telescope. This is the improved methodthat Helmholtz used in 1855 to correct his Itat results, the methodthat was used in the better quandlativo researches by Kiinig andothers, and the best method today.
There was also the metliod of mixliiro by transmission andreflection, a method originated by
H. Lambert in 1760, The obJ.
server', 'viewing one color obliquely tlirough a glass plate, sees an-other color reflected from the gl^, the two superposed. Helmholtz, when he described the method, pointed out that it could be

used with colors obtained by white light passed through liquid
filters.

This technique is common today witli plate glass or half-silvered mirrors in a wide variety of situations which require tire

combination of two visual fields. The half mirror is set at 45° to theline of sight, so that one field can be seen directly tlu'ough it andthe other, at right angles to the line of sight, as reflected horn it.

Of course the simplest method of mixture is the combination ofcolors as sectors of a disk which rotates so rapidly tliat the colors
fuse. This method was first employed by P. van Mussohenbroek in

1768. J. Plateau ( 1829 ) and H. F. Talbot ( 1834 ) used it for photo-

metric purposes. Maxwell (1855) invented the colored disks withthe radii cut so that the disks can be fitted together and the resultant sectors varied at will—the device familiar to every student

of elementary experimental psychology. For years they were calledCOLOR MIXTURE

145

Maxwell’s disks. He also invented a top that would carry the disks

and spin for a long time. Later color-mixers were spindles driven
rapidly by a belt from a large wheel turned by hand. Nowadays

the electric motor does the work.

That this method of the mixture of colors by rapid succession
should be called in question was natural. Helmholtz had shownthat the laws of mixture break down for mixed pigments, and succession is not even a true mixture. To settle this matter an appeal
was made to what came to be called the Tdbot-Plateau law, Pla-teau it was who had really first laid down its essential principle inan obscure paper in 1829. Next, Talbot had established it for use in
making photometric matches in 1884, after which Plateau had discussed the matter and formulated the law in 1835. Plateau said: “Ifan illuminated object affects the eye with regular intermittance,

and if the successive moments of its appearance lie so close to
one another that the eye can no longer discriminate among thembut receives an uninterrupted sensation,then the apparent brightness of

this object is weakened as the sum of

the durations of the presence and ab-

sence of the phenomenon
duration oi theisto thephenomenon alone.”

The principle involved is briefiy this.
The effect of a brightness or color, thus
brieflypresented,

is

proportional tothe intensity and also to the time ofpresentation, so that there is no change
if

an intensity, for example, is halved

Helmholtz's
Color Circle (1860)
Fio. 13.

but maintained twice as long. The general formula is: light of an
intensity a, acting through the time t, produces the same effect aslight of the intensity a/n, acting through the time nt. Mrs. Ladd-

Frankhn noted in 1M2 that this is a famfiiar law of chemical action.
It had, nevertheless, been

accepted with considerable hesitation

until Lummer and Brodhun(1M9) showed photometrically thatthe error at most is not more than two pet cent.

Color Diagrams
Newton constructed his color circle (Fig. 11) to summarize thefacts of color mixture.

Although it also showed the relations of

COLOR AND ITS STIMULUS

140

similarity among the colors, its primary purpose was the predictionof the results of mixtures—an approximate prediction only, since

Newton did not regard this diagi'am as working with exactitude.
It was Thomas Young (1801) who fixed attention upon tliat im-

Fib. 14.

Maxwell's Colob Tbiangle ( 1855 )Maxwell showed the color circle with the triangle within it. The positionsof various pigment colors are indicated, and the coefllcicnts indicate tile
strengths or me colors, thus implying a third dimension to the system.

portant consequence of Newton’s discoveries, tire fad that all thecolors can be had from a mixture of three. Thus Young thought ofthe color figure as a triangle rather than a circle, for, if three colors

be chosen as primaries within Newton’s circle, then all their mixtures will lie within the triangle formed upon them.
J.

Clerk Maxwell (1855) was the first person to undertake aquantitatively exact formulation of the laws of mixture. Having

worked out equations for the mixtures of colors, he represented the
mixtures within a triangle, each lying at a center of gravity on aline between the colors mixed.

He discovered here that he had toCOLOR DIAGRAMS

147

lake account of the intensity of the colors by attaching a numericalcoefficient to each. In this way he implied the fact, recognized byeveryone shortly thereafter, that thesystem of colors, being tridimensional,cannot be represented by a

/C--9^^^\oiwnge

plane figure. See Fig. 14.

With the triangle coming to beviolet*^''accepted as the figure for mixtures

and wiffi quantification being rec-Helmhol^s Coioa

ognized as the ideal, the question

Tmamcle (1860)

arose as to where the spectrum liesin the color diagram. In

The

forerunnerofKSnig’s

triangle in Fig. 16 .

Newton’s

figure, the spectrum was the circle. Helmholtz ( 1860), recognizingthat the spectral colors lie at different distances from central white—that a Ulde yellow, for instance, will cancel a great deal of violet— drew the spectral diagram as in Fig. 15.
Konig and Dieterici made the most careful measurements ofspectral mixtures in 1892, and Kiinig’s triangle has since been ac-

cepted as standard. See Fig.
16.

In

this

diagram, where

the spectral wave-lengths havebeen carefully plotted, the locus of the spectnim is shownas lying within an ideal larger

triangle ofmore thantrallysaturated

shape

of

the

spec-

colors.

The

spectrallineshows how much oversimplified was Newton’s generalizaFjb. 16. Konig's

Color Tbiakgle

tion that mixed colors axe less(1892)

saturated

The heavy line shows the locus of
the spectrum within the large theoretical triangle.

The letters on the spec-

tral line are forthe positions of thethemore remotetheir components In the color
series.

Paralleling this interest in

Fraunhofer lines. Since the figureisaccurate for mixtures, the seatingoS

the making of a diagram to ex-

spectralpress accurately the facts ofof wave-lengths
line

is

along

the

very irregular.

color

mixture, 4here

was atrend toward the construction of a figure to show the phenomenal
relations of the colors to

one another. Actually Newton’s circle

shows these relations, yet with the omission of important facts.

COLOR AND rrs STIMULUS

148

There is die fact that red, yellow, green and blue occupy crucial
positions in the coloi system, and die furUier fad that black andgray need to be included as well as white. The first fact could betaken into account by subBLACK
stituting a square lor theciicle 01 tiianglc; the second

could be lepiesonted by extending the figure in thethird dimension.
T.

H. Lambeit in 1772

represented the colors in apyramid with white at theapex and the colors around
BUJe

ORANGE'

die

base.

Wundt

once

(1893) showed die system
as a cone, with black at theFig, 17.

Wundi'6 Color Coheapex and the color circle as(1893)

the base (Fig. 17). Thesefigures indicate the fact that the number of colors hills off u.s tho

system is made brighter in approacliing white or daikcr in approaching black. Thus Wundt’s more usual diagram (1874 ol se<[,)was a sphere (Fig. 18) with white at the lop, black at the bottom,
the grays falling along a vertical axis, and a horizontal bisecting

plane as the color circle.

The first figure to take account of the crucial position of the four
prmcipal colors was constiucted by the painter, P, 0. Runge, in1810 (Fig. 19). His diagram wastheforerunner

of

the

doublepyramid or octahedron so familiar in textbooks today. The mod-ern double pyramid was intro-

yeluo

duced by Ebbinghaus (1902).
He made the base square, buttilted it so that ihe best yellows,

being relatively blight, should benear white, and the best blues,

being relatively dark, should benear black. He also blunted the18.

WUNDI’S COLOB SbHEBE(1874)

sixcomers for the reason thatpoints of change are not sharply defined. See Fig. 20. Such a diagram does not serve to predict mixtures; it is a purely phenomenO'

COLOH DIAGRAMS

149

logical representation. Red and green, although not complementaries, lie opposite each other,

Nor do the lines represent the numberof dlscriminable colors that lie along them, nor (as in Konig’s tri-

angle ) the loci of two-color mixtures. Thus, because they represent
different sets of facts, the double pyramid and the triangle haveboth persisted in systematic psychology.
Except as pedagogical devices the diagrams no longer seem important. The facts of color-mixture are better expressed by graphsof functions plotted against standard physical measures than by

PYBAMm(1810)(1902)

Kdnig’s triangle, where wave-iength and energy vary in accord-

ance with no simple spatial rule. For a while Ebbinghaus’ double pyramid represented the last stand of the phenomenologists
against the encroachments of the nervous system upon psychol-ogy: here in the color pyramid, it was argued, there is at least one
fact that is independent of both the stimulus and of physiology.

That there are but few psychologists any longer to cherish such alast leaf on the tree of mentalim goes to show how phenomenology perpetually, in the development of psychology, loses thebattle to experimenlalism.

Notes
Color and Its Dependence
on the Stimulus

dispersive powers,
flection,by prismaticre-Phil Ttwis., 92, 1802, 36&-

was published between
and second papers oncolor theory. The observation about

380.

It

For refearences to Newton, Youngand Goethe, see the text and notes orYoung’s

the preceding chapter.

the black absorption lines separating

first

A

the four

method of examining refractive andpp. 378 f.

W. H.

Wollaston’s paperis:fundmental

colorsisonCOLOR AND ITS STIMULUS

150
J.

Fraunhofer’s paperis:Bestim-72-91 tlie first two papers mentioned

mung des Brediungs- und Farben-

here.

zerstreuungs-Vermagens verschiedener Gkssarten, in Bezug auf die

colors has been still further contused

achromatischer Femriihre, Denhchr.
Acad. Wise, Mimchen, math.-natur-bterature die foUowing

The problemofthe elementaryby its terminology. We have iii lliis
words and= primal color =wlss. Cl, (1814-1815), 5. 1817, 193-

meanings. Urfarbe

226. See esp. on the black lines, pp.
202-204, and Plate II.

primitive color was used by Hering

Because the idea was incorrect andsterile, the teat makes no mention of
Sir David Brewster's view that sun-for die physiological elementary colors, but unfortunately used hy West-phal and others in the sense of Hauptfarbe (Infra), and hence so definedcomposed of three kinds ofby H. C. Warren in his Dietionanj

light! red, yfflow and blue. Brewsterof Fsydtolosy, 1834. Houptfarbe
fundamental color is practically thelight isshowed thatof these threeglassescolors might completely absorb the

spectrum, and that all the visible colors were the result of different combi-

nations of diese three lights. The theis a noteworthy instance of thetendency to refer the characteristicsof physiological phenomena to theorynature of the physical stimulus, but

=

same

as ?rinzlpn!/arBe=principa!
and is generally used for thefour (or three) ‘pure’ colors which
form the frame of reference in aphenomenological system of color
color,

similarities,

Ormdfarbe

like

=

the

color

square.

nriniorp color is a term

used by Helmlioltz,

Much and Eb-

ignored the essence of Newton’sbinghaus for any oiio of the throe

A Trea-colors whioli are basic to a systemtise

on Optics, 1831, Cliap. 7. In
see
Helmholtz, Ueber
Herm D. Brewster’s neue Analyse dcs
Sonnenliohtes, Ann. Fhus. C/iem.,
162, 1852, 501-523, which also givesof mixtures and which can tlius givecriticism,

all the colors.

it

discovery. See D. Brewster,

the

other

references

toBrewster’sIlorlna’s refotonoo ofyellowislincss of1874 to dio

spectral rod

isin

108 of 2 od., 1878).
For his determination of the amounts
toe.

clt,

ip.

of spccbal red and bluo in pure red.

theory.

On H. L. F. V. Helmholtz’s es-

see his Ueber Individuelle Verseliied-

pousal of the 3-color theory, see Iris

enheitenUeber die Theorie der zusammengesetzen Farben, Ann. Fhys. Ch^.,

6. 1885, 142-198, esp. 162, For F. C.

desFarbensinnes,

Lotos,

inDonders’ determinations of Urgelb,
see his Farbengleichungen, Arch.

his Wlssenschaftliche AbhandZungen,Physiol. Leipzig, 1884, 518-552, esp.

II, 3-23 ) , or the Handbuch der phys-533,

iologischen Optik, II, (1800), 1807,(or the reprint as 3 ed., 1911, orHauptfarben, see his Ueber die Farb-

the Eng. bans., 1924), sect. 20. For

Ophihttl. Berlin, 35 (4), 1889, 1-02,

E. Hering’s 4-color theory, see his
Zur Lehre eom Lichtsinne, 1874,e^. 20 f. The standaM determinations at the present time are from H.

163,

1852,

45-88.

Mltffreilvmg 6.

Franklin’s(reprinted

enslnn bei indirectem Selren, Arch.

For Christina Ladd-

4-colortheory,see

herElne neue Theorie der Lichtempfindungen, Z. Fsychol, 5, 1893, 211221, (hi her theories of bght-sensation.

For C. Hess’s values of theMind, ms.

3,

1892, 473-489;

or better, the various papers reprinted
in her Colour and Colour Theories,
1929, which reprints on pp. 219-230,

en der Urfarben, Z. Sinnesphyslof,
44, 1910, 182-230. Westphal discusses the history of this problem,

pp. 182-187.

The references to the researches on
and thediscussion of the number of disoriminable colors are as follows: E. Mandifferential color sensitivity

NOTES
delstamm,

BeltragPhysiologie

zurder Faiben, Arch, Ophthd, Berlin,
13399-408i W. DoBdtiEge zui physlolo-

1867,

(2),

biowolsky,

gisohen Optik, ibid, 18(l\ 1872,

151

upon the solution of the
problem and further discussion of it
and its hlstoiy, see E. M. Alspach,directed

Simplicity

of color hues, Amer,J.

Psychol, 27, 1916, 273-282.

On the problem of phenomenal

58-103, esp. 66-74; J. v. Rties, Die
Gesichtsempfindungen und ihie Ana-

green as a psychological mixture ofArch, Physiol,, Leipzig, 1882,

yellow and blue, see Brentano, op.

lyse,

A. K5nig and C.
Dieterici, Ueber die EmpSndliebkeil
des normalen Auges fur WellenlangeSuppl. Bd., 57;

Unterscblede

des

Arch,

Lichtes,

Ophthd, Berlin, 30 ( 2), 1884, 171184

in(reprinted

Ges,

Konig'sAbhandl,, 1903, 23-33); 0. KiUpe,
Outlines of Psychology(1893),
1895, 127; L. A. Jones,

trans.

The

fundamental scale of pure hue andretinal sensibility toI,hue differences,

1-50, 129-161, although thecit., esp.

entire book is really about this matter.

E. B. Holt supported Brentano,

New Realism, 1912, 332-385. Again
see Alspach, op. cit., esp. 280-282.

On the Bezold-Brilcke phenomeW. V. Bezold, Ueber das
Gesetz der Farbenmischung und dienon, seephyslologischen

Grundforben, Ann.

Phys. Chem., 226,

1873, 221-247,

Bniidre, Ueber
Empfindung im Gebiete des237-239;esp.

E.

apt. Sac, Amer,, 1, 1917, 63-77.

einigeTTie discussionof simplicity vs.

Sebnerven, Sitzimgsber. Akad. Wise.

that are notWien, matb.-naturwiss. Cl., 77 (3),1878. 39-71; D. M. Purdy, The
Bezold-Brilcke phenomenon and contours tor constant hue, Amer. I.

complexlyforcolorsUttuptlarben Is widespread, but thefallowing references snow its natureand its dates.
belongs

It ispeculiarlya problem thattotheperiod1890-1910, when inlrospecllon was

Psychol,

49,

1987,

313-815. Theof simplicity, there wore Kiilpe, op,

problem as lo whether there is nosuch color as dark yellow troubled
Hering and otliers. Purdy’s research
was mst reported In 1929, but the

126; E. B. Titchener, Outline

fullest printed account is the note ofgenerally supposedtobe the solemetliod of psychology.

On the side

cit.,

of

Psychology,

1896,

55

(cf.

his

1937.

Text-Book of Psychology, 1910, 8064); H. Ebbinghaus, Grundziige der
Psychologic, I, 1897, 187-191 (sect.

Brightness and Intensity(hi the side of complexity,

14.2),

there were Ladd-Fraoklin, opp, cUt.,

On E. Bering’s phenomenobgicaland presently F. Brcntano, Ontersuchungen zur Slnnespsychologie,

distinction between a light sense and1907, esp. 51-79. G. F. Stout, Man-

Lichtshme, (1874) 1878, and compare Mitth^ung 5 with MlttheQ-ual of Psychology, 1899, 148 f., ispractically on the aide of complexity,

a color sense, see his Zur Lehre com

ung 6.
Is black a sensatlonf See H, L. F.

and M. Bentley, The simplicity ofoobr tones, Amer, J, Psychol, 14,V.

1903, 92-95,

m, (1866) trans. 1925, 204 f,; Her-on theside of simplicity, although both discussispracticallymeaning ofcase. For the only

inadequately

analysis in thistherecord of Ladd-Franklin’s exhibit ofunitaryofthecolor-sensations,mg, op, cit, Mittheilung 4; J. Ward,
Is ‘blaok’

a sensation?, Brit.

J.

Psy-

1905, 407-427; A further
note on the sensory character of

chol,

1,

psychicallybbck, ibid., 8, 1918, 212-221; E. B.
Titchener, A note on the sensory

Psycholcharacter of black, J. PhU,, 13, 1916,

complex and unitary colors, see her
Determination

Helmholtz, Physiohgfcal Optics,

Bull., 12, 1915, 62 f. For experiments

113-121;

A furtiier word on black.

COLOR AND ITS STIMULUS

152

tend to keep quality constant(hid; 649-flS5i and references citedjects

by the last two authors.

in a varying illuinination

which canThe following references deal withalso be perceived. Tire classical work

the problem of intensity vs. quality
in the blaok-gray-white series. Hering
denied intensity for the black-whites:on tills subject is D. Kalz, Die Erschelnungswelsen der Farben, 1911
(Z. Psychol, Ergbd. 7), esp. 79-245.

at-

An early summary of the problem is

tempted a psychophysiologieal resolution: Znr Psychophyaik der Ge-

K. Biihler, Die Erschelnungmeisen

op,

cit,f

21.

sect.

G. E. Mullerslchtsempllndungen,

Z Fsychol., 10,

der Farben, 1922, esp. 72-141. For
fire

history, see R. B.

MacLeod, An

IS96, 30-33; 14, 1897, 40-46, 6064. E. B. Titdiener rejected Muller’s

experimental investigation of briglit-view and discussed the problem cit-21,

ing olher references (q.v.): Lectureson the Elementary Psychology of
Feeling and Attention, 1908, 20-22,
324 f Titehener argued explicitly for.

both attributes: Text-Eook of Psychology, 1910, 205 f.. 217, 219. E. J.
Gates tried to show that the limens
for intensity and quality are different:Onintensive

andqualitative

ness constancy. Arch, Psychol, N, Y.,
1932, no, 135, 19-57. For still
more recent discussion, see K. Kofika,
Principles

Gestaltof

PsyMogy,

1935, esp. 240-264.
It should be noted tlial the shift
from sensation to perception, from
simplicity to complexity, from a sim-ple retinal system to the total organic
system, from immediate experience
to meaningful awaienos,s, from Titch-

Judgments of light sensations, Amer.

ener ta Kofika— the list gives dlffcr-

FsychoL, 26, 191S, 296-299. C.
Stumpf gave his view: Die Attribute

enl

;.

der

Abh.

Gosichtsempflndungen,preuss. Akttd. Wtes., philos.-hist. KL,

1917, no.

8.

F. L.

Dlmmlck foundaspectsofthesame shift—iscrucial. To be aware of the inlen,slly

of

the

dlfforont

illuniltmllon

somethingasfrom the brightness of theobject illuinlnaled is to respond ade-that white and black do not oveilap

quately to each aspect ofand determineddieir diresholds: A note on the seriesof blacks, greys and whites, Amer.

tion bill nol necessarily to have twoin the gray seriesI.

Psychol, 31, 1920, SOI f. Titehener

revised his

view:

Visual Intensity,

ibid,, 34, 1923, 310 f. Dimmick clari-fied his;A reinterpretation of thecolot-pyramid,

PsycholHeo.,

36,
1929, 83-90. Finally S. S. Stevens

has shown that the question of one
or two attributes depends, not on a
direct introspective apprehension ofdifferentially unique experiences, Tlio

coming lo doubt whether
immediate experience, ns Titehener

ogists are

believed

inWeber’s Law
law applied to
as

Acad,
Scl. Wash,, 20, 1934, 457-AS9: seealso E. G. Boring, The relation of thed’optiquesurIvmiite,1760,

Sci., 2,a^ pp. 25 f.

The dual perception of quality andmtensity comes about because ob-for

The researches cited on Weber's

upon the values of the stimulus: The

1935, 236-245. See

existsthere is for tlie psychologist to use.

Introspective judgments of equality

sions of the stimulus, Phil.

actuallyit,

any plausible scientific purpose, orwhether this discriminatory awareness of knowledgeable data is not allderived laws of dependence of theattributes of sensation to the dimen-

situa-

diificulty here is that many psychol-

the attributes, but on experimentally

attributes of tone. Free, net,llio

follows:

visual intensity are

Bouguer,

P.
la

TraiU
de la
Masson,gradation

51 1.;

V.

Etude de photomdtrie dleetrique,Ann. Chsm. Phys,, 3 ser., 14, 1845,
129-195,esp.

148-154;

D, F.

J,

Arago, Un mouvemeni moddrd rendla visibility(1850),

indesobjetsplus

facileOeuores completes, X,

NOTES

153

18S8, 255-260; G. T. Feohner, Uebet

absolutednlook the form of explaining

psychophysisches

Grundgeselz

amount.

Thusund (lessen Bedehnng zur Schatzung

explaining

der SterngroBsen^ Abh. sbchi, Ges.
Wiss.j maUi.-phys. Cl., 4, IBM, 457-

the actual results fromaway—thetlieorlzing—or even

deviation
tile

of

Weber

law, instead of explaining the form

457-459. 465-483; E2e-of ie Weber function without rela-mente der Psychophysik, 1880, I.
139-175; H. L. F, v. Helmhollz,

tion to the law’ which the results did

Physiological(1860)

ture bears more upon the psychology

1924, 172-203; H. Aubert,
Physiolo^e der NetAaut, 1865, 52-

of scientific belief than upon that

esp.

532,

Optics,II,trans.

82; A. ^nig and £. firodhiui, Experimentelle Untersuchungen liber

me psychophyslsche

Fundamentalformel in Bezug auf den Gesicbtssinn,
Sitzmgsher. preuss. Akad. Wise.,
1888, 917-931; 1889, 841-844;
J.

not confirm. The study of this litera-vision which Is mediated by the retina.

Thus recently L. T. Troland

spoke as if Weber’s law might be thetrue function for part of the intensitive range:"The exact value of therelative threshold varies rather widelywith conditions, but is of the order

BlatMjinrd, The brightness sensibilityof magnitude of 1/lOOth part, or 1%,of the retina, Phys. flau,, son 2, 11,

for the intensity range within which

1918, 81-99.

the logarithmic relationship holds,"

Another phase of the early establislunent orWeber’s law for visionPrinciples

of

Psychophyslobgy,II,1930, 79. Against this view that theWeber function is fundamentally

was Fcchner's study of stellar magnitudes. The astronomers Herschel andSteinheil had shown, hy photometriclogarithmlo in spite of certain devia-

measurements,

land,

that

the

acceptedscale of stellar magnitudes is a logar-

ithmic function of the intensities oftions from the true law, see H. Hong-

The Weber-Fechner law andthe all-or-none theory, 1. gen, Psychol, 3, 1930, 351-372. An excellent

the stellar light. Fechner thought thatsummary of results, showing that thefact supported Wober’s law.

Seefraction tends to be minimal for some

Fechner and Helmholtz, hcc. citi.
Although there is a considerable

middle intensity, is A. H. Holway
and G C. Pratt, The Weber-ratio forliterature of Weber's law in the field

intensitive

tills

of vision,

most ofitgets nowhere.

discrimination,

Psychol

Reo., 43, 1936, 322-340.

Fechner 'established' the law in 1860,

and Aubert disestablished it in 1865by showing how the Weber fraction
varies with intensity. Since then noone has ever supposed that the Weber
fraction remains constant at all intensities,

but there have been many

Color Mixture
For Isaac Newton’s laws of color
mixture, see the preceding chapter,
pp. 102^-106. For ms further discirssion of color mixture and his color
see his Opticks, 1704 et seq.,

attempts to explain its departure fromcircle,Ebbinghaus, Ueber den Grand der Abweichungen von dem Weber'schen

Bk. I, Pt. 2, prop. 4-7.
H. L. F. V. Helmholtz’s two mostGesetz bei Lichtempilndungen, Arch,noticeable difference increases as the

Ueber die 'Theorle der zusammengesetzen Farben, Ann. Phus. Chem.,
163, 1852, 45-66; and Ueber die
Zusammensetzung Von Spectralfarben, {bid., 170, 1855, 1-28; which

stimulus Increases and that it repre-

ate reprinted in his

sents more nearly a constant propor-

Uche Abhandkmgen, 1883, U, 1-23
and 45-70 respectively. See also his

constancy, like the paper of H.

ges. Physiol, 45, 1889, 118-133, The

point is that Weber's law won belief

becauseitisobvious that the justtion of the stimulus than a constantimportant papers on this subject are

Wissensohaft-

COLOR AND ITS STIMULUS

154
todiscussion

Handbucb derhis

I860, sect.

phystohgischen Ojytih

20, reprinted in Germ. 3 ed. end
Eng. trans.; and the later discussion

pressions produUs par la lumldre surde la oue, 1829, [n.v.]; Betraentungen Bber ein von Hrn. Tal-i’organbot vorgeschlagenes photometrisches

Ann,

Phys.

Chem.,

Ill,in idem, 2 ed., 1896, sect. 20.

Frinoip,

H. Grassmann's paper is Zur Theorle der Fatbenmischung, Ann. Phys,

1835, 457-468; H. F. Talbot, Experiments on light; Phil Mag., 3 ser.,

Chem., 165, 1853, 69-84. It is translated into English in Phil Mag., 4

1834, 321-334, esp. 327-334.

ser., 7,

1854, 254-284.

For J. Clerk Maxwell’s mote important papers on this topic, see his
Experiments on colour, as perceived
by the eye, with remarks on cokuiblindness, Trans,

Soo.

roy.

Edinb.,

validity of theThe

law was pretty wellestabbshed for photometric purposes
by 0. Lummer and E. Brodhun,

Fhotometrische

Untersuchungen,I,

Ueber ein neues Photometer, Z. Instrumentenkunde, 6, 1889, 41-50[n.v.].

21 (2), 1855, 27S-298; On the theory of compound colours, and theColor Diagrams

rmations of the colours of the spec-

trum, Phil Trans., 150, 1860, 57-

For H. L. F. v. Helmholtz's circle,

Handbuch der84; reprinted in The Scientific Papersof lames Clerk Maxwell, 1890, I,

Optik, 1 ed. (or 3 ed.),nos. 7 and 21. See {bid., I and II for

sect.

Maxwell’s other papers on co’or.
The later determination of theibid,. Fig. 19.

wave-lengths of oomplementaries, determinations which confirmed Helm-

op. cit„ 1855, Plato I, Fig. 1.

M. vonUober dieholtz’s values of 1855, are;

Frey and J. von Kries,
Mischung von Speclralfarben, Arch.
Fhi/slol Lelmig, 1881, 336-353; A,
Kfinlg and C. Dleterioi, Die Grundempfiudungen to normalen undanomalen Farbensystemen und ihre
IntensittLtsverteilung in Spektrum, Z.

Psychol., 4, 1892, 241-347, esp. 287(Helmholtz gives

this reference In-

oonectly as Wied. Ann., 1887, andNagel has twice copied him); R, H.
Sinden,Studiesbased on spectral

see

20,

Fig.

16;

physiolcgisohen(or his

II,

1860,

triangle,

For J. C. Maxwell’s briangle, see
KBnig’s triangle was developed in
Kbnig and Dietcrici, op, eit.. Figs.
7 and 8.
For W. Wundt’s cone, see his Vor-

lesungen iiber die Uensohen- undThierseeU, 2 ed., 1893, (or Eng,
trans.), Lect. 6, Fig. 13. Wundt did

not give the cone to the first edition of
1863, and it is not clear why he introduced so inferior a diagram after hebad given the sphere in 1874.

Wundt cites the reference to J. H.
Lambert’s pyramid as Besohreibung
eftier nUt Jem CALsa'sehen Waahse

For the origin of color-mixing byausgemalten Farbenpyramlde, 1772
[n.v.]. P. 0. Runge’s Parbenkugel,
1810, gives the double pyramid astransmission and reflection, see J. H.

Fig. 4, and is reprinted in nis Hinter-

oomplementaries, J. apt. Soo. Amer.,7, 1923, 1128-1158.

Lambert, PhotomeMa, sine de men-lassene Schrlften, 1840,

sura et gradibus Zioninis, colarum etesp. 118.

umbrae, 1760, 527,

For Wundt's sphere, see his CrutidzUge der physiologfschen Psychologie,
1 ed., 1874, 395, or any of the five

first

[n.v.].

For theuse of rotating sectors for color

mixture, see P.

IntroducHo

van Musschenbroefc,

ad •philosophiam notu-

ralm, 1768, II, ’728, sect. 1820.

On

the

originsoftheTalbot-Plateau law, see J. Plateau, Dissertation sur queltpies propriMs des im-I,

112-137,

succeeding editions.

For H. Ebbinghaus’ double pyramid, see his Gfundzilge der Psychologie, 1 ed., 1902, 1, 184. This figure is the best known of them allChapter 5

VISUAL PHENOMENAT

he scientific interest in color began, as we have seen, withthe objective physical problem, fire problem of the stimulus to color, not the problem of seen color itself. Interest

centered in the nature of light. Newton’s discovery that white Kght
is a mixture of colored lights

was really the discovery of the subjec-

tive fact that white, a simple color showing no evidence of com-ponents, is an illusion, a phenomenon that depends less upon thehght (for white has no unique stimulus, there are many different
light mixtures that will give white) than upon the constitution of

the perceiving organism. Newton’s interest, however, was chiefly

focused upon the nature of the stimulus. His laws of color mixture

were laws of the ways in which light combines to make various
colors; no one at the time realized that Newton was actually in-vestigating the properties of the percipient person.

On the other hand, there was to be found an incidental interestin phenomena that were recognized as subjective. The careful his-

torian can note the phenomenological observations of Aristotle andPtolemy; he can cite Alhazen’s Opticae thesoum (ca. 1100) andLeonardo da Vinci’s Trattato deUa pittura (ca, 1519); he can quotehalf a dozen other ancients who wrote before the seventeenth century. In the seventeenth century there were more than a score ofmen who interested themselves in incidental subjective phenomenaof vision: Kepler (1604), Boyle (1663), Mariotte (who discovered

the blind spot in 1668), Newton. There was a considerable literature by the astronomers, who had discovered irradiation, the factthat the apparent size ofacelestial object

depends upon its

brightness. The eighteenth century began with Newton’s Optich(1704). By 1772 there was enough known for the chemist, Joseph
Priestley, to write, as an 812-page book, The History andPremt

State of Discoveries Relating to Vision, Light, and Colours, but abook which dealt much more with the physics dian widr the psychology of color, G. L. L. Buffon, the French naturalist, wrote a
155

VISUAL PHENOMENA

156

Dissertation sur les couleuts accidenteUes in 1743, but for the mostpart the phenomenological writings in this century were by lessfamous men; C. Scherffet (1761-1775), N. de Beguelin (17671771), de Godart (1778), C. G. Kratzenstein (1781), R. W.

Dar-win ( 1786 ) These papers, however, were but a beginning. Plateau,
who wrote in 1876 a history of visual sensation and wrote from.

the phenomenological point of view, cited less than sixty references for the eighteenth century and over seven hundred for thefirstseventy-five years of the rrineteenth.

Thus Goethe may be

counted as the real head of the phenomenological tradition in the
study of vision, for, even though all the important topics had al-

ready been touched upon, there was before him relatively little
careful systematization of the field.

Plateau, in writing this historical account, classified the hundred-

odd papers that had been published before 1800 under six rubrics,
whiii show more or less the nature of the subjective problems
recognized in the early days. (1) Plateau’s fli'st section dealt with"the persistence of impressions on the retina,” a topic which musthave been especially interesting to one of the authors of the TalbotPlateau law. (2) His second section covered the “ordiiiniy accidental colors of succession.” Buffon (1743)

had coined thisphrase, “accidental colors” (couleurs accidenteUes, zufalUge Far-ben), to cover these subjective phenomena whidi seem somewhat
capricious in occurrence. In English the phenomena were also

often referred to as spectra (or in French, spectres). The word

spectrum in those days meant a visual appearance, as distinguishedfrom a corporeal reality, and was thus similar to spectre. It was

Newton who applied the term spectrum to the colored image
formed by a prism. (The French spectre means both a ghost andthe band of colors.) Plateau in this section brought together thedata for die flight of colors and for those after-images in which theform is not a dear<ut objective Image. (3) His third section took

up the well-defined after-images: “images which follow the contemplation of objects of great brilliance or even of well-illuminatedwhite objects.” (4) “Irradiation” was his fourth topic. Althou^
Leonardo da Vinci had noted that whites tend to be larger thanblacks, it was .for the most part file astronomers who were inter-

ested in the spatial relations of dark and light objects in eclipses

and ocoultations. (5) The fifth topic, “the ordinary phenomena ofcontrast,” presented the essential facts of simultaneous contrast,

AFTER-IMAGES

157

but it lacked definiteness because the fundamental importance of
paired complomentariness among the colors was not recognized soearly. (6) Plateau ended his r6suin4 with summaries of tiie litera-ture on “colored shadows,” for which the technique of production

had been worked out without a dear understanding of the factthat the shadows are instances of complementary color contrast.

Such is the background from which the modem laws of afterimage, adaptation and contrast emerged.

After-Images
There are certain visual after-effects so easily obtained and so
striking that they were hound early to find their way into the litera-ture of casual observation. (1) The circle of light that is seen on

whirling a live coal indicates a persistence of visual sensation. So
too does the confusion of the rapidly moving parts of an object.

Ptolemy remarked that a disk, painted with various colors, appears
to be but a single color when it is turned rapidly. (2) Looking at

the sun even briefiy leaves a succession of colored appearances fordie closed eye, or else after-images of the sun’s disk upon any fieldof projection.

Of this obsemtion there are numerous early in-stances, although a systematic account of the phenomenon seems

not to occur before Boyle’s description (1663). (3) Gazing fixedly
at a window and then looldng away gives a negative after-image ofthe pattern of brightness—the dark frame and the bright fieldnext it are reversed. So natural is it to look at windows that one

ought to expect early descriptions of this phenomenon of reversal,

and such descriptions were indeed given by Aguilonius in 1613
and by N. C. F. de Peireso in 1634. (4) The fact that these aftereffects may recur periodically led Aristotle

and others after him

to consider dreams as the recurrences of perceptual images of wak-ing life.

The

early

interest inafter-images

was frivolous.

A priest,

how a friend had wagered that he could
make the priest see in the dark, and had won the wager by having
Kircher, told (1646)

him look steadily at a drawing by a window in a dark-room andthen gaze ‘at’ a piece of white paper when the room was suddenly
thrown into complete darkness. ’The paper, as Helmholtz noted
later,

was unnecessary; but Kircher’s theory was that the lightfrom the object, having entered the eye, was again projected by,

VISUAL PHENOMENA

158

the eye upon the paper—a theory illusti-ative of the seventeenth
century’s uncertainty about the nature of light and of visual perception.

Newton (1691), queried by John Locke about Boyle’s accountof the after-effects of gazing at the sun, looked himself at the mir-rored image of the sun three times in close succession, and then had
to shut himself up for three days in a dark room in order to get ridof the after-images. Newton was of tire opinion that he had also todivert his mind from the after-images and that they would still

have returned after a very long time had he not resisted seeingthem.
In the eighteenth century there wassome systematic study.

Jirrin (1738 ) put forth the theory that the reversal of brightness inthe negative after-image is due to the fact that the process in theeye continues but is opposite in effect— a theory which is some-what advanced over the fatigue theory that presently came into
vogue, because it accounts for an after-image in complete darkness when there is no stimulation to the eye at all. Buffon ( 1743 )who gave a full and circumstantial account of the occurrence of“accidental colors,” was the first to desci-ibe in detail negative after-

images of colois, noting that blue is the cause of ‘aoddental’ yellow

and conversely, that ted is the cause of ‘accidental’ green and conversely,and even that the consequence of red is a green that issomewhat bluish. Thus Buffon actually sought laws for these effects; he did not regard them as truly accidental. Benjamin Franklin ( 170S ) noted how the positive after-image appears on the fieldof the closed eyes and the negative on a field of wliite paper. Thisphenomenon, called thereafter the “Franklin experiment," was dis-cussed by Godart (1770), along with an elaborate account of theflight of colors.

In 176S Father Scherffer published a long discussion of theseHe noted that the color reverses occur between theoomplementaries of Newton’s color circle, and went on to discuss

after-images.

the painting of a picture in the complementaries of the correct

hues so that the after-image would assume die natural colors. He
proposed the fatigue theory of the negative after-images of bothbri^tnesses and colors, the theory that is essentially part of theYoung-Helmholtz theory. The eye, locally fatigued to brightness
or specific colors, sees white light with a diminution of the previous
excitation, so that the former light regions become relatively dark.

AFTER-IMAGES
and die cobred regions appear the complementary color

169
{for

white less some of the color for which the eye is fatigued gives acomplementary cobr), This theory, though more specific than
Jurin’s, still does not eicplain

how the negative images occur in com-plete darkness.

The scientific situation for the after-image at the end of theeighteenth century was set forth in an experimental paper byRobert Waring Darwin, the father of Charles Darwin and die sonof Erasmus Darwin, who communicated the paper to the Royal

Society in 1786. Robert Darwm undertook first to show that theretina itself is active in vision, since it gives rise to “ocular spectra"

when no light is being admitted to the eye. He then laid down thelaws of retinal sensibility. “The retina is not so easily excited into
actionby less irritation after having been lately subjected togreater”; and conversely. In these principles we have what amounts
to a law of adaptation, andwe see how negative after-effects are

related to the differential fatigue of the retina. Darwin’s explanation of positive after-images was that retinal excitation tends tocontinue if the retina is not fatigued, and that it continues spas-

modically with recurrent spectra if the original intensity is great

enough. When the stimulus is continued and the retina fatigued,

however, then die spectra are reversed, in brightness and in color,as might be expected from the principles of sensibility just stated.

He paired green ( not blue-green) with red, orange with blue, andyellow with violet, being thus less phenomenologically accurate

than Buffon. Darwin also noted that the reversed spectra are recurrent when the stimulus has been btense enough, that, when thesun is the stimulus, they may last for days.

We have already seen what, impetus Goethe gave to the phenomenological description of visual facts in the nineteenth century(pp. 112-119). Purkmje followed him, and even Johannes Muller

wrote a litde book on subjective visual phenomena (1826). What

was becommg a large literature of conflicting opinions about theafter-images was then brought together and ordered, first by Plateau in 1833 and then by Fechner in 1838. Fechner stressed therelation of the reversals to the complementariness of the colors.

Helmholtz incorporated the explanation of negative after-images

by relative fatigue into his general theory of vision—the YoungHelmholtz theory as it came to be called. For Helmholtz thereversals

were complementary because complementaries, when

VISUAL PHENOMENA

160

mixed, give white; hence the diminution of one color (or of its
stimulating power) in white yields an increasing effect of the com-plementary color, Hering, on the other hand, built his theory uponcomplementaries, supposing that adaptation to one color means
sensitization to its opposite. Thus Hering’s theory avoided the objection that the negative image would not be seen by a lightless
retina.

Modem views, of course, take it tor granted that excitation

disturbs some sort of chemical equiHbrimn in the retina, which,being recovered in the absence of excitation, excites the comple-

mentaty quality.

The ^erm spectra dropped out of use about the middle of thenineteenth century and accidental colors a little later. Fechner(1838),

who consistently spoke of afterimages (Nachbilder),seems to have established the word in its technical meaning. Horing later (1872) used the general term, light-induction, for both
positivefects.

and negative and both simultaneous and successive ef-

He also used the term successive contrast for the negative

after-effects.

Adaptation

We have just seen that the phenomenon of nogalive after-imago
was explained by such early investigators as Father Scherffer andRobert Darwin as due to the selective fatigue of the retina to continued excitation, such that, with sensitivity differentially diminished, a general excitant, like white light, would produce a residual

and hence a reversed effect. Thus it can be said to have been realized throughout most of the eighteenth century that excitation
leads to diminished sensitivity.
It wasHermann Aubert, the physiologist who shares with Helm-holtz and Hering the distinction of being a chief
field of physiological optics,

pioneer in the

who in 1865 introduced both the con-

cept of adaptation and the term. The words adaptation

and accommodation had both been used to denote the adjustment of theeye for near and far focus, but accommodation had

received preference for this function since about 1850, and it wasmeaningthatwhich Helmholtz fixed upon psychology. Aubert in his Physiolog^
det Netsihaut ^1865) sought to limit the word adaptation,other hand, to the adjustment of the eye to theon theintensity of li ght,

and his usage has held ever since.
Since the problem arose in connection withthe diminution of

DARK ADAPTATION

161

visual sensitivity as the result of excitation, it was natural that

Aubeit should undertake to measure adaptation in terms of sensitivity, and not phenomenologically in terms of the level of bright-

ness at which objects are seen. As observer he would go from alight into a dark room, where he would adjust the length of a fineplatinum wire connected across a Daniel cell until the wire, hotfrom the current, was just visible in the dark. The shorter the wire,
the less its electrical resistance, the greater the current, and thus

the greater the light given ofi. By the use of an episcotister ( an in-stnament which he both invented and named) he calibrated thebrilliance of the wire photometrically to establish the ratio ofbrightaesses between two lengths of wire shunted across the constant voltage of the cell, In this way he determined the absolute

threshold for illumination after periods of dark-adaptation that

ranged from no time at all up to more than two hours. The resultant curve showed that there was more adaptation in the first
five minutes than in the next 115 minutes, and that adaptation wasstiU not complete after two hours. Aubert’s function—plotted actu-

ally between sensitivity (reciprocals of the absolute threshold)and time—has the general form and approximate values of thelater

more careful investigations; and this in spite of a serious

error in his method, his neglect to control the degree of light-

adaptation willr which the subject entered the dark.

This omission was significant. Aubert knew noSiing about lightadaptation, although it was of course the more obvious basis forthe negative after-images. He thought of the dark as a state of no
excitation and, theiefoie, as the condition of complete rest for theeye, a state in which the retina would gradually reach maximal
sensitivity. Like Helmholtz he conceived of the zero of the visualsystem as lying in black and at no illumination. It took Heiing toargue that black is a sensation, that the visual system is symmetrical about middle gray, and that the phenomena of dark-adaptation

are matched by the phenomena of light-adaptation. Aubert, it istrue, noted the crucial phenomenological fact that the dark field

becomes subjectively lighter as the observer continues in the darkroom, but he failed to see the implication of this change—thatblack implies excitation and that the resting retina finds its equilibrium at gray.

Hering, however, saw this point and made it the central principle of orientation for his Zwr Lehre eom Lichtsinne in 187^1874.

102

VISUAL PHENOMENAHe argued that black is a sensation and that the series of graysfrom black to white consists of a constant increase in the weight ofwhite and decrease in the weight of black in the total excitation.

Middle gray is the point that is just as white as it is black, or, forthat matter, just as blue as it is yellow.

We have already seen(pp. 132 f.) the difficulty that such a view brought, the question as to why the middle point of the system is not an invisibility

instead of a gray, and we have seen how Muller rescued Heringfrom this difficulty by his hypothesis of cortical gray. Nevertheless,in spite of its introduction of this new difficulty, Hering’s view wasan advance over Aubert’s. It took cognizance of the phenomenologically positive character of black, which means that black

must also be physiologically positive at the level of the retina,
although physically negative at the level of stimulus-illumination.

Perhaps even then the symmetry of the visual system would nothave become apparent had not Hering made it vivid in terms of
his theory of retinal excitation, the theory that there are three
retinal substances, each capable of undergoing a reversible process—one substance for gieen-red, one for blue-yollow, and one forblack-white. With this picture of adaptation as a balance between

two opposing tendencies, the notion of retinal fatigue appeared tobe quite inadequate to express the effects of continued stimulation.

The classical researches, after tlie symmetrical nature of the
problem became clear, are Piper’s on dark-adaptation and Lehmann’s on light-adaptation, both of them done under Nagel’s inspiration at Berlin. Piper ( 1903) improved Aubeit’s technique.

Hecontrolled the initial state of light-adaptation at a high value, sub-sequently measuring adaptation by the absolute threshold forbrightness in the dark. The resultant function is sigmoid in form!

during the first nine minutes, there was Httle adaptation, whereas
during the next twenty minutes adaptation went on rapidly andafter an hour was beginning to level off. Nagel, however,j^that even after sixteen hours

asserted(an experiment on himself) it is notdear that complete dark adaptation has been reached.

To determine functions of light-adaptation is much mote involved, inasmuch as there is no single level of illumination

adaptation shopld naturally be made. It was

to which;;Ohmauru4906)

who found the functions for adaptation to various^brightnesses,
and he got a clear indication that the fi nal level of eguiUVii-iSiT,,
Mgher, ti;e.hi^ei: the intfflsity lowhich adaptation isisbeing mTde!

LIGHT ADAPTATION

163(There is, of course, no reason why dark-adaptation should notalso be determined for various levels of low illumination, but noteven yet does the problem seem quite symmetrical to pychologists: darkness appears to be more ‘absolute’ than lightness,

)

Loh-

mann continued to use Auberfs and Piper's criterion of sensitivity;
the absolute threshold for brightness in the dark. He had to takehis light-adapted observers out of the light, put them in the dark,

and determine the threshold quiddy { 10 sees. ).

It would seem nat-ural for him to have used the diEerential intensitive limen at thelevel of illumination to which the observer was being adapted;

that would be the true analogy to Aubert’s method. With tradition

dominant, however, he kept to the absolute threshold as a measure. Lohmann’s functions show li^t-adaptation to be much more

rapid than dark-adaptation. There is a tremendous change in thefirst minute,there is very little change after the first ten minutes,

and complete adaptation may be reached in ten minutes for intense light or after only an hour for weaker light—for the rate ofchange depends upon the intensity to which adaptation is made.
In a sense all this measurement of adaptation is indirect. What
the procedures measure directly is a capacity for discrimination. A
directmeasure would give the curve that represents the phe-nomenological change—in dark-adaptation the shift of black to-ward middle gray and in light-adaptation the shift of white towardmiddle gray. One can note, as Aubert did, that the black of complete darkness gets subjectively lighter as it continues, but thefunction is difficult to determine with any exactitude because themethod would normally involve a comparison of two grays separated by a long interval of time, the comparison of the gray after

adaptation with the gray before adaptation. Since the whole of tire
retina is always exposed to some degree of lightness or darkness,there is no way of comparing the adaptation of one part of theretina with some other part which has no adaptation; every part isin some state of adaptation depending on its previous stimulation.

For colors the situation is different. Although the negative afterimages had shown that sensitivity to color diminishes with continued excitation, Aubert did not mention color in connection withadaptation, partly because there is no way in winch the absolute

threshold of vision changes with color adaptation. The first ditectresearch on retinal fatigue for color was undertaken by S. Exnei inHelmholtz’ laboratory at Heidelberg in 1868. Exner studied theVISUAL PHENOMENA

164
faHiTig of cobis with

continued fixationb an effort to find support

for the Young-Helmholtz theory of color vision. His melliod was tofixate a small patch of color for the desii'ed adaptation time andthen to project the after-image on a much larger colored field.
Thus fixation of a red patch with the subsequent projection of theafter-image on a fieldd the same red showed the after-image to be

an unsaturated red as compared with the rest of the field. Here thefield serves as a standard of comparison, because the retina during
adaptation is excited by a gray, which is a chromatically neutral
field,and thus it comestothe colored field without previous

adaptation to color. (In the case of brightness-adaptation there

was no way of getting a comparable neutral adaptation field.)
Exner also found that the after-image of a green projected on a red
field gave a red better saturated than the field. The other colors

gave comparable results. In this way he demonstrated clearly thediminution of color sensitivity with continued excitation.
It was Hetmg who by the symmetry of his tlieoiy for colors andfor grays brought color fatigue under tire general concept of adaptation. Light-adaptation is a function of the change in tire retiiial‘black-white’ substance, he thou^t; so chromatic adaplaliotr iniisl

be a function of changes in the ‘blue-yellow’ and ‘greou-red’ substances.

There was not much early research on chromatic adaptation.
Apparently the first paper after Extrer was one by Jolm Aitken in
1872, followed in 1899 by G. J. Burch’s description of the tem-porary color-blindness which he induced by chromatic adaptation.
It is a question as to whether color completely disappears rmder

adaptation. Burch found that it does, and he is supported in a re-cent study by H. Sheppard (1920). L. T. Troland, on the contrary, has held that equilibrium is reached at different bvels under'

different conditions,and that ordinarily some hue remams at

maximal adaptation.
Another controversial problem concerns the constancy of hue

m a color undergomg adaptation. Exner found oidy three (primary) cobrs that adaptatton does not change in hue; and he was
supported in this finding by Hess (1890) and Voeste (1898).
Troland, however, has contradicted this finding on the groundthat the change appears because the Bezold-Brucke phenomenon
is involved

and not because of chromatic adaptation per se.

,

COLOR CONTRAST

165

Contrast
The principle of brightness contrast was known to Aristotle, thefact that themargin of a black on a white ground may seem

blacker than the rest of the color, and conversely, Alhazen (ca.

1100) attributed the invisibflily of the stars in daytime to the lackof contrast between them and the bright sky. Leonardo da Vinci(ca. 1519) laid down a number of exact nJes whereby painters

might use or take account of contrast between black and white.
Although not always intelligibly, the early writers also mentioned
color contrast; frequently, however, in such a way that the point of

the remark seems to lie in the brightness contrast of colors. Leo-

nardo, however, stated the correct rule for color, pairing the oomplementaries correctly almost two centuries before Newton madeout the general table of opposition between pairs of colors. He
wrote: “In order to attain a color of the greatest possible perfection, one has to place it in the neighborhood of the directly con-trary color: thus one places blade with white, yellow with blue,

green with red.”

Almost all the writers whom we have mentioned in this chapter

and who wrote before 1800 made at least incidental mention ofbrightness contrast,

and often tihey spoke of color contrast, al-though the examples of the latter phenomenon do not always seemcorrect in the li^t of our present knowledge. Many of them, like
Aristotle, noted the occurrence of a marginal contrast,

speciala halo ofenhancement close to the boundary contour. This phe-nomenon was, however, undoubtedly due to eye-movement andthe reenforcing after-image, as Helmholtz later made dear ( 1860 )There were also, however, many valid examples. Newton cited
Halley’s remark that the hand of a deep-sea diver appears rose-colored against the green of the sea-water— doubtless because
contours are blurred and brightness more nearly equalized in thedepths. BuSon (1743) gave instances of both brightness contrast

and color contrast as a form of accidental colors. Robert Darwinsummed the matter up in 1786: “It was before observed, that when
the two colours viewed together were opposite to each other, as

yellow and blue, red and green, &c, according to the table of reflections and transmissions of light in Sir ISAAC

NEWTON’s Optics,... the spectra of those colours were of all others the most brilliant, and best deflned; because they were combined of the reverse

VISUAL PHENOMENA

166

spectrum of one colour, and of the direct spectrum of the other."Darwin then repeated the implication of Leonardo’s thought, thatcolor contrast is an aid to heauty, perhaps in part because the outlines are emphasized by it.

There was also, from Leonardo on down, a great deal of discussion of the cause of colored shadows, especially as to why shadowsare blue at sunset. The topic was, of course, of great interest to
painters.

For the most part it was expected that the explanation

would be physical, not a consequence of the properties of the human eye. Subjective explanations were not much in vogue before
the nineteenth century. In 1782 feere appeared a book of morethan 200 pages by an author who signed himself “H. F. T.” Called
Observations sur les ombres colorSes, it dealt entirely with ananalysis of the physical conditions under which colored shadowsarise. The nearest it came to a solution of the problem was to lay

down the principle that the shadows can be of various colors anddepend upon the relation of two lights to each other. Apparently
the first person to get at the true nature of the colored shadows

was Count Rumford (B. Thompson), who in 1794 found that hecould produce the phenomena with a colored glass and two artificial lights in a dark room. Wlien he put a yellow glass in front of

one li^t, it oolotod the shadow from tire other light yellow; but
the objectively uncolored shadow from the first light tlien lookedblue.

Thus he synthesized the blue sunset shadows. Rumford

found, however, that a blue glass reversed the phenomenon, oeat-

ing a yellow shadow in the absence of any yellow light. Unfortunately he had no red and green glasses wherewith to complete

the generalization; but he said: “I began to suspect that the coloursof the shadows might, in many cases, notwithstanding their ap-

parent brilliancy, be merely an optical deception, owing to contrast, or to some effect of the other neighboring colours upon theeye,” This suspicion

he established to his ovro satisfaction by

showing that the induced color in the gray shadow vanishes when
the shadow is viewed through a tube that excludes sight of thesurrounding field and the neighboring shadow.

The facts of both brightness and color contrast seem to have been
generally accepted from the beginning of the nineteenth century,

Goethe and die other phenomenologists described many instances.
Johannes Muller (1838) discussed “physiological colors producedby contrast," placing the discussion under the general heading,COLOR CONTRAST

167"Of the reciprocal action of diierent parts of the retina upon eachother.” This phrase anticipates Herin^s notion of contrast as show-

ing that the retina acts as a whole. Thomas Young in 1807 had
given what might be called a sympathetic theory of color contrast

He suggested tiiat those parts of the retina which are adjacent to aregion excited by colored light are affected "by sympathy," so thatalong with the excited area they lose part of their sensibility tolight and are therefore more strongly affected by the remaining

constituent parts of white light

Sui a theory of the sympathetic

adaptation of adjacent regions is invalidated by the fact that contrast colors

appear before adaptation can be effective. In 1839

M. E. Chevreul published a book of more than 700 pages, De hhi du contfoste simidtanS des coideurs, which is mostly concernedwith principles of contrast as applied to paintings and other ohjets
dart, but which shows also that the principle had got itself established in scientific thought. It was tire next year ( 1840 ) that Fechnei-’s discussion of Nebenbilder firmly established the rule that con-trast occurs between complementary coloi-s and brightnesses.

In 1855 M. Meyer demonstrated color contrast by a simple useof colored papers. Placing a small patch of gray paper upon a pieceof colored paper, he covered both with a piece of thin white paper

through whidr the other papers could be faintly seen. The gray,of course, took on the contrast color that is complementary to its

background color. Not only did this demonstration bring the factsof contrast under easy conditions of demonstration; it also related

them to the phenomena of colored shadows, for it became dearthat contrast is more effective with the shadow-like appearance ofthe colored papers seen through the white paper than with thestronger undimmed papers.

Helmholtz in 1860 discussed simultaneous contrast at great
length. Although he warned against confusing it with that type of

successive contrast which, depending

upon fatigue and inad-vertent eye-movement, seems to put a halo of complementary color

about the boundary of a field, he admitted, nevertheless, theexistence of simultaneous contrast that appears immediately andwithout eye-movement. At die same time, he was hard put to it toexplain such a phenomenon. In his perplexity he resorted to thetheory that the opposite color is seen as an illusion of judgment;a view which he generalized under the concept of unconscious inference {unbeumster ScMuss], tiie notion that perceptions are

VISUAL PHENOMENA

168

altered immediately and involuntarily so as to accord with theresults of inference based upon past experience.

For all its usefulness, however, unconscious inference is but anegative explanation. It tells nothing positive about the nature of
the phenomenon; it is a speculation which is essentially a confession of ignorance. Hering (1873 et seq.) supplied a positive concept: simultaneous Hght-induction. His Zur Lehre vom Lichtsime
is for theFio.

most part concerned with the problems of successive and

H. Appabatos fob BaioiiTNias Contb.\8t iiv IIiab and PuCTom(1894)The variably illumitiated suifaee f is seen as a small squnio Held thrinigh
the window in F; and F, vailabiy iUuminalccl, becomas u sunouncling
field that induces a contrast eSect in f. Similarly for /'and F'. Tlic standardof comparison is f, supported by soma given value of F, arid / is iiialcliedinbri^tnesstoffor dilfeient values of F.

simultaneous induction and of contrast. He added no crucial dis-covery to the facts of contrast, it is true, but he organized thosefacts under intelligible positive scientific rubrics, and he success-fully removed from this chapter of visual psychology the concept

of unconscious inference. He devised, in addition, several schemes
for the demonstration of contrast effects. Among them there is tlie

“Hering window" which gives remarkably well-saturated contrast
colors of shadows cast in a dark room and produced by a double
window provided with a gray glass and colored glass which canbe changed. This device represents the final perfection of Humford’s old experiment.

The problem of contrast was now ready to pass over into theexperimental and quantitative stage. It was Alfred Lehmann of

Copenhagen vyho in 1886 undertook to study the application of
the psychophysical method of mean gradations to certain problemsof visual brl^tuess. In the course of his study he worked out die
relationship between the objective brightnesses of (1 ) a gray back-COLOR CONTRAST

169

ground that could be varied, (2) a variable gray disk seen against
the background, and (3) a second gray disk that was varied tomatch the other disk whose subjective brightness was undergoing
induction by its background. He came out with a simple relation,
but this problem was put in more general form in the classical re-search of Hess and Pretori published in 1894.

They set up the apparatus which is shown in Fig. 21. The observer, looking at this apparatus from the front, sees

two large

square gray fields, F and F', and in the center of each, a small grayfield, f andf showing through windows in F and F'. All four fields,

are independently varied in bri^tness by lamps that illuminate

them and move back and forth in tunnels running to the right andthe left. The task is to equate / subjectively to f for various brightnesses of the inducing backgroimd, F. Since everything is affectedinductively by its surroundings, it is necessary also to control F',

the background of f, Witli F' and f set at some value to provide astandard of comparison, F is varied, and then ihere is determined
the illumination of f that makes f and f subjectively equal inbrightness. The resultant generahzatiori can be expressed in an

equation. If F and f represent the iUuminations of these fields (inhefners), then/= %F + c, a linear relation in which the induc-tion is one-half, for a change in F induces half as much change in/.

The value c depends upon the values of F' and f, for the samef — j4F'. The inductive

relation holds between F' and f and c=coefficient, Va, is dependent, of course, upon the particular dimen-

sions of this apparatus. Nevertheless, we have with this researchcome a very long way from Leonardo’s rules for contrast in painting or even from Buffon’s observations about accidental colors.

For color contrast the classical study was made by Kirsohmann
in Wundt’s laboratory at Leipzig in 1890.

Kirsohmann placed agray ring on a color-mixer so that the ring took on a contrast color.
This ring he matched by varying papers on another mixer outside
the field of influence of the inducing color. In this manner he deter-—

mined most of the important laws of color contrast except thefundamental law that contrast is always in the direction of maximal opposition, for that principle had been clear since Fechner.
These are Kirschmann’s principal findings. (1) The intensity ofsimultaneous contrast increases, within the limits of the distinct
perception of size of the resting eye, in proportion to the linear extension of the inducing part of the retina; fliat is to say, the larger

170

VISUAL PHENOMENA

the perceived inducing field, the greater the effect. (2) Simul-

taneous color contrast is maximal when brightness contrast is absent or reduced to a minimum. In diis principle lies, of com'se, one

reason for the slow recognition of die facts of color contrast:
the phenomena had seemed to occur adventitiously because theyfailed to appear in the presence of considerable differences inbrightness. (3)Given equality of brightness, then the amount of

induced color varies with the saturation of the inducing color, butthere are diminishing returns in the induction of color,which

Kirschmann found to be roughly proportional to the logaridim of
the inducing saturation.

The other reason why the phenomena of color contrast were notunderstood sooner lies in the fact that induction is greatly favoredby the elimination of contours. Here was the real point of Meyer’s
experiment in 1855. By spreading thin white paper over a pieceof gray on a colored background, he tremendously reduced thesaturation of the inducing background and yet, for all that, got amore intense contrast color in the gray. The reason escaped Ilohnholtz. He had to be content with Ac mere fact that color contrast
actually seems best for faint inducing colors. Wundt, however, got
the right principle in 1874; he noted tliat Meyer’s tliin white paper

enhanced contrast, in spite of reducing the intensity of the colors,
because it eliminated die contours tiiat make of the gray paper

an object separate from its background. In the same way Ku-sdimann's rotating disks aided contrast because rotation blurs contours. Though no one seems to have made much of this point at
first, Ti^ohener in 1901 put

down the elimination of contours as thefifth formal condition of contrast.

Nowadays Gestalt psychology

makes use of this fact to show that contrast phenomena hold better within an integrated field than from one field to another.

Hering said of contrast: the retina acts as a whole. Koffka said:
contrast depends upon the manner of organization of the per-ceptual field.

In the present century the only important advances in the knowledge of visual contrast are these indications brou^t forward by
Gestalt psychology to show that the laws hold in relation to theorganized structure of die perceptual object, and that the neurological basis of the phenomenon may lie in the brain rather than indie retina. Certainly, if contrast is dependent upon perceptual organization, it is very probable that its laws represent the proper-

INDIRECT VISION
ties of central neural action. This view is, actually, a

171

modem andsophisticated return to the orginal objection of Helmholtz, for hetoo believed that the laws of simultaneous contrast must depend

upon the brain and not upon the action of the retina.

Indirect Vision
Marimal retinal sensitivity in daylight is limited to the fovea,
which is not much more than M.000 of the total area of the sensitive
retina; yet before the nineteenth century there was almost no im-

portant consideration of the nature of vision as it occurs outside of
the immediate field of fixation. Even Mariotte’s discovery (1668)
of the blind spot in this region gave no impetus to systematic investigation.

The first experiment on indirect vision, after Mariotte’s, was dueto the habitual curiosity of Thomas Young who, in 1801, deter-

mined the range of visibility of a li^t as he moved it away fromthe visual axis. He reported the limits of its visibility as 90° out-

wards, 00° inwards, 70° downwards, and S0° upwards, stating
further that distinotness of perception begins to decrease at 5° or

6° from tile visual axis.

Upon the question of color-sensitivity

Young did not touch.
In 1804 D. Tioxler noted that peripheral images fade out very
rapidly so that, in a series of white figures pasted on a blue ground,
all but the fixated figure soon disappear. In other words,

adapta-tion in indirect vision is rapid. Troxler seems to have thought thatthe particular color had something to do with the rate of adaptation, but it is not clear how.
It was Purkinje

into the picture.

(1825) who definitely brought color sensitivity

He showed (1) that the extreme limits of vision

are approximately what Young had already shown them to be,(2) ihat visual sensitivity diminishes continuously from the center to the periphery, (3) that colors tend to change in hue, at dif-ferent places for different colors, and differently along the different

meridians, and (4) tibat aU colors tend to become gray in the ex-treme periphery. Though he is said thus to have indicated theexistence of color zones on the retina, actually aU he showed wasthat color sensitivity varies and diminishes toward tire periphery,

He coined the term indirect vision.
It was really Szokalsky 1842) who had the idea of zones. Work(172

VISUAL PHENOMENA

mg on the basis of a three-color theory of vision, Ilko most pemons
after Young and before Hering,

he reported tliat the peripheryof the retina gives rise only to black and wliite sensations, that
there is an intermediate zone which mediates blue and yellow aswell as black and white, and finally that the central zone gives red
in addition to these others. It must have been partly the operationof chance in his choice of stimuli that led him to a conclusion soclose to the later requirements of the Hering theory.

The first thoroughgoing investigation of indirect vision wasmade by Aubert (1857 et seq.), who established most of the fundamental truth about this matter. Here is what he discovered.
(1) The range of chromatic sensitivity varies with the brightnessof the color, for colors on black backgrounds are seen much farther

toward the per iphery than the same colors on white backgroimds.
This difference is of the order of the difference between 16° (rodon a white background) and 30° (red on a black background).
(2) The range of sensitivity depends upon the area of the stimulus.
The difference here is of the orda‘ of an inci'ease from 16° for a redof 1 sq. mm. to 43° for a red of 256 sq, min., whereas a stimulus of1024 sq. mm. often appeal's still in its original color at the extremo

boundary of the retina. (3) The rate of change of sensitivity is not
uniform and differs upon different meridians. (4) In general, reds

and greens pass gradually into yellow and then to gray us stimulation shifts from the center to die peripheay, whereas yellow andblue pass directly into gray.

With so many conditions of variability Aubert did not thinkitpossible accurately to map the retina into color zones.

Such

topography could have meaning only if it wore accomplished fora set of colors of the same brightness, and Aubert did not believethat colors can be precisely equated in brightness. In striking certain averages of limits obtained

under very various conditions

Aubert did not find large differences for the four principal colors.

The weight of his discovery thus told against the establishment of
retinal color zones.

He pointed out moreover, that the difference

between the center of the retina and its periphery is more one ofdegree of sensitivity than of kind. Even at the fovea coloredstimuli are seen colorless if very small, if unintense, if weakened

by contrast, or if weakened by adaptation. Thus the laws of the lesssensitive periphery also apply to the more sensitive center.

Some years later (1872) E. Landolt demonstrated further the)

COLOR ZONES

173

wide range of color sensitivity for maximally effective stimuli,
concluding—with Bonders’ concurrence
is insensitive—^that no part of the retina

to color of any hue provided the conditions are madesufBciently favorable. (This conclusion also seems to follow fromthe fact that a large sheet of color, filling the entire field of vision,

being large and therefore effective, does not allow the subject tosee his own color zones; but this obvious observation appears not
to have been made.

At this time there began to be a great deal of experimental research on the problem of the color zones. Where there had been

but a half-dozen papers in the preceding fifty years, now there

were a dozen in the decade 1871-1880 and almost as many in eachof the two following decades. Actually, as Aubert and Landolt had

shown, tliere are no color zones, not in the sense of fixed boundaries which separate funofionaliy or anatomically different partsof the retina. Sensitivity diminishes continually toward the pe-riphery of the retina, and the zonal boundaries are no more real

than the contours on a contour map. What happened was that interest in color theory became acute because of the conflict between

Helmholtz’s and Hering’s theories, and it was thought that theestablishment of fixed color zones could settle the argument one

way or the other, depending upon how the boundaries lay withrespect to one another.

Helmholtz’s theory had held the field after 1852. Bering’s theoryisdated as of 1874. Both alike were founded upon Helmholtz’s

extension of Johannes Muller’s doctrine of specific energies to the

problem of the different hues. Both appealed to the laws of color
mixture to explain how an infinitude of perceptible colors can be

mediated by very few retinal processes. Helmholtz for his part
supposed the existence of three specific energies arising respectively from the excitation of three substances in the retina—the‘red,’ ‘green’ and ‘violet’ substances. All the colors, including white,come, he thought, from different admixtures of the excitations ofthese three. Hering, on the other hand, supposed that there are
six specific energies arising from three substances,ofeach capable

two antagonistic and mutually incompatible processes—the‘red-green,’ ‘yellow-blue’ and ‘white-black’ substappes. To him it

seemed that the facts of indirect vision could furnish a decision
between these two theories by showing whether red and green are
inseparably related, as they should be if they depend upon the

174

VISUAL PHENOMENA

presence of the same substance (Hering theory), or whether tliey
are separable, as they should be if dependent upon different substances (Helmholtz theory).

The proponents of the Helmholtz theory held that the ‘red’ substance is missing or diminished in the periphery of the retina,

Some of the arguments were involved, but the theory was supposed to be supported by Aubert’s finding that red and green passthrough yellow as they fade out to gray at the periphery, whereas
yellow and blue become gray without change of hue, Schelske in1863 and Woinow in 1870 got experimental results similar to Auand used them to support the Helmholtz theory before

bert’sBering’s theory had clearly come into the field. The diminution ofthe ‘red’ substance would, of course, explain the fading of red to

yeUow, even though it would not explain in any simple manner

why green passes through yellow to gray.
Hering’s theory seemed to require that the red and greerr zones

should coincide, and also the blue and yellow zones. Szokalsky(1842) had already reported such a relation. Nevertheless it had
become plain that a color-sensitive zone can be any size at all, de-pending upon the effectiveness of the stimulus used. Tiro only possible meaning that can be given to coinddonoe between the red

and green zones is, therefore, that they should bo doterminod witli
equally effective stimuli. Aubert, who had realized that point, hadthought that the heteroohromatio equation of colors could trot bo
established. In 1881, however, seven years after Ilering had pro-mulgated his theory, Ole Bull saw that sudr a hypothesis also requires the existence of four critical invariable colors which do not^ange in hue from the fovea to the periphery. Not only should
yellow and blue change directly to gray, but there should also be a

red and a green ( the hues assodated with the isolated action of the‘red-green’ substance) that do not change in hue before they be-come gray. Bull found two such colors, a bluish green and a purplish red which, with pure blue and pure yellow, he called the“physiobgically pure” colors. Hess in 1889 confirmed these results

about the invariable hues and determined their spectral wavelengths as Mows; blue, 471 mp; green, 495 mp; yellow, 574.5 mpj
red, non-sped:|:al. Introspectively this yellow

and this blue arepure, whereas the red and the green are bluish. Hegg (1893 etseq.) and Baird (1905) obtained similar results.

When tirese four investigators used what they thought wereCOLOR ZONES

Fig. 22.

175

Colob Zombs, as Shown by Chromatic Thbesholds op Fpbreb
AND Rand (1919)

The threshalda are plotted between energy (watts) and eccentricity (defrom the fovea on the nasal meridian). The stlmi^ are 670 mu(red), 581 mu (yellow), S22 mp (green) and 468 mp (blue). A horizontal line drawn at any level shows the limits of the color zones (forthese particular stimuli) at that level of energy. The order of limits forraees

the four zones varies with the energy level, and in general zones do notcoincide for equal energy. Compare the different orders at the levels rraresented by the horizontal lines AA, BB, CC, DD. All these curves, excTOt ihe

one for green, extend as far out as 90* when they are continued to bigher
energy levels.

equivalent values of the four invariable colors, they got remarkablezonal coincidences to support the Hering theory. Typical limits(in degrees from the visual axis) occurred for the temporal

meridian as follows:

Bed

Green

Yellow

Blue

Bull

20

20

30

29

Hess

21.2

21.6

35.6

3SX)

Hegg

20

20

41

Baird

32.5

31X1

47.0

42
.

48.2

In this table one cannot, of course, compare Hess with Baird, since
their stimuli

were not equated. The point is that, for each in-VISUAL PHENOMENA

176

vestigator, the values for red

and green are close together, thevalues for yellow and blue are close together, but the two pairs
are far apart.

More recent times have witnessed the evaporation of interest
from these classical, naive theories, and with it the disappearanceof the problem of zones. No longer is it clear, in fact, just what

would be the physiological significance of the coincidence ofzones, since any zones can be made to coincide or to differ in any
desired order simply by choosing slimuH of the proper relative effectiveness. Twisting the argument around, one can even say thatthe effectiveness of each stimulus is measured by the degree of
retinal eccentricity at which its color still remains visible. At any

rate modem research, having largely abandoned the theories,

primarily concerned with theismeasurement of the phenomenal

effects of the carefully controlled variation of the physical dimen-

sions of the stimulus.

An example of the modem work on indirect cliromatic vision is
the research of Fence and Rand (1919), who detennined chro-matic thresholds for certain spectral colors along certain uu'ridians.
Fig. 22 shows how these thresholds vary for four colors along thenasal meridian. It will be seen tliat with increasing level of energy

the order of the hmits for these four colors alters fromthroughRYGB,

GRYB and GRBY, to GSRY, The more the retina isstudied, the more it is found to vary irregularly and in no such

simple manner as the early theories presupposed.

Luminosity of the Spectrum and the Purkinje

Phenomenon
The distribution of luminosity in the spectrum changes with thetotal level of energy in the spectrum, and tiiis fact accounts for the

Purkinje phenomenon. Thus the history of the luminosity curve,

the Purkinje phenomenon, and the differences between photopic

and sootopic vision is single and must be discussed all at once.
That the colors of the spectrum are not equally bright is obvious.

Newton wrote; "The most luminous of the Prismatick Colours are
the yellow and orange. These affect the Senses more strongly thanaU the rest togeffier, and next to tiiese in strength arc the red andgreen. The blue compared with these is a faint and dark Colour,

LUMINOSITY OP THE SPECTRUM

177

and the indigo and violet are much darker and fainter, so thatthese

compared with the stronger Colours are little to be re-garded.” The full import of this statement Newton could not see

because he thought of light as something that was, by its very nature, visible. It was a long time before it was realized that there isa continuum of energy with maximally visible light in the yellows,
minimally visible light in the extremes of red and violet, and invisible light beyond in the infra-red and ultra-violet regions.

In 1815 Fraunhofer, studying the problem of the constructionof achromatic lenses, realized that he must know the relative intensities of the spectral colors, since the chromatic aberrations of

the stronger colors have the greater need of correction. Hence hearranged an apparatus with a divided field, in which any chosenpart of the spectrum could be seen on one side and a white light ofvariable intensity on the other. By varying the intensity of the artificial white light, he undertook tomake it match the various parts
way he found theof the solar spectrum in brightness. In thismaximum brightness to He in the yellows, “about a third or a quartet of the way from D toward E” in terms of the letters for the
spectral lines which still bear his name. Actually this point is about

575 mg, at the point for pure yellow. The ratios of fhe intensities
of die white light equated to the colors in the solar spectrum were,according to Fraunhofer’s average of four determinations, as follows:

Spectral line:
Relative brightness:

BCD
.032

.094

,640

{Max.)

E

F

G

H

1.000

.480

.170

.031

.0056

This curve has the general shape of the present-day luminosity
curve. It does not match it exaedy, nor should it match perfectly,
for the two curves do not express identical properties of vision.

Purkinje’s classical observation was reported in 1825 in the sec-

ond volume of his Beitrdge. It is a bit of correct phenomenologicalreporting which takes up a mere three paragraphs and seems not
to have been regarded by its audior as of exceptional importance.

After noting that “objectively the degree of illumination has agreat influence on the intensity of color quality,” he went on todescribe how the colors emerge from darkness at dawn as the day

begins to break. At first there is only black and gray, with the red

appearing blackest. Then, as the li^t increases, the blues are die
firstcolors to appear in their own hues. Purkinje thus describedVISUAL PHENOMENA

178

lie ‘colorless Interval’ for low illumination, and the relative darkness of the red end of the spectium and lightness of the blue end.

Because the greatest relative change between daylight and twilight vision lies in the extremes of tiie spectrum, it is the twilightdarkness of the reds and brightness of die blues that are most
likely to be noticed.

During the next forty years there were various verifications of
the Purkinje phenomenon by Seebeok (1837), Dove (18S2), andGrailich (18S4). Aubert described the phenomenon in 1865. Mostof this discussion, however, was incidental, failing to advance theproblem.
In 1869 Vierordt measured the brightness of the solar spectrum

and obtained a curve closely resembling Fraunhofer’s. Fraunhofer

had compared a white with a color in respect of brightness; that is
to say,he had attempted a direct heterochromatic equation ofbrightnesses. This judgment is difficult, so difficult that Helmholtz
said for himself that he could not make it with accuracy. Vierordt,
therefore, tried to get the brightness function indirectly by deter-mining the amount of white light that must be mixed with each
spectral color to give a just noticeable diminution in Uio strengthof the color. This method assumes that the eilectivcncss of a stim-

ulus for color is proportional to its resistance to perceptible change

by a dilutant of constant character, an assumption natural enoughin the days when Fechner’s law was in the air. The importance ofVierordt’s determination, and of Dobrowolsky’s in 1872, is to showthat there was then a felt need for exact quantification.

Inasmuch as there was no method for determining the absolute energy of the spectrum, all the measurements of the luminosityof the spectrum had up to this time been relative. In 1883, however, Langley succeeded in measuring the distribution of energy

in the soIm spectrum by means of a bolometer. For the first time

now it was possible to determine the absolute sensitivity of theeye for different wave-lengths. It was Stranger who made this general point about the eye in 1887. If the intensity of the spectrum
is greatly reduced, it shrinks to a small luminousband near green.

Hence, Strenger argued, the eye is more sensitive to green thanto red. Newton had said that yellow is brighter than red. Fraun-

hofer had said how much bri^ter. The problem had not, however, been envisaged before as a problem of relative sensitivities,of the eye’s sensitivity diminishing from a mid-point in the spec-

VISIBILITY CURVE

179

trum to the extremes where the limits of visibility mean merdy
that the eye is completely insensitive to the invisible ‘light’ thatHes beyond the ranges of the spectrum.

Langley himself in 1888 worked out this function for the sensitivity of the eye, In preference to the direct heteroohromatic equa-tion of brightness, he used a method of acuity in which the relative
intensities of two wave-lengths are varied until die two lights giveequal visual acuity. Since he knew the absolute intensities of eachwave-length by way of the bolometrio measurements, it was now
possible for him to plot the energies thatwould give, for all

the spectral hues, equal acuities and, therefore, presumably equal
brightnesses. Such a curve would be U-shaped with a minimum inits

center. Langley, however, started the modern practice of tak-ing the reciprocals of these energies as measures of the sensitivityof the eye; as a consequence, his curve, like all the others after
it, isbell-shaped.

The most important investigation in this field of visual sensation was certainly Kfinig’s, for he systematically determined brightness and sensitivity of the eye as a joint function of wave-lengthand intensity of light, thus bringing the brightness curve and the
Purkinje phenomenon under one large generalization. KSnig foundthe distribution of brightness in the spectrum for the eight levels
of intensity that had to one another the ratios 1: 16; 256; 1024, andso on up to 262,144. The lowest intensity was approximately tire

absolute direshold. At each intensitive level he equated in bright-

ness thirteen different wave-lengths to the brightness of 535 mp.

His results take die form of the set of curves in Fig. 23, which arefor Konig’s own eye. The curves are all referred to 535

mp as unity,

which was kept at a constant intensity. For comparison colors
darker than this standard, the collimator slit had to be opened
wider, to make the intensity high enough to get a match of brightnesses.

A “brightness curve” plots the reciprocal of these observed

slit-openings. Kdnig’s curves

show how the point of maximal

brightness shifts from about 615 mp at higher intensides to about

530 mp at bwer intensities. In the set of curves of Fig. 23 the intermediate intensities seem to show a combination of the two distributions, a form of transition which has not, however, generally

been found.
That diese facts should now come to appear as functional differences between the rods and cones was quite natural. Schultze,

VISUAL PHENOMENA

180

who had distinguished between the rods and cones in 1866, hadalso suggested that the rods function for achromatic vision in

dim illumination. Others had supported this view, and there had

Em.

23.

Konig’s

Cohvis of BBicimrass fob

Ills

Own Eye(1891),

Ssowma Disthibdtion of Senstuvity fob tuc Sfsctbum at
Diffcbent Levels of Intensity, and thus the Fcdkinje

Phenomenon
The curves are for six levels of intensity, in which die lowest. A, is
about liniinal, and the highest, H, is about 262,144 times the lowest. The
curves really measure senktlvity, with 535 m|i taken as the point of reference, because they are the reciprocals of theofcollimator

slit)

necessary toamount of energy (width

make any hue appear jusl as brlglit as

the standard; but, since these ratios indirectly show laie relative brightnesses

which wave-lengdis of equal energy would have, KBnig called them “curvesof brightness.”been a great deal of discussion about the function of the visual
purple. In 1894 von Kries put the facts together into his “duplicity
theory,” which we shall have to consider in the next chapter. It
isenough for the moment to see that Konig’s data and von Eries’s

dieory belong together, and that Konig’s curves came eventuallyPURKINJE PHENOMENON

181

to be interpreted as two kinds of sensitivity curves, one for rods

and one for cones.
In a large literature there appear to have been after Konig threemain problems; (1) the relation of the Purkinje phenomenon to
the fovea, (2) the dependence of the Purkinje phenomenon upondark adaptation, aud (3) the precise establishment of the luminosity curve as a quantitative standard.

If thePurkinje phenomenon depends upon the differences insensitivity of the rods and cones, then it ought not to occur in the

fovea where there are no rods. On this problem there have been

many experiments, with conflicting results. Koster (1895) and
Sherman (1898) reported finding &e phenomenon in the fovea;
other studies, including a veiy careful experiment by von Kries

and Nagel (1900), contradict these findings. In this case theburden of proof does not lie with the negative finding. If the fovea
isdefined too generously so that the region of stimulus-projectionisnot strictly within the rod-free area of the retina, or if fixationis

not rigidly maintained so that die stimulus-projection wanders

outside the rod-free area, then the Pmkinje phenomenon could

appear as an artifact. Von Kiies and Nagel failed to find it withcareful fixation within a two-degree field,

and this result seems

likely to remain correct.

Hering ( 1895 ) argued that the Purkinje phenomenon is the consequence, not of the low illumination of the stimulus, but of thestate of dark-adaptation of the eye. Thus he was opposed to theHelmholtzian tradition which found its culmination in Eonig’s
work. That dark-adaptation favors the Purkinje phenomenon had
long been known. Purkinje himself described the phenomenon
for the twih^t of dawn (when the eye is, of course, dark-adapted)

instead of for the twilight of evening. Parinaud in various articles(1881 et seq.) had argued that the visual purple is essential todark-adaptation. Now (1895) he held that the visual purple is acondition of the Purkinje phenomenon. Although there were in the
1890’ssome researches indicating the similarity between thelight-absorption cui've of visual purple and the sensitivity curvefor faint light, the confirmation of thisview has been recent(Hecht and Williams, 1922). Since the absorption values of thevisual purple would tend to create the Purkinje shift and since thevisual purple is associated with the rods, the theory is convincing.

182

VISUAL PHENOMENA

That does not mean, however, that Bering was right and KSnig
wrong, but simply that KHnig and the others of tlie Helmholtzianschool measured the sensitivity of the functioning rods, whereas

dark-adaptation is a condition for their functioning. It

is

gen-

erally supposed now that cone and rod vision overlap throughout

a very wide range of illuminations, and that any person indoorsissomewhat dark-adapted.
So well accepted nowadays is the dual functioning of the eyethat Parsons (1913) introduced the term photopia for daylight(presumably cone) vision and scotopia for twilight (presumablyrod) or dark-adapted vision. The “brightness curve,’ ‘sensitivify
curve’ or ‘luminosity curve’ has come fairly generally to be known

now as the mibUity curve. In 1^0 the Illuminating Engineering
Society of America adopted a standard visibility curve for photopic
vision, a table of coefficients that can be applied to an energetic

spectral distribution in order to get its total photomcU'ic (bright-

Hecht and Williams (1922) have determined bothphotopic and scotopic visibility curves, the values for which areness) value,

now often used in the computations for other research. In sharp
contrast with the untechnical phenomenology of Purkinjc and thesimple computations of Fraunhofer ai'c the assuiance and complication of modem technique.

The eye (hke the ear; see p. 339) is a very sensitive organ. Langexperiment showed that the retina at 550 mp can be excitedby three-thousandths of a millionth of an erg (3111''’ 6rgs) of
ley’s

X

light. Others have obtained similar values. The latest for

510 mp,got by Hecht, Shlaer and Pirenne in 1941, lies betweenX2and 5 X 10"” ergs at the cornea and even less at the retina. This
minimal value represents only from five to seven quanta of light.

Color Blindness

No other topic in the field of color vision has created so muchinterest as color blindness.

Because it is a common defect that

leads to amusing mistakes which may neverthelessexist unsus-

pected in its possessor, the topic has interested the layman. For

thesame reasons, h has interested the general scientist, who was thus
sometimes drawn into investigating it or inventing

a test for it.

Psychologists it interested because it was obviously

related to thenormal color blindness of the peripheral retina andmight be re-COLOR BLINDNESS

183

lated to the noimal color blindness of scotopic vision, and becauseitseemed to bear even more directly upon the question of retinal

color theory, upon the decision between the Helmholtzian threecolor theory and the type of theory fliat was held by Hering. Yet

not only did these theories stimulate interest in color blindness;

On the Helmholtzian view there
would be three color substances, one for red, one for green, one

they also biased the findings.

for violet. Since

presumably any one of them might alone be

missing, there could be red-blindness, green-blindness, and per-haps also occasionally violet-blindness. Hering’s theory required
red-blindness and green-blindness to go together; that is to say,there should be blindness to both red

and green when thesecolors are affected at all. It was not so much that the proponents
of one view or the other found what they looked for; more often

they presupposed one theory or the other and analyzed their results in respect of the theoretical hypothesis. At any rate, interest

was keen. Konig, in his bibliography of vision in 1896, gave about
twelve hundred citations of the literature simply on the topic
of color blindness— about one-seventh of all his references.

He

found oighty-eight papers to cite for the year 1881, a year which
represents the peak of proliflcity.

Although color blindness is probably nothing new in the hu-

man race, it is hard to know what account of deficient visual capacity should stand as the first recorded instance of this defect.

For example, there is the letter printed by the Royal Society from"the great and experienced Oculist, Dr. Turbervile of Salisbury,”

who reported in 1684 the case of a girl who saw "no colour besideBlack and White.” That phrase, however,ifcorrect, indicates

total color blindness, whereas it is partial color blindness that, be-ing common, has created the most interest. The first indubitablecase of partial color blindness was reported in 1777 by Joseph

Huddart to the chemist Joseph Priestley (the author of the bookon vision, light and color in 1772). Huddart described the case ofa shoemaker who had observed that “other persons saw somethingin objects that he could not see.” In seeking the owner of a child’s

stocking, which he had found, ho noticed that “people called it ared stocking, though he himself did not understand why they gaveit that denomination." Asa child he had been able'to distinguishcherries on a tree only at close hand by their shape, whereas otherchildren could see them at a distance. After this case of Huddart’s

VISUAL PHENOMENA

184

there appeared during a few years descriptions of several otheroases of color blindness. Scientific interest, however, was not fully

aroused until Dalton described his own case.
In 1794 John Dalton, a young man of twenty-eight who wasshortly to become die author of the atomic theory in chemistiy anda scientist of great influence, presented to the M,anchestor Literaryand Philosophical Society an account of his own color deficiency.
It is easy to see, when we read his report, why so great an incapacity existing unsuspected in a person of ability should excite
interest.

For instance, in discussing the reds, Dalton wrote: “Allcrimsons appear to me to consist chiefly of dark blue: but manyof them seem to have a tinge of dark brown. I have seen specimensof crimson, daret, and mud, which were very nearly alike. Crim-son has a grave appearance, being the reverse of eveiy shewy andsplendid colour. Woollen yarn dyed crimson or dark blue is die

same to me.

.

.

.

The colour of a florid complexion appears tome that of a dull, opake, blackish blue, upon a white ground.
Blood appears to me red; ... to me it is not unlike that colour.

called hottU-gteen" Dalton gave his defect scientific status

.

.

by

studying it and describing it. Ho concluded that “in the solar

spectrum three colours appear, yellow, blue, and purple. The twoformer make a contrast; the two latter seem to differ moro in degree than in kind,” Thus later it was possible to conclude that

Dalton had “dichromic vision” diat is to say, blind to the reds

and greens, he saw only the yellows and blues. Dalton, supposing that his defect might be due to the absorption of certain colors

by the ocular media, provided for a post-mortem examination of
his eyes. The examination was made and his theory disproved.
Still othercases of color blindness were brou^t to the atten-

tion of the scientificworld in the early part of the nineteenth

Goethe discussed two instances in Zuf Farberdehre( 1810 } The term Daltonism was first applied to the defect in 1827.

century.
.

As we have already seen in the last section, Seebeck in 1837
confirmed Purldnje’s observations on twilight vision. This studyof Seebeclds was in addition really a thoroughgoing investigationof color deficiency. In it he argued that color blindness is of two

kinds one, where the defect is associated with the visibility of the:entire spectruril; the other, where it involves the shortening of thespectrum at the red end. Since red-blindness would give a short-ened spectrum, such a view may be taken as an anticipation of theCOLOR BLINDNESS
distinotioii

185

between green-blindness and red-blindness respec-tively. Actually

we know now that Seebeck’s dichotomy was die

anticipation of the distinction

between deuteranopic and pro-tanopic red-green blindness, as von Kries established the facts

much later.
Though it is easy to find out what portions of the spectrum arevisible to the color-blind, as Seebeck did, it is hard to know justwhat it is that the color-blind person sees in the visible portions.
Nevertheless, in 1845 Sir John Herschel formed the inference thatthe color blind have what he called “dichromic vision,” tliat is tosay, they see in the spectrum only two colors, yellow

and blue.

Dichromic vision is, in short, red-green blindness, and Hersdiel’sview is consistent both with Dalton’s confusions (botOe-green
blood) and with Dalton’s conclusions (that he saw yellow, blue,

and a purple which is a weak blue). The history of the knowledgeof color blindness might have been str aight going had it not now
become complicated by the Young-Hehnholtz ‘trichromic’ theoryof vision.

Helmholtz advertised Thomas Young’s views and formulated
the three-color theory in 1852. Clerk Maxwell supported Helmholtz. In 1855

George Wilson published a book, Researches on

Colour-Blindness, in which he supported the three-color theory

and argued against Herschel’s dichromic theory. Maxwell had
written him a letter supporting his view and describing tests ofcolor blindness with rotating colored disks (“Maxwell disks”), andWilson published this letter in his book. Wilson’s argument wasthat Dalton was green-bHnd, but not red-blind—this in spite of
Dalton’s confusions of red with green and in spite too of the in-cident of his wearing about the streets his scarlet doctoral gown

conferred upon him by Oxford, wholly unaware of its striking incongruity with his habitual Quaker garb. This belief of Wilson’s

about Dalton was a case of theory affecting conclusions. Most people were coming around to a belief that there are only threekinds of nerve fibers originating in the retina and, in conse-

quence, that the eye can ‘see’ only three colors, red, green andviolet. Hence it would follow that color blindness must be due tothe lack of one or more of these colors, like red, or green, but
hardly to a lack of both, for then all vision would be violet. Thusitwould not be possible to perceive yellow, a mixture of red andgreen, if one were blind to both red and green.

VISUAL PHENOMENA186

At this point in the history terminology becomes confusing.
Helmholtz and Maxwell supported a theory of normal vision that
others sometimes called “trichromic.” Heischel for his part heldthat inasmuch as only

twocolors are seen, color-blindness

is“dichromic.” The implication of Herschel’s view is that normal
vision is tetrachromic, but that in dichromic vision

two colors

have been lost. On the Helmholtz-Maxwell view likewise it would

be logical to say that a color-blind person has ‘dicromic’ vision,
since he would be supposed to see one less color than the threewhich are normal. In actual usage, however, the word dichromic
was employed as meaning that only yellow and blue are seen.

The year after the publication of Wilson’s book, Pole describedhisown cobr-blindness, reaching the conclusion that his vision

was dichromic; in other words, though blind to red and green, he
could see yellow and blue. His case continued in the literature.

Maxwell thought him red-blind, whereas Holmgren subsequently
classified him as green-blind.

Much later (1893) Pole attempteda summary of the whole argument about himself and persisted in
his former notion that he was red-gi-een-blind, wherolo Holmgren

now agreed.
In 1880 the dichromic theory received support from von Hippel’s description of a case of monocular color blindness.

Hero atlast was the opportunity for getting a direct comparison between

what is seen by the color-blind eye and by the normal eye. There
had been another such case reported earlier and there were presently to be still others, but von Hippel’s account was especiallyclear and convincing, His subject could see all colors with his left
eye, He could see yellows and bbes with his right eye, but notreds and greens. Von Hippel put him through eight tests. Holm-gren at first drought him red-blind, only later agreeing drat hewas bhird to green also.

The practical concern with color blindness as well as the theoretical interest in it created a need for tests.

The earliest was theconfusion test, which simulated the conditions originally leading
to the discovery of color blindness. Wilson had shown that

objects

can be named correedy as to color on the basis of other than theirchromatic attributes; grass is green. Thus good tests
jects which are different in color andrequire ob-

yet alike in such other re-spects as shape, texture, touch and smell, Wilson

had for this pur-pose used colored yarns, a procedure which Holmgren

developedDICHROMATIC VISION187

In 1874 to careate the test that bears his name. The contrast colorsof shadows had also been used to test for color blindness, forshadows meet these specifications perfectly. In 1880 Stilling established what he called “pseudo-isochromatic*

tests, inwhichpatterns of spots, varying in hue and brightness, present a figurethat stands out from its background in terms of hue alone. These
charts can be constructed so that the figure will be seen only
in normal vision, or else only in color blindness of

one type or

the other. The Ishihara tests are the modem form of Swing’s
invention,and the Nagel cards were a variant of it. Lord Ray-leigh in 1881 setup the conditions for what was called laterthe “Rayleigh equation,” which specifies cmcial conditions formatching colors that involve both red and green in order to measure the relative strength' of these two factors in color mixing.

Though the test presupposed the three-color theory, according
to which red

and green vary independently, actually his results

showed, not only that the two may vary independently, but alsothat color blindness is not an all-or-none affair.

While these somewhat uncertain tests might have to serve fordeterminations of color blindness in railway engineers and forother practical uses, it was obvious that, b^ore color blindness

could be understood scientifically, careful quantitative measure-ments were needed. In this work Konig, who belonged to theHelmholtz school, was the pioneer. The first important researchhe published with Dieterici in 1886. They undertook to measurefor normal and color-blind persons the intensitive distribution of

the Grundempfindungen in the spectrum. Whether one held to

Helmholtz’s or Hering’s views about the physiological action of
the retina, Newton’s great fact remained true, that one can get all
the colors from a mixture of three properly chosen wave-lengths.

Konig and Dieterici undertook to find what three basic wavelengths would be most satisfactory to use for a system of mixtures,and how the response of the retina to intermediate wave-lengths
isrelated quantitatively to its response to these tiiree. In otherwords, they undertook to work out, by way of spectral color
matches, sensitivity curves for three hypothetical basic frequencies

which correspond to the three modes of excitation positedby the Young-Helmholtz theory. Inasmuch as they confirmed Newton’s assertion that any color can be got from a proper combination of a proper three colors, they therefore proceeded to char-VISUAL PHENOMENA

188

acterize normal vision as trichromatic. Thus pei-sons with normal—and—that partiallyvision camo to be called trichromats. They also foundthis isthe important matter for our present discussion

color-blind persons can match the entire spectrum with the proper

combinations of a proper two colois; hence partial color blindness

they called dichromatic vision and the persons dichromcts. (So it

happens that the “dichromic vision” of Hersohel and the “dichromatio vision” of Konig have almost opposite meanings, for Herschel meant that one sees two out of a total of four colors,andKonig meant that one gets all the colors he sees from two out of a
total of three stimuli.) Even though Heiing remained critical, theimportance of Kdnig’s work was recognized, not only by Helmholtz, but also

by von Kties and Nagel. As a consequence theweight of opinion was thrown to die color-matching tedinique,which in turn seemed, though incorrectly, to imply the truth ofYoung-Helmholtz theory.

The effect of von Kries was in many ways that of mediator between Helmholtz and Hering. Hore in the mailer of color blindness he could accept the finding about dichromatic vision,
still

and

be concerned about what dio color-blind actually see. It was

he who directed attention again to the distinclion that had been

made by Seebeck between the color blindness of tlie shortened
spectrum and that of the full-length spectrum. As we have soonin the last section, in 1894 von Kries propounded his duplicity

theory concerning the rods and the cones and die different brightness distributions, as found by Kdnig. In 1896 von Kries and Nagel

went on to measure the brightness distributions of some dlchromats. (Nagel himself was a dichromat.) Thus it became clear that
Seebeck’s two kinds of color blindness were accounted for by thefact that some dichromats have die normal (photoplc) distribution of brightnesses for the spectrum, whereas others

have thePuikinje (scotopic) distribution. The latter kind of color blindness von Kries called protanopla, and the persons protanopes, be-cause he thought of the scotopic type of sensitivity as more primitive. The other kind of color bliniiess he called deuterarwpia andthe persons deuteranopes, because he regarded this type of sensitivity as derived.

A protanope, then, has his red so dark that red

appears to be missing; his spectrum is shortened and he might beAcalled red-blind.
deuteranope sees the whole extent of thespectrum; the reds appear as poor yellows since the basic red is)

TYPES OF COLOR BLINDNESS

189

not in the spectrum, and the greens ( darker than in the protanope
so gray that the subject rai^t be called green-bhnd. It was vonKries’s point that protanopes and deuteranopes alike ate blind tobodi red and green.
It was just after this time that color weakness was establishedasa common phenomenon. Although it was now dear that both

deuteranopia and protanopia are forms of red-green deficiency, itremained for Nagel to show that there are many intermediate

anomalous cases, where vision is trichromatic, but where the subject has diminished sensitivity to green or to red. Von Kries called

these cases “deuteranomalous trichromacy” and “protanomalous

trichromacy." The anomalous trichromats turn out to be fully as

numerous as die dichromats. Thus Hering was justified in his
contention that dichromatic vision is blindness to both red andgreen, but Helmholtz was also justified in claiming that sensitivity
to red and to green may nevertheless vary independently. It was

Lord Rayleigh (1881), as we have seen, who first made this discovery. Since then S. P. Hayes (1911) has shown that dichromatic
vision can be regarded as Ihe limit of die variation of trichromatic
vision, a view to which S.

W. Terman (1929) has added support.

In reviewing the development of knowledge about the usualforms of pai'tM color blindness, we have had to ignore many isolated facts of minor significance in the trend of thought. ( 1) Thereisa literature of what is called by the Hering school blue-yellow

blindness (supposing that the blue-yellow substance is lacking

from the retina) and by the Helmholtz school violet or blue blindness (assuming that the violet substanceislacking from theretina). It is a confusing literature, wherein cases are not clearly

established and theory has aflfected conclusions on many occasions.

(2) For all that there is no doubt about the existence of

total color blindness or

monochromatic vision, not more thaneighty cases had been reported when a survey was made someyears ago, and there are complicating factors that have prevented

any positive conclusions on this subject. Since foveal vision is diminished, there is the implication that the monochromats may haveto rely more on their rods than do dichromats. (3)There are re-ports of the sudden acquisition of partial color bUndness as a resultof accident or eye-strain, but these cases lack the detailed investi-

gation that mi^t make them fit die total picture. (4) It is established that dicbromacy is much more common in men than inVISUAL PHENOMENA

190

women, and that it follows approjdmately a sex-linked form ofinheritance. Laterallthese facts

may enter the history of thepsychology of vision in some dynamic way, influencing thought,
occasioning a theory or explaining some other phenomenon. At
present, however, they are about as isolated as was Seebeck’s clas-

two Idnds of color blindness in 1837 before

sification of the

von Kries found its significance sixty years later.

Notes
Joseph Priestley's historical text is

The History and Present State of DisVision,

coveries Pelating toPeiresc, Boyle,de Godart,

etc.,

see

Plateau.

Athanasius Kircher’s bookLigiitisArs

and Colours, 1772, 812 pp. The bookmagna hois el umbrae, 1640, [n.v.].

examines the history of vision {torn

For his wager about tire after-images,
see p. 162. His theory that die eye
might give out light ns well ns absorb it was not slrangc for that time.
Even as late as 1834 a man claimed incourt to have recognized an assailant

objective or physical point oftheThe history of the discovory

view.
of

subjective

visualphenomenaisbrought together by J. Plateau, Biblionapbie analytique des pcincipaux
phenomines subjectifs de la vision,
depuis les tomps anolens jnsqu’a lafin du XVUIe siecle, suivle d'une
bihUograpbie simple pour la partlo
Acad.
toul& du si4cle actum,Mm.

wlio struck him in the oyo in tho dark

because the blow on tho eye createda flash of light snOlclenl Ui illumino
the features of the assailant; sueJ.

Mtiller in bis Jnhrosboi'Ichl for 1833,

2 ser., 42, 1878, the first
five memoirs, separately paged, 266

Arch. Anat. Physiol Leipzig, 1834,
140 f.

pp, altogether. The blbliographie
analytique gives full abstracts of more

spectra of die suns image, see D.

toy. Belg.,

For Newton’s c.X]5eriments on thethan a hundred papers before 1800,

Brewster’s

and the reader must so to this source
for the references and for the full ac-

lettercount of the discoveries and opinions.

spectra produced by the action of the

The bIbUopaphie simple is Just a list

sun’s lighton the retina, Edinb.

of more timn 700 papers after 1800

Sci., n,s. 4,1831, 75-77.

with simple annotations for someitems. Later thereis,KSnlg’sbibliographyclassifiedof course, A.

of

7833 tides in H. L. F. v. Hehnholtz,

Btmdbuch der physiolaglschen Optik, 2 eA, 1893.

L

publication of Newton’s
Locke, written in 1691;
Newton, Experiments on oculai'totext are;J.

Jurin, An essay upon dis-and indistinct vision, which isprinted as an appendix to Hobert
Smith, A Compleat System of Opticks, 1738, Bk. 4, 115-171, esp. 168171; C. L. L. Buifan, Dissertation
tinct

sur les couleurs acddentelles,

After-Images

1.

'The later papers mentioned in theMSm.

Acad. Sci., 1743, 147-158; Benjamin

For the history of discovery, seePlateau’s Bibllographle, op.
first

ctt.,

the

three memoirs; also H. L. F. v.

Helmholtz,

PhyHologilod

Optics,trans. 1924, U, 261 f. For the refer-

ences

to

Ptolemy,Agudonius,deFranklin, letter to Lord Karnes, June2, 1765, printed in the later editionsof [Netof Experiments and Observations in Electricity, 4 ed., 1769, 469,

1774, 48‘7 f., and reprinted in the A. H, Smith and theIn.v.], or 5 ed.,

;)

NOTES
Bigelow editions o( Franklin’sJ.
works (it was just a paragraph, but
it was an important (act noted by animportant man, and it got attention )191

und die Funktion der Stabohen undZapfen, Ergebnisse der Physlolagie,I.

Pt 2, 1902, 694-800 ( bibliogra^yof 274 titles).

Charles SchetSer, AbMfldiung con

Hermann Aubert’s pioneer hook is

den no/Siiigen Farben, 1765, [n.v.],
French trans., ObserooHons aur hphysique (de Bozier), 26, 1785, 175-

Fhysiologie der Netahaut, 1865, butbisGrundxuge der physiohgischen
was also very impor-

Optik, 1876,

W. Darwin, Newtant Aubert established the concept

experiments on the ocular spectra ofof adaptation, invented the episcotis-

187, 273-290; R.

and

light

Phil Trans., 78,
313-348,colours,

Pt. 1, 1786,ter(adjustable rotating sectors fordiminishingintensityofavisualThe general orienting articles bystimulus behind them), and invented

Plateau and Fechner on this topic

the Aubert diaphragm (square dia-axe: J. Plateau, Easai d'une theortephragm adjustable to any area because it consists of two overlapping

gdndrale comprenant ensemble desapparenccs visuelles qui sucoMent
it lacontemplation des objets col-pieces that slip together or apart alongordes, et de celles qui accompagnent

a diagonal of the square as an axis).
Ewald Hering wrote Zur Lehrecette contemplation, Mem. Acad, toy.

com Lichtsinne in 1872-1874

Bele., 2 ser., 8, 1834, 68 pp. (sepa-

unaltered printing, 1878). His later(

2nd

rately paged); G. T. Fechner, Ueber

views appear in his posthumously

die subjektiven Complementiirfarben,

published Grundmge der Lehre vom

Ann. fhys, Chem., 120, 1838, 221245, 513-535; Ueber die subjektiven
Nachbilder und Nebenbilder, ibid.,
126, 1840, 193-221, 427-470.

Llchtslnn, 1920. In part because herepresented

phenomenologicalthetradition and opposed Hebnholtz, his

infiuence was much greater than theextant of his writings would lead one
to expect.

Adaptation

The

later

classical

papers from

There axe three German words. ( 1Nagel's laboratory on da»-adaptation

Akhmmodation was fixed by Ildm-

and light-adaptation ate: H. Piper,
Ueber Dunkeladaptation, Z. Fsycnol,
31, 1903, 161-214; W. Lobmaim,
Ueber Hefiadaptatlon, Z. Sinnes-

holtz as the adjustment of tlie lensand ciliaty process to changing focal
length, but Johannes Muller andothersbefore Helmholtx usedthephysiol., 41, 1906,

290-311,word in the sense of (2). (2) Adap~
tation was fixed by Aubert for ad-adaptation is S. ETxner, Ueber einige

justment to the intensity of stimula-neue subjektive Gesichtsetschelnun-came togen. Arch. ges. Fhyslol., 1, 1868, 375-

mean adjustment to the intensity of

394. Tlie next early paper on this sub-white, black or color; nevertheless,

ject is John Aitken, Colour and colour

tion,

and

after

tieringit

before Aubert it was sometimes usedin the sense of (1). (3)Anpassungmeans biological adaptationof therace or individual to his environment,

but Hering used it in the sense of(2). Adaptation (2) is also someIn general on the facts and history
the experimental psychology ofadaptation, see A,

initialpm>er

on chromaticsensation, Trotw. toy. Scot, Soo. Arts,
8.

1873,

375-418,esp.

396-405,

where be showed tiow waptatian toone color changes the appearance ofother colors. The paper by G. J. Burcb
isOn

artificial

temporarycolour-blindness with an examination of thetimes called Vmstimmung.
ofThe

colour sensations of 109 persons, Fhil.
Trans.,

191 B,

1899, 1-34.

Burch

Tsenermak, Diegives colored plates which show how

Auges

3ie spectrum looks to persons with

Hell-DunkeladaptationdesVISUAL PHENOMENA

192
coijiplete

adaptabon

particularfoi

menls upon coloured shadows,

Phil.

spectral cclors. The recent phenomenological descripbcn of the pocesa of

Trans., 84, 1794, 107-118,
The nature of M. E. Chevreul’s

chromaUc adaptabon is H. Sheppard,

work is shown by its full bile: Do
la hi du contraste sinmltani descouleurs, et de Vassortment des ob-

Foveal adaptation to color, Amer. J
Tsychol, 31, 1920, 84-58. L. T. Trohnd’s contradiction of the findingthat all cobrs adapt completely into
gray

if

colorsgiven time enough is: The
produced by eqidlibiium

photopic adaptabon, J. exp. Fsychol,
4, 1921, 344-390.

wascohris, constdire d’opiis cetlelots

loi dans ses rapports aoec

h peinture,des Gobelins, lestapisseHes de Beauvais pour meubles,
lestapisseiles

les tapis,

lamosatque,lesoitraux

coloris, timpiession des itoffes, Vim-theprimerie, Tenhminure, la dicoratlon

first

to indicate that, eaeept for cer-des edifices, thabiUement et Vhorti-

tain

primary

Emer’s paper, op.
colors,dt.,

allcolors shift

in hue under adaptation. This conclu-

sion was seemingly confirmed by C.

Hess, Ueber die Tonanderungen derSpectralfarben dutch Ermbdung der

Nebzhaut mit

homogenem

Lichte,culture, 1839.
Sir Thomas Young’s tlieoiy of sympathebc adaptabon is in his A Course

on Natwal Fhthsophij
and the Mechanical Arts, 1807, I,
455. For the reference to Fochner onof Lectures

Arch. OphihaL Berlin, 36 (1), 1890,

Nebenbllder, vide supra.

1-32, and by H. Voeste, Measende

The crucial experiment of II,
Meyer is Ueber Contrast- odor Complemonlarfarbon, Aim. Pht/s. Chen.,Versuehe liber die Qualitiltsbderungen der Spectralfarben in Folge vonErmiidung der Netzhaut, Z, Fsvchol.,
18. 1898, 257-2Y8. Troland and C. H.

171, 1855,

nOf,

For Helmholtz on contrast, see his

Langford eaplain this result away as

Phi/siologlcal

an artifact of the Eezold-Brttcke
henomenoni cf. Troland, op. ctt.,

1924,

sect.

trans.

Tins seebon has a lair Ibstori-?80.

cal account of the problem

Optics,II,[18001

24, 264-301 in Iho Eng.

upin

1860. Helmholtz's doubt about thesensory actuality of conbast runs all

Contrast

the way through the seebon: he ad-

For the early history of contrast,

mits contrast, yet tries to argue

it

see Plateau, op. cit., the fifth memoir,away. The explanation as illusion ofand for the history of the theory of

judgment comes in here, as does also
his puzzle about Meyer's experiment
For Helmholtz on unconscious infer-colored shadows, see {bid., the sixth
memoir. Here lie the references toAristotle,
Albazen,
Leonardo daVinci, Halley, Buflon and manyothers. The quotation from R. W.
Darwin is from his op. ctt., 345.

The

ence in general, see ibid., HI, [1866]

A

His1925, sect. 26; E. G. Boring,
tory of Experimental Psucholoiu,

1929, 300-304.

eighteenth century book on

For the reference to Hering, seecolored shadows is H. F. T., Oiseroations

m Us ombres

his Zur Lehre vom Uchfsinne, 1872-[n.v.].

The paper offamous

1874, esp. Mittheilungen 2 and 3,
1873. For Hering on contrast induced

scientist, Benjamin Thompson, Countwibi colored shadows and also somemore attenbonof his cribcism of Helmholtz, see his

Rumford,deserves

colories, 1782,

thedian it has had, for it established con-Ueber

trast as a suhjectike phenomenon, dis-Contrastes von Helmholtz, Arch. ges.

covered synthetizlug oondibons tor it,

Physiol., 40, 1886, 172-191,

and related the cmored shadows tocontrast: An account of some experi-of brightness oonbust are: A. Leh-

die Theorie des simultanen

The classical experimental studies

NOTES
Ueber die Anwendang der
Methode dei mittleren Abstufungenauf den Llchtsinn, Pbii. Stud., 3,msirn,

193

Ser, 1

Kmgr. exper. Psychol., 1904,

10-13, and cf. 20 f. Similar instances
are mentioned by C. E. Ferree and G.

Hand, Some areas of color blindness

1886, 497-533, esp. 516-528; C.
Hess and H. Pretori, Messende Untersuchungen uber die Gesetzmassig-of an unusual type in the peripheral

keit des303. On the general role of the brain

simultanen Helligkdtscon-

trastes. Arch. Opthd. BeiUn, 40

retina, J. exp.

Psychol, 2, 1017, 295-

(4),
1894, 1-24. A. Kiisohmann’s experi-in the perception of color, see alsomental study of color contrast

physiology, II, 1930, 192.

is

L. T. Troland, Ptindphs of Psycho-

Ueber die quantitativen Verhaltnisse
der simultanen Helligkeits- und Farbencontiastes, Phil.

Indirect Vision

1890,

Stud., 6,

417-491. Another classical study ofcobr contrast is II. Fretori and M.
Sachs, Messende Untersuchungen der

Excellent

accountsofandhistoricalthecritical

experimentalre-search in the chromatic sensitivity ofSimultancontrastes, Arch. get. Phus-

the peripheral retina are given

iol, 60, 1895, 71-90; but mis study,J.

being based upon Hering’s concep-of the Periphetal Retina, 1805, 7-41,

tion of valences, lacks the permanent

and G. Hand, The factors that infiuence the sensitivity of the retina tovalue of Kirschmann's.

by

W. Baird, The Color Sensitivity

On the elimination of contours ns acolor, Psychol Monogr., 15, 1913, no.

condition of contrast, see W. Wundt,

62, 0-78. The former is more histori-

Grmdxiige der nhysialogischen Psy-cal,dhologie, 1 ed„ 1874, 415 f.; E. D.

critical.

Titohener, Experimental Psychology,

the latter more constructive and

For Thomas Young on the range of
see his On lire mechanismof the eye, PM. Trans., 91, 1801, 23-

20 f., Pt. ii. 34 f. St
tire other hand, one finds no serious
consideration of this principle in dte
handbooks of Helmholtz (1660),
AubertWilliamJames(1865),
Nagel
Kulpe(1892),(1890),

vision,(1905), and Ladd and Woodworth(1911), although all these texts discuss the laws of contrast. On the way

gebener Gegenstande innerhalb un-

I,in

1901, Pt.

1.

which Gestalt psychology

finds

contrast involved with the principles

ofperceptual

integration,

see

K.

Koffka, Principles of Gestdt Psychol-

ogy,

1935,

I&iffka’sbook

133-188.
carriesOf
allcoursethewaythrough the implication that theseperceptual integrations depend mostly

on the laws of the brain and not the88, esp. 44r-46; reprinted in Miscel-Works of Thomas Young,
1855, L 12-63, esp. 30 f. D. Troxler’slaneousstudy is Ueber das Verschwinden geseres

Gesichtkreises, in

Himly andSchmidt’s Ophthalmologjmhe Bibliothek, 1804,
J.

n, Pt 2, 1-53, [n.v.l.

E. Furkinie’s account of indirect

vision is in his second volume, Heue

BettrSge zur Kenntniss des Sehens insubjectiver Hinsicht, 1825, 1-31.

V. Szokalsky

iscited at second-

hand from Baird, presumably his
Ueber die Empfindang der Farben
in physiologtscher und pathologischer

laws of the retina.
The argument for contrast’s being

Hinsicht, 1842, [n.v.], since his Essaia central neural phenomenon orig-

which r^rints the nine papers ofAnnales if oculistique, 2 1839, and 3,
1840, does not have tliis discussion

inates in the special case of Schu-mann’s vision. lie was blind to green
but perceived, for green light, red
after-images and red contrast sensations. See F. Schumann, Ein ungewiilinbcliet Fall von Farbenbhndheit,

sur les sensations des couleurs, 1841,,of the color zones.

’

H. Anbert’s basic paper for this
topic is Ueber die Grenzen der Far-benempfindung auf den

seitbehenVISUAL PHENOMENA

194

the figures in the text are translated

Theilen der Hedna. Arch. Ophthal
Beilin, 3 (2), 1857, 38-67. See also

into visual angles from Hegg’s di-his Untersuohungen uber die Sinnes-

mensions of the visualthdbgkeit der Netehaut, Ann. Phys.
Chem., 191, 1862, 87-116, esp. 99-

Baird’s confirmation of Hering, see

field.

For

op. cit., 42-74.

modem

113; also Aubert’s own summary of
the facts in his Phusiolo^c der Netlr

point of view on chromatic indirect

hmt, 186S, 118-124. Baird, op. cit.,

vision, see C. E. Ferree and C. Band,11, cites five other relevant references,

Chromatic thresholds of sensationfrom center to periphery of the retina
and their bearing on color theory,
Psychol Reo., 26, 1919, 18-41. The
figure of the text is adapted by changeof scale from their Chart III.

none later than 1876.
E. Landolt's work is scattered, but
his most inclusive article on Indirect
vision is 11 perimetro' e la sua appli-

cazione. Arm. Ottolm.i 1, 1872, 465-

For the example of the484.

For the early papers supporting theHelmholtz theory from the facts on

Luminosity Curve andPurkinje Phenomenon

indirect color vi^ou, see B. Schelske,

Zur Fnrbenempfindung, Arch. Oph-

Two historical accounts are L. L.

3), 1863, 36-62, esp.

Sloan, The effect of intonsily of light,

thal, Berlin, 9(39-49; M. Woinow, Zur Farbenemp

state of adaptation of the eye,fore the theory

andon the vial(n study of the Purkinjo
phenomenon), Psyc/iol. Manogr., 38,
1928, No. 1. 7-40, and the sboiter
E, M. Chamberlain, A Study of theveloped)Purkinje

findung,m., 16 (1), 1870, 212-

size of pholometiic fieldbility curve

224.

One of the first papers to provide
support for the Hering theory (be-had been fully dewas H. Schirmer, tJeber
erworbene und angeborene Anomalien des Farbensinnes, Arch. Oph19 ( 2). 1873, 194-235.
Schirmer determined the order of thethal. Berlin,

Phenomenon with Sjiectral

Lights, 1911, 2-10. One also finds agood deal of history in W. A. Nagel’s
account of the duplicity tlicory in relation

to twilight vision, inHelm-color zones asholtz’s

Physiological Optics,

3

concluded that in cases of atrophy

D, [1911], Eng. Irans. 1924, 343394 [290^32 in the German], andG, R, Y and B fromthe center to the periphery, and heof die optic nerve the zones shrink

and disappear, maintaining the sameorder, die Bull's most informative
paper on the zones is Studien liher
Liwtsiim und Farbensinn, Arch.
Ophthal Berlbi, 27 (1), 1881, 54154, esp. 135-154. See also his Sorla pdrlmftrle au moyen de pigments

octmt.

Fa^,ed.,with respect to the recent history inthe computation and correction of thevisibility curve, in

W. W, CoUentz

and W. B. Emerson, Relative sensibihty of the average eye to light ofdifferent colors and some practicalapphcatlons to radiation problems,Bu«, U.S. Bur. Stand., 14, 1917, 167-

24. Ihe classical paper for C. Hess

236 ( also called Scientific Papers of
the Bureau of Standards, No. 303).
For Newton on the differences ofon this topic is Ueher den Farbensinn

brightness among the colors, see his

bet indirectem Sehen, Arch. Ophthalures in the text ere taken from Baird,O^cks, 1704, Bk. I, Ft 1, prop. vR(p. 97 of die 1931 reprint of me 4ed.). The first brightness curve was

who translated Hess’ cm. into visual
angles. For E. Hegg, see his La

plotted by J. Fraunhofer, Bestimmung des Brechungs- und Farben-

pdiimdttie des cauleurs, Ann. oculist.

zerstreuungs-VennBgeos

Foris, 109, 1893, 321-^8. Here also

ner Glasarten, in Bezug auf die Vet-

colords,

Ann.

110,

1893, 169-181; PMmdtria, 1895, I-

Berlin, 35 ( 4), 1889, 1-62. The fig-

verschlede-NOTES
volUconimung acliromatlscher FernrShre,

Dmhchr, Acad. WUi. Mdn-

chen, math.-natunvias, Cl., 5, 1815,
193-226. esp, 210-216 and Plata II.

195
sensitivity

differential

of

the

eye

would affect the perception of spectroscopic lines In the ^ectrogiams ofstars; Ueber den Einfluss der Schwel-

The original reference to Ihe Pur-lenwerthe der Lichtempfindung auf

kmje phenomenon is J. E. Pnrlcinje,

den Charakter der Spectra, tbid., 269,

Beitrdge zm Kenntnlss desSehens in subjecUver Hinsicht, 1825,

1888, 138-158.

Neue

108-110 (to be found also in Purhinje’s Omnia Opera, 1918 ) The men
who first conhrmed tliis observation
were A. Seebeck, Ueher den bei
manchen Personen verkommenden
Mangel an Faibensinn, Ann. Phys.
Chem., 118, 1837, 177-233, esp.
222 f. (incidental reference); H. W.
Dove, Ueber den Einduss der Helligkeit einet weissen Beleuchtung auf.

die relative Intensltht verschiedener
ibid., 101, 1852, 397-408(more than inmdental, but not quan-

Farben,titative);

J.

TheoriederSifzungsber.

GraUich,Bcitragzur

gemischten Farben,
Akad. Wias. Wien,

math.- naturwiss. Cl., 13, 1854, 201-284 (incidental); H. Aubert, Physiologic der Hetzliaut, 1865, 126-129(rather incidental).

The second determination of tlie
form of the brightness curve was byK.
Vierordl,
Beschreibung elner
pbotometrischen Methode zur Messung und Vergleichung der Starke
der farbigen Liohtes, Ann. Phus.
Chem., 213, 1889, 200-222; and thethird was by W. Dobrowolsky, Ueber
die Empfindlichkeit des Auges geg-

A. KSnig’s classical paper is Ueber
den Helligkeitswerth der Speotralfarben bei verschiedener absoluter
Intensitht Beitriige zur Psychologfe

andPhysiologiederSinnesorgane(Helmholtz Festschrift), 1891, 309338,

reprinted in his

Abhandlmeen

sear

Gesommelte

physiologischen

Optik, 1903, 144-213.
For a discussion of the duplicity
theories of M. Schultzo, H. Parinaudand ]. von Kries, see Nagel, loc. eft.,and J. H. Parsons, An Introduction to

the Study of Colour Vision, 2 ed.,1924, 206 f. Von Kries’s original
aper on his theory is Ueber den EinusB der Adaptation auf Licht- undFarbenempfindung und uber die
Funktion der StSbehen, Ber. naturf,
Ges. Freiburg i. B., 9, 1894, 61-70,
but a more accessible account is
Ueber die Funkdon der Netzhautstdbehen, Z. Psychol., 9, 1890, 81123,

For representative papers

in thecontroversy as to whether the Purklnje phenomenon occurs in the fovea,

en die Lichtintensitht versrmiedener

see W. Koster, Untersuchimgen zur
Lehre vom Farbensiim, Aren. Ophthd. Berlin, 41 (4), 1895, 1-20, andF. D. Sherman, Ueber das Purldnje’-

SpectraKarben, Arch. Ophthal. Ber-sche

18 (1), 1872, 74-92.
S. P. Langley's measurement of
the distribution of energy in the solar

Netzhaut, Phil. Stud., 13, 1898, 434479, who find the phenomenon in the

spectrum was reported by him as The

Mittheilungen fiber die funotionelle

selective absorption of solar energy,

Sonderstellung

Amer. J. Sci,, 3 ser., 25, 1883, 169-

irums, Z. Psy^ol., 23, 1900, 161-186,

196. His determination of the luminos-lin,Phhnomen Im Centrum der

fovea; von Kries and Nagel, WeiteredesNetzhautcen-

3 ser., 36, 1888, 359-379. F.

esp. 173-177, who are on the otherside and who say why; and L. T.
Troland, The absence of the Purkinje

Strenger's paper is Zur Lichtemission

phenomenon in the fovea, I. Franklin

gluhender fester Korper, Ann. Phye.
Chem., 288, 1887, 271-275. There

ally supposed te have settled the issue

fty curve is in his Energy and vision,ibid.,

was at this time also a study by H.
Ebert showing that the chromaticIrut,, 182,

1916, 111 f., who is gener-in favor of

von Ilkies and Nagel.

On E. Hering’s position that dark-

VISUAL PHENOMENA

196
adaptation

the condition of

is

tlie

Blindness, 1925, 3-30. There is con-infoimntion

Furidnje phenomenon, see Ills Ueber
das sogenanote Purldnje’sche Phiino-siderablemen, Arch. ges. Fhysioh. 60, 1805,
519-545. On H. Paiinaud’s similar

Colour Vision, 2 ed., 1924, 170-202.
V. P. Scheidt, Revision and Fm therview, see Parsons, he. cit.i also Fari-

Application of the Hek Test for Cohr

naud.

La

de

sensihilite

amc

I’oeilcouleurs spectrales, Ren. sci. Park, 4set., 3, 1895, 700-714, For the early

work on the nature of the absorptb.i
of light by the visual purple, theW. Kiihne, W. Trendelen-studiesherg anti others, see Nagel in Helmholtz's Physichgiad Optics, Engtrans., II, 51-56. The recent authoritative work is S, PIccht and R. E.
Williams, The visibility of monoohtomatie radiation and the absorption

spectrum of visual purple,
PhysicL,

5,

gen.

J.

1922, 1-33, q.v. for die

history and bibliography or Oils topic,

historicalin

Faisons, Introduction to the Study ofBlindness,summarizes

1936, 3-20,

all the other summaries. I. A.

Ilaupt,Tests for color-blindness: a survey ofthe hteratme with bibliography to1028, 1, gen. Psychol, 3, 1930, 222-

265, has some historical value.

For bibliography, besides Konig’s
1205 references in Helmholtz, Handbuch der physiohgisehen Optik, 2ed., 1896, mere are the 335 titles in
Haupt, loc. oit. Fat general information, seeParsons and Collins, tmp.

also

W. deW. Abney, Colour

citt.;

1895, about half of which
treats of color blindness. All these

Vision,ity oiirvea (p. 16), and for the dosebooks make it clear how cbscly tbo
problems of color blindness have been

rdation of the sootopio visibility curve

related to retinal theory.

for the photopio and sootopic visibil-

to theabsorption curve forvisualFor the two early iiislaiiocs citedin tlie text, see D. Turborvlle, Several

purole (up, 24-30).

andremarkable cases in physlck, relating

1 ed.,

chiefly to the eyes, PIms. Trans,, 14,

For die I.E.S, oflloiallyadopted mean normal photopic visibility coefficients, see P. G. Nutting
1919 rqiort of the Standard Committee on Visual Sensitometry, J. apt.

1684, 738; J. Huddart, An accountof persons who could not distinguishSac. Amer,, 4, 1920, 55-79, esp.

the vision of coloius,

For

die

use

photopiaofscotopia, sec Parsons, op.

1916,

60.

olt.,

17.

^

For the general picture of mod-em standardization in this field, seecolours, ibid., 67 ( 1), 1777, 260-265.

For the classical paper, see J. Dalton, Extraordinary facts relating tophil Soc., 5, Pt.

Mm, Manohr.

1798 [paper
read Oct. 31, 1794], 28-45. Dalton
lit.

1,

For

(1766-1844) had just been elected

Instance, they show, aupe^osed, theto the Manchester Literary and Phil-

visibility curves of 125 persons, indi-osophical Society, of which

cating Ue agreement in this function

later secretary and then ( 1817-1844)(Fig. 13, facing p, 206).

president, and to which he eventually

Coblentz and Emerson, op.

cit.

On the minimal sensitivity of theretina,see

Langley,

ho.

ait.;

S.

Heoht, S. Shlaer and M. H. Firenne,

Energy at the threshold ofvision.

Science, 93, 1941, 585-587, who citeother rderences.

Color Blindness

oontributed,

all

told,

be was

116 memoirs.

The story about his gown is that whenon him ihe Docand its scarlet
gown, he, a Quaker, wore the robe
for several days because he liked it,
not realizing that it was gay and conspicuous. George Wilson (op. oit,
Oicford conferred

torate of Civil Laws

infra, p.

6) says that Pierre Prdvost

There is a very good account of

first used the term Daltonism in 1827.

the history of the psychology of color

Seebeck's paper has been cited inblindnessin

M.

Collins,

Colour-the notes to the last section. It

isNOTES

197

Vppsdafonnally divided between thetwoi^es of color blindness; one half ofhet,

ibe paper describes the first, the otherhis instructions and a full discussion

half the second.

of the test, see E.

John F. W. Herschel, son of
Sir William Herschel (both Herschelswere astronomers), made his remarks
on color blindness in his article on
Light, Encuchpaedia Metropolitana,4, 1845, 434 f,
George Wilson's book is Researches
on Colour-Blindness^ 1855, a very in-

Blindness,

Sir

FSrh.,

LSkfdren.

13,

1878, 193-226, For an Eng. trans. offirst

J. Jeffries,

1879, 201-219.

Color-For thepseudo-isochrematio test, see J.

Stilling, Ueber das Sehen der Earben-

blinden mit Tafeln, 1880, 2 ed., 1883.

Lord Rayleigh’s equation is to befound in his Experiments on Colour,
Nature, 25, 1881, 64-66. On othermatters concerned with the tests, seeformative text, exhibiting knowledge

Ilaupt, op. Nt.

and belief in the period when theHelmholtz theory had just been publi-

in these notes the contributions to

C. Maxwell’s letter to WilJ.

diis problem of Konig, von Kries andson is entitled On the theory of col-Nagel. The extent of Konig’s work ap-

ours in relation to colour-blindness,pears

and was printed by Wilson, pp. 153159. It was reprinted in Trans, toy.
Scot. Soc, Arts, 4, 1856, 394-400; andItmgen aur physlologlschen Optik,
1903. There are really two important

reprinted again in Scientific Papers of

Kdnig and C. Dieterici: Die Grund-

James CUtk Maxwell, 1860, I, 119-

empmrdungen und ihre Intensltiitsvertheilung im Spectrum, Sitzungsher. preuas. Akad. Wiss., 1888, 8l5829 (reprinted in Ges, Abhandl, 6087); Die Grundempfindungen in
normalen und anomalen Farbensystemen und ihre Intensithtsver-

cized.

125.

W. Pale’s original description of
On oolour-btindness,

his own defect isPfoc. rou, Soc., 8, 1856, 172-177;
reminted in Phil. Mog., 4 ser., 13,
1857, 282-286. His firial summary

and argument is On die present stateof knowledge and opinion in regard
to colour-blindness, Trans, roy. Soc.

On A. von Hippel's monocular case,
Ein Fall vongenitalereinseitiger,

con-

Koth-Griinblindheitbeinormalen Faibensinn des anderen
Auges, Arch. OphthaL Berlin, 28 (2),1880, 176-186.
F. Holmgren developed his thought

about testing gradually, beginning
in

1871,

impossible to cite adequately

in

his

Qesammelte Abhand-

papers on dichromado vision by A.

Mung im Spektrum, Z. Psychol, 4,1892, 241-347 (reprinted In Oes.
Abhandl., 214-321). Then see J. v.
Kries and W. Nagel, Ueber den Ein-

Edinb., 37, 1893, 441-480.
see

It is

The rqiresentative article

establishing his test seems to be

Om

Quss von Lichtstarketion

und Adapta-

auf das Sehen des Dichromaten(Griinblinden), ibid,, 12, 1896, 1-38;

vonElies,

Ueber

Farbensysteme,

1897, 241-324.
Two recent articles implying that

ibid., 13,color blindness
affairis

not an all-or-none

but that dichromatic vision is

the limit of normal variation ofchromatic vision, are;

S.

tri-

P. Hayes,den medfodda fargblindhetens diag-

The color sensations of the partiallynostik och teori, Nord, med. Ark,, 6,

color-blind,a criticism of current

which estab-teadring, Amer, J, Psychol., 22, 1911,

lishes a date,but a fuller discussion

369-407; S. W. Terman, A new classi-

occurs in his

Om nagra nyare peak-

1874,

24-28,[n.v,],

tiska metoder att

upp&ka fargblind-fication of the red-green color-blind,
ibid.. 41.

1929, 237-251,

Chapter 6

COLOR THEORYW

1have abeady seen in Chapter 3 how the problem ofcolor theory arose. It is hard to say what ttie original

theory of color must have been. The view that, in per-ception, the mind correctly represents the characteristics of an

external object to itself—such a view includes a theory of color.

Epicures’ belief that fine images of objects, exact replicas of theperceived bodies, are discharged from the surfaces of the bodies
to reach the soul by way of ihe organs of sense—that is an evenbetter theory of color because it tells why the pci'ception is correct,

and the nature of the dependence of die perception upon

the stimulus. What has been called ‘theory’ in connection withcolor is always an assertion, generally somewhat speculative, aborrt

the nature of the processes that are intermediate

between thestimulus, on the one hand, and the sensation or the brain, on theother.

John Locke’s doctrine of the secondary qualities was an

assertion that the properties of the perception do not always re-semble the properties of the stimulus; so it was a sensory theory.

The doctrine of the specific energies of nerves was a similar sensory
theory, because it asserted that all qualities are secondary, thatone perceives, not the objects themselves (or images emanatingfrom them) but the states of the nerves that have been affectedby them.
The first coneot ffieory of color, as we have seen, was Newton’s.
He was concerned vrith the nature of light, the process between
the object and fire eye. White and purple, he showed, are always

complex lights; the spectral hues may be either complex or simple;

and all colors are indeterminate as to constitution, for everycolor may be compounded in a variety of ways. Newton’s conception of the process beyond the eye was naive. He supposed thatthe vibration rates of the seven primary colors are transmitted by
the optic nerve to die sensorium, (See pp. 110 f.)

After Newton there was a question as to the place of the ‘seaf
I9S

YOUNG-HELMHOLTZ THEORY

109

of vision in the eye, as to whether it was the “crystalline* (thelens), the "choroid” (coat of the eye), or the retina. By the timeof Thomas Young, opinion had pretty well settled upon the retina
as the percipient organ, that is to say, the crucial point at which

the perceptual process ceases to be light and becomes nervous.

We have also seen that Thomas Young (1801) realized the necessity for a retinal theory of color, and in making his three-fiber

hypothesis anticipated the theory of specific nerve energies. Know-ing that there is an infinitude of simple colors in the spectrum, he

did not see how the ftequend^ of all could be taken up at aand transmitted along a single fiber.
Thus he took advantage of Newton’s principles of color mixture
single point in the retina

to suppose that there might be only three kinds of fibers,

each

selectively activated by different wave-lengths of light. This viewof his was an attempt to explain color perception by retinal events.

Until Helmholtz publicized it in 1852, however, it attracted scantattention; thereafter it was to seem more important, inasmuch as,

coming after Johannes Muller s doctrine of specific nerve energies,
itappeared as an application of that dogma. (See pp. 70, 110-112 .)

As we have also seen, Goethe, Schopenhauer, and Szokalsky
had theories of color in the first half of the nineteenth century,
but there was no real progress until after I860,

The Young-Helmholtz Theory
Of Thomas Young’s theory of color Maxwell said: "It seems almost a truism to say that cobur is a sensation; and yet Young, byhonestly recognizing this elementary Truth established the firstconsistent theory of colour. So far as I know, Thomas Young was

the first who, starting from the well-known fact that there areduee primary colours, sought for the explanation of ihis fact, notin the nature of light, but in the constitution of man.” Newton’s
critics, noting that the sensation white is achromatic, had not beenable to see how white light can be a mixture of colored lights. For

the same reason it was easy to suppose that, if all the colors can bemade by mixing three, there must be only three kinds of physicallight. Even Sir David Brewster as late as 1848 coniinued to makethis mistake. In fact, Thomas Young’s theory had to be rediscov-ered by Helmholtz, so little was it known. In advocating the un-

COLOR THEORY

200

duktoiy theory of light Young had been opposing tlie Newtonians

and their corpuscular theory. This happy heresy of Young’s met
with so great opposition, however, that his color theory has been
said to have been obscured by tire general suspicion aroused byhis theory of the nature of light.

The revival of Young’s theory, as we have seen, occurred inconnection with the experiments on color mixture by Helmholtz

and Maxwell. (See pp. 140-144.) Although Helmholtz’s experi-

Fib. 24.

ExcrranoN Craivis or the Yoouo-IlELMiioLra Tuboiiy {i860)

Approximate ootutruction by Helmhollz.

1= the same for
3 = the same for the "violet-sensitlvo
for the "red-sensitive 8bcra.” 2= distribution of excitationtlie“green-sensitive libers.’’

fibers.”mental study of complementaries in 1852 is the first date for his
espousal of the theory, the event was marred by Helmholtz’s failure
to find that he could get white from more than one binary com-bination.

Grassmann ien pointed out the faulty logic of Helm-holtz’s first conclusion, and Helmholtz, with an improved experi-ment, rectified his position in 1855. In this year, too. Maxwell
supported Young’s fiieory in the report of bis experiments uponcolor mixing. Ultimately, Helmholtz propounded the theory for-mally and effectively in the section of his Fl^siolo^che Opiik
that came out in 1860.

Newton’s laws required ftat any color can be matched by aproper mixture of three properly chosen primaries. Young seemedto think it an obvious consequence of the laws that all color sensa-

tions could be got from three physiological processes in the retina.

Actualy, however, there is an important step that has to be taken

YOUNG-HELMHOLTZ THEORY

201

between Newton’s laws and Young’s theory. If there were merely
three kinds of nerve fibers in the retina, stimulated respectively

by R, G and V light, then there would be no reason why orange
should ever be seen. One has to assume that all light affects all theprocesses, but in unequal degree. It

Mows then that the physicalprimaries cannot have simple physiological effects; R light excites
the R,

G and V processes, and G light too excites all three procV light. Thus one has to assume excitation curves

esses, and so does

like those of Fig. 24, whichshow Helmholtz’s tentative sugges-

tion in 1860 as to the form of these functions. The important pointis that, if all thecolors can be matched by mixtures of three sim-ple physical primaries, then these primaries will require not morethan three physiological components in order that all pure lights

may be perceived as different and that the laws of color mixture
may hold, Young merely impUed this step. Maxwell took it explicitly by his calculation in 1855; he computed from his color tri-

angle a set of three excitation curves and later (1860) charted
the two components for a “dichromic” cobr-blind person. 'The

mathematics of this relationship was given explicitly much later(1888) by Konig and Dieterici, whose exposition Helmholtz re-peated in die second edition of
his Optik (1896). (Cf. pp,

A

145-

147.)

To Maxwell and Helmholtz it
was apparent that the pure physiological sensations are stronger

than can be got by a mixture ofphysically pure lights, There areno three spectral colors which by
mixture can match all the othei
spectral cobrs in hue and saturation, fora mixture is usually of

less saturation than

25. CONSTBHOTIDN OF THE
CoiOB Tbiancle; HELMnontz

FiC,(1860)

the spectral

color of the same hue. Thus, in

The

three

sensations

constructing

themixturedia-

grams, it is always necessary toform a hypothetical triangle large

basic

physiological{Gnmdmpfindmgen)

are represented at R,

A and V.

The line of tile specirum is R'. T,
G, C, I, V. Cf. Fig. 15. p. 147.

enough to include the spectrum, as in Helmholtz’s chart of Fig. 25.

Here the spectrum is represented by the line RiYGCWt, but the
diagram is extended to the triangb RAV, The three corners, R, A

COLOR THEORY

202

and V, represent the colors which each of the physiological processes acting alone would give. Although the constiuction is hypothetical, it receives support, as Helmholtz noted, from the factthat spectral colors can become supernormal in saturation if tlie

eye is first fatigued to the complementary hue.
In all this argument theie was never any certainly as to whichcolors should be selected as piimaiira. Young had first chosen a

Fig. 26.

Kxotation Gubves: Konio and Dietebici (J892)

The curves for the three Crmdemjijindungen os coiuputod ior Konig’s
eye.

These data are classicalred, a yellow and a blue,

Modem curves differ from them.
and then later a red, a green and a

violet. In general, it seems best to choose three colors thatform

a triangle (cf. Fig. 25) which extends as little as possible beyond
the spectrum. Young and others after him preferred to choose

two colors at the extremes of the spectrum; otherwise a purple
would have been required, and the excitation curve (cf. Fig. 24)
for it would have had two modes, one at each end of the spectrum.

The Young-Hehnholtz theory, as we saw in the last chapter,
was developed with great elaboration in connection with dichromatic vision. K5nig and others sought to work out the excitation
curves for trichromats (Fig. 26), protanopes and deuteranopes.
(See pp. 187-189.) There was a chance to check the choices ofprimaries here, and KBnig and Dieterid found that color mixtures
for the protanopes resemble closely, but not exactly, the mixtures

for trichromats with the R-component lacking, and that the mix-

DUPLICITY THEORY
hires for deuteranopes resemble closely, but not exactly, the mix-

ture for trichromats with the

G-component lacking. Thus thetheory received at this stage a general, but not a precise, corroboration. Meanwhile the Hering theory was gaining attention for cer-tain facts

which lay outside the scope of the Young-Helmholtz

theory but which had eventually to be brought within the general
theory of color. In 1881, for example, Bonders published a significant paper which derived its Importance, partly from the fact thatitverified the color matches for dichromats

and trichromats inthe way that the Young-Helmholtz theory required, and partly

from the fact that it proposed, as we shall see presently, a moregeneral theory which tended to resolve the incompatibilities be-

tween Helmholtz’s and Hering’s views.

The Duplicity Theory
The Duplizitatsiheorie is a term applied by von Kries in 1894
to the theory that twilight vision is a function of the retinal rods

and daylight vision a function of the retinal cones. The theory,
however, took shape gradually before von Kries, and it may properly be regarded as die second advance in the theoiy of retinal
action. The Young-Helmholtz theory was the first.

When, in 1838, Johannes Miiller discussed the functions of theretina, he could appeal only to Treviranus’s elaborate researcheson the anatomy of the eye (1828). Consequently he localized thepercipient function in the “rod-shaped terminations of the nervous
fibers upon the internal surface of the retina,” “a layer of cylinders

arranged closely side by side.” He did not know about rods andcones.

The anatomy of the retina and the relation of the rods andcones to each other were described by H. Muller in 1851, and his
findings incorporated by Kblliker in his Mikroskopische Amtomie
in the following year. Miiller and KdUiker made it dear that then
are two different recipient organs in the retina. Muller also dicovered the visual purple that is associated with the rods. He!
holtz, however, considering theories of vision in 1860, was chi

concerned with Young’s three-component theory an^, for thisson, did not realize the tme significance of the dual structu

the retina.

The first person to attach a proper meaning to the ‘duplir

COLOB THEORY

204

the retina was Max Schultze, who in 1886, in the second volumeof his new journal, the Atchio fik mikroskopiscke Anatomie, published a lengthy study of the

anatomy and pliysiology of the

The date is significant, for the theory which that paper
included would not have been possible except for Aubert’s publi-

retina.

cation of his Physiologie der Netzhnut the year before.-Aubert

had pointed out that both color discrimination and visual acuity
diminish toward the periphery of the retina

(cf.

p.

172).

Schultze now showed that, since the number of cones diminishes
in indirect vision, the rods

predominate greatly at the retina’s

periphery. Hence, by putting two and two together, he concluded
that the cones are the mediators of color vision and the basis of

accurate spatial discrimination. His studies in the comparative

anatomy of the retina led him to observe that the cones are missing
or few in the retinas of animals with nocturnal habits (e.g., bats)and that the tods are few in the retinas of animals witli diurnal
habits ( e.g., lizards ).

From that point, since night vision in man isachromatio, it was a simple step to assign the rods to night visionand the cones to daylight vision. Schultze exaggerated the degree
in which nocturnal animals lack cones, but he was right in general as to the tendency for predominance of rods in nocturnal eyes

and of cones in diurnal eyes. Moreover', because cone vision ismore highly differentiated in respect of chromatic and spatial
discrimination, he concluded that rod vision—he was writing in

the days when the theory of evolution had just become impor-tant—is the more primitive, and that cone vision is a later develop^ment, mediating both light and color sensations. Thus Schultze,^drtes'evidenoe than von Kries had later, espoused the duplicity^theory almost thirty years before von Kries named it.

In 1877 Charpentier, who did not know Schultze’s work, set

up the argument that the variation of vision in different parts of
the retina must indicate 'the existence of two independent visualfunctions.

He thus made out a case for a light sense and a colorsnse, citing the data of Putkinje and Aubert. The light sense hedied “perception lumineuse brute,” Its action, he said, is diffuse,d he called its organs the “photoesthetic elements,” without'nitely identifying them with the rods. The other sense he called’on nette.” It mediated, he held, the perception of both lightcolor

and of accurate spatial discrimination, and he calledvans the “visual elements."

DUPLICITY THEORY

205

Just at this time the visual purple came under investigation. In

1876 Boll found that the visual purple is ‘bleached’ to yellow indaylight, a discovery

which suggested the possibility that theformation of visual pinple is the mechanism of dark-adaptationand that the visual purple accounts for the shift of brightness in
the Putkinje phenomenon (cf. pp. 176-181).

A series of researcheson the action of the visual purple was published by Kiihne in
1877-1878, and thereafter the study of ro^sion was always associated with the facts of dark-adaptation.

Besides Charpentier there was another anticipator of von Kries,

H. Parinaud, who formulated “Ta thteie des deui retines” in 1881.

He also was unaware of the work of Schultze. Studying night
blindness, and finding that it did not diminish foveal sensitivity,

he attributed this deficiency to a defect of the rods and visual
purple. When, on the basis of later experiments (1884), he con-cluded that the fovea is not subject to dark-adaptation, he accounted for this fact by the absence of rods and visual purple in
the fovea. His theory of "the two retinas” was quite explicit: thecones are the organs of spatial vision and color vision, functioning
in daylight; the rods are nocturnal organs which mediate solely thelight sensation and functjofonly when the visual purple is formed

under dark-adaptation.
It was Konig

who supplied the last important fact needed toestablish the function of the visual purple in night vision. In 1894

he published determinations of the absorption coefficients of thevisual purple and the visual yellow, and showed that the bright-

ness shift of the Purkinje phenomenon agrees very closely withwhat should be expected hom this absorption.

Von I;^, bringing all these arguments together in 1894, formulated the duplicity theory that has since received general acceptance. He stressed particularly the implications of tihe facts ofadaptation. Ever since Aubert's pioneer work on adaptation (pp.

160 f.)

ithad been customary to measure the degree of dark-

adaptation by observing the decrease in the size of the thresholdforillumination.

These

results

show

that,

whereas inlight-

adaptation the periphery of the retina is a little less sensitive than
the fovea, in dark-adaptation it is fully a thousand tinges more sensitive. Von Kries held that the rods are primitive receptors, giving

rise only to the light sensationand functioning with great sensi-

tivity in low illumination under the influence of the visual purple.

COLOR THEORY206

The cones, present alone in the fovea and scarce in the periphery,are, von Kries believed, the organs of vision in good illumination,

mediating both the chromatic and achromatic sensations. Because
it assumes that the sensation white is arousedby two very different

processes, one from the rods and one from the cones, von Kries’s

theory has sometimes been called a theory of the “double white.”
Since von Kries also accepted the Young-Helmholtz theory as applying to the cones, it seemed strange at first that wliite should

appear in his theory both as the sole function of the rods and also
as the emergent quality of the simultaneous excitation of the threecolor-processes in the cones. Later theories, like Ladd-Frankhn’s,

which regard the perception of color as a differentiation of themore primitive perception of white, and the cone as evolutionarily
later dian the rod, answered'this objection. At any rate, die objec-

tion was not fatal, for the duplicity theory is the only part of all thetheorizing about retinal function that can today be regarded as afact established beyond the speculative stage.

The Hering Theory
In general the phenomenologists have always agreed that there
are four fundamental colors; red, yellow, green and blue (cf. pp.

126-131), although Brentano questioned the simplicity of green(cf. p.

131), and sometimes it has seemed that orange and pur-ple, which have special names, must have a different status fromyellow-green and green-blue. Leonardo da Vinci (ca. 1519) held
for the four principal colors.

Goethe (1810) kept to the same

basic principle. Mach affirmed the same fact later. The four-hue

theory of color is pretty obvious to phenomenological observation,

but the phenomenological mixtures do not agree with the physicalmixtures. For all that a pure’ red stimulus mixed with a ‘pure’ green

stimulus gives a yellow, no one ever thought that yellow looks as if
itwere reddish green. The Young-Helmholtz theory, based upon

the facts of color mixture, thus missed these important phenomenological facts.

Ernst Mach pointed out the difficulty in 1865. He laid down

the general principle of psychophysical parallelism. “Jedem Psychischen entsprioht ein Physisches, und umgekehrt. Gleichen

psychischen Processen entsprechen gleiche physische, ungleichen
tmgleiche.” Some people, he said

—and he may have been Slinking

TETEACHHOMATIC THEORIES

207

of Helmholtz’s explaining of color contrast as an illusion of judg-

ment-dismiss psychic facts as illusions; nevertheless, even an
illusion is lawful and should have its principle determined. Since it
is clear that red, yellow, green

and blue are four basic colors, there

must be something fundamental in die physiological processes toaccount for their peculiar status. There must also be somethingphysiologically unique for black and white, since they are unique
as experiences. As

no one questioned psychophysical parallelism

in those days, this logic of Mach's was convincing; it influenced

even Hering in the formulation of his theory.

A similar objection to the Young-Helmholtz theory was expressed in the same year ( 1865) by Aubert, who brought together

numerous cases where the matches of color mixture difier fromphenomenological expectation. The most obvious instance is that‘pure’ red and ‘pure’ green, when mixed, give yellow, an nnsat-

uratod yellow, but nevertheless a ‘pure’ yellow,

if

the red andgreen are in die right proportions. The Young-Helmholtz theory

depends on the principle that H

G = Y, and that R-j-G-{-V = W, if R, G, and V correspond to the elementary physiologicalprocesses. Aubert also brought out other cases, like Y -j- Bfc= G,

an instance of what was later called the Bezold-Briiclce phenom-

enon (cf. 132). All these oases go to show that the psychologicaland physical components of colors do not agree, that thestimulus-components may be other than what one could expectfrom the direct observation of the color, and that we must, therefore, as Mach also was saying, admit the importance of phenom-

enological fact. Aubert

ended by adopting the term principal

color (Hauptfarbe) for black, white, red, yellow, green and blue.

Somewhat later it came to be said that the Young-Helmholtz
Y, andtheory depends upon an “additive principle.’’ If fl -|-G=

Y is not merely a reddish green, then Y is an emergent from theaddition of H and G. Similarly, in holding that R -|- G -[- V *= W,
the theory assumes that white emerges from a combination of all

three components. It was precisely &is difficulty of accepting thefact of emergence that had led in the 1670’s to the opposition to

Newton’s analysis of white light into colors. In a way Hering was
attempting a Hegelian synthesis of the controversy between Newton and his critics, for he was showing that, although Newton wasright, his critics were also right, were insisting, indeed, on a factthat required explanation.

COLOR THEORY

208

Hering promulgated his theory in 1874. Showing that all thecolors can be regarded as intermediates between red, yellow, green,

blue, blade and white, he described the "natural system of color
sensations.” In this system, he pointed out, yellow and blue areopposites (Gegenfarben)', there can be no yellowish blue. Similarly in opposition are red and green. Such a four-color theory de-scends from Leonardo da Vinci and Goetlie. At first Hering heldthat every simple color has a simple opposite, every mixed color amixed opposite; but he had later to abandon this view in the faceof the fact that pure red and pure green are not complementary,and that the red and green which do not change hue in indirect vision are both bluish (cf. p. 143). Thus, he concluded, the funda-

mental colors are yellow and blue, because one half of the spec-

trum is yellowish and the other half is bluish. The critical pointthat divides the two halves is pure green, and pure red does notoccur in the spectrum, Red and green, he though are therefore alater development, as the facts of color blindness sliow (pp. 185-

189).

To account for this natural system of colors, Heitig supposed
the existence of three visual substances in the retina, each capablechange in either of twoof undergoing metabolic or chemical

antagonisbe directions. These opposing changes he called assimiiation and dissimilation. The substances were named for thecomponents to which their processes give risci the ‘black-white’substance, the ‘blue-yeUow’ substance, the ‘green-red’ substance.

How the pure colors were regarded as dependent upon these six
different processes is shown in the following table.

White-black

Ydlow-blue

Red-green

substance

substance

substance

Dissimilation

White

Assimilataon

Black

Yellow
Blue

Green

Red

All colors other than these six are mixed colors, dependent upon

the excitation of more than one process. No one color process, asa matter of fact, is ever excited alone, for all Hght affects the white-black substance. This ffieory was greatly strengthened by the
final decision that all partial color-blindness, whether of the deu-

teranopic or .the protanopic type is red-green blindness. Hering ar-

gued further that the facts of indirect vision lend the theory similar—that the middle retinal zone

supportis red-green

blind, lacking

the red-green substance, and tihat the peripheral zone is totally

HERING THEORY
color blind, lacking both die red-green and tbe yellow-blue substances. This contention was not, however, univocally established.

One great difficulty in the Hering theory is its requirement ofdifferent assumptions for the action of the white-black substanceand for the action of the other two substances. An intermediate

hue depends upon the ratio of the two processes combining in it.
Violet, for instance, depends for its exact hue upon the ratio of thedissimilative process in the red-green substance to the assimilative

process in the yellow-blue substance. Since assimilation and dissimilation are mutually exclusive in the red-green substance andthe yellow-blue substance, in any one substance there is simply
less or more of either process. Ilering had to

imagine, however,that in the white-black substance both processes may go on togelher, as

istrue of many antagonistic processes in reversible

chemical reactions. The brightness of a gray, he asserted, must de-pend upon the ratio of assimilation in the white-black substanceto the total of assimilation and dissimilation taken together;the brightness equals A/(A -|- D) or

i.e.,

W/(W+ Bfc). Thus ‘middle

gray’ is experienced when assimilation and dissimilation equal eachother in die white-black substance. This point is very important,for, if assimilationand dissimilation were mutually exclusive inthe white-black substance, as they were said to be in the odier two
substances, then, instead of middle gray at the point of equilibrium
for all three substances, one should see nothing at

aU—as he seeswith the hack of his head.
This necessary difficulty in the theory led Hering to develop asomewhat elaborate theory of color “valences.” A light orange
would have a red valence, a yellow valence, a white valence ( since
it isli^t), and also a black valence (since aR Ught arouses bothprocesses in the black- white substances) Later Hering had to ex.

plain the facts of color mixtures by assuming, in addition, the existence of a “specific brightness” for the colors, such that a whitevalence is added to mixtures for red and yellow and a black valence for green and blue. These valences represented for him theexperiential potentialities of the excitation. Their historical im-

portance, however, is negative! other theories came into existencein order to avoid hypotheses of such dubious value.

COLOR THEORY

210

Modifications of the Fundamental Theories

The end of the last century was a period when psycliologisls
found it easy to manufacture speculative physiological tlieories.

An important psychologist was expected to espouse some Uieoryof important phenomena, and generally—aided by this social pres-sure and by the closeness at that time of the new experimental

psychology to the speculative freedom of philosophy— each man
modified existing theories to form his own. Thus, after Helmholtz

and Bering, there were theories of color vision associated witheach of the following important names; Wundt (1880), Bonders(1881), Edridge-Green (1891), Ladd-Franklin (1892), Ebbing-haus (1893), Kbnig (1894), G. E. Muller (1896), McDougall(1901), Schenck (1907), The details of these theories, many ofthem, were mere guesses or suggestions as to how certain special
facts could be accounted for if the retina were fous and so. Be-

cause they were not steps toward any view finally validated orrendered plausible, they have little historical importance. On theother hand, these theories did yield two important advances; theybrought out a conception of the evolution of the color sense andthey demonstrated the need for including ilie brain along with theretina in a theory of color.

EwliMon of Color.

—Sohultze (1866) had supposed the rods

to be more primitive organs than the cones, achromatic twili^tvision to be more primitive than cb’omatio daylight vision. Von

Kries (1894) established this view. Most of the intervening discussion of rod vision and cone vision had implied an evolutionary
distinction between them.

Heting’s supposition that the red-green visual substance is laterin development than the yellow-blue was based upon the fact that

red and green may disappear alone in color blindness or indirect
vision, whereas yellow and blue are seldom lacking unless red andgreen are also gone. The impHoation is that the white-black substance is the oldest and most stable, the yellow-blue substancenext, and the red-green substance least. The fact that the spectram
is divided

between yellow and blue—the warm half is yellowish,—seemed to Bering

the cold half is bluishto mean that yellow andblue are raorfe primitive than red and green.
Christine Ladd-Franklin’s theory in 1892 made this evolutionary
relationship focal. She supposed that the primitive sense

is

the

EVOLUTION OF COLOR

211

black-white of achromatic vision, that white vision becomes differentiated into yellow-blue vision, and that yellow vision is still
later differentiated into red-green vision. For some unknown rea-son blue vision has not become further differentiated. The relationship of these colors takes account of the six principal cobrswith whose uniqueness Hering was concerned, as well as the factsof color mixture which were basic to Helmholtz’s theory. Sincepure red and pure green mix to give yellow, they should represent
a differentiation of yellow; and since pure yellow and pure blue

mix to give white, they should represent a differentiation of white.

The diagram of differentiation is this:
Black

Blue
.White--I

Green.Yellow—-^

Red
Mrs. Ladd-Franklin gave this relationship concrete objectivity

by supposing it to represent differentiation in the decompositionof a retinal color molecule. Although Dondeis had anticipated her(

1881 ) in the general assumption that color vision may be ex-plained by reference to the decomposition of a color molecule,whose product of decomposition selectively stimulates the nerves,
itwas Mrs. Ladd-Frankhn who added the evolutionary principle

to Donder's idea. The original undifferentiated molecule, she held,

alone excites the simple sensation black, but white light, by someprinciple of resonance, tears off from the inner core of the mole-cule a white-excitant group of atoms. The residual core becomesinactive and white is seen. This function, which is primitive, is allthat can happen in the rods. In the cones, however, there has beendeveloped a further selectivity, so that the yellow half of the spec-

trum tears off one half of the white-excitant atoms to arouse thesensation yeUow, and the blue end of tlie spectrum tears off theother half to arouse blue. At this stage of evolution there can be
yeUow or blue or the yellow-blue which is white. The next stage ofdevelopment would have to be the differentiation of yeUow into
red and green, in the way that white became capable of differentiation into yellow and blue. Thus the theorym^es red, green andblue the three ultimates, with a chemical decomposition-product

They are, moreover, what Mrs. Ladd-Franklin caUed
G Y be a simple
be a simple color.
G) -f Bcobr, and that (flfor each.

,

simple colors. The theory requires that fl -f=Y B=W=

COLOR THEORY212
All other colors, likeR + B= Purple, are complex. Certainly thehypostasizing of these relationships as concrete relations between
parts of molecules gives the evolutionaiy principle clarity, al-though there was never enough knowledge of the ciemistry of theretina to justify such assumptions.

Both McDougallin 1901 and Schenek in 1907 sponsored theories
of color vision that included this same evolutionary relationshipamong the principal colors. McDougall’s theory was focused uponsome crucial experiments in visual induction and inhibition which
he argued implied certain relationships in the optic nervous system. Both he and Schenck, moreover, accepted the Young-Helmholtz three-component theory as holding between red, green

and blue in the initial stage of the process of color vision. In fact,
one important function of the evolutionary theory is that it provides a synthesis between the theory of three components and thetheory of four (or six) simple hues.
It may be said, in general, that this evolutionary view has been

accepted. Red and gi'een are paired, as against yellow and blue, inmany phenomena, and they appear to bo less stable in their laws.
Moreover, red and green, representing as they do a finer discrimination of wave-length than do yellow

and blue, might bo

supposed to have been developed later. For a similar reason it isnatural to assume that primitive sight would include only theblack-gray-whites of monoohromatio vision.

Central Factors.

—^When Mach argued for a one-to-ono cor-

respondence between die psychical and the physical and therefore
for six physical terms to account for the six principal colors

—

red,

yellow, green, blue, white and black—it did not seem to occur to

him that the six physical terms might be localized somewhereother than in the retina. In the history of psychology the knowl-edge of perceptual mechanisms has proceeded from without in,from stimulus to sense-organ to narve to brain, and speculation has

been most specific at the frontier between knowledge and ignorance. The theory of specific nerve energies was merely a device to

get the qualities separated among difierent nerve fiberson theassumption that the 'sensorium’ could then discriminate the particular fibers excited. It was not long, however, before the difficulties of color flieory forced

the consideration of processes subse-

quent to the initial retinal events.

Thus Donders in 1881 suggested that the Young-Helmholtz

COLOR PROCESSES IN THE BRAIN

213

theory might hold at the retina and that the other simple colors

might emerge in the brain. Though he accepted the view of the six
principal colors, he thought nevertheless that there might be only

three specific energies in the fibers of die optic nerve; R,

G and B.

Then Y, for instance, would appear in the brain because R and G,
together would excite a third central substance for Y, Similarly
would correspond to a central substance excited by the simultaneous cooperation of all three energies, and Bk would arise cen-Wtrally in the absence of any of the energies. Donders was follow-

ing out Mach’s principle of psychophysical parallelism; for any

simple color there must be a simple substance or process in thebrain. Purple can immediately be seen to be a mixture of red andblue because it depends directly upon these two processes or‘energies.’ Yellow does not appear to be a mixture of red and green,

because another simple process intervenes.

In 1896 G. E. MUller formulated his modification of Hering’s
theory. His most important addition was the concept of corticalgray. Hering, as we have seen, had to complicate his theory inorder to account for the fact that something (gray) is seen when
the R-G, Y-B, and W-Bfc processes are all three in equilibrium.

Though logically one should see nothing, actually one does see
gray. Muller supposed that the brain added to aH vision a con-stant grayupon which aU specific excitation is superposed. In

addition to the needs of theory he had evidence from the grayness of scotomata ( blind spots ) in the retina. He posited further six
central color processes or “valences,” which respond to the retinal

processes in such ways as to account for color mixture and also thespecific brightnesses of the colors.
It was in these papers that Muller laid down his psychophysicalaxioms, setting forth the commonly accepted fundamental relations between psychic events and dieir correlates in the brain, (Wehave already discussed this matter in an earlier chapter; pp. 8390.)

The modern reaction against the speculative theorizing of

the late nineteendi century is due largely to the fact that theseaxioms, so fundamental to the thought of that period, today seem

dubious, especially as applied to the specifications of processes inthe sense-organ. In 1865 (to Mach) and in 1896 (to Muller), however, it seemed convincing to say: If

ydbw does not appear to bea mixture of red and green, then it must depend upon some simple
process in the brain and not immediately upon a mixture of theCOLOR THEORY214

red and green processes. Today, although we still meet the axiomsofMach, Donders, Hering and MiiUer in the isomorphism of

Gestalt psychology, visual theory, resting for the most part in thehands of the physiological psychologists, seems to be more in needof observation

j facts—about the retina and the brain—tlian ofaxioms.

On the other hand, modern psychology has been forced into theacceptance of important central factors in color vision. Chromatic

phenomena often depend upon binocular relations, as, for example, in binocular color mixture; and the excitations from the twoeyes cannot interact at any level lower than the common central

region of proiection. ( On color contrast as a central phenomenon,

seepp.l70f.)

Modern Visual Theory
The first third of the present century differs markedly from thelast third of thenineteenth century inits

altitudetoward ihe

psychophysiology of sensation. Not only has the emphasis upon thephenomenological aspects of vision become less and the conceni
with its physical basis mote, but there is less physiological speculation and more carefully reasoned argument. Psychologists do not

attempt complete theories of vision or of hearing, nor is it any
longer an argument against a theory that it leaves many collateralphenomena unexplained. Instead ihe theorists are concerned tobring out by experiments various properties of visual phenomena
until an implication as to corresponding properties of retinal processes becomes apparent.

The discovery of the all-or-none principle of nervous conduction(pp. 59-68) radically altered visual theory. Whereas, in thenineteenth century, it had been taken for granted that nerve fiber

can be excited in varying degrees, there existed now a definite

problem about sensory intensity. In a single fiber excitation cannot
vary in amount. To meet this difficulty Forbes and Gregg invented
tire frequency theory in 1915,

a theory which Adrian and his as-sociates amply verified in 1926

and immediately thereafter. The

fact that the apparent magnitude of stars increases with intensity

showed, moiMver, that brightness may depend upon the numberof fibers excited; yet the situation offered no easy solution for thetheorists, who already needed three independent sets of nerves for

HECHT’S THEORY OF VISION215

the three color processes. Troland, nevertheless, in 1920 made it
clear that the all-or-none law is not necessarily incompatihle withthe facts of visual perception, suggesting a plausible synthesis,

which has not, however, been substantiated.

The only thorough endeavor to establish a theory of retinal excitation consistent withmodem knowledge of neural action is thatof Ilecht, which depends upon a series of researches beginning in

1919 and summarized once by flecht in 1929 and then again later.
It is not possible to state Heoht’s analysis of the photochemistry of

the retina briefly, but the nature of his argument can be exhibited.

Hecht began with the Bunsen-Roscoc law of photochemical re-==

U=C, where 1 intensity, t time, and C is a constant.
The law states that a photochemical reaction depends upon theaction,total energy and not upon intensity or time alone, for the reactionisconstant if 1 and t vary inversely. That this law holds for tho

retina appears at

first

to be contradictedby the fact of thethreshold, since a low intensity may never be sensed, no matter

how long it persists. Hecht drew from this fact the inference
that the product of the initial reaction must in some way be dissipated, so that, below the thieshold, dissipation prevents the ac-

cumulation of enough of the product to excite die nerve fibers.
Tlie retina does not, however, remain permanently exhausted after
stimulation; it recovers in time, and the rate of recovery should be

proportional to the amount of the product of the original decomposition. Hecht suggested formulae for each of these two opposing

reactions—^the decomposition under the action of the stimulus, andthe recomposition under the accumulation of the products of decomposition. It is the sum of the two processes, and that(

It—C

The Bunsen-Roscoe law ) , when the time is very short, is just what

experiment shows.

Hecht summarized his theory in the following diagram:

The diagram is read as follows. Light, as stimulus, acts upon theretinal photosensitive substance, S, which is thus decomposed into

COLOR THEORY

216

two decomposition products, P and A, and possibly a third residue,
B, which is ultimately dissipated. The cessation of the light, that is
to say, the ‘dark,’ acts to recompose S out of P and A, and perhaps

some otiier agent, C, supplied by the retina to induce the recom'
A now acts as a catalyzer by which another retinal
position, P
substance, L, is transformed into T, which acts upon the nene
fiber, exciting the neural impulse. This theory is speculative, but it

must be noted that Hecht has checked some of its assumptions
against certain measurements of dark-adaptation, light-adaptation,
acuity and sensitivity.

Hecht has also extended his theory to include color vision at thelevel at which the Young-Helmholtz theory accounts for color mixture. He has explained the increase of visual acuity with intensityof illumination by reference to a population theory of the retinafire

theory that the rods and cones constitute a population ofvaried thresholds, and that at greater intensities of the stimulus

more receptors are put into function, with the result tliat a mosaic
of more numerous points is excited in the retina and the excitatory
pattern becomes capable of finer spatial differentiation.

One ofHecht’s calculations computes, from the data for the dependenceof acuity on illumination, the result that a given retinal area should

contain 542 cones, whereas anatomical data indicate that the num-

ber should be 540. Such remarkably close agreement has helped togain acceptance for the theory, at least for the time being.

Notes
la general od theories of vision before 1850 see Chapter 3. An excellent

discussionof nineofthe theories

1911), 455-468 (Ladd-FrankUn’s
account of her theory in relation toothers). Helmholtz’s

own discussion(Young-Helmhollz, Hering, Donders,of theories is fuller in idem, 2

Ladd-Fianlclln, McDougaS, Schenck,

1898, 340-350, 876-384. For a clear,

Wundt, Muller, Ediidge-Creen) is tobe found in J. H. Parsons, An Intro-

concise, elementary exposition of six

duction to the Study of Colour Vision,M.

2 ed,, 1924, 203-314. This exposition
includes a historical review, pp. 206-

81-58.

214, but the whole account isnistori-

ed.,of the theories mentioned above, see
Collins,

Colour-BUndnm,

1925,

Young-Helmholtz Theory

cally oriented. See also the discussion

H. v.
Fhyslahglad
1924, H, 140155 (HelnJiolbs’s own account of his
theory as of 1860), 426-464 (voninHelmholtz,

Opttos, Eng. trens.,

Kries's account of other theories as of

For Young, see Chapter 3; for the
relation of the theory to cobr mixture,

see Chapter dj for me relation of thetheory to color blindness, see Chapter 5.

NOTES
H.

For

Hdmholtz’a

V.

chief

contributions to the theory, see his

Ueber die Theorie der zusanrniengesetzen Farben, Am. Phys. Chem,,
163, 1853, 45-66 (reprinted in his
WissenschaftUche
Abhandlungen,
1883, II, 1-23 )i Ueber die Zusammengesetzung von Spectralfarben,
ibid., 170, 1855, 1-28 (reprinted in
Wiss. Abhandl.,

buck

der

45-70); Hand-

II,physiologischen

sect. 20, in the 1 ed.,Optik,

1860, reprinted

1911, and the Eng.

in the3trans.,

1934; see also the extended

ed..

discussion in the 2 ed., 1893.
J.

papers, where he develops the excitation

curves from the eelortri-angle of mixtures, are: Experimentson colour, as perceived by the eye,remarkswithoncolour-blindness,

Trans,

ray.

Edinb.,

21

1855,

27^298 (reprint^in

Scientific

Soc,

PapersofJames

by A. Tschermak, Die Hell-Dunkeladaptation des Auges und die Funktion der Stdbehen und Zapfen, Ergehnisse der Physiohgie, I (2), 1902,
694-800, esp. 780-800. It has a classified bibliography of 274 titles. It issignificant that the duplicity theory

should have come to be discussed
under the general head of Adaptation,

when the origin of the theory

had so little to do with adaptation.
The crucial paper on the rods andcones and the visual purple is H.
Muller,Zur

liistologle

der

Netz-

haut, Z. wiss. Zool, 3, 1851, 234-237.

Maxwell’s most Important

C.

2ir

(2),

The
Clerk

was evaluatedand placed in relation to the rest oflire Imowledge of the structure of theretina by the famous histologist, A.
Kolllker, In particular in his Zur
Anatomic und Physiologic der Retina,
Verh. phys.-med. Ges, WUrzburg,
3, 1852, 316-336, and In general in
Muller’s contribution

Mikroskopische

hisAnatomie,

11,

Maxwell, 1890, 1, 126-254); On the1852, Pt. 2. 648-703, esp. 840-662,

theory of compound colours, and the800-703. KBlliker says that the rods

relation of the colours of the spec-

were described by Leewenhoek (oa.
1720) but had to be rediscovered by
Heuschke (1835) and Treviranus

trum, Phil Trans., ISO, 1860, 57-84(reprinted In Sci. Papers of J. C. U.,I,

410-450).
F. A. C. Donders’ paper, support-

ing the Young-Hehnholtz theory but
also adjusting it to makeitcompati-

ble with certain other facts(Me(1835). Ce^inly the distinction between rods and cones was not clear
to Johannes Miiller in 1838 and was
not firmly established before H. Mtiller in 1851.

infra) is Ueber Farbensysteme, Arch.

The paper of Max Schultze's that

Ophthal Berlin, 27 (1), 1881, 155-

fixes the date of his ‘duplicity’ theory

223.

is

The classical paper of A. Kdnig and
C. Dietericl is Die Grundempfindung-en und ihre Intensitatsvertheilung
im Spectrum, Sitzmgsber. preuss.
Akad. Wiss., 1886, 805-829 (reprinted in A. Kbnig’s Gesammelte
Abhandlungen, 1903, 60-87).
Of course the Young-Helmholtz
theorystill

survives in sophisticatedform in modem views, like Hecht’s;

Me

Infra.

Duplicity Theory
The best discussion of the history.and nature of the duplicity theory is

Zur Anatomie und Physioiogie dec

Retina, Arch.

mik. Anat,, 2, 1866,
175-286, esp. 247-261, but Schultze

made his ideas somewhat more explicit in Ueber Sttibchen und Zapfen

dec Retina, ibid.,3,

1867, 215-247,

and Bemerkungen liber Bau und
Entwickdung der Retina, Ibid., 3,
1867, 371-382.
A. ebarpentier first expressed himself

on this matter in De la vision

avec les diverses parties de la retlne,
Arch. Physiol Paris, 2 set., 4, 1877,
894-945. Re held insistently to bis
view in many later short papers up
to 1891; see Tschermak, op. cH., forthem.

COLOR THEORY218

For F. Boll's workand die visual purple, see his Zur
Anatomie und Physiolorie der Retina,
on the retina

Monotsber. preusi. Akad, Wiss., 1870,
783-787; Zur Physiologie des Sehens

uniqueness of the six principal colors:
white, black, red, yellow, green, blue.

In general on the problem of simple
Chapter 4, pp. 127-131.

colors, see

For the two criticisms that immedi-

und Farbenerapnndung, ibid., 1877,

ately antedated Hering’s theory, see

W. Kiihne’s various papers on

the visual purple axe in Vntersuch.

E. Mach, Ueber die Wirkung derrflumlichen Verthoilung des Llcht-'phys. Inst, [leidelberg, 1, 1877-1878,

reizes auf die Netzhaut, Siteungsher.

2-7.

and 2, 1878. See esp. his study with£. Ewald, Untersuchungcn iiher den
Sehpurpur, ibid., 1, 1877-1878, 139218, 248-290, 370-455.

Akad. Wias, Wien, math,-naturwiss.
Cl., 52 (2), 1865, 303-322, esp, 319321; H. Aubert, thyaiohgie derNetehaut, 1865, 177-180, ey. 180,

H. Parinaud first proposed his the-For E. Hering’s account of his own

ory of the two retinas on the basisof his study of night hlindness intheory, see his Zur Lehte com Licht-n

Ij’h4m4rnlopleetfonctions

lesduvisuel, C. R. Acad, Sci. Paris,
1,

2801. For his discussion

dnne,

1878,

(lightsensation),sensation).

70-141, esp.
107-12173-80(color

These papers were orig-

inally published in 1874. After

tliis

99,

Hering published many papers onsuch topics as color blindness and indirect vision, topics which brought
facts to bear upon the question of

He summarizes his
Texistonco de deux

statement of the theory, though more

espAces de sensihfiitA k la lumieie,

in respect of tho light sense than ofof peripheral vs. foveal adaptation,

see hisDe I’intensitd lumineuse descouleurs

spectrales;

I’adaptatlon

view

Sut

in

influencerAtinienne,

1884, 937-939.

ibid.,

de1885, 821-823. For manyreferences to Parinaud, see

the validity of his tlicory. Ills lateremor senso, occurs in his Grund-ibid., 101,

tire

other

zilge der Lehre vom Lichtalnn, 1020,

Tsohermak, op. oit. Parinaud carriedon a controversy with Charpentier
about this matter; he also pointed
out that von Xries did not have prior-This book was published posthumously; its parts were written in

ity in his duplicity theory.

just given appeared in 1905 and 1907.

1-82,

100-115, 273-275, 290-294.

1905-1916.

The first two citations

A. Konig’s Important contribution
to this topic is his Ueber den mensch-

Sehpurpur und seine Bedeutung fur das Sehen, Sitzungaber.

Later Theories

lichenpreuss. Akad. Wiss., 1894, 577-598.
V. Fries established the duplicity
J.
theory briefly in Ueber den Elnflusa

der Adaptation auf Licht- und Farbenempnndune und ilber die Fuoktion

di Stflbrmen, Ber, naturf, Gea.

Freiburg i. B., 9, 1894, 61-70, ahd

Nine of the most important theories of cobr vision are fisted below.
These theories represent modifications and elaborations of the fundamental principles which were, forthe most part, brought out by Helmhollz and Hering.
W. Wundt, GrundzUge der phyaio-

at greater length in Ueber die Funk-logtachen taychohgie, 2 ed., 1880,

don der Netaiautstabohen, Z. Psu-

I,

furtlier partlcidarized in idem, 4 ed.,Herit^g Theory1893 (there were many new theories
of color in that decade), 529-541,
em. 535-538; and continued to 6

The Herlng theory starts from thecriticism

450-460, esp. 455 f.; extended and81-123.

cfiol, 9, 1895,

that theYoung-Helmholtz

theory does not take account of the

ed.,

1910.

Wundt supposedthatwhite and ^ay depend upon theamplitude cu tne li^t waves, andNOTES219
and not the necessary conse-

Aat hue depends pilmarily upon the
wave-length but secondailly upon thetous

nature of the photochemical processes

differentiation.

aroused in the retina a meory of“polyform photochemical processes.”bensehens, Z. Psychol, 5, 1898, 145-—

quences of the line of evolutionary

H. Ebbinghaus, Theorie des Far-

F. C. Donders, Ueber Farbenwsteme, Arch. Ophthal. Berlin, 27(1), 18S1, 155-223. Donders anticipated Ladd-Franldin more than she

238. Ebbinghaus had presented theever admitted.

composition of the visual purple toW.

F.

Blindness

Edridge-Green,

Colour-andColour-PemepUon,
1891, esp. 30-54. The 1909 “edition” of mis booh is really a reprint.

theory briefly at the London International Congress of Psychology in

1892. He assumed two stages of de-account for the perception of Y and
B. Then he hypostasized two otherretinal substances to account forW

R

Hunterian Lecturee on Colour-and Bk.
and G and for
A. Konig, Ueber den menschliohen
Sehpurpur und seine Bedeutung firr

and Colour-Blindness, 1911,
11-23, and Physiobgy of Vision loith

WIss., 1894, 577-598, esp. 589-598;

The theory became more explicit in
his

Visiondas Sehen, SItzungsber. preuss. Akad.

263-273. Edridge-Greenr^rinted in his Gesammelte Abhandlungen zut physiohgfschen OpUk,

made the visual puiple the sole retinal

1003, 338-383, esa. 353-363, Konig'a

perceptual agent. He had little influ-

theory assumes that the function ofSpecial B^ferenee to Colour Blindness, 1920,

ence because be was not known in

die visual purple

Germany when theof gray, of the visual yellow the per-wastheorizingisthe perception

ception of blue, while red, green and

rife.

Eine

yellow dgiBud on the pigment epi-

neue Theoiie det Lichtempflndungen,
Z. Psychol, 4, 1892, 211-221! On
theories of li^t-sensation, Mind, 2

thelium. The cones, he thought, are473-489i and, in general, her book where all her papers
on color are reprinted, Colour andColour Theories, 1929, The student

der Geslcbtsempflndungen, Z.

Christlno

ser.,Ladd-Franklin,

2, 1893,

who wishes to comprehend the fullsignificance of Ladd-Franklin's evo-lutionary theory should perform thefollowing

Gedrmkenexperlment.

Y

not receptors, but condensers.

G. E. Milller, Zur Psychopbysik
Psy-M., 10, 1896, 1-82, 321-413; 14,
1897, 1-76, 181-196. For the psychophysical axioms, see 10, 1-4, 15-20.

For cortical gray, see 10, 30-32,
411 f„ and 14, 40-48 (esp.), 60-64.
For the rest of the theory, see 10,

C, Imagine that 6 has similarly, in the

33S-418.
W. McDougall, Some new observations in sujwort of Thomas Young’s

course of evolution, become diSer-

theoryentiated into two new simple colors,

Mind, 2 ser„ 10. 1901, 52-97, 210-

Q and 8, The color series about the245, 347-382 TTiis account includes

then R-T-G-^-B-S-H.

reports of ezperimenta cracto on vis-

has become diSerentiated into R andcolor circle

The

is

following relations, given theri^t proportions of mixture, are necessary

becauseevolutionary

R-|-G

they

process:

reversethe

Y-|-B=W,= Y, and g-|-S =B.

It

would be possible for Q to turn out
to be the complementary of R, andS the complementary of G, so that
andbut
fl-t-5these relationships would ho fortui-=W

G-fS=W,offight-

andcolour-vision.

ual Induction and inhibition.

Schenck,

F.

TheoriederFat-benempflndnng und Farbenblindheit,
Arch. ges. Physiol, 118, 1907, 129180, esp. 176-180.
theorists were not quite so
widi imaginary physiology as

The
free

these simple ipse dbdts imply. Theta

was a great mass of argument fromexperiment and from less systematicCOLOR THEORY

220
observation.

There

Is

also

running

is hisThe 'all or none’ principle inthrough the history of the theorioa

visual response,

an important thread of theorizing

i, 1920, 180-185, esp, 160-104, 181-

concerning what axioms of psycho-

185.

1.

opt. Sod.

Amer.,ac-

For S. Ilecht’s theory, see his The

cepted a prioti, a subject that became

nature of tire photoreceptor process.

physical

explicit

parallelism

in Fechner

could

be

(1800),

MachIn

HandbookofGeneralExperi-(1865), Donders (1881) and C. E.

mental Fsychologtj, 1934, 704-828,

Muller (1896).

and references tliere cited, including
31 to lilmself. His worlc is part of thelarger movement of general physi-

Modem Theory

ology to apply physical and chemical

On the all-or-none theory of nervous conducdou, see Chap,

2.

L. T.

principles to the reactions of the intact organism, research which has oc-

Tioland’s early recognition of the re-cupied many pages in thelation of this theory to visual theory

Fhysiol, since its beginning in 1918.

J,

gen.

Chapter 7

VISUAL PERCEPTION OF BIDIMENSIONAL SPACET

he history of the psychology of the visual perception of
space introduces philosopHcal considerations in sensory
physiology to an extent not true for the psychology ofcolor. The earliest problem of visual space perception was a simple

one of physiological optics; how do the spatial relations of the external world get represented in the image upon ihe retina so thatthe ‘sensorium’ can perceive them? Only when ibis question had

been answered, could the second problem be faced; how, if theretinal image is bidimensional, do we come to perceive the third

dimension? Do the eyes provide cues other than the fonn of theretinal image for the perception of depth?
It was at this point that philosophy came into psychology by way

of Zant’s doctrine of space as an a prioH intuition. Is visual space
actually native in perception, as Kant had it, or is it generated inexperience, as British empiricists believed? Out of iis problem

arose the longand barren controversy about nativism and em-

piricism. Descartes,
nativists,

Kant and Hering—to span the ages—were

Locke, Lotze and Wundt were empiricists. Wundt, infact, was somuch of an empiricist that be never even admitted that

extensity is a sensory attribute like quality and intensity—for theattributes

were supposed to be innate, not learned. His systememphasized the distinction between the simple, elementary, native

Empfindmg and the complex, meaningful, learned Vorstel-lung, and it described Empjindungen as organized in respect ofspace (cf.Kantl) into VorsteHungen.

Wundt’s distinction has continued, somewhat obscured, into die
present century. Analytic physiological psychology finds the perception of space more complicated than fire perception of color.

In general, it has been content to deal with color_^as dependent
solely upon retinal processes, but for space it has had to add tothe shape of the retinal image such indicators of depth as accom-

modation of the lens and, in binocular vision, the convergence of
281

222

AKEAL VISUAL SPACE PERCEPTION

the eyes. Gestalt psychology, on the other hand, represents a returnto the nativism of Hesring. It notes that extension, shape and even

depth are just as immediate in perception as hue and brightness

and it looks more to the brain (though in that it passes beyond
Bering) than to the retina for its explanatory hypotheses.

The Retinal Image
It is easy enough nowadays to scoff at the Epicurean theory that

objects emit images which are projected into the eye to be per-ceived by the sensorium; yet a more sophisticated theory of vision
requires a greater knowledge of optics than the ancients had.

Though they realized, of course, that the eye is the percipientorgan and that li^t travels in straight lines, they knew nothing
about the formation of images. Alhazen ( d. ca. 1039 A.D. ) had designated the crystalline humor as the sensitive element in the eye

without recognizing that it is a lens, and his view persisted for along time. The camera olwcura—the arrangement by which liglit,
entering a dark room through a very small hole, casts upon ascreen or wall an inverted image of the illuminated field outside—

was known in the sixteenth century. Leonardo da Vinci ( ca. 1519),
for example,

knew it and compared the eye to it. G. B. Porta(1591) later developed this analogy, assuming the crystalline

humor to be the screen upon which the image is cast. Yet Porta,
though he knew about the image-forming power of lenses, did notrecognize the “crystalline” as a lens. F. Maurolycus, however, hadalready (1575) Identified it as such and suggested its function to

It was Johann Kepler, the astronomer, who, in a work on optics

published in 1604, gave the correct view vrith sufficient argument
to establish it with considerable certainty. Noting once more thatthe eye is like a camera obscura, he demonstrated in detail howthat principle works. The surprising thing about a camera obscurais that the imageof the sun, projected Sirou^ a square hole, isnevertheless round, but Kepler was able to show in detail why theimage of a square object projected through a triangular hole issquare and the image of a triangular object through a square holetriangular. Because the eye has a lens, however, it is not, he argued,a simple camera obscura. He showed exactly how the lens must

RETINAL IMAGE

223

fonn an image at the back of the eye, concluding that the retina

must therefore be a sensitive screen upon which the image falls.
Noting further that the image would be blurred except for objects at one particular distance,

he concluded that the eye musthave the capacity of adjusting itself for vision at different distances. Such an adjustment, it seemed to him, would have to takeplace by a variation of the distance of the lens from the retina. He

noted too that the retinal image is inverted, right for left and up
fordown, and went on to pose without solution that problem

which bothered so many after him, as to why we see rightside up

when the image is upside down. This is, to be sure, a pseudoproblem, for ‘up’ and ‘down’ and ‘right’ and ‘left’ have no meaning in

the image except as it is brought into relation with something else,with the object imagined or with the real retina, since the mind
does not see the object. It sees its image; nor does it see the retina

when it sees the image.
That the image on the retina would actually bo visible were
there another eye to see it was Kepler’s belirf. It is said that

Scheiner carried out just such an experiment in 1625. Descartes, at

any rate, made the experiment and described it fully in his Diop-

Hique in 1637. By placing the eye of a bull in a hole in a shutter
after removing the tiiick coats from the back of the eye, he received

the image on a piece of thin paper placed in the position of theretina.

So modem are Descartes’ diagrams of the optics of theformation of the retinal image that it is hard to realize how recent
that knowledge was.

After this for a very long time the retinal image was practically
identified with perception. Euclid in bis geometrical analysis ofvisual perception had, as a matter of fact, equated the apparent
size of an object to the visual angle which it subtends, and now
W. Molyneux (1692) insisted on tile same relationship. He was, inshort, saying that extension in perception corresponds exactly toextension in the retinal image. Berkeley ( 1709 ), on the other hand,

was somewhat more sophisticated. Naming the possible criteria
for the perception of distance, he showed that the perception ofmagnitude in the object would have to depend on a knowledge ofthe distance of the object; but his whole argument was based on
the assumption that the size of the retinal image is immediately ap-

parent to the observer. If the observer knows the size of the image

224

AREAL VISUAL SPACE PERCEPTION

and the distance of the object, Berkeley argued, he can becomeaware of the size of the object.
This view was not greatly altered in Helmholtz’s time, much

more than a oentuiy after, Its exact eonectness was, however, challenged a little later when, toward the end of the nineteentli century, the optical illusions became one of the important centers ofinterest. Yet the illusions for the most part turn out to be exceptions

that prove the rule, for, if illusion were die rule, it would not becalled {llusion. So it happened at the beginning of the present cen-tury that psychologists

stillthought of apparent magnitude asmeasured by visual angle, that is to say, by the size of the retinal
image. Looking upon illusions as interesting exceptions, they suc-ceeded in bringing many directly under the rule by hypotheses that
explained them as alterations in the actual size of the retinal image.

Though later Wertheimer and the Gestalt psychologists attacked
this “constancy hypothesis” of the equivalence

between the per-ceptual and retinal patterns, the fact remains that retinal extension
is stiU regarded as thefundamental factor among those that deter-mine extension in the visual perception. We must return to these
exceptions later.

The problem of the inveision of the retinal image shows a conflict

between two points of view, the old and the new, regarding

perception. Astonishing to modem psychologists is the length oftime it took for the new view to prevail. KeplM ( 1004),

as we haveseen, raised the problem and did not solve it. Molyneux(1691),

however, for all that he was not very sure of himself, already had
the right answer, Berkeley (17(©), with the same right answer,
spoke out with assurance, yet the length of his argument is a measure of how well entrenched he conceded the contraiy view

to be,

Johannes Muller (1826, 1838) repeated the solution even morepositively. Only by the time of Helmholtz(1860) could the newview be taken for granted and the discussion of the pseudoproblem
dismissed. What were the two views?

The older theory of perception regarded the mind (the soul, thesensorium) as a personal entity wifliin die head, shut off fromtheexternal world but seeking information about it and perceiving
therepresentatives (images, copies) of objects that the nerves
bring
to it. This was thecommon-sense theory: a cranial homunculus

able to perceive directly anything that comes withinapprehension. The mind, according to such a view,

range of its

would see theINVERSION OF THE RETINAL IMAGE

225

image on the retina and would see it inverted because it is inverted.
Thus, since the mind does see objects without inversion, there wasa problem.

The newer theory held that the mind knows only what comes to
The mind sees the image, but not on the retina. The

it in sensation.

image in itself is perceived neither as erect nor inverted. If byerect we mean that the tree s branches are near the sky and its
roots at the ground, then the retinal image of a tree is erect whenits

imaged branches are near the imaged sky and its imaged rootsat the imaged ground. To say that the image is inverted would beto know the relation of the retinal image to the actual external object of which it is an image, or to the real sky and the real ground,and this relation of the image to the world which it images has
been known only to natural philosophers who lived after Kepler’stime.

Molyneux said; “Erect and Inserted are only Terms of Relation
to Up and Doom, or Farther from and Nigher to the Centre of the

Earth.

.

.

.

But the Eye or Visive Faculty takes no Notice of theInternal Posture of its own Parts, but uses them as an Instrument
only.” Berkeley made this principle of relativity even more explicit.
The retinal image, he argued, is not in itself inverted, for all highobjects lie in one part of it and all low objects in the opposite partof it It can be considered inverted only when the world of touchisbrought into relation to the world of sight, as when the eyeturns upwards to view objects that have been imaged on the bot-

tom of the retina. Johannes Muller, who cited A. W. Volkmann asagreeing with him, said: “Even if we do see objects reversed, theonly proof we can possibly have of it is that afforded by the lawsof optics; and, if every thing is seen reversed, the relative positionof the objects of course remains unchanged.” He ended by observ-

ing that what is erect at noon is inverted by midni^t because of
the rotation of the earth, and yet we notice no changel So the final
solution of the problem lay in the recognition of the relativity ofspace, but it took a long time for the solution to prevail over the

popular theory of the absolute perceptions of file homunculus
within the head. (Cf. pp. 257 f.)

AREAL VISUAL SPACE PERCEPTION
Singleness of Vision and the Horopter
The solution of the problem of the inverted retinal image wasrelativistic; up in the image is simply that part of the image where

the things that mean up lie (the sky, people’s heads, the branchesof a tree), and the mind does not see the retina in relation to theearth and the sky. There still remained, nevertheless, the question
as to whether the different parts of the retina do not have somefixed and constant characteristic that identifies each, a “local sign”

as it came later to be called. It was the impbcit belief in somesuch absolute characteristic of retinal position thatmade therelativistic solution of the problem of the inverted image so hard toaccept. If the bottom of the retina is labeled as different from thetop, does it not come labeled as the bottom of the retina? or doesitjust have a characteristic label which is later

learned to mean

the top of the seen world? On this question turned a long debate

about nativistio and empiricistic theories of space perception, adebate which we must consider later. Here we are concernedwith the precursors of the local sign.
In this connection we have first to consider the problem of thesingleness of binocular vision. It has always been obvious that, al-though there are two eyes, they seem to give but a single view ofthe external world. If the mind sees retinal images, why docs it

not see both of them? It takes only a little careful observation,

however, to show that not all of the field of vision appears single

when it is viewed with both eyes, and it was only nine years after
Kepler had established the fact of the retinal image tiiat Aguibnius
defined the horopter,

Aguilonius (1613) coined the word horopter to indicate thelocus of all points seen as single in the binocular field of vision. Incorrectly, he thought of the horopter as a plane containing thepoint of fixation. The fact is that the point of fixation, seen single,

moves toward the eyes as they converge upon a nearer object. Thusitseemed to him that it would be objects behind and in front of theplane of fixation that appear double, whereas objects in such aplane would be seen as single. This conception re^ly implies thenotion of corrraponding points on the two retinas. If all objects inthe plane of fixation are seen as single, it must be that the eyes

have been converged so that not only do the images of the fixatedpoint fall upon corresponding pints in the two eyes, but also theSINGLENESS OF VISION

227

paired images from every point in the plane fall upon corresponding points. The images of farther and nearer objects would thenfall

upon other pairs of points, and such images would appear

double, In this manner tiie concept of the horopter makes the prob-

lem of the singleness of binocular vision into a problem of corresponding points.

Because this relationship was not at all clear at first, there were
three different theories of the singleness of binocular vision.

(1) In the first place, there was the projection theory whidi

Kepler ( ISll ) had proposed. The images, he argued, are projected
into external space; corresponding images, being projected to thesame place, cannot appear double since diey are in the same place,

Even Aguilonius looked with favor upon this view, and Porterfield
sponsored it in his Treatise on the Eye in 1759. The theory fails because it does not show why some images are correctly projected
and seen os single, whereas others, incorrectly project^, are seen
as double.

(2) There was also the theory of alternate vision, the suggestion that we see, now with one eye and now with the other, butnever with both at once. This theory gained support from cases ofcross-eyedness and other defects in binocular coordination. It washeld by Porta ( 1593) and certain other writers of the seventeenth

and eighteenth centuries. Like the preceding theory, it is inadequate because it does not explain why there are any double images,
nor why it is always the fixated object that is seen as single.
(3)

The third and correct theory of the singleness of binocularvision is anatomical, taking into account the partial decussation of

the fibers of the optic nerves in the optic chiasma. This view actually goes back to

Galen

(ca.

175 a.d.), who thought that thefibers from the two eyes were connected in the chiasma. Newton(1717) was quite specific, He suggested that the fibers from thelight half of the left eye cross at the chiasma and join the fibers

from the right half of the right eye, oormecting either there or subsequently at the Sensoriura, so that all the fibers from the righthalves of the two retinas go to the right half of the brain; and conversely for the left halves, David Hartley (1749), the physicianphilosopher-associationist, implied thesame relationship among

the optic fibers, except that he entertained the possibility of die

impression in one eye being actually propagated to the other. He

spoke definitely of corresponding points in die two retinas. W. H,

228

AREAL VISUAL SPACE PERCEPTION

V'ollaston. the contemporary of Thomas Young, told in 1824 how,
after excessive exertion, he had twice lost sensitivity of one-half ofthe field of vision, a loss which he ascribed to the distribution of
the optic fibers in the way that Newton had suggested. He argued
then, as we argue now, that blindness of half of the field of visionmust be due to the “semi-decussation” of the optic fibers. Tlrus,Fic.

n HonopTEB-CmCLE: Johannes Mnunn (1826)

A. Only if tlie points t, p and A Ho In a circle mil their images fall on
coirespondmg mints
the two retinas. Corresponding points are p and p',
and p'
r and P, q ana q' hecause r and f' are separaled respectively frommp
by equal angles, and so also for q and q'. 0 and O' are the opbcnl centersof the two eyes. The horopter circle is doited near and through the eyes
where no points can actu^y be seen. For geometrical proof, see text.
B. Three different boiopter-ciicles for three different distances of fixation
at P, Sand T. For the true horopter-line, see Fig. 28.

when Johannes Muller reviewed the theories in 1838, this fact was
already pretty well established, and the general principle has

never been questioned since,

Meanwhile the conceptions of the horopter and of corresponding points had been developing, Aguilonius (1613) had thought,
as we have seen, diat the horopter must be die vertical plane of
fixation, a view that would make thehoropter in the horizontal

plane of the eyes a transverse straight line at the distance of the
fixation point from the eyes. That is not correct. The horopter in

die horizontal plane is a circle that passes through the point of

THE HOROPTER

229

fixation and the optical centers of the two eyes. Although this rela-tioDship was first worked out by Vieth in 1818, general knowledgeof it is due to the exposition of Johannes Muller in 1826, who dis-covered it independently and who advertised the fact so well that
this horopter came to be called “Miiller’s circle,”

Fig. 27 shows the argument of Vieth

geometrical, not physiological.

Fig. 28. CsttmjjsizEO

and Muller, which was

0 and O' are the optical centers ofL

HonoPTEH-LiNB:

Helmholiz and Hehing (1868-1864)
The general horopter Is a curve, symmetrical above and below, that can be plotted in

the surface of a cylinder. The curve is asymptotic to the line

LMN In the front of die cylin-der. The eyes are represented by circles at theBback of the cylinder with their optical centers j

0 and O’. The horopter-line is ABODE.
The invisible portion of the line that passes
through the eyes is dotted, BCD. In a specialat7case this horopter becomes the horizontal
circle,TheCKUJ, and the vertical line, LMN.
CKUJ, is Muller's horopter-circle,circlei see Fig. 27.

iS
the two eyes, which fixate P, forming images at p and p'. Thus p

and p' are corresponding points. It is argued then that other corresponding points, q and q', r and r', would be separated from p

and p' by equal angular distances; that is to say, the angle pOq
equals the angle p'O'q'.

Hence die opposite angles are equals

POQ = PO'Q. But the opposite angles at m are also equal, so thatthe triangles POQ and PO'Q are similar, and the angles OPO' and
OQO' are equal. Hence P and Q must lie on a circle whose chordis00', since all triangles, erected upon a chord of a cirde to apoint on the periphery of the circle, have equal angles at the
periphery. The same argument places
ai'e

R on the cirde, if r and i'corresponding points. Thus theoretically the horopter

isaAREAL VISUAL SPACE PERCEPTION

230
circle,although actually the images of objects neat the eyes andwithin die eyes cannot fall on the retina and the circle is inter-

rupted ( cf. dotted portion ) If the fixation point changes from P to.

S or T ( Fig. 27B ) the horopter changes to a circle of different size.
,

That Miiller’s circle is the horopter only in tlie horizontal planeand for fixation in that plane was soon clear. When the circle is thecorrect form, the horopter also includes the straight vortical linethat runs through the points of fixation; but this is a special andlimiting case, Helmholtz and Hering, working independently andcriticizing

each other in successive papers, concluded in 1862-

1866 that the general case of the horopter is a line, a curve of the
fourth degree representing the intersection of a hyperboloid witha cone. The

curve has the form of the line ABCDE in Fig. 28.

Asymptotic to the vertical line LMN, it is symmetrical above andbelow about its midpoint. In one special case this curve becomesthe circle CKMJ, which is Muller s circle ( Fig. 27) and tire straiglit
line

LMN.

Eye-Movements
Johannes Muller’s monograph of 1826 on eye-movements in relation to human vision was more or less the beginning of a series ofmonographs and articles on the anatomy of the eye with the exact
measurement of its dimensions, the dioptrics of the eye with thedeterminatioiyrf the constants that affect the formation of theretinal image, and movements of the two eyes as they are related

in the convergence of common fixation. In the books of Helmholtz

and Hering in the 1860’s this interest came to a culmination. It

had resulted in the accumulation of a very considerable body ofdetailed descriptive fact.

We have here to consider, however, only

the way in which the facts of eye-movement came into relation to

the problem of visual q)ace perception.

The two most discussed laws of eye-movement are Bonders’ law
and Listing’s law. The facts of the former were established by
Bonders in 1846, although it was Helmholtz in 1866 who called
the principle a law and named it for its originator. Listing’s law

was formulated and thus named by Reute in 1853. Apparently
Listing never published the law himself. To understand the im-portance of these laws is to understand one of the problems ofvisual space perception in the middle of die nineteenth century.

Bonders’ law states the principle that for any direction of regard

BONDERS’ AND USTING’S LAWS

231

the eye always assumes the same position. It is conceivable that theeye might rotate about its own axis as it variously changes fixation,and so come to a given direction of regard, sometimes with one

amount of torsional rotation and sometimes with another. Bonders’law denies such variation. If there is torsion, it is always the samefor any direction of regard. The effect of the law is to establish thefact that the retinal image of any object fixed in the field of vision

wiU, for any given position of the head and fixation of the eye,always fall upon the same retinal points. Thus Bonders’ law becomes the basis for a constancy theory of localization: if the orientation of the head and eye are known, then the position of aperceived object in relation to fire vertical and horizontal of thevisual field is determined by the retinal points stimulated.
Listing’s law states that, when the eye moves toany position

from the primary position (the natural position in looking horizontally straight ahead), it rotates about an axis that is perpen-

dicular to the initial and final lines of regard at the point of tiieirintersection.

This is the simplest sort of rotation possible.

It isrotation without torsion: or at any rate, there is no torsion of theeye about the line of regard as an axis. So simple is this principlethat it is often supposed to be self-evident.

Why should the eye

undergo torsion about its own axis in moving from one fixation toanother? The importance of the law becomes apparent, however,when one understands that the geometry of rotation requires theeye under ordinary circumstances to undergo some torsion.
Consider the bloek shown in Fig. 29. This block is so fixed that it

can rotate about the point 0, If it rotates from position 1 to position 2 without torsion and about O, it will be oriented as shown. If

next it rotates without torsion from position 2 to position 3, then it

wiU again lie as in the figure. If finally it is rotated without torsion
from position 3 back to position 1 again, then we are faced wiffi thecontradiction that altogether it has undergone torsion throng 90”,
for the shaded side will now be up instead of in front. The threemotions described are the sort of motions prescribed by Listing’s
law. Yet these three motions, each separately without torsion,

have the effect of producing very considerable torsion. Thus, if
the eye dways moved in accordance with Listing’s law, then it

would disobey Bonders’ law, because it would codie back to thesame position with different amounts of torsion about its own axis.

Hence it follows that, since Bonders’ law is true, the eye is subject

AREAL VISUAL SPACE PERCEPTION

232

to torsional rotation in most of its movements. Listing’s law states

only a special case, viz., that movement from the primary positionis without torsion.

There is still the question as to why psychologists became interested in the special case of move-

ment from the primary position.
This question is answered as follows. Donders’ law stated that forany direction of regard the eyealways has the same torsional
position. But just what torsional

position does it have in any given

position? It has the position thatwould be given it by movingfrom the primary position to the
given
Fiq.

29.

Kinematics or
TobsionOcuuB

positioninaccordancewith Listing’s law. Thus Donders’law shows that the actual posi-

were rotated troio

tion of tho eye is the same forposition 1 to position 2 about anany dli'ection of regard, and List-

If the block

axis

through

0 perpendicular totho plane of rotation, it would horotating according to Listing's law.

Similar lotafaon would bringIt

towere now rotated
In tho same way back to position
again,
it1
would be found tohave undergone 80“ of torsional
position 3. If it

rotation:thecross-hatchedsidewould now be up instead of forward. Thus the olook would notobey Donders’ law. Since the eyeobeys Donders’ law, it follows thatitcannot move in accordance withthesimple principleof Listing'slaw (without torsional rotation) except when moving toward or fromthe primary position,

ing's law specifies what that posi-tion is.
It must have been all this con-temporaneous discussion of eye-movements that led Lotze to his
theory of visual local signs in1852. Tliough he did not mention
Donders or Listing in that discussion, Lotze did assume simplicity

and constancy of eye-movements.

Any given retinal point, he argued, becomes associated in experience with the series of impressions that would be produced if

the image of an object moved from the given point to the center ofthe retina, that is to say, if the eye moved so as to fixate the peripherally perceived object. Since the eye tends automaticallyto fixate

peripheral objects, these associations might easily be set

up—soLotze thought in 1852, His theory depended, however, on the truth

.

NATIVISM AND EMPIRICISM

233

of the principle that fee eye moves from any one position to any

other in accordance wife immutable laws and not fortuitously.

Nativism and Empiricism

We have already seen (pp. 27-32) how, in fee second half offee nineteenth century, there was a great lo-do about fee origin of

fee individual’s idea of space. British empiricism made it appear
that fee knowledge of space, like fee knowledge of everything else,comes out of ejEperience by way of fee senses. Kant, holding thatspace is an a priori intuition, added fee weight of his prestige tothe view feat fee conception of space is innate in the individual

and is not learned. Johannes Muller, acknowledging Kant's authority in this matter, held that spatiality is intrinsic to fee mind,

which arranges its impressions so as to build up its idea of space.
Hering was the first explicit nativist, however, writing after Lotze,

who was, except for fee associationists, fee first explicit empiricist.
The later exponent of nativism was Stumpf
Although Lotze can be placed at fee head of fee modern empiricistic line, he was, in this matter as in other philosophical afiairs, acompromiser and synthetizer: he admitted fee Kantian contention
feat spatiality is intrinsic to mind, but held further feat space, as itisknown, is something more than spatiality, feat it is an organiza-tion or system generated in experience. To the support of Lotzecame Helmholtz and Wundt, who feus bore fee weight of fee
empiricistio tradition over against Hering and Stumpf. Kiilpe andTitchener belong wife Hering in feat they believed extension to

be a primitive attribute of visual and tactual sensations, but theyalso belong

wife Wundt in their assertion feat locaBzation islearned. Gestalt psychology stems from Hexing: for it, form as

well as extension is native.

No simple exposition of this great and largely fruitless controversy can, however, be adequate to its complexities. For one
thing, almost every protagonist turns out, whatever he was called,

to have been both nativist and empiricist, Everyone believed featfee organism brought something congenitally to the solution of the

problem of space; everyone believed feat fee organization of space

may be altered or developed in experience. The differences lie in
fee way the men viewed the different parts of fee total problem,

AEEAL VISUAL SPACE PERCEPTION

234

for within the total problem

we find part-problems, which have,for the most part, not been dearly distinguished and which there-

fore confuse the issue. Let us take up diese part-problems separately.

(1) SpatialUy. Although the nativists looked to Kant for authority in their quarrel with the empiridsts, the fact is that both—namely,groups admitted one fundamental Kantian principle
file

tliat

capacity of the mind to conceive such relationships as ulti-

mately come to make up the idea of space is given in its primarynature and not developed in particular experience. To accept thisview was natural enough for Johannes Muller, writing in 1820, sosoon after Kant. It was natural too for Lotze in 1852 to suppose thatthe local signs would never have got themselves related into a con-

cept of space had not spatiality been intrinsic to the mind. Helmholtz, who was at great pains to show that the axioms of EucUdean

geometry are founded upon experience and are not innate, nevertheless admitted that space itself may be ‘ti'anscendenlal.’ So too
Wundt was really allowing the validity of this Kantian categoiywhen he held that the sensory elements can be organized in space
to make up die rdumllche Vorstelkmgen. Wundt admitted only

quality and intensity as attributes of sensation; space and time

were hi his system frames of reference for the patterning of sensory
complexes. Kiilpe, on the other hand, in bringing in space andtime as attributes of sensation showed diat he thought extension

and duration to be just as primitive in experience as quality andintensity. Titchener followed Kulpe. Although he said in 1910 that
this primitive experience of extensity is necessary for the idea ofspace, he did not believe that native extension explains localization any more than did the other empiricists.

There was, there-

fore, really no psychologist in the nineteenth century to deny the

Kantian doctrine of the a priori nature of space at its fundamental
level. The difiference of view appeared at the higher level of theorganization of spatial perception.

(2)

Loed sign. The outstanding fact about visual and tactual

space perception is that the spatial relations of the pattern ofstimulation get themselves more or less correctly represented inperception. Perception, within limits and with known exceptions,mirrors stimulation. Thus in general the stimulation of three points,
abc, in a tow, with b lying between a and c, gives rise to a perception ABC, with B between A and C, and a correspondence ofALOCAL SIGNS

235

with a, B with b, and C with c. This fact means not only that thethree stimulations, a, b and c, cannot be identical but that, becauseof their differences in position, they possess local characteristics

which are reflected in the differentiation of the perception. In thissense every point must have a ‘local sign,’ be that sign a conscious
quality immediately indicative of the position of the point or aphysiological potentiality for giving rise to different perceptual
effects. Such an effect in perception

may be a label of locality, likethe visual image of a tactual stimulation, or it may be a perceived
relation, like seeing the order

ABC for the stimulus order abc. In

this broad sense all the physiological psychologists of the nine-

teenth century believed in local signs.

As we have aheady seen (pp. 28 f.), it was Lotze who, in 1852,
originated the theory of local signs. TTiat every retinal and tactual

point is distinguished from every other one was his chief tenet.

For him these local labels were not simple quabties that varied
from place to place, but patterns of intensities—tactual patterns
for touch, intensities ofeye-movements for vision. His general

theory was never worked out in detail, was open to many objections; nevertheless it started a trend in thought that occupied at-

tention for a long time.

Wundt, rejecting Lotze’s notion of intensitive patterns, believedin distinct local qualities which characterize every retinal or cuta-

neous point of stimulation. He founded this belief upon the introspective fact that difference in localizationisasimmediately

obvious in perception as any other qualitative or intensitive difference. To an empiricist, like Wundt, tire local signs had to be purely
qualitative, or at least not consciously spatial; while they serve todifferentiate the sensations, they do not at first signify tire spatial

arrangement of the sensatiorrs. The spatial relationships must be
learned.

The nativists, on the other hand, though also believers in local
signs, thought of the signs themselves as intrinsically spatial: givenknow without experience that b
we have already seen, Hering and Stumpf

tire signs for a, b and c, one could

lies between a and c. As

were the chief exponents of this view. Hering went so far as toposit three local signs for every retinal point: one for height, one
for breadth and one for depth.

There were still other psychologists who believed that the local
di§erentia is unconscious. For them two sensations could be iden-

AREAL VISUAL SPACE PERCEPTION

236

tical in all conscious respects and yet have different potentialities

for their effects.

Many of the associationists held such a view. They

considered sensations to be differentiated spatially, not by theirown conscious characteristics, but by the different associations
that they are able to acquire. Kulpe made this position explicit.
Sensations in different places may be identical in quality, intensity, extent and duration, he held, and yet come to be distin-

guished associatively. For instance, identical pressure sensations

on the left and the right index fingei's aie immediately discriminated by the associative context of visual imagery that localizes
each differently. In other words, sensations alike in all of theirconscious athibutes are still capable, because of a physiologicaldifference in their excitations, of forming different associations.

Titchener’s theory was similar to Khlpe’s.

Thus there were four views about the local sign. Lotze thoughtof it as (a) an intensitive sensory pattern. Wundt held that it is(b) a simple quality. Kulpe found evidence only for (c) an unconscious physiological predisposition. Thesemen all count as

empiricists because they thou^t that non-spatial characteristics,

whicli vary with position although not intrinsically spatial, comoby learning to signify position. Hering on the other hand, heldthat the local sign is (d) origirrally intrinsically spatial, indicating
position at once without learning.

(3) Localization. Obvious from what has been said is the factthat the empiricists believed the discrete quaUtative local signs

become related in experience in such a way that each point
acquires a position in relation to the others and aU the points to-gether form a spatial continurrm. These relationships were established, they believed, by the continuous movement of stimulation

across the retina or the skin. That was Lotze’s view and Wundt’sview. One learns that b lies between a and c because the order ofstimulation is a-b-c.

Wundt eventually devebped an elaborate

schema of space perception in which all visual and tactual localization was established by reference to the kmesthetic sensations thatare aroused in the movements of the eyes and body. The continuityof space,he held, comes fram the continuity of experience In

movement.
f

Strange to say, the nativists did not succeed in avoiding the

problem of the genesis of space. Hering, for one, was forced to
explain how visual spaceisbuilt up in relation to a “nuclear

RELATIVE AND ABSOLUTE SPATIALITY

287

plane,” as well as to meet many other difficult problems of theorganization of visual space. His nativism did not spare him muchpains.

Status praesens.

We have already considered in Chapter 1 (pp.

32 f. ) the fates of nativism and empiricism. The nativism of Heringis

now lost in the larger nativistic phenomenology of Gestalt psy-chology. The empiricism of Helmholtz has given place to the behavioral theories of the positivists. These systematic faiths are,however, no longer so important as the experimental findings. The
modern emphasis is on fact, though the underlying systematic bias

may determine emphasis of the interpretation. Let us examine, withthis matter in mind, two experiments neither of which is yet out ofdate.

(l)The first experiment is empiricistic and associationistic inthat it shows how a localizing context can be changed by learning.

Stratton in 1898
if the date is—the insight ofthis experiment ismodem evennot—tried the effect of reversing the field of vision,

up for down and right for left, by a system of lenses which hewore during the waking hours of eight consecutive days. Thoughconfused at first, he presently became quite satisfactorily adjusted
to the inverted field. What did this discovery mean? In the older

terms it would have meant that the local signs can acquire in experience either new spatial qualities or new relations to one another. Stratton, however, envisaged the problem as one of external

relativity—“the interorganization of motor, tactual, and visual experience.” If a man, seeing the ceiling and reaching for it, finds thefloor, he is not well oriented

in space, and that is approximately

what happened when the reversing lenses were first put on. Later,
after a period of conflict and of deliberately being ‘right’ by mov-

ing the ‘wrong’ way, the seen world ‘turned right-side up’ in thesense that the correct movement followed automatically upon thevisual perception. Thus Stratton may be said to have settled both

Kepler’s problem of erect vision withan inverted image andLotze’s problem of the role of experience in space perception, by—showing that the ‘absolute’ localization of retinal positions^up-

down and right-left—are learned and consist of bodily orientationas context to the place of visual excitation.

(Ewert repeated Stratton’s experiment in 1930, achieving similar results withalmost complete readjustment in twelve days of)

AREAL VISUAL SPACE PERCEPTION

238

wearing the lenses, He worked quantitatively, plotting the learning curves which describe the couise of readjustment.

(2)

The other experiment, in spite of the fact that it involves

the learning of spatial relationships or form,
nativistic,isfundamentally

because it offers no explanation as to how a straight

vertical line in visual perception differsfrom a bowed vertical,

except to assert that die one or the other is given directly in experience. Gestalt psychology, of course, tends to interpret theseresults as meaning that the straight line

is

more

natural’ thanthe bowed, but that too is a kind of nativism, a faith that certain

dynamic principles are given in the nature of the organism, notacquired in experience.

Wooster in 1923 and Gibson in 1933 found that perceived vertical lines,

when bowed in perception by having the subject

wear prismatic wedges in a spectacle frame, become straight if
die wedges continue to be worn. If for both eyes the wedges taper

toward the left, then the verticals appear bowed to the left. Afterthe lines have become straight under ‘adaptation’ and the glasses
are removed, verticals will for a while appear bowed to the right,

a case of ‘successive contrast.’ This whole process can take placein an hour and the amount of Teaming’ be measured by seeing

how much a flexible rod must be bent in order to appear straight.
In other words, we see straight verticals as they are, not so muchbecause they are such, as because the organism is the kind oforganism that tends to see verticals and near-verticals straight.

Geometrical Optical Illusions
Strictly speaking, the concept of illusion

has no place in psy-chology because no experience actually copies ‘reality.’ Certainly

John Locke’s secondary qualities are ‘illusory’ in the sense thatthey do not correspond to the object, and Lotze remarked muchlater that color is an illusion because the color is “in us” and notin the outer world where there exists only light of various wavelengths, Lotze in his chapter on sensory illusions (1852) discussed
color, sensation in general, die two-dimensional projection of thethree-dimensional world on the retina, after-images, the percep-

and after-images of rotation, and many other phenomena
where the lack of correspondence between sensation and stimu-

tion

lus is obvious. In the sense that perception is normally dependent

GEOMETRICAL ILLUSIONS

239

upon subjective factors as well as upon the stimulus, all perception is ‘illusory’ in so far as it does not precisely mirror the stimulus.

In this broad sense the term fusion becomes practically meaningless.

The psychologists of the late nineteenth century, nevertheless,found diemselves much concerned with illusions, especially withthe geometrical diagrams that give rise to such visual perceptionsof extent as form exceptions to the general mles. To account forthese exceptions theory after theory was devised.

The interest

was clearly recognized about 1860. Thereafter, for perhaps three
decades, a few of the classical illusions were discussed whenever
the problems of visual space perception were systematically considered.

A knowledge of the principles governing the abnormal

perception of extent would certainly help, it was thought, withthe understanding of the normal cases. Then in the 1890’s there

was a sudden culmination of this concern with the subjective conditions of form. Papers

and theories multiplied. Not only were

new illusions found, but variant forms of die old illusions were
fixed up as experimenta cruds for the theories. One bibliography
lists thiity articles

on these illusions during the

1890’s, fliough

less than half a dozen in each of the three preceding decades. In

the present century the study of illusions has continued as an interesting but not important sector of psychology. The rise of Ge-

however, has creat^ a new concern with theways in which visual perception realizes its form and pattern in-stalt psychology,

dependently of the stimulus, or at least without mirroring thepattern of the stimulus. Thus Gestalt psychology has made theold problem of the illusion broader, given it a new significance,and provided it with a new set of explanatory principles.

The interest of psychologists in geometrical illusions may besaid to have begun (oa. 1833) with the reversible perspectives,

but we must leave this matter for discussion later (see pp. 268271). Subsequently there arose, first the problem of interrupted
extents,

and then the problem of the overestimation of verticals

in respect of horizontals.

In a study of geometrical illusions carried out in 185S, Oppel
showed that a row of dots appears to occupy a greater extent than

the same empty distance between two dots, and that a line inter-

rupted by cross-bars seems longer than the same line without thecross-bars.

He made up, in fact, various illustrations of this prin-

240

AREAL VISUAL SPACE PERCEPTION

ciple. Here was an important fact of space perception, one which

Bering tackled in his &st important scientific publication ( 1861).
Bering suggested that the perceived distance between dots

might be taken to depend on the chord of the arc connecting thedots on the spherical surface of the retina, and that the chord be-

tween the two extreme dots, wili empty space between them,would be shorter than the sum of flie chords between successive
points in the row of dots. Kundt (1863) and Aubert (1865) bothmade measurements of the illusion. In 1866 Helmholtz publishedHELMHOLTZ'S SQUARES
Fig. 30.

iNTEHnuPTED amd Vebucai. Extents: Helmholtz (1888)

the two squares of lines shown in Fig. 30 to show that the effectof interruption may more than compensate for the ovea'estima-tion of verticals. Because the two tendencies work together when

the interruptions

lie

in theverticaldimension, the left-handsquare looks much taller than wide. The middle square, however,looks broader than it is high, for here the horizontal interruptions

more than overcome the lengthening effect of the vertical.
It was Wundt who, in 1858, called attention to the tendency tooverestimate the vertical as compared with the horizontal. Already he was supporting the theory that judgments of extent are
based upon eye-movements. Because of the arrangement of theeye-muscles, he pointed out, vertical eye-movements are more difficult than horizontal. The eyes need, moreover, to have greater

freedom for horizontal motion in the caseof dwellers

on thehorizontal surface of the earth. This general view Wundt main-tained all through his life, although in the twentieth century eye-movements have been shown to be less impoitant in judgmentsof extent than Wundt had supposed them to be. Belmholtz, as

we have just seen, attested the validity of die vertical-horizontal
illusion with his lined squares.

There would be no profit in an attempt to list and classify all
the geometrical filusions and their variants.

We Can get the pic-

GEOMETHICAL ILLUSIONS

241

ture of what waa going on if we select a half-dozen of the best-

known classical figures and see how they originated.
(1) The Poggendorff figure (Fig. 81) is the first of the illusionsof direction. Mentioned to 2!ailner by Poggendorfi, it was described by Ziillner in 1800. Helmholtz and Hering and Wundt all

discussed it without haming it, and it was not given its originatot’s

name until 1896. In explanation of it there have been many theo-

!

S'

in

S!
i

i!
!

i!

S'

ZOLLNER'SnSURE

FIGURE

Fio. SI. Pogcehdohff's and ZStuna’s Ficusas (1860)

The diagonal lines in the Poegendoiff figure appear slightly displacedwhen intenupted by die verticalrectangles. Similarly the short diagonals
In the Zdllner figure seem displaced by the vertical fines, so that thereis

an apparent shift that makes me marks look like a nonius or vernier scale.
is also a complementary shift of the verticalIn the Zdllner figure therelines.

ties.

The illusion has been referred to eye-movements and also toa tendency to overestimate acute angles.
(2) The Zolber figure (Fig. 31) in a sense starts off the illusions
proper. It is a special abnonnal case, and more striking than the

Poggendorff illusion. Originally it was described as a “nonius dis-placement" because the little cross-pieces on either side of the line

do not seem continuous, but displaced relative to each odier, likethe scale marks on a nonius or vernier against the edge of its
measuring scale. The ZSUner illusion is a dramatic elaboration of
the principle involved in the Poggendorff illusion.

(8) The Hering lines (Fig. 82) are well known because the apparent bowing of the two paraEels is so striking. Hering presented
this figure in 1861 along with another which shows that the idea

arose as a variant of the ZoUner figure.

242

AREAL VISUAL SPACE PERCEPTION

Fig. 32.

HERINQ’SFIGUREWUNDT'SFIGURE

Hiring’s( 1881 ) and 'Wundt's(

1896 ) Figures

The bowed parallels of Herin^s Bguie extend die principle of Zbllnei's
ffluslon.

Wundt’s figure is compfenentary to Hering’s.

(4) The Wundt lines (Fig. 32) are the companion to the Heringlines. Simply

reversing the motif, they show the parallels flaring

at the ends. They date much later, having been first published inGEOMETRICAL ILLUSIONS

243(S) The Helmholtz lined squares (Fig, 30) are fully as important historically as the preceding four figures.
lished them first in theHelmholtz pub-

tod part of the Fhysiohgische Opttk in

1866. The squares introduce the principle of interruption and theprinciple of vertical-vs.-horizontal, whereas the preceding four
illusions are all illusions of direction of the

Poggendorff-ZoUner

type.
(O')

Perhaps the most famous geometrical illusion of all is theMiiller-Lyer figure of 1889 (see Fig. 33). This is a straight illusion of extent; the middle sector looks longer

with the arrow-feathers than widi the arrowheads, It has been repeated again and again in

the psychological texts of the last fifty years,

and Miiller-Lyer himself described more thana dozen variant forms. The amount of this illusion in several of its forms was measured by

Heymans in 1896. The figure has been used as
an example for almost aE the different theoriesof the geometrical Elusions.

There were many classifications of the kindsof iEusions, Iflce Wundt’s in 1898, but in general they all boEed down to two groups: fllu-

MULLER -LYER
ILLUSION
ConvluxionPahai)ox:MulFio. 33(1889)

sions of extent and iEusions of direction, to which may be added

some special complicated cases. Actuafly it was not always possible to keep the iEusions of extent and direction separate;

Z&E-

ner’s Elusion was classified first as a “nonius-like” displacement of

the cross-lines, and later as a shift in the direction of the principal
Enes.

There were even mote theories than classes. It is, indeed, possible to list twelve different 'theories’ of the MiiEer-Lyer iUusion

for the perifid 1889-1902. Because this phenomenon was then the

ground of considerable controversy, we may briefly examine theisoussion in order to understand the character of the theorizing.

The MuEer-Lyer illusion or “paradox," as it was called (Fig.
33) consists of a principal line to which wings are attached.
When the wings extend die figure by making obtuse angles withthe principal line, then the line is judged as longer. When thewings make acute angles, returning upon the line, then to line
seems to be shorter. This is an Elusion of ‘assimilation’; to line
appears altered in length in the direction of the wings. Without

244

AREAL VISUAL SPACE PERCEPTION

the wings there is no illusion. How then do the wings enter in?
Is the line ‘actually’ altered in length by them? or does the subject

judge the distance between the wings when he supposes he is judging the lines themselves?
(1) Muller-Lyer himself
fluxion.”first

offered the principle of "con-A given line seems longer as the side of an obtuse angle

than as the side of an acute angle. The arrow illusion is simply,

he held, a multiplication of this simple effect. The principal line
changes—‘flows’—in the direction of the wings. This view implies
a sensory shift in the actual length of the perceived line.

Other similar theories suppose the judgment to be based, noton the principal line alone, but on the fact that the wings by theirpresence enlarge the basis of judgment. (2) LAska, noting how

one tends in imagination to close open figures by the shortest possible lines, suggested that the more open of the Miiller-Lyer fig-

ures would seem the larger because closed by longer lines.
(3) Delboeuf thought that the wings would attract the regard

away from the ends of the lines so as to create the illusion. ( 4 ) Similarly Brunot argued that the judgment would be based upon
the mean distance between the wings instead of the distance between the exact ends themselves. (5) Einthoven supposed that
there might be enough dispenion of excitation at the retina tomake a difference in the average lengths of the retinal images.
(6) Auerbach stressed the influence of seeing the total figure inindirect vision,and (7) Schumann sought to explain this andmany other illusions on the principle that one judges, not a single
element, but the total impression. In a sense all these theories aretheories of total impression as the determinant of judgment.

In contrast to such theories of total impression there were several dynamic theories, which supposed that the extensitive judg-

ment was mediated by eye-movement, or the tendency to eyemovement, or by a conscious act. (8) The chief exponent of theeye-movement theory was, of course, Wundt. He held that the eyes
move beyond the ends of the line for the obtuse-angled wings andthat they are checked before the ends by the acute-angled wings.
Although experiments later verified this fact, stfll o4er experiments have ^own that the illusion holds in negative after-image

and in tachistoscopic exposure where there cannot be effective
eye-movements. (9) Heymans’ theory did not suppose actual
movement, but was based on the tendencies to eye-movement that

THEORIES OF THE MOLLER-LYER ILLUSION

245

the wings would create. (10) Lipps was the originator of the concept of empathy as explaining many esthetic phenomena. He wasan act psychologist, a believer in the theory that the contents ofconsciousness are all acts. For him the Miiller-Lyer iUusion was

explained hy the fact that perception is an act and that the acute-

angled wings limit the activity, whereas the obtuse-angled wings
free it In a sense too Schumann’s Iheoiy of total impression was
also dynamic, for he beReved it to be due to the act of attention

that adjusts itself to the total impression.

There were also two important special theories. (11) For Brentano the iUusion was a special case of the general principle that
acute angles tend to be overestimated and obtuse angles underestimated. Subjective changes in the angles could compress or
stretch the principal line accordingly. (12)phenomenon to perspective.

Thi&y referred theHe saw the illusion in the third

dimension, like a saw-horse. The acute-angled figure would be asaw-horse with the legs extending away from the observer, theback near and hence relatively small, whereas the obtuse-angled
figure would he Ihe saw-horse with the legs approaching the observer, with the belly far away and therefore relatively large.

Amongst all these theories there could be no decision. The problem of the geometrical illusion is not a special problem of spaceperception, When the general laws are known, the illusions will
also be understood. This Hurry in illusions in the 1890’s did some-thing more for psychology, however, than estabhsh certain phe-nomena as interesting psychological curiosa. It fashioned a problem and bequeathed it to Gestalt psychology. An implicit assumption of the 1890’s was the notion toat the retinal image is a pretty

good copy of the stimulus, and that the perception is a pretty good
copy of the retinal image. Gestalt psychology changed that. It

showed the correspondence to be less than had been supposed. It

showed that, even when the perception comes close to matching
the stimulus, it may not match the retinal image: as, for example,

when perception puts back the third dimension of the stimulusthat was lost in the bidimensional retinal image. It showed thatthe problem was not a special problem of illusions but the general

problem of visual space perception, and it brought new conceptions to bear upon the solution.

nature in the next section.

We shall see something of their

,

246

AREAL VISUAL SPACE PERCEPTION
Dynamical Gestalten

Tlie chief contribution of Gestalt psychology to the psychologyof perceived form was its insistence that the perception is formed

under certain dynamical laws which give it its specific psychological organization.

A perception is not a copy of Its stimulus;

indeed, if it does turn out to represent its stimulus fairly accurately,that result may be the consequence of the interaction of manyof the organism’s properties. For instance, a three-dimensional

stimulus gives only a two-dimensional image on the retina, yet

the organism has the capacity under certain normal di'cumstances
to reconstitute the bidimensionality in the perception.

While itremains true that the retinal image is the primary basis for theperception of visual form, nevertheless it can be shown that manyof the characteristic features of perception are added by the cen-tal nervous system, some of tiiem determined, not by tiie stimulus, but by the organism, its attitudes and its past experience. Thischange in the conception of the nature of perceived form cameabout gradually.
In 1690, when the interest in optical illusions was mounting,von Ehrenfels enunciated the doctrine of GestakqiuilUiit or formquality, which we have already considered in Chapter I (pp. 16 f. )A form, like a geomehical shape or a tonal melody, is somethingover and above the elements (lines, tones) which combine tocreate it. Form is a “founded content,” said Meinong, based upon

the elementary “founding contents.” In general, however, formquality came to play the role of a superior element, for the psy-chology of the nineteenth century took elements too seriously to

be Rghtly dispossessed of them,

A surer step in the rejection of elements came with what has
sometimes in retrospect been called experimental phenomenology.
Since elementism had done aR it could for psychological discovery,some new conception was needed. To say that form is a kind of
higher element did not point the way to research, and the unsuccessful attempt of Kiilpe’s school al Wurzburg to account forthought as a new non-sensory element (1901-1907)

still

further

discredited elementism. At Gottingen and at Frankfurt, however,there came mto being the method of the phenomenological description of perception without regard to its analysis into elements.

SCHUMANN ON VISUAL FORM
and it is these experimental

studies that247

show the continuity

from Wundtians to the Gestalt psychologists.

The first of these events was Schumann’s studies of visual spaceperception which he published in 1900 to 1904. Formerly a pupilof G. E. Miiller’s at Gottingen, he was then at Berlin with Sturapf.

Undertaking to examine the visual perceptions of shape, size anddirection,

he found their analysis into sensory elements of nohelp to him. He sought, therefore, to understand the phenomena by describing

them, and for this purpose he appealed
to the concept of attention. First he notedthat attention may bind the parts of a
figure into a unitary whole, so that the

Fig.

34.

parts, becomes effective. That is the caseof the MiiUor-Lyer illusion(Fig. 33),

where the observer judges not the line,
but the total impression of the line with

(IDOO)

The

square,largerent

andfigurelikea differ-

because,ac-cording to Schumann, attention

served-attention may abstract some es-verticalsential part from the whole, to therotatedthrough 4S degrees, looks—Schumann ob-

the wings. Contrariwise

Schumann

Squabe and Diamond

total impression, instead of some one of its

is

given

and

to

the

horizontal

dimensions in each case.

endthat the perception takes its character from the part. Such is thecase with the square of Fig. 34, which, when rotated through 45
degrees, looks larger and likea diamond. We attend, he said,

primarily to the vertical and horizontal dimensions; a square withits diagonals vertical and horizontal looks different from the squarethat stands flat upon a side, and it also looks larger. Because Schu-mann thus sought the explanation of perception in the descriptionof the immediate experience, he is entitled to rank as one of theearly phenomenologists.
It was quite clear that Schumann was using the word attention asa dynamical principle under which perception is organized; hewas making, in short, a first formulation of what was later to besaid so much more dearly by the Gestalt psychologists. Look at

Schumann’s diagrams in Fig. 35. According as “attention” organizes them, the black squares can be perceived in an endless varietyof patterns. One can see columns of squares, or rows, or diagonals,

or sets of four squares, or rectangles of four-by-six squares, andso on. ’There are, in other words, dynamic factors which determine

AREAL VISUAL SPACE PERCEPTION
the nature of the perception and which depend upon the perceiving person, On the other hand, neither Schumann cor anyone else

has supposed that perceptionisindependent of the stimulus.

There has to be something to perceive even thou^ the exact formof the perception may be subjectively determined. Tlius Schumannpresented the unevenly spaced black carcles of Fig. 35B to showthat objective conditions may favor one kind of grouping overA
Fic. 35.

B
Schumann CBECXXBBOAans (IQOO)

A; the squaies group diemselves under the attention of the subject Invarious patterns; tows, columns, diagonals, groups of two by two, four byfour, four by two, etc. B: the circles behave in a similar manner,

objective grouping predisposes toward certain patterns

but theirand makes otherpatterns difficult to form.

another. Some of the groupings that are possible with the squares

oaimot be easily formed with the circles. In the same way the difference between the ‘square’ and the ‘diamond’ of Fig, 34 depends
initially upon stimulus-position, but secondarily upon theway inwhich the subject’s attention is related to the stimulus. The subject is quite capable of seeing die ‘diamond’ as a ‘twisted square,’or vice versa.
It is possible now to see how the phenomenological method
was being introduced into psychology during the first part of thepresent century. The philosopher Husserl, having taken the word
phenomenoUgy from Kant and Hegel, applied it to the study of

immediate experience or “pure being" (1901). Stumpf at Berlin( 1906)

took over the term for the study of all experience, without

EXPERIMENTAL PHENOMENOLOGY

249

systematic bias, in and of itself. Schumann’s study of perception
at Berlin (1901-1904)

had been, as we have noted, essentially aphenomenological study. Next we find the method and the word
turning up at GBttingen in G. E. Muller’s laboratory, with Jaensdi,

Katz and Rubin.
E. R. Jaensch in 1909 published from Gottingen a monographdealing with the Aubert-Fiirster law, the principle that visual acuity is greater for neat objects than for far. This is the sort of fact
tiiat

leads to the consideration of dynamical interaction within

total systems, for it shows spatial discrimination to be dependent

upon other aspects of the perceptual situation than the mere
separation of stimulated retinal points. In 1011 Jaensch put out

another monograph in which he dealt with the visual perceptionof depth, the phenomenology—he used the word—of empty space

and the nature of its psychic representation, and certain problemsof perceived size where size variK independently of the size of theretinal image. That Jaensch was using the phenomenologicalmethod and dealing with the sort of perceptual problem thatlater was to be the primary concern of the Gestalt psychologists
is evident.

It was in 1911 too that Katz brought out his study of the modesof appearance of colors. Althou^ not primarily a study in spaceperception, its effect was to show that the problems of quality andspace cannot be separated, and the method was a perfect exampleof phenomenology. That visual experience was necessarily limitedby the properties of the retinal excitation had been an assumption of the older psychology, It assumed, for instance, that monocular experienceisbidimensional because the retina

is

bi-

dimensional, and that acuity and color are functions of the natureof the action of the retinal elements. As a phenomenologist Katz,

on the contrary, could forget about the retina and describe experience in its own right. He found fliree kinds of cobts: (1) the
surface colors (Oberflachenfarben), which are bidimensional andlocalized at a given distance and which are In general the colorsof perceived objects; (2) volumio colors{durcMcMge, raum-

hafte Farben), which are the tridimensional colors of transparent

media, like colored liquids, colored air or a completely hghtiess
space; and (3) film colors {FlSchmfarben), which’ are primary

and without localization or precise spatial characteristics, like thecolor

m a spectroscope. Katz invented the “reduction screen,” a250

AREAL VISUAL SPACE PERCEPTION

screen with a hole in it. Viewed through the hole a colored surface is seen as a film color instead of a surface color, because thescreen eliminates perception of everything (position, relation tosurroundings, general illumination) that provides the context for

the establishment of the spatial characteristics of the color.

Byelimination of this context a surface color is “reduced” to a film,

Although the plea for phenomenology is essentially negative inthat it demands freedom from convention in the formulation of descriptions of events, nevertheless it has been justified by its positive results; and Katz’s monograph was one of the first to

show

clearly how the conventional rubrics of psychology had been limit-

ing discovery.

In 1915 Rubin published from Muller's laboratory—he had be-

gun the research in 1912

—a study of figure and ground in visual

perception. He found that a visual perception normally divides
into two fields: a figure, which is usually the object of attention,

and a ground which occupies the rest of the perception. This distinction becomes especially dear in such ambiguous fields as areshown in Fig. 36, where a black figm-e can be seen upon a whiteground, or a white figure upon a black ground, Figure and grounddifier, according to Rubin, phenomenologically, Tlie figure, whidi
is seen as a whole, looks like a thing or

an object {Dlngcharakter),whereas the ground appears not as a thing but as a substance(Stoffehardkter),

The figure appears nearer than the ground,which usually seems to continue behind the figure, thus giving
the impression that the bounding contour belongs to the limited
figure and not to the continuous ground. Moreover, die figure acts

as a whole functionally, and, being an object, tends toward con-

A shadow on the figure darkens the figure less than ashadow on the ground darkens the ground. In an ambiguous patstancy,

tern (Fig. 36)

what is first seen as figure tends to reappear as

figure if the pattern is seen again at a later time. If at a later time

figure and ground do become reversed, then the pattern may not

be recognized. Although Rubin published after Wertheimer, thefact that

he did this work at Gfittingen without knowledge ofWertheimer’s study on seen movement shows that the new experi-mental phenomenology, dealing in the dynamics of perception,

was in Ae air before Gestalt psydiology was established.
Wertheimer’s study of apparent movement was published in1912 from Schumann’s laboratory at Frankfurt. That it is regarded

EXPERIMENTAL PHENOMENOLOGY251

as the beginning of the movement of Gestalt psychology is partly

due to Ihe fact that it involved all three of the prime movers of
the new school, for Kohler and Koffka were Wertheimer’s chief
observers in the investigation. It is also true that Wertheimer fromthe first saw in the new phenomenology a general reorientationof psychology, whereas Schumann, Jaensch, Katz and Rubin were

Fro. 38.

Robin’s AnBicuons Fioores(

1915 )! Vase-Pbofiles andClaw-Fingehs
In each pattern fi^e and ground can be reversed. In A one can see awhite vase on a black ground or black proflIes on a white ground. In B one

can see a black claw on a white ground or white fingers on a black ground.

thinking within

the narrower

confinesof particularsubject-

matters. Wertheimer’s achievement was to describe movement inphenomenological terms, exhibiting it as a dynamic event in a perceptual field. He showed that discrete displacement of stimulation upon the retina is seen, if slow enough, as the successive ap-

pearance of two displaced objects, or,i fast enough, as thebsimultaneous appearance. Between these extremes, however, thereis

an intermediate speed of displacement which gives rise to the

optimal perception of movement, which may be indistinguishable

from the real movement in which the stimulation is continuously
displaced. Wertheimer thus succeeded in getting away from thenotion that perceived movement is merely the change of a sensation in space with time,

He realized that movement is itself an

252

AREAL VISUAL SPACE PERCEPTION

observable phenomenon, which may occur with actual movementof the stimulus and which depends upon such dynamical i elationships as the speed of displacement of the stimulation. (For a full

discussion of the nature and significance of Wertheimer’s paper,see pp. 595-599.)

Gestalt Psychology and the Laws of Form

As an aggressive school Gestalt psychology dates from about
when Kohler published his Die physischen GestaUen in

1920,

Rtihe und im stationaren Zustand, The next year he was calledto

Stumpfs chair at Berlin, and the Fsychologische Forschung,the journal of the Gestalt school, was begun. Die physischen Ge-

staUen is a book that provides a methodological foundation for
Gestalt psychology in that it heats of the general dynamics ofthe formation of form. Kohler dealt there with the development,change and stabilization of difierentiation within physical systems. He worked out the prindples, showing how the dynamicallaws hold only for whole systems and not separately for the parts.
Since he also showed that the dynamics of physical systems holdin many instances for perceptud fields, he could tlius undertake
to apply physics to psychology

by way of his principle of iso-morphism, a principle which asserts that the perceptual field corresponds to the brain field in such a way that the physical dynamics

apparent in the peiception mi^t actually be operative in thebrain. (Cf. pp. 83-90.)

With such a foundation it was quite natural that Gestalt psychology should start out with perception as its chief field of interest, and that visual form should be the principal kind of perception

studied. For more than a decade, in fact,ie systematic discus-

sions of Kohler, Koffka and Wertheimer used predominantly vis-ual patterns as expedmetta enwis to prove their points. Kohler
said, in fact, that Gestalt and form are almost synonymous.

Ex-

actly what then is it, we may ask, that Gestalt psychology has con-tributed to the psychology of visual form?

A precise answer to this question would involve the evaluationof this new movement, when unfortunately there is as yet no sufficient precipitation of scientific factfrom partisan opinion toestablish su^ a conclusion. There aremany laws’ of Gestalten

which in then formulations stiR reflept to some extent the personal

LAWS OP POEM

253

predilections of their authors. One cannot at present name six, or
thirty, sure principles that are ready to be taken over by scientificpsychobgy and accepted as truth with the names of their origi-

nators forgotten. Nevertheless one can pick out a fairly complete
list of themore important principles of Gestalt, those that apply

especially to visual form; and to that undertaking we may now ad-

dress ourselves.

There is a huge literature. From it in 1933 Helson extracted
114 laws of Gestalten. All but half a dozen of these laws are applicable to visual form; but

a great many of them, devoted toshowing that a Gestalt differs from a congeries of parts, may beignored here.

We can take it for granted that a visual form

isaunitary whole. As many of the other laws are related or overlap,

we can, by elimination of the less important and combination ofdie similar, come out with fourteen that represent the major contribution of Gestalt psychology to the knowledge of this subject

matter. Most of the principles are derived from the formulationsof Wertheimer, Kofflca, Kohler, Eubin and Sander. Most of theprinciples really specify dimensions in respect ofwhich forms

vary.
1.

Naturalness of form. A field tends to become organized andto take on form. Croups tend to form stmctures, and disconnectedunits to become coimected.
2.

Figure and ground. A form tends to be a figure set upon aground, and the figure-ground dichotomy

isfundamental to allperception. The simplest form is a figure of undifferentiated quality set upon a ground.
3. Articulation.

Forms vary from simple to complex in the de-gree of articulation or differentiation that they possess.
4.

Good and poor forms. A good form is well articulated andas such tends to impress itself upon the observer, to persist and torecur.
5.

A circle is a good form.

Strong and weak forms.

A strong form coheres and resists

disintegration by analysis into parts or by fusion with another

form.
6.

Open and closed forms. An open form tends to change towarda certain good form. When a form has assumed stable equilibrium,
it has achieved

closure. Thus a nearly circular seriei of dots mayachieve closure by being perceived as a circle.
7.

Dynamic basis of form. A form is a dynamic system or is

AREAL VISUAL SPACE PERCEPTION

254

based upon a dynamic system. Since the dynamic principles operate within the organism, a strong form is that which depends

more upon the dynamic properties of the organism tlian upon
the properties of the stimulus. The fact that the organism operates
to structure the perception means that there need be no corre-

spondence between the form of the stimulus and die form of theperception.
8. Persistence of form,

A form once perceived tends to persist,and to recur when the stimulus situation recurs. The recurrence ofpart of a previously perceived form tends to reinstate the whole.
9.

Constancy of form. A form tends to preserve its proper shape,size and color. This is the well-known “constancy phenomenon.”10.

Symmetry of form. A form tends toward symmetry, balanceand proportion. Many of the geometrical ‘illusions’ illustrate thisprinciple.
11. Integration of similars and adfacents. Units similar in size,

shape and color tend to combine to make belter articulated forms.

Near units also combine more readily than far. Fig. 35B illustrates
the effect of adjacency. The principle of the integration of similars would appear in Fig. 35A if certain of the squares were one

color and the other squares anotiier color. It would, foi example,

be easy to oieate thei'e the form of a cross by coloring the propersquares green and the others red.
12.

Meaningfulness of forms. A form tends to be meaningful

and to have objectivity. The more meaningful the form, thestronger it is, the more easily

it ispei'ceived,

and the longer it

tends to persist.
13.

Fusion of forms. Two forms can fuse, giving rise to a newform; or, in combination, the stronger one may persist, eliminating
the weaker. Simple, poorly-articulated forms fuse more easily thancomplex, good forms. A more meaningful form tends to predomi-

nate over a less meaningful one.
14. Transposition of form.

A form exists independently of its

constituent elements and may thus be transposed without change
to other elements. This is von Ehrenfels’ original law that a melody

independent of the particular notes that sound in it, and thata shape is independent of the quality and size of the lines thatisconstitute it,' The law is of wide application. It holds in sensory

discrimination where human subjerts and animals learn easily toTMNSPOSITION AND CONSTANCY

255

choose the larger, or the brighter, of two objects without regard
to absolute size or absolute brightness.

Of these principles the most Important mi^t be said to be thelaws of transposition and of constancy, partly because they are notobvious to common sense, but mostiy because they are generalprinciples, indicative of the organism’s broad capacities and limi-

tations in dealing with its environment.

The law of transposition is inherent in the conception that form
itself isindependent of the nature of its content. Mach’s notionsof space-form

and time-form mean that something exists over

and above the elements formed; it was such a form that von Ehrenfels calleda GestaUquolitat Transposition expresses a principleof relativity:

it isthe relations that persist independently of thecontents in the QestaUqualitiU, as Meinong pointed out. 'Thus one

may expect to find transposability wherever relationships are more
important than contents—a situation which has always been

known to exist in sensory discriminations of psychophysics. Of two
sensations the observer can say greater, equal or less with assur-

ance when quite uncertain of the absolute intensity of either.

While Wundt and others of the old school recognized this principle of the relativity of judgment, it was left for Gestalt psychol-ogy to identify it with tie law of transposition. Xbhler in 19171918 showed tiiat children, apes and chickens transpose a relationof size or brightness from one pair of stimuli to another, so thatthe subject, trained to choose the brighter of two grays or flielarger of two objects, may reject the stimulus originally preferred

when it is paired with another still brighter or larger. In the years
since 1918 there have been many extensions and confirmations of

the principle that the form or relation is the important datum ina discrimination.

The law of constancy is also not new. Many psychologists havenoted that persons see objects as they know them to be and notas the retinal image represents them. Helmholtz (1860-1860) ex-

plained the constancy of objects in perception by the principle(later rejected)of unconscious inference. Hering(1905) de-

scribed color constancy under the term memory color, and Katz

(1911) showed how memory color gives stability to die surface
colors of objects.

We have already seen how this diffierenoe led tothe solution of the problem of brightness and intensity in the series

256

AREAL VISUAL SPACE PERCEPTION

of grays (pp. 135 f.). In the 1920’s the rulecame gradually tobe recognized as a fundamental of Gestalt psychology. Later
Thouless (1931) conducted experiments on the constancy of size

when the distance between the stimulus and the observer varies,
of shape when the angle between the stimulus and the obseiwer
varies, and of brightness when the illumination varies. Since thephenomenon is not really one of complete constancy but only ofa tendency toward constancy, he called it “regression to the real
object,” meaning regression

toward the real object since the re-gression is seldom complete; and he invented a formula for meas-

uring the amount of regression. There was an extensive quantitative study of “constancy” of size and shape by Brunswik and his

associates in 1933. Brunswik made it clear that, since it serves tostabilize the ever-changing perceptual

world, object-constancy

has biological value for the organism. In the next chapter we return to the matter of constancy of size with varying distance (pp,288-299).
It should be noted here that the principles of transposition andconstancy are so closely related as to be often indistinguishable.

The law of transposition holds when relations remain constantwith change of content. The degree of the constancy phenomenon
can be demonstrated, however, only by a comparison with astandard, that is to say, by the establishment of a relation. Thus

both transposition and the constancy phenomenon depend upon
the constancy of relations when other data change. For instance,
the piece of white paper still looks white in the shadow because
its relation to the field is unchanged; but,when a reduction screen

eliminates the field, the relation is no longer perceived and thepaper is no longer white.

While it is true that the Gestalt laws of form are some of themobvious, and most of them old, and a few of them accepted by all
psychologists—a paradox that old principles should s^ not win

general acceptancel—we must nevertheless not lose si^t of thefact that the accepted theory of the fundamental nature of per-ceived form has been greatly altered in the last fifty years. In thattime we have passed from the discussion of patterns of elements
to the formulation of the dynamic structure of perceptual fields,a radical chSnge in emphasis which has been wrought entirely

by Gestalt psy^ology.

NOTES

257

Notes
1772, 112j cf. E. Mach, Principles ofRetinal Image

Physical Optics, bans. 1025, 46.

G. B. Porta wrote (1S40-161S)

Magiae mtmalis in four short books
In

1558, but his discussion of theWilliam Molyneux, the friend ofJohn Locke, wrote A Treatise of
Dioptricis, 1692, In which see Props.

principle of what we call the camera

84, 40, 42, etc., for the identification

obscure (projection through a smallof the “optlck angle” with “the ap-

hole into a dark chamber) and his

parent magnitude,^ and pp. 105 f. topointing out the analogy to the eye

the problem

isIn£e second edition, enlarged

into twenty short books, 1591, Bk. 17,

which Is De cntoptrlcis Imaglnibus;
or Eng. bans.. Natural Magic, 1658,
Bk. 17, Of sbange glasses. In themeantime F. Maurmycus ( 14941575) had published Phottsme de
kimHie, 1575 (see esp. Bk. 3 of the

69-80, on the eye), Eng.

1611

of the retinal image.

George Berkeley, An Essay towards
a New Theory of Vision, 1700, considered the problem of magnitude insects. 52-87 and the probkm of theinverted retinal image in sects. 88121. Johannes Muller discussed theimage

retinaJ

HandhuchinderPhyslologie des Uenschen, 1888,

Bk. V, sect. 1, Chap. 3, Ft.

II,

1.

bans,, 1940, esp. 105-121, In which

he recognized the crystalline humor
as a lens, but regarded it still as theseat of ^sual sensation and not as
forming an image on the retina. He

Singleness of Vision and the

Horopterthought the function of the retina was

On the anatomical explanation of
the sin^eness of binocular vision in

nublUve.

terms of the scmi-decussatlon of theJohaim Kepler's book Is Ad vUelllmem paraUpomena, 1604, and thechief reference to this matter la Chap.

optic fibers at the chiasma, see Clau-

De modo vislonls, 158-221. For

Newton, Opticks, 1704, query 15j D.
Hartley, Obseniaflons on Man, 1749,l, prop. S9j W, H. Wollaston, On

5,

Kepler’s proof that an image in acamera absoum would be the shapeof the object imaged and not of thehole, see p. SO. The argument about
the mechanism of vision is eztendedin Kepler's second book, Dioptrice,
1611.

B.

Descartes’s

discussionofthe optics and anatomy of vision isin his ta dloptrlque, 1637, Chaps. 3,

De usudius Galen (a.d. 129-199),

parHum librl XVII, X, Chap. 12i I.

thesemi-decussation

nerves, Phil.

231;

j.

Trans.,

Miiller,

of

the

1824,

Beitriige

optie

I,

222-

mr ver-glelclmden Physiologie des Geslchtstones, 1826, 71-164. On the othertheories, see the general discussion by
H. L. F. v. Helmholtz, Handhuim

5, 6 and 7; see esp. Chap. 5, entitled

der physiohgischen Optik, III, 1866,

Des images qul se forment sur lefond de 1 oelL See also his L'homme,
1662 (De homlne, 1664), the latter
half of Ft. 3, The story that C.

end of sect. 31 (in the Eng. bans.,
m, pp. 482 f.). Helmholtz cites F. }.

1625 produced
images with a bull’s eye before Descartes performed the experiment is
atbibuted to G. Sohott, Magic uniScheinerinoersaUs, 1657, Pt.

visible1, 87,[n.v.].

byHistory of Discoveries
Relating to Vision, Eight and Colours,

J.'

Priestley,Gall as well as Porta as holding the

An ex-

theory of alternating vision.

cellent earlier summary of theories isthat of Muller, Handmch der Fhpsi-

dlogie des Menschegs, 1838,V., sect,

I,

II,

Bk,

Chap. 3, R. 4.

On the horopter, see F. Agullonius,
OpHcofum librl sex,

1813,

II,

148-

150; G. U. A. Vieth, Debar die Richt-

AREAL VISUAL SPACE PERCEPTION

258

ung der Augen, Ann. Fhys. Leipzig,

tlie head normally erect and the lines

235-238:of regaid of die two eyes parallel and1818, 233-255,

58,

esp.

Muller, Geiichtssinn, lfe8,

!oc.

cit.

and Plate I; alao Muller, Handbueh,
he, cU. For an historical note, see
Ilelmholb, he. elt. For the generalform of the horopter, see Helmholtz,
op, eit,. III, sect 31 (in the Engtrans, pp. 421-482); E. Heiing,
Beittage mr Fhysmlogie, 1861-1864,
most of which ii about identicalpoints and the hoiopter. Helmholtz,
Eng. trans III, 484, has a long noteon now Hering and he independently
woikcd out the form of the horopter.
Fig. 28 IS plotted from Hehnhmtz’s
graph of the curve developed. L. T.
,

Troland’s similar figure, Ftinelples ofFsyehophjsiohgy, 1929,
wrong,

I,

343,

is

In geneial, see H. A. Can, An Intfoductum to Space Peieeption, 1935,
159-194.

More shictly^ealdng the piimary position is denned ns die position for which Listings law holds, i.e., the position fromwhich the eye moves widiout torsion.
in a horizontal plane.

If the eye is in the primary position

when it fixates a cross, then me projected

negative after-image of thecross will not rotate when the eye is

moved.
For Helmholtz’s discussion of these
two laws, see his Handbueh derphyshhgischen Opiik, 111, 1866,
sect 27 (also 3 ed. and Eng. bans.).
For hmitadons of the laws and deviations from diem, see
von Kries’ noteJ.
to this sect. 27 in the 3 ed. (andEng. bans.). For Ilerings discussionof Listing’s law, see his Beitrage ziir248-286. Fora general ^scussion of the laws andPhi/slolosle, 1864, csp.

ihe experimental means of their verification, see E. B. Titoliener,

Eye-Movement

Experi-mental Psychology, I, ii, 1001, 246Frohlems of eye-movemont aro die

252,

On Lolze and local signs, soe thecentral theme of Muller’s monograph,next secdon.

op, oU,, 1826.

For the pilnciple of Donders' law.
De bewegungon
van het menscheh]k oog, Ned. Lancet,
see F. C. Donders,

Nativism and Empiricism

2 set., 2, 1846, 104-138; Ecitrag zur

den Bewegungen desmenscldlchen Auges, Holliind. Bettr.

Lehre vonmat,physlal. Wise,,

1,

1846, 105-is

For diis 19th-centnry topic therea largo and unfruitful literature.

Excellent summaries
Blbot,

145.

of

it

are;

T.

German Fsychohgy

B. Listing's law, see theof ToDay, bans. 1886, 68-133, 0. Kiilpe,

contemporaries

Outlines of Psychology, bans. 1895,

always gave for it; C. G. T. Heute,
Lehrbuch der Opthalmalgie, 2 ed..

343-351, 368-873; V. Henri, Ueber
die Baumwahmehmungen des Tastshmes, 1898, 182-214; W. Wundt,
GrundzBge der phushloglschen Psychobgle, 6 ed., II, 1910, 517-529,
702-738; J. v. Krl®, in Helmholtz’s

For

f.

reference

that

his

1863, 37. The statement sometimes
cited in 1 ed., 1847, 14, is not explicit,

calls

whereas the 1853 reference

the principle Listing’s law but

ives no reference to Listing.

Hehn-foltz says. Physiological OpUce, Eng.
trans..

Ill,

1925, 121, fhat Listing

Physiological Optics, 3 ed., Ill, bans.

1925,

607-625. 635-652.

referenceisthe fullest

The

last

and most

never published the law; so diat mustsopbisdeated. These discussions in-be why Heute waS always cited for it
primary position, which may be de-boduce more theorists than does thepesent text; e.g., J. F. Herbart, T.
Lipps and J. Ward.

fined as me position of the eyes wii

The history begins in experimental

Listing s law should hold only for theNOTES
psycholaw wdth Johannes MuDer,
Zur MT^khenden Fhyslohgle desGesichtsslmes, 1826, 39-67, which

Hamilton's Philosophy, 1865 or later

Muller’s first introduction o{ the con-

Chap. 13.
Helmholtz discussed these theories in relation to monocular space
pweeption in his Physiological Op-

cept of specific energies and that he

tics,

is

nativistic in

Insists

thatthe sense thatit ismind can perceive

the

ed..

III,

[1866]. trans.

1925,

sect.

For

28, esp, pp. 154-168, 228-232.

abject. For Muller’s use of the views

Helmholtz s contention tliat the geometrical axioms are not intuitive andoi the philosophers (including Kant)

innate but learned in experience, seea theory of space, see his Hand-

the three articles of 1866, 1863 andbttch der Physlologte des Menschen,

1878, reprinted in his Wissenschaft-

1838, Bk.

lidte

only the retinal image and not thein

8. sect. 1, Chap. 2 (Vol.
2, pp. 1346-1351 of the Eng. trans.).
E. H. Weber infiuenced Lotze.
Weber, in his Der Tastsinn und dasGemeingefiihl, H. Wagner's HandwSrterbuch der Fkysimogie, III, ii,
1846, 524-543, discussed cutaneous—

famous experiments on the discrimination of
two points ^under the heading of
the "Ortsinn,” and sought to explain
spatialperception

his—

Aahandlnngen, II, 1883, 610-

660.

Wundt’s final summary of his theory of space perception (1910) has
been cited above. 'The theory devel-

oped through all six editions of the
Physiologische Psijoliologie, One getsits

beginnings inhisVorlesungeniiher die Menschen- itnd Thierseele,

1863, 1, Lect. 15-17; witlr which cf.
2 ed,, 1892, Lecls. 9, 10 (or Eng.

discrimination by a theory of sensorytrans. of 2 ed., 1894).

(pp, 527-529), the nationthat the nerve-fibers, leading to dif-in his Beiirllge

ferent spots on the skin, make of the

only part ever published has the sub-skin a mosaic of sensitive regions,title;

andE. Hering’s nativisttc slant appears

circleszw Physklogie (theZut Lelire

vom Ortsinne dertliatspatialdiscrimination oc-

Netzhaut), 1861-64. In this his gen-curs only

when

differenteral discussion ol theory occurs

and therefore

different“circles,”fibers,arestimulated. Cf. pp. 475-477.

R. Lotze's theory of local signs was
essentially a theory

which endowed

the men cited in the text are as follows.

C,

Stumpf,Ueber den psy-

and applied

Vrsprung der SaumooTstmung, 1873, an important bookw^ aswhicli helped get its author the chaireach sensory circle with a conscious
localizing (diaracteristicon

pp. 323-329 (1864).
The other important references forthe principle to the retina as

chologischen

Wurzburg; W. James, The Prin18M, H, 145-

to the eye. See his Medkinische Fsij-atcholagle, 1852, 325-371; and, for aciples of Psychology,

summary, Ribot, op. ait, 88-95.
Although the British empiricists
naturally provided a background forchologie, 1893, sects. 57, 61 (or Eng.

the empiricistic theories of spatialof Psychology, 1910, 303-306,

do not come directly into lliis controversy. For an
example of the way in whidi they338.

sought to derive the conception cn

reported in 1890 to the III Inter-space from the perception of timenational Congress of Psychology atand motion, and of the discussion as
to whether extension must be given

ion without inversion of the retinal

intuitively in the first place if space

image, Psychol, Reo., 4, 1897, 841-

perception,

is

they

presently to be built up, see j. S.

Mill, An Examination of Sir Wluiamnb; 0. Kiilpe, Grandriss der Psytrans.); E, B. 'Titohener,

A Text-BoSc
335-

G, M. Stratton's experiment on the
inversion of the visual field was first

Munich, but the main paper is Vis-360,

463^81. The modern repeti-tion of the experiment is F. H. Ewert,

m

AREAL VISUAL SPACE PERCEPTION

A study of the effect of Inverted

ungen,

retinal stunulatian upon spatially co-ibid.,
1856-1857, 47-55i
1360-1861, 26-37, [n,v,]. The otherordinated behavior, Genet. Psychol.
Monogr., 7, 1930, 177-303,of the effect of interruption of extent

On adjustment to a visual fieldore E, Heiing, EettrUge xur Physi-

by prismatic wedges, seeplogie, 1, 1861, 66-69i A, Kundt, Un-distorted

M, Wooster, Certain factors in thedevelopment of new spatial coordination, Psychol, Monogf,, 32, 1923,

early discussions

and measurements

teisuchuDgen uber Augenmaass undAnn, Phys.
Chem., 196, 1863, 118-168; H. Au-

optische Tfiuschungen,no, 4s J. J, Gibson, Adaptation, aftei-

beit, Fhystologie der Natzhout, 1S65,^eot and contrast in the perception

284-267; H, Helmholtz, Hasidbwdi
der physhloglschen OpHk, HI, 1866,

of curved lines, J.
1-31,

loss,

exp. Psychol., 10,W, Wundt mentioned

the straightening (in a few days orhours) or straight lines perceived as

crooked because of experimentallyinduced optical clianges or because,in metamorphopsia, of the actual
shifting of the retinal elements
Grundxbge der physialogischen Psyi

eholcele, 5 ed„ 11, 1902, 512-514,

He

159 f, lEng, trans,. III, 192 f,],W, Wundt’s first mention of theoverestimation of the vertical withrespect to the horizontal

Beitrpge

xur

is

ii.

his

der Sinneswahmehmunp [1859] 1862, 158163, HelmhoUz discussed diis matter
Theortein ioc, rfit.

The

rderences to the six
in the text

early

described his own case of metamor-

classical illusions listed

phopsia which arose out of his cho-are as follows:roiditis.

(1) J, C, Poggendorff called Z5I1ne^s attention to the illusion diat

There is a related experiment onreversed auditory localization: P, T.

bears his name, so see ZOllner, op,with

dt. infra. E, Burmester, Boltrag zur

Auditory

Young,

localization

acoustical transposition of the ears,J.

exp, Psychol, 11, 1928, 399-429,

axperlmentellun

Psychol,350,

llluBionsdorff,^stematic

secondaryA

CourseExperimental Psychology, 1898,
B,
Tltwener,
E,
Experi212-260i
sources are E, C, Sanford,inmental Psychology, I, 1901, pt, i,
151-170, pt il, 303-3281 W, Wundt,Die

geometrisch-optlschenCl,,(also separate),

gives his24,355-394,esp,

See also A, H, Pierce, Studies

and Visual Space Per-ception, 1901, 242-278,(2) F, ZOlhier's figure in his Ueber
eine neue Art von Pseudoskopie undHire Beziehungen zu den von Plateau

und Oppel beschrieben Bewegungsphtlnomenen, Ann, Phys, Chem., 186,
1860,

500-525, The original

illu-

Ges,

Wise,,

sion has the thick lines, as shown in

1898,

53-178Fig, 31, which has the advantage ofof course,

being double: both white on blackand black on white. It is generally

schungen, Ahh, sSchs.
math,-phys.

Tfiu-

1696,

12,

in Auditory

best

geo-

named the illusion for Poggen-

Geometrical Optical

The

Bestimmung

metrisch-optiscfaer Tfiuschungon, Z,

Wundt,

own theoryi Sanford andTltchener discuss others'.

For B, Lotze’s early discussion of
the sensory illusions, see his Medi-drawn nowadays with thin lines,
black on white. See also Fierce, op,dt.,

279-314,cinische Psychologie, 1852, 435-452,(3) E, Herlng first published the

Oppel's pioneer articles are

bowed parallels in his BettrSge zur

J.

J,

Ueber geometrisoh-optische Tfiusohungen, Jher. phys. Ver, FronfcM,
1854-1855. 37-47, [n,v,]i Nachleee
Olden geometrlsch-aptiEchenTausch-

Physiolode,I,

1861, 74,

(4) Wundt’s anabgous figure of
the fiaring parallels was based on anolder figure of Pisco’s and was used

NOTES
by Wimdt in bis lectures. It was first

261

W. Einthoven, Eine

1898, 88-105;

published by A. Thidry, Uebei geo-

einfachemetrisch-optische Tauschungen, f ML

fiirphysiologische

Erklfirung

geometriseh-op-

versohiedene

Stud., 12, 1896, 74, and then Wundt

tischepublished it himself in his Die geo-

Physiol, 71,

metiisch-optische Tauschungen, op,

F. Schumann, Beitrfige zur Analyseder1898, 117.

tit.,

(5) For Helmholtz’s squares, see

Tiluschungen,

And),

get.

1898, 1-43, esp. 2f.;

Gesichtswarhnwmungen,Z.

241-291,esp.

Psychol,

SO,

1902,

286-290.

loc. tit.

(6) For F. C. MuUer-Lyer’s fa-

mous arrows, see his Opti^e Urtheilstauschungen.

Arch,

Dynamical Gestalten

thystol,

though brief, figures fifteen variant
forms of the illusian and offers the

For further orientation on the confiict between elementism and phenomenology, see E, G. Boring, A

principle of "confiuxion” in ezplana-History of Experintental F^cbomgp,

Suppl. Bd., 1889, 283-^70, which,account is

1929; on elementism, 324, ^8, 377-

Ueber Kontrast und Konfiuxion,

879, 423 f., 572, 575-578; on phe-

PsyM, 9, 1898, l-16i 10, 1898,
421-431. The illusion was analyzed

nomenology, 3OT-359, 367 f., 401,
572 f., 575 f., 579.

tion, Mtiller-Lyer’s fuller

his

Z.

miantitativoly

QuantitativebyG.
Heymans,
Untersuchimgen fiberdas "optiscbe Faiadoxon,’^ ibid., 9,
1896, 221-256,

An excellent discussion of theseOn the school of Gestaltqualitat,
see Boring, op.

tit.,

433-440, 448-

450. The important papers are citedin the notes of Chap. 1 (p. 47).

various theories of the Mfiller-Lyer

The early work in experimental
phenomenology is: F. Sidiumann,^paradox” is given in E. B. Titchener,

Beltritge zur

Experiments Psychology,

wahrnehmungen,

I,

1901,

Analyse der GesichtsZ.

Psychol,

23,

Ft U, 321-828. The original sources

1900, 1-32; 24, 1900, 1-33; 80, 1902,

in chranological order are: Mfiller-

241-201, 321-339; 36, 1904, 161185; E. R. Jaensch, Zur Analyse derLyer, op. tit., 1889, esp, 286 f.; loco,
titt,,

1896;

W. Liska, Ueber einige

OTtlsche UrtheilstSuschungen,Ar^

nystol., 1890, 326-328; F. Brentano, Ueber ein optisches Faradoxon,
Z. Psychol, 3, 1892, 349-358; 6.
1893, 61-ffi; T. Lipps, Optische
Streitfragen, ibid., 3, 1892, 493-504,
esp. 498-504; Batimaesthetthmdgeometrlsch-optlsche

TSuschungett,

1897, 234-258; J, Delboeuf, Sur eine
nouvelle illusion d’optique,fleo.

Gesichtswahmehmungen, Z. Psychol,
Ergbd. 4. 1909; Ueber die Wahmehmung des Baumes, ibid,, Ergbd. 6,
1911; D. Eatz, Die Erscheinungsweisen der Fatben undihre Beeinflussung dumb die individuelle Erfahrung, ibid., Ergbd. 7, 1911; K.
Rubin, Synsoplevede Figurer, 1915,
German bans, as VisueU wahrgenom-

mene Figuren, 1921.

scL

Paris, 3 ser., 51, 1893, 237-241; C.
Brunot, Les filuslons d'optique, ibid.,

Gestalt Psychology

Auerbach,

EBhler’s diSicult prolegomenon is

Erklfim^ der Brentano’schen optlBchen llusohuM, Z. Psychol, 7,W. Kfihler, Die phy^chen Gestalten

1894, 152-160; cf. Heymans, op. tit.,

1920. It has never been banslated,but a little of it has been abstracted
in English by G. W. Hartmann, Gestalt Psychology, 1935, 31-50, andW. D. Ellis, A Source Book of Gestalt

52,

1893,

210-212; F.

1898, esp. 248-252; A. Thib^, Ueber
geometrisch-optische

Tauschungen,

PhiL Stud., 12, 1896, 67-125, esp,
67-102; W. Wundt, Die geometrischoptischen Tiluschungen, op. tit.

in Rube und im statUmiren Zustond,

Psychology, 1938, 17-54. Ilto only

AREAL VISUAL SPACE PERCEPTION

262

complete systematic treatise that the
Gestalt psycliologisls have publishedconstancyprinciple);

K.

Hering,Gestalt

GrundzUge der Lchre oom Lichtstnn,
11905] 1920, If., 0-12, on objects
and memory colors; D. Katz, Die

The secondary sources are numerous. The best of these are Hart-

Erscheinungsweisen der Farben, Z.
Psychol, Erjgbd. 7, 1911, 214-228;

mann, op. cit, and W. D. Ellis, op.
dt,, where thirty-four of the important German documents have been

R. H. Tboul^s, Phenomenal regres-

K. Kofika, Principles
Tsychohgy, 1935.

isabstractedin

English.

of

A splendid

French summary is P. Guillaume, La
pstjchohg^e de la format 1937. See
also

Boring,A Hlsiortj of Experi-mental Psychology, 1920, 571-580,
591-593.
The text has based its summary
upon Kelson’s 114 laws; H, Kelson, The fundamental propositions ofGestalt

psychology,

Pst/chol.

Reu.,

1933. 13-32, q.v. for 24 basic
rrferences by 18 authors.

40.

On transposition, see W, Kohler,
Die Farhe der Sehdinge helm
Schimpnnsen und beira Ilausliuhn,
Z. Psychol, 77, 1017, 348-255;
Nachweis einfacher Strukturfunktionen beUn Schimpansen und beim
Haushuhn, Abh, preuss. Akad. Wiss.,
pbys.-math. Kl, 1918, 1-101; andthe abstract of die latter in W. D.
ElUs, op. Git, 217-227.

On

the constancy phenomenon,
H. Helmholtz, Handbuch derphysiologischen
Optik,
sect.
24(1860) on contrast, sect. 20 (1806)on nature of object-perception (seeesp. Eng. trans., Ill, 287, which issee

in sect. 24, for a stotement of the

sion

the

to

real

object,Brit.

/.

Psychol,

21, 1931, 830-859; 22,
1831, l-30j E. Brunswik (with B. E.

Holaday, K. Eissler and S. Klimpfinger), Untersuchungen liber Wamnehmungsgegenst^nde, Arch. ges.
Psychol, 88, 1033, 377-628. The
best discussion of the literature of
the constancy phenomenon is K.

KoRka, Principles of Gestalt

Psy-chologu, 1935, 211-264. The historyof brightness constancy is dealt withbriefly

by R. B. MacLeod,perimental

investigationofAn exbright-

ness constancy. Arch. Psychol N. Y,,

1932, No. 135, 5-18; M. A. Sheehan,

A study of individual consistency inphenomenal constancy, ibid., 1038,
No. 222, 14-10. Bnmswik's views
are described by H. Ansbachor, Perception of number os affoctod by themonetary value of the objects, ibid.,
1987, No. 215, 5-25.
Recently the problem of visualshape, and tlius of the optical iUusions, has been brought into relationtodie Held theory of Gestalt

W. D. Orbison, Shapea function of die vector-field,
Amer. J. Psychol, 52, 1939, 81-45,
j^ycliology;
as

809.

Chapter 8

VISUAL PERCEPTION OF DEPTH AND DISTANCE

B

erkeley, having said m 1709 that “the estimate we makeof the distance of objects amidembly remote is rather an
act of judgment grounded on experience than on sense,”

went on to argue that the distance of near objects may be perceived by the sensations that arise when the eyes, in looking at anear object, are brought nearer together (convergence), or when

an approaching object is kept from being confused by the effort
or straining of the eyes.

Thus Berkeley represented the funda-

mental view that prevailed for two centuries after him. It was
the notion that the convergence and accommodation of the eyesfurnish primary sensory data, basic to the immediate perceptionof distance, and that the devices which the painter uses, like per-spective and shadow and interposition—all of which work for one

eye and at great distances—are only secondary judgmental criteria

which a person learns by experience to employ in his estimate of
distance. Because representative drawing and painting are older

than psychophysiology, these ‘secondary

criteria’

gained atten-

tion before the ‘primaiy’ mechanisms. By the nineteenth century,

however, convergence and accommodation had come to he re-garded as the two important factors, to which Wheatstone presently added a third when with the stereoscope he brought retinal
disparity into prominence as another fundamental means of per-ceiving depths. In the present century the pendulum has started
to swing back; the classical ‘secondary criteria’ are now being re-garded as the primary dynamic medianisms in visual perception
with convergence and accommodation as auxiliary processes. In
this chapter

we shall consider aU these principles and mechanisms

in the order in which they became important.

Secondary Criteria of Distance
It was in

the nineteenth century that the founding of experi-mental psychology upon British empiricism led to the acceptance263

VISUAL SPACE PERCEPTION IN DEPTH

264•

by psychologists of the view that perception, the knowledge ofthe external world, is based upon experience and judgment. On

the basis of experience the mind makes a judgment as to the na-—

ture of the external world^that

was the view implicit in mostof the thought about perception. Helmholtz’s doctrine of unconscious inference ( 1866) was put forth because these judgments are

immediate and the judgmental process is not detectable in consciousness. Thus it came about &at the sensory data which form

the basis of a perception seemed to function as criteria of judg-

ment. In the perception of distance, therefore, the sensory data of
convergence, accommodation

and retinal disparity came to be

regarded as ‘primary criteria.’ This term criterion persisted longafter theimmediacy of perception had been admitted and thedoctrine of unconscious inference rejected. Like its equivalent cue,
it is stillused somewhat anachronistically today.

It is for the most part the secondary criteria thatcan be em-

ployed to give the perception of distance in drawings and paintings. Thus the history of toe knowledge about them turns out to be

the history of knowledge about the use of certain techniques inart. It is art if

a man can draw what he sees, putting a three-dimensional world into two. It is science if ho knows the principles
involved in the success of his drawing as a representation of reality.
1.

Superposition. Near objects may partially obscure far objects;

the converse is never true. Hence the mind ‘seizes’—if we may use

toe empiricistio modes of speaking—upon the interruption erf one
object at toe boundaries of another as a criterion of toe relative
distance of toe two objects. The interrupted object is farther away.

The circumstances attending toe recognition of this principle arelost in antiquity. It is used in some of the most primitive drawings,

and early art which knew no perspective observes this rule, perhaps largely for toe need of getting objects close together while
avoiding the confusion of drawing parts of different objects in thesame place. Although the principle is too obvious ordinarily to receive special mention as an artistic technic, it eventually got into

toe lists of secondary criteria for the perception of distance, as,for example, Helmholtz's in 1866.
2. Size and perspective. The simple rule of perspective is: toeremote is smaller than the near, Hence relative size may be a

SECONDARY CRITERIA

265

criterion of distance, and continuous change in size in accordancewith certain laws is perspective,
If a drawing or painting is to be realistically representative of

the natural world, it must be fashioned in accordance with theselaws. Realism is, however, sometimes ignored and sometimes evencondemned by art; thus the absence of a competent perspectivefrom ancient pictures may mean tiiat exact representation was notdesired. It is said that Agatharoos, who painted soeneiy for theplays of Aesohylos in the fifth century b,c., wrote a treatise on perspective which greatly impressed Anaxagoras, but thelostbook isand there is no evidence as to whether its principles werepracticed. Certainly the Romans used perspective; paintings on

the walls of Pompeii ( destroyed 79 a.d. ) are excellent examples of
itsuse. It was the naturalistic movement in Italian art, however,that brought about the formal recognition of the laws as we know

them today. Although several famous painters contributed to thisdevelopment in art, the two most important names seem to be
Paolo Uccello ( 1397-1475 ), who has been called “the first scientificexponent of perspective,” and Piero deUa Francesca

(ca.

1418-

1492), who carried the geometrical analysis of the principles muchfurther and Invented, it would seem, the vanishing point. Before

that time mistakes in perspective were made even hy great painters like Fra Angelico, who, according to one measurement, repre-

sented Christ as putting water into St. John’s mouth with his handseven feet away. The principles once thoroughly known, there

were no longer gross errors, though the artist might choose, ofcourse, to avoid the realistic representation of a third dimension.

The geometry of perspective, in that it approximately duplicates the retinal image, is an adequate basis for the perception of

the third dimension. In actual experience, however, perspective is

modified by other factors, as we shall see later when we come to
discuss the problems of size and distance (pp. 288-299).
3.

Light and shade. It cannot be a large step from the ability

correctly to represent the lights

and shadows of nature to theknowledge that the representation of light and shade gives depth
to the perception of the picture.

Hence the ‘discovery’ of thiscriterion of the third visual dimension, like the discovery of inter-

position,islost in antiquity,although much primitive

art,

not

seeking to be realistic, contented itself with flat outline drawing.

VISUAL SPACE PERCEPTION IN DEPTH

266

One can, nevertheless, assess the growing importance of this itemof knowledge from the manuscript notes of that great geniuspainter, anatomist, architect, engineer, scientist, observer of na-—^Leonardo da Vinci (1452-1519), who soughtture

to organize

the use of light and shade in a set of principles for painting. Whatcame to be called his Trattato deHa Pittura includes “six books”
on the use of light and shadow, a discussion which is classical in
the naturalistic movement in art. To speed the progress of naturalism, balked in its effort to get the third dimension of nature on

two-dimensional canvas, Leonardo was developing the technics of
securing depth by light and shade, as well as by perspective. Later

we shall see his admission of naturalism’s defeat in the impossibility of painting a picture that resembles nature as seen in binocular vision (pp. 283 f,).

The scientific interest in the problem of relief came later. Rittenhouse noted in 1786 that a low relief or matrix may reverse
its

depth and appear like a raised relief or palrix, the concave

turning to convex. After the discovery of stereoscopic depth(1833) interest in these reversible reliefs was increased. Sclirbder(1858) showed tltat a reversal of a matrix is very easy with afamiliar object like a human head or an animal which is always

experienced as convex outward, never concave, Oppel (1855),with an ingenious instrument which he called an anaglyloscope,

showed that the perception depends, not upon the real directionof the light, but upon its perceived direction.

light

A matrix with thecoming from some known direction is perceived correctly

as a matrix because of the disposition of light and shade. In the

anaglyptoscope the light, perceived as coming, say, from the right,
is interrupted, without the observer’s

isknowledge, by a screen andreflected upon the matrix from the left by a mirror, thus re-versing the disposition of light and shade. What the observer perceives is not a reversal of the direction of the light but a reversalof the relief, a patrix instead of a matrix.
4. Aerial perspective.

Like the other painters’ criteria, aerial

perspective has probably been recognized for a long time byaitista

who could and would copy nature. The term (“prospettiva

aerea*) was proposed by Leonardo, who discussed the principle
at great len^. “Thereiscall aerial perspective,”

he wrote in his notes, "because by the

another kind of perspective which I

atmosphere we are able to distinguish the variations in distanceSECONDARY CRITERIA

267

of different buildings which appear placed on a single line; as,for instance, when we see several buildings beyond a wall, all ofwhich, as they appear above the top of the wall, look of the same
size, while you wish to represent them in a picture as more remote

one than another and to give the effect of a somewhat dense atmosphere.

.

.

.

Hence you must make the nearest building above

the wall of its real color, but make the more distant ones lessdefined and bluer. ... If one k to be five times as distant, makeit five times bluer.”

Berkeley appealed to aerial perspective to explain the moon
illusion. Ever since Ptolemy the accepted explanation of this illu-

sion has been that the moon looks farther

away at the horizon

than in culmination, so that, since it always subtends the sameangle, it also looks larger on the horizon. A far object that subtends

the same angle as a near object must be larger than the near object.

Berkeley, on the other hand, had this novel reason to offer

for the changed distance of the moon: the atmosphere is hazy,and the haze is greater toward the horizon because there is more
air tolook through; hence the horizon moon seems larger. One

further argument for this view as against others was that the moonon the horizon varies somewhat in size, and similarly the haze inthe atmosphere also varies in amount. One variation might explain the other. Euler, the mathematician, supported Berkeleys

view, but there were not many others. To Ptolemy’s theory of tiie

moon’s size we turn next.
5.

Filled and empty dktance. The principle that a filled distancelooks longer than an empty distance is one of the oldest to havereceived formal recognition as a perceptual law, for it was theprinciple that Ptolemy (ca. 150 Am.)

employed to explain themoon fllusion. The distance to fire horizon seems greater than the
distances up to the vault of the heavens because it is filled with objects.

Hence the moon on the horizon seems farther away and,

consequently, larger. It is this explanation which was fixed upon

the ancients. Helniholtz named almost a dozen distinguished scientists from Alhaz®n (d.

1039) to Malebranohe (d. 1715) who held

the view, which seems likewise cunent among astronomers today.
6.

Fartdkx of movement. Helmholtz noted that the movementof the head may resolve a confused visual field into depth.

Hewrote; “Suppose, for instance, that a person is standing in a thickwoods, whereitisimpossible for him to distinguish, except

268

VISUAL SPACE PERCEPTION IN DEPTH

vaguely and roughly, in the mass of foliage and branches

allaround him what belongs to one tree and what to another, or how
far apart the separate trees are, etc. But the moment he begins tomove forward, everything disentangles itself, and immediately hegets an apperception of the material contents of the woods andtheir relations to each other in space, just as if he were looking at agood stereoscopic view of it.” lius he described the way in which
the parallax of movement yields a depth which is quite as striking

and compulsory as the depth provided by stereoscopy. The phe-nomenon is familiar in the view from a moving train or vehicle, andmore recently in the moving pictures when the camera has been
moved continuously while fte photographing was in progress.
Because no parallax is possible in a picture, it is not to the painters that one would go for mention of this criterion. Leonardo, ofcourse, may have been aware of this principle, in that it shows oneof the ways in which paintings inevitably must fail to represent
nature, but he seems to have left no record of such knowledge.

Although Helmholtz’s contemporaries spoke of the principle asobvious, in general the older optical texts fail to mention it, either

because it was not recognized, or perhaps because it was too obvious.
7. Reoersible perspective.

Wheatstone remarked that the geo-

metrical solids which are usuaEy shown in outline in the eleventh

book of Euclid are often seen to reverse themselves, the near becoming far and the far near. Thus it is possible that the phenomenon

reversible perspective has been known to geometers eversince Euohd’s time. The first person, however, to call attention to

the fact in print and as a scientific observation seems to have been

the Swiss naturalist, Necker,

who in 1832 wrote a letter to Sir

David Brewster in England describing this “optical phenomenon
which occurs on viewing a crystal or a geometrical solid.” Necker
illustrated his point with a drawing of a rhomboid resting on oneedge (Fig, S7A), but in later years the figure has generally beendrawn as a cube (Fig. 37B). Necker noted that, although the reversal of the figure may seem fortuitous, the change can be controlled by fixing the regard onor N, for the corner fixated isM

generally seen as nearer to the observer and thus determines theperspective seen. As a matter of fact, Necker’s original rhomboid

reversed more easily than the cube, for the rhomboid stands
upon an edge and is prejudiced for neither perspective, whereasisREVERSIBLE PERSPECTIVE
die cube is seen more easily flat upon the ground {M near) than in
the alternative peculiar uptilted position ( N near )Interest in tiie problems of the visual perception of depth was

greatly increased by the invention of the stereoscope. Schrdder, in

11i
Fic. 37. REVERSIBI.E Pehsfective:

Fixatian of

Nscxer's Rhomboid (1832) and Cobb

M gives one pei^ectlvei fixation of N gives the levetse. The

rhomboid A was the original figure. The cube B is more easily seen with

M near.
his study of visual relief(18S8) which we have already men-tioned, presented the stair figure of Fig. 38. Drawing this figure

with shading as if the light were coming from above, he seems tohave found diat the most usual result is for one figure to be seen as
steps,and the other as the under-side of some step-lilce broken

masonry. It is apparent, however, that the light and shadows are
not the essential factors, for the two figures can be seen simultane-A

B

Fia S8. Hbvebsible Persfegtive: Schroder's Stairs (1858)
Schrader drew these Hgures with shading so diat the light (Indicated by
the arrow) could be considered as a determinant o£ the perspective. The
stairs are seen either from above, or from their under-side. Direction ofillumination is, however, less important than other factors like fixation (cf.
Fig. 37}and ^is figure is usualty reproduced without the shading.

VISUAL SPACE PERCEPTION IN DEPTH

270

ously in the same perspective, either as stairs or the reverse, and"Schroder’s stairs” have usually been reproduced without theshading.

In 1860 Sinsteden noticed that a windmill, seen obliquely anddarldy silhouetted against the bright evening sky, kept reveming
its direction of rotation so that hecould not teU whether he wasseeing the mill from in back or infron(5This effect, which has since

been reproduced by projecting

on a screen the shadow of slowly
revolving motor-driven vanes, iseven more startling than the reversal of the static drawings. Fig.
39, the silhouette of a perspective

drawing of a real mill in Essex,
England, shows what Sinstedenmust have seen. The aims of themill rotate in the direction of theFensrccmvi:
Sinsteben's Whtomili, (1880)

arrow. This rotation is clockwise

Sinsteden drew no such explicit

server, that is to say, if the per-but (his is what he roust
have seen, a windmill silhouetted

spective is that of seeing the arms

When tn is per-from behind with the fourth atm

Fro. 39. Hevshsibijei

figure,against the sky.

if the arm

m

is

by

seen near the ob-

ceived as near, the observer sees

obscured

the left side of the plane of rota-

When the perspective reverses,

tion and thus the rotation is clockwise.

When m is perceived as far,then the other aide of the plane ofrotationisseen

and the rotation

becomes counterclockwise.

the

the

mill

house.

arm m is far from the ob-server, and the arms are seen as

from in front with the fourth arm
in front of the mill house but in-visible in the black silhouette; thus the rotation changes to coun-

terdookwise. The reversal shifts the observer from the left to theri^t side of the plane of rotation, and the effect is that of changing the direction of rotation, for in one instant the upper arms

move away from the observer, and in the next they are foundmoving toward him. Sinsteden found ffiat he could fix the direction of rotation by imagining himself on the one side of the millor the other, a discovery that is comparable to Oppel’s that relief is determined as a matrix or patrix according as

the light to come from one side or the other,

one believes

.

CONVERGENCE

271

There is not much history to the reversible perspective because
the fact was obvious and no one has been successful in offering
a plausible explanation of it Lange (1S88) and Marbe (1893),

both working in Wundt's laboratory, measured the rate of reversal

and sought to relate the phenomenon to the fluctuations of faintstimuli, and thus to the fluctuations of attention, but nothing cameof the idea. Recently the facts of perspective have been exhibited
as examples of the dynamic organization of a perceptual field, andto this matter we shall return later (pp. 209-303)

Convergence and Accommodation
The ‘piimaiy criteria’ of the perception of depth and distancecame, in the course of the nineteenth century, to be recognized as
three: (1) the convergence of the eyes, (2) the accommodation of

the eye’s focus, and (3) the retinal disparity that is due to binocular parallax.

Of these three principles, knowledge about con-vergence is the most ancient, whereas knowledge of retinal disparity is comparatively recent, being for the most part only of firelast one hundred years.
1. Convergence. The fact of the convergence of the two eyes
upon the object of regard was known to the ancients. Euclid

knew it, Indeed the principle could hardly be overlooked by anyone interested in the geometry of binocular vision, since the move-

ment of the eye to Took at’ an object is one of the most obvious
facts about vision. The significance of convergence, on the odier—sometimes

hand, was not apprehended so early

for the reason

that it was not certain the two eyes can function simultaneously,
for one theory of the singleness of binocular vision had been thatthe vision of one eye is suppressed in favor of vision by the other,with alteration of vision between the two,

The nature of convergence was, however, clear to Aguilonius,
who, as we have seen (pp. 220 f. ), invented and defined the horopter in 1618. Aguilonius thought of the horopter as a plane contain-

ing the point of fixation, so &at the distance of the plane from theobserver would depend upon the angle between the eyes. Descartes in 1637 described the eyes as feeling out a distance by theconvergence of their optic axes, just as a blind man might feel out adistance with two staves, one in each hand. He drew a picture of

the blind man. He assumed that a man, knowing the direction of

VISUAL SPACE PERCEPTION IN DEPTH

272

the regard of each eye, would, by a “natural geometry,” be able toappreciate the distance of the object regained.

Berkeley in 1709, accepting the fact of convergence as well established, noted that there remained still the question as to how

these movements of the eyes could convey the idea of distance tothe mind. To the solution of die problem he applied empiristic andassoeiationistio theoiy. "Wheneyes, according as

it

we look at a near object with both

approaches or recedes from us,” he wrote,“we alter the disposition of our eyes, by lessening or widening the
distance between the pupils. This disposition or turn of the eyes
is attended with a sensation, which seems to me to be that whichin this case brings the idea of greater or lesser distance into the

mind.

.

.

.

Not that there is any natural or necessary connexion

between the sensation we perceive by the turn of the eyes, and thegreater or lesser distance, But because the mind has by constantexperience found the different sensations corresponding to the different dispositions of the eyes, to be attended each with a different

degree of distance in the object: there has grown up an habitual or

customary connexion, between those two sorts of ideas." And hewent on to stress the role of experience in the association of these

two ideas and to discredit Descartes’ view that one perceives actually the angle of the eyes in order to apply a natural geometry inthe judgment of distance.

Through two full centuries of psychology this view of the function of convergence in the perception of distance persisted. It wasessentially theview of Helmholtz and Wundt and Titchener.

Titchener’s context theory of meaning implied it; the meaning ofa particular distance is given to the sensory visual core of theperception by the accrual to that core of the kinesthesis of theparticular convergence that the eyes assume. Berkeley’s theory ofvision was published in 1709, and Titchener’s context theory ofperception in 1909.
2.

^ommodation. So long as Galen’s view that the ‘caystalline’is the seat of visual sensation persisted, there couldof diebe no problem

change in the eye’s focal length; but as soon as Kepler(1604) had established the ‘crystalline’ as a lens and the retina as
tiae sensitive element, and had been confirmed by Scheiner ( 1625)

and Descartes (1637), who both showed that an extirpated eye
actually focuses an image on the retinal region, then the problem
arose. (See pp.

222 f.) Thanks to the knowledge of the

tele-

)

ACCOMMODATION

273

scope, the physics of optical systems was too well known for there
to be much doubt in the scientific mind that the eye would haveto change its focal length if it was to get on the retina clear imagesof objects at different distances. It was, in fact, not long after

Kepler fixed upon the retina as the organ of sensation that
Scheiner (1619) performed the experiment which has since beencalled by his name. Having prepared a card with two pinholes init,closer together than the diameter of the pupil, he viewed witha single eye through these holes two pins unequally distant.
Either pin, if fixated, he saw as single, because the lens super-

posed the two images on the retina when the focus was right; butthen the other pin, for which the focus was wrong, was seen as
double. The fact that the eye changes focal length was thus established.

Kepler had supposed that the focusing might be accomplishedby die hack-and-forth movement of the lens, but Descartes ( 1637
hit at once upon the correct idea, that it changes its curvatm-e.
About the function of accommodation in the peiception of distance, he was quite explicit, noting that accommodation is effectiveat short distances of three or four feet,whereas convergence iseffective at the long distances— 15 or 20 feet, he said in one place,

100 or 200 in another.

Berkeley ( 1709 ) argued for three lands of “ideas” as the cues tothe perception of distance. Besides the distance between the pupils

as
were,
—
—ate seen clearly and that near objects(convergence), he held that far objects^fitting,

itthe natural focus of the eyetend to be blurred; as a consequence, the idea of nearness becomesin experience connected with the idea of blurredness.

Althoughin this matter he was in error, since fat objects become blurredwith near fixation, the point led him to the observation that the“straining” of the eye will make an object in near vision less “con-fused.” This was in accoidance with the evidence of introspectionthat a strain is felt in near-accommodation.
It cannot be said that Kepler or Descartes

or Berkeley settled

the matter of accommodation as a cue to the perception of depth,
for the fact of accommodation remained in some doubt—in spiteof the existence of conclusive experiments like Schemer’s

the mechanism had been established—^untilby Helmholtz.’ A fact gets

set in the structure of science, not often by one line of direct evi-

dence, but generaUy by means of several converging lines along

274

VISUAL SPACE PERCEPTION IN DEPTH

with circumstantial evidence, If all one knows is that the laws of
optics require the eye, having dear vision at different distances, tobe able to accommodate, one may still doubt the fact of accommodationj but a person will not ^ubt it if he knows what is thenature of the mechanism of accommodation— or if he believes
that he knows.

There have been during the three centuries since Kepler altogether six theories about accommodation, their histories being toa large extent contemporaneous. Let us consider them, however,successively. The word accommodation seems to have been intro-

duced by C, A, Burow in 1841. Johannes Muller before him said
adaptation. The earlier writers used various descriptive phrases.

We speak always of accommodation here, adopting a verbal
anachronism for the sake of simplidty of expression,(a) There is no mechanism of accommodation.

The simplest

theory of accommodation is, of course, its denial, the contention
that die eye has a universal focus. This view de la Hire presented in
1685, He held that objects at one distance would be clearly focusedand the blurting of other images ignored in recognition. While de laHire, in view of Scheiner’s experiment, may seem to us to havebeen denying a demonstrable fact, we must remember that it wasthen known that the doubling of binocular images of objects lying
outside the horopter is generally ignored. In a very crude way, dela Hire was anticipating themodem constancy phenomenon, forhe believed that objects are perceived for what they are in spiteof the inadequacies of their nnmediate sensory excitation.

Much later the famous physiologist Magendie (1816) gave theweight of his authority to this view that the eye has a universal
focus. He claimed that the sharpness of the image on the soleroHoaof the extirpated eye of the white rabbit does not change with the
distance of the imaged object feom the eye, but Helmholtz re-marked later that the sclerotic coat of the eye is a very poor screen
on which to define a sharp image. Magendie believ^ that the
crystalline is not a lens but has other functions in the eye.

Finally, there was Treviranus, who published in 1828 quantitative data on the dimensions of the eyes of man and of many kindsof animals. He argued that, because it has many layers of differing

density froih the front to the back, the lens has a universal focus

and would act differently for objects at different distances, especially if the contraction of the pupil in near vision removes theTHEORIES OF ACCOMMODATION

275

outer portions of the lens from optical functioning. His was a complicated theory and never won support. Having measured so manyeyes so accurately, Treviranus was perhaps loath to admit too

much freedom of movement within the eye.
(b) The contraction of the pupil in near vision is the mech-anism of accommodation. The camera obscura with a pin-hole
aperture has a universal focus, and the larger the hole the lesssharp the image. That the eye is analogous to the camera obscurais the assumption of this second theory.

The lens is supposed to bepermanently adjusted for far vision, a fact which can seemingly

be recognized in the relaxed state of the eye with remote fixation.

The blurring in near vision would then be reduced by the contraction of the pupil Schemer’s experiment seems to disprove theassertion that pupillary contraction is the sole mechanism of ac-

commodation; nevertheless it was Scheiner himself who discovered that the pupil contracts in near vision, and who suggested thisfunction for &e contraction. He also believed that the lens moves
in accommodation, but the great physiologist Haller(1763)

held to the contraction theory alone. Various other writers sup-ported this view after Haller, the most important of them and thelatest being the Dutch physiologist, Donders, in 1846, ten years

before Helmholtz brought together the evidence that the lenschanges shape in accommodation. Helmholtz (1856) refuted thistheory by pointing out that accommodation is not noticeably impaired by &e use of an artificial pupil, a hole in front of die real
pupil and smaller than the smallest size of the real pupil.
(o)

The external eye-muscles elo'ngate the eye-ball in near vi-

sion. This theory was for several reasons a natural proposal The

external muscles are obvious; muscle fibers inside the eye were

unknown; and the familiar method of focusing a telescope wasby changing the length of its tube. The view was first put forth by
Sturm in 1697 and, according to Helmholtz, was supported by almost a score of others before Listing, who argued for it in Wagner’s Handworterbuch der Fhysiologie in 1853. For a century anda half it was the most widely held of the incorrect theories.

We have already seen (pp. 109 f.) that Thomas Young, whocame to a negative condusion.
Young turned his eye inward toward his nose, forcing the smoothin 1801 sought to test this view,

ring of a key between the eye-ball and the conjunctiva in such amanner that he could look over the bridge of his nose tbrou^ die

276

VISUAL SPACE PERCEPTION IN DEPTH

ring of the key, while the anterior surface of his eyo-ball was pre-vented from moving forward. Then he forced tlie ling of a small

key in behind the eye between the eye-ball and the bone. The resultant pressure led to dark images on the retina, and, since theseimages reached to the center of the field of vision, Young concluded that he actually did have his eye-ball firmly constrained.
Nevertheless he was able to altar his accommodation for near andfar. Helmholtz, always a champion of Young, described this paper

as “a work of astonishing perspicacity and originality, which was

qualified to settle the question as to accommodation even at thattime,” a paper which Listing and the others may have missed because, in Helmholtz’s phrase, “on account of its conciseness, it isoften hard to follow, and, moreover, it presupposes the most thor-

ough knowledge of mathematical optics.”(d) The curvature of the corriea changes in accommodation,
This view is closely related to the preceding one, since the emvature of the cornea can only be dhanged by action of the eye-muscles, and elongation of the eye-ball would bo likely to change

the curvature of the cornea in the right direction. Tliough tiro theory is said first to have been put forwaid by Lob6 in 1742, its mostelaborate support came from Homo in 1795. John Hunter had
been appointed to give the Croonian Lecture in 1794 and had

been intending to show tliat the lens changes shape in accommodation,

when he died. Home not only undertook topresent

Hunter's views for him as well as possible, but, when the next year

he was himself appointed Croonian Lectui-er, ho continued the
topic, arguing that theobserved change of curvature is in thecornea and not the lens. He reported observations performed byhimself with a microscope and confirmed by two colleagues, observations that showed the cornea bulging out in near fixation.

Others, however, failed later to confirm these experiments. Helmholtz was of the opinion that they were refuted by Thomas Young’s

demonstration that accommodationis

not noticeably impaired

when the eye is covered with water, since the refraction between
the cornea and water is very much less than the refraction between
the cornea and air.
(e) The lens shifts back and forth in accommodation. This is
the original theory, fhe one that Kepler proposed in 1611. Scheiner

seconded it in 1619, supposing that a forward shift of the lens innear vision is accompanied by pupillary contraction. Although

THEORIES OF ACCOMMODATION

277

Descartes presently introduced the view that the lens changes

shape and docs not move back and forth, many investigators continued to believe that Kepler had been right. Johannes Miiller in
his monograph on thecomparative physiology of vision (1826)

held to this view, as did Burow in an important text on physiological optics that he published in 1841. Undoubtedly the dieory persisted because there were insufiSdent grounds for a decision. One

important line of evidence is the relative movement, with changing accommodation, of the images reflected from the front andrear surfaces of the lens—Sanson’s images.

It is true that theseimages were described by Purkinje in 1823 and by Sanson in 1838;
nevertheless their true importance was not generally realized until

Helmholtz emphasized it in 1856. That the lens should change

position would seem simpler than that it should change shape; andscientists often hesitate to accept the less simple dieory until there
is strong evidence in its favor.

The lens changes shape in accommodation. We have seen(f)that Descartes originated this view and that John Hunter had been

intending, when he died, to support it in his Croonian Lecture in
1794, basing his argument on the structure of the lens. Thomas

Young’s investigation of the mechanism of the eye (1801) cameout; aswe have also noted, with this conclusion. Purkinje sup-ported the theory ( 1825), and Helmholtz championed the view sovigorously that the idea is sometimes said to be his. The most im-

portant evidence in its support is found in the behavior of theimages reflected from the surfaces of thelens.

These images

Purkinje described in 1823. Sanson, having used them in 1838 in
his method for the diagnosis of cataract, much later lent his nameto them. Both Purkinje and Sanson employed the reflection of acandle flame (Fig. 40), which by its shape shows when it is erect
or inverted. Cramer in 1851 improved the technique, using a lightthrough a tube to cast a pear-shaped image, which could be judged

both as to size and as to whether it was erect or inverted. Helmholtz

improved the technique furflier by using two separated

squares of light (Fig. 40), which, although they do not dearly indicate inversion, show the change of size by their altered separation. Helmholtz attributed the discovery of the images to Langen-beck in 1850 (missing Purkinje and Sanson, althou^ he cited
Sanson in other contexts), and discovered Cramer’s papers only
after he had independently discovered the images. Cramer was ex-

VISUAL SPACE PERCEPTION IN DEPTH

278

plidt in his argument for accommodation as a change in curvature of the lens, but it took Helmholtz’s authority to get the theory

accepted.

To observe these images (Fig. 40) the experimeirter must place
his eye so that he can see in the pupil of a subject the reflected

images of a candle flame or some otherlight.

As the subjectchanges his accommodation, the change in size and position of theimages is noted. The erect bright image at the left (in the figure)

SANSON’S
IMAGES

Fro. 40. Sanson’s(1838) ans IIixMiiom’s (1888) Images

The left flgore shows die reflecUons of a candle flame as Sanson loptoduced them. The rlglit llguies aie HehnJioitz’s leflccUons of a pair of illuminated squares foi far and near fixation a = erect reflection fiom cornea;==

erect i^ection front antoiior siuEaoe of lens; cinverted refleotionbfrom posterior surface of lens. In near fixation tlio images from botli surfaces of the lens are smaller because of gieater convexity of the lens, andnearer together.

from the cornea; the erect, lai^e faint image in the middle isfrom the front surface of the lens; the very small inverted faintisimage at the right is from the posterior surface of the lens, and isinverted because it is seen thiough the lens. The relative sizes ap-

pear better when the refiected object is the two squares of light at
tiie ri^t of Fig. 40.

The change of accommodation from far tonear makes the middle image decrease notably m size, since thesize of an image reflected from die convex surface of the lens is

proportional to the radius of curvature of the surface. The image

from the bi^ck of the lens gets a trifle smaller in near fixation,
showing that the posterior surface of the lens bulges a little in nearaccommodation, yet only a little as compared with the front surface. This experiment also shows that the cornea has its convexity

ACCOMMODATION VS. CONVERGENCE

279

increased slightly in near vision, but not enough to aoconnt for thefacts of normal accommodation.

Helmholtz’s only original contribution to what became the ac-

cepted theory of accommodation was to provide an explanation of
the means by which the lens can change shape. He suggested thatthe lens is elastic and under tension. By itself, consequently, it

would tend toward a spherical shape and thus toward near accommodation. It is, however, also under tension from the ciliary
process which, attached to the lens and also to the walls of the eyeball, transmits a puE that tends to flatten the lens for far accom-

modation. This is the resting position of the eye with two unfelt
antagonistic tensions. In near accommodation the muscular fibers
in the dliary process contract, with a sensation of effort, to release

the tension and allow the lens to bulge. It was the plausibility ofthis mechanism that went far toward winning assent to the direct

evidence of Sanson’s images.

Table I. Wundt’s Exfibiment on tub Pbucepiion of Distance(1859-1861)and monocular vision, in the

Just noticeable dlSetences, with binoculai

distance o£ a thread receding from or approaching the observer's eyes. All
figures in cm. The table abbreviates Wundt’s data Sightly.

Just noticeable diferences

Distanceof thread

Binooular visionfrom eyes

Approach Recession

50
80
100
110
ISO
180
200
3.

Monocular vision
Approach Recession

1

4.5

2

2

-

-

5
8

1

2
3

2

3.5

5

-

-

3

e.5

7
11

-

-

8
8

12

12

Relation of Accommodation and Convergence. Wundt was

the first person to submit to experimental measurement the functions of accommodation and convergence in the perception of dis-

tance. It was, in fact, thisproblem that constituted Wundt’s

maiden effort in experimental psychology in 1859-1861. The observer in his experiment, looking through a tube at a distant whitebackground, saw the field of view crossed by a suspended black
thread, which could be moved back and forth from as toward him

without eidier the upper or lower end becoming visible. The observer looked at the background and then at the thread, noting its
distance; immediately thereafter, while he turned his head to one

280

VISUAL SPACE PERCEPTION IN DEPTH

side, tie thread was moved either from or toward him; tlien finallythe observer, looking through the tube again,

first

at the back-ground and then at the dwead, judged whether it liad recededfrom him or approached him during the interval. The nature ofWundt’s results for both binocular and monocular vision is shownin Table I, where are given the just noticeable differences(

Unter-

soheldungsgrenzen) for approach and recession of the thread.

That convergence is more important than accommodation in
the perception of depth was Wundt’s conclusion, because the justnoticeable differences for binocular vision were so much smsJler

than the ones for monocular vision. Wundt also noted that thethresholds for recession were much larger than the thresholds forapproach in monocular vision, although in binocular' vision there

was no difference. This obsei-vation led him to conclude tliat the
subject can make more accurate discrimination in innervating themuscles of accommodation than he can in relaxing them, a viewthat was the beginning of Wundt’s belief in the existence of sensations of innervation. In fact, this difference in the

monocular

thresholds led him to suppose that accommodation fimclions not
at aU in recession, but that the judgments in recession are based

upon the diminution in the apparent size of tlio thread,
These somewhat meager experimental results remained unchallenged until 1894 when Hillebrand, a protdgd of I-Iering’s, criticized them and published the results of a new investigation. Hille-

brand eliminated the effect of the apparent size of the perceptual
object by using a line that had no breaddi, die sharply out edgeof a cardboard screen which, in front of the remote background,filled half of the field of vision. For sudden changes of distance thescreen on one side covdd be removed and another screen on theother side and at a different distance immediately introduced. For

gradual changes a single screen could be moved slowly along thevisual axis. In order to eliminate the double images that mightprovide cues when both eyes see the field, Hillebrand worked withmonocular vision only. He argued diat convergence is so related
to accommodation that the eyes converge even when one of themissmeened from the perceptual object.
Hillebrand was unable to obtain thresholds with gradualchange. The observers could not tell which way the screen was

being moved. He concluded, therefore, that accommodation (andtherefor! also convergence, as he argued) does not mediate theACCOMMODATION VS. CONVERGENCE

281

perception of distance. When the change of distance was abrupt,

he obtained large thresholds due, he thought, to the dispersion
circles that occur

with faulty accommodation and their dimina-tion by trial and error,

Table II. BArao’s Expebiment on the Pebception op Distance (1903)
Just noticeable dlSeiences, with binocular and uionocular vision and withabrupt and gradual change. In the distance of a line of no thickness recedingfrom or approaching the observer’s eyes. Tire j.n.d. ate in percentages of thestandard distance from the eyes, wMch is given in cm. Av.
average of 4
observers with normal vision. B== one observer with very slow acoommoda-

tion.

Standard

Just noticeable di'Serences in per centdistance

BinocuJar

Monocularfrom

Abrupt
App.
flao.

Ahupt

Monocular
Gradual
App.
Rea,

App.

Rec,

Av.

1,8

1.9

8.7

13.4

fi

2.1

2.5

12,8

47.0

Av.

1.7

2.0

8.7

15.5

B

1.S

1.5

10.8

22.0

40.0

Av.

1.8

1.7

9.7

17.4

25
30
24
41
25

B

1.9

2.5

8.5

25.0

51

50.0

Av.

1.7

1.6

9.3

14.4

B

1.4

2.0

5,4

35.0

Av.

2.0

1.8

10.6

14.5

B

2.1

1.9

8.8

16.2

26
53
24
64

eijes

28.e
33.3

60.7

51

206
49
105
46
83
36
77
29
142-1-• The range of the apparatus, 95 cm., was not great enough to measure this|.n.d.

There was some controversy. Arrer repeated Wundt’s experi-

ment and defended him. Hillebrand replied. Then in 1903 Baird
conducted a thorough investigation of the whole matter. Although
he used Hillebrand’s form of apparatus, he followed Wundt in

employing both binocular and monocular vision. His results appear in Table 11 as the items labeled “Av.” It is clear that thethresholds for binocular vision are much smaller than for monocular vision, also that there is no difference in the thresholds forapproach and for recession in binocular vision, but that the thresholds for recession are much greater in monocular vision than thethresholds for approach. Thus Baird concluded that convergencefurnishes the most important cue to the perception of distance.

Hillebvand’s notion that the doubling of images might furnish thebasis of the judgment he rejected for the reason that dSuble images

are not specific as to direction. Since he was able to obtain thresh-olds with gradual movement of the screen— although they were

282

VISUAL SPACE PERCEPTION IN DEPTH

naturally much larger than the thresholds got with abrupt move-

ment—he decided that accommodation plays a secondary role
which becomes significant in monocular vision. Abrupt change always favors comparison. The fact that the limens of approach were
lessthan the limens of recession in monocular vision seemed tomean that innervation of the mechanism of accommodation is abetter cue to change of distance than is relaxation, and that wasessentially Wundt’s view.

By a lucky accident Baird had one observer, B, who could accommodate his eyes only very slowly. His thresholds are given
separately in Table II. It will be seen that in monocular vision they
are nearly always larger than the thresholds for the other observers, and that in the case of recession they are always larger,

In binocular vision, on the other hand, there is no significant difference between B and the other observers. Thus it appears thatfaulty accommodation increases the dillerence between monocular and binocular perception of distance, thus reenforcing the arg-

ument that accommodation normally furnishes m monocular vision a cue for distance. The slow accommodation of B also showed,
against HiUebrand, that convergence can occur and function accurately in advance of accommodation.

Stereoscopy
The two eyes, being separated in the head by a distance between 60 and 70 mm. and having their lines of sight converging

upon the fixated object, see slightly different views of the object.
Although this binocular parallax furnishes a cue to the perception of depth, very little was made of it before Wheatstone’s inspiration,

about 1833, that the consequent disparity in the two

retinal images can be a reason for the perception of depth. Before

Wheatstone the fact of binocular parallax was recognized, and it

was known that parallax must give disparate retinal images. The
theory of corresponding points, however, required that such disparity should mean a doubling or confusion in the perception.

Since the perception of doubling is not identical with die perception of depth, the matter remained for a long time an unexploredpuzzle, with' the possible explanation that the doubling is ignored

and that depth comes into perception in other ways.
Euclid noted the fact that a single eye sees less than half aBINOCULAH PARALLAX

288

sphere, since liie tangents forming the angle that subtends thesphere are not tangent at opposite ends oi a diameter, He also

noted that, if the sphere is smaller than the distance between theeyes, the two eyes together may see more than a hemisphere. With

the sphere, of course, the problem of disparity between the two

Fro. 41. Leonaiujo’s Pabadox (ante 1519)

The eye at A sees the background PD, and the eye at B the backgroundGEi hence both eyes see all the background and the opaque object C Is
transparent to binocular vision. Hence a painting cannot reproduce accurately what is apparent to binocular vision. This drawing was made by
L. B. Alberti in uie publication of Leonardo’s notes in 1651.

images does not arise. Galen (ca. 175 a.d.), on the other hand,described the differences in the perception of a column, with theleft eye,with theright,

and with both. He seemed, however,chiefly interested in the fact that more features of an object can beseen with two eyes than with either eye alone.

Among his manuscripts Leonardo da Vinci (d. 1519) left a noteon the transparency of objects. “If nature is seen witfi two ^es, it

wiE be impossible to imitate it upon a picture so as to appear withdie same relief, though the Enes, the li^ts, shades and color be

VISUAL SPACE PERCEPTION IN DEPTH

284

perfectly imitated.”

He presented a sketch like tliat of Fig. 41,

showing that the sphere "C becomes as it were transparent according to die definition of transparent bodies, behind which nothingis hidden.”

The eye at A sees the background PD, the eye at B seesG£, and PD + GE includes the whole of the background. Wheatstone remarked that, if Leonardo had used a cube instead of asphere, he would have become aware of the fact of retinal disparity. Brewster,

on the other hand, insisted that Leonardo, ex-cellent observer that he was, must as a matter of course have beenaware of the disparity of the images. The fact would seem to bethat,even if Leonardo noted the necessaiy disparity of the two

images, he might not have been interested in them. His interest
lay in the accurate reproduction of the appearance of nature inpainting. He was aheady noting the paradox that opaque objects

may also be transparent to binocular regard. It would not havehelped naturalism in art to observe that what should have been a
confused superposition of two disparate imagesisin reality aclearly outlined solid image, although it would indeed have beenan achievement in phenomenological observation.

On the other hand, Aguilonius in 1613 noted the problem, but
missed die implication &at it could lead to an understanding of
the perception of depth. It was natural that the inventor of die

horopter should be puzzled as to why solid objects, which cannot,of course, lie completely within the line of the horopter, should

He wondered“how it happens that bodies seen by both eyes are not all con-nevertheless appear neither confused nor double.

fused and slmpeless, though we view them with optical axes fixed

on the bodies themselves.

.

.

.

Since the images in each eye are

dissimilar, the representation of the object must appeal' confusedand disturbed to the primary sense.

.

.

.”

Aguilonius then went

on to say that what is "truly wonderful” is that objects actually are“seen clearly and distinedy with both eyes when the optic axes areconverged upon them.” How, he asked, is this contradiction explained? By the action of “the common sense.” "Whatever body.

.

.

each eye sees with the eyes conjoined, the common sense

makes a single notion, not composed of die two which belong toeach eye, but belonging and accommodated to the imaginative
faculty to v^hich the common sense assigns

it.”

Aguilonius ap-

pealed to the common sense as we today would appeal to meaning, saying perhaps that what is confused in sensation is neverthe-STEBEOSCOPY

285

less clear in perceptual meaning. But he did not make the last step.

He explained disparity away, without realizing that it is disparity
which under the constitution of the organism becomes perceived
depth.

The men who in the first part of the eighteenth century wrote on—menphysiological optics—

like Robert Smith and Porterfielddis-cussed the visual disparities due to binocular parallax, yet without
discovering that disparity yields depth. Thus it would seem that

Fro. 42.

Wheatstowi^s Stebeoscoh! (1838)

The panels EE' bear the disparate drawings which are reflected by the
mirrors AA', one into each eye as the observer faces the stereoscope.

Ad-justments are made by sliding EE' in the uprights DD', and changing the
distance between DD'and AA°witb the screw p.

thisnotion may be original wiih Joseph Harris, who said in his

Treatise of Opticks in 1775; “And by the parallax on account of

the distance betwixt our eyes,

we can distinguish besides thefront, part of the two sides of a near object, not thicker tiian thesaid distance; and this gives a visible reliew to such objects, whichhelps greatly to raise or detach them from the plane, on which theylie:

Thus, tiie nose on a face, is the more remarkably raised, by

our seeing each side of it at once."

We may say, then, that the fact of stereoscopic vision was readyto be discoveredand established. Wheatstone seized upon dis-parity as an essential condition of the perception of depth. For allthat he never knew why disparate images should yield a sin^eVISUAL SPACE PERCEPTION IN DEPTH

286

clear perception in three dimensions, he nonetheless realized thatthey do. He proved his point, moreover, by inventing what hecalled a stereoscope (Fig. 42), a device in which two mirrors, A

and A', reflect respectively to the eyes the disparate drawings on
So striking is Ae resulting syntlietic percep-

the slides E andtion of depth that it is no wonder the phenomenon commanded

attention after Wheatstone had published his complete description of it in 1838.

The date of <iscovery is generally said to be

1833, for it was then that Mayo included in his fhysiology a very
brief mention of the phenomenon, but it was not until five years
later that the facts received tlie notice that they deserved.

Wheatstone’s discovery was remarkable for two reasons. In thefirstplace, it isolated one criterion of depth

from all the others

and showed that it could be exceedingly effective alone. Without
the aid of convergence or accommodation or any of the ‘secondary
criteria’ for lire

perceptual dif-ferentiation

depth,

ofsimplegeometrical figures, perceived in

the stereoscope, stood oirt witli

immutable insistence, often witha dimension of depth that ex-

ceeded their horizontal and vertical dimensions. In the second

place, the stereoscopic experi-

Refractino
Stereoscope (1849)

Fio. 43. Brewster'sThetioiilar^form of Sir David Brew-

prismsIn 1843 Brewster de-ment was convincing because it
was synthetic. It was not necessary to iirfer disparity of images

binocular

andparallax,

Men to wonder how the drspar-

the principle, and in 1849 ity of images from a unitary obmanufactured this stereoscope, whi* igct could
give the perception'
came into generaluse in the early
.
» t
“
‘
Ota unitary object. In the stereo-

smbed

5

scope the disparity was actually
given in the drawings selected for use, and the nature of the perceived depth could always be predicted from the nature of thedisparities chosen.

Once the principle of the stereoscope was recognized, it became
possible to apply it in various ways, and to construct instruments
in a variety of forms. Sir David Brewster, having in 1843 outlined

the principle of a refracting stereoscope which uses lenticular)

STEREOSCOPY

287

prisms, proceeded to construct one in 1849, In the 1850’s many ofthese stereoscopes were built and sold in England and France forthe edification of the pubhc (Fig. 43). Still other optical systems

were proposed. In 1856 Brewster was able to describe eleven different kinds. The hand stereoscope with the hood (Fig. 44), an

accessoryoftheVictorian

was invented by theparlor,physician-author-poet,

OliverWendell Holmes, in 1861. The—daguer—for

use of photography

and oalotypes

reotypesmaking stereograms also be-came common in the ISSO’s.
In

1852

Wheatstonede-Fig. 44. Hand Stbbzoscofe ( 1861

scribed a refracting pseudoscope, an instrument with an

This type of stereoscope wltlt the
firstdesigned by Oliver

hood was

Wendell Holmes.
optical system that reverses thepaiallaa, as if the left eye were placed to the right of the righteye, With drawings or photograms the pseudoscopio effect is got

simply by reversing the stereograms, left for right. The refracting
pseudoscope, however, makes it possible to reverse even simple
objects,

convex for concave. Now it became apparent that thestereoscopic effect occurs only when other cues to space do notinterfere.

Stereograms with perspective cues in than may notreverse pseudoscopically, nor is it possible with a pseudoscope toturn a living human face concave.

In 1857 Helmholtz described the telestereoscope, an instrumentin which the eyes see a view with the parallax of two mirrors set
far apart.

A telestereoscope used at the window may thus resolvea landscape into depth. Helmholtz also built a telestereoscope

combined with a double telescope, so that distant objects could
be magnified at the same time &at the binocular parallax is increased for them.

Wheatstone regarded his discovery as a direct challenge to thetheory of corresponding points, the basic theory that accounts for
singleness of vision with the two eyes. Btiicke suggested almost

immediately (1841) that a solid object is perceived with a horopter that shifts as the eyes explore the object. The object is not, hethought, seen solid at the first instant, but only as the eyes con-verge first upon this part and then upon tiiat The parts of the ob-

VISUAL SPACE PERCEPTION IN DEPTH

288

ject lying outside the instantaneous horopter are not seen double

because they are ignored. Dove, however, exploded this plausible
theory by showing that a steieogram can be perceived as a solid
objectwhen illuminated instantaneously by an oleclric spark.

Such an iBumination, which lasts less than a mlUiontli oi a second,
does not allow time for the eyes to move at all.

Panum in 1858 took Dove’s finding to mean that space is nativeand not generated (as Lotze had argued in 1852) by eye-movements. He introduced the notion of corresponding sensory
circles, based on Weber’s conception of sensory circles on the skin.

Weber held that double stimulation within a cutaneous sensory
circle would be perceived as single; Panum held that similar contours falling within conesponding sensory circles on the two retinas would be perceived as single. From tills point he went on to

discuss the "sensations of binocular parallax” tliat could give riseto the peiception of depth, being mostly concerned with getting

away from empiricism and eye-movements lo nativism and a nonkinesthetic visual space,

Hering’s nativistic theory of visual space was influenced greatly

by Panum. Hering, it will be remembered(p. 29),—a sign

every retinal point to have thi'ee local signs

supposedfor depth inaddition to those for the veitioal and horizontal dimensions. Thusitwould be possible for images in the two retinas to be disparate

in respect of die local signs for deptli, and yet otherwise identical.

This line of theorizing, however, has led nowhere, except insofar
as it can be argued that Gestalt psychology takes its nativism irom

Hering. To its view that the perception of depth deponds upon theorganization of phenomenal data we shall return presendy (pp,299-303).

Size and DistanceAs an object recedes from an observer its retinal image diminishes in proportion to its distance from the observer. In perception,

however, the object appears to lose size much less rapidly, or it

may even be "perceived" as constant in size. Thus the Gestalt psychologists, being anxious to call attention to the fact that size in theperception is not solely dependent upon the size of the retinal

image, have called

this relationship,

not without exaggeration,"size constancy,” a special case of the "constancy(of. pp. 254r'256).

phenomenon”

APPARENT SIZE

289

The history of this phenomenon is more a history of tie clarification of concepts than a history of empirical discovery,

We must,therefore, first clarify the concepts in order to understand the his-

tory afterward.

There are three different kinds of size to be considered. Thisdistinction was made quite clearly by Hering, the phenomenologist, in 1879, although the modern terminology,

which follows,

does not exactly repeat his phrasing:1.

Visual angle or retinal size, the size of the image upon theretina, therefore physiological size or the size of the proximal

stimulus;2.

Phenomenal size or apparent size, the size of the sensory

datum in perception;
3.

Estimated size, the size as partially determined by judgment,
inference, past experience, or other processes inclusive of

more than the proximal stimulus.
It is easy to distinguish retinal shse from the other two conceptions,but not easy to state the difference between phenomenal size andestimated size. Helmholtz ( 1866), recognizing tliat perception de-pends upon past experience as well as present stimulus and thatits

form is what might be expected in an inference as to the natureof a constant object, held that perception depends upon an in-stantaneous unconscious inference {unhewusster ScMuss). Since

an inference is ostensibly a conscious process and can therefore
be neither unconscious nor immediate, this view was rejected as
self-contradictory. The ultimate reason, however, for rejecting un-conscious inference was the belief of the schools of both Heringand Wundt in the existence of immediate experience. The business of the experimental psychology of the late nineteenth cen-tury was, essentially, the determination of the relation between thestimulus and the phenomenal experience—in this case between thevisual angle and the Sehgrosse, as Hering called it. In those days

everyone believed that, since phenomenal experience is not theresult of inference, apparent size and estimated size must, therefore, be different. In the present century the Gestalt psychologists

find a distinction between these two concepts at a different level.

No longer insistent that phenomenal data are meaningless and notinterpretative, they hold that the perception neverflieless depends

upon the operation of psychophysiological dynamical forces which
determine size and other diaracteristios. These forces are not de-VISUAL SPACE PERCEPTION IN DEPTH

290

rived from past experience, they believe, but arise out of the native constitution of the organism.

They think, consequently, of

phenomenal size as dependent upon some process in the brain
which is isomorphic with the perception as to size. Estimated size

would also depend upon a neural process, since inference musthave a neural basis, but the genesis and form of the brain process

would be difiei-ent. It thus becomes plain that the distinction between apparent size and estimated size is still quite speculative, as
it

was when the issue existed between Hering and Helmholtz.

Granting that some of this history still lies in the future, let us now
turn to the past.
Ifanyone ever seemed to establish firmly the equivalence ofvisual angle to apparent size, it was Euclid, for in his Optica hedealt with the problem of size in just such a geometrical way.

Naturally, then, he could point out that the nearer of equal mag-nitudes appears larger; but he also modified his strict geometry bynoting that equal magnitudes at unequal distances do not appear
in sizes inversely proportional to their distances. Thus it appears
that, in moments of phenomenological insight, the distinction be-

tween apparent size and visual angle goes back to the very beginning.

In the eighteenth century there arose what came much later tobe called the alley problem. If one looks down the vista of an
avenue of trees, the two rows of trees, actually parallel, appear to
approach each other in the distance. Bouguer (ante 1758)

dis-cussed this problem at length. Porterfield in 1759 held that thephenomenon is due to the progressive underestimation of more
and more remote distances. He assumed that, if the angle between
a pair of trees on the two sides of the avenue diminished with theperceived distance, then the rows of trees would be seen as parallel; if, however, the distance is underestimated, then the angle be-

tween the pair seems too small for its apparent distance (sinceactually it belongs to a greater distance). Thus the rows of trees

appear to converge. Priestley considered the problem further in
1772, pointing out that no philosopher had yet discovered how thetrees of the avenue could be spaced so as to appear parallel andwithout convergence when viewed from a predetermined point at

one end. If the' el^teenth century had had railroads, the fact thatapparent size follows neither a law of constancy nor of visual
angle would have been even more apparent toitsscientists.

SIZE AND DISTANCE

291

Railroad tracks converge in the distance, but their separation does

not diminish at the rale at which distance increases.

As happens so often in science, in the nineteenth century incompatible views existed contemporaneously. The size of the retinal image was regarded as the primary determinant of perceived
size, with the optical illusions special cases requiring special ex-

planations. This view,which worked well enough in bidimen-

sional vision, where distance is constant, failed for changing dis-stance because it overemphasized visual angle as the determinantof apparent size. The sophisticates who considered size in relation

to distance all knew that proportionality of perceived size to retinal size does not occur exactly; nevertheless it took the defiiute

campaign of Gestalt psychology to make this incompatibility clear
to all.

In 1842 H. Meyer observed that wall-paper patterns with repetitive designs can be viewed with different degrees of convergence.

The eyes can be converged enough so that they combine adjacentfigures in the pattern, or even more, so that figures next but one or

next but two are combined. In such cases the figure is seen at the
point upon which the eyes are converged—nearer, and, since it
still subtends thesame visual angle, smaller. The greater the con-vergence, the neater and smaller the figure. Ludwig, the physiologist, made theconverse observation in 1852;

if

one fixates awindow, holding a pencil in the hand, and then shifts fixation to
the pencil, the window gets smaller. Presumably also the pencil
gets larger. Later Panum (1859) undertook to bring all these ob-servations together. He cited Meyer’s and Ludwig’s observations;

he noted that the image of a distant object, seen near on the screenof a camera ludda, appears much smaller than the abject itself inthe distance; he pointed out that the size of an after-image varies

with the distance of the ground upon which it is projected, thus
anticipating Emmert’s law.

That apparent size varies somehow

with perceived distance, even when retinal size remains constant,

was getting pretty clear.
Fechner and Hering also contributed to the discussion at thistime. Fechner (1860) held two compass points, with a certain

separation between them, a certain distance in front of his eyes.

Then, when he held another compass with twice* the separation

between its points at twice the distance away, he found that thesecond pair of points had to be brought doser to each other in292

VISUAL SPACE PEHCEPTION IN DEPTH

order to give the same apparent separation (Augenmm) as thefirst.

Horing (1861) observed the apparent size (Sc/jgrosse) of thewindow in his room as he paid attention to his own hand, held
near and in front of his face. When he moved his hand away fromhis face toward the window, the window got larger; and conversely. The implication is that the object attended to tends toremain constant although its distance changes, and that otlier objects, therefore, having a fixed relative size inthe visual pattern,

may vary. Because the retinal size of the hand gets smaller while
the retinal size of the window remains constant, the window relative to the hand gets larger as far as its retinal representation isconcerned. If the apparent size of the hand shrinks less than thecorresponding retinal image, then the whole field may remain proportioned in accordance with the relative retinal sizes; hence thewindow appears to get bigger because the hand does not appear toshrink as much as its retinal image.
It was not until 1881 that Emmert formulated that law of thegeometry of aftei'-images known by his name. If 0 is tlie linear sizeof an object, and d is its distance from the observer; and if

N is theD thelinear size of the after-image {NaohbUd} of the object, anddistance from the observer of the gi'ound of projection of tlie after-

image; then Emmert’s law states:

0:N::dtDIn other words, the apparent size of the after-image is directly
proportional to its apparent distance from die observer. This law,although it deals with the inconstancy of apparent size whenretinal size is constant, nevertheless does indirectly imply its con-verse, ‘size constancy.' The principle of size constancy asserts,

if

one stops to think it through, that apparent size remains constantwhen retinal size diminishes in direct proportion to the distance ofthe object from the observer, Emmert’s law states that apparent
size increases when retinal size remains constant in direct propor-

tion to the distance of the object from the observer. In other words,
if the distance isdoubled and the angle halved, the apparent size

remains the same, i.e. is doubled in proportion to the angle (sizeconstancy) ; and, if the distance is doubled and the angle constant,the apparent size is doubled, i.e. is doubled in proportion to theangle (Emmert’s law). If both size constancy and Emmert’s law

were exactly tme—

as they are not—it can bo shown that appar-

SIZE AND DISTANCE
ent size would always be

293

proportional to the product of theangle of the perceived object(See p. 310.)

visualby its distance from the observer,

The &st systematic experimentson this problem were made,not under Bering’s influence
as one might expect, but in

Re. 4S. SjzB CoKSTANox: Mabiivs’

Wundt’s

Expemment (1889)

The stmd^ stimuli were rods
100, SO and 20 cm. Ions, viewed at a
istenM of SO cm pie lines for Equivalent
Apparent Magnitude show theequivalentmagnitudes at distances of 300 and 875
on. That these lines
sue almost horizontal showsthat size remained practicallyconstant withchsmgmg ^tanoe. The dashed lines
show how the magnitude of the sHm-

qmred equal visual angles. These

data are for Martiua as ohscrw.

laboratoty by Martius in 1889. He

100 cm.

had wooden rods, 20, 50 andm length, which he suspended, one at a time, as standard
observer. Then at distances ofand 575 cm. he had the observer choose, underphysical procedure, a rod of length
sults for Martius himself

equal to the standard. The re-as observer are shown in Table III

Fig. 45. There is practically300

a definite psycho-

and inphenomenal constancy. The 20-cm.

VISUAL SPACE PERCEPTION IN DEPTH

294

rod at SO cm. was equated to a rod of 20.6 cm. at 300 cm. and to arod of 21.7 at 675 cm. If the observer had been equating visual
angles, these rods should have been 120 and 230 cm. long. Hencethe data seem to prove size constancy. But at once the question
arises as towhe&er there is a valid distinction between phe-nomenal size and estimated size. Might the more distant rods have
Tabi.1 hi. Mabtius’s Expebiaient on

Sbe Constancy (1889)

The data are for Martins as observer; the results from other observers are
similar.

Equhialent sizeStandard

As obseraed

Site
at

SO cm.

20 cm.
SO
100

at

SOO cm,at

20.8 cm.

S7S cm,If visual angle constantat 300 cm.

21.7 cm.

120 cm.

53.9

57.6

107.7

106.6

SOO
600

at

575 om,230 cm.
575
1150

appeared smaller, and the observer, with his knowledge of how
distance tends to diminish size, have been able to correct for thephenomenal change? Could he perhaps make tliis correction immediately? and how many seconds may elapse if the judgment isstill tobe called immediate? Questions of this sort Martius’s ex-

periment did not settle.
In 1902 Hillebrand, working under the influence of Hering, re-vived with his alley experiment the interest in the old problem of
the vista. He seated his observer at the end of a table, 4 m. long and

1 m. wide, covered by white paper with the axis prominently

marked down the middle. At the far end of the table the ends oftwo black threads were attached, equidistant from the axis andseparated by distances varying from 39 om. to 10 cm. The observer,

who held the other ends of the threads, was asked to adjust themlaterally until they appeared to be parallel. The results showed
what the eighteenth century philosophers also knew, that theflireads must diverge as they recede from the observer if they are

to appear parallel; they must diverge

enough to counteract thetendency of true parallels to appear to converge. Hfllebrand also

found that the divergence was greater for wider alleys than forsmaller, but that it never approached the divergence of lines whichgive a constant visual angle—^not within the limits with which heworked. Very narrow alleys approach the constant separation oftrue parallels, a result which might have been predicted, since a

ALLEY EXPEBIMENT

295

very small separation at the far end gives little chance for con-vergence at the near end,

Though the use of threads presupposes that apparently parallelsides of an alley should be straight, thatassumption is not neces-

Fic. 46. Size Constancy; HuiEBaAiro’s Ai.t.etExpehiment (1902)

AB = standard distance at 380 cm. from observer; it is here 39 cm,, or
19.5 cm. on each side of the median line. The observer, at S,
adjusts suspended threads to form two apparently parallel lines throng A and B,
AC, BDlooi of threads for apparent parallels. AE, BF
geometrical

=

=

=

AS, flS
locus of what parallels would be if visual angle had toremain equal for parallels to seem alw^ equidistant from each other. The
parallels.

figure at the left is

drawo to scale and shmvs the shape of the alley withsides that appear parallel. The figure at the right is the sameas the one at

the left, except that the horizontal scale is magnified to show

the curvatureof the alley's sides. These data are for Hiilebrand as observer.

saiily valid. Hiilebrand, therefore, repeated his

experiment withmany threads suspended vertically at each side to form the alley
walls. The separations between pairs of opposite threads couldbeadjusted, and the shape of the apparently parallelValls thus dis-covered. The results for Hiilebrand himself as observer are shownin Fig. 46. The diagram at the left is drawn to scale; it showstheVISUAL SPACE PERCEPTION IN DEPTH

296

true parallels drawn from the separation of 39 cm. at the far endof the alley, the visual angle tliat subtends 39 cm. at tho far end,

and the loci of the apparently parallel sides of the alley. The rightof the flgnre is the same as tho left except that tho scale for thebreadth of the alley has been increased ten-fold to show how thesides actually curve for apparently equal sepai'ations.

The
(

alley

experiment was repeated

later

by Poppelreuter

1911 ) with vertical rods fixed on simple bases, in such a way thatthey could be shoved in toward the median line or pulled out fromit tomake an actual vista. In general his results confirmed Hille-

brand’s; to appear as determining parallel vertical surfaces, thesurfaces formed by the rods are not parallel, nor do they converge

so much as the visual angle, nor are they planes. They are some-what curved, lying intermediately between the locus of the constant angle and the locus of the constant separation (parallels).

Blumenf eld ( 1913 ) sought to eliminate the visual frame of reference for these judgments—the room, the rectangular table. He ar-ranged tiny gas jets with faint blue flames that could be pushed inand out with respect to the median axis. The observer, in Uie dark
except for these flames, looked between the two rows, or in olhej

experiments looked somewhat down upon tho two rows, and ar-ranged the points of flame to form appai'ent parallels. Tho interesting thing about this experiment is that the loais of the apparent
parallels, although it lies intermediate between the locus of true

parallels and the locus of constant visual angle, is very much nearer

the constant visual angle than was the case for Hillcbrand or
Poppelreuter, In other words, this is, in Katz’s sense, a reduction

experiment. The perceptual cues are reduced in the dark morenearly to bare unassisted retinal size. It seems obvious that if allcues to distance could be removed and die points that determine

the alley perceived at entirely indeterminate distances, then visual
angle, the only remaining determinant of size, would control, andlines diverging from the observer to give a constant angle would

seem everywhere equidistant.

The recent history of this problem has been partly factual andpartly systematic. Let us turn to the factual contribution first.

That chimpanzees can pei'ceive objective size independently of
retinal size was demonstrated by Kohler in 1915. G6tz showed in

1926 that the same principle holds for chickens. He trained thechickens to take larger grains of com and to reject smaller, when

SIZE CONSTANCY

297

the linear sizes of the larger to the smaller grains had a ratio as

small as 1.1; 1.0; that is to say, the chickens were perceiving a dif-ference in size of 10 per cent. When the small grains were placed

only 15 cm. away from them and the large grains as much as 73

cm. away, the chickens still singled out the larger grains, choosing
in the larger object a visual angle that was about one-flfth the sizeof the visual angle for the smaller but nearer object. These results

have been interpreted as meaning that the chickens made thechoice on the basis of phenomenal size rather than estimated size,
yet that conclusion would be valid only if an estimate is an elaborate inferential process, which a chicken would not be likely toemploy. On the other hand, if by estimate is meant a practical

judgment of objects as things and not an ‘introspective’ judgmentof immediate experience, then the chickens were probably making‘estimates.’ It can be said (hat, in Helmholtz’s terms, an inference(Sdduss) was required of the chickens, and we may assume thatina chicken such an ‘inference’ would be unconscious {unbe-

uausst).

Beryl, publishing also in 1926, had adults and children equate

the sizes of boxes and also of disks at different distances, ranging

from 1 to 11 m. The adults showed almost exact constancy in tiieir
judgments of objective size, but the children exhibited a tendency
to need a larger remote object as a match for the smaller near object. For instance,children two years old matched a 7-cm. box at

1 m. to an 11-om. box at 11 m., whereas children six years old

showed a little more constancy, matching the 7-cm. box at 1 m., to9-cm. box at 11 m. Such results do not show size constancy, although of course they also do not come anywhere near constancy
of visual angle.

The experiment makes it seem, however, thatlearning or maturation has something to do with this approach

toward constancy.

Both Thouless (1932) and Sheehan (1938) have studied theoccurrence of individual differences inthis function.

Thoulessfound the degree of constancy to vary with training and with intelligence, and hence sometimes with age. Sheehan found that it

was dependent upon a number of objective and subjective factors.
The amount of visible details makes a difference, as does also thedeviation of the object from normal appearance. THe introductionof misleading contexts natmally works against constancy, just as

the deliberate use of cues to objective size works for it. Suggestion,

298

VISUAL SPACE PERCEPTION IN DEPTH

contrast and altitudinal sets all affect tlie function,

Such results

imply that the phenomenon is not a simple lesultaiit of a few physiological forces, but the resolution of acomplex process which,even though it be unconscious, is fully as involved as an estimate
or inference.

Holaday (1933), working under the stimulus of Brunswik in
Vienna, has produced the best general analysis of the conditions
that underlie this ‘constancy phenomenon.’The greatest con-stancy, he showed, is achieved by trying to achieve it; in short, theobserver does best when he takes an active objective attitude ofcommon sense, betting that one pair of differently distant objects
ismore nearly the same size than another pair. Such an attitude

works best when there are provided cues for its use. Holaday

found that constancy was more nearly achieved when cues to the
distances were provided by placing many objects in the inter-vening space, and conversely that the falsification of the impression of distance reduced constancy. Thus we come back essentiallyto Bishop Berkeley’s position { 1709 ) Ural the perception of the sizeofan object depends on the perception of tiro distance to theobject.

On the systematic side there have been two successive movements! the first, by the Gestalt psychologists, to show that size,

when distance varies, does not change with the visual angle but
tends to remain constant; the second, by Brunswik and others, toinventory and appraise the various forces which determine ap-

parent size at values intermediate between retinal size and theconstant size of an object.
Gestalt psychology, tikeallvigorous movements

—

^the

authormust be forgiven for his reiteration of this statement—began as aprotest against an established order in systematic psychology. In
this order, as

we have seen, there was imMded the prevailing no-tion that apparent size is determined by retinal size, a belief which

had persisted in spite of the fact that it was definitely known, as

we have also seen, not to be true when the distance of the stimulus
object varies. The Gestalt psychologists were determined to showthat there is no fixed relation between the stimulus and the perception, since the properties of the perception depend as much upon

the operation bf dynamical forces in the central nervous system as

upon the stimulus. If one has been thinking that apparent size
varies with visual angle and then suddenly notes that the man 10

SIZE CONSTANCY

299

feet away in the hall is not nearly twice so large as the man 20 feetaway (or if one merely chances upon Maitius’s experimental results), then one is struck by the fact that size is practically con-stant when distance changes—practically constant as comparedwith what would happen if size changed with visual angle. It was,therefore, a pardonable hyperbole for the Gestalt psychologists to

speak of “size constancy” as if the appearance of objects did notshrink with distance—this in spite of lie actual fact that apparent
size does usually diminish with increasing distance, althou^ muchless rapidly than the visual angle.

Thouless (1931) and Brunswik (1933) both gave formulas formeasuring this tendency away from the stimulus value and toward
constancy, Thouless spoke of the phenomenon as “regression to[toward] the real object.” Brunswik wrote about the transformation to the intermediate object {Zwischengegenstand). Both men

pictured the organism as correcting the immediate impression of
the stimulus in the direction of objective constancy and thus effecting a compromise between the two. Their formulas measured
tire weight of each component in the resultant.

As a matter of fact, Brunswik, with Holaday and his other associates, has changed themodem form of this problem. Brunswik

pictures the organism as trying to perceive objects which are only

more or less accessible to it; it bases its perception upon all thedata available. Apparent distance is thus, as Holaday showed, oneof the determinants of apparent size. With enough cues the Ztoisc/i-

engegenstand may approximate the real object, but the organ-

ism can neverthelesssatisfy its

own needs sufficiently without

fully achieving its intentions. This point of view, born in the func-

tionalism of Vienna, is so close to the functionalism of America, thepsychology that examines mental functions in respect of their use
to the organism, that it clarifies the problem of size and distanceto a great number of modern psychologists.

Tridimensional Dynamics
It is to Gestalt psychology that themodem psychologist turns

framework when he deals with perception.
Thus it is not surprising today to find depth and disfance regarded
for his systematic

simply as a dimension of a perception organized under dynamicallaws in a tridimensional field. There are really five points which

300

VISUAL SPACE PERCEPTION IN DEPTH

the Gestalt school, speaking here most explicitly with the voice ofKoffka, makes about the perception of the third dimension. They

are these.

(1) Visual perception is essentially tridimensional. It does notcopy the retinal image, not even to the extent of being, like theretinal image, bidimensional. Instead,tutes the stimulus-object;itapproximately reconsti-

and sthnulus-objects, like everythingelse in the material world, are solid. The tridimensionahty of thevisual field becomes especially obvious, however, in those cases

where a flat stimulus yields a solid perception, and Koffka has

ABC
Fie. 47.

Dynamics of the TmtaMENsioNAL Visual Field

The plane stimuli, A and B, yielding each a bidimensional visual form,
give, when added together in tlie plane stimulus C, a tridimensional visualform. It is piaotionlly irapossibla to perceive C as what it is, 12 linos lying
in the plane of the paper.

listed a number of these instances, (a) Fig. 47A is a fiat stimulus

whicli gives a flat perception. Fig 47B yields perception of fourlines in a plane. But, when the lines of these two figures are com-bined in Fig. 47C, solidity at once results. It is practically impossible to see the cube as twelve lines lying flat in a plane, (b)When

the lines a and o' in Fig, 48A alternate tachistoscopicaUy, the line

b being absent, one gets apparent movement of a line back andforth between positions a and o'. Then, if the line b is introduced
as a constant,ie fluctuating fine seems to pass under b between

oando'—to be forced out of the plane, as it were, (o) If the angles
aba and ah'a in Fig. 48B alternate tachistoscopicaUy, the perceived movement is the movement of an angle rotating in the third

dimension about the pivots aa. This is the simplest movement that
could bring the angle from position aba to position ab'a. (d) If

blue vanes of an episcotister whirl in front of a yellow disk on a
black background and one views a part of the field through a ‘reduction’ tube, then there is color mixture between the blue andTRIDIMENSIONAL DYNAMICS
the yellow;

if

301

the blue vanes are made the right size, one may

even see a gray. But without the tube one sees, not a mixture, but
the yellow through a transparent blue; both colors are seen in

the same direction at different distances, a case of what Koffka
has called “double representation.”

Here, of course, the stimulus is notflat,

but gives a flat perception when

the colors mix, and a perception of

depth when they do not,(2)

The second point is that such

excursions of the perception into thethird dimension are due to the op-

eration of dynamical principles oforganization exactly like the principles that operate in two-dimensional

space. The perception of the cube

tends toward symmetry (Koffka),

and thus tends to reconstitute the

Fro. 48. Dynamics of the Tbi-

DIMENSIONAI. VISUAL FlELD

A: Tachistoscopio alternaSon
and o' widrout b makes it
appear that a line moves backana forth between posittons aand e' in the plane cn a and s';
but with the Introduction of bof athe line appears to move out oftlic

object (Brunswik). Because move-

ment tends toward least action, theangles flop over in space instead ofplane behind b.

B: Tachistoscopic alternationof iiba and sh'a does not resultin the apparent movement of an

angle

between the two posisame plane, but intwisting around and moving up andtions in thedown, as they would have to do ifanthey remained in the plane. The line

angle out of the plane about

apparent

rotationofthethe pivots aa.

moves from one position to the otherthrough the plane when there is no hindrance, but, when a barrier
is introduced

between the two positions, it moves around the bar-rier and thus out of the plane.

When the blue-vaned episootisterand the yellow disk are seen entire, their integrity as objects localized at different distances prevails, and the yellow is seen throughthe blue and at a different distance. With the reduction tube toeliminate the object-character of the two things, however, the simplest event occurs: drey fuse. This sort of speculation about theforces which determine perceptual form is called fidd theory. The
field,

the matrix of perception, is obviously tridimensional,

andGestalt psychologists also infer a tridimensional neural process.

(3) Stereoscopic vision thus becomes simply a special case of
field theory, and the key to an understanding of it is the fact thatstereoscopic vision is a process of the formation of objects. If theleft eye views the stereogram

A in Fig. 49 and the right eye theVISUAL SPACE PERCEPTION IN DEPTH

302

stereogram B, then the combined field would be what is shown at

C with bb' double. One does not, however, ordinarily see bb'
double, but rather a single line a in front of a single line b. Thereis an attraction

between b and b', and they form a single line. Why

do they pull together? Because they are near? Yes. Because they
are both black? No. Koffka has dted Helmholtz’s observation thata black stereogram on a whiteground can combine to give
depth with a slightly disparate
white stereogram on a blacka b

ground. They pull together be-

B
49,

Fig.

Dvhamics or im! Tm-

cause in thatway they re-constitute a simple objective

DIMENSIONAL VISUAL FlELD

organization of two lines at

A; stereogiam for left eye. B; stereogram for rlglil eye. Ci superpositioncolor of the lines, but the fact

A and B, the way the hinocularthat they are lines, objects, thatofwould look if the law of coiresponding points were absolute. Actually b and b' attract each other, andone sees a single fine b farther away
field

dillerent distances. It is not the

makes the black line b combine with the black line b' instead of with die white groundthen a.

near b', a ground whi(i is in
the position corresponding to the position of b, but whidh is not

an object. Koffka has given examples of how these forces of combination operate in the binocular field, always in the interest of theformation of objects; it is, indeed, well known that the stereoscopic
constitution of genuine objects and scenes is much easier than the

combination of the geometrical skeletons of objects that are used
for experimental demonstrations,(4) Convergence and accommodation in this theory lose muchof their importance. They remain, of course, optical mechanisms

necessary for obtaining clear retinal images of objects, just as theretinal image is still basic to visual perception in spite of all thedepreciation it has received. Do convergence and accommodation,
then, not enter into the distance of field theory at all? Not much.

Schui has suggested that the shrinkage of the horizon moon as it
rises

toward the zenith might be due to the muscular effort ofelevating the eyes, but that is merely speculation. Although weknow that convergence (Meyer’s experiment)

altersperceived

distance and size, that result might come from the accompanying
alteration of retinal disparity. It is certainly true that these two

FIELD THEORY

303

mechanisms for the perception of distance have interested psychologists less in the 1930’s than in any one of the preceding ten

decades.
(5) Field theory is bolstered up by the theory of isomorphism.
Kohler’s axiom that “all experienced order in space is a true representation of a corresponding order in the underlying dynamical

context of physiological processes” and that there is an organization in a brain field corresponding to the organization of the per-ceptual field, has been extended to all three dimensions of perceptual space. If the perception of a closed figure means that
there is some kind of closed system of excitation in the brain, thenthe perception of a solid figure means that the excitation in thebrain must be extended into new dimensions. This theory, v?hichis still

speculative,isnot essential to field theory; yet there canbe no doubt that it has given great support to field theory in thatit—provides a concrete place^thebrain—where the field forces

can be supposed to operate.
In this matter of the dynamics of perception Brunswik has gonesomewhat beyond the Gestalt school. The Gestalt psychologists
seek the laws of object-formation ostensibly in the perceptual

by the implication of isomorphism—in the brain.
less physiological and more biological ap-

field, but also—

Brunswik, with aproach, ignores the brain and shows how the organism ‘tries’ toreconstitute the objects from thesomewhat insufficient sensory

information that it receives from them. The Gestalt theory is oneof dynamics; Branswik’s is one of functional use, a view which is,
in fact, a modem equivalent of unbewusster ScUim.

Notes
On the perception of the viiual
third dimension in general, see H. A.

handbook, the reader is referred tothese sources for most of what hap-

Carr, An Introduction to Space Fer-

pened in the present century.

ception, 1935, 159-288; R. S. Wood-worth,

Experimental

Fsijehoh^y,Secondary Criteria of1938, 651-680. Carr gives tlie more

orthodox presentation;

gives_fee modern view_in wHclTconmergence and accommodation become secondary to other visual factors. On the other hand, Woodworth
goes a little into the history andquotes Leonardo at length. Since ahistorycannot also

Distance

Woo dworth

be a

modem

On the history of the use of perspective In art, see the histories offor example, H. V. Cole, Fer.
specHve, 1921, 2ie>-242, e^. 216-

art,

224.

Leonardo da Vinci, one of thegeniuses the world has

greatest

VISUAL SPACE PERCEPTION IN DEPTH

304

known, brought hia ladle mind tn
beEir upon the problems of the tech-ener, physischor Bilder,nique of paintine. Wliile he probably
never published bis projected treatiseon painting, he left at his death in
1519 many notes which have beension ol hght and shade in tire deter-

combined into a Trattato della Pitand published in various editions and translations from 1651 to
1039. The latest volumes add new
items from the manuscripts, items

ogists Icnow thethat have never been published be-bulges), if the photograph is turnedtm

ibid,,

181,

1858, 298-311. For a modern ^scus-

mination of visually perceived depth,
see W. Meizger, Gesetze des Sehem,

1936, Chaps. 6 and 9. Most psychol-

photograph of theturret of the monitor Lehigh, dented

been used as a target.

after having

The depdi, given solely by light andshade,

reversedisbecome(dentsfore: J. P. Richter and I. A. Richter,

upside down or if tiro direction of the

The Literary Works of Leonardo dalight is reversed in imagination from

1939, 2 vols. In Vol.

downward to upward. U both imag-

Vinoi, 2 ed.,I

and photograph are reversed

are reprinted in Italianand Eng.

ination

700 notes— dicta,

precepts,

together, the deptlr remains, of course,

sketches,

the same.

trans.

technics,

observations,plans—which constitute the modern
and enlarged Treatise on Painting.
Leonardo, coming to power ns he

For Leonardo on

aerial perspec-tive,

see the Richter edition of 1930,

op.

cit.,

I,

210-212, 234-241(for

did at tlie heightd the naturalistic

the quotation, 236 f.). For G. Berke-

movement inlent his observa-

ley on the moon illusion, soo his An

art,tional powers

Essay towards a New Tlieory of Vi-

techniquession, 1700, soots. 67-77.

and his representative
support that movement. Perspective had been ‘discovered’ again by the Italians, andtodiscussion of linear perspectiveIris

125-161)(Richter edition, 1039,

I,

is important in showing

how fully its

principles were then understood andaccepted hy the artists of tliat time.

L^ardo's

discussion of the useof light and shade in painting is clas-

Thesical.

Richters give

been found
Leonardo’s

shade

(I,

in

\wat hasthe manuscripts ofbooks on light and
182-207, 213 f.). These
sis

sections indicate the extent of knowl-edge at the beginning of the 16th
century- extent rather than discovery, for the fundamental principles
must have been established long before.

On the reversal of reUef, see D
Bittenhouse, Explanation of an optical

deception,

Trans.

Arner. phO.
2, 1786, 37-42; J. J. OppeL
Ueber ein Anaglyptoskop, Ann.
Phyt. Chem., i75, 1856, 466-469;
See.,

H.

Sohriider,

Ueber eine optische

Fur H.

v.

Helmholtz’s discussion of the problem, see his Physiologtoal Optics,
1866, Eng. trans,,

1925,

III,

360-

362, where also is to be found astatement of Ptolemy’s theory offilledand empty distance.

Helnilultz's discussion of the parallax

ofmovement
OpticsPhysiologicaloccursin[1866],

theEng.

295-297. He menUons a brief note on die subject by
H. W. Dove, Ueber eine optische
Tauschung bei dom Fahren auf derElscnbalin, Ann. Phys. Chem,, 147,
1847, 118; the increase of speed oftrans., 1925,

III,

locomotion diat came with the invendon of the railroad must havemade the criterion more obvious, Although the author does not know
where early references to this principle occur,

itis

impossible that all

the natural philosophers were un-aware of it. The principle is obvious
to the habitual observer, but one does
not always put the obvious into
print.

Inversion her Betrachtung verkehrter,

On the reversible perspectives, seedurch optische Vorrichtung entworf-

L. A. Necker, Observations on some

NOTES
phaenomena seen ia
Switaerlaud; and an optical phaenomenon which occuis on viewing

iiimarkableofaor geometricalciystalPhil

Mag., 3 ser„

1,

1832,

337, esp. 336 f.i Schroder, op.

54, that Descartes says that accom-

solid,

modation is effective up to distances329-

of 3 or 4 feet and convergence up

oit.,

311 and Plate III; W. J. Sinsteden,
Uebei ein neues pseudoskopischea

Bswegungsphanomen, Ann, Phys.
Chem., 187, 1880, 336-339; Helmholtz, op.
(Eng.). Ill, 285 f. It

A

is,

305

37-51, pp. 37-55. It is in
De homine, p. 64, and L’homme, p.
articlesof course, prob;%le that the per-todistances

IS or 20ofPriestley, History

feet.

J.

and Present Stateof Discoveries Relating to Vision,
Light and Colours, 1772, 115, cites
this passage and says that Descartes

elsewhere assigned an effective distance of 100 to 200 feet for conver-spective revers.il of windmills is often

gence.

observed where windmills are numerous. Although Sinsteden and

G. Berkeley’s discussion of convergence as a cue to the perception

Helmholtz did not know it, the phe-of distancenomenon had been described by W.

wards a New Theory of Vision, 1709,
sects. 18-20. For Berkeley on accommodation, see sects. 21-29.

A Tiealise on the Eye,

Porterfield,

1759,

II,

384.

On tlie fluctuationsof reversible perspectives and theirin hisis

An Essay to-E. B. Titchener’s context theory

passible relation to the fluctuationsof meaningof ‘attention,’ see N, Lange, Beitriige

interests of tlie

zur Theorie der sinnlichen Aufmerksamkeit und der activen Appercep-

but necessarily applied from the mst

1888, 390-422,

on the Experimental Psychology of
the Thought-Processes, 1909, 174-tion, Phil. Stud., 4,

OleMarbe,
Swwankungen der Gesichtsempflndungen, ibid., 8, 1893, 615-637,
405-412;

esp.

esp.

K.

was formulated in the
problem of thought

also to perception. See his Lectures

A

180;

Text-Book of Psychology,

1910, 367-371.

For histories and classifications of

616 £., 635 f.

Convergence and Accommo-

accommodation, seetheoriesofMuller,Handbuch derJ.

Physiologie

des Menschen, 1838, Bk. V, sect, i,
Chap. 2, iii (Eng. brans., II, 1136-

dationFor the history of the theories of1150); Hud esp. H.

v.

Helmholtz,

the roles of accommodation and con-

Handbuch der physiologischen Op-

vergence in the visual perception offik,

distance, see J. W. Baird, The influ-

ence of accommodation and convergence upon the perception of depth,
Amer. 1. Psychol, 14, 1903, ISOBOO, esp, 151-170.

phis

Optloomm Ubii sex phmso-

juxta

tto

mathematids

1856, sect. 12

a few of the more important papers.
For Schemer’s experiment, see C.
Scheinet, Oculus, 1619, Bk. Ill, 163,
[n.v.], TTie

For F. Aguilonius on the horoptw,
see his(Eng. trans.,
I, 15^188). The text mentions onlyI,

utiles,1613, II, 146-150.

original;

author has not seen thetliis

and seven of the ‘n.v.’

bebw are taken from
Helmholtz, who is not always accureferences

rate in his citations.

On

For R. Descartes on convergence

the dieory that thereisnoand accommodation as the means of
the perception of distance and themeclianism of accommodation, seeof a blind person feelingconformation de I’oeil, J. des Spooons,picturesout a distance with staves, see his
La dioptric^, 1637, chap. 6 (first

P.

de

la

Hire,

Dissertation sur la

1685, 196-202, 219-j24; F, Magendie, Frdcis dldmentairede physioh-

De nomine, 1864, paragraphs

gie,

1816,

I,

73, [n.v.], (in the 4

18-21, pp. 43-85, or L'homme, 1682,

ed.,

1836,

I,

64 f., 74-76); G, R.

part);

VISUAL SPACE PEHCEFTION IN DEPTH

306

Tieviranus,

mr Awtomk

Seitriige

and Vhysiohgle del Sinnemerkceugedel Uemohen and der Thiere, 1828,
I,

On the theory that pupillary contraction is the (or a)mechanism ofaccommodation,

Scheiner,

see

op.

1819, in, 31, [n.v.]; A. v. Hal-

Elements physlolo^ae corporishuman!, V, 1763, 516-518; F. C.

ler,

Donders, in C. G. T. Beute, Leei-boek der Ophthabnologie, 1846, 110,[n.v.].

On the elongation of the eye as amechanismaccommadation, seede presbyopia et myopia, 1697, [n.v.]; J. B.
Listing, Dtoptrlk des Auges, in B,

J.

ofSturm,

C.

Dksertatto

Wagner, Handw&Herbudh der Physlologte, 1853, IV, 451-508, esp. 498500;

and,period.

Fordiechanges46-52.

oft,,and at least haU a dozen others in thisagainstthetheory,T.

Yonng, On the mechanism of the eye,seetheoryshape

inDescartes,

the

that

lens

accommodation,

1637,

dC,;

loo.

J.

reported by E, Homo,
Some facts relative to die late Mr.

HunterasJohn Hunter's preparation for the
Croonlan Lecture, Phil Trans., 1794,I, 21-27; T, Young, 1801, loc. cit.j
Beobachtungen and
J. E. Furkinje,
Vetsuche zar Physiologle der Sinne,n, 1825, 128; Helmholtz, Ueber
Bine blsher unbekannte Voranderung

am menschlichen Auge bel veriinderter Accommodation,

Uonatsher.

preuss. Akad. WIss., 1853,(or

WIssenschaftUche

137-139

Airhandlun-gen, H, 1883, 280-282); Ueber die
Accommodation des Auges, Arch.
Ophthal Berlin, I (2), 1850, 1-74
(or WIss. AbhandL, II, 1883, 283-

Phil Trans., 91, 1801, 23-88; or G.

345); Ilandbudh der physlologUchen

MlsceHaneous Works of
the Late Thomas Young, 1855, I,
12-63. For Helmholtz on Young, see
Helmholtz, loo. oJt., Eng. trans.,
158 f., 167.
As to whether a change of curvature of the cornea mediates accommodation, see J. F. Lob6 (Alblnus),
Dissertatlo de ocido humano, 1742,
110, [n.v.]; E, Home, The Croonlan
Lecture on muscular motion, PhU.
Trans., 1795, 1, 1-23, For a vigorous
modem objection to the Helmholtz

Optik 1, 1856, sect 12 (Eng. trans.,

Peacock,

and the contention that theexternal muscles of the eye accommodate vision by elongation of thetheory,I.

143-166).

On

Sanson's

images— die"rclleximages" ns they wore first called—
see Fm'kinjo, Do examine physlobgIco

organ!

olsus

etsyslematls

ootond, 1823, 21-29, who actuallydescribed and pictured four imagesof a candle fiame, the images fromdie front and back surfaces of thecoiuea and from the front and backsurfaces of the lens; L.

Legons sur

J.

Sanson,les maladies des

yeux,

M.

A. Langenbeck,
1838,
Klinische Beitrlige aus dem Gebiete

28-30;

trSge sur Fhpsiologie ufld Physik desder Chlrurgie und Ophthalmologie,
U, 1850, 105-107; A, Cramer, whose
first publicadon on the images in
Dutch is Mededeelingcn ult het
gobied der ophthalmologie (over den
stand der iris), Tijdsohr. d. Nederland. maatschapp. tat bemrd. d.
geneeskunst, 2, Ft. 2, 1851, 99-119,
but whose full discussion of the matter is in his Dutch text of 1853,
Chap. 3, so see die German trans.,
Phydologische Abhandlung Uber das
Accommodallons-Vermdgen der Augen, 1855, Chap. 3, 27-43; Helm-menschllehen Auges, 1841, 94-177;

holtz, loco. citt. Bates, op.

axis or increasing thecurvature ofW. H. Bates, The
Cure of Imperfeot Sight by Treatthe cornea, seement without Classes, 1920.
That the lens shifts back and forthin accommodation was the theory ofJ.

Kepler, Dioptrice, 1611, proposi-tion 26; Scheiner, op.

163, [n.v.];

J.

1619, III,

^

eft.,

Muller,verglei-chenden Physiohgie des Gesiaitsshmes des Idjensmen and Thiere,209-216, cm, 212; C. A. Burow, Bel-

cit.,

54,

NOTES&aicl tliat the image from the front of

die lens is not clear enough to estab-807

and convergence upon the perception of depth, Amer. 1. Psychol,tionlish the dieory of Cramer and Helm-

14,holtz.

Baird’s

For W. Wundt’s experiments on
the percepdon of distance, see his

Beltiageder Sinnes-

Theoriezurwahrnehmung, 1862, lOS-134, esp.
105-118, and 182-199. These two
portions of the Bettriige were originally published in 1859 and 1861
are DasAccommodation undHillebrand’s papers

Verhaltnis von

Konvergenz zur Tief enlokalisation, Z.
Psychol, 7, 1894, 97-151; In Sachender^eriment

optischen

Hillebrand's experiments with improved technique, see
Bappert,J.
Neue Untersuenungen zum Froblem

Akkommada-tion und Konvergenz zur Wahmehmnng derTlefe, £ Psychol, 90, 1922,

167-203.

Tlefenlokalisation,m., iK 1897, 71-161. The main
controversial

B inMadisonBentiey. The averages of Table 11
show significant differences, since theindividual cases do not scatter widely.
For a later repetition of Wundt’s andwasdes Verhaltnisses vonrespectively.

F.

1903, 156-200. Observerofissuesthat

Stereoscopy

timetended to divide German experimental psychologists into two groups:

On the history of the stereoscope,
see Sir David Brewster, The Stereo-

HelmbcLtz, Wundt, die Leipsig lab-scope, Its History, Theory, arid Con-the PhU, Stud., empiricism

struction, 1856, 5^7. This book also

on one side; and Hering, Slumpf, theZ. Psychol, nativism and phenomenology on the other. Hfllebrand inthese papets was Hering's mouth-

exhibits the importance of the stereo-

oratory,

Wundt

t&ough M.
Arrer, Ueber die Bedeutung der Convergenz- und Acccmmodationsbewegungen fur Tiefenwahmehmungen,piece.

repliedscope for the public in the midst of
the century that was noted for displaying the wonders of science.

On

the kinds of stereoscopes, see 63-75,

107-130; but the familiar hand stereoscope with a hood was invented
later by OUver Wendell Hobnes, Sun-

Phil Stud., 13, 1896-1897, 110-161,
222-304. Hillebrand also excited an

painting and sun-sculpture, Atlantic

experimental paper in England, E. T.

vrith which of.

Dixon, On the relation of accommo-

Monthly,

8,

1861,

1^29,

esp.

29,

E. B. Titchener, Ex-

perimental Psychology,

I,

ii,

1901,

dation and convergence to our sense

269. Holmes’ article also envisages

4, 1895, 195-

Hillebranda great future for the stereoscope, afuture in which, form having been
divorced from matter, the destructionofof the Pantheon would not be a greatof depth. Mind,

n.s.

212.

Another reason
disbelieved

in

the

why

effectivenessaccommodation for the perception of
depth was his discovery that an Aubert diaphragm, which was made toapproach the observer while its aperture was rapidly diminished in size,
was perceived as receding althoughreally approaching. Actually the ex-periment shows, however, merely thatloss

because any one could go to astereoscopic library and view it again

in all its original cornorealityl On thehisto^, see also H. v. Helmholtz,

Handbwih der physlolaelsohen OpHk, III, 1866, sect, 30 (Eng. trans.,
HI, 300-312, 350-369).

On binocular parallax and dispar-change of size can be more effective
than change of accommodation.
For T. W. Baird’s experiment andity ofthe fuUer history of this research,gives both thesee his The influence of accommoda-

trans.); G.

images as understood by theancients, see Euclid, Optica et Catoptrica,

theorems 23-28 (the 1577 «.

Greek and a Latin
De usa parBum

Galen,

VISUAL SPACE PERCEPTION IN DEPTH

308

corporis Immani, Bk.

10,Chap. 12

(pp. 592f. ofthelSSOed.).

Leonardo da Vinci's paradox of theopaque object tliat is binocularly

A Trmtisa

PM Mag.,given in inosL collec-

on painting, but isomitted from the Richter edition, op.
cit., 1939. See, for example, sect. 348

Rigaud Eng. trans, ofon Painting,1802 et seq,, which is baaed on the
Italian collection by R. du Fresne,

Leonardo,

telestercoscope, see his

ser,opter, see hiswhich is not
so dramatically put; in die Rigaud
trans., sect. 124i in the 1939 Richterischenanotlieris19-24).

Ueber die stereoskop-

Erscheinnngen und Wheatstone’s Angriff auf die Lehre vonden identischen
fmute.

item 28.

4, 15, 1857,

For E. Briicke's notion of tlie perception of solidity witli a shifting hor-

1651. Closely related to the passage
in questioned., I,W. H. F. Talbot as

early ns 1839.

F.

istions of his notesJ.

stereoscope by

For H. Helmholtz's invention oi theDas Stcreoskop, Ann. Phijs. Chem., 178, 1857,167-175 ( WIssenschaftllclie Abhandlungen, II, 484-491; and Eng. trans.,transparentof thephotographic stei-eograms (calotypes
or talbotypes ) wore prepared for the

Arch.

dcr

Netz-

PhystoL

Lpt.,

Stellcn

Anai.

On die combining of double images

1841, 450-478; and for li. A. Dove’s

by the sensus
communis (Aristotle’s concept of thehis Die Combination der Eindriickc

perceptive faculty which combines

beider Ohren und heidcr Augon zu

disparate sensations), see F. Aguilon-

einem Eindniok, Ber. preuss. Akad.
Wiss., 1841, 2511. For the relation

outside the horopterius,

OpHcorum

juxta

libH sex plulosapliis

ac maihematlcls

utiles,1613,

Bk. II, sect. 38, pp. 140 f.

For anearly atatemont that dis-A Treatise of Optieks, 1775,

The first but brief mention of C.
Wheatstone'sis

discoveryofstereo-by H. Mayo, Outlines of

Human Physiology, 3 ed., 1833, 288,
but Wheatstone's
scription

is

to

tliis

nativisra, a theory ofand the facts of rivalry

and binocular mixtiue, soo P. L. Panum, Plujsiohglsclw Vntarsuchmgen ilber das Selim mil meet Atigen,own and full de-

A modern analysis of tlie resolution of conflicting cues to distance(e,g.,

linear perspective

and shad-ing may together overcome tire nor-

mal effect of binocular parallax)ishis Contributions to the

W. Schriever, Experimentclle Studien

On some re-ilber slereoskoplsches Sehen, Z. Psy-

physiology of vision.

markable, and hitherto unobserved,

phenomena
Phil

all

1858, esp. 63-88,

171.

scopy

of

stereoscopy

parity of images may yield relief, soo]. Hanis,annihilation of Briicke’s theory see

Trims.,of binocular vision,
Pt.

I,

chol., SB, 1925,113-170,

I,

1838, 371-394;

Size and Distanceand idem, 11, Phil Mag., ser. 4, 3,
1852,

504-523.

The

dates

becomeOn the early history of the relaand also ofimportant because James Elliot is saidtion of size to distanceto nave thought of thethe alley problem, see W. Blumen-same installment in 1834 and to have made one
in 1839 (see Brewster, op. cit., 1822; but Brewster is not quite fair to
Wheatstone, having himself had acontroversy with him, for which see
22-36). TOeatstone described andfeld,

Untersuohungen

Uber

die

scheinbare Crosse in Sehraume, Z.
Psychol.,

65,

1913,

241-404,esp.

2^274; on the later history of size
constan(w, see M. R. Sheehan, A
study

of

individual

consistency inpictured his refiecting stereoscope inphenomenal constancy. Arch. Psychol.

1838; be described a refracting stereoscope and also the pseudoscope in

N.Y., no. 222, 1938, 14-19, esp. 14-

1852. He also mentioned in 1852 that

researches

16; and also the general discussion ofby E.

KofEka, Principles

NOTESof Gestalt Psychology,

193S, 211-

264, and esp. 87-95, 235-240.

309

Sanford,

A Course in Experimental

For E, Hering’s distinction of thePsychology, 1898, 273, notes, as avariant <5 Meyer’s observation withthree lands of sizes, see his discus-wall-paper patterns, that one can hold

Hermann's Lehrhuch derFhystologfe, III, i, 1879, 541 f. Her-up a cane-seated chair, converge theing said scheinbare GrSsse for visual

identical unils of the repetitive pat-sion in L.

angle or retinal

size,

Sehgrdsse forphenomenal or apparent

size,

and

geschStze Oder gedachte GrSsse for
estimatedwritingsize.

In current

scheinbare

German

GrSsse can hetranslated correctly as apparent size,

and SehgrSsse as phenomenal size.
On Euclid's distinction between
apparent size and visual angle, see
Hirschberg, Die Optilc der alten
J.
Groiclren, Z. Psychol, 16, 1898, 321351, esp. 323 f.

eyes so as to combine other thantern of the seat,andperceivetints

the seat as bulging out in front of
its

frame

(cf.

E. B. Titchener, Ex-

perimental Psychology,
262; also R.

S.

I,

1901,

ii.

Woodworth, Experi-mental Psychology, 1938, 676). A
modern study that conUrms theseearly experiments in more systematic

form is H. Frank, Uober den Einfluss
inaditquater Konvergenz und Akkom-

modation auf die Sehgrdsse, Psychol.
Forsch., 13, 1930, 135-144.

On me converging vista in theavenue of trees, see W. Porterfield,

Aubert-Foerster

A Treatise on the Eye, 1759, II, 381-

fact tliat the total spread of that field

384; J. Priestley, Tlie History and
Present State of Discooeries Relating

The text makes no mendon of thephenomenon,

theof vision (measured in visual angle)

and Colours, 1772,

whose boundaries are the limits ofany given degree of acuity (meas-

700-704. It is Priestley who discusses

ured also in visual angle), is less forat length the views of the prollSo P.

a far field than a near; that is to say,the separation of two objects by one
minute of arc can be distinguishedto Vision, Light

Eouguer (1698-1758) on this matter, out he gives no rrference andthe argument is not in Bouguer’s Essoi d'optique, 1729, or his Tradefrom the center of thefarther out

retina when tlie objects are near thantfoplk/ae, 1760.

when tliey are far. Such a rule is

For the middle nineteenth century
observations on the reladon of apparent size to apparent distance as
convergence or accommodation varies,
see H. Meyer, Ueber einige
Tauschungen in der Entfemung und

not inconsistent with the principle

GrossederGesichtsobjektc,

physiol Hellk.,

1,

1842,

Arch,

316-323,d size-constancy. The law of sizeconstancy implies that at greater distances less of the retina functions forthe same apparent size. The AubertFoerster law implies that, in spiteof size-constancy, the total fieM ofvision(for

any degreeofacuity)316 f.; Ueber die Scliiitzung derGrosse und der Entfemung derGesichtsohjekt nus der Konvergenz
der Augenaxen, Ann. Phys. Chem,,
161, 1852, 198-207; C. Ludwig,
Lehrbuch der Physiologfe des Menschen, I, 1852, 252 f.; F. L. Fanum,
Die scheinbare Grosse der gcschcnen
Objekte, Arch. Ophthal Berlin, 5,

does not inorense with distance, nor

1859, 1-36, esp. 14-38; G. T. Fech-den Raumsinn der J4etzhaut,

esp.

ner,

Elemente der Psychophysik,H1860, 311-313; E. Hering, Beitroge
sur Physlologie, 1861, 13^16. E. C.

does

the

resolving

power

of

the

retina ( in visual angle) increase with
distance. The consequence is tliat an

abject on receding should lose someit appears toremain the same size and to occupyof its detail, although

the same proportion of the total fieldSee H. Aubat and R. Foasta, Ueba
Jber.

Ges. oaterl Kult,, 43, 1856,
33 f. (brief but first); Untersuchung-settles.

en fiber den Raumsinn der Retina,

VISUAL SPACE PERCEPTION IN DEPTH

310

Arch. Ophthal Berlin, 3 ( 2), 1857,
1-3? (the main exposition)i E.

20. 1911, 101-149; Blumenfeld, op.
eft., 1913. It should be noted that the

Jaensch, Zur Analyse der Gesichts-

text omits

wahmehmungen, Z. Psychol, Ergbd.

differences in diese reseaiches. Dif-

1909 (practically all about thephonomencm); E. Freeman, Untersuchuneen iibei das indirekte Sehen,
PsycM, Borsch,, 14, 1931, 332-

ferent investigators found different

879 (historioal account, 339-341).
On Emmerl's law. see E. Emmert,

sults

R

4,

Grdssenverhaltniase der Nachbllder,mentionmany

ol

forms and dhecUons of curvature in
the loci of the apparent parallels.

Blumenfeld got slightly different re-when nia observers tried tomake the lights fonn parallel lines
and when they bled to make them

Mbl AvgenheUk., 19, 1881,443-450. The relation o( Enunert’s

everywhere equidistant.

law toLet 5panzees,Klin.

size constancy is as follows.

= perceivedd=linear size;f=distance. Then;retinal size;

const.,
s~(i, if(1)
which is Emmert’s law. Moreover,

~

=

small

On die perception of size by chimsee W. Kohler, Optisohe

Untersuchungen am Schlmpansen
und am Haushulm, Abh. preuss,
Akad. Wiss,, phys.-math. KL, 1915,
no. 8, esp. 18-139; in chickens, see(2)W. Gbtz, Experimentelle Untorsuch-a statement which is Implicit in theungen ziun Problem der Seherissenkonstanz beiin Haushuhn, Z, Fsuchol, 99, 1926, 247-260, esp. 254 f.

e

f, if

definition ofdconst.,

since ss,ismeasuredby the actual size of a comparison
sUmulus at a constant distance. Hences~k1,

On the relation to ago, see F. Boryl,

which is the general formula for apparent size mentioned in the tezt.

Ueber die Ordssennuflassung bei
Kindem, ibid., 100, 1926, 344-371,
esp. 364; and also H, Fkank, Die

This formula implies

Sengrdssenkonstanzs=: const., U ni

(3)=const,(4)bei

Pn/oliol. Borsch., 10, 1928,

Kindern,
102-106,

which is the law of size constancy.

On individual diffcrenoc.s, see R. 11.

In this sense size constancy (4) be-

Thouless,comes a special case of Emmert'slaw (1); but it is also passible toderive (3) from (4) and (2) so that
Emmert’s law becomes die special

phenomenal regression, Brit. J. Psy-

case of size-constancy.

On this re-

Individual differences in

22, 1932, 216-241; M. R.
Shoehan, op. cit., esp. 39-43. For ageneral analysis of the conditions,chol,

see B.

E.

Holaday, Die Grdssen-lationship, see E. G. Eorlng, Size con-konstanz der Sehdlnge bei Variation

stanw and Emmert's law, Amer. J.

der inneren und ausseren Wohrnehmungsbedlngungen. Arch, ges Psychol,88. 1933, 419-488.

Psychol, S3, 1940, 293-295.
G. Matdus's experiment is Ueber
die scheinbare

Grosse der Gegen-

The best exposition of size con-

Eeziehungstancy from the point of view ofstiindeundIbre

GrbssederNetzhautbilder,

zur

Phil

Gestalt psychology

isKoffka’s, loco.

On the alley mperlments, see F,

and esp. Chap. 3, where Koffka
combats tire “interpretative theory”

HiUebrand, Theorio det scheinbarenof the perceived object in the inter-

Stud,, 5. 1889, 601-817.

Sehen,

ests of the phenomenal object formed

Denkschr. Akad. Wiss, Wien., math.-by field forees. That Koffka’s belief

CrOssenatbela, 72,

binocularem
1902,

255-307;W.

in "size constancy’’isa measure of

Foppelreuter, Beitiilge zur Haumpsy-

his disbelief in the constancy of size

bhologie, Z, Psychol, 58, 1911, 200-

for constant visual angles is clearly

zur

indicated by his comment that Beryl's

Kenntnls des Sehiaumes auf Grunddata "reveal an amazing degree ofder Ehrfahrung, Arch. ges. Psychol,

constancy if compared [with what]

262;

F,

Schubotz,

Beibfige

NOTES

311

represents the sizes of hoses

whichwould have produced a constantsee his Die ZugSnglichkeit von Ge-

image” (p. 92), Beryl’s data
would be amazing only to one who

Arch, ges, Fsuohol., 88, 1933, Slf418, for the formula and degrees of

constant apparent size for

Dingkonstanz, 387-411; Wahmehmung und Gegenstandniieh, 1934,

retinalexpects

constant visual angle. This concept

geirstanden fur die

Wahmehmui^,of phenomenal constancy was 6rst in-

esp.

troduced hy Kohler in 191S, loo. cit,;

For R. H. Thouless’s experiments andhe did not then, however, speak of
SehgrSssenkonstam, but only of relative constancy, In 1917 he used theterms Farbenkonstans and Grossenkonstmz casually, Die Fnrbe derSehdinge beim Schimpansen undbehn Haushuhn, Z. tsuchol, 77,
1917, 24S-2S5. esp, 254. By 1928
Miss Frank, as wo have seen, regarded the concept as established andput Sehgrdssenkonstonz in her title.

measures of regression, see his Phe-

48-92; also Holaday, op.

eft.

nomenal regression to the real ob1931, 339-

ject, Brit. J. Fstjckol, 21,359 (formula, 344); 22, 1931, 1-30.
For a recent analysis of the perception and its ‘reduction,’ almost to
the law of the visual angle, by theremoval of various cues

tothe per-

ception of distance, see A. H. Hol-

way and E. G. Boring, Determinantsof apparent visual sfoe with distance

Size constancy came into English as

variant, Amer. J. Fsychol, 54, 1941,a translation later.

21-37,

A terminological confusion arises
here because the constancy of rela-

Tridimensional Dynamics

tion between the form of the percep-

and die form of the stimulus
has been called the constancy hypodtesis—casually by KSliler, who
Inveighed against its use, Ueber unbemerkte Empfindungen und Urteils-tiontkuschungen, Z. Fsychoi., 68, 1913,
Sl-80, and more specifically by his'The

The best account of the Gestalt
theory of the perception of depth

and distance is K. Kottka, Some problems of space perception, FsuAohgies of1930, 101-187. Cf. alsomo,Kofika,PrinciplesofGestaltPsy-chology, 1935, 265-280. Kofika gives
theillustrations

chologist rejects the constancy hy-

dted (on his behalf)in the text.

pothesis because

The reference to E. Schur is Mondtauschung und Sehgrftssenkonstanz,colleagues

later.

It

Gestaltis

psy-

Incompatible

with phenomenal constancy.

It

is

the

references

toterm, al-

Piychol. Borsch., 7, 1926, 44-80, esp.

though it is interesting to see thatcompromise between diese two op-

75 f. For W. K8hler on isomorphism,
see his Gestalt Psychology, 1929, 6064; The Place of Value in a World of

posed constancies.

Facts, 1938, 185-232; also other ref-better to forget thefirstBrunswlids Ztoischengegenstiind is a

For E. Brunswik’s systematic view.

erences cited on p, 96.

Chapter 9

PSYCHOPHYSICS OF TONE

bout hearing there is less to say in modem psychology

Athan about vision, and the history of the psychology of audiL.tion iscorrespondingly less voluminousand complicated.

There arc, for one thing, fewer auditory relations to describe thanvisual, partly because the spatial dimensions are not added to thequalitative in heai'ing, and partly because the ear is mechanicallyso arranged that there are fewer after-effects of stimulation, On
the other hand, the history of music, like the history of piclorialart,

goes back into prehistoric antiquity, tnid it was in connec-

tion with music that the stimulus to tone was first defined. The

establishment of the notes in definite relation to each other camefirst,

a process forwarded hy Pythagoras and continued throughmany centuries up to the adoption of equal temperament in thenineteenth century. In the seventeenth century the physics ofsound began—the knowledge about frequencies, media of toansmission and velocities. The psychophysics of tone began in theeighteenth century, although there was no sustained effort in thatfield until experimental psychology appeared in the latter half ofthe nineteenth century, a period which Helmholtz introduced withhis Die Lehre von den Tonempjindungen in 1863. That text, writ-

ten and published in between the second and the third volumesof his Handbiwh der physiohgischen Optik, was, and is, like the

Optik, the classic in its field. In the twentieth century, however,the pattern has completely changed.

The development of thethermionic vacuum tube has given the investigator such a control
of acoustic stimuU, that the resulting wave of research has brou^t
the auditory problems well past the stage where phenomenologicaldescription is any longer in itself an impoiiant goal.

.

The Origin of Musical Notes

Because tones, unlike colors, do not mix to provide an infinitude
of tones &om the combination of a few primaries, it has
312

come

GREEK INTERVALS

313

about that music difiers from painting in its employment of discrete elements instead of the qualitative continua that the lawsof color mixture make available. Thus the scale of western music——the most highly developed tonal scalestilloanies in itself thelimitations of the fixed pitches of the musical instruments of the—the

Greeks130-6

and Ae flute. Had it been possible with theseven-stringed lyre to get intermediate pure tones from the mix-—

ture of tones lying on either side of the resultant^like orange

from

red and yellow—the development of music would have beenaltered enormously.
If

we are to have a tonal scale of discrete fixed pitches, then wemust know about the intervals between the pitches. We must
know, for example, whether there are any native intervals deter-

mined by perceptual properties of the human organism. It is quitepossible that the octave is in some sense ‘native,’ for voices ofdifierenl register tend in singing to faU into unison with octave

separations, as, indeed, Aristotle remarked.

There may, in fact,

be something about the human ear that accounts for the similarity
of tones when the frequency of

one is just twice the frequencyof the other, or it may be that this similarity comes about because
all the haimonics of the octave of a tone are also harmonics of thattone.

We know now that a fundamental tone is never heard with-out its partials. The octave was, however, whether ‘natural’ or not,too large an interval to enter into early music which, besides be-

ing vocal, melodic and simple, was quite hmited in range.
Besides the octave, the interval of the fourth has been regarded,at least by some students of the histoi-y of music, as a native interval; in descending cadence it is, they say, the natural drop forthe voice in making a statement. The recitative is thus based upon
the descending fourth. Yet it seems probable that what is natural

about the fourth is only its descent, which gives it the feeRng of
finality or repose. It was the Greeks who, after approximating thefourth, at first fixed it as thebasic interval when Pythagoras in-vented the monochord and discovered the relation of pitch to thelength of the string.

That there are any other native elements in tones, besides theoctave similarity and the relaxation of a falhng cadence, the history of music seems to deny. There have, indeed, been many otherkinds of scales in eastern music, and the history of our own occidental scale from the Greeks to the present is a history of decision

314

PSYCHOPHYSICS OF TONE

and change with regard to the notes established as proper at any
given time. Let us examine the origin of this scale among the
Greeks.

The primitive base of Greek music was, then, the descending
cadence of approximately a fourth, two notes elaborated by a thirdintermediate note to provide the rudimentary possibilities of melody. In modern notation we might represent such a cadence byA-G|)-E. This sequence, however, presently became complicatedby die addition of a leading note just above the final note, andthe adjustment of the position of the intermediate note to a place

halfway between die initial and the leading notes; thus, A-G-F-E,

which is the diatonic tetrachord basic to early Greek music. It isinteresting to see that the direction here is downward, that theleading note leads down into the final. Since descent is obviously

the correct way to get the perception of finality, it is puzzling toknow how the modern sequence got itself reversed so that scales
are thought of as ascending and the leading note as always pointing up to the tonic. The Greeks also came to use two other foitnsof the tetrachord; the chromatic tetrachord, in which the middle
note was moved down so that it was practically a leading note to

the leading note (as A-Gj)-F-E); and the enharmonic tetrachord,a descending fourth with two notes before the lower separated

by quarter-tones (like A-F-e-E, if c signifies a quarter-tone aboveE). These three lands of tetraohords were diEerent genera andwere used contemporaneously. To each genus different musicaleffects

were ascribed; the diatonic was said to be manly andaustere; the chromatic, sweet and pathetic; the enharmonic, ani-mating and mild.

Somewhat later a second tetrachord was added, continuing
beyond the first, perhaps by Terpander (ca. 700 B.c.) who is generally

regarded as the founder of classical Greek music. In the

resultant heptachord the upper note of the lower tetrachord wasused as the lower note of the upper tetrachord; hence the sequence

was much like D-C-B-A-G-F-E, with A, common to both tetrachords, the "middle string.” The note of this “middle string,” much
like the tonic in modern music, came to be an orienting point forthe melodies. The seven-stringed lyre, on which this music wasplayed and which was the accepted instrument for a century or

more until Pythagoras successfully added the eighth string, actually did not contain the octave. Thus it happened that music was

GREEK INTERVALS

815

not at first based on that ‘natural’ interval, the octave, which wasintroduced only later when the range of melody was extended.
Various Greek musicians tried to increase the lyre’s strings toeight or even eleven, but they met with opposition. Among theSpartans, who had a law against more than seven strings, judgment was sometimes passed requiring the executioner to cut theadditional strings from a lyre. Pythagoras (ca. 530 b.c.),how-ever, was able to bring music under his philosophy of number, andthus to begin a long association between music and mathematics.

He originated the monochord, a stretched string whose length
can be altered by a movable bridge. The first to establish theoctave as determined by lengths of string in the ratio 2; 1, he went
further to lay

down the rule that simple ratios yield the best

consonances. Thereisno doubt that the properties of number

were more important to Pythagoras in his consideration of music
than the properties of auditory sensation; only long afterwards did
Aristoxenos (ca. 318 b.c.), in opposition to the Pythagoreans’ pre-occupation with number in music, found a school that cham-pioned the importance of sound as validating the musical canons.
In terms of the ratios of string-lengths, however, Pythagoras wasable to regularize the scale. He separated the two tetracbords ofthe lyre, extending them to fill out the octave and adding thehitherto objectionable eighth string. The scale then became ap-

proximately (E-D-C-B)-(A-G-F-E), a sequence which constitutes the notes of our modern scale, although organized about

the “middle string,” A, instead of the tonic, C.
It was in this way, by the necessity of establishing fixed pitches

in musical instruments, that the system of tones became defined
as discrete units, the notes of scales, and not as continua, like thecolors of painting. The important thing to realize is that, aldiough
historically scales have been basic in the understanding of tone,

the intervals of the scales are not ‘native’ and inevitable; rather,

they have been set up, one way and another, in a long history ofexperimentation. The first interval to be fixed was the fourth, thelimits of the tetrachord. Its stringsgave the soni stabiles whichwere not changed, and upon them all other intervals were based.
After Pythagoras there was, aR the way on into the nineteendi
century, a complicated development of scales and intervals. Music

had to face a series of inevitably unsatisfactory compromises. The
difficulty was this.

On the one hand, the Pythagorean notion that

PSYCHOPHYSICS OF TONE

316

the best intervals are those with the simplest ratios was right; theseintervals,

having the largest number of coincident harmonics,

were best suited for the polyphonic music that developed after
the tenth century and for harmony proper, which may be said tohave begun in the sixteenth century. On the other hand, there
was an insuperable mathematical difficulty in the fact that the
product of hvo simple ratios is not usually an equally simple ratio.
If only 4/3

X 4/3 equaled 2 instead of 16/9, for then two perfectfourths would make an ociavel Actually they make a minor seventh.

In the Pythagorean scale each tetrachord is meant to be two wholetones and a semi-tone, and the tetrachords are separated by a whole
tone, so that six whole tones ought to make an octave. Euclid dis-covered, however, that six whole tones exceed the octave by what
is aboutan eighth of a whole tone. Didymos ( ca. 63 B.c.-ca. 10 a.d. )worked out the best solution. He made each tetrachord consistof a major tone (9/8), a minor tone (10/9) and a semi-tone(

16/15), with a major tone between the tetrachords. This arrange-

ment gives the octave, for 9/8 X 10/9 X 16/15 X 9/8 XlO/9 X
2 exactly. The resultant scale is diagrammed as the
9/8 X 18/15=

scale of just temperament at the left of Fig. 50. Receiving the sanction of Ptolemy ( ca. 130 a.d. ) , it persisted for a long time as the ancestor of the modem occidental scale. It is, in fact, what has beencalled the ‘natural’ scale, although its naturalness is more mathe-

matical tlian physiological. Newton believed in it: he tried to makea heptachord of the spectmm with seven discrete colors spaced
according to these specifications of Didymos (see pp. 104f.)l

The great difficulty with this just temperament is diat the sevennotes suffice only for one key. Every note in the scale has a simple
ratio to the key-note:from the major second to the octave, theratios are 9/8, 5/4, 4/3, 3/2, 5/3, 15/8, 2/1. Unfortunately, how-ever, the ratio between pairs of notes that do not include the key-note are not all simple. If the fifth, C-G, has its proper ratio 3/2,

then what ought also to be a fifth, D-A, has the ratio 40/27. And
the tritone would be 45/32 when it is F-B, and 1125/1024 when it
is

B-f. Even when the eight notes of the octave are increased to

twelve by dividing the major tones and the minor tones (Fig.
50, left), it is still not possible to play accurately in more than

one key. Starting the sequence of intervals in just temperament at

any new point throws the successive notes out of step with theoriginal series. In fact, to get just temperament in any one of twelve

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PSYCHOPHYSICS OF TONE

318

keys would require 34 notes in the octave, a complication muchtoo great for an organ or other instruments in which the pitches
are fixed. Thus eventually further compromise became necessary.

The history of musical temperament is important for psychology
merely in this way. It shows how the ‘natural’ intervals are uniqueonly in the sense that, having many coincident partials, they are

most consonant in harmony. The various scales that have hadserious use in occidental music are as follows.

(!) Just temperament, the Pythagorean octave compromised by

Didymos and Ptolemy (Fig. 50) to give simple ratios, and hence
called in the nineteenth century the “natural scale.” It can be used
in a cappella singing, and the Tonic Sol-fa Association of London(founded 1873) urged its use; but it cannot be employed, as wehave seen, on most musical instruments if there is to be a change
of key.

(2) Pythagorean temperament,a series of perfect fifths, notmuch used in western music. In it die octave is not a perfect simple ratio.
(a) Meantone temperament, invented by F. Salinas in 1577 tomake the ‘whole tone’ a mean between the major tone and theminor tone(of. Fig. 50).

Actually it requires 27 notes to theoctave, but the organ builders, becauseit

was impracticable tointerpolate more than five notes in their proper places, kept theoctave down to a total of 12 notes; C, Cf, D, El>, E, F, Ff, G, Gf,
A, B[j, B, making only six keys possible, viz., the keys of C, G,

D, A, F, and Bj). H an organist got into the key of E|j and wanted tosound the chord A|j-C-Ejj, he had to strike Gjf instead of A|j, andGH, being almost a quarter-tone flatter than A|;, created a discord

which came to be known as “die howling of the wolves.” Until
itsdisplacement by equal temperament in 1841-1846, meantone

temperament, nevertheless, was used almost universally on organs,claviers and pianos.

(4) Equal temperamevi, which has long been found in Chinesemusic, was suggested by Aristoxenos ( ca. 320 b.c. ) and supported,

formally by the arguments of G. Zarlino (1558). It was favored

byj. S. Bach, who wrote for it the WoWtemperirtesKZaoier (1722),
containing twenty-four preludes and fugues, one in each of thetwelve majoFand the twelve minor keys. The general adoption ofequal temperament waited, however, until the middle of the nine-a.

STANDARDS OF PITCH

319

teenth century. Mg. 50 shows how much it varies from just tem-

perament.

So it turns out that the stabilization of the musical notes is arelatively recent occurrence in the history of music,

and thereason for this tardy development is not hard to find. Music had
to wait upon physios.

When Salinas invented meantone tempera-

ment in 1577, there were no exact means for measuring the stimulus,

The variation of pitch in musical instruments was controlled

by altering the lengths of strings or of pipes. Although Pythagoras

knew that the shorter strings vibrate more rapidly, die measurement of frequency and the law of its relation to pitch awaited
Galileo’s research

about 1836. Even then there was no simple

method for testing the tuning of an organ in terms of frequency.
For almost three centuries the tuners aimed at meantone temperament; yet there is little evidence that for the first half of this period
they struck very near their goal. The meantone wolves’ mighthowl in certain keys, but undoubtedly mistuning led to otherdiscords even when the ‘wolves’ were silent.

Shortly after the coronation of George I in 1714, John Shore,

who had been sergeant trumpeter at the coronation and had been
made Lutenist in the Chapel Royal, invented a tuning-fork—"pitch-fork,” as hehumorously called it—by which to tune hislute. The law of beats was discovered about the same time ( 1700)

Thus there actually existed, before Bach wrote his music for thewell-tempered clavier, a possibility of accurate tuning, althou^ it

was not generally utilized until later.
It was in the middle of the nineteenth century—the ‘century ofscience’—that accurate calibration of musical notes was under-

taken. By then the tuning fork had developed into an instrumentof precision. Thus in 18M J. H. Scheibler was able to constructa tonometer of 58 tuning forks for the purpose of calibrating musical instruments.

Marloye, a famous instrument-maker in Paris,

put the tuning forks on resonance boxes in 1839, and his evenmore famous successor, Rudolph Koenig, who took over his business in 1858, developed the precision of die tuning fork to such a

degree that Koenig forks came to be known throughout the scientific world and cheiished in physical and psychological laboratories.

Meanwhile, in 1840, A. Seebeck constructed h siren which

proved a convenient instrument of caRbratlon because its

fre-

820

PSYCHOPHYSICS OF TONE

quency was easily determined by its speed of rotation and thenumber of holes in its rotating disk. Subsequently, in 1860, A.
Toepler employed a stroboscopic method for the study of thevibration of singing flames, and A. Kundt devised the dust method
for computing die frequencies of tones. Altogether, the forty years

from 1880 to 1870 constituted a period in which great advanceswere made in the control of the frequency of the tonal stimulus.

That the unsatisfactoriness of meantone temperament should havebeen admitted at this time was, thus, no accident, or that equal
temperament should have come into general use in the 1840’s.
This same period saw the establishment of absolute standardsof pitch. Scheibler, using his tuning-fork tonometer to study thepitches of concert pianos in Vienna, finally recommended to acongress of physicists at Stuttgart in 1884 that a standard of

A =440 c.p.s. be adopted. This standard has since been called
the Stuttgait Pitch. The pitch at the Paris Opera, which had beenA = 404 c.p.s. in 1699, had risen to A = 423 in 1810 and to
A 450 in 1858. A commission of the French government then=decided to establish the standard at A

= 485, and tho physicist

Lissajous prepared a standard fork of this frequency for preservation.

(Koenig in 1880 found that the fork was, however, almost

half a vibration in error.) Ellis, who has been at great pains todiscover all the pitches that have ever been established and used(sometimes he constmeted model organ pipes to historical specifications in order to find out the frequency), has listed 188 pitches

employed from 1615 to 1885. The standards range through theinterval of a fifth, fromA = 373 to A = 5671

Thus it came about that music, aided by recent physics, wasable to furnish the new experimental psychology in the middleof the nineteenth century with pretty good specifications for the

tonal stimuli. Helmholtz’s

Tonempfindungen in 1863 dealt fully

as mudi with musicology as with psychophysiological acoustics.

Until well into the 1920’s the tonsd stimuli were designated bypsychologists as notes in some standard scale for some standard

frequency of A. The occurrence that took the psychology of hearing away from the musical specifications of the stimulus was thedevebpment of the control of electrical frequencies by the electronic vacuum tube. With electrical oscillators the control of pitch

became independent of musical instruments and of fixed pitches
in general. Because frequency t»uld at last be varied easily andPHYSICS OF SOUND

321

continuously by changing the electrical properties of a circuit, theartificial emphasis upon a fixed number of notes—with equal tem-

perament music uses only about 100 notes, nine octavos—was lost.
A. frequency of1000 c.p.s. was accepted as the specification for areference tone, and the only trace of the musical intervals in the

research of the 1930’s comes about accidentally, inasmuch as it iseasier to deal with the logarithms of frequencies than with fre-quencies proper.

Ph3rsical Acoustics

At this point we must turn to the history of the auditory stimulus, a part of the history of thephysics of sound.

The Acoustic Medium. Although it was obvious from the firstthat sound can travel through the air, it was not clear that the air
Itself is the essential conductor. It was Aristotle’s suggestion thata sounding body displaces the adjacent air, which in turn moves
the air next to it, to the end that the spread of sound occurs by the

propagation of the motion of the air. There could, however, be no
crucial test of such a theory until means were found for creating

vacuums,

Vacuums could be had after Torricelli had invented the baromThe barometer is an inverted tube in which atmospheric pressure supports a column of mercuiy, with a vacuum
eter in 1643.

above the mercury below the sealed upper end of the tube. In
1650 Father Kircher used such a tube with a glass globe, containing a bell, sealed to one end. He filled it with mercury, in-verted it in a dish, letting the mercury level drop until it was sustained by atmospheric pressure, and thus

hadthe bell in a

Torricellian vacuum. Unfortunately for the cause of truth,when

he actuated the bell from outside by a lodestone, the sound was

audible—presumably because the support of the bell conducted
the sound to the glass.

A few years later the Italian Academy in Florence failed in asimilar experiment, but presently Guericke, having invented theair-pump in 1650, utilized it for this experiment. After suspending by a thread in a jar a bell that would ring by clockwork, henoted that, as he pumped the air Irom the jar, the sound of thebell got fainter until it ceased,

and that, on tlie other hand, thesound became audible and then louder as the air was again let in.
This experiment, carried out successfully by Guericke about 1657,

PSYCHOPHYSICS OF TONE

322

was verified by Eobert Boyle in 1680. Thereafter various otherinvestigators showed that water, solids and gases other than air
will conduct sound, thus explaining Father Eircher’s failure. It isinteresting to note that seventeenth-century music could

be sohi^ly developed—well beyond the stage of meantone temperament in organs—before anyone was certain that air is the usual
conductor of sound.

The Velocity of Sound. Another fundamental problem interesting the naturi philosophers of the seventeenth century was thevelocity of sound It was apparent that, when a cannon is fired at

a distance, the flash is seen before the sound is heard. Since thetransmission of light is at these distances practically instantaneous, themeasurement of the time between thefiash

and thenoise will give, in conjunction with the distance, the velocity ofthe sound. Gassendi (1824) was die first to employ this meihod.

Wishing to show Aristotle mistaken in his assertion that highpitched sounds travel faster fiian low, he compared the times forthe sound of a cannon and of a musket and found no great difference.

Mersenne (1638), Galileo’s pupil, repeated Gassendi’s experiment, and there were numerous subsequent repetitions. Every-

body got a different velocity, but Gassendi's figure, which was
1473 feet per second, was lowered by Mersenne to 1380 feet pet
second, and by BoreUi and Viviani (1656) to 1077 feet per sec-

ond. (The correct value is about 1128 feet per second in dry air
at 20°C.)

Mersenne also used an echo. He found that he could

shout Benedicam Dominum in just one second, and that an echo

from a wall 519 feet away began just as his utterance ended, sothat his voice and the echo together said BenedicamDominum~

BenedicamDomimm, The velocity of sound he therefore set down
at 1088 feet per second.

Newton in 1687 calculated the velocity from theoretical considerations, but he got a figure of only 968, against which was set

an official determination at the Greenwich Observato^ (in 1708)
of 1142 feet per second. It was not until 1740 that Bianconi

meas-

ured the great effect of temperature upon the velodiy, thus ex-

plainmg some of these earlier discrepancies. Between the resultsof an experiment in summer and one in winter(36°C. difference),
Bianconi found a difference of about 42 feet per second.
Pitch and Frequency. From the psychologist’s point of view the

PITCH AND FREQUENCY

323

great acoustic event of the seventeenth century was Galileo’s dis-covery of the dependence of pitch upon frequency. Pythagoras

had worked out the laws of the dependence of pitch upon thelength of strings; he knew that decreasing the length of the string
to one-half raises the pitch an octave, and he had determined theother simple ratios for the intervals of the fourth and the fifth. He
also knew from the observation of long strings in which the vibra-tion is immediately apparent, that shortening the string increases

the speed of vibration: yet of relative frequencies he had no quantitative knowledge.

Galileo found, in scraping a brass plate with an iron chisel, thatthe operation sometimes made a whistling noise and that, when-ever this tonal sound was created, the chisel left a series of small
parallel streaks upon the brass.

He experimented. First he noticed

that, the higher the pitch, the more numerous the streaks.

Then

he measured the pities by resonance. He got a series of streaks
to the sound of which one string on an instrument responded, andafter that another series to which another- string responded. The

two strings were tuned a musical fifth apart. By counting thescratches in equal distances on the brass he found 45 scratches
for the higher string and 30 for the lower, that is to say, the ratio
3:2, the proper ratio for the fifth. In other words, pitch depends

upon frequency, and frequency varies with the length of the string.
After that Galileo, old and frustrated by the Inquisition, left the
problem to Mersenne,

Mersenne began with a taut hemp rope, over ninety feet long,sbw enough to be counted. Thenin which the vibrations were

he extended his studies to brass wires, and was able finally to lay

down the chief laws of the stretched string; that the frequency ofthe string is directly proportional (a) to its kngth, (b) to thesquare root of the weight which stretches it, (c) to the squareroot of the weight of the string itself, (d) to the reciprocal of its

diameter, and (e) to the reciprocal of its specific gravity, These
relationships, first put in a more general formula by Brook Taylor

in 1713, were given their modem expression by Euler in 1739:

„

1

I

tensionMeanwhile Shore had invented the tuning fork (post 1714), andwas beginning to become important to the

Galileo’s discovery

PSYCHOPHYSICS OF TONE

324

musicians. Robert Hooke, for instance, in 1681 arranged to rotate

a set of toothed brass wheels allowing an object to strike theteeth.

Rapid rotation produced a musical sound. Doubling the

speed gave an octave, increasing it one-third gave the fourth, andso on.

Much later this principle was used by Savart (1830) for

the determination of the limits of hearing. The general principle—that discrete impulses whose rate is mechanically controlled will

yield pitches which vary with the rate

—wasalso employed in See-

beck’s siren (1841).

The Galilean law of pitch as a function of frequency stood as abasic canon of psychological acoustics until Zurmuhl showed in1930 tliat pitch is also to a lesser degree dependent upon intensity.

Most textbooks of physics identify pitch with frequency as if there
were no difference; yet, if that be true, what was ft that Galileo discovered?

Resonance and Harmonics. Even though the story of Galileo’s

sudden insight into the principle of the pendulum, as he watched
the swinging lamp in the cathedral at Pisa in 1583,

may beapocryphal, atiU there is Galileo’s own word for it that many times

he had observed in the swinging of lamps in churches—how eachlamp had its own rate of vibration, depending upon its lengthand not at all upon the amount of its excursion. Thus Galileo
conceived the notion drat objects may have natural periods of vibration, and this principle of the pendulum may be transferred to

the vibrating sti'ing. He even represented consonant intervals bysuspending from the same horizontal rod pendulums 16, 9 and 4
units long, so that they would vibrate wii rates proportional to4, 3 and 2. If such pendulums start in coincidence, they fall into

coincidence again at every second beat of the longest (or every
fourth beat of the shortest), illustrating the consonant relationsof the octave (4:2), the fifi (3:2)
It was Mersenne

and the fourth (4:3).

who noticed that a vibrating string produces

overtones, that, as the fundamental pitch fades out, highercom-

ponents of the sound sometimes emerge. Descartes suggested tohim that these overtones might result from the string’s vibratingin parts, each part on its own account, but Mersenne had no conclusive proof of what was going on in the string.

Not until 1677 was this matter deared up. Then John Wallis described and discussed two independent experiments that had been

made at Oxford in 1673, one by William Noble and the other by

HARMONICS

325

Thomas Pigot. Wallis first noted the fact of resonance in strings;
if two strings

be tuned to the same pitch and one be plucked, theother is thrown into vibration. He also observed that a string will
vibrate if its pitch is sounded on an organ, and he repeated fromhearsay the story that "a thin fine Venice glass cracked with thestrong and lasting sound of a trumpet or comet near it, sounding
in unison” with the natural tone of the glass.

The discovery of

Noble and Pigot was that when consonant strings, not in unison,
are together, the sounding of the shorter will cause the longer
to vibrate in parts—as they noted bywrapping a bit of paperaround the string and moving it along to different points so thatthey could easily see the vibrations. Wallis satisfied himself thatthe string always divides thus into aliquot parts—halves, thirds,
quarters, etc., responding respectively to the octave, the twelfth,

the double octave, etc.

Joseph Sauveur ( 1701 ) rounded out and established the theoryof overtones, coining the words fundamental to apply to the basic

frequency and harmonic for the overtones that are even multiplesof the fundamental. The harmonics can be brought out, he showed,
if a vibrating string

be touched lightly at some even fraction of its

length, that is to say at a node, as he called the point that divides

from each other the separately vibrating parts of the string. If thestring be touched at one-third of Us length, for instance, then its

fundamental frequency is damped, as are also the second, fourth,fifth,

seventh, eighth harmonics; but the third harmonic (alongwith the sixth and ninth) remains strong, sounding the pitch

which corresponds to three times the frequency of the fundamental. This discovery meant tiiat the harmonic overtones of afundamental frequency are really parHah, as tliey were named
later by Helmholtz; that is to say, the total vibration of the stringisto be regarded as the sum of all these partial vibrations goingon simultaneously. Although the upper partials may not be heard
in the total mass of sound, they come out clearly when the lower

components have been damped out by Sauveut’s method. Thus it
was more than a century after Salinas had prescribed meantone

temperament for organs before the physics of harmony was understood well enough to furnish the valid argument for just temperament.
Analysis. In 1822 Baron Fourier,’French statesman-scientist-

mathematician, made, in the course of a study of the theory

PSYCHOPHYSICS OF TONE

826

of heat, a remarlcable mathematical discovery. He found that any

continuous function or curve, no matter what its shape or how
irregular (provided it does not return on itself), can be represented
as the sum of a series of sine curves, in which the separate terms

vary in length (period), in height (amplitude) and in phase relation to one anodier, and in which&e wave-lengths are even frac-

tions ( 1/2, 1/3, 1/4, etc. ) of the wave-length of the function being

represented. He proved that this infinite series is convergent: theoriginal function can be represented with any degree of approxi-

mation by adding enough terms in the series. In addition heshowed that there is possible no other such general analysis.
Because it provided a mathematical theory of the vibrating
string, this discovery

had presently a great effect upon physicalacoustics. While Sauveur had made it certain that a shing vibrates—as a whole, in halves, inin a great many different ways at once
thirds, etc.

—

^noone had made it dear how the composition of somany modes of vibration takes place. Now Fourier’s series provided an analogue; the pattern of the vibration would be the pattern given by the algebraic sum of all the harmonic (sine) com-ponents that represent the various harmonics involved. Nor was
this new principle only synthetic; it was also analytic, for it showedthat any periodc motion at all can be reduced to the sum of a seriesof simple harmonic vibrations. In the case of sound the demonstration of Fourier’s theorem meant that any irregular wave, no matter

how it has been produced, can be regarded as complex, because it
can be analyzed into sine components. If the form of the soundwave is known, then the analysis can be made mathematically by
the application of Fourier’s series; or the same components can be
identified by resonance if an adequate series of resonators is available.

A resonator—be it pendulum or taut string—has a natural

period of simple harmonic vibration with which it responds to thesame vibration occurring elsewhere, either simply or as a harmonic
partial of a complex motion. In other words, analysis by resonanceand by Fourier’s series must, by the identity of their natures, givethe same result

This kind of analysis was given a psychophysiological meaningby G. S. Ohm in 1843. (This was the Ohm who lent his name tothe law of simple electric circuits and to the unit of electrical re-—

Ohm argued—quite elaborately and at length that for
any complex wave-foim ffie ear hears out’ tiie simple harmonicsistance.)

OHM’S LAW

327

components, the same components that Fourier’s analysis or reso-

nance would give. Ohm’s acoustic law thus asserts that it is possible
to pay separate attention to the simple harmonic components ofany irregular sound wave. The law has been generally accepted.
Providing the basis for Helmholtz’s resonance theory of hearing,

Ohm’s law along with Helmholtz’s theory dominated all theoretical
discussion in the field of audition for at least sixty years (1863et seq.

) .

It seemed for a time as if the law broke

down in the caseof difference tones, but now it is realized that these difference com-ponents are added by distortion in the ear and that the hearing ofthem further substantiates the law. All in all, the analysis of irregularwave-forms into harmonic components remains the obvious

and important fact about the perception of tones.
So laborious is the mathematics involved in the use of Fourier’s
theorem that various machines have been invented to lessen thelabor.

Lord Kelvin invented a mechanical harmonic synthetizer(primarily to use in predicting tides) in 1872 and a harmonic analyzer in 1876,and other and better machines have been built

since. If it is a sound which is to be analyzed by such a machine,that sound has first to be turned into a curve by an oscillograph.

This process has, however, changed since the development of thethermionic vacuum tubes in connection with the radio. Nowadays
the sound is turned into an electric wave which is analyzed byelectric resonance. Wave-analyzers are built so that an amplifier

can be tuned to respond to one or another of the components of
the wave and the strength and frequency of each component readoff from a dial.

Sometimes the question is asked: Why is an irregular wave-form
called ‘complex’ when its ‘components’ usually have never had inde-

pendent existence until they are separated by analysis? D. C. Miller
has published the Fourier analysis of a girl’s profile into the sum ofei^teen sine curves; are these ‘components’ really parts of thegirl’s face?

The obvious answer is that an irregular periodic curveis ‘complex’ in the sense that it

can be analyzed into harmonic com-ponents (a) mathematically (Fourier’s series), (b) physically(resonance), and (c) psychophysiologically (Ohm’s law) with ap-

proximately the same results—presumably because Fourier’s series
gives the results of resonance and because the ear aotj like a resonator. There is, however, beyond thisobvious answer, an historicalreason as to why it is natural to identify wegMlor with complex in

328

PSYCHOPHYSICS OF TONE

dealing with sound waves, The order of discovery was synthetic,

not analytic. Galileo was sure about the simple natural periods ofstrings Eist. It was only later that Sauveur established the fact of

the compounding of these different partial vibrations. The irregular wave-forms were first known as compounds and not until later

as irregular. It was a full century after Fourier before anyone realized that (on account of subjective harmomcs)

a pure tone is sorare as to be almost non-existent, ihat tones are in fact nothing

more than ideal analytical elements, primarily useful for simplifying description.

Apparatus. There were many sources of tone in the nineteenth
centrary. The siren had the advantage of being easy to control andcalibrate, since its frequency is simply the number of holes passing

the air-jet in a second. The tuning fork was most precise as to fre-quency, the most elaborately developed, the most elegant. The
resonator Increased the fork’s intensity and assured its purity. Or-

gan pipes operating on large wind-chests and reed tonometers withsmall wind-chests of their own were employed where purity oftone was not desired. Blown bottles were often used, while theStein variators, which were brass bottles with piston bottoms, pro-vided the best method for continuous change of frequency. The

Gallon whistle and the Koenig cylinders (short suspend^ bars
struck with a metal hammer) were used to determine the upper
limit of hearing, and lamellas and wire forks for the slow frequencies at the lower limit. The most famousmakers of these instru-

ments were Antoine Appunn and Rudolph Koenig, both of Paris.

Koenig was closely associated with H^holtz: he built Helmholtz’s ideas into apparatus, and Helmholtz built at least one pieceof Koenig’s apparatus (the vowel synthetizor) into a theory.

The siren was developed before the tuning fork. If pitch be frequency, as Galileo had seemed to show, then the way to get a pitch

would be to create a frequency. That is essentially what Hooke
did in 1881 when he let an object sbike the teeth of a revolving
wheel! given the number of teeth and the speed of the wheel, thepitch is known. A better method, however, is to have a blast of air
strike a series of holes in a revolving disk; such a device is a siren.

Cagniard de la Tour, who made the first siren in 1819, empbyed

two superposed horizontal disks, with corresponding rings of holes.

The lower disk was fixed to a wind-chest; the upper could rotate
above it. The holes of the two disks were drilled at different an^es.

ACOUSTIC APPARATUS

329

so that the air, coining through the holes of the lower dish, caused

the upper disk to rotate and thus to interrupt the air stream regularly.

This type of siren was later perfected by Helmholtz andKoenig, Another type, invented by Seebeck in 1841, consisted of asingle rotating disk, mounted in a vertical plane and with an airblast directed at sets of holes drilled circumferentially in rings

around the center. Later these disks were made up by Koenig andother instrument makers to illustrate a great variety of tonal phe-nomena.
Shore’s invention of the tuning fork (post 1714), we have al-

ready noted along with Scheibler’s tuning-fork tonometer (1834)

and Marloye’s putting of resonance boxes on tuning forks (1839).

The triumph of the tuning fork was, however, chiefly the achievement of Rudolph Koenig (1832-1901) who, taking over Marloye’s
instrument business in 1858, devoted his life—unmairied and making a shop of his house on the Isle St. Louis in Paris to the manu-—

facture of acoustical apparatus of a precision and quality that madehis tuning forks the revered possessions ofmany laboratories

throughout the world and a classical tradition in the psychologicallaboratories. ’The height of Koenig’s fame was readied when, in

1876, he exhibited at the Philadelphia Centennial Exhibition where

he received a special dtation of honor, a gold medal, and the plaudits of the scientists,

who tried with imperfect success to raise

enough money to purchase his apparatus for the United States. At
the exposition he exhibited 070 tuning forks, ranging from giant
forks for 16 c.p.s,, five feet high, weighing 200 lbs, each, and having

resonators eight feet long, down to the small forks for the upper
limit of hearing near 20,000 c.p.s. At home hesale

had—it was not for—a precision tonometer, modeled after Scheibler’s but more

extensive and more accurate. It consisted of 150 forks ranging from

16 to 21,845 c.p.s.
Koenig’s finest instrument was his clock-fork, made for the pur-pose of calibrating other forks by ultimate reference to a standard
clock. It was a clock with its escapement engaged, not by a pendu-

lum, but by a tuning fork. The frequency of this fork could be de-termined with an error of less than 0.0001 c.p.s. by comparing thedock that it drove with a standard dock over a period of several
days. (The fork would make more than 16,000,000 wibrations inthree days, ) One prong of the fork carried the objective of a mi-

croscope whose eye-piece was fixed immovably to the frame of the330

PSYCHOPHYSICS OF TONE

apparatus. The fork to be tested was set at right angles to thestandard fork, and a spot upon it viewed through the microscope
while both forks were kept vibrating. This arrangement forms a
Lissajous comparator; the application of the principle to the calibration of forks was Helmholtz’s idea, If the two forks are exactly
in unison, then the double motion causes an observer to see
ellipse (or the limiting cases ofanan ellipse, a line or a circle)

through the microscope. If the frequencies differ, then the Lissajous figure moves across the field, and the difference in frequency

can be determined from its rate.

What else did Koenig do? He constructed a manometric flame
apparatus for viewing acoustic wave forms. He invented the adjustable resonator and the wave siren. He assembled the famous
set of tuning forks for synthetizing clangs by controlling the in-tensity and relative phase of ten harmonics—the apparatus that

Helmholtz used, as he thought, to spthetize vowels ( Fig. 51 ).

He

improved the phonautograph (invented in 1857) before Edison
got at it and improved it more. With Helmholtz he devised theelectromagnetic control of tuning forks (ca. 1860), the means bywhich a fork is kept in continuous vibration. But mostly he madebeautiful accurate forks and other acoustic instruments, working
as an artist works, without a primary motive of profit, putting whatmoney he made back into further creation or experimentation.
The tuning fork was valued because it gave an approximately—^provided

pure tone of accurate pitchit

was not struck too vigor-

ously. The fork, however, had the disadvantage that, while accu-

rate as to frequency, it was not easily controlled in intensity. Psychologists of the nineteenth century, however, stressing sensory

quality as more important than intensity, scarcely recognized thisgross defect. It is true that they could control intensity after afashion by stopping off the fork’s resonator; yet the studies ofWeber’s function could not be made with forks at all. For such research they had to depend upon the noise of steel balls falling on

an ebony plate or of a hard rubber pendulum dropping against an
ebony block, not (as nowadays) upon energy measured at the ear.

By the development of the thermionic vacuum tube the twentieth century presently changed all this. Althou^ this is not flieplace to tell adequately the history of that development in physics,
the chief of many events were these, Guthrie ( 1873) found that aball heated to a white heat discharges a positively charged elec-

ELECTRICAL TONES

331

troscope. That is because hot metal emits negative charges in theform of electrons. Edison found (1883) that a current will flow
between a metal plate in a lamp and the positive end of the lamp’s

Fig. 51. Koenig’s Forks foe ihe Synthesisof Clangs

Ten folks, the first ten harmonics of 128 c.p.s., each with a resonator andall actuated electromngnetlcally by a 128-c.p.s. master fork (shown at therear right of the apparatus) which is property placed in another room. The
keys control stops in front of tlie resonator openings. Various timbres canthus be created synthetically. Helmhollz used the apparatus in his attempt
to syntlietize vowels.

filament if the two are connected, because the positively charged
plate will attract the negative electrons from the hot filament; but

no such current will flow from the plate to the negative pole of thefilament. By 1896 Fleming had utilized this principle to make avalve through which a current would pass only one way.

—

Fleming valve rectifies an alternating current

The

rectification being

PSYCHOPHYSICS OF TONE

332

the first important function (except for the ordinary incandescentlight) that vacuum tubes provid^.

grid to the tubes.

De Forest (1907) added the

A weak voltage impressed on the grid controls

the facihly with which a strong current flows through the valve.

Thus the strong current takes on the wave-pattern of the weak
voltage, and the weak voltage is said to be ampUSed. Amplificationis thesecond important discovery. No other advance was so im-

portant until the discovery of oscfflafion in 1913 when several men—there were

five claimants of priority for this idea

—thought ofleading the amplified current back through a tuned circuit to thegrid. Tlie electrical properties of the circuit give it a natural periodof resonance, so that the amplifier “boosts” itself periodically at therate to which the circuit is tuned. Oscillation of a precision that

Koenig would have envied is the result. After 1913 the improvements in this field of physics, greatly stimulated by radio broadcasting which began about 1921, have been numerous, but mostly
in the direction of greater range and stabflizalion of the funda-

mental processes just described.

Thus it came about that the radio age unfrocked Koenig in his
sanctum, the psychological laboratory. Nowadays the audio-oscillator replaces the tuning fork. Intensity, being easily controlled,

has at last become an important variable of the stimulus. The
psychologist can now get any frequency at any intensity in the perfect quiet of an electrical potential, changing it at need into soundat the ear-drum by means of ear-phones or a loud-speaker.

The Limits of Hearing
The musical scale is limited. It is a series of pitches picked out
arbitrarily from a much longer series. Although it is true that there

are deep rumbles below the bass of the organ and shrill whistles

above its treble, yet the series does not continue on indefinitely ineither direction. Frequency, on the other hand, falls into an infi-

nite series, for there is no rate so slow that there might not be aslower, nor so fast that it could not be faster. So it was that, when
Galileo established the dependence of pitch on frequency, he alsofrequencies-t-limits which the scientists ultimately undertook todetermine. Sauveur in 1700 was the first; by a study of organ pipes
he set the lower limit at 12.S o.p.s. and the upper at 6400 c.p.s.; but

LIMITS OF HEAEING333

the concentrated attack upon the problem did not come until muchlater.

During the nineteenth century there was a score of determinations of each of these limits. What sb'ikes

one first in reviewing

them is their variability. The lower limit was set as low as 8 c.p.s.
(Savart, 1831) and as high as 48 c.p.s. (Despretz, 1845). The up-

per limit was set as high as 55,000 (Bezold, 1897) and as low as4096 ( Biot, 1817).

From the lowest lower limit to the highest upper

limit is almost thirteen octaves, whereas

from tlie highest lower

limit to the lowest upper limit is less than seven octaves. Many ofthe values for the lower limit, however, fell between 16 and 20
c.p.s,,

and for the upper limit between 20,000 and 25,000

—a

total

range from lowest to highest of about ten octaves, which has been
only slightly reduced by the more accurate work of the twentiethcentury.

There were three sources of error in the work of the nineteenth
century, (a) The limits of hearing are not clear cut. It was hardto decide when the successive throbs of a faint rumble became

the full continuity of the lowest tone, or when the tiny bead of

the highest tone faded out in the swish of the blown whistle, (b)The harmonics made no end of trouble. One might hear an instrument calibrated for 8 c.p.s. because the second partial (16c.p.s)

was present, or the fourth (32 c.p.s,). At the upper limit

the harmonics, which, being inaudible, might have been supposed
to be safely out of the way, might nevertheless affect the calibration.

The limits in the neighborhood of 50,000, found with theGalton whistle around the year 1900, had twice their proper frequencies because the whistle, calibrated by the Kundt dust method,

impressed on the dust the pattern of the second harmonic insteadof the first. The second harmonic was more intense than the first(as the dust showed), but the first was louder than the second( tothe ear, which could not respond to the second at all).

(o) Andthen error was inboduced because intensity could not be accurately controlled, although, as we now know, the range of hear-ing increases with increase of intensity.

Sauveur set the lower limit in 1700 at 12,5 c.p.s. because he decided that the 40-ft. organ pipe was the longest to give a continuous sound which was nOt the successive throbs of a fumble. BothChladni (1802) and Biot (1817) put the limit at about 16, eachbasing his judgment on the observation of the tones of organ pipes

,

PSYCHOPHYSICS OF TONE

334

and of weighted strings. In 1831 Savait, having reduced his
toothed wheel to a rotating hub with two spokes which he let hit
against cards or thin boards, concluded that he heard a continuous low tone at seven or eight strokes per second; accordingly, he
set the threshold there. Despretz (1845), on the other hand, withthe same instrument fixed the limit much higher, perhaps as highas 48 c.p.s. None of these investigators, however, had excluded thepossibility that theupper harmonics were heard instead of thefundamental, a neglect which accounts for the lowest values found.

Of the problem of the harmonics Helmholtz was fully aware.
First (1863) he put the limit at about 37 c.p.s., observing the toneof a weighted string which had, besides the fundamental, only

high harmonics from which he thought he could abstract. Later(1870) Koenig liad made him a giant fork, which—so it seemed—gave a low tone near 30

to himo.p.s.

Preyer for his part used

loaded reeds (1876) andaforkmadebyAppunn (1879) to estab-M

16 andc.p.s. Later Appunn
made a lamella, a steel tongue gripped in a vise and caused to vilish the limit variously between

brate by being pulled to one side and released. It tended to givevery low values; Wundt (1893) reported 8 o.p.s.

Another scheme for getting rid of harmonics was to use difference toiies. The 8-ft organ-pipe fear C= 64

o.p.s, and the pipe for

D = 72 o,p.s, gave, according to Wundt’s observation (1874) asingle difference tone which corresponded to 8 o.p.s. Preyer ( 1876 )

employing the difference tones of reeds, put the limit near 20
c.p,s.

The method was, however, not safe, because, even thou^difference tones may have no harmonics, the harmonics of theirgenerators have difference tones. The second harmonics of Wundt’s

pipes of 64 and 72 c.p.s. would have had a difference tone of 16c,p.s,, and the fourth harmonics a difference tone of 32 c.p,s.

The story of the attempt to establish the upper limit of hearing
he could get was from a pipe

is similar. Because the highest pitchthat was%4 as long as his standard organ pipe for 100 c.p.s.,

Sauveur (1700) set the limit at 6400 c.p.s. Most of the early results with organ pipes were too low(Chladni, 1802, 8192 c.p.s.;

Biot, 1817, 4096 o.p.s.), for the reason that an organ pipe is not

adapted to give the highest audible pitches. Savart, using a wheelwith 720 teeth against which he held a card or thin wooden wedge(see Fig, 52), set the limit at 24,000 c,p.s. or higher. That wasmore nearly correct, for the frequency was determined by the

LIMITS OF HEARING

335

number of teeth and the speed of die wheel, and the many upperharmonics were inaudible. Much later Koenig built the short sus-pended steel cylinders which, when struck with a metal hammer,
give off a tiny tsead of tone in the midst of the thud from the ham-mer. These gave 20,000 e.p.s. for the upper limit (Turnbull, 1874;
Blake, 1878). Then Appunn made a set of high forks for this purpose, but unfortunately they were incorrectly calibrated and regis-

Fic. 52. SAvaitt's Warn, (1830)

A card or wedge of thin wood was held against the rotating teeth, anda note was heard, increasing in pitch as the wheel was speeded up, As there
were 720 teedi, 33 r.p.s. would give 24,000 c.p.s., whim Savart set as thelowest value of the upper limit of hearing. The picture is from W, H. Stone,
Elementurp Lessons on Sound, 1879, 78.

tered much too high. Preyer (1876) got with them a limit of 40,-960 c.p.s.

For forty years after 1880 the Galton whistle was die standard
instrument for the upper limit. Francis Galton first described thewhistle in 1876. It was calibrated for frequencies from 6500 to

84,000 c.p.s. Galton contented himself with showing differencesin the audibility of the high tones for persons of different ages

and for different kinds of animals. With the whistle built into theend of a cane, he used it on the streets and in zoological gardens.
There were several determinations of the upper Ihnit with theGalton whistle from 1878 to 1897, all in the region of 20,000 o.p.s.
for young people and less for older persons. Then Eddmann madean improved form of the whistle, in which, however, as we havenoted above, some of the calibrations were defective in that they

PSYCHOPHYSICS OF TONE

Q36

depended upon the second harmonic. The result was that thelimitswere found either in the region of 20,000 to 25,000 or of

40,000 to 50,000, but not in between. As late as 1910 Titchener

could state that the upper limit is 50,000, but by 1920 it was pretty
well recognized that 20,000 c.p.s. is nearer the truth.

Now the fact is that the extreme frequencies for hearing depend

50

200

100

400

600

1600

3200 6400

12600

FREQUENCY
Fig,

53 Wien's AuraBajnr Ccbve ( 1903 ).

The function shows the idatian of the sensitivities of the eat (ledpiocalsof threshold intensities) at various hequencies. The curve is analo^us to
the luminosity or visibility curve in vision.

upon intensity, although intensity was not carefully controlled inany of these experiments. Some investigator with a happy insightmight, even before Galton invented his whistle, have put two andtwo together and seen die difficulty, for as early as 1870 Toepler

and Boltzmann had found that auditory sensitivity is low at theextremes of the audible range and very high (actually rivaling
the eye) in the musical region of frequencies. Lord RayleighAUDIOGRAM

337

showed in 1894 how the minimum current audible in a telephonevaries when the frequency changes from 128 to 768 c.p.s. Then

Wien in 1903 determined an audibility curve, i.e., the function forauditory sensitivity that is analogous to the luminosity curve forvision (see pp, 177-182). Wien generated his sounds electrically,

rendering them phonic with a telephone receiver. He could easilytell how much electrical energy he put into the receiver, but hehad to determine the sensitivity curve of its diaphragm before hecould state what energy had been delivered to the ear. He did,

however, in this way deteimine the absolute intensitive thresholdof hearing at frequencies ranging

from 50 to 12,000 c.p.s. The

audibility curve of Fig. 53 is his plot of the reciprocals of thesethreshold energies, showing maximal sensitivity near 2200 o.p.s. It

took nearly twenty years for the significance of tliis research to

become apparent.
About 1922 the Bell Telephone Laboratories, under the directionof Harvey Fletcher, began a long and valuable series of investi-

gations in psychophysical acoustics. They developed the modern

audiometer, an instrument using thermionic oscillators and de-signed so tliat the intensity of each of a large number of different
frequencies can be varied from inaudibility up to an intensity sogreat that tactual sensations, generally unpleasant, are elicitedby the sound. The intensity at which these tactual components are
introduced was called the threshold of feeling. One of the first
papers making use of this apparatus and these terms was hy Wegel(1922). Having determined minimum audibility or the thresholdof hearing at various frequencies for a representative set of observers, he plotted the averages as in the lower curve of Fig. 54.

He also determined the values for the average tirreshold of feeling, the upper curve of the figure. It will be noted that these two

curves cross at each end, enclosing an area in which lie all normal—sounds^forbeneath the lower curve the sounds are normally in-audible and above the upper they are so loud as to be uncomfortable. Wegel proposed to see how much this area of normal
sensitivity is reduced in a given case of auditory defect, and whatpart of it is lost, tlms coming at both a quantitative and a qualitative description of auditory deficiency.

As a by-product of the creation of the audiogram Ifae problemof the hmits of hearing received a new solution. The lower curveof Fig. 54 defines, not only the threshold for intensity at any fre-

PSYCHOPHYSICS OF TONE

338

quency, but also tlie two limits of frequency at any intensity, Thus,
reading the curve horizontally, we see that the upper and lower
limits of hearing at various intensities are approximately as follows:

At .001dynespersq.cm.,lowerlimit=880ep.s., upper limit= 6,500c.p.s.
““'" =180,=12,400
At .01
,
“
“ “ “
"
"
"
“ ,
At .1
74
=17,500,"“““" =19,000.
32 “ ,
At 1.
“
‘
“
“
“
“ =20,000
20
At threshold of feeling,===

Wegel’s data in this way tended to fix the maximum range ofhearing (without feeling) at the limits which emerged from the

FREQUENCY (!:.P.S)AND MUSCAL NOTATION
Fig. 54. Wegei's AuniOGRAM (1922)

This drawing is for Wegel’s data as drafted by Fletcher (1923).

old determinations—20 and 20,000 c.p.s.
investigations have, however,Numerous subsequentchanged the form of these early

curves, especially the function for the threshold of feeling. Somestudies have made it appear that frequencies well below 20 c.p.s.

may be audible at intensities which are still below the thresholdof feeUng. Such details get settled only with time. The important

modem advance in 4is matter of the limits of hearing was thediscovery that frequency thresholds and intensitive thresholds can-not be considered separately. There are more loud pitches thanfaintDIFFERENTIAL SENSITIVITY FOR PITCH330

The curve for the absolute intensitive thresholds shows that theear (like the eye; see p. 182) is indeed a very sensitive organ. Thofunction obtained by Wilska in 1935 showed that at 3600 c,p.s., thefrequency at which sensitivity was greatest, a tone could be heard

when the drum-sldn of the ear moved only 4.6 thousandths of amillionth of a millimeter (4.5

X 10"‘“ centimeters). That ampli-

tude of vibration is less than two per cent of the diameter of a molecule of hydrogenl

Differential Sensitivity

The fundamental problem of what range of frequencies is audible was supplemented fairly soon by the problem of differential
perception; how many tonal differences are discrimlnable within
the audible range? That this quffition should be raised first withrespect to pitch was natural, since pitch was the dimension forwhich the limits had been determined. Loudness was not until
recently a primary differentia of tone, and, moreover, loudness

could not in the early days be controlled so as to form a satisfactory basis of investigation. Later, of course, with the rise of theinterest in Weber’s law, the loudness of noises was studied; andthen finally after 1920 the thermionic tubes made it possible ao
curately to control the loudness of tones.

Apparently the first experiment on the differential threshold forpitch was made by Sauveur in 1700 when he decided that a changeof )4odo

the length of the string of a monochord makes a dis-tinguishable difference in pitch. That difference is very small, be-ing less than one musical cent (of ^ semitone in equal tem-

perament); yet it is no less than the limen that Luft found laterin the region of 500 c.p.s. Sauveur did not say to what frequency
his string was tuned.

In 1827 Delezenne, studying die musical intervals, took underconsideration the statement that the major and minor tonal intervals of just temperament are not noticeably different.

He had astring which was 1147 mm. long and which vibrated at a rate of 120
c.p.s. At its exact middle he placed a moveable bridge, so that hehad two halves, each vibrating at 240 c.p.s. By moving the bridge
1 mm. toward one end, he got from the two halves of the string
tones that were just barely distinguishable by a person with a‘delicate’ ear

who shut his eyes and avoided all distractions. A

2-mm. displacement of the bridge gave a difference readily ap-

PSYCHOPHYSICS OF TONE

340

parent even to unpracticed observers. In other words, at 240 c.p.s.
the threshold for unpracliced observers is about .84 c.p.s., whereas
the extreme threshold under the most favorable circumstances isabout .42 c.p.s. It interested Delezenne that even tire greater ofthese just noticeable difference is equivalent to only about half

a comma, the comma being the difference in interval between the

major and minor tonal intervals (see p. 317). Hence he concluded
that these two basic intervals of just temperament are distinguish-

able even to unmusical persons.

There were after Delezenne several casual determinations ofpitch discrimination, Seebeclc, for instance, in 1846 put the thresholds at .36, .30 and .50 c.p.s. for 440, 500 and 1000 c.p.s., respectively, and Preyer, using Appuim reeds in 1876, verified these lasttwo quantities. There was, however, no systematic determinationof the limen as a function of frequency until Luft, in Wundt’s
laboratory in 1888, used tuning forks to get the differential thresholds for frequencies ranging from 32 to 1024 o.p.s. His thresholdvalues were all very small; they lay between .15 and .44 c.p.s. Max

Meyer in 1898 found comparably small values for Stumpf’s ear.
So for a time it was the general belief that the differential hmen,
at least in the middle of the musical range, is less than half a cycle

per second.
Later the linens got largerl Vance with tuning forks in 1914 re-ported values more than ten times the size of Luft’s, just as Stiioker
in 1907 had also found large Hmens. Then, with the substitution of

the thermionic tubes for the tuning forks, the Hmens seemed toget a little larger still. The determinations of Shower and Biddulph(1931) are the standard for this last period of investigation. Herefor comparison are three classical determinations of the threshold(in c,p.s.):Standard frequency:

62

125

2S0

500

1000

Luft (1888)

•le

.16

.28

.25

.22

.36

8,40

1.40

1,40

1.80

8.80

5.70

2.64

3.10

2.64

2.60

3.60

3.80

Vance (1914)
Shower & Biddulph
at 40 £b, (1981)

2000

That these discrepancies are a function of the method of investigation seems now pretty clear. There are great individual dif-ferences in sensitivity, due to differences in the sensitivity of theeat

and also in practice. Practised musical observers generally

have small limens. Because they were averages of a group, Vance’s

DIFFERENTIAL SENSITIVITY FOR PITCH

341

limens are too high to represent maximal sensitivity. Luft’s Umens,on the other hand, are plainly much too low, and this for the foL
lowing reasons. His two tones for comparison were not well controlled, because he used hand-struck tuning forks, a technique thatfavors differences. He used, moreover, the method of limits, inwhich differences of any kind tend to be reported as differences in
the fundamental pitch, and so to make the limen smaller. Vance

used a method of constant stimuli where this error does not occur.
Hand-struck tuning forks, furthermore, have in them a pattern ofovertones or transient tones, many of whicli are the pitches forwhich the ear is most sensitive (around 2000 c.p.s.), although thefundamentals may be lower (30-1000 c.p.s ). In such cases the observer may make a discrimination of these higher transients thatlie in the region most sensitive to difference of frequency, with theresult that the limen comes out too low. Shower and Biddulph tried
to get away from this difficulty by arranging to have the electricalfrequency, which generated the tones, changed gradually in ac-

cordance with a sinusoidal function from the one frequency to theother. That method, to be sure, minimized the transients and con-sequently raised the limen, but it also introduced another artifact,
for it is harder to observe continuous change than abmpt change.

Presumably maximal sensitivity is represented by limens some-what smaller than Shower and Biddulph’s, and yet larger than
Luft's.

When the differential thresholds are known, it is natural to try
to count the j.n.d. of pitch. The total number of j.n.d. has some-times been considered important for Helmholtz's resonance theoryof hearing,which required a separate resonator with its inde-

pendent nerve-fiber for every discriminable pitch. In 1863 Helmholtz could note only that the rods of Corti might be the resonators,
since the 3000 rods would provide fifty resonators for every semi-

tone within the seven musical octaves, leaving over 200 for theupper ranges. That was not quite enou^ rods, for Helmholtz took
the differential limen of pitch to be about %ooo, which he figured

would require some 64 discriminations per semitone. Thus he concluded, just as he had previously in his color theory, that inter-mediate qualities must depend on the ratio of excitation of adjacent receptors. Such reasoning seems to be necessary when thequalitative differentiation of sensation exceeds the spatial differ-entiation of the sense-organ. By 1870 new histological researches

342

PSYCHOPHYSICS OF TONE

had improved the situation, for Helmholtz could then say that
there were 4500 outer rods of Corti or seventy-five per semitone,
and also that the basilar membrane was probably the resonator.
It was Kiilpe who in 1893 took Luft’s determinations and com-puted the total number of j.n.d. at about 11,000, a total for which
the 4500 rods of Corti were clearly too few. Kiilpe noted, however,that there are in the inner ear between 16,000 and 20,000 hair cells
to which the nerve-fibers run,and that is, of course, ample an-atomical differentiation to take care of 11,000 tones, Nowadays it
appeal's, because Luft’s hmens are too small, that 11,000 pitchesistoo large a requirement for maximal sensitivity. On the other

hand, the 1500 j.n.d. provided by Shower and Biddulph’s data arepresumably not enough, The minimal differentiation of the ear

must lie somewhere between these two values, presumably nearer
the smaller.
Differential sensitivity to acoustic intensity is the second princi-

pal psychophysical problem in hearing, At first it was not recog-

nized as important, but, after the impetus given the investigationof Weber’s law by Fechner's publication of his Elemenie der Fsy-

chophysA in 1860, this threshold received its share of attention.
Because at the start there seemed to be no good way of controllingthe intensity of tones, the first work had to be done with noise. It

was assumed that the intensity of noise is proportional to the heightof the fall of a ball upon a plate, or, if the height be kept constant^to the weight of the ball. The first standard apparatus was thesound pendulum of A. W. Volkmann, which Fechner described. It
consists of a pendulum-hammer which has a hard rubber ball for ahead and which can be allowed to drop from different angles of
elevation, swinging against an ebony block at the base of the sup-port of the pendulum. Later a double pendulum was made: two

pendulums, one on each side of the block, arranged so that they
could be released in quick succession to provide a pair of loudnesses for comparative judgment. There iso came to be used a“fall apparatus," which

Wundt presently standardized. This was aframe carrying at variable heights several electromagnetic releases.
so arranged that steel balls could be dropped upon iron or ebony
plates, striking once and then being caught in a padded box.

The first determinations of differential sensitivity for loudness
were made by Renz and Wolf (1856) working under the directionof Vierordt at Tubingen, Their research, the second to employ theDIFFERENTIAL SENSnTVITY FOR LOUDNESS

343

method of right and wrong cases ( as the method of constant stim-uU was then oaRed), was primarily concerned with the establishment of this new method, which Vierordt had invented. As stimulus
Renz and Wolf used the sound of a ticking watch, varying the intensity by changing the distance. Their results (the average forthe two of them ) were these:
Ratio of two intensities

Per cent of right judgments

1000:920

1000:840

1000:778

1000:716

S4.9

85.1

86.1

100.0

These frequencies are, therefore, one of the first psychometricfunctions ever obtained. They show the threshold ( the point where

the function would be 75 per cent) at a ratio of about 1000:870,
i.e., a difference of

13 per cent.

More than twenty years later this experiment was repeatedby Norr, who also worked in Tubingen under Vierordt with themethod of constant stimuli. He dropped lead balls on an ironplate, using intensities ranging from 2500 to 800,000,000 milligram-millimeters.

He got a threshold (75 per cent of the judgments

right) at about 5 per cent of the stimulus intensity. Because thisvtJue did not vary greatly throughout this range, he concluded
that he had verified Weber’s law.

When Wundt’s laboratory was formally opened at Leipzig in
1879, it was natural that some of its energies should soon be turned
to testing the validity of Weber’s law. Thus there were, beginningwith Tischer in 1883 and ending with Kampfe in 1893, six studiesof the measurement of differences of auditory intensities, all but

one of them made at Leipzig. For the most part these studies
dealt, not with differential hmens, but with supraliminal sense-

distances. Three intensities would be set up and the middle one

adjusted until it bisected the difference in loudness between thefirst

and the third. Then, if the middle stimulus turned out to be

the geometi'ic mean of the two extremes, Weber’s law was sup-posed to be verified; but, if it turned out to be the arithmetic meanor something still else, then the test of the law was considered tohave failed. Inasmuch as Merkel (1889) got one result and Angell(1891) got the other, the research cannot be said to have beenconclusive.

Most of these investigators, however, also determined differenhmens, which were considered to have establi^ed Weber’s

tial

law for the middle ranges of intensity. The law is validated if theWeber fraction, the ratio of the magnitude of the differential

PSYCHOPHYSICS OF TONE

344

threshold to the magnitude of the stimulus, is constant, Lorenz(1885) got values for the fraction ranging from .25 to .38; Starke(1889), from ,08 to .13; Merkel (1889), from .04 to .08. What wasmeant by verifying Weber’s law was, usually, that the fractions
were all of the same order of magnitude when the stimuli were not,and that there was no clear major trend of the fractions as a function of stimulus-magnitude. Thus Merkel used stimuli ranging from
.5 to5000 with the fraction vaiying irregularly back and forth

between ,0385 and .0625. Such instability of die fraction was, ofcourse, probably the fault of the method. The height of the fall

and the wei^t of the ball determine the enei'gy delivered to theplate but not the acoustic energy that gets to the ear. There was,however, no better method in the early days.
After all, noises were used faute de mieux in this experiment.

Tones were the proper material if a method could be found for controlling their intensities. Such a method was invented, as we havealready seen, by Wien in 1889. With his telephone-and-resonator

technique he varied the intensity of a tone of 440 c.p.s. from a value
proportional to 1.6 up to a maximum proportional to about 10“,Wldiin these limits he determined twelve differential thresholds
for which the Weber fractions ranged from .108 to .350. Wien’sfunction Is much more regular than Merkel’s, and ten of his twelve
values are all under .178— a degree of variability which in thenineteenth century meant that Weber’s law had been verified.

With the introduction of the thermionic technique, Knudsen in
1923 arranged to have a variable resistance alternately shunted inand out of an oscillator circuit, in such a way that the observer
heard a tone fluctuating in loudness whenever the resistance wasgreat enough. As determining the differential threshold he chose

Sie point where the fluctuation could be just perceived, Riesz in1928 invented an entirely new method for the purpose of avoiding
the transients introduced by Knudsen’s technique. Having firstgiven the observer two superimposed frequencies, so close together
that only a single beating tone could be perceived, he then reduced

the intensity of one frequency until the beats disappeared. 'The

Weber functions of both investigations at die frequency of 1000
o.p,s.

are shown in Fig. 55. Knudsen’s results approximate thestraight horizontal line of Weber’s law more nearly than do Hiesz’s.

The minimal Weber fraction in one case is .09, in the other .06.
Thus all the results from Renz and Wolf to Riesz are consistent,

WEBER’S LAW FOR TONE

34S

with the conventional statement that auditory sensitivity is about
Vio.
^Using Shower and Biddulph’s data for pitch sensitivity (a maxi-

mum of 1500 discriminably different pitches) and Riesz’s data forintensitive sensitivity (a maximum of 325 discriminably different

Fig. 55.

Auditory Weber Functions of Knudsen (1923)

AND Riesz (1B28)

The BbscIssB-scale shows the intensity of the stimulus in decibels above
the threshold of hearing. The ordinate-scale is the Weber fraction, theratio of the differential threshold tothe intensity at which it is obtained.

These curves are for 1000 c.p.s.

loudnesses ), Stevens got a total of about 340,000 discriminably different tones. Luft’s and Knudsens data would have given ever somany more—presumably several million. Helmholtz, being ignorant of the all-or-none action of the nerve-fiber, made no at-

tempt to take special account of intensity in his theory of hearing.

The modern problem is much more complicated than was his.
The most recent finding for differential sensitivity in both pitch
and loudness is the work of Stevens, Morgan and Volkmann ( 1941 )who have shown that sensory quanta of fixed size fan be determined for each of these dimensions. Never, under their optimal
conditions of observation, did they find a sensory difference when

PSYCHOPHYSICS OF TONE

846

the inorement between tones was less than one quantum, and they

always did find a sensory difference when the tonal increment

was greater than two quanta. Under these conditions the psychometric function becomes, instead of a sigmoid curve, a straightline with abrupt corners at zero and 100 per cent.

Notes
Musical Notes

Physical Acoustics

On the history of the physics of

The text does scant justice to theelaborate and fascinating hislory ofsound and thus of the auditory stimu-

the establishment, as tonal elements,

1ns, see the histories of physics, al-thwof the notes of the musical scale. Seethoughthe histories of music; in patUculai,

briefy with acoustics. For an older

tegeneraldeal

but

Hawlcins, General History of thepoint of view, see W. Whewell, His-

Science and Practice of Music, 5 voL,
1776; C. Burney, A General History

tory of the Inductive Sciences, 1837,

of Music, 177e-1789, 4 vol., of whioh
there is a 1935 reprint, 2 vol. (seethere esp.

D. C. Miller, op. cit. Excellent but
condensed is A. Wolf, A History of
Science, Technology, and Philosophy

358, onin the 16th and 17th Centuries, 1925,

J.

I. 40-83, 288-294, 342Greek music); C. H. H.
Parry, The Eoolutton of the Art ofUunc, 1918, esp. 14-46 on the scales;n, Bk. 8 (also later eds.). Excellent
is281-289; Idem, in the ElehteenthCentury, 1939, 172-176. Rdevant is

H. V. Helmholtz, On the Sensationsof Tone, Eng. trans. from German,
annotate by A. J. Ellis, 2 cd., 1885,
esp. 234-249 (Helmholtz on the history of tonaliW), 310-330 and 421513 (Helmholtz and Ellis on scales
and temperament); A. J. Ellis, On

F. Cajorl, A History of Physics, 2 ed.,the bistoiy of musical pitch, I, Son.

Zloni

Arts, 28, 1880, 293-336, 400-403,
whl^ Is more detailed than the ap-

pendices to Helmholtz. The complex-

—the

1933,

72-78,

35-43,

104 f.,

141,283-289, 383 f.
Besides these secondary sources,see,on the vibration of strings andthe relation of pilch to frequency,
Galileo Gablei, Discorsi e dimostra-mathematiche intomo d due
nuooe scienze, 1638, 138-150 (endof dialogue I); or Eng. trans., Mathematical Discourses

Gonceming Ttoo

at-

New Sciences Relating to Mechanicis

topt to retain simple ratios while
gaining the variety of trampositioa

and Local Motion, 1780, 143-157,or the 1914 Eng. trans,, 94-103; M.

afforded by equal intervals

Mersenne, Traitez deiiy ofthe interval-problem— shown^isclearly by Elus,

who, in Helmholtz,
op. cU., 453-456, lists ISS intervals
less than an octave which have musical significance. Of them 121 haveactuaUy been used in musici

On standards of pitch, see Ellis in
Helmholtz, op. dt., 463^13.

On the caltotian of frequency,
see D. C. Miller, Anecdotal Historyof the Science of Sound, 1935, 9-14,
39, 41, 55-68.

sons et deslanature desmouvemens detoutesde corps, 1636, Bk. 1 and 3;
Harmonic universelle, contenant latbeorle et lajtractique de la muslque,sortes1636, Vol.

I.

The Traitez gives themost acoustical (the least musical)
information, but the Harmonie is themost frequently cited. In the volume
I have seen, the Traitez, althoughseparately paged, is hound behind thetlUe page of me Harmonie. Of course,

NOTES(1564-1642) antedates his
pupil Mersenne (1588-1848), although his delayed publication was
two yeais later. Galileo’s brilliant
argument for the Copernican theory
in 1632, after he had promised thePope in 1616 not to do it, brought
Galileo347

ous and thorough treatment of the

problem.

For Fourier’s theorem and series,
see J. B.

tiqve deesp.

J.

Former, Thiorle analy-

h chcdeur, 1822, Chap. 3,

sect,

(Eng.

6,

frarts.,1878).

me

Ohm’s acoustic law is to be foundin G. S. Ohm, Ueber die Definition

age of sixty-eight in 1633, and into
retirement under censure thereafter.

des Tones, nebst daran geknupfter
Theorle der Siiene urtd ahnlioher

He went blind in 1637, and sent the
MS of Two New Sciences, which hetonhlldenerhad by him, out of Italy to the Elzevirs for pinting in 1638. Four years
later he died. The stringed instrument which he used for resonating
to the squeaks of the chisel on thebrass plate was a cembalo, a general

On tonal analysis in general, bothhim before

the Inquisitionatterm probably referring in this casetosome antecedentofthe harpsi-

chord.

On the velocity of sound, see F.

Vorrichtungen,Phys. Chem.,

135,

Ann.

1843, 497-565.

physical and psychological, see H. v.

Helmholtz, Die Lehre von dm. Ton-empjindungen, 1863 (orlater eds.,

or Eng. trans.). Chap. 2-4. Foramore recent mechanical analyzer andsynthetizer than Lord Kelvin’s, see
D. C. Miller, The Science of Mtistcol
Sounds, 1916, 92-141 (for the 18
harmonics of a girl’s face, 119). On

by resonance, see

Gassendi, ExercUatlonee paradcxicae

electrical analysis

adverm Aristoteleos, 1, 1624, [n.v,],

S. S. Stevens and H. Davis, Hearing,

reprinted in Syntagma pbilomphicum,

1938, 19f., 39f,

Mersenne, Tmiten, op.
ott., Bk. 3 (the echo experiment ison p. 214).

la Tour, Sur la sirene, nouvelle ma-

On air as the medium of sound,les vibrations de Tair qul constituent

1658,[n.v.]isee 0. V. Guericke. Experimenta nooa
(atoocantuf)

Magdeburgicadevacuo spatto, 1672, Bk. II, Chap. 15;
R. Boyle, New Experiments ThystcoMechtmical, Touching the Spring o/Air, and Its Ejects, Made, for the
Most Tart, in a New Pneunutlcal
Engine, 1660 (or Latin ed., 1661;
or 2 ed., 1862), Experiment 27.
Guericke precedes Boyle, in spite of

On the siren, see C. Cagniard dechine d’acoustique desUnie k mesurer

Chlm. Phys., 2 ser., 12,
A. Seebeck, Bcobachtnngen uber einige Bedingungender Entstehrmg von Tonen, Ann.
Phys. Chem., 129, 1841, 417-436.
Rudolph Koenig and his work havebeen well described by D. C. Miller,

le son, Ann.

1819,

167-171;

Anecdotal History (op. cit.), 85-92,
et passim. See also Koenig’s town collected

researches

in

his

Quelques

the dates; in fact G. Schott publishedexperiences d'acoustique, 1882.

in 1657, an account of Guericke’s experiments with which Boyle is sup-the calibration of tuning forks, seeposed to have been familiar.

many textbooks of physics, e.g., W.

On resonance, harmonics and par

On the use of Llssajous figures in

Watson.

A Text-hook of Phy^cs, 7
Duncan andHals, see J. Wallis. Concerning a newed.,musical discovery, Phil. Trans., 12,
1877, 839-842, a trivial report which

S. G. Starling,

gains importance only byprior-

of frequencies by Lissajous figures in

Sauveur, Des intervales desthe cathode ray oscillograpb (with

ity;

J.

its

1920, 400-402; J.

A Text Book of Phys-

ics, 1936, 873-677.

On the calibration

tous lesno sweep circuit and^o frequencies

systemes et 1 tous les instrumens deimpressed at right angles upon themusique. Hist. Acadelectron stream), see

sons,

et sonapplicationrtSci, Parts, 1701,299-388, esp. 347-354, the first seri-

Stevens andDavis, Bearing, 21-24, 40 f.

PSYCHOPHYSICS OF TONE

348

On the bi&toiy of the developmentof thennionicvacuum tubes ( 1873-

1929), see E. L. Chaffee, Theory o/
Thermionic Vacnnm Tvhes^ 1933,

On the use and calibration of

S-ie.

the

tubes

as

see

audio-oscillators,

1863, Chap. 9;
the use of the Koenig fork,

Tonempfindungen,or, for3 ed., 1870, or Eng. trans.. Chap. 9.
For W. Wundt’s determination of
the lower limit by difference tones,
see his Giundxilge der physlohgi-

Stevens and Davis, op. eit., 35-41.

schen Psychologie, 1 ed., 1874, 362;

Limits of Hearing

idem, 3 ed., 1887, 1, 423; for his useof the Appunn lamella, idem, 4 ed.,for his use of the large Appunn fork,

A good account of the experimental
attempts from 1700 to 1900 to determine the upper and lower limitsof hearing is given by E. B. Titch-

Experimental Ptijchology, II,
1905, 13 f,, 24-36, 41-4B. The

ener,
ii,

older classical source

is

W. Preyer,

Udier die Grenzen der Tontuakrnehmmg, 1876; AkusHsche Untet-

1893,

450 f. For Iheyer’s deter-I,

minations, see op. cU., 1876, 1-25;
op.

1879, 1-10.

cit.,

F.

Galton’sofdescription

whistle in 1876

his

reprinted in his

isInquiries into Human Faculty, 1883,

375-378, where see also 38^.
For a rather recent acceptance of
50,000as thec.p.a.

upper limit bysuchmgen, 1879.
The early work of J. Sauveur on
the limits is described by an anonymous reporter, Sur la ditermination

a careful syslematist, see E. B. Titchener, A Text-book of Psychology,

d'un son Sxe, Hist, Acad. Set Paris,
1700, 134-143. Sauveur's paper on

Frobes, Lehtbuch der expeHmentel-

1910,

and

98;

Ibat 20,000

is

die later viewforabout right, seeT.

len Psychologie, 3 ed., 1923, 102.

the harmonics of strings was not pub-The first suggestions of a sensitiv-

The other papers

ity curve for hearing are to be foundlished until 1701.

before Savort are E. F. F. Chladniin thewho discoveredof A.

( die great acoustician

how to make sound pictures in dust

experiments determinationsand L. Boltzmann,

ToeplerUeber eine neue oplisdie Methode,
Schwingungen tbnender Luft-on vibrating plates). Die Ahistik(which Napoleon paid to have trans-diesiiulenzu

lated into fVench), 1802, 2, 27, 230,

Chem,

217,

[n.v.J:deJ. B.

Biot, Precis eUmentaire

physiqueexperimentale,

1817,[n.v.], but see 3 ed., 1824, 1, 344, 356.

F. Savart's

firstexperiment withthe 720-toothed wheel for the demonstration

of

the

dependenceofpitch on frequency and of die upper
Ihriit is

Sur la sensibiliti de Torgane

de I’ou'ie, Ann. Chim. Phys., 2 ser.,44, 1880, 387-352 (or see Ae German Ann. Phys. Chm. 96, 1830, 290-

analysiren,349-352;
Strutt),

Ann.

Phys.

1870, 321-352, esp.
Lord Rayleigh (J. W.

On

minimumthecurrent

audible in the telephone. Phi!. Mog.,
38,285-295, esp.

1894,

294

(or

109118, esp. 117). The first good audibility function was worked out by
M. Wien, Ueber die ErapflndlichScientific

kelt

des

Papers,TV,menschlichen

1894,

Oliresfiir

Tone verschiedener Hohe, Arch. ges.
Physiol, 97, 1903, 1-57, esp. 20-31.

304). His determination of the bwer

On audiograms and their implica-

with the two-spoked wheel is
Sur la limite de la perception destions about the limits of hearing, seesons graves, Ann. Chim, Phys., 2 ser.,tion of hearing and binaural aids forGermanthe deaf. Proo. not. Acad. Sci. Wash.,

limit

47,

1881, 89-74

(or

the

R. L. Wegel, Tlie physical examina-

Ann. Phys. Chem,, 88, 1831, SOB-8, 1922,

BOO).

which led

For H, Helmholtz on the lower
limit, see his Die Lehre mn denothers, mostly at first from tlie Bell155-160, the original paper
off

for

a

great

many

Telephone Laboratories; H. Fletcher,NOTES
Physical measurementsof auditionin the text are E. Luft,

Ueber dieand theli bearing on the theory of

Unterschiedsempflndiichkeit fiir Ton-

hearing, 1, ftanmn Inst,, 196, 1923,

hdhen,

289-326, esp. 291-293, a more gen-

540, esp. 528;eral

and clearer presentation of the
Wegel and the Bell Lahoratorlesj also Fletcher, Speech andUnierschiedsempfindliclikeit fiir Ton-

results ofhiilien,Heating,132-144,

1929,

On

the

general problem of the Intensltive
threshold andsee L,

tion,

audibility func-

tlie
J.

Sivian and

D.

S.

White,On minimum audible soundfields, /.

aamt. Soc, Amer., 4, 1933,

PhU.

Stud.,

4,

511-

1888,

M. Meyer, Ueber die

Z. FsijchoL, 18, 1898,

352-

372, esp. 352-^61; H, Stuoker, Ueber
die Unterschiedsempfindlichkeit

fiir

Tonhohen, Z. Slnnesphysiol, 42,
1908, 392-408; T. F, Vance, op. ctt.,1914, esp. 128 f. Tlie first pitch limens wim the tliermionic tubes were
got by Knudsen (op. d(. Infra, 1923)

288-321. For general discussion andassome of the more recent results, see
S. S. Stevens and H, Davis, Hearing, 1938, 41-68, 117-127, esp. 4148, S5-84, 67 f., 123-127. The way
in which tlie range of hearing in-thresholds for loudness. The standard

creases wifh tetensity is exactly com-parable to the way in whicli the sizeof the retinal color zones increases

with intensity; see pp. 173-176.

more

or

less

secondarytohisresearch on pitch limens witli thermionic conh'ol is E. G. Shower and

R. Biddulph, Differential pitch sensitivity of the ear, J. acoust. Soc. Amer,,

3, 1031,275-287.

On tile question as to how the discrepancies among the various deter-

minations of the differential limens

On the maximal sensitivity of thefor pitch are to be explained ns func-

Fine Methodetions of experimental artifacts, seo E,

zur Bestlmmung der HSrschwellen-

G. Boring, The size of the differential
limen for pitch, Amer. J. Psychol.,53, 1940, 450-455. On the way inwhich continuous change makes for

see A. Wilska,

ear,amplituden

desTtommeKells

beiFrequenzen, Shmd.
FhjM., 72, 1935, 101-165.

verschiedenenArch.

larger limens tlian abrupt change, see

L. W. Stern, Psychologic der Verand-

Differential Sensitivity

erungsauffassung,Ontlic history of differential sen-sitivity to frequency, see E. B. Tltch-

Experimental Psijchology,

ener.

II,

1898,

esp.

208-

243, On tlie way in which the transientsofabrupt change work the

opposite way, see Shower and Bid-ii,

1905, 232-245; T. F. Vance, Variation in pitch discrimination within

dulph, op. ait.

the tonal range, Pspchol. Monogr.,

gestion that the 3000 rods of Corti

No. 69, 1914, 115-149, esp. 115-

would be enough resonators to provide 33 discriminations per semitone, sec his Die Leltre tion den Tonempfindungen, 1883, Chap. 6 (n.v.,
but p. 219 in 2 ed,, 1865); or latereds. or Eng. trans.. Chap, 8, for 4500
rods and me discussion of the resonating basilar membrane. For 0.
Kulpe's computation that, on Luffs

120.

On the recent facts, see S. S.

Stevens

andII.

Davis,Hearing,

1938, 84-89, 94-98.

The conventional starting point for
the history of pitch discrimination is

Delezenne, Sur les valeursJ.
numdrique des notes de la gamme,
Recueil des travaux de la Socldti
des Sciences, de TAgrioulture et desArts de Lille, 1827, 1-56, esp. 4-6,
C. £.

The

date

usually

given,

1823,iswrong; idiis volume mr 1826-1827 is
not arranged chronologically. The
subsequent determinations mentioned

For H. v. Helmholtz’s original sug-

figures, there ought to be 11,004 dif-ferent tones

noises)(besides 553 different

and forhisi applicationofthe computation to the Helmholtz
theory of hearing, see his Giundriss

der Psychologic, 1893, 108-111, 114

PSYCHOPHYSICS OF TONE

8S0
(Eng.

110 f.).

104-107,dans.,

It

Schallempfindungen,ibid.,

470-474;

1885,

2,

must be remembered that this was

394-474,

the period when elementism to psychology was at its height; psycholo-

Die Messung von Schallstiirken, ibid.,sought to enumerate the conscious elements in some sort of a psygists

chological Mendeleyev

table,

Thus

esp.

P,

Starke.

3, 1886, 264-304, esp. 302-304; J.
Merkel, Die AbhSngigkeit zwischen

Reiz und Empfindung:

Schallreize,

1889, 499-557, esp,

ibid., S,

511-

total, added all the j.n.d. and discrete

515; F. Angell, Untersuohungen iiber
die Schdtzung von Schalltotensitaten

qualities of all the senses to get a total

nuoli der Memode der mittleren Ab-

of “more than 44,485" conscious ele-

stufungen, ibid,, 7. 1891, 414-468,
esp. 425-481; B, Kiimpfe, Edtrage

E. B. Titchener to 1896, seeking thements. See p.

10. It is interesting tonote the confusion of thought at thattime, for some psychologists recog-

nized the fact that sensory series arecontinuous and yet treated the j.n.d.

ezperimentellen

zurPriifung(fir

Methode der riohtigen und fuohen
Fallen, ibid., 8, 1893, 511-591, esp.

584-588.

as if they were discrete and quantal.

The more recent studies on tone

For general dlscussian of differen-

are M. Wien, Ueber die Messung dersensitivity,

Tonsthrke, Ann. Phys. Chem., 272,

see W. Wundt, Grundiiige der phys-

1889, 834-857, esp. 845-848; V. 0.

tialintensitiveiologlschen

acoustic

fsycholosie,

6

ed.,

I,

Knudsen, Tlte sensibility of the ear

1908, 648-656; and mr recent facts,

to small differences in intensity

S. S. Stevens and H. Davis, Hearing,frequency. Phys. Rev., 21, 1923, 84-

136-140. About the form of

1938,

the

Weber function in general, see

and

103,

91-94; R. R. Riesz, Dif-

ferential

sensitivityofthe ear forA. H. Holway and C. C. Pratt, The

pure tones, ibid., 31, 1928, 867-875,

Weber-ratio for intensitive discrim-

but Riesz does not give his actual
values which are printed to Stevens
and Davis, op. cil., 140.

ination, FmchoL Ben., 43, 1938, 322-

340.

On

volkmann's sound pendu-

lum, see G. T. Fechner,
der Peychophysik, 1860,

ElmenteOn the total number of discrimina-

176-178;

ble pitches and intensities, see Stevens and Davis, op. cit., 152 f., butor for the double sound pendulum,

Kilmpfe, op. cit. infra.

On a Fallap-

parat for noise intensities see Tlscher,op. cit. infra; on Wundt’s form of the

FaUapparat, see Starke, op. cit. infra.

The

early

investigations

under

cf. also

Boring, he. cit.

For the determination of fixed
quanta for both pitch and loudness,see S. S. Stevens, C. T. Morgan, andVolkmann, Tlieoty of the neuralJ.

Vierordfs direction were T. Renz andquantum

A, Wolf, Versuche iiber die Unter-loudness and pitch, Amer.

scheidung difierenter SchallstSrken,

chol. 54. 1941, 315-335.

to

the

discrtoitoation
J.

of

Psy-

Arch, physiol. HeOk., 15, 1856, 185193, em. 190-192; C. N5rr, Experimentdle Prilfung der Fechner’schen

Cesebses auf dem Cebiete dec Schallstarke. Z. Biol., 15. 1879,
esjP

297-318,806-314.

Tonal ScalesThemention here of
tonal scales for the reason that theimporlant developments are all retext omits

eentered to or upon Wundt’s labora-

The problem goes ba^ toFechner, who assumed that all j.n.d.

tory were E. Tischer, Ueber die Un-

are equal and, on the basis of Web-

terscheiduttg vnt Schallstiirken, Phil.

er'sStud., 1, 1883, 485-542; G. Lorenz,ties

Die Methode der riohtigen und fal-theinvestigationsof noise thatsohen Flille to ihter Anwendung auf

cent,law, built up a scale of intensi-(Fechner’slaw)

by counting

from the absolute threshold up to the intensily being measJ.n.d.

NOTES
He could not do mncli about

ured,

351

that a frequency that is the geomet-

pitch because there were in 1860 no

ric

good data. Weber and ho did con-quencies

sider that pitoli follows Weber’s law,

two equal pitch differences. Wundt
thought not; Stumpf thought theydid. About this point raged one ofbecausethe

proportionalmusicalthetologarithms

theintervalsaredifferencesofthe frequenciesofthat determine them; but much laterit

was realized that pitch is not in-tensityand, whatever the form ofitsfunctional relation to the stimu-

lus,

could not, therefore, be an in-

stance of Weber's law.

On this see

E, B. Tilcliener, Experimental Psy-

chohey,test ofj.n.d.

II,

ii,

IBOS,

232-235.

A

Fechner's assumption that all

are equal would lie in the dis-mean between two otfe

the

would

bitterest

alwaysfre-establish

controversies

this

of

period. See Titdiener, op. cit., 241-

245; C. C. Pratt,

The bisection of

tonal intervals smaller dian an octave, 7. exp. Psychol, 6, 1923,

211-

222; E. G. Boring, 'The psychologyofPsychol.

controversy,

Rev.,

1929, 97-121, esp, 107-113.

however,whole,

has

there

36,

On thebeenmuch less use of sense distances forpsychophysicalmeasurementthancovery of whether sense-distances,

the attempt to quantify psyohobgy

judged equal, yield a sensory scale

ought

to

centlyStevenslilce

summed ].n.d.

that of theIfthey do, the bisection of a sensedistanceshouldgeometricalstimuli.

be given by the

mean

of

the

extremeMoat of the papers batedabove in Wundt’s Phil. Stud, attack
this

have

accompbshed.

and

his

Re-

associates

have been creating scales of pitchand of loudness, scales based on theequation of sense-distances and notofj.n.d.

They have even created aunit of sense-distance for pitch, theproblem, though with different

mel, and another for badness, theTheresone. See Stevens end Davis, op. cit.,

results.

See Wundt,

Zoo.

oit,

was also the question as to whether

76-84, 112-123;

S.

S.

Stevens andent parts of the scale represents al-

Volkmann, The relation of pitch
to frequency; a revised scale, Amer.

ways die same pitch

7.

the

same musical interval in differdifference, soJ.

Psychol, 53, 1840, 329-353.

Chapter 10

AUDITORY PERCEPTIONN THIS chapter we consider the history of the older problems
of auditory perception; beats and combination tones, timbre

I andfusion, the nature of vowels, the attributes of tones andthe localization of sound.

Beats and Combination Tones
Because the frequency of the first difference tone for any two
generating tones is the same as the frequency of the beats for thesegenerators, the histories of the knowledge of beats and of com-bination tones are related, even though psychologists since Helmholtz have had adequate evidence that the two phenomena are distinct,

We have aheady seen that it was Sauveur who, in 1701, first described the complex vibrations of a string and the relation of theharmonics to the fundamental (see pp. 825 f.), It was in connection with these experiments that Sauveur discovered beats. Trying
to establish standards of frequency for music, he found beats for theorgan pipes that were slightly out of tuno. His earlier paperm 1700,Sur la ditemiMtion (fun son fxe, irot only described beats andshowed that their frequency equals the difference in frequency between the two primaries, but actually used the beats for tuning

and for tire measurement of mistuning. He explained the beats correctly as the alternation of reenforoement and cancellation, and,knowing nothing at that early date about Ohm's acoustic law, hefound the explanation both adequate and obvious.

The difference tone was discovered, quite independently of the
discovery of beats, by the Italian musician, Tartini, as he taught
himself the violin in the monastery of Assisi. With double-stopping,he observed, there could be heard a tern suono, a third tone additional to the proper tones of die two bowed strings,

and thisthird tone he came to use in checking the tuning of the strings.

352

COMBINATION TONES

353

Tartini himself later dated his discovery in 1714, and in 1728 hefounded a school for the violin in Padua, where he taught thismethod of tuning. It was not until 1754, however, that he described
the phenomenon in print, Then he published a treatise on music,

introducing the terzi suoni in the first chapter as basic to his theoryof harmony. It was thus drat these extra tones

came later to becalled Tartini’s tones, a term which is still occasionally met.

Because Tartini did not publish anything about the third tones
until twenty-six years after he had begun to teach students to notice them, it is natural that other published references to the phe-nomenon should precede Tartini’s. Sorge, for instance, mentioned
the existence of these tones in 1744 and the next year named themgrave harmonics. He has, therefore, often been called their discoverer, but, not claiming discovery, he was probably only noting

a fact that some musicians had learned from Tartini or from Tartini’s students. It is, moreover, plain that a French savant, Romieu,

discovered difference tones in the early 1740’s without any knowl-edge of Tartini’s teaching, although he may have learned something from others

when he published in 1751, likelater, since,

Sorge he used the phrase grave harmonics. Thus the order of orig-—^reverses the order of the publica-

inality—Tartini-Romieu-Sorge
tions of those three men,

— an obscure volume which has

Romieu, in his paper of 1751

^in—actually sought

only recently been given its place in tliis history
to relate the grave harmonic to beats.

He noted the obvious fact

diat the pitch of the harmonic corresponds to the frequency of thebeats. This view, that the grave harmonic is a “beat tone,” is usually

attributed to Lagrange, who

expounded it in 1759, noting thatbeats which are too fast to be heard ought to give rise to a third
tone. To Thomas Young, who supported the same theory in 1800,
it isprobably due that the problem received in the early nine-

teenth century the attention it deserved.
It was Vietli who coined the term combination tone in 1805
when he discussed the results of Young and another investigator.
The older term was grave harmonic, but Helmholtz ruled in favorof Vieth’s phrase because it could be made to include summation

tones as well as difference tones.

In 1832 Hallstrdm extended the beat-tone theory to its logicalconclusion. If two primary tones sounding together beat, and thebeats are so fast that they create a beat-tone, may not this beat-AUDITORY PERCEPTION

354

tone, itself beating with one or the other of the primaries, establish a second beat-tone? And, if there can thus be a second com-bination tone, why can it not beat with the first combination tone
or a primary tone giving rise to a third combination tone? And isthere any

Wt tothis progression of beats

and resultant com-bination tones? Actually HaUstrom specified only four terms inthis series, although he wrote und so wetter after it. If s represents

the frequency of the higher primary tone, and r the frequency ofthe lower primary, then the first four combinations, HaUstrom

pointed out, are the first four differences, as follows:
Basic tones

Combination tones

S

f

j-f

I

T

s-r

Sl«

II

s

2r-s

2(«-r)

III

s-r

3f-2s

IV

m

2

Hero the second combination tone is dependent upon the first; thethird and fourth are dependent upon die second. Differences whichcoincide with tones already generated HaUstrom omitted. His ex-

periments consisted of the study of various tonal dyads, in which

he was able to identify the existence of one or two—never morethan two— of these four combination tones.
Hslllstrdm published in 1832. Ohm’s acoustic law was promul-

gated in 1843. In 1856 Helmholtz published his investigations ofcombination tones, a paper of primary importance for the following reasons, (a) It reported the discovery of summation tones—
tones of which the pitch corresponds to a frequency which is thesum of the frequencies of the two primary tones. This discovery
led Helmholtz to invent the term difference tone for the Tartini
tones and to include both summation tones and difference tones

under the mbric combination tones. The sununation tones, being

weaker than the more obvious difference tones, are harder to observe, but Helmholtz's discovery is fully established by modern

research, (b ) Helmholtz also verified the difference tones of higher

orders—die tones that HaUstrom had described and still others
based upon them. He noted how these tones would vary for themusical intervals none for the octave, one for the fifth, two for the:

fourth, three for the major third and the major sixth, four for theminor third, sjx for the minor sixth, (c) Under certain conditions

he succeeded in getting objective combination tones which, byresonators, could be pidked out of a complex physical wave prior

BEATS AND COMBINATION TONES

355

to the intervention of the human ear. The necessary conditions forthem seemed to him to be met when a large body of air is set invibration, as in the wind-chest of a harmonium, (d) Finally, hestated correctly the physical conditions which would have to be
fulfilled if combination tones are to be heard: the displacement of

the vibrating body must fail to be proportional to the force actuating the displacement. Such a statement is equivalent to the mod-ern formula for combination tones: they are added to the acoustic

complex of the two primaries only when the transmitting mechanism distorts the wave-form. Herein lies the explanation as to why
difference tones occur in what is really a contradiction of Ohm’slaw.

According to a strict and simple interpretation of Ohm’s law,neither beats nor difference tones should be heard. If the external

stimulus consists only of two superimposed harmonic frequencies,

then we should hear only two pure tones. The fact that the amplitude of the successive waves in a combined frequency seems tovary periodically has nothing to do with the matter, although thevisual appearance of the graphed waves makes it look as if beats

should be heard. Beats actually occur because two frequencies act—

upon the same resonator in the ear, or sometimes outside thebody in a physical resonator, for tuning is never so sharp that aresonator responds only to a single frequency and not to otherfrequencies adjacent to the most natural period of the resonator.

Combination tones actually occur, not because there are beats
which, having a rate above the lower limit of hearing, produce atone, but because at some place—thereknew, external to itis—in the ear andalso, as Helmholtz

distortion of the wave-form, a dis-tortion that yields difference-frequencies and summation-frequencies in Fourier’s analysis, in resonance, and thus also under Ohm’s

law when the distorted wave is regarded as the stimulus instead of
the original wave. It was quite dear to Helmholtz that subjective
beats depend upon the properties of the auditory mechanism, thatcombination tones depend on distortion, that the two are different

phenomena, and that the first difference tone is not a “beat-tone.’
Others after him had less insight.

Helmholtz explained beats, as many do today, by his resonanceplace theory: the adjacent frequencies actuate adjaeent regions of
the organ of Corti, and the overlapping parts activate the afferent
nerve-fibers with pulsating intensities. Such a special situation is

356

AUDITORY PERCEPTION

found outside the body only when the frequencies act on the same
resonator, as in the amplitude modulation of ordinary radio broadcasting. Helmholtz was at considerable pains to demolish the beat-theory of the first difference tone by showing that beats up to 132

per second can be perceived dearly as roughness. If the lower
limit of hearing lies at 30 c.p.s., then there must be a region be-

tween 30 and 132 whore both beats and a difference tone corresponding to the beat-frequency can be heard simultaneously. Thisphenomenon Helmholtz established as an observed fact.
After Helmholtz there was until recently no great further insight into the nature or significance of either of these phenomena.

Both Rudolph Koenig (1876) and Prey er (1879) argued that combination tones are subjective, but tliose were the days when the

dualism of mind and matter pervaded the thought of all the wisemen. To argue diat a phenomenon was subjective was to imply
that it was therefore not objective, even though one might seek foran explanation of the phenomenon in a physiological mechanism
within the organism, a mechanism which would be wholly physicalif transferred outside the subject’s skin.

Koenig also defended thebeat-tone theory of the difference tone, the theory of Romieu, La-

grange and Young, Nevertheless, Helmholtz was right and boththese others wrong, as the modem user of thermionic apparatus

well knows. The beat-frequency oscillator gives electrical “beattones’ only because it introduces distortion into the wave that iscompounded of the two primary frequencies.

How extremely complicated distortion may make the soundwave has been shown by modem methods. Newman, Stevens andDavis (1937) used an electrical wave-analyzer to discover thecomponents of the electrical potential occurring at the inner ear ola oat when two primary tones of 700 and 1200 o.p.s. were soundedat its outer ear. Discarding all combination tones in which the intensity was less than one per cent of the fundamental and all witha frequency above 8000 c.p.s., they nevertheless found 64 of the 68
possible additional frequencies. This number is so large because
distortion adds to the primaries upper harmonics as well as com-bination tones, and tlius makes possible combination tones be-

tween these harmonics.
In modem radio broadcasting we have both amplitude modulation and frequency modulation. In the first, the amplitude of acarrier wave of high frequency—too high a frequency to be heard

TIMBRE357—

is varied in accordance with the wave-form of the soundwhich is to be broadcast. In the latter, the frequency itself of theitselfcarrier wave is tlius varied. It can be shown mathematically andphysically that both forms of modulation produce similar results,
electrical oscillations at the frequencies of the impressed modula-tion which, under Fourier’s anafysis or, in sound, under Ohm’s law,

break up into the desired components. The physics of these relationships is too involved for exposition here, although its mentionisin point because it shows how far from the truth were Romieu,—

Hallstrom, Koenig and Preyer^but not Helmholtz. Beats and com-bination tones are physical phenomena, special cases of modulation. They are subjective only ns the organism provides the physicalconditions which produce them for a resonating organ in which

the localization of resonance is not too sharply restricted.

The precise physiology of beats and combination tones will bedearer to the reader after the next chapter has been read. Helmholtz thought that the distortion necessary for combination tones

occurred in the middle ear; recent research, however, indicatesthat some of it depends on the transmission mechanism of the middle ear

and some on the properties of the inner oar. The only

physiological theory of beats that has ever been offered is Helmholtz’s in terms of his placo-resonance theory {vide supra).

TimbreSince any auditory stimulus can theoretically be reduced to acomplex of simple harmonic vibrations, and since Ohm’s law is ordinarily approximated, most of the phenomena of hearing can beunderstood as resultants of the interaction of separate tonal components. Beats and combination tones are consequences of suchinteraction, as are also the phenomena of timbre, fusion, noise andmasking. With these latter four we occupy ourselves in the following sections.

The timbre of a note, its Klangfarbe or musical quality, depends
wholly or in part, according to the way in which the word is defined, upon the pattern of harmonics that are present with thefundamental. The historical background of this problem lies in
Galileo’s discovery of resonance, in Mei'senne’s apalysis of thefundamental nature of the vibrating string, in John Wallis’s discovery of the harmonic character of overtones, and in Sauveuris

AUDITORY PERCEPTION

358

eslablishment of the relation of harmonics to the fundamental ( pp,324-327). The fact of timbre, of qualitative differences other thanpitch, was recognized early; in fact the French word timbre and,to a lesser degi'ee, the German Hang, are acoustic words which

express exactly this difference. The mutual significance of aU thesefacts could, however, hardly have been realized before the estab-lishment of Ohm’s law in 1843. It was subsequently Helmholtz

who saw that, since all sounds can be reduced to a complex of
haimonic components, there are only three dimensions to the auditory stimulus; the frequency, the amplitude, and the combinationof different frequencies. So be looked to the pattern of partials in

a musical note to explain its Kkn^orbe. Actually his first paper on
this subject(

1859) was an attempt to account for the Klangfarbeof the different vowel sounds in terms of the relative strength ofparticular paitials in each of the principal vowels. Later in the

Tonempjindungen this theory led to his identification of Kkngfarbewith the pattern of partials. His logic was simple. If musical instruments, human voices and vowels can differ in timbre from one another at any pitch and at any loudness, then there is nothing left

but the pattern of the different pitches to distinguish them. This
theory has stood the test of time.

The theory was not, however, quite so easily accepted as thisbrief statement seems to indicate. In order to test it Koenig built

the clang synthetizer (Fig. 51, p. 331). There was, moreover, another dimension of the stoulus that might have entered in: thephase relation of the component tones. Helmholtz was at great
pains to show that this variant did not alter the sound of clangs orof musical combinations of tones.

Helmholtz's emphasis upon the prominence of harmonics in allmusical notes led the psychologists of the late nineteenth century
to stress the pure tone. Inasmuch as fire weakly struck tuning-forkor the weakly blown bottle gives a fundamental almost without

harmonics, it was supposed Aat absolute purity could be had byhearing such a tone through a resonator tuned to the specific fre-quency. It is now known, however, that even a ‘pure’ stimulus delivered to the outer ear is distorted by transmission throu^ theauditory mechanism and flat this distortion, under Ohm’s law, isequivalent to;, the addition of harmonics, Since with any strong
activation this distortion is bound to occur, it is safe to say that noloud pure tone has ever been beard.

IAURAL HARMONICS
It is difficult to decide who

359

discovered these aural harmonics.

Helmholtz, who, as we have seen, was aware that the difference
tone depends upon distortion, in the third edition of the Tonemp-

fndungen (1870) added to the section on combination tones anappeni'x which shows that certain harmonics would be generated

by distortion and which gives die mathematical equation that describes their occurrence; nevertheless he left the matter as if thesepartials were to be regarded as combination tones. Lord Rayleigh(1896) supported Helmholtz's argument, but also failed to makeit

clear that the aural harmonics are not necessarily difference

tones or summation tones. In 1924 Wegel and Lane, also interested
in the consequences of excitation by two simultaneous frequencies,

were able, with two generating stimuli of 700 and 1200 o.p.s. to findin the ear altogether 19 resultant frequencies, which included thesecond and third harmonics of both generators. They used a third
exploring stimulus, varied its frequency and noted when the subject could detect beats, Wegel and Lane did this research in the

Bell Telephone Laboratories, from which in 1929 Fletcher published his Speech and Hearing, devoted in great part to the sum-mary of the recent acoustical research of those Laboratories. In
this book for the first time there wasa clear account of the sub-jective harmonics which, because of the non-linear transmission of

the ear, occur for a single pure generating tone without difference
tones or summation tones, It was Stevens and Newman who substituted the term aural harmonics, since the word subjective seems

inappropriate for a phenomenon whose physical cause is so wellunderstood.

Tonal Fusion
Closely related to the problem of timbre is the classical prob-

lem of tonal fusion. Are some tonal complexes more unitary thanothers? Ordinarily the partials of a note are so intimately fusedthat they cannot be heard separately except

by special means.

That is why, until Helmholtz insisted upon it, their great importance was not recognized. Sauveur had shown how the partials

can be isolated physically in a plucked string by damping thestring at a node with the light contact of a brush; if one touches

the string at one-third its length only the third partial, the sixth,

and those for other multiples of 3 are left. Then the observer, knowing what to listen for, can hear the partial in the tonal complex

360

AUDITORY PERCEPTION

without the damping. In fact, Ohm’s law would not be valid if theear could not make this analysis.

Helmholtz did not write about fusion, but about consonance hehad a great deal to say. The consonant intervals, according to accepted musical principles, have simple ratios; the simpler the ratio,
the greater will be the number of coinciding partials for the twocomponents. In the octave, the most consonant interval, with its
frequencies in the ratio of 2:1, all the partials of the upper notecoincide with partials of the lower, so that the two complexes intoipenetrate each other maximally. In the fifth (ratio 2:3) onehalf of the partials of the upper note coincide with one-third of

the partials of the lower, whereas in the tritone, (f-b, ratio 82:45)
onlyof the partials of the upper note coincide withof thepartials of the lower. The simpler the ratio, the greater the degreeof interpenetration. Thus it may be said that Helmholtz both dis-covered and advertised the intimate fusion of harmonics in a clang

and in the musical consonances.

On the other hand, tire formal doctrine of tonal fusion is pe'’cuUarly StumpFs, who formulated it in 1890 in the second volumeof his Tonpsychologie. Stumpf held that tones tend to fuse, to interpenetrate each other, with the result that the total perception

becomes something different from the mere concurrence of its
components (as the Gestalt psychologists also said later), and thatdifferent combinations vary in dieir degrees of fusion. Fusion,

Stumpf thought, is not unanalyzability, because the expert observer can analyze the best fusion, noting its degree; nevertheless,it istrue that unmusical persons have difiSculty in analyzing thegood fusions. Stumpf was willing to distinguish five gross degrees
of fusion as follows. ( 1 ) The octave gives the best fusion. His un-musical observers might mistake it for a single tone three-fourthsof the time. (2) The fifth is the next best fusion, being mistaken
for one tone about half the time. (3)The fourth is still poorer.

(4) Then come the major and minor thirds and sixths. (5) At thebottom of this series lie all the other intervals, including the seconds and sevenths, which nevertheless show some degree of fusion,

being mistaken for a single tone perhaps 10 or 15 per cent of thetime by unmusical persons. Now this list follows Helmholtz’s or-der of deaeasing consonance in that the number of partials com-

mon to the two components diminishes in the successive groups,
but Stumpf held that the harmonics do not determine the fusion.

TONAL FUSION

361

Stumpfs chief laws of fusion were these, (a) Degree of fusion
is a function of flie vibration ratio of the components.
isHence fusion

independent of the region of the musical scale in which thetonal interval occurs, This law Stumpf modified with the observation that the degree of fusion is not greatly altered by slight rais-tuning, a modification which allows the same degrees of fusion to

the just and the tempered intervals and also contradicts the state-ment that the simplest ratios have the greatest fusion. For instance,
the just third has the ratio 4:5, but the equally tempered third has
the ratio 1;-^ or about 1:1.259921. (h) Degree of fusion is thesame for intervals beyond an octave as for intervals within an
octave; that is to say, the degree is the same for the third and thetenth, the fifth and the twelJEth. This rule limits the first rule tointervals within the octave, (c) Degree of fusion is not affected bytimbre, Stumpfs belief that the phenomena of fusion can be dem-

onstrated wifli pure tones is a direct contradiction of the belief
that fusion depends on coincident harmonics, but Stumpf did not,of course, know about aural harmonics. Finally Stumpf said (d)that fusion is independent of the absolute intensity of ie constitu-

ent tones and their relative intensities; (e) that it is not affected byrelative location of the sources of tone; {f ) that it occurs when one

tone is brought to one ear and another to the other ear; and (g)that imagined tones have the same degree of fusion as perceived
tones. Although in imagining two simultaneous tones, one is con-strained, Stumpf said, to hear the proper degree of fusion, one may

not hear at aU the beats which would inevitably occur in the perception.

Stumpf was an expert musician and a phenomenologist truly inthe tradition of Goethe (cf. pp. 112-115). The details of his laws

depended upon his own confident observation and but little on the
confusion of single tones with dyads by unmusical persons. For
several decades his theory of tonal fusion stood out as the best

example, in an introspective psychology that was largely analytical,of the synthetic process among conscious elements.

Now his theory

has lapsed, not so much from confutation as from disuse, becauseof its failure to relate itself significantly to other phenomena of
tonal perception. The different intervals, of course, are separately

recognizable to musicians; Pratt showed in 1921 hew they differ

from each other in their attentional analyaability, in the disparityof their two pitches, in the degree of roughness occasioned by the

362

AUDITOBY PERCEPTION

beats among their harmonics (which we now know may be theaural harmonics of tones that are pure outside the ear), and in thepleasantness associated with these patterns by musical observers.

Edmonds and Smith (1923) tried to find adjectives to characterize these perceptions; the octave was “smooth,” the fifth “hol-low,” the fourth “coarse,” the thirds “meUow,” the sixths “luscious,”

the sevenths “astringent,” and the seconds "gritty.” Brues (1927)

showed that the degree of fusion, as determined by the comparison
judgments of laboratory observers (not by the confusion of two
tones with one by unmusical persons) varies continuously through-out the octave, with maxima at unison, the octave and somewhere

near the middle of the octave, with two minima in between (often

near the second and seventh), and with quarter-tone intervals giving about the same degree of fusion as the adjacent musical intervals. Stumpf—who never plotted acurve of degrees of fusiotir—would have had fairly narrow peaks with different heights, allascending from a base level for the seconds, sevenths and nonmusical intervals. In 1934 Pratt dismissed tonal fusion from psy-chology on the ground that StumpTs theory was never clear, that
his degrees of fusion could not be verified, and that in general allmusical dyads are about equally unitary if the roughness of beats

be ruled out of consideration and if the uniqueness of the octave
be granted.

What has happened is that Stumpfs theory of fusion has disappeared along wi& the cult of expert introspective observation. The
expert observer is now the expeiunenler, not the subject, who may

indeed be a rat. Stumpfs musical training had become his prejudice; he knew too much about tones to observe their natural properties in their purity. What

we have remaining is the fact that at-

tentional analysis of tonal complexes, under Ohm’s law, varies indifficulty. The components mask each odier{vide infra). Stimuli

whose effects are but little differentiated in lie organ of hearing
ate not easily discriminated (a principle of which the place-reso-

nance theory of hearing makes use). Stimuli constantly associatedin experience may not be easily separable, and the aural harmonics—^which were notestablish associations—especially for the octave

supposed to exist when it was thought that tones could be ‘pure,’Thus the demise of this once important theory goes to show how far
psychology has advanced from the phemonenological observationof the expert observer toward the objective experimentation inNOISE363

which hotii the human and animal subjects are relieved from theresponsibility of being scientifically sophisticated.

Noise
The psychology of sound has had mostly to do with tones, although nearly all sounds in nature are noises. It was, of course.

Ohm’s law that created this situation, for thereby it became possible to deal with a continuative sound as a sum of tones, provided

exceptions, like beats, were given special consideration. Even the

combination tones, whiph seemed to be exceptions, fell underOhm’s law when it was realized fliat they are Fourier components
of a distorted wave-form. Are noises also complex fusions of tones?

There were two problems. The first concerned the continuity ofnoise and tone. Noises may be tonal; a thud—bang—-pop ascends
in pitch, as does also a series of continuative noises, like a rumble—rattle—hiss. Some of these Helmhote mentioned, together withthe fact that noises can be built up from tones by striking a large

number of piano keys at once. Does this continuity from the indefinite pitch of noise to the definite pitch of tone mean that thetone and the noise belong in the same class? Here was one problem. The other concerned the organs of perception. Are there different sense-organs for tone and noise?

Helmholtz, who in 1863 described the tonality of noises, was inclined to the view that there might be different organs for tone

and noise, that the ampullae of the semi-circular canals or perhaps
the vestibular organs might mediate the perception of noise, Holding that periodic wave-forms give rise to tones and aperiodic wave-

forms to noise, he implied a continuity between noise and tone, forthere can obviously be intermediates between these two extremes.

In 1875 Exner, using Savart’s spoke (see p, 334), found that thesuccessive noises of a card or a piece of wood, striking the rotat-

ing spoke, could be distinguished when the interval between hits

was greater than .002 sec. In other words, tonality begins to comein, as Savart’s spoke speeds up, before noise completely disappears.

So impressed was Helmholtz by ftiis evidence of continuity that hechanged his mind in 1877 about the organ of noise, concluding thatnoise like tone is mediated by the cochlea. He stressed then the factthat the aperiodic vibrations of noise are more or less indeterminate
in pitch, whereas the periodic vibrations, no matter how complex.

384

AUDITORY PERCEPTION

are determinate. Stumpf in 1890, relying as usual on his expert introspection, argued that noiseis

not pitch, even though one ofthem may enter into a perception as the other passes out, and that
their perceptual disparity indicates the existence of separate or-gans for them. Kiilpe (1893) supported the essentials of Helmholtz’s final conclusion.

In 1913 E. R. Jaensch undertook a study of vowel sounds inwhich he presented the view that the vowels are noisy tones, being
partially aperiodic. What he did was to construct a photoelectricsiren.

He cut a sine-curve into the edge of a circular disk, rotatedthe disk so that the undulating edge, placed in a beam of light,

caused the light to vary sinusoidally, let the beam shine on a photoelectric cell ( selenium ) , and then put the resulting current througha telephone receiver. The result was a tone. A disk with an aperiodic wave-form cut on the edge gave a noise. A disk similar to thesine-curve but with varying wave-length gave, so he maintained, avowel; at any rate it gave a noisy tone with a pitch as indeterminate
as the wave-length. The problem of vowels we consider later, but
it is important here to see that Jaensch's experiment led him into

what he called a Du‘(McitaUtheorie of hearing: periodic vibration
exdtes the cochlea and gives tone, whereas aperiodic vibration excites some other organ, perhap in the vestibule of the ear,andgives rise to noise. The intermediate sounds excite both organs invarying degrees. The analogy is to the duplicity theory of von Kries
for the functioning of the rods

and cones in vision. Von Kries

thought of the rods as forming a more primitive sense than thecones. Jaensch thought of noise as more primitive than tone.

In recent years the duplicity theory of tone and noise has disap-

peared because there was no physiological evidence for it, because
psychologists have come to rely less upon expert introspection, andbecause the tonal stimuli are now known to be so complex that
there seems to be no need of a separate class for noises. For one
thing it became evident that masses of tones, though noisy, cannevertheless be treated as tones. Raley, for instance, in 1913 re-ported that a group of eight to ten tones, lying close together in fre-quency and occuning simultaneously, have the pitch of the meanfrequency; but Ekdahl and the present author showed in 1934 thatthese complexes are noisy tonal masses of an approximate pitch

which an observer may localize perforce at the midpoint of themass when he is required to equate the mass to the pitdi of a single

MASONG365

frequency. In 1929 Bek^sy showed that the difierontial limen for
pitch is greatly increased when the duration of a tone (800 c.p.s)
is deci'eased

from 0.2 to 0.01 sec., thus furnishing another illustra-tion as to how tones can vary in definiteness of pitch without ceas-

ing to be tones.

Perhaps the most striking evidence of the relation of noise to tonelies inthe perception of die thermal noise. A thermal noise is anoise produced by the random movements of the molecules of the
air as the result of thermal agitation, and it is duplicated when theelectrical potential, due to the random agitation of the electrons in

a conductor, is amplified and impressed upon a telephone receiver.

This noise is not due to aperiodic motion but has in it all frequencies in equal degree. Its sound is a shshhsh of fairly definite pitch.

The shshshsh is localized, it is trae, in the middle range of hearing
with the extremes of pitch lacking because, since aD frequencies
are equally intense, the pitches for the most sensitive part of therange of frequencies predominate; but within the sound no discrimination is possible. It is certainly a noise, and its properties

strengthen the conclusion that a noise is a complex fusion of tones,
often brief or rapidly varying, with the indefiniteness of its pitch

depending upon the range, equivocality and brevity of the deter-minant frequencies. Fletcher in 1938 made use of the principle thata thermal noise is all frequencies in equal intensities to study thethresholds of particular frequencies. He determined the masking
effect of a thermal noise upon each frequency.

Masking
Another exception to Ohm’s law is found in the phenomenon ofmasking. Even though it was well known that loud sounds 'drownout' faint sounds and that only the more intense harmonics in aclang are audible, the matter was slow in coming to quantitative
investigation.

The first experiment was published in 1876 by A. M. Mayer, whoused organ pipes for low tones and tuning forks for high tones. He

sounded a pipe and a fork together in such a way that both tones
were audible, making the sound of the fork especially noticeableby moving his hand back and forth over the mouth of its resonancebox, so that the fork-tone fluctuated. As the vibration of the fork

died down, its tone presently ceased to’be audible, masked by the

306

AUDITORY PERCEPTION

tone from the organ pipe. When Mayer thereupon stopped the air
to the pipe so as to remove the masking sound, immediately thefork-tone again became audible and surprisingly loud.

We haveseen (p. 330 ) that there was in the last century no good way of controlling the intensity of tones, Thus Mayer’s experiment was notquantitative, nor did it lead to an exact determination of these relations until nearly fifty years later. Mayer concluded merely that

low tones may obliterate high, but that this effect is not reversed.
In the latter conclusion he was in error; yet he could not, with his
technique, have been expected to discover the less striking mask-

ing effect of high tones upon low.

The classical paper on masking was published by Wegel andLane in 1924. It was one of the pioneer papers in the new thermionic technique for the control of tones, a paper which we havealready considered in connection with the discovery of amal har-monics. They found (a) that a given frequency tends to maskother frequencies in the same region, that the masking effect tends
to be greater the closer the masked frequency is to the masking fre-quency, but that this general rule requires two modifications, as
follows, (b) When the masked frequency is so close to the mask-

ing frequency that beats are heard, there is a slight reversal of therelationship, for audible beats will occur for a tone which, if moved

out of the frequency region for beats, would have been just inaudible. (c) The inevitable presence of aural harmonics in the in-tense masking tone extends the masking effect far up into thehigher frequencies, giving the total masking effect for a set of harmonics. This is the reason why Mayer observed masking from be-

low up, while missing the effect from above down, Fig. 56, a modification of Wegel

and Lane's schematic diagram, shows what isheard for all frequencies and intensities of the secondary (masked)
tone when the primary (masking) tone is 1200 c.p.s. and 80 db.

The nearer the secondary to the primary, the louder it must be to
be heard. In the region of beats, however, the masking effect drops
off a little. This general functional relation repeats itself at the re-gion of each harmonic—at 1200, 2400, 8000

c.p.s. The perceptual

picture is, moreover, compHoated further by the entry of differ-ence tones into the mixture.

Because these phenomena of masking imply an overlap in thephysiological effects of adjacent frequencies, they have been em-

ployed, in connection with a place theory of pitch, for the relative

400

000

000

1000

1200

lOOO

2000 2400

3200

4000

FOEOUGNOY OF SECONDARY TONE
Fre. S6.

Tonal Mashng: Wbbsl and Lane (1924)

The maskiog effect at a piinary tone (1200 c.p.s. and 80 db above
threshold) upon secondary tones whose intensity is given by the ordinate
scale end frequency by the abscissa scale. The solid line is the locus ofdiresholds for the secondary tones in tlie presence of the primary. The
thresholdislowered in the region of beats forall

the harmonics of the

primary. After Wegel and Lane, as modified by Fletcher.

was able in this way to assign loci in the organ of hearing to all thefrequencies from 100 to 20,000 c.p&

VowelsThe nature of the sounds employed in speech forms in itself aninteresting scientific problem,

and there have been various at-

tempts to build talking machines or automata, at least one of which
included in its mechanism a dwarf concealed in a small compart-

ment that looked like a bellows. After Helmholtz had made clear
the nature of timbre the vowel sounds provided an especial puzde,
for the vowels, being sustained sounds, are thus presupiably analyz-

able under Ohm’s law, and they can in addition be sung at various
pitches. Are the different vowels then simply different timbres?

368

AUDITORY PERCEPTION

Seemingly not, if voices of different timbres can sing the samevowel at different fundamental pitches. Before Helmholtz’s timeit

was recognized that there is a pitch quality to vowels, such thattheseriesU (asintrUth),0 (sO), A (fAthor),E (prEy),I (sEE)
ascends steadily in pitch, even on a falling cadence of the fundamental. Hence after Helmholtz it became an accepted fact thatvowel character is given in a sustained tonal complex by the intensification of certain components. This problem, whiclr exciteda great deal of interest and investigation during the latter half ofthe nineteenth century, recurs today with the new methods of analyzing sound. Of the several hundred papers on the subject, however, we can consider a few that are crucial.

There have been three theories of the pitch of vowels, (a) The
theory of lelative pitch makes the vowel equivalent to -timbre, apattern of the paidals present. Although this theory was not held
seriously by the important investigators, it was generally cited incontrast with the other two theories, (b) The theory of fixed pitch,
as it was called, was attributed to Helmholtz; its assumption wasthat the mouth cavity is shaped for the different vowels so as to reenforce, by resonance, different partials of the total harmonic complex. The particular partials reenforced would depend, of course,on the pitdi of the fundamental: for a bass voice the fifth partial
might lie well within the region of resonance for a given vowel,
whereas for a soprano voice, an octave and a half hi^er, the sec-

ond harmonic would fall within the same region, tliough not atexactly the same pitch, and would be reenforced to give the samevowel. Thus, in this theory, the pitch is fixed only approximately:
it is only the regionof resonance that is fixed, for the exact pitch

reenforced depends upon what partials happen to fall within theregion, (o) According to the formant theory of Hermann, the re-gion of resonance is so fixed that it responds with its own natural

frequency independently of the place of the harmonics of thefundamental tone. The resultant pitch formant, which determines
the vowel, is thus not necessarily a hannonic of the fundamental.

In ffieory, then, the formant is more definitely fixed than the reenforced harmonic of the ‘fixed pitch’ theory, but actually those who

followed Helmholtz generally managed to find some actual fre-quency which they stated as defining the position of the region ofresonance, whereas Hermaim’s method was such as to lead him to
specify general regions rather than exact optimal pitches.

PITCH OF VOWELS
There may be said to have been lour principal methods of determining the pitches of the vowels (cf. Table IV). (a) The early

method consisted in determining with tuning forks the resonancevalue of the mouth cavity when it was set to form die vowel, (b)Later the method of analyzing phonograms by Fourier’s analysis

came in. The early phonograms of spoken vowels were traced
on smoked paper on a kymograph, but Edison’s invention of thephonograph in 1877 provided so accurate a procedure that the results became highly complicated, (c)Along with these analyticalmethods there was the synthetic method of producing vowels.
Helmholtz did it with tuning forks. Whereas the first two methods

depend on the mouth for the specification of the vowels, the synthetic method depends on the ear. (d) Finally, there came in an-other auditory method in which pure tones were compared withvowels, or two tones were compared with each other with respect
to then' relative resemblance to some vowel. It is a reasonable question, for instance, to ask whether 950 c.p.s. is more or less likeAthan 900 c.p.s.

With this brief lesum^ of the research in mind, we are prepared
to understand the liistory. The reader sliould keep his eye on Table

IV as the discussion progresses.
Of the very early contributions one of the most important is thatof Kempelen who, writing in 1791 on the mechanism of speech, described the construction of an elaborate talking machine. He seems
to have proceeded by trial and enor in the construction of his ma-chine, arriving at no generalizations about the vowels or the otherspeech sounds. He gave, however, definite specifications for getting the different vowels by means of reeds and boxes of various

shapes, and it is quite clear that he produced the series of vowels

UOAEl by continuously reducing the concavity of the reenforcing
box. In a sense, tlien, he may be said to have established this orderof pitches for the vowels, although he did not make the generabzation.

Ordinarily the history of experimentation in this field is regarded
as starting with tlie Englishman Willis, who in 1829 published astudy of the vowels. Vowel-like sounds, he found, are given off bytubes in which the column of air is activated by a vibrating reed;
the particular vowel depends upon the length of the tube. The
seriesUOAEl he could get from a tube with a piston in it, pushing
Ho was able to establish onlyin the piston to change the vowel.

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PITCH OF VOWELS

371

ranges for the frequencies for the different vowels; the range forU, moreover, was so long that he could not specify it, and the tube
for I was so short that he was uncertain of it.

N evertheless. Table IVshows that his regions for A and E include most of the later specifications, and that his value for

0 is in the region fixed later. (Thefrequency for 0 has always been more reliably establishable than
the frequencies for the other vowels.) Willis also produced theseriesUOAEI by holding a watch spring against tiie teeth of awheel and speeding up the wheel (cf. p. 33S) The uncertainty of.

his results he explained by noting that sustained vowels are neverreadily recognized. In speech, he said, the vowels are easily identified because they come rapidly and contrast with

one another.

He denied that the vowel sounds depend on a pattern of harmonics present, and, in thus speaking, he originated the theory of
fixed pitch as against the theory of relative pitch.

In 1837 Wheatstone, who reviewed the work of Kempelen andWillis, went on to develop the physical theory of Willis’ findings,

thus establishing the fixed-pitch theory on firmer ground. Afterthat nothing happened to this problem until Bonders, Helmholtz

and Koenig undertook the investigation of the resonance values ofthe mouth cavity in 1857-1870.

Dondera, the Dutch physiobgist, was the first to publish. He

determined the resonance values of the mouth cavity for the various vowels (Tabic IV). Hebnholtz, later in 1857, showed what

happens when vowels are sung at the same fundamental pitch intoa clavier with the damper removed from the strings. For U thefundamental alone responded; for 0, the third harmonic; for A, thethird and fifth. Two years later he published a paper which laid

down the fixed-pitch theory, that vowel qualities are due to a reenforcement of partials in a fixed region of pitch Against the viewthat relative pitch (timbre) determines the vowel he argued definitely. Then, in the Tonempfindungen of 1863, he went into thematter thoroughly, thus getting his name attached to a theory
initiated by Willis. Next he determmed the optimal resonance valueof the mouth cavity for the different vowels, noting that resonancefor the higher vowels may be double. In the region of

E and I, forinstance, the mouth is shaped like a bottle witii a large neck; ac-cordingly there is one period of resonance for the total cavity andanother for a part, Hence both a high and a low frequency belong

AUDITORY PERCEPTION

372

to these two vowels. (Table IV.) The same result was found byMiller in 1910.

To validate his theory Helmholtz undertook a synthetic experiment. For the purpose he used the clang synthetizer, which we havealready had occasion to mention (p. 331). (It consisted of a seriesof ten tuning-forks, the first ten harmonics of 128 c.p.s., arranged

so that the relative intensities of the difl!erent harmonics could becontrolled. Fig. 51.)

With this apparatus he could set up any

timbre for the fundamental 128 c.p.s., and he could also, by intensifying partials in the right regions, imitate the vowels. These

synthetic vowels convinced Helmholtz, but, having in them too

few components to match actual speech, they would probably notconvince a modem psychologist. The clang synthetizer, elaborately
standardized by Koenig, stands in many of the older psychologicallaboratories, amonument to the classical days of psychologicalbrass instalments. It is usually known as the “Helmholtz vowel

apparatus."

Rudolph Koenig himself, having determined the resonances ofthe mouth cavity, published values for the vowel pitches in 1870,

The interesting filing about his data is that, placing U at hc.p.s,,= 235

he placed the other vowels in the UOAEI-series exactly anoctave apart—as did Kohler in 1910.

The study of the vowels by means of their phonograms was, tor
the most part, the achievement of Hermann. It is true that Donders

had used the records of spoken vowels recorded on a kymograph(phonautograph) in 1864, but Hermann, making use of the Edison phonograph, was the principal contributor by this method. In

1889-1894 he published a series of six “phonautographische Untersuchungen.” In the first of these he contented himself with a

Fourier analysis of the extremely complex phonograms of the vowels. In the last hecame to the view that the vowel-character, being

determined by the natural frequency of the mouth cavity, is wholly

independent of the fundamental pitch of the voice. Thus the determining frequencies for the vowels would ordinarily be inhar-

monic with the fundamental for the voice. Hermann named thesepitches formants. It is a paradox that, coming to this conclusion by
this method, he was forced by the analysis to find so many com-ponent elements, that—as in Table IV, based on his data of 1895

—he could give only ranges for the formants. In theory the formants should be absolutely fixed, whereas it is the harmonics of the

PITCH OF VOWELS

373‘fixed-pitch’ theory that would shift with the fundamental. In general, however, except for U, Hermann’s results accorded tolerably

well with Helmholtz’s and Koenig’s.

Hermann’s method was employed by D. C. Miller in 1916 withgreatly improved apparatus—he called the phonogram recorder aphonodeik—and the addition of a mechanical analyzer for the

cuwres. He was able to fix the pitches much more exactly than Her-mann, and in general his results were consistent with the others.
It is interesting to note that, like Helmholtz, he found double re-gions of resonance for vowels in the El half of the series.

Wc have already considered Jaensch’s production of noises byaperiodic activation ot his photoelectric siren (p, 364). ActuallyJaensch was more concerned with speech sounds than with noiseproper. The vowels he synthetized—so he claimed—by modulat-

ing the frequency iiTegularly. For instance, instead of cutting a—each wave sub—series of sine waves on the edge of the siren disk

tending 24° with fifteen waves to tire complete circumference^hemade the lengths of the waves 22°, 24°, 23°, 26°, 25°, etc., letting
each of these five wave-lengths occur three times in a fortuitousorder in the circumference of the disk, The result was a frequency

which fluctuated around the average frequency, correspontog toan average wave-length of 24°. Jaensch found that such fluctuation

makes the tone noisy; nowadays we know that irregular modulationof the frequency of a tone in this manner would tend to scatter

frequencies into regions adjacent to the average frequency. There

would be a mass of tones with an approximate but not an exact—a tonal noise, in

pitchfact. Jaensch regarded these noisy tones as

good vowels, a conclusion which led him to suggest tliat vowelcharacter is a qualitative dimension of noise. His specifications

were most general. He placed U at a frequency of 250 of his varying waves per second, and the other vowels at successive octaves

above— 0 at 500, A at 1000, and E at 2000. 1, which should havecome at 4000, was loo high for this method of syndiesis.
It was Kohler, iirvestigating the attributes of tones in 1910, whothought to compare simple tones with vowels. He used tuningforks, and, in the upper regions of frequency, the Gallon whistle.

Actually he was reversing the conventional argument. Instead offinding the vowels tone-like, he used his results to indicate that thetones are vowel-hke. that vowel-character or vocality is an attributeof tone. His results seemed to him to mean that the vowels UOAEIAUDITORY PERCEPTION

874

lie separated by octaves, as Koenig had said. Fixing on c, insteadof h, as the crucial point, he placed the vowels

UOAEI at 262, 525,

1050, 2100 and 4200 o.p.s. respectively. This was his theory, for theactual results fell somewhat off from the exact octaves. (See thecolumn for “Av." under K6hler in Table IV, the averages that
Modell and Rich computed from Kohler’s data for Kohler as observer.)

Most of KBhler’s predecessors had investigated vowels intermediate between UOAEI, such series as pooh (U),poe (O),pflto,po (A), pot, pat, pet (E), pote, peat (I), The present exposition
has omitted mention of these extra vowels. Kohler, having decided
that UOAEI are principal vowels, like RYGB in the series of hues,

proceeded to argue that intermediate vowels would thus be like—uo between U and 0 like orange between
R and Y. Such a system, accounting for oclave similarity in phe-the intermediate hues

nomenological terms, also suggests that there should be still otherprincipal vowel-qualities at octave intervals beyond the extremesof the UOAEI-series. The Galton whistle gives a hiss, am vowel,

at a high frequency, perhaps at 8400 c.p.s. Still higher up it goes
off into

a fff and finally ch (like the soft oh German sound in

Chemie), Kohler, writing in the period when the error in the calibration of the Galton whistle led to the belief that the upper limitof hearing may be as high as 50,000 instead of 20,000 c.p.s, (pp.

335 f.), tentatively placed fff at 16,800 and ch at 33,600 c.p.s. At
the lower end of the scale he suggested that an octave below
there is a low

mmm vowel nearUc.p.s., and Titchener enteredinto the speculation by hearing in the ramble of the Appunn reedfor 64 c.p.s. a continuative ooo. That made a series of ten principal

vowels separated by nine octaves from 65 to 33,600 c.p.s.;

mmm-V-O-ArE-l-m-fff-ch, Phenomenology was

not,

vm-

however,

destined to stretch quite so far. The system broke down when theexact octave relations could not be confirmed.

On the other hand, not only did Kohler’s determination of theactual frequencies of UOAEI reenforce the earlier findings, but hehimself was also confirmed, within the broad limits of tolerance

which this ^q)e of investigation required, by Modell and Rich in1915 and by Rich without Modell in 1919,

Recent investigations of speech sounds have been phonographic,
making use of the oscillograph to obtain a record of die wave form.
Analysis of such vowels shows a wide scattering in the auditory

ATTRIBUTES OF TONE

375

‘spectrum’ of frequencies. Fletcher’s account of them in 1929 is representative. Although the results do not contradict the generalitythat appears in Table IV, they show rather that total speech sounds
are ever so much more complicated. If this seems an unsatisfactory
result of so much experimentation, it must be remembered that avowel is in itself no very specific object for investigation. The same
person, hying to duplicate a vowel, may not succeed at aU in re-producing the same sound spectrum.

Attributes of Tone

The phenomenological description of sensory experience, as wehave seen in an earlier clrapter (pp. 19-27), tended to become
formalized by an enumeration of athibutes and the determinationof their laws of dependence upon the stimulus. All sensations, ofcourse, ‘had’ quality, that is to say, they varied in respect of aqualitative dimension. Quality was thus the important attributewhich usually gave the name to the sensation. Yet sensations also

had intensity, for they could vary in degree. Since quality was regarded as ie primary attribute, intensity was supposedly secondary, an intensity of a quality. That is approximately the relation

found in Wundt’s system. In 1893 Ktilpe formalized thedoctrine, (a) arguing that the attribute is an inseparable part ofthe sensation (the sensation disappears

if

any attribute is abol-ished) and (b) implying that the attributes of sensation are dis-tinguished from one another by being independently variable. Al-

though he added duration to quality and intensity as attributes oftone, he did not admit extensity as a tonal attribute.

The phenomenological description of a tone is, however, not exhausted when its quality, intensity and duration have been stated.

Tones have brightness, volume, octave similarity. Are these additional descriptive dimensions also attributes? On the ground thatthese aspects have to be included in a complete description, thatthey are, indeed, inseparable, the phenomenologists tended to
say Yes. The psychophysicists tended to go farther and inquire

whether, by quantitative experiment, all the alleged attributes canbe shown to be independently variable. It was, in fact, the psychophysical experiments upon tonal volume that eritidzed andchanged Eulpe's too simple doctrine.
In the decade 1910-1920, when phenomenology was becoming

AUDITORY PERCEPTION

376

important in experimental psychology and Gestalt psychology was

being bom of it, there was quite a flurry in tonal attributes. At leastnine important psychologists offered considered judgments about
the number of tonal attiibutes and their names, to the end that agreat deal of terminological and factual confusion resulted. If we

ignore intensity (loudness), which everybody admitted, the fol-lowing sentences give some idea of the situation in respect of the‘quahtative’ attiibutes.

Rivdsz (1913) wanted three tonal attri-butes: pitch, wcalUij (vowel-quality)
larity). Jaensoh
cality.

and quality (octave simi-(1913) said that tones have pitch and noises oo-

Max Meyer (1914), however, held that the dimensions ofhigh-low, large-small, and vowel-quality are all the same attribute, which he called vocalitij, getting rid of pitch as a term but

adding to vocality a second attribute, tonality (octave similarity).

Watt in 1914 used oolume to describe both the large-small andhigh-low dimensions of tone, and pitch for vowel-quaUty and octave similarity, achieving this extraordinary change in the meaningof pitch because the vowels, seeming to show octave similarity,

appeared to him to be the basic quality of tone. Stumpf (1914)
identified pitch with brightness, and allowed two other attributes,

volume and quality (octave similarity). Khhler (1915) had four
attributes; brightness, volume, vocality and pitch, the last of which

he, like Watt, used for octave similarity. Titchener (1915) lent his
auflrority to three; pitch,ity). Rich

volume and tonality (octave similar-(1919) investigated the independent variability of allthese claimants to attributehood by seeing whether they had, in

terms of stimulus-frequency, different differential thresholds, sothat they could vary independently when a single dimension of thestimulus is altered. He ended by agreeing with Stumpf that pitchis

not to be distinguished from brightness and that volume andtonality (octave similarity) are independently variable with re-spect to each other and to pitch. It was much later (1934) that
Stevens, on the basis of experimental work, added density to thelist.

In the following paragraphs we shall consider successively theseven more important proposals for attributes of tone. For the sakeof darity, we shall ignore the authors’ predilections for names, andemploy the ccanmonly accepted words. Thus the possible attributes
are:(1) Pitch, which varies predominantly with stimulus-fre-quency and applies to the high-low dimension. (2) Loudness, theATTHIBUTES OF TONE

377

new word for what psychologists called intensity before 1920.
(3) Brightness for the bright-dull dimension. (4) Volume forchange of extensity or size of a tone, since low tones tend to be
judged larger than high, and loud tones larger than faint. (5)Voccdity for vowel-similarity. (6) Tonality for octave similarity

Fraquencyi c.p.».
Fto. 57.

IsoPHomc Contoubs fob Poim Touxt ATTRiBuria! Stevens(1934)The slotidard tone

tlie diagram) has afrequency of 500 c.p s and an intensity of 60 db. The 'equal-budness' con-(corroipanding to the center oftour shows the locus of tliose combinations of frequency and intensity which
will give tones equal in loudness to the standard tone. The contours tor pitch,volume and density are similar. Tlie graphic relationships are considerably
altered for standard tones of different fr^uency and Intensity.

and thus presumptively for the varying disparity of the membersof inteiwals within the octave. (7) Density for the dimension ofcompactness (hardness) vs. rareness (thinness).

So well was isomorphism worked into the thought of psychologists before 1920 that it was more or less taken for granted thatevery attribute of sensation would correspond to some dimensionof variation of the stimulus—as pitch to frequency, loudness toenergy. Prom that simple view phenomenology broke away; psy-

chophysics after 1920 showed that the modes of correspondence,

being complex, are to be established oiJy by the experimental determination of the form of a functional relation. Thus it became

apparent that the total number of attributes is limited only by theAUDITORY PERCEPTION

378

number of relationships that can be established. This matter has
been discussed in Chapter 2 (pp. 26 f.).
1. Pitch. All tones have pitch; on this point there never was dissent, Tones vary inquali^ from what is called Ugh to what iscalled low. Galileo discovered that pitch varies with frequency, asimple isomorphic relation which held until Zunniihl in 1930 and
Stevens in 1934 showed that the intensity of the stimulus also affects the pitch. ( Fig, 57; also pp. 323 f. ) It is true that others before

1930 thought that pilch changes or ought to change with intensity,

but they lacked experimental evidence; neither did their guesses
agree as to the nature of the change.
2.

Loudness. Neither was there ever any question about tones’

varying in loudness, but the correspondence with the stimulus was

not so definite as it was for pitch. Sometimes amplitude of the wave

and sometimes its energy— the energy varies with the square of
the product of amplitude andfrequency—was considered the‘true’ stimulus to loudness, until, following the renaissance of audi-

tory psychophysics after 1920, it was realized that there is no sim-

ple isomorphic relation and that the functional dependencies haveto be worked out by experiment. Loudness was found to be a de-terminate function of energy and frequency, (Fig. 57; also pp,

33&-338 and Fig, 54.)3.

Brightness.

Low tones arc dull; high tones are bright. Is

brightness, then, just another term foi pitch, or is it a new attrib-

ute? Mach had argued (1886) that bright and dull, not Ugh andlow, are die truly descriptive terms for the qualitative continuumof tones, suggesting that the pitch-series results from a combinationin changing degree of bright with dull, just as the oranges result

from a combination of red with yellow. After Stumpf (1890, 1914),
Brentano (1907) and Kohler (1915) had all identifi^ pitch withbrightness. Rich (1919), failing to determine a significant differ-ence between the differential limens for the two attributes, took
this finding to mean that they do not vary independently.
later Stevens

Muchand the present author (1936), noting that higher

transients make a tonal complex bright, were inclined to equate

brightness to density.
4.

Voiome. The first relationship, noticed by Stumpf (1890), wasthat low tonq^ tend to be large and massive, whereas high tones

tend to be small. Stumpf was not concerned at that time with thelisting ofa formal set of attributes. Titchener, however, pro-ATTRIBUTES OF TONE

379

nounced volume an attribute in 1910, followed by Rich (1916),

who proved its independent variability by showing that the differential Rmens are larger than the limens for pitch

and vary as afunction of frequency in accordance with a different law. The volu-

mic limens, in fact, were for him approximately proportional to thelogarithm of the frequency, after the manner of musical intervals.

Thus Ogden (1924) suggested that volume, not pitch, may he thebasis for the musical scale.

Meanwhile the acousticians and musicians were using the word
volume as practically synonymous with loudness. When Halverson(1924), employing observers accustomed to make judgments ofvolume as frequency is varied, found that they could also discrimi-nate volumic diffei'ences with the variation of the intensity of thestimulus, he determined quantitatively the functional relation.

This finding made tonal volume into a joint function of frequency

and intensity, such that it ought to have been possible to equate
in volume a loud high tone to a faint low tone.

A heterophonicequation of this sort is, however, not easy to make and the firstexperiments failed. Stevens ( 1934), who finaUy hit upon the rightmethod, worked out the functional relation that is shown in Fig. 57.
This was the first study to make it plain that the criterion of thedifferentiation of attributes is not so much independent variability,

as Kiilpe had said, but rather independent constancy. Though it is

not possible to keep both pitch and loudness constant while vol-ume varies, nevertheless one can keep volume constant while both
pitch and loudness vary. This situation is realized when the fre-quency and intensity of the stimulus are varied concurrently along
fte contour of Fig. 57, which is the locus for constant volume.

The question has been raised as to whether tonal volume, as thus
established by Stevens, is a ‘true’ attribute of tone or merely an association, as of low loud tones with big instruments and high soft

tones with little instruments. Presumably the question is unanswerable; a learned attribute which shows constant functional relations
to the stimulus, which is judged immediately, and which exhibits

no large individual differences, is as ‘true’ as any other, Most observers make use of associated visual imagery in judging tonal vol-ume as they do also in judging tactual localization, but Stevens
found that a congenitally blind observer who used kinesthetic
imagery, made the same kind of judgments of tonal volume asseeing persons.

AUDITORY PERCEPTION

380
5.

Vocality. The work on the vowels left it quite indeterminate

as to whether vocality is an attribute of tone or simply the fact thatcertain pitches characterize the vowels. R^vesz ( 1913 ) was tlie first

person to label vocality an attribute. Kohler (1910), stressing theapproximate octave relation of the principal vowels, regarded intermediate frequencies as giving mixed vowels; thus Watt (1914)
identified vocality with tonality because of this apparent octave
relation. Rich ( 1919 ) , however, failed to get reliable limens for thediscrimination of vocality, and the view today is that vocality is not

something new in attributes, but merely the way die odier attributes sound.
6.

Tonality. It was perplexing for the psychologists to find that

their measures of pit^ did not correspond to the musical scale.

Some octaves had in them many more difference limens thanothers. Pitch seems, moreover, to change continuously from low tohigh through the gamut, whereas octave similarity implies a circular variation of some other attribute—a something whicli goesaround and around while pitch ascends, so that c-ness recurs once
per octave and so that there is a g somewhere intermediate be-

tween one occurrence of c and the next. Thus, under different
names, McDougall (1905), Brentano (1907), Rdvdsz (1913),
Kohler (1915) and Titohener (1915) have subscribed to a separate attribute of tonality. It was Meyer (1914)

who gave it thatname. Even Rich ( 1919), finding a set of limens that were not for
pitch or for volume, hoped that they might indicate the existence of
tonality. Figures for tones, analogous to the color solid, have been

constructed to include tonality. One such figure is a conical spiralline, in which pitch is thought of as

ascending vertically, volume

as measured radially from a central axis, and tonality as being in-

dicated droumferentially, c being on one side,

g on the other, andthe odier tonalities in between. Nowadays, with diminution of thephenomenological interest in tone, with the failure to get differential limens of tonality, and with the knowledge that the aural har-monics insistently apply the musical relations to tones, the needfor this attribute has

krgely evaporated. The octave is, so it isthought, the tonal distance for which die harmonics—and there

always are aural harmonics-^terpenetrate maximally.
7.

Deiwity.'Because both were similarly related to the frequencyof the stimulus, density

was originally identified with volume.

Titchener ( 1910), in defining the volumio attribute, said that “deepAUDITORY SPACE PERCEPTION

381

tones appear very large and diffuse, and high tones very small andoonoentratcd." It was Stevens (1934) who noted that large-small

and diffuse-concentrated are different dimensions, and, by plotting
the isophonic contours of each against frequency and intensity,

demonstrated their difference, (See Fig. 57.) If stimulus-frequency
is increased,volume decreases and density inei’eases, for the hightones tend to be small and concentrated.

On the other hand, if

stimulus-intensity is increased, both volume and density increase,for the loud tones are large and dense. Thus it comes about that aloud high tone may match a soft low tone in volume, as we havealready noted, but that it takes a loud low tone to match a soft

high tone in density. So far tliis discovery has helped more to clarify
the definition and establish the nature of an attribute than to throw
light upon other phenomena of hearing.

Auditory Localization
Sights and touches have extension, size and shape. The conventional view of psychology has been that tones and noises do not,although recently tonal volume has.done much to establish its claim
as a sensory attribute. Because they denied extension to tones, thenineteenth-century psychologists for the most part doubted theexistence of any ‘truly’ auditory space perception, and sought forways in which touch and kinesthesis could provide spatiality fortones. Here we have an excellent example of the way in which sys-

tematic belief influences experiment, for the experimentalists at
the end of the century were mainly concerned with the genetic

problem of how non-spatial tones get themselves placed in space.

The problem was, they thought, to describe and understand a subjective space of

which the conscious individual is immediately

aware. Some geneticists, thinking in the tradition of Lotze, Helmholtz and Wundt, tried to decide how auditory space can be built

up by the mediation of otlier sensations. Others, nativists like
Stumpf and Miinsteiberg, argued that auditory space is Itself immediate. Along in the present century, when tlie problem of theimmediacy of perception had lost much of its scientific meaning,
this difficulty disappeared; psychologists

then asked merely, as

Lord Rayleigh, the physicist, had always done: Cairthe organism
discriminate the relative positions of tonal stimuli, and, if so, how?
Spatial discriminatinn-ULsightand touch is possible because theAUDITORY PERCEPTION

382

visual and tactual receptors are spread out spatially in such wisethat a pattern of stimulation can be impressed upon them. In thecase of hearing, although, according to soiae theories, there is apattern of pitdh impressed spatially on the organ of Corli in the— he no spatial pattern.

inner ear, there seemed—to introspection^toNevertheless, inasmuch as the organism possesses two ears in different places, physiologists recognized quite early that this dis-placement of one ear with respect to the other provides the basis[‘

for a crude and simple localization. The trouble was that psychologists were later distracted from this basic fact by their desire tosolve the empiricistic-nativistio problem of auditory space.

Another way in which presuppositions hindered progress appeared in connection with the phase relations of tones, Helmholtz,

who had studied phase, came to the conclusion that it makes nodifference in the operations of Ohm’s law or in the perception of

timbre, vowels or any other qualitative pattern; and from this decision there arose the commonplace that the organism “cannot per-ceive phase.” Thus, it was said, if the organism cannot perceive

phase, then phase cannot be the basis of auditory space perception. Eventually, of course, it was

shown that the difference ofphase between the two ears is one of the bases of auditory localization,

but the conclusion was prevented for many years by afaulty isomorphism:

iftones have no attribute that correspondswith phase, then one cannot perceive phase, and, out of what hecannot perceive, he certainly cannot build up a perceptual space.

With this perspective of the way in which dieory interfered withdiscovery, we can now turn to the actual history of the experiments

on auditory localization, and in so doing we shall use Stumpfs
convenient terminology. Stumpf (1916) called the simultaneous
stimulation of the two ears by the same stimulation dioHo, the si-

multaneous stimulation of the two ears by different stimulations
dichoUc, and the stimulation of one ear only monoHc. In this connection it is important to note that a total stimulus can at the same
instant be both diotic and dichotic; for instance, the hinaural stim-

ulus may be diotic as to frequency and dichotic as to intensity,
as it is in the common situation for the intensitive localizations of
tones.

—The empiricists—^Berkeley, James Mill and Bainffie localization of sound to experience.

all attributed

In the application of thisprinciple they could be most explicit about heard distance, forDICHOTIC LOCALIZATION

383

there they argued that a sound whose intensity is known can haveits distance inferredfrom the loudness with which it is perceived.

On the means by which auditory direction is perceived they weremore vague, but in general they held that oSier sensations mustassist.

Bain asserted, for instance, that, if one man speaks fromamong a row of persons, we cannot identify the speaker unless werecognize the quality of his voice or see his lips move. Johannes
Muller, the physiologist, writing at this time (1838), noted thatthe perception of direction must depend upon the different positionof the two ears; it must be, he said (hitting incompletely on thetruth ), the diEerence in intensity of the sound at the two ears or thechange of intensity at one ear when the head is moved which provides the cue for direction. As showing how visual perception may

determine the perceived direction of a sound, he also cited ventriloquism, an ancient art.

Tte ejgisimaataLlitfirature seemsJo begin with Ernst HeinrichWebe r’s observation in 1846 that when two watches are placedheard-simultaneously, and each can be referred correctly to its
prQp.e£jside, Here Jhen, is.ffie initial recognition of the fact that the

primary diiufinsion o£ auditory localization is left-right, the directi

on of dichoticity of binaural stimulation.

At once there arose the question as to how there can be an
auditory space when sound has no size. Eduard Friedrich Weber,

one of Ernst Heinrich’s younger brothers, decided that sound cannot be localized when the head is under water and the external
canals of the ears are filled widi water, except that right and left

can be correctly distinguished. Thus, he argued, localization, except the gross distinction between left and ri^t, is a tactual matterand depends upon tactual intensities, presumably the sensationsin the external aural canals, He tried tying the pinnae of the twoears back against the head and having the observer cup his handsin front of his ears, so as to form artificial pinnae turned toward therear.

In that situation so many bcaUzations were reversed fromfront to back, that Eduard Weber concluded the front-back localization to be dependent upon intensity—-the intensitive difference

which comes from the ears’ being aimed forward.
After the Webers nothing much of importance 'happened fortwenty-five years. In 1876 Folitzer reported the case of a man witha monau ral defect who always localized sounds toward the side

AUDITORY PERCEPTION

384

of the more sensitive ear, and then in the same year Lgrd.Rayilei^

took up the problem. He stood with closed eyes on a lawn with acircle of assistants around him.

When one assistant spoke, he tried

to localize the voice, finding that he could be correct within a few

degrees. With low pitched tuning-forks, however, he was not so
successful, a fact which led him to propose that dichotic intensity
is the basis for localization.

Having figured out how the intensities

Iof tones would vary at the two ears when the sound comes from tlieside, he showed that the intensitive difierence would be great forhigh tones, less for low, and negligible for tones whose wavelengths are as much as four times the circumference of the head(ca. ISO c.p.s. and loss). Actually he got no difference in accuracyof localization for 128 and 256 c.pj5. The next year, as the result of

more experimentation with forks, he was able to show that localization depends on the binaural ratio of the intensities at the twoears. It was from thiswo rk of Rayleigh’s tliat the phras e binawal

ratio—meaning always a ratio of intensities—camo into the literatpre. Rayleigh pointed out the implications of his result: for every
position in front of the observer Aere is a corresponding position

behind where the binaural ratio is the same, a place which is confused with the region in front in the same way that front-backlocalizations in the median plane are confused. Thus he demon-

strated altogether (a) that noises (voices) are better localized thantones, (b) that high tones are better bcaHzed than low, (o) thatthe binaural intensitive ratio is crucial for localization, (d) that
there is confusion between front localization and any symmetrical
position in back, and (e) that there is no confusion. between rightand left. A considerable contribution, even though it neglected
phase difierence.

Other support came to the ‘intensity theory’ at this time. Von
Kries and Auerbach argued in

187Y—as they well might withHelmholtz’s theory of mbewusster ScMuss still in the air—that localization is an inference as to position based on auditory intensities.

The observer must, they said, (a) estimate the intensity ateach ear, (b) judge the relations of the two intensities, and then(o) conclude as to the location. Inference takes time, and theyfound that the time of localization, longest for the median plane,
diminished aS the sound (the crackle of a spark) was

moved

toward one side, becoming minimal at the side. Silvanus P. Thompson, who inaugurated the ‘phase theory’ in 1878, also found inten-

DICHOTIC INTENSITY

385

sitive difference determinative of localization in some cases, In thesame year Tarohanow, having set up two telephone receivers, one
at each side of the observer, showed that with equal intensities thebilateral stimulation “fused” into a single

sound in the medianplane. His report was brief, but Urbantsohitsch in 1881 reported

more thoroughly on the method. Equal intensities give, as he putit,“a combination field” of sound, which, as the binaural ratio ischanged, migrates toward tire louder side. Then in 1879 Thompson
built his “pseudophone," a faame to fit over the head and carry ateach car a small shield which could be rotated, acting as an artificial pinna.

When these pinnae were reveised, back to front, theWhenlocalization of sounds tended to be reversed, front to back.

the pinnae were arranged to favor the sound in one ear and shield
the other ear, the localization moved toward the favored ear. This

experiment, therefore, siippoited die intensity theory. Later, in
1882, Thompson showed, as had Rayleigli, that intensitive differ-ence is more effective at high frequencies than at low, but that low
notes may nevertheless be localized by their higher harmonics.

The quantitative measures of localization as a function of dichotic intensity came later.

Bloch’s results in 1898 (correcting Miin-sterberg’s; nide infra) are classical.

He measured the angular dif-ferential threshold, finding that it was least in front at the medianplane, larger in back, and laigest at the sides. Although there isnever actual confusion between the two sides, a small change inangle at the side is not noticeable; whereas in the median plane
there is confusion between front and back, though a small deviation from the median plane is readily noticed.

Matsumoto, working with Scripture at Yale in 1897, was the firstto use a sound cage (but ef. fteyer’s helmet, infra), a sphericalmetal frame woik centered about the observer’s head, so as to markvarious angular positions at a constant distance from the head(Fig. 59). With a telephone receiver at each side and the relative
intensities of their buzzing noise controlled, he measured the ac-

curacy of localization, thus duplicating Bloch’s function. He also

used the cage with a single telephone receiver placed at various
positions. Later more thorough studies confirming the general re-lation of the binaural intensitive ratio to localization were made by

A. H. Pierce in 1901 and Ferree and Collins in 1911. Recently Stein-berg and Snow (1934) have shown exactly how the sound-shadowof ihe head affects the binaural ratio at various frequencies of tone.

,

AUDITORY PERCEPTIONAt 2S0 c.p.s. there is practically no diminution of intensity, for flie
waves are long enough to get around the head. At 1000 c.p.s. thediminution is about 8 db, and at 10,000 c.p.s. about SO db. There is
no doubt that intensity is diohotic for tones of high frequency thatare out of the median plane.

Meanwhile there had been much discussion of this problem interms of the genetic theory of space perception. It was Laborde’s

Fic. 58.

Sound Helmet; I^er

Fm. 69. Sound Cage; Fnraci(1887)(1901)The ends of the 26 wire pointers

The frame provides a system ofmark 26 direchons from the head andspherical coordinates for the location

were used to locate the stimulus. The
system is: r=s right, ileft,click in die telephone receiver. Later== under, 0= before (uom),= behindover, uii

o—(iiintam).

or the stimulus, which is usually acages made it possible to bring thestimulus below the horizontal pmne.

suggestion in 1881 dial die semicircular canals may have some-thing to do with the way in which uon-extensive sound gets itself
built up into auditory space. To show that injury to the canals affects the reflex movements of the head in the plane of the injured

canal, he cited the classical experiments from Monrens on. If thelocal signs of sensation are given their spatial function by bodily

movement, as Lotze and Wundt bad held for vision ( pp. 234-236 )then die canals may be the means by which sound is given its spa-

Pr^er in 1887 performed elaborate experiments
which he interpreted in terras of this theory. Actually his investiga-

tial position.

tion is interesting because he was the first to simplify the problem

of locating the stimulus by building a sound helmet ( Fig. 58 ) , a de-

ORGAN FOR AUDITORY SPACE

387

vice that fitted over the head and carried 26 wire pointers, deter-mining 26 equidistant positions from the head, Preyer’s pupil, Amheini, in the same year put out a dissertation reljdng on the same

method and ending in the same theory. Miinsterberg was a little
more explicit in 1889. He determined the accuracy of localization
as greatest in front of the observer, less at the sides and least behind—a functional relation that Bloch, as we have seen, presently

cor-

rected. Since the movements of the head are less accurate thefarther the head is turned from the front position, he saw in these(incorrect ) data a reason to believe that head movements, and thus

the semicircular canals, contribute to auditory localization.

Against this tlieory of the semicircular canals Breuer argued(1891) that it would be "completely impossible” for the canals
to mediate direction of sound, since the stimulus, after passing

through the external aural canal, would have no way in which it
could excite the three internal canals differentially. And von Kries(1891), who presented an experiment to show that two sounds, anoise and a whistle, can be localized simultaneously (as E. H.

Weber had noted for two watches long before remarked that thehead could hardly move in two directions at once. (One wonders) ,too what these motor theorists would have said to the intracranial
localizations that were stressed so much later in connection withthe phase theory. How does the head move to get inside itself?)

Also against the canal-theory was one touch-theorist, Celle, whoin 1886 reported on a patient of CJharcot’s. The patient was tact-

ually anesthetic all over his face and at both ears. Since he could
not, so it was reported, localize sound at all. Gelid was inclined torevert to what had been Eduard Weber’s theory, that auditory
localization depends upon touch.

This account brings the research pretty well up to the end of thenineteenth century. In the twentieth century die interest in die
genesis of a subjective auditory spatial system disappeared, and inits place the questions of the function of

diohotic phase and timearose. For a while there was conflict between what were called the‘intensity theory,’ the ‘phase theory’and the ‘time theory.’ Only

after 1920 was it realized that the investigations indicate, not threetheories of localizations, but different physiological means by which

the same localization is effected.

»

The ‘phase theory,’ as we have seen, began with Silvanus Thompson. In 1877 he observed binaural beats. He had two tuning-forks.

888

AUDITORY PERCEPTION

one of 128 c.p.s. and one slightly mistimed from 128, and led thesound by rubber tubes from one fork to the left ear and from theother to the right eai, He heard beats This observation has always

proved difficult, for each sound seems continuous and yet the beats
are heard. Although Thompson did not then note any movementof the fused sound, the next year he reported an experiment inwhich the sound from two forks, 258 and 512 c.p.s., was conducted
through a single tube which branched and led to both ears. Whenhe rotated one fork about its axis so as to change its phase relation
to the other, the sound of that fork migrated from the front to therear while the sound of the other fork stayed put. He also an'anged
to take these two frequencies into two telephone receivers and thento lead the sound as before thiough tubes to the ears. When he re-versed one telephone electrically so as to change its phase withrespect to the other, the localisation changed as before. At thattime these results were not accepted because they seemed to contradict Helmholtz’s dictum that phase cannot be perceived.

Though Lord Rayleigh had considered the possibility that phasemay determine the localization of sound, it was not until 1907 thathe proposed the ‘phase theory.’ Taking his cue from Silvanus
Thompson, he put two forks of 128 c.p.s. in isolation, mistuned one
sUghdy, brought each sound separately by a tube through a wall,

and adjusted the terminal tubes so that the observer could just fit
his head between their ends, one ear to each opening, He heard

binaural beats as Thompson had; and, although the observation

was difficult, both he and Lady Rayleigh concluded that the beating sound moved back and forth from right to left. Now, as twotones beat, their phase relation passes through all possible values;
thus Rayleigh concluded, since 128 &p.s. is too low for dichotic
intensity to be effective, that this movement, and hence the locali-zation of low tones in general, may be due to the phase relation.

As soon as the great Rayleigh had made this pronouncement.
More and Fry produced results that they had obtained back in1902 and had presumably suppressed because of the improbability
that phase is ‘perceived.’ They had arranged to bring a frequency

thiough a tube which divided and led it to the two ears. In one sideof the divided tube there was a slide extension, fixed so that thepath to one e^ could be made longer than the path to the other,and the dichoRc phase relation of die tones changed accordingly.

Working with both 512 and 320 c. p^., they wei-e able to make theDICHOTIC PHASE AND TIME
perceived tone shift from one side to the other simply by altering
the relative lengths of the two paths. This experiment was repeatedmuch more thoroughly in 1908 by Wilson and Myers, whose apparatus is shown in Fig. 60. There could be no doubt that low
tones, tlius administered, are localized toward the side of the lead-

Fro. 60.

Appabatus fob Djchotic Phase:

Whsom and Myebs (1908)

The sound from the tuning-fork at K is divided in the tube T, whichslides into S

and out of V (or conversely), altering the relative lengths ofthe paths from T to the head H. P and 0 are soft pads at the observer’sears;

M end N are standards supporting the pads. SS

the observer from seeing how

isa screen to keep

T is shifted, and the scale DS measures the

TSACF exceeds in length the path TVBFQ by someamount less than half a wave-length of the frequency of K, the observer
shift of T, If the patli

localizes the tone toward his left

0?)-ing phase. Within variations of half a wave-length, the localization

moves toward the earlier stimulus. So obsessed, however, were
Wilson and Myers by Helmholtz’s rule that they were at some unnecessary pains to argue that a phase difference of this sort might

be changed into an intensitive difference before it became effective
for localization.

In 1920 the 'time theory’ was introduced, first by von Hombostel

and Wertheimer and then by Klemm, who had worked independently. Von Hombostel and Wertheimer sought to work out withdiscrete sounds the time differences that would give differences of
localization,and to show that these times are the same as those

implied by the experiments on dichotio phase. Stimuli diotic as totime give a median localization. When the time-mterval between
the two stimuli is increased, the perceived sound starts to migratefrom the median plane at about 30 microseo. (.03 millisec.), a

AUDITORY PERCEPTION

800

very short time indeed. As its diohotioity in time is increased, thesound migrates toward the earlier stimulus and becomes anchoredat the side at about 630 microsec, Klemm, however, found great
variability in his results from observer to observer and from obser-

vation to observation. The very least time difference for deviationfrom the median plane he determined as 2 microsec., which is anunbelievably short interval for a physiological differential. The single sound, anchored at one side, brealcs up, he discovered, into two

successive sounds at about 2000 microsec, (2 millisec.). Klemm

was inclined to reduce the ‘time theory’ to an ‘intensity theory,’
for he showed that dichotic intensity can be equilibrated against
dichotio phase.

A louder later sound in one ear may balance afainter earlier sound in the other, so that localization becomes medial. Von Hombostel and Wertheimer, on the other hand, sought

to reduce the ‘phase theory’ to the ‘time theory.’ In 1920 they had

every right to do so, for in 1912 Adrian had established the aU-or-none principle of nervous transmission, A simple harmonic excitation, it was now probable, must be resolved in the nervous sys-

tem into a series of discrete discharges, so that dichotic phase must
become in the organism a series of pairs of dichotic times. Von
Hombostel and Wertheimer did not, however, make this explicit
appeal to recent physiology.

Although there has been a great deal of research in this field
since 1920, the effect has been mostly to bring the different ‘theories’ together. The present author in 1926 showed

how phase andtime are identified by the all-or-none principle and how time could

be the physiological equivalent of intensity. Trimble in 1928 alsobrought the various researches together, making Raylei^’s original distinotion explicit by attributing dichotio phase to 5ie locali-zation of low tones and dichotic intensity to the localization ofhigh tones. The upper limit for the effectiveness of dichotic phasehe placed in the region of 512 to 1700 c.p.s., but all the indications
have been that the refractory period of the auditory nerve-fiber
limits the effective frequencies to 1000 or less.

Id 1934 Stevens and Newman investigated the localization ofpure tones on a raised platform out in the open air where refiectedsounds are minimal, Under these conditions they showed that the
localization of low tones from 60 to 1000 c.p.s.

isaccurate, thus

finally laying the ghost of Rayleigh’s old suspicion that low tonesi»re riot

Ipca^ble at all. Above 1000 c.p.s. localization gets poor))

THEORY OF AUDITORY LOCALIZATION

391

and is worst at some point between 2000 and 4000 c.p.s. Then it
improves again, until at 10,000 c.p,s. it is quite as precise as it was
at 1000. TTiey analyzed this function into two, indicating that

dichotic phase is eSective for low tones and dichotic intensity forhigh tones, that one of these principles begins to work after theother leaves ofi, and that the poor localization near 3000 c.ps. isdue to the fact that there is just not enough overlap of these two

Fio. 61. Ebross op Looauzation of Tones as a Function of Fse-

qomcT! Stevens and Newman (1934)
The solid curve shows how the eirors inoiease up to shout 3000 c.ps.
and then decrease. The dashed curve shows the theoretical (and very nearly
the observed) effectiveness of dichotic phase for localization. The dottedcurve ^ows the observed effectiveness of dichotic Intensity for bcalization.

Adapted from Stevens and Newman.
basic functions to make the organism as adequate in this criticalregion as it is at both extremes of frequency. ( See Fig. 61.
All this work shows that diohoticity is the primary factor in de-termining the localization of sound; yet dichoticity alone is effective only as

a cue for the right-median-left dimension, whereas

sounds are actually well localized in tridimensional space, in front
or in back, above or below. Recently Wallach (1939) has shownthat the kinesthetic system of the head, be it muscular or vestibular or both, is integrated with tlie auditory system when the headis allowed tomove in such a way as to provide furdier specificationof the locus of the sound. If the head is moved, the subject can‘decide’ (by “unconscious inference,” Helmholtz would have saidl

whether the sound is in front or back. If rotation of the bead abouta vertical axis does not change dichoticity, then the localization ismade for the position at which the dichoticity of a sound would notAUDITORY PERCEPTION

392

be changed by such movement, i.e., above tlie head. Wallach has

made it quite clear that the localization is not purely auditory, but
the product of an integration of auditory, kinesthetic and, whenthe eyes are open, visual factors.

This history of auditory localization illustrates altogether theeffect of systematic premises upon experimental research.

In thelast century the problem centered on the way in which a subjective spatial system can be built up out of auditory experience. In

the present century perception has become the organism’s capacity
to discriminate the differentiation of the world of stimulus.

Wewant to know the functional relations, and we want to understandthem in terms of lire physiology and physics of the perceptual situation, Finally we are beginning to discover tliat we must trot bo

content with too simple a physiology; many different capacitiesof the organism may be used to determine a single localization.

Not much escapes the organism that could be of use to it.

Notes
The usual references to
M4m. Soo. roij Sot. Montpellier are

Beats and Combination

77, [n.v.].

Tones

incorrect. This historical matter has

For
their

tile

discovery of beats

anduse in the determination ofrelative frequencies

and in tuning,see J. Sauvenr [as reported], Sui fa

determinationd’un

Aced. Scl. Pails,
esu 134-140.

son
1700,

fixe,

Wist.

131-140,Wbeen woikod Out by A. T. Jones,The

discoveryofdifference

tones,

Amer. Phijs. Teacher, 3, 1935, 4951, which gives the references andquotations and shows that the usual
attribution of

the discovery of dif-ference tones to Soige is incorrect.

G, Tartini's discussion of diftones, see his Tmttato dimusica secondo la vera scienai delP
armotUa, 1754, esp. 13-19. G, A.
ference

On die beat-tone theoryof thedifference tone, see Romieu, he.

first

at,,

L. Lagrange, Rcchcrches surJ.

k nature et la propagation du son.

Sorge’s earlier mention of difference

Miscellanea

tones is in his Amoeisung xur Stim-

Imv.], reprinted in his Oeuores,

muttg und Tmperatur sowohl der1867, 39-148, where see osp. 143-

Orgfiwerke, ah auch andere Instiumente, sondarlich aber des Claolers,

144; T. Young, Oudines of experiments respecting sound and light,
Phil. Trans., Ft. I, 90, 1800, 106-1744,

[n.v.l,muHkallschen

and Vorgemach derComposition,

1745, 13, [n.v,].

J.

Tauiinensia,

130-133, or same

1,

150,

osp.

B. Bomieu’s in-

P/iii

Tians.

Ft.

dependent discovery and menlionof a beat-tone theory is in the rare
AssmbUe publique de la SoclHS
royals des Scfences tenue dans laande saUe de THdtel de Vllle deontpellter, h 16 iScembre, 1751,

1,

abridged,

18,

1759,
I,

title,

1809,

604-628, esp. 816-618; Koenig, ha.
cit.

infra.

For G. U. A. Vieth on combinaUeher Combinationstone, Ann. Phtjs. Ghent. Halle,21, 1805, 265-314. For G. G. Halltion tones, see his

NOTESand theory of dif-

strbm’s discovery

Timbre and Aural
Harmonics

ference tones of higher orders, see
his Von den Combinationstone, ibid.,

100, 1832, 438-466.

H.

Helmholtz’s

important paper

Ueber Combinationstone,

Ann.
Chem., 175, 1856, 407-540.
r^inted in his WissenschaftUche
Abhandlungen, 1, 263-302. He also
published two other minor papers
on tills topic in the same year, but

is

Phys.

On timbre, see H. Helmholtz,
Ueber die Klangfarbe dec Vocale,Ann. Phys, Chem,, 184, 1859, 280290, rmrinted in WissenchaftUche
AhhancUungen, 1, 397-407; Die
Lehre von den Tonempfindungen,
1863, Chap. 5 and 6.

On auralharmonics,

Helm-

see

Tonempfindungenhis other principal contributions toholtz,Die Lelira non
den Tonemp/indungen, 1863, Cluip.
7 (combination tones). Chap. 8(beats). Chap. 11 (beats of combination tones), or same chapters

8in later eds. or Eng. trans. It

in-sion of pure tones, as if they could

Helmholtz

be heard, see any ed.. Chap. 5, sect.

the

topic

terestine

are

in

that

note

to

is

ed.,

[op,

cit.),

where he618-620,1670,

shows that they occur in connection
with combination tones, and 2 ed.,1865, 595-598, which is before herealized

For

fact.

this

his

discus-Lord Rayleigh, Theory of Sound,departed so far from the beat theory

1.

of difference tones that he dealt with

2 ed., 1896, IL 453-460, esp. 458-

combination

with466, repeated Helmholtz’s argument

The view that combination tones

and insisted that the ear is likely totransmit sound asymmetrically. The

tones

and

frst

beats second.
are subjective was supported by R.

odier citations

Koenlg, Ueber den Zusammenldang

are R. L.

zweier

Ann.

Tone,

Chem.,

Phys.

233,

1878, 177-237) French trans.

in hisQuehues expiriences d'acou-

on aural harmonics

Wegel and C. E. Lane,

The auditory masking of one pure
another andtone byrelation to tlie

its probabledynamics of the in-1883, 87-148; W. Preyer,
Akustische Vniersuchungen, 1879,

ner ear, Phya. Rev., 23, 1924, 266-

11-43.

Speechstiqua,E. B. Newman, S. S. Stevens andH.

Davis show die complexity of

thisproblem by themodem tech-nique of registering the electricalpotential from the cat’s ear. Factors
in the production of aural
ics

harmon-and combination tones, J. acoust.

Soc,

Amer.,

also

Stevens

1937,

9,

107-118; seeand Davis,

flooring,

285,

H.

272-274;esp.

and Hearing,

Fletcher,

1929,

176-

180; A space-time pattern theory ofAmer,,
1930, 311-343, esp, 313-318; S.
hearing,

acoust.

I.

Soc.

1,

S,

Stevens and E. B. Newman, On thenature
not.

of

Acad.

aural
Set.,

harmonics,

Proc.

22, 1938, 668-672.

S. S. Stevens and
H. Davis, Hearing, 1938, 184-207,

In general, seeesp,

184-196.

1938, 197-201.

In

generalHelmholtz,

on these topics, see
Chaps. 7-11;
cit,,

Fusion and Consonanceop,

89-94,For Helmholtz on consonance in

140 f„ 184-208, 22^247. Stevens
and Davis dismiss fully the relationof beats and vibrato to omplitude
modulation and frequency modulation, and of combination tones end

relation to coincident harmonics, see

Stevens and Davis, op.

cit.,

any
ed..
Tonempfindungen,Chap. 10 and 11. For C. Stumpf’s

histheory of fusion, see his
chologte,

II,

Ton^-

1890, passim, esp. 127-

distortion

218. For o^er details and the gen-which is introduced by the transmission through the middle ear.

eml importance of this topic at thattime, see 0. Kiilpe, Gnmdriss deraural

harmonics

totheAUDITORY PERCEPTION

394

Eng.

lians.>

tonal hearing in general, see S. Bel-

1895, sects. 43-48j E. B. Tilohencr,
Eiperimemd Psuchology, I, ii, 1901,

Ueber die Zusammenklang einer
wenig verschiedener
Tdne, Z. Psychol, 67, 1913, 281276; A. G. Ekdidil and E. G. Bor-

Psycholo^ie,

oi

189S,

329-337.

On

ferences

among

quaUlatlve

the
the

dif-

perceptions of

the musical intervals, see W. Kemp,
Methodes und Experimentelles zur

ey,

grbsseren Zahl

The

ing,

Amer.

pitch

of

masses,tonal

Lehre von der Tonversclimelzung,

Psychol, 46, 1934, 452455; G. V. Bdkdsy, Zur Theorie desAfch, gas. Pstjohotf 29, 1913, 139-

Hiirens,

2S7j C. C. Kratt,Soma qualitative

aspects of bitonal complexes, Amur.
J. PsijchoL, 32, 1921, 490-515; E.
M. Edmonds and M. E. Smith, The

J.

Phys.

Z.,

SO,

721-

1929,

745, esp. 731 f.; S. S. Stevens and
IL Davis, Hearing, 1938, 98 f. (ontonal masses), 102 f. (on Bdkdsy).

sical intervals, ibid., 34,

Thermal noise was first discovereda random variation in electricalpotential in a thermionic system due

291. A.

to the thermal ^itation of the elec-

phenomenological description of mu1923, 287M. Bmes determined degrees of fusion for the 24 intervals
witliin the octave that ate given by

as

trons

by W. Sc&ttky, Ueber spon-tane

Slromschwankungen

in

ver-

a quarter-tone scale: The fusion ofschiedenen Elektrizitatsleiteru, Attn.

non-musical intervals, ibid,, 88, 1927,
624-638. Pratt’s coup de grdoe toitStumpfs theory of fusion is
Tonal fusion, Psychol. Reo.,

his

41,

Phys., 57, 1918, 541-567.

the

"shot

was

On noise, see Helmholtz, Tanmpfindmgen, Chap. 1 (first part) andChap. 6 (last part), in respect ofwhich compare any of the first
three eds. (1863 et seq.) with the
4 ed. (187'i] or the Eng. trans., inorder to see the change of view. The

bycalledFletcherthermal noise,”ticalthermalnoise,’^

psychischen Ptocesse,
einfaohsten
Arch. gas. Physiol, 11, 1875, 403-

Ohrenheflh.,Ton-

1890, 497-514; O.
Grundriss der Psychology,

pmihologte,

11,

See

Stevens

Sd, 24, 1938, 285-

Masking432, esp. 416-418; V. Hensen, TJn-

Arch.

turnedthe masking effect of thermal noise,
Proc. not, Acad,23, 1888, 69-90; C. Slumpf,

when

as revealed through experiment on

274.

Wahmehmung

and,

it

“electricaland Davis, op. cit., 57 f., 98 f,; H.
Fletcher, The mechanism of heating

Experimentelle Untersuchungen derder Gerfiusche,signifi-into sound by a loud speaker, "acous-

other references cited are S. Exner,

iiber

134-136.

1933,

aconsticalcance cl the effect was realize,

Noisetersuchungenlater

it the “Schottky effect.” See
E. L. Chaffee, Theory of Theimlonlo

calledVacuum Tubes,
Later when the1934, 86-97.

He called

otherseffect”;

The three papers cited on masking are A. M. Mayer, Researches inacoustics, Phil Msg,, 2, 1876,

500-

507, esp. 503-505; R. L. Wegel and

E. R. Jaensch, Die Natur dermensch-G. E. Lane, Audiinry masking andthe dynamics of the inner ear, Phys,
Rev.,
H.
1924,
266-285;23,lichen Sprachlaute, Z. Sltmesphysiol,

Fletcher, The mechanism of hearing

Kiijpe,1893, sects. 14, IS, or Eng. trans,;

47,

1913, 219-290,esp.

256-269.

Watt, Psychology of Sound,
1917, 34-41, presented a similar viewH.

J.

and discuss^ '[he literature.

On the indefiniteness of pitch of
tonal masses and their relatlan toas revealed

through experiment on

the masking effect of thermal noise,
Proc. not. Acad. Sd., 24, 1938, 265274. See also Fletdier, Speech end

Hearing,

1929,

167-18'/;

Stevens

and Davis, Hearing, 1938, 208-217.

NOTES
Because Mayer could hear a fainttone of 1024 c.p.s. through a loudtone of 1280 c.p.s., hethou^t tliat

895

70. 1870, 031-933, reprinted in his
Quelijues experiences d’acoustiyue,

1882, 42-46.

ate" the lower, but consultation of

The first of L. Hermann’s PhonoauLographische Untersuchungen is in

Wegel and Lane's obart in Fig. 56

Arch. ges. Physiol, 45, 1889, 582-

shows

820, and five more follow in thesame Ardhiv up to 1894. Importantthe higher tone could not "obliter-

that

the

tluresholdmust nevertheless1024-tone

the

or

have

me

been raised considerably.

Untersuchungen mittels desneuen Edison’sehen Fhonographes,
ibid.,

Vowels1892,

53,

because1-51,

ittakes account of Edison's discovery,

The early work cited Is W. de
Kempelen, Le m^cenlsme ie la parole suioi de la description dune
machine parlante, 1791, esp. 394464 (De la machine parlante),
where 447 f. gives the speeiBoations
for producing the vowels; R. Willis,

On vowel sounds and on reed oiganCambridge phil.

ipes, Trans.
,

231-288.

1829,

esp,

Soc.,

231-250,and Nachtrag zur Untcrsuchung der
Vocalcurven, ibid,, 58, 1894, 264279, because it introduces the term
formant. For actual values of theinharmonic formants, see his Weitere Untersuchungen iiber das Wesen
der Vocale. ibid., 61, 1895, 189204. The work of D. C. Miller, theon the analysis of vowels,

physicist,is described in bis Science ofMu-with the vowel frequencies on p.
243; C. Wheatstone, a review ofsical

Kempelen and Kratzenstein,[London ana] Westminster Seview,
28, 1837, 27-41, reprinted in ScL
enttjic Papers of Sir Charles Wheat-withstone, 1879, 348-387.

modulation can result in a set ofWillis,F. C. Dondera” chief contributions

are Ueber

Natur

die

der Vocale,Arch. Holland, Beltr. Nat. Ueilk.,

1,

1857, 157-162; Zur Klangtarbe derAnn.

Vocale,Chem., 199,on the phonographic
Phys.

1864, 527 f,,
method; Die physioloeie der spraaklanken,[mv,).

1870,

contemporaneous

Helmholtz's

contributioas

Nat, Heilfe.

reprinted

in

his

Phys.

As

219-290.

adjacent frequencies, seeS.

S. Ste-vens and H. Davis, Hearing, 1938,

234-241.

The important paper of W. KShler's in thisconnection is his Akust-

Untersucliungen

ische

II,

Z.

Psy-

chol, 58, 1910, 59-140, but see also
other papers in

his

and

84.

54.

ibid,,

this72,

seriesin

1909-1915.

by J. D. Model! and G. J. Rirm, A
preliminary study of vowel qualities,

I,

Chem., 108, 1859, 280-290,

Ab-I, 397-407; Die Lebre

Amer.

Psycdiol, 26.

J,456; C.

J,

esp.

1915,

453-

A study of tonal
121-164,131-143.

On sound spectra for vowels, besides

he,Miller,

cit„

see

H.

Fletcher, Speech and Hearing, 1929,

28-33.

Good

general disciissions of thisliterature are toRayleighverse voyelles, C. R. Acad. Set. Paris,

Sound, 2

caractraistiquesRich,

attributes, ibid., 30, 1919,

des di-fixes

47, 1913,
frequency-

WlssenscHaftlichevon den Tonempfindungen, 1863 orlater ed. or Eng, trans.. Chap. 5.
sect. 7 (in general and on analysis),and Chap. 6, first half (on synthesis). For B. Koenig, see his Sur les
notes

how

to

Die

Sprach-The confirmation of his findings isreprinted in WissenschaftUche

handlungen,

Slnne^hyslol.,Z.

laute,

in hisismenschlichen

derHolland.

1,

1882, 395 f.; Ueber die Klangfarbe der Vocale, Ann.

Abhandlungen,noisy siren

his

Natur

1857, 354 f.,

Ueber die Vocale. Arch.
Beitr.

areSounds, 1016, 215-251.

E. R. Jaensch’s synthesis of vowels(J.

be found in Lord

W. Strutt), Theory of

ed.,

1896,

H, 470-478;

AUDITORY PERCEPTION
F. Auerbach's Akustik, in A.

Wink-

Handbuchder Physik, 2ed., n, 1909, 681-705, esp. 691701, which has a bibliograpny. Lesselmann,and Fletcher,satisfactory are Miller
tocc, citt.

Attributes

339 f.; W.
Untersuchungen305-348.

esp.

Akustisclie

Kiihlet,III,

Z.

PsycIioL, 72, 1915, 1-192, esp. 177-

192. G. j, Rich failed to distinguishbetween die limcns for brightness
and pitch in op, oil. (1919), 143149, 153-158 For a suggesdon diatbrighlness and density might beequated, see E. G. Boring and S. S.

For the history ol research andopinion on the tonal attributes andStevens, The nature of tonal bright-

fm many more references than these514-521.

ness, Proc. not.

Acad. Scl, 22, 1933.

A study

On volume as a tonal attribute,of tonm attributes, Amer. 1, Psychol,see Stumpf, Tonpsychologle, I, 207-30, 1919, 121-184, esp. 122-127.

211; op.

cii,

Tildiener,

A Text-book of Psychol-notes give, see C,

Rich,

J.

On the theory of attributes, see,besides

Chap.

2,

pp.

Kulpe,

Gtundrtisaer

19-27,

0.

Psyclwhgle,

1893, or Eng. trans., sect. 4; S. S.
Stevens,The

attributes

oftones,(1914),

ogy, 1910, 94 f.; Rich,

study

of

149-153;

1919,

op.

M.

R.

exper.

J.

13-22;

1916,

1,

B,

A preliminary

volume,tonal

Psychol,

339; E.

cit.,

Ogden,

Proc. not. Acad. Scl, 20, 1034, 457-

Hearing, 1924, 66-69,

4S9j E. G. Boring, The relation ol
the attributes of sensation to die di-ume as equivalent lo tonality); H,

mensians of die stimulus, Pftil.
2, 1935, 236-245.

funedon of intensity, Amer.

Sci.,

chol.,On the dependence of pitch upon
the intensity

of

the

M.

stiinulus,see

165 f. (vol-Halverson, Tonal volume as a
1924, 360-367;

35,

Psy-

J,

Stevens,

The volume and inlensity of tones.
Ibid,,

1934,

46,

G. Zurmiilil, AbhSndigkdt der TonhShenempfiudung von der Laut-intensity);stiirke und ihre Beziehung zur Helm-48,

897-408(volumeas a joint function of frequency and1934,

Are tones spatial?, ibid,,142-150 (judgments ofhollaschen Resonanztheorie des 116-

tonal volume by a congenitally blindrons, Z. Sinnesphyslol, 61, 1930, 40-girl)'

86; Stevens, The reladon of pitch to

On vocality as an attribute, see
G. R4v6sz, Zur Qnmdlegung der Tonmchologle, 1913, 84-90; W. Kbhler, Akusdsoho Untersuchungen II,
Z. Psychol, SB, 1910, 59-140 (onintensity,

7.

ecoust. Sac. Amer., 6,

1935, 150-154. For one guess (onlyhalf correct) as to how pitch would

vary with intensity, a guess
beforejust

Zurmiihl’s

made

paper

ap-

the vocality of tones)

181 f,(onpeared, see L. T. Troland, Frinei-

1915,

ples of Psychophysiolosy, U,

status of vocality);

222

1930,

chological.

On brightness as die phenomeno-

hearing,analysisBrilJ.

and op.

die

cit,,

attributive

H. J. Watt, Psy-

andtheoryPsychol,

7,

of

1914,

logical equivalent of what is usually

1-43, esp.

Mach, Zur Analyse der Tonempflndungen, Steingsber. Akad, Wiss, Wien, inath.-nat.
Cl., 92 ( 2), 1885, 1283-1289; F.
Brentano, Vntersuchungen zur Sin-musical *‘pitoh” to vooality); Rich,

called pitch, see E.

1907, 101-109; C.
passim,Tonpsychologle,

nesphpsiologie,
Stuinpf,

13 f.,On tonnll^ and octave shmiarity
be called pitch, quality
see W. MdDougall,
Phystohgical Psychology, 1905, 72 f.;orft

tonality,

Brentano, op.
R4v6sZ|VI

Meyer,

Psychol,

1914,

of

ios of vocality).

whether

Untersuchungen zur Tonlehre, Ber.
exper,(relation

op. cit., 1910, 131-143 (psycho-phys-esp. II, 1890, 272-276; Ueber neuere

Kongr,

27 f,

ett,,

1907,

101-109;1913, 4-75; M.
Vorschlage zur akusHschen
op.

cit,

NOTES
Teiminoloaie, 2. Fstjchol, 88, 1914,

3,

115-119 (introducing the term tocit., 1915, 177192; Titdiener, A Be^nnet's Psy-

8,

nality)! Koliler, op.

1915, 52; Bicb, op, di.,1919, 158-162. On tonal figureswith a ciieumferenttol dimension for
cholagy,AA, Ruckmlclc,
newtone qualities, Psychol, Rev,, 36, 1929, 172-180, who

tonality, see C.

classification of397
3, Pt C

Chap.

imagination); Bk.

Pt 3(ventriloquism;

5,

sect

Chap.

2,

h^

(intensitive difference

tween ears and when head is
moved); or later ed., or Eng. brans.
The contributions of the two Webers are E. H. Weber, Ueber die
Umstlinde dutch welche man geleitet wird manche Empflndungenauf aiissere Objecte zu beziehen,gives a history and states that M. W.

Ber.

Dcobisch in 1848 was the first person to suggest that this dimension of

228-237; E. F. Weber, Ueber den

tone

is

ibid.,

circular.

On density, see Titohener, op. dt,,
1910,

exper,

J.

Tonal denslW,

Stevens,94;

Psychol, 17,

58^

1934,

592.

Localization

1901, see theA.

excellent account of

H. Berce, Studies in Auditory

and Vised Space Perception, 1901,
28-51 et passim, 204-209 (bibliography, somewhat inaccurate). After 1901, see C. E. Forroe and B.
Collins, An experimental demonstia-

tlon of the binaural ratio ns a factor
inauditory

Psychol,

localization,

22,

Amer.

250-297,

1911,

I,

esp.

250-271; 0. C. Trimble, The theoryof sound localization: a restatement,
Psychol Rev,, 35, 1928, 515-523;
S,

S.

Stevensand H. Davis, Hear-

167-183, which gives theing, 1938,

Wise.,

1848,

2,

Gehorsorgans,des29-31. There were

1851,

E. H. Weber, 17951878 (Weber’s law), W. E. Weber,
1804-1881 (famous physicist), andE. F. Weber, 1806-1871,
For the man who localized soundtoward ffie side of his better ear,fibrea brofliers:

A.

see

On

the history of this topic up toGes,

sSchs.

Mechanismus

Siudien

PoUtzer,

Paracussis

Arch.

loci,

libcr

die

OhrehheiH,,11, 1876, 231-236,

W. Slrutt’s)(J.
On our peicepUon ofLord Rayleigh’s
papers are;diieotion of a source of sound,

tire

Proc.

Mvs.

1875-1870

Assoc,,(1876), 75-84 (experiments on thelawn); Acoustical observations, Phil.

Mag., 5 set, 3, 1877, 456-464, esp.

456-458 (toaural ratio and frontback confusion); On our perceptionof sound direction, ibid,, 6 ser., 13,1907, 214-232 (phase experiments
and theory).
Erqierunents

supporting

tensity theory were

J.

the

hi-

von Kries andF. Auerbach, Die Zeitdauer emfach-current facts.

On the use of dichotic, diotic andster

Vorgauge,

psychisclierArch.

1877, 297-378, esp, 321-

monotic, see C. Stumpf, Binaurale

Physiol,Tonmischung,Mehrheits5cbwelle und337; J. Tarchanow, Das Telephon
ab Anzeigei der Netven- und Mus-Z.

Mitteltonbildung,

Pswchol.,

75,

1916,330-350, esp, 340 f.
For the Kn^ish empiricists on localization, see Pierce, op. cit., 7-

kebtiome beim Menschen und den

27, where

bantschitscb,

is

also

a discussion ofnineteenth-century space theory inThieren, St. Petersburger
enschrlff,

iol,arguing for an auditory space un-

585.

Pierce himself

supported by other senses. Joharmes
Miiller’s diseussion of theseisin hismatters

Handbueh der Physiologic

des Menschen, U, 1638, Bk. 4, sect

1878,

Zur

med.Wo^353 f.; V. UrLehre von derSohallempfindvmg, Arch. ges. Phys-wasthis connection.

3,

24,

1881, 574-595, esp. 579-

Sllvanus P.

’Thomp^’s coutribn-

dons to this topic (be was an important scientist

known best for his

accomplishments concerning electric-

AUDITORY PERCEPTION

398

magnetism and the theory of theily,

dynamo ), are his Phenomena of binaural audition,

Mag., 5

Phil.

ser.,

1877, 274-276 (binaural beats);

4,

ibid.,(phase383-891

1878,

6,

Ueber

ErkennendasderSchall-richtung, Z. Psychol, 1, 1890, 236^1. Against the canal theory, seean experl on the caUeber die Function der Otol-

Breuer,J.
nals,

theory); The pseudoplrone, ibid., 8,

ithen-Appaiate, Arch, ges. Physiol,

1879, 385-390; ibid., 13, 1882, 406-

48, 1891, 195-306, esp. 295-302.

esp. 415
mined by higher harmonics),
Later contributions on the effectRayleigh, op.

(localization

415,

of dichotic intensity are E.

deter-

Bloch,

Horen, Z. Ohrenhellk, 24, 1893, 25-85, esp. 53-85(accuracy of localization as function of azimuth); M. Matsumoto,Dasbinaurale

Besearcbes on acoustic space. Studies
Yale patjchoL Lab,,
1901,

1897, 1-75,

5,

A H. Pierce, op.

13^7;

esp.

1-209;

Ferreeandeit.,

Collins,

C. Steinberg

ap.

alt.,

1911;

].

W.

B.

Snow,

Physicalfactors

andinauditory perspective. Bell Syat. tech.
13, 1934, 245-258, esp.

].,

250-253(diminution of intensity by soundshadow of head at different frequen-

On dicliotic pliase, besides Lord
cit,,

1907, see L. T.

More and H. S. Fry, On the appreof differeoces of phase ofsound-waves, Phil. Mag,, 6 ser., 13,1907, 452-459; H. A. Wilson andciation

G. S. Myers, Tlie influence of binaural phase differences in the localisation of sound, Brit.

J.

Psychol, 2,

1908, 363-385.

On dichotic time, see E. M. von
Hombostel, Ueber der Wahmebmung

derSitzungs-

Schallrichtung,ber. preuss.

Akad. Wtss., 1920, 383-

396; 0. Klemm, Ueber den Einflussdes binamalcn Zeitmiteischicdea auf
die Localisation, Arch. ges. Psychol,40, 1920, 117-146, esp. 123-129.

For summary and evaluation, seecies).

On the semicircular canals in re-

E, G. Boring, Auditory theory withlation to auditory space perception,

specialsee J.-V. Labosde, Essai d’une ditermination ezpirimentale et morpho-

ume and localization, Amer. J, Psy-

logiquedufonctionnel

tdle

des

canauz semi-circulairs. Bull. Sac.
Anthfopol Paris, 3 see., 4, 1881,797-801, 819-840, esp. 834-840;
W. Proyer, Die Wahmehmung der
Schallri^tung mittelst dec Bogengange, Arch, gee, FhyetoL, 40, 1887,

586-622 ( 588-609 is experimental
and includes tire sound helmet, and609-616 is the ampullar theory);
F. Amhelm, BeiSrage

mr Theorie der

Localisation von Schoffemp/indungenmittelst der Bogangdnge, 1887; H.

Miinsterberg,

Beltrage

airexpert-reference tointensity,vol-chol, 87. 1926, 157-188, esp. 164173; O. C. Trimble, The tlieory ofsoundlocalization:

Heo.,

Psychol.

85,

The experimental
tensity,arestatement,

1928, 515-523.
synthesisofin-phase and time as determi-

nants of localization is in S. S. Stevens

and E. B. Newman. The localization of pure tones, Proc. not. Acad.
Sci., 20. 1934, S93-59B; Tile localizationof actual sources of sound,

Amer.

J.

Psychol, 48,

1936, 297-

306.

For H. Wallach’s demonstration

way in whiclr movements ofhead extend the range and in-of themeateBen Psychologie, 2, 1889, 182234, esp. 192-215 for the canalfunctions and 215-234 for the ex-theperiments.

Scballriehtung, Psychol Forsek, 22,On

die patient

ears, see ? Gelid,
billtdau

widi anesthetic
B61e de la sensi-

du tympan dansbruit,

C.

K.

See,

rorientation
Biol.

7

ser.,

1886, 448 f. On double simultaneous localization, see J. von Eiles,S,

crease the precision of localization,
see his Ueber die Wahmehmung der1938,

238-266;

On sound localiza-

tion, I. acoust. Soc. Amer., 10, 1989,

270-274; The
head movemeots and vestibular and visual cuesrole ofinsoundcho!., 27,

localization,J,

1940, 339-368.

exp.

Psy-

Chapter 11

AUDITORY THEORYNINETEENTH-CENTURY dualism separated phenomenal
fact

from physiological theory. Having established theprincipal laws of vision or of hearing or of association, thepsychologist then asked how they could be ‘explained’ in terms of

the physiology of the retina or the ear or the brain. In a simple

psychophysical parallelism conscious process had always to hecorrelated with physiological process, In general, the investigators

paid more attenhon to the qualitative than to the intensitive dimension of sensation, and to the sense-organ than to the brain. That

was natural. Quality, being the primary atbibute, should be considered first.

Johannes Muller’s doctrine of specific nerve energies formed thebasic theory of qualify: a change in quality means a change in excited nerve fiber and thus in the place of origin of excitation in thesense-organ. Until the all-or-none law of neural transmission upset
that simple isomorphism in 1912, sensory intensity seemed as if it

must bo simply the degree of this excitation. Thus it was MiiUer’s
doctrine which in part fixed attention so exclusively on the senseorgan, where the spatial difiEerentiation of specific energies would

have to originate; yet it is also true that knowledge of sensory
physiology has always migrated inward from the stimulus toward
the brain. In the seventeenth century it was an achievement to getvisual stimulation as far in as the optical image on the retina; inthe nineteenth man began to ask how such a colored image gets
itselftranslated into a neural pattern in the optic nerve; in thetwentieth we are actually considering the brain. Similarly in hearing, at the beginning of the nineteenth century, investigators werestill demonstrating

how sound gets from outside the body into theaural labyrinth in the skull; whereas in the latter part of the cen-tury they were, stimulated by Helmholtz’s theory of hearing, con-cerned with the processes in the cochlea. Although that (iange

was partly due to physiological discovery in the middle of the cen-

AUDITORY THEORY

400

tuiy, there was also a further shift of interest that ran ahead ofphysiological knowledge.

Men made suggestions about how theear works; they advocated them on insufficient evidence, A theoryof hearing—not Helmholtz’s, but manyothers—thus became an

uncertain mixture of physiological fact and physiologist’s speculation,an ‘as-if physiology. Any theory of sensation—from 1870

to 1910,say—was adequate if it could describe imaginary physio-

logical relations which ‘explained’ a majority of the psychologicalfacts without contradicting many physiological facts. In the pres-ent century speculation has become less reputable, and the theories
of hearing are being reduced to the factual physiology of hearing.

Before Helmholtz
The gross anatomy of the ear has long been known. Empedocles(ca. 490-ca. 435 b.c.)discovered the inner ear, and Galen (129-

199 A.D.), naming it the labyrinfli, regarded it as the essential
nervous organ of hearing. Galen described the pinna and its muscles, the external meatus, the drumskin, and the distribution of die

nerve to the labyrinth. About the middle ear he had, however,
little to say,and certainly he knew nothing of the essential stnio-

ture of the labyrinth.

After Galen there was a long period of anatomical observation,

concerned often with the structure of the ear, as the copious footnotes of Haller’s EUmenta physiologiae ( 1763 ) show. It is enoughfor us here to realize that the details of aural anatomy began toreveal themselves in the sixteenth and seventeenth centimes. Bar-

tolomeo Eustachi wrote De auditu organis in 1562, describing
there and in a set of essays dated a year later, the ossicles, the tensor

lympani and the Eustachian tube. He did not discover this tube;

Alcmaeon(sixth century B.C.)

knew that there was an opening

between lie mouth and the ear. Later G. Casserio in 1600 gave amore extended description of the tympanic membrane, the ossicles,
their muscles and the gross structure of the cochlea, and C. Folio
in 1654 described the semicircular canals. The whole subject was

brought into excellent systematic shape by G. J. Duvemey’s thor-

ough treatise on the ear in 1683.
In this 'f/sy it came about that Albrecht von Haller, considering
the ear in 1763, knew as much about its gross anatomy as the mod-em psychologist needs to know. He described the external auricle.

ANATOMY OF THE EAR

401

the auditory meatus, the elastic tympanic membrane (conical in-ward and vibrating for sound), the tympanum, the Eustachiantube for adjusting air pressure, the three ossicles (malleus, incus,

and stapes), the tensor iympani and two (though actually there
is only one) other muscles, the oval

window and the round window

opening into the labyrinth with the stapes closing the former, thevestibule with the "nervous pulp” in i^ the conical cochlea withits

two and a halt turns, its spiral plate and its vestibular' and tym-

panic canals, and the semicircular canals. About the ampullae ofthe canals he did not know, nor about the microstructure of thecochlea. Assuming that the canals are organs of hearing, he said

that the functions of the cochlea are obscure; but he made, nevertheless, a conjecture about the cochlea that anticipated Helmholtz’s

resonance theory by one hundred years. Actually he noted thatthe “transverse nervous filaments” between the spiral plate and thewall of the cochlea become successively shorter as lire tip of thecochlea is approached from the base, and he suggested that these“nervous cords, continually shortening their lengths, [are] by thatmeans adapted to an harmonioal unison or consonance according
to the variety of acute or grave sounds, so as to tremble together
in the same time with most of them, namely, the longest cords inthe basis of the coclilea, with the grave sounds, and the shortest

cords nearer the tip or apex, with the sharper sounds.” He was, ofcourse, wrong in detail. The transverse fibers in the cochlea are

not nervous; and the long ones are situated, paradoxically, at thenarrow tip of the cochlea, and the short ones at its broad base.
Nevertheless Haller, in noting the existence of fibers and of thetapering space for them, actually did suggest resonance as themechanism whereby acute and grave sounds may be separated in
the ear.

Because the necessary knowledge about the microscopic anat-omy of the inner ear waited upon the impovement of die compound microscope about 1830, ftere was not much important progress made in the first half of the nineteenth century. Cooper in 1801

described cases in which the tympanic membrane and the bonesof the middle ear had been lost and in which hearing, after an
initial deafness, recovered surprisingly well, although the original

sensitivity was not entirely regained. Wollaston, who glaimed to beable to increase or diminish the air pressure in his middle ear byblowing or sucking through his Eustachian tubes with his mouth

402

AUDITORY THEORY

and nose closed, described in 1820 the clicking noises made bychanging pressure on the tympanic membrane and the way fa

which acuity is reduced by such unequal pressure. That the function of the Eustachian tube is to equalfae air pressure on both sides
ot the tympanic membrane became pretty clear, although J ohannes

Muller ( 1838 ), for one, was not wholly convinced of this function.
Savart in 1824 managed to show that the tympanic membrane vibrates when a sound impinges upon it He put sand on the mem-brane, as Chladni had done wilh metal plates, and observed its

movement when the ear heard a sound.
Sir Cliarles Bell fa his Anatomy of the

Human Body in 1809 dis-cussed the topic of hearing at length, repeating the standard anatomical facts that Haller had cited. Supposing the entire labyrinth
to be the organ of hearing, he suggested that the cochlea, so much

more highly developed in quadrupeds and man, may function for
the finer auditory discifaiinations

and for musical perception.

Since there aie, he supposed, from 400 to 500 distinguishable
pitches, and also as many loudnesses, the cochlea would have to

respond differentially to as many as 20,000 different tones.
BeU’s discussion is especially remarkable, however, for his correct apprehension of the function of the round window. At thattime it was coming to be supposed—-and Johannes Muller still held
this view in 1838—that the ossicles conduct sound directly to theoval window and that the air of the tympanum conducts it to theround window, affording thus alternative modes of transmission.

The fact that hearing recovers after the tass of the ossicles supported this view. Bell pointed out that the stapes, up against aclosed vessel filled with liquid, which is practically incompressible,

would be unable to move at al except for the fact that tire roundwindow provides relief. He was of the opinion that the direct
action of the soimd upon the membrane of the round window
could not be very great, partly because air fa the tympanum would
he a less effective conductor than the bones and partly because
the action at the round window, if considerable, would oppose
the action at the oval window so that the two effects would tend
to nullify each other.

He even suggested(

correctly ) that the posi-tion of the round window would, therefore, in part determine thecourse of the,movement through the cochlea from the oval window.

He did not, however, apply this logic to the semicircular canals.

MECHANISM OF THE COCHLEA

408

which have no relieving membrane, and ought therefore not tofunction with the activation of the oval window.

In 1824 Flourens published his first findings indicating that thesemicircular canals operate in the reflex orientation of the organism. His chief papers on this subject appeared in 1830. Eventually
this discovery was to be established, making it clear that the canals

do not function in hearing. (See pp. 538-543.) New fact is, however, slow to be accepted; Johannes Muller in shaping his theoryof hearing considered neither Bell’sargument about the roundwindow nor Flourens’ evidence about the canals.
Muller, then, in his authoritative account of the ear in 1838, re-verted to the theory that sound is conducted in two ways throughtho tympanum—by the ossicles to the oval window, by the air tothe round window. After he had undertaken research on the trans-mission of sound from one kind of medium to another, he con-cluded that conduction would be more effective from the solidbones to the liquid in the labyrinth than from the air to the liquid.

He thought of the sound as being transmitted through immobile
ossicles in the way that sound passes through any solid body, forhe assumed that the incompressible liquid in the labyrinth would
prevent tliese bones from moving. Supposing too that the sound istransmitted from the stapes to the canals and from the round win-

dow to the cochlea, he suggested that the lesser effectiveness oftransmission through the round window might be compensated forby the much greater amount of nerve spread out within the cochlear spii'al.

The problem that Ohm’s law was to solve flve years

later Muller recognized, but, not realizing how Fourier’s theorem

would apply, he hazarded the solution that primary and secondary

maxima and minima of a compound wave might excite the nervewith the different component frequencies. That was not an adequate analysis of the problem.
Itmust be remembered (pp. 70-72) that at this same time

formal promulgation was given by Muller to the law of specificnerve energies, a law which held that difference in quality depends

upon difference in the nerve excited. Muller himself applied theprinciple only to the differentiation of the five senses, but Natansonin1844 extended the principle to separate qualities within the

single sense—to red, yellow, blue, temperature, touch, sweet, sour,
bitter and the simple smells. When, however, Natanson lacked theAUDITORY THEORY

404

boldness to suggest that every pitch must have its own specificenergy, that extension of the prindple was left for Helmholtz to

make. That Helmholtz had such courage of conviction as to suppose the existence of more than 5000 specific energies for hearing(with a separate fiber, of course, for every energy) was one reason why both Muller’s doctrine and Helmholtz’s theory became
so important. The logic was sound, but it contradicted habitualmodes of thought.
Just at the middle of the century the problem became tire beneficiary of the new wave of research in microscopic anatomy, madepossible by the improvement of the microscope. The new tech-niques were applied to the study of the inner ear. Corti’s study ofmammalian ears came out in 1851, Reissner’s in 1851 and 1854, andKdlliker’s in 1854. The organ of CorH, Corti's rods and Reissnet's

membrane are terms that perpetuate these contributions. This was
the sort of information available to Helmholtz in his first formulation of his theory, though later Hensen’s studies (1863) caused

him to revise his theory. It was not until 1884, however, that Retzius published his classical description and charts of the humanear,

ie drawings that have for so loirg been copied in textbooksof physiology and psychology. Thus it was in this period of about
thirty-five years that tire

most important work was dotre on the

microscopic anatomy of the inner ear: the form and dimensions of
the organ of Corti and certain iirferences as to its probable kine-

matics were all worked out The psychologists who needed physi-

ology for speculative theories now had it

Resonance Theory of Hearing
The resonance theory of hearing, a scientific achievement of firstimportance and one which has dominated work in this field during
the eighty years since its inoeptioir, was formulated by Helnrholtz
in his Tonempfindmgen in 1863. It is definitely a product of Helmholtz’s clear thinking, of his ruthless logic and scientific objectivity;

nor are we belittling these attributes of Helmholtz’s if we also notethat 1863 was just about the right time for such a theory. The necessary facts and premises were at hand for his use.

To make ihe theory Helmholtz drew upon four bodies of information until then largely unrelated. (1) In the first place, heknew the physiological acoustics of the eai>—that sound is con-

HELMHOLTZ’S THEORY

405

ducted from the tympanic membrane through the movement of theand confined to the cochlea by theossicles to the oval window

position of the round window, which in turn allows the stapes tomove and its displacement to he transmitted through the cochlea
but not through the semicircular canals, Thus his theory depended
upon Charles Bell’s observation about the function of the roundwindow (1809) and Mourens’ estabUshmenl of the non-auditory
function of the semicircular canals (1830). Johannes Muller did

not use these data ( 1 838 ) ; Helmholb did. ( 2 ) In the second place,—as Haller and Bell and MuUer had not—someHelmholtz had

knowledge of the microscopic anatomy of the inner ear; tliis wasdue to tlie work of Coiti ( 1851) and others who had taken advantage of the improvement of the microscope to examine the receptor

mechanism of the cochlea. In this respect his theory was somewhat
premature in 1883 because, choosing then the wrong microscopic
resonators (Corti’s rods), he had later to make a change when

Hensen’s histological research became available. (3) Tlien he hadfor use Muller’s doctrine of specific nerve energies, a rule that dif-ference in quality always means difference of conducting sensory
fiber. It was his ‘ruthless logic’ which

made him extend to all thepitches the principle tliat Muller had proved only for the differentiation of the five senses. Helmholtz, regarding Muller’s theoiy asestablished fact, compared its importance for psychology to the im-portance of the theory of the conservation of energy for physics;
yet,

since

accepted,

its

application

to hearing has

never been entirely

we must regard his extension of the law more as apremise than a fact. Helmholtz, moreover, was handicapped byhaving no good psychophysical data on the number of discriminably different tones. He took Seebeck’s value of 1846, whichshowed the number of pitches to be of the order of thousands, nothundreds or tens of thousands. (4) Finally, Helmholtz had Ohm’s

law of 1843, which depended in turn upon Fourier’s theorem of1822 and which had been given great importance by Helmholtz’s

own studies of vowels and timbre in the 1850’s. Because it was clearthat the ear makes the same analysis as would be made by a large
set of resonators, it followed that the ear must in reception be aresonating organ. It remained only for him to identify in the microscopic anatomy of the cochlea the appropriate resonators. Putin this way it seems almost as if Helmholtz’s elaborate argument
for the theory amounted to little more than a statement of the ob-AUDITORY THEORY

406

vious, but it was Helmholtz’s achievement to bring unrelated data

together and in so doing to make their mutual significance obvious.

After all, the best logic is obvious.

Helmholtz chose in 1883 the rods of Corti as the probable resonators. Corti bad described them clearly.

The rods along with thewhole organ of Corti are large at the tip of the cochlea and small atthe base. The facts that we have reviewed in the preceding paragraph asserted the existence of a graded series of resonators; andhere actually was a series of objects, graded in size and so placed
as to stimulate, if they vibrated, the hair cells in which the nerve
fibers originate. Naturally enough, Helmholtz took them to be theresonators. Later in 1863, however, Hensen published two studies.

One showed how the particular hairs in the hearing sacks of Crustacea respond by resonance to particular tones, thus making theresonance ot organic structures plausrble and eventually persuading Hensen to adopt a theory of human heating in which the hairsof the hair-cells are themselves the resonators. The other paper wasa study of the structure of the cochleas of men and mammals whichshowed that the basilar membrane is a 30-mm. trapezoidal strip,
consisting of a series of transverse fibers of graded lengtlis, varying

from about .495 mm. at the tip of the cochlea to .041 mm. at its base—an ideal series of resonators, resembling a liarp or a set of piano
strings.

In 1869 Helmholtz in an article changed his opinion andargued for the fibers of diis membrane as the essential resonators,

In tihose theories of hearing that appeal to resonance to accountfor Ohm’s law, the basilar membrane has ever since, with few ex-

ceptions, been regarded as the resonating system.

There were five chief difficulties with Helmholtz’s theory, andmost of the other theories that it provoked were attempts to meetthese difficulties. Let us enumerate them so that we can have themin mind.

(1) It was necessary to find an adequate set of resonators in the
inner ear, Hensen’s measurements showed the ratio of the longest
basilar fiber to the shortest to be about 12, and later figures showedeven a smaller ratio. A ratio of 12 accounts only for a range of thi-ee

and a half octaves, whereas from 20 to 20,000 c,p.s. there are tenoctaves. Some persons rejected the theory on this account. Only

much later did Gray (1900) note that the shorter fibers might also
be under greater tension and Roaf ( 1922 ) that the longer fibers are

RESONANCE THEORIES

407

die most heavily loaded by the columns of lymph that move withthem.
(2) The small size of the organ of Corti oi’eated skepticism. How

could such tiny structures resonate to such large waves? A tone of

100 c.p.s. has a wave-length of about 330 cm., which is eleven times
the length of the entire basilar membrane and about 700 times thelength of the fiber that is supposed to resonate to it. This argument

was not physically sound: the whole wave does not have to bewithin the cochlea at once for its frequency to be effective at one
point. Various theorists, nevertheless, tried to meet the objection

by constructing tiny camerae ocusHcae to show that they would
resonate. None of them was, of course, nearly so small as the inner

ear itself.
(3)

The most serious objection arose in connection with thewidth of the strip of the basilar membrane fiiat must be excited.

Most critics noted that the transverse fibers, connected as they
were with each other, could not vibrate independently. Helmholtz
himself, recognizing that theii- tuning would not be sharp, cal-culated the degree to which adjacent fibers would be forced torespond. Implicitly this objection was met by the assumption that
pitch would be determined by the point of maximal stimulation—a premise elevated by Gray ( 1900) into a formal principle.
(4) Others argued that the resonance of the basilar membrane

would consist in a pattern of activation, as is shown by the sandon one of Chladni’s bowed melal plates. Although Ewald's (1899)

and Lehmann’s (1910) camerae acusHcae seemed to show this result, there was, as

wc shall see, other evidence favoring a simple

serial arrangement of resonances in the ear itself.

(5) Finally there was the quite natural premise of parsimony;fivethousand or ten thousand specific nerve energies were too

many when the eye was getting along with three and the skin was
soon to settle down to four. Of course, this analogy was not quite
fair, forthe eye and skin, having to mediate spatial as well as

qualitative patterns, thus have their myriads of ‘local signs.’ Nevertheless there were efforts, as we shall see, to reduce the necessary

number of specificities, like Mach’s reduction (1886) of them totwo.

In 1870, when Helmholtz had got his theory adjusted to the newdata about the basilar membrane, there were four important tonal

AUDITORY THEORY

408

phenomena of which a theory ought to take account, (a) First,
there was Ohm’s law. Helmholtz’s Rieoiy was built to take accountof it. Because it was basic to an understanding of all complex

sounds and because it had only recently been recognized, it wasat that time the most important fact about tone, (b)Then there

was intensity, which nobody thought about, because everyone took
it forgranted that the nerve fibers could respond with different

degrees of activation. After the discovery of the all-or-none law(

1912 ) this phenomenon became a problem. ( c ) There were beats.

Helmholtz explained beats by an appeal to the width of the stripof the basilar membrane which responds to a tone, The strips over-lap when the tones are close together, and the beats arise in the——^became thecommon portion. Thus one of the objections to ihe theory^thelack of sharpness of tuning in the basilar membranemeans for explaining beats, (d) And finally there wore the combination tones. Helmholtz, who had shown that they can occur
outside the organism, suggested that the ossicles of the middle oar

may be their place of origin when they are subjective. That, dien,
was the Helmholtz theory in 1870.
For the next twenty years there was not so very much criticism
of the fheoty. Then objections, modifications and new evidence

began coming in. We may mention a few of the more important
events.

Mach, in his Analyse der Empfmdungen in 1886, made an effort
toward parsimony of specific nerve energies. Just as the circularseries of hues could arise from mixtaes of three specific compo-

nents, so, he suggested, might the open hnear series of tones comefrom two specific energies: D {dsmvpf, dull) and H {hell, bright).

=

Any tone would be given by pD -|- qH, where p-\-q
l. Unfortunately that analogy to colors breaks down in the case of mixtures.

On Madh’s ffieory c and c' should mix in the right proportions togive g. He had to complicate his theory by suggesting a third component, Z, that would account for the richness of timbre; and withsuch gratuitous fabrication the theory failed. K8hler in 1913, in thetemporary belief that there are tones of pure vocaMty an octave
apart wiffi mixed vooalities in between, applied Mach’s theory ofvooality within the octave—making it much more plausible but
still not avoiding thesame difficulty.

In 1900 A. A. Gray contributed the principle of maximal amplitudes as the solution of the difficulty raised by the lack of sharp

—

RESONANCE THEORIES

409

tuning in the basilar membrane. He made the comparison withtouch.

An extended cutaneous region can be localized with anenor less than the diameter of the region because the area is considered to be where its center is. Similarly pitch could depend physiologically on where the center of the basilar excitation lies, thatis to say, at the point of

maximal amplitude. A noise. Gray thought,

would be like a tactually perceived line, having approximate but
not exact punctual location. This principle was, to be sure, implicit
in Helmholtz, but Gray by using the tactual analogy made it moreplausible.

Gray also at this time was the first person to note that the tension

on the short basilar fibers might well be greater than the tension
on the long ones, thus increasing the range of tuning from three
and a half octaves (due to lengdi alone) to something more likethe total audible range. From the base to the tip, the cochlear tube
gets smaller, the basilar fibers longer,

and the spiral ligament

which occupies the space between the outer end of the fibers andthe wall of the tube and which presumably keeps the fibers under

tension—smaller.

The short fibers in die laige end of the tube

leave room for a huge ligament, but for the long fibers there is onlya small ligament. To this fact Roaf in 1922 added the considerationthat die long fibers at the fai- end of tile cochlea are woiglited by theinertia and friction of long columns of lymph in the cochlear canals, columns that have to move between the oval and round windows when the long fibers are activated; whereas the short fibers,

near the base of the coclilea, are weighted only by short columns.
Wilkinson, writing in 1924 a defense of the resonance theory inassociation

with Gray and without knowledge of Roafs paper,

made the same observation. Thus length, tension and weight couldallbe regarded as entering in to account for the tuning of thebasilar membrane through ten octaves of audibility. The surpris-

ing thing is that, with all the talk about the resonance theory, it

took thirty years for someone to think about the differences intension and twenty more for someone else to think about the differ-ence in weighting, two principles that should be obvious to anyone
as sophisticated about tuning as was Galileo’s pupil, Mersenne, in

1636. The next twenty years were to show that even this view wasmuch too simple.

,

In general, the theorists who believed in resonance stuck to thebasilar fibers as the resonators. An exception is Shambaugh. He, in410

AUDITORY THEORY

1907 and later, argued that the resonators must be the fibers of thetectorial membrane. The basilar membrane is too stiff, he said, its
fibers are too rigidly connected to one another, its tension is toomuch dependent upon blood pressure from the blood vessel underit, for it to act as a series of resonators. The tectorial membrane isreally, so his histological preparations

showed, attached at bothends, not at one only; floating in the endolymph, it would easily

respond to the impulses transmitted through the cochlear canal.
This theory never gained acceptance, perhaps because the tectorial

membrane does not show a graded series of resonators.
The theory of basilar resonance was supported by the construction of camerae acusticae. M’Kendrick built one which he described in 1900. It consisted of a little box with glass sides (cochlea), a horizontal partition extending from one end almost to theother (spiral plate), two windows, one above and one below thepartition at the end and coveted with membranes (oval and roundwindows), two membranes covering two openings in the horizontal shelf (basilar membrane) with watch springs of different nat-ural periods suspended from them.

A piston actuated the mem-brane corresponding to the oval window. At 12 c.p.s. the larger

watch spring vibrated; at 24 c.p.s., the smaller. With these two
frequencies compounded in the motion of the piston, both springs
vibrated. Thus Helmholtz’s principles were shown to hold for thissystem.

In 1910 Lehmann arranged to transmit different rates of vibration to a strip of rubber membrane, wide at one end and narrowat the other with transverse tension applied to it. When, in order toobserve the vibration, he put sand on the rubber, he found thatthe membrane was activated most strongly in the strip most distant from the base of activation when the vibrations were slower.

Although this result supported Helmholtz’s theory as to placeof resonance, Lehmann was also concerned to point out that thevibrating band was too wide to give the sharp tuning required in

the ear.

Other evidence came from the tonal gaps. Stumpf in 1883 examined the hearing of certain persona for whom there were gaps
in the tonal series. Certain frequencies gave no pitches. Bezold too

in 1897, desqjdbing such tonal gaps and the consequent tonal is-lands which he found in a number of persons with defective heating, noted ffiat a defect of this sort is evidence for the separate andPLACE THEORIES
serial localization of pitches infilter out a

411

the ear. An injury would hardly

band of frequencies unless it did so by destroying a partof a series of resonators.

Somewhat later there were several experiments in which animals
were exposed for a long time to certain intense frequencies, one frequency for each animd, and their organs of hearing afterward ex-

amined histologically. The firstexperiment of this sort by Witt-maack in 1907 was inconclusive, except that it showed theorgan of Corti to be affected

and the organs in the vestibule-966

not. Later Yoshii in 1909 foundthat theexposure-frequency•‘1096determined in general the partof the cochlea where destruc-—the lower tones

tion oocun'ed

toward the tip and the higher
toward the base, as the Helmholtz

theory requires.

Fic. 62. DcGENzaATiOM oir Organ or

Corti62. ) The experiment, however,also told against the theory;

since a single frequency caused

the virtual destniction of a

Doe to Long Exposorb to
Tone: Yosan (1909)(Fig.

Cross-sectionof8

half-turns(oanumbered) of the cochlea oi a guinea
pig, showing legion in which degeneration occurred after long exposure

toindicated by this mefeod to be

loud impure notes with fundamental frequencies of abont 192, 966,
1024 and 4006 c.p.3. The region of
injury is large, but the high tones ate
near the base of the cociuea and die

ever so much less exact than

low tones nearer the apex, as requiredlarge region of the organ ofCorti, localization of pitch wasit really is.

by Helmholtz’s theory.

When the electrophysiological methods came into use about
1930, the evidence for the resonance theory, though not conclusive, was plentiful. The case for the theory was put excellently andforcibly by Waetzmann in 1912, by Hartrldge in 1921-1922, andby Wilkinson and Gray in 1924. In a later section we shall see what
the new physical technique did for the problem.

Other Theories of Hearing
The constructive criticism of Helmholtz’s theory took the formof the creation of other theories. These were all theories of pitch,

AUDITORY THEORY

412

since it was taken for granted that intensity depends upon the de-gree of excitation of the single fiber. The theories differed in two
respects, (1)There was the question as to the physiological cor-

relate of pitch, whether it is (a) the place excited in the organ ofCorti, as Helmholtz’s theory had it, or (b ) the pattern of pressuresin the organ, or (c) the frequency of excitation (functioning inde-

pendently of the particular fiber conducting the particular fre-quency). (2) Then there was Ihe further question as to how&e frequencies are separated in accordance with Ohm’s law,whether (a) by resonance or (b) by some other mechanical or
acoustical principle in the inner ear. Let us consider the five principal kinds of theory that were evolved in respect of these principles.
1,

Pioce-resoiiance theories. These are the theories discussed in

the preceding section. In them the component frequencies are re-garded as separated out by resonance, each at its own place, anddie particular fiber stimulated determines the pilch heard. Thus
this type of theory is always one which employs the principle ofthe specific energy of nerves; that is the essence of a place Uicoiy—itmakes particularity of fiber the deteiminanl of quality.
2.

Pattern-resonance (pressure-pattern) theories. It

was theassumption underlying these theories that the basilar membrane
responds to stimulation with a pattern of activation,much asChladni’s sound-plates form a pattern in the sand strewn uponthem when they are bowed to give a particular tone. Though suchtheories are really resonance theories in that the properlies of the

responding membrane ate partial determinants of the pattern, they

do not lend themselves readily to an interpretation in terms of specific nerve energies. Inthem a pitch would depend upon a patternof spedfle energies, not on a single energy or a simple relation ol afew. It is true, of course, that the Young-Hehriholtz theory of vision

assumed a pattern of specific energies as the determinant of visualquality, but that analogy was not urged.

The first pressure-pattern theory was put forward briefly byWaller in 1891. He argued simply that the tympanic membrane

would respond to different simple and compound tones with dilferent patems, and that it was reasonable toassume that thesepatterns are similarly impressed upon the basilar membrane. Sucha view was reasonable only for those who believod the objections
to the Helmholtz theory to be insunnountable.

FREQUENCY THEORIES

413

Ewald in 1899 and 1903 developed the theory fully. He performed experiments upon a membrane in which standing waves
were setup by an acoustic stimulus. The resultant patterns he photographed by reflecting light from the membrane, thus avoiding

any alteration of the period of the membrane by putting sand upon
He found, in general, that the distance between bands of the pat-it.

tern increased when the wave-length of the exciting tone increased.

Since his camera ociislica did not exactly duplicate the ear, he had

no proof that his theory was right; yet the effect of his experiments

was to weaken the Helmholtz theory.
3.

Frequenaj-non-resmance (telephone and leather chair-seat)

theories. In 1886 Rutherford suggested that the ear works like atelephone, merely transmitting die simple and compound frequencies along the auditory nerve to the brain.

He had noticed that afairly high frequency can be put on a motor nerve. Ten electric

shocks per second may result in ten twitches of a frog’s nerve-muscle preparation, but forty shocks per second hold the muscle
contracted in tetanus yielding what can actually be heard as a low-

pitched tone. Rutherford reported that he could hear tones fromsuch nerve-muscle preparations all the way up to S52 o.p.s. but
only noises at higlier frequencies. The recency of the invention of
the telephone (1877) and his surprise at finding nerves capable ofconducting such rapid frequencies, both predisposed him to believe that the analysis ofOhm’s law must take place, not in theear, but in the brain.

Perhaps the best publicized theory of hearing, next to Helmholtz's, was

Max Meyer's, for no other theorist has equaled him in

persistence and enthusiasm. Because it denies resonance and de-pends ultimately on frequency as the essential condition of pitch,
his theory is really a frequency-non-resonance theory.

He form-

ulated it in 1896, extended its application greatly in 1898, andgave it his most explicit exposition in 1907. libbed the “leatberchair-seat theory,”itmemwhen pressed

denies the elasticity of the basilar

brane, likening it to a leather chair-seat, which,up, stays bulged up, and, when pressed down, stays bulged down.

Meyer argued that the stapes, in moving in at the oval window,
starts todepress the basilar membrane, and that tMs depression

travels along from the base of the cochlea toward the tip until the

inward movement of the stapes is completed. Then, as the stapes
begins to move outward, a contrary action begins at the cochlearFig. 63.

The figure

Compound Wave of Components in Ratio 6:7

represents one period of thecompound wave whose twocomponents ue in the ratio 6.7i te., if this period is .01 see., the two components would be 600 and 700 c.p.s. This is the wave tor which Max
Meyer’s diagram in Fig. 84 is drawn.

Thus Meyer was contributing a new theory of loudness as well asof pitch. Pitch depends in his theory upon the frequency of excitation of any part of the basilar membrane, and loudness upon theamount of the membrane affected.

Meyer did not, like Rutherford, leave the analysis of complex
waves to some mystical property of the brain. He had a mechanicalexplanation which is diagrammed in Figs. 63 and 04. Let us takethe case of the simultaneous presentation of 600 and 700 c.p.s.,which in musical terms is approximately a minor third. Fig. 63
shows the compound wave for %oo ssc. Fig. 64 shows what, on
Meyer’s theoiy, happens to the basilar membrane in that %oo sec.

The instants A, B, C,

.

,

,

conespond in the two figures, We sup-pose that the basilar membrane is up at A as the stapes starts in.

At B the stapes has completed its maximal excursion, and the membrane is depressed through sections I to VII of its length. Next
the stapes starts to move out, and the membrane is pulled up until atC the stapes is about to reverse its direction of motion. Since

the stapes does not move out as far as it moves in ( Fig. 63 ) , section

Vn is left depressed. The remainder of Fig. 64

isderived from

Fig, 63: the stapes moves less and less in each direction until it

MAX MEYEB’S THEORY

Fig. 64.

415

Max Meter's Theory of Hearinq (1896-1907)

The figure shows the supposed positien of the basilar membrane In 14
successive instants in the complete (^de, when the compound wave in theratio 6:7 (Fig. 63) is perceived and analyzed by Ae eai. A, B, C, D,
N, A are successive instants and correspond to the points with Ihe same
letters in Fig. 63. 1, II,HI,

are successive sections of die cochlea

numbered away from the base. When the basilar membrane is up, it iscross-hatchedi when it is down, it is solid black. The numbers of di^Iacements (up, down, and up again) in a complete cycle are totaled at the bottom. Section I had 7 such displacements in a cycle; section H, 6; section
VII, only 1; section VIII and beyond, none. Thus these three sections furnish the frequencies for the two generating tones and for the first dlfieience
tone. See text for further explanation.

416

AUDITORY THEORY

reaches its minimal excursion at H. Then the system of motion isreversed until after

N the original state in A is again achieved.

Counting the number of up-down movements of the membraneshows that section I has had 7 in ^ooor 700 c.p.s., which isthe frequency of one of the component tones. Section II has had

6 up-down movements in Vioo sec. or 600 c.p.s., which, althoughdiey are not unifoimly timed (there is a long penod from G to I)
might give the other component tone. Section VII, reversing 100
times a second, might give the difimence tone; and indeed it was
the consideration of combination tones that first led
this theoiy. It is, to be sure, not clear

Meyer towhy the frequencies of sec-

tions III to VI might not be heard, but in the days of theorizing

about the ear. aU theories had shortcomings and tu quoque wasan acceptable defense.
In 1900 ter Kuile put out a theory of hearing quite similar to
Meyer’s; it assumed that the frequencies which determine pitch
are the result of successive positive and negative bulges travelingup the cochlea from the base. For simple harmonic motion sucha theoiy is adequate, but for compound waves it becomes involved.
Ter Kuile, who worked without knowledge of Moyei’s theory,
later acknowledged the similarity between fiieh basic principles,

In general, frequency theories have been favoied by the dis-covery that dichotio time and phase may determine auditory localization. In 1926 the author of this book argued that a frequency

theory of pitch provides physiological explanations for loudness,
tonal volume and dichotic localization. It seems, however, that hedid not go fat enough; he should have kept to resonance too, Un-

doubtedly he was blinded by the commonly accepted opposition

between the principles of resonance and of frequency, whereas
these two principles are not opposed and may be combined, as

already they had been by Wundt and Ebbinghaus {viide infra).
4. PlacB-nm'resonance theories. There arc at least two theories

which, rejecting resonance, yet managed to find a way whereby
frequencies might be localized in the cochlea and pitch regarded
as dependent upon specificity of excited fiber. The dassical theoryof this sort was Hurst’s in 189S, Because as few as two complete

waves may give rise to a determinate pitch, he held the resonancetheory to be impossible, as well as “aU new resonance theories ofhearing that may ever be propounded in the future.” His theory

OTHER THEORIES

417

assumed that the sound wave passes up the vestibular canal andback down the tympanic canal to the round window, the ascending and descending waves interacting through the elastic basilar

membrane to set up standing waves, the most prominent of which
would fix the place diat determines the pitch. This physical relation has never been established, and it is unnecessary to go into

the complicated physical analysis on which it was based.

The other theory of this type was Watt’s, formulated in 1914.
Like ter Kuile’s in its description of the mechanics of excitation of
the eai', it insists, however, that it is the place reachedh'aveling bulge

by thewhich determines the pitii, not the frequency

with which it is excited. Watt decided that pitch is really spatial, alocalization in the cochlea, and diat tonal volume is the spread ofthe excitation from the point of localization. Pitch is, neverdieless,not “cognized as spatial” although volume is— or so Wattthought. Tb's analogy of pitch to tactual localization comes up

every now and then; we have already seen how Waller made it inhis pressure-pattern theory.
S.

Frequency-resonance theories, There is no reason why a reso-

nance theory should not also be a frequency theory; that is to say,frequency, rather than specificity of fiber, may determine pitch,and yet the frequencies may ordinarily be sorted out onto different nerve fibers by resonance. The first theory of this sort wasHensen’s, contemporaneous with Helmholtz’s in 1863. Although hewas convinced of resonance because the hairs in the hearing-sacsof Crustacea respond selectively to different frequencies, he was

not prepared to accept the theory of spedfio nerve energies forthe pitdies.

Much later Wundt adopted this combination of principles. He
accepted nearly all of Helmholtz’s theory as it pertains to the actionin the cochlea but rejected Helmholtz’s belief that difference tones
arise in the middle ear. Subjects can,he found, hear difference

tones for two tuning forks held against the skull, and such “subjective difference tones” must be due, he believed, to the beat fce-quency in the auditory fibers themselves. This theory, which appears first in the 1893 edition of Wundt’s Physiobgische Psychologic, he amplified in 1902 and again in 1910.

Meanwhile, in order to explain difference tones, Ebbinghaus in1902 had adopted a similar theory. It was his idea that a given

AUDITORY THEORY

418

frequency activates not only its proper fiber, but also all the fibers
for its“^rmonic undertones," e.g, 600 c.p.s. activate the 600-

fiber, also the 300-fiber vibrating at 600 c.p.s, in two segments, the200-fiber vibrating at 600 c.p.s. in three segments, etc. Ebbinghaus

wanted to know how 600 and 500 c.p.s. can give a difference toneof 100 o.p.s. Presumably the fibers for 600 and 500 c.p.s. would lie
too far apart on the basilar membrane to interact. Their fifth har-monic undertones, however, would be nearer. If the 120-fiber isvibrating in five segments at 600 c.p.s. and the 100-fiber in five seg-ments at 500 c.p.s., then there might be a common region of overlap where the beat-tone of 100 c.p.s. would show up. Such a theoryispossible only if pitch is dependent upon frequency and inde-

pendent of the specific fiber which, for the moment, vibrates withthat frequency. If pitch is frequency, then fast beats might be apitch.

Recently Troland ( 1929) adopted a frequency-resonance theory

more consistent with good physics. By assuming that resonance inthe basilar membrane analyzes a compound wave into activatedregions corresponding to its component frequencies, and assuming
too that the frequences are preserved in die nerve, he was in aposition to account for the role of diohotio time and phase in auditory localization, as well as for otiier related phenomena. In a way

he anticipated the fact of the Wever-Bray effect to which we turnin the next section.
8.

Duplicity theory.

We have already seen (pp. 363 f.) how

Jaensch in 1913 formulated a duplicity theory of hearing, the notion that the cochlea functions for tone and the vestibule for noise.

We have now noticed, and reviewed as space permitted, twentyone theories of hearing. The sedentifle progress made is disappointing, Helmholtz’s original contribution, was, to be sure, a great ad-vance, his clear thinking and sound physics worthy of admii-ationj

but not nearly so favorable a verdict can be given of his critics.
Sincere and industrious, they nonetheless dealt naively with a complicated problem of physical dynamics,

and there can be little

doubt that they were partially blinded to the deficiencies of their
theories by their own ingenuities. In that respect they were being
littlemore dipn consistent with the period in which they wrote,

the paiod when theories were validated almost as much by the
personalities of their authors as by their supporting facts. So im-

PHYSIOLOGY OF HEARING

419

portant, indeed, were theories before 1020 that even an inadequate

one seemed better than none at all. With the new techniques theatmosphere has completely changed.

The New Physiology of Hearing
Since 1930 there has been a new and effective period of researchin psychophysiological acoustics. Primarily the electrical tech-niques for the control of the stimulus and for the amphfloation ofphysiological potentials have been responsible. It is also true thatmany of the contributions of the present have been made by men
better trained in physics for their day than were the older theoristsof hearing for theirs. The spirit and atmosphere of Helmholtz havebeen revived in a period when knowledge, techniques and thenumber of persons engaged in research are all greatly increased.

New facts about the physiology of the nervous system have also
influenced tlie theory of hearing in this period, just as the newhistological observations of the structure of the inner ear had de-termined Helmholtz’s thought.

We have already seen (pp. 80f.,

66 f.) how Bowditch in 1871 discovered the all-or-none principle
for muscle, how Lucas in 1905 and 1909 established and named thelaw and indicated that it might apply to nerve, how Adrian in 1912
proved that die principle is a property of motor nerve, how Forbes

and Gregg in 1915 argued that ie law ought to apply to sensory
nerve and, in consequence, invented the frequency theory to explain how sensory intensity can be perceived, how Adrian in 1926

and immediately thereafter proved that Forbes and Gregg wereri^t, and how part of the vacation of the validity of the all-or-

none law and the frequency theory for sensory nerve consisted in
the research on theories of hearing, research that began with theexperiment of Wever and Bray in 1930. It is to these investigationsof hearing that we now turn. They depended upon the new dis-coveries about sensory conduction and also upon the new electrical

techniques that had made those discoveries possible.

Although it is not practicable in this text to describe most of thescientific progress acliieved in the physiology of hearing since 1930,

we may, nevertheless, comprehend its nature. In general, we shallfind that there were four principal topics in respect ef which theserecent researches have yielded positive advances. Let us see what

happenedAUDITORY THEORY

420
1.

The Cochlear Response. When a sound acts upon the auditoiyniechanism in the normal manner, there are two effects, (a) A
neural impulse is set up in the auditory nerve, and its passage along
the nerve, consisting in the release of the nerve’s own energy, creates ‘action potentials,’ electrical voltage-differences that are meas-

urable by an ‘action current’ through a galvanometer. ( b ) The energy of the sound is also transfomed at the cochlea into other
differences of potential which can also be measured; it is these potentials, not transmitted along the nerve nor apparently dependent

upon the release of nervous energy, which have been called cochlear mietophonics (since the cochlea acts like a microphone intransducing mechanical energy into electi-ical) and which constitute the cochlear response.

We are concerned for the momentwith tho way in which these two phenomena came to be differentiated.

In 1910 Buijtendijk measured with the siring galvanometer what

he supposed were the action potentials of the auditory nerve. Withan elootiode upon the nerve he noted a considerable deflection of
the galvanometer for a percussion shot, and even for the ticking
of a dock and the sounding of a flute. The abrupt sounds weresynchronized with their stimuli, and tlie latent time was very short—of the order of .005 sec.
Much later the question of whether tlie frequency theory ofhearing could be settled by physiological experiment led Forbes,
Miller and O’Connor in 1927 to see whether rapid successions ofsounds could be detected by a string galvanometer and thermionicamplifier, measuring action potentials in the auditory tract in the

medulla. Their best results were obtained with a rapid scries ofclicks from a watchman’s rattle. Here they could get synchronism

between the stimulus and the action potentials up to rates of 200
per second, althou^ the best records were obtained foi' frequencies
less than 100.

There was nothing in these results to make themfavor a frequency theory of hearing, as there would have been

had they obtained synchronism at very high frequencies (wellabove 1000, say), a result which would have indicated to themthat the refractory period of auditory nerve fibers is much less thanfor other fibers investigated

and that high auditory frequencies
can thus pass-through the auditory nerve.

Then in 1930 came the dramatic experiment of Wever and Bray.
The amplified potentials from an electrode placed on the auditory

COCHLEAR RESPONSE

421

nerve of a cat they conducted to a telephone receiver in a soundproof room. Thereupon they discovered that tonal frequencies

from 100 to 5000 c.p.s. and human speech were reproduced in die
receiver when they were presented to the oat’s ear in the otherroom. That was a result to appeal to die imagination, for it seemedat the time as if one man could talk to anothM over die cat’s audi-

tory nerve. Wever and Bray, however, were conservative and cautious. By shielding the wires and avoiding tonal stimuli that weremade of steel or iron (like tuning forks), they ruled out the possibility of microphonic action in the receiving apparatus. They
proved that the phenomenon is biological by showing that it ceases
shortly after death, is reduced when blood supply to the head is
reduced, and is reslorcd when blood supply is restored. Although
they considered the possibility of microphonic action in die cochlea
itself, they decided (incorreedy)

against it.

Perhaps die most suiprising thing about this discovery was theexistence, as it seemed, of frequencies of several thousand cycles

per second in the auditory nerve. There was no other evidence thatthe refracloiy period of any nerve is less than .001 sec. To explain
their result, however, Wevor and Bray presented what they called

the “volley theory.’’ Tliey supposed, as had Troland before thorn in
1929, that different fibers would get out of step with each other,so diat one set would fire a volley of impulses at the critical pointin one wave of a tone, another set at the corresponding criticalpoint in the next wave while the first sot remained refractory, andso on. See Fig. 65. There, for intensity A, fibers a, b, c and d are

discharged at every tiiird wave of die stimulus, remaining refractory for the two intervening waves; but, since the fibers are outof step, the successive volleys come at the rate of the stimulus

which, for this intensity, is three times the rate of the nerve. At
intensity B, which is greater than A, the fibers would discharge

earher in the relative refractory period and thus oftener, perhaps
at every otherwave. Tlie result is the same frequency with agreater summated total excitation. In this way, Wevor and Bray,

by appealing to both the multiple fiber and the frequency theories
of intensity, as laid down by Adrian and Forbes, were able to explain not only how a nerve can conduct a frequency greater thanthe maximal rate of any single fiber, but also how an^electrical detector

can again integrate these scattered frequencies into die

original frequency-amplitude pattern of the stimulus. The theory

AUDITORY THEORY

422

was right, even though not all of the Wever-Bray effect was action
potentials of the auditory nerve.

Immediately there arose a controversy about the nature andorigin of the Wever-Bray effect. It was biological. Was it neural?

tr^v/\/\/\y\/\/\/v i<

Fia

65.

Volley Theory of Atottory Nbrve-Conductioni Wevbi andBray (1930)

Nerve*fibers a, b,c,d aro discharged at frequencies less than the fre-quency of the sound wave, but in ^nchiornam widi the wave. At intensity
A, die fibers discharge at every third wave, one-third of them at each wave.
At die grealer intensity B, half of tliem respond at every other wave. A

S

numba: of fib«s gives the total rwponse indicated oy tlie black hila series which reproduces both the frequency and intensity of theori^al sound. When the intensity is increased from A to B, the hillocks ate
hi^er, since the total number
nerve impulses is greater, but the synchronism with the sound wave is unaltered. From Wever, in Boring, Laogfe!d and Weld, Introduction to Bsychohgy, 1939, 596.
,i

Or might it be mioropbonic in the cochlea? Adrian early in 1931
argued that it was microphonic because he found that it persisted

when the nerve was damaged or narcotized, but later in association with Bronk and Phillips he dianged his view, largely because

he found the effect abolished by cocaine—aresult seeming to im-ply a neural origin. The first dear differentiation between the two

phenomena was made by Hallowell Davis and his associates in1981 and immediately diereafter. They used as an electrode a finewire passed through a hypodermic needle and insulated
from it (a “coaxial electrode”), in such a way that the needle-

silverAUDITORY ACTION POTENTIALS
casing, which was428connected with tlie ground, formed a shieldfrom the inductive effects of neighboring potentials. Enabled in

way to get action potentials from the nerve with the codilear

thismicrophonics eliminate, they found that the total potentials were
not so accurately duplicative of the stimulus as they were in the

Wever-Bray effect.
Further research in a very active period of investigation established many of the properties of the cochlear response, as this mi-

crophonic action came to be called. The response also provided ageneral method of investigation, for it taps the chain of causal
events at the cochlea and before the nerve. If one puts a pure tone
into the external ear and gets harmonics in the cochlear response,

then one knows that he has aural harmonics. If high tones give astronger cochlear response at the base of the cochlea than at thethen one makes an inference about the localization of pitches

tip,in the cochlea. The Wever-Bray effect opened up this new tech-nique, and Davis’s isolation of the cochlear response within theeffect was a very important additional discovery.
2.

Action potentials in the audilonj nerve. The new techniquewith the sliielded electrode made it possible to measure the action
potentials in the auditory nerve with the cochlear response eliminated. To pick up action potentials in the auditoiy tracts in thebrain also became possible. The main discoveiy was that the potentials of the auditoiy nerve reproduce the stimulus, including intelligible speech sounds, with considerable accuracy, that its fibers

are nevertheless limited to 1000 discharges per second as a maxi-

mal frequency, and that accurary of reproduction is diminished in
the tract in the medulla. These findings are due mostly to the workof Davis and his associates in 1931 end thereafter.

—because

The most important question about the auditory nerveits

answer bears on the problem of frequency tlieories and place—concerns the means wherebyittransmits frequencies

greater than the refractory period permits.

We have just seen thattheories

Wever and Bray, making specific in their volley theory an earlier
suggestion of Forbes and Gregg and of Troland, explained thisphenomenon as occurring by the successive discharge of “Volleys”(Wever and Bray) by different “platoons" (Forbes and Gregg) offibers.

Derbyshire and Davis proved that this relation holds forfrequencies

up to about 8000 c.p.s. As the intensity of a tonal

stimulus is increased, the magnitude of the action potential in theAUDITORY THEORY

424—presumably

nerve also increases until it reaches a maximum

at apoint where all the available fibers aie being excited. Derbyshire

and Davis, having determined the size of this maximal response forvarious frequencies, found the function that is plotted in Fig, 66,

Here the maximal response is constant for low frequencies since
every available fiber is presumably discharged for every cycle ofthe tone, Tlien at about 850 ap.s. there is a sudden drop in the re-sponse, indicating that the refractory period for auditory fibers

Fig. 06,

Acton Fotenhals in the AnDiroax NEava; Dibdyshibe (1935)

The nuudmal actian potential from the auditory nerve of the oat at different ftequenciei.. The sudden drop near 860 o.p.s. implies diat the refractory period of the fibers has been reached, and mat thqi are dischargine in
two platoons at every otlier wave of the stimulus The second chop at about
1700 o.p.s. indicates that tlie refraotoiy period permits discharge at only
every third wave. From Stevens and Davis, 1. acoust, Soe, Amer., 8, 1936,

9 (based on additional unpublished data of Derbyshire's).

has been reached and that the fibers are beginning to be discharged
in the volleys of two alternating platoons. Near a frequency of

2 X SSO= 1700c.p.s. there is another drop where the fibers would

presumably be divided into three platoons. Above 3000 c,p,s., however, the evidence of platoon organization is lost,

and the fibers

presumably fire ‘at will.’3.

Locdiei^on of pitch in the cocUea. Tlie place theoiy of pitch

raises the question as to whether it can be shown by physiological

techniques diat particular frequencies require particular parts of

COCHLEAR LOCALIZATION OF PITCH

425

the cochlea for their perception, and especially whether the baseof the cochlea can be shown to function for high tones and the apex
for low.

Direct evidence requires the observation of a correlation be-

tween tonal frequencies and places in the cochlea. Frequencies
have been measured (a) by noting the frequency of a prolonged
stimulus that is expected to damage the inner ear, (b ) by determining the frequency at which the cochlear responses are markedly

diminished or abolished, and ( c ) by finding the frequency at whichhearing loss is greatest in an audiogram, using the method of theconditioned reflex when the subject is an animal. Place has been
fixed (i) by post-mortem histologioal examination of the organ ofCorti for a region of injury and (ii) by observing the place on theoutside of the cochlea where the cochlear response is maximal. At
least four of these correlations furnished the subject of investiga-

tion in 1934-1935.

The method of Wittmaack and Yoshii was revived. After an animal had been subjected to strong stimulation, the region of cochlear injury

was determined by histological examination of thecochlea. Guild in 1919 found that animals exposed to loud detona-

tions—he was concerned with 'war deafness’—showed widespread
destruction of tlie organ of Corti in the second to the fourth halfturns of the cochlea, Davis and four of his associates in 1935 foundonly slight histological damage to the hair cells of guinea pigs

subjected to 75 days of stimulation by 600 and 800 c,p.s. at 60-96
db, but great damage from 45 days of 2500 c.p.s, at about 100 db.

In no case was the damage narrowly localized; indeed, witli 2500
c.p.s.

the maximal lowering of sensitivity, as determined by thecochlear response, occurred at 1200 c.p.s. instead of 2500. Kemp
at this timereviewed the entire literature of ‘stimulation deaf-

ness,’ showing that the effects are widespread and tend to be maxi-

mal for aH frequencies ( except perhaps the very high tones ) aroundthe second whorl of the cochlea. This negative conclusion is, afterall,

not inconsistent with Yoshii’s finding (Fig. 62. p, 411).

In 1934 Crowe, Guild and Polvogt published a report on casesof deafness to high pitches, cases for which they had both an antemortem audiogram showing the subject’s sensitivity and a post-

mortem examination of the cochlea, They found thtf degeneration
for the high frequencies always in the basal turn of the cochlea,

were able to localize approximately 8192, 4096 and 2048 c.p.s. andAUDITORY THEORY
to say that 1024 c.p.s. must lie beyond the first turn. See Fig. 67.

Culler attacked the problem directly, exploring the outside of

the cochlea to find the point at which the cochlear response ismaximal for each of twenty-three difierent frequencies. His results

showed remarkable consistency, See Fig. 68.
Stevens, Davis and Lurie, in a further pursuit of the problem, in-

67. iooALBSinoN of HighPlTCBSS IN THE BaSAL WhORL OF

Fio.

TBE Cochlea! Crowe, Guild and
POLVOGT (1934)

The spiral shows the 2)4 turnsof the human cochlea. The block
structures at the right rroresent
nerve tissue and hair celh of oFio, 6S. Looauzation op Pitches

m THE Cochlea! Culler (1935)
The

optimalpositionstheincochlea of the guinea-pig for thedetection of weak codtlear re-sponses at the frequencies shown.

From

Culler,Ann. Otol. Rhinol,

Laryngoi., 44, 1935, 813,

normal cochlea! the white areas in
the first half-turn show degeneration in a pathological case of hfgh-tone deafness.

The localization of three high frequencies, as determined from an
From Crowe, Guild and Polvogt, Bull,

analyais of 70 cases. Is also shown.
fofitis ffojjkins

Hosp.. 54, 1934, 372.

jured the cochlea by drilling through its wall with a small drill,

and then by use of the cochlear response determined the frequencies for which sensitivity was most reduced. Their results areshown in Fig. 69, in which the location of the center of a rectangle shows the relation of the beginning of a region of destruction
to the beginning of a region of loss of sensitivity, or else die relation of the end of a region of destruction to the end of a region
loss of sensitivity. The heights and widths of the rectangles

of

indi-

cate the range of uncertainty with which these points are located,

COCHLEAR LOCALIZATION OF PITCH

427

for the changes are not abrupt. It was possible in this way to scale
off the basilar membrane for frequencies. See also Fig. 70.

By the end of the 1930’s there had come to be pretty generalagreement on at least these points; that the high tones require forFig. 69.

Localization of Pitches in the Cochlea; Stevens,
Davis and Ldhie (1935)

Locslizalion of fiequeodos in four turns of the guinea-pig’s cochlea. The
horizontal position of eacli rectangle represents the beginning or end of aregion of desirucUon of the organ of Corti caused by boring through thecochlea with a drill and detennined afterward by histological examination.
The vertical position of each rectangle represents the beginning or end of aregion of loss of sensitivity. The widi^ and heights of the rectangles represent
the range of uncertainty of localization, since neither change is abrupt. The
is the distribution of frequencies determined by integrating
J.n.d.
from Knudsen’s data, and tlie fact Aat the rectangles tend to lie on the solid

solid line

line seems tomean that j.n.d. occv^ equal spaces along the basilar mem-brane. From Slevens, Davisand Lurie, !. geneial Psychol., 13, 1935, 312,

their perception the functioning of the basal part of the cochlea,that excitation spreads pretty far for all fiequencies and further for

greater intensities, and that the spread is so great for die low tones
diat theii- localization at the tip of the cochlea is at best only a grossapproximation.

,

Besides all these methods there have been two others. Wegel and

Lane, in their early paper in 1924, arranged the frequencies along

DISTANCE FROM OVAL
WINDOW: MM,
Fig. 71.

LocM,nATioN o* Ptickes

m the Cocble,,. W*gel and Lane

(1»24;

the dfiffres tnoise,

membrane for frequencies by notingI

amving at the locabzationsof Fig. 72, for masking
is a

DYNAMICS OF THE COCHLEA

429

phenomenon tliat implies overlap ot frequencies on the basilar

membrane (pp. 365-367).
All in all it is astonishing how well these many methods agree( Figs.

67-72 ) As Davis showed in 1940, it is hard to plot the differ.

ent investigators’ results on the same coordinates because the vari-

ous curves so nearly ooineide.
4.

Dynamics oj the cochlea. Much more sophisticated physics

has been applied to the problem of cochlear dynamics than was
represented in the old resonance and pressm'e-pattem theories.
2000

Fro. 72.

Locauzation or Pitchcs in Tni CocncEA: Fletcheb (1938)

Chart based on the metlrod of masknig tones by a thennal noise. From
Fletcher, Froc. net. Acad. Sot., 24, 1938, 273.

The first attempt of this sort was made in 1924 by Wegel and Lane,

who set up an electrical model of the cochlea, a series of tuned
resonating circuits connected in parallel to represent the series of resonators in the Helmholtzian conception of the ear.

Be-

cause the circuits were separate, however, this model was wrong.

The subsequent demonstration of the localization of pitches in thecochlea served to show that the spread of excitation is great, muchgreater than the simple overlap required by beats. Hence later investigators came to see the problem as one of the total hydrody-

namics of the cochlea, of a tube with elastic waDs, and not as aseries of nearly independent resonators.

The most trenchant analysis of this sort was made by B4k4sy(

1928-1933 ) , who showed that the movement of the stapes in sucha system—he had a model and observed the vibration of its mem-

AUDITORY THEORY

430

brane by a stroboscope—would establish a wave with a maximal
bulge in the basilar membrane near the middle of die cochlea, andthat this wave would then travel on to the tip of the cochlea. ( Fig.
73.) The speed of the wave would range from about 30 meters per

second at the base of the cochlea to about 10 at the tip; the displacements of the basilar membrane would not be in phase witheach oiher. There might be as much as 3 miUiseoonds required for
STAPES

fio! 73. Tkaveliino Wave in

HELICOTREMA--,

the Basilae Membhane; Birisv (1933)

As the stapes moves out, the column of lymph toward the base acts as apiston and first elevates the basilar membrane as in die solid line; thereafter
the wave travels on to the tip of the cochlea (helicotrema) as in die dottedline. From B4kdsy, as redrawn by Stevens and Davis, Heating, 1938, 279.
the passage of the wave to the tip of the cochlea, an interval that islong with respect to the refractory period of nerve fiber and verybng indeed with respect to the times that are effective in the localization of sound. Fletcher in 1930 made a similar analysis, andBeboul in 1938 developed the differential equations whicli show

how such a system would operate for sounds of different periods.
Stevens and Davis summarized and extended this analysis also in
1938.

The mathematical physics shows that there should be in thecochlea a widespread displacement of the basilar membrane, a dis-placement which travels from the base to the tip and changes form
as it goes. In the sense that the dynamic properties of the cochlea

determine the form of the displacement, such a view constitutes aresonance theory; but it is not a resonance theory in Helmholtz’s
sense of there being a series of nearly independent resonating ele-ments. The Helmholtzian properties of the ear—the fact that thelongest fibers under the least tension and the greatest weight areat the tip of the cochlea and that the shortest fibers with the greatest tension and the least weight are at the base— enter into thehydrodynamic system by making the displacement greatest at the
tip for low tones and greatest at the base for high.

Pul thus simply, ffie problem would seem to be far advanced;

NOTES431

yet it is hard to see how these long flat waves can determine pitch
discrimination, which amounts, as Stevens and Davis noted, to adifferentiation of a distance of about .02 mm. on the basilar mem-brane. Gray’s principle of maximal amplitude would hardly seem
valid for a wave without a peak, Bekesy first,

and Stevens andDavis later, have argued, however, that the essential basis for excitation of the hair-cells may lie, not in the amount of displace-ment, but in the gradient of the displacement, just as a visual
gradient of grays is marked off by contrasting rings at the point ofgreatest change or as a ring of pressure is felt at the maximal

gradient when a finger is held in a liquid. In some such way, they
think, the necessary spatial specificity required for the discrim-

ination of a thousand or more pitches might be achieved.

While it is clear that the problem of the physics of the inner ear
is

not yet solved, it is also dear that modern physical analysis hasbrought it much nearer to solution than did the more personal
speculations of the physiologists of the late nineteenth century.

Always, however, we must except Helmholtz from such strictures,for he made the greatest contribution in the history of this prob-lem, thinking dearly and impersonally, and combining the courageof speculation with an objective respect for fact.

Notes
1786, in which De audita is Vol. V,

Anatomy of the Ear
For

Galen’sknowledge

theof

1783, Bk. 15, pp. 186-305, a very
thorough discussion.
briefer ac-Astructure of the ear, see H. Werner,count of Haller’s

Die mlenische Otolagie, 1925, (dis-

Imae

Later

sert.).

anatomical

conlribu-

and summaries of pievbus
work were by B. Eustachio, De auditu Oigmis, 1562, and also his
Opuscuh anatomkae, 1563; G. Casserio (he was one of Harvey’s teach-

tiona

De

in

physiologloe,

1751; 3 ed.,ed.,

his Primae
1747; 2 ed.,Eng.
trans. of 3
1784;
is

1779.

resonance

His anticipation of thetheoryisand 405 of the 3ined.; I494
have notsects.

seen die eaiUer eds.

The incidental researches cited fororgenisdie middle ear are A. Cooper, Fur-C.

ther observations on the effects which

Nova intentoe aurls dilineato,
1654, [n.v.]; G. J. DuvemCT (a verytake place from the destruction ofers),

historia

vocis auditusqueamtomica, 1800,[n.v.];

Folio,

firorough account).

Trait/ deTor-

Bane de Touie, 1683; Eng. trans. of

1 ed., 1748.
After them came Albrecht vonHaller (1708-1777), whose important work was Elementa physiologlae corporis humani, 8 vol., 1757-

themembrana tympani of the ear[and from the ms of the ossicles],PM. Tram., 1801, 435-450; W. H.
Wollaston, On sounds inaudible bycertain ears [Includjpg those

wherethe air pressure in the middle ear
is too great or too litde], ibid.,1820,

306-314; F. Savaih Redierches sur

AUDITORY THEORY

432

du tymde roieille exlorns [sandmethod], Ann. CAim. fhys., 3 ser.,usages 4e la membrane

les

pan

Resonance Theoryet26, 1824, 5-39.

1803,[n.v.],

anatomy and kinematics
and the organ ofof the inner ear

Human

Corti,

known to every student of abut in the

goodintroductory

ear is in his Anatomy of theIII,text is not tire place to de-scribe the

Sir Charles Boll’s account of the

Body,

This

coursepsy-in

The reader is supposed toknow the positions and functional

346-272
the human anatomy and 272-

chology,

277 for hearing. On the function of
the round window, see p. 273.
For Johannes Muller on the car
and hearing, see his Ilandhuch derPhytiolagie des Menschen, II, 1838,
Bk. V, seel. 2, or later ed., or Eag.

relationstrans. Muller's discussion of specificbasilarnerve energies is in the introductory

forming the arch of Cord, and theinner and outer hair calls in which

1809
for

232-279,

ed.,

esp.

portion of Bh. v, hut in general on
this topic see pp.

69-72.

or the oval window, theround window, the vestibular canal,
the tympanic canal, the cochlear canal, Reissner’s membrane, the spiralplate, tire spiral ligament, the organof Corti, the tectorial membrane, thediemembrane, llie rods of Corti

of

the

If

he

does

there

are

innumerable

fibersFor M. J.

P. Floureiis' establish-

originate.

ment of thesemicircular canals as

them,auditorynotorgans of orientatian and thus notcounts which also discussortearlng, see pp. 014, 014.

the resonance theoiy;

The references on tlie mioroseopie
anatomyCorti,

ac-

critically

G. M’Ken-drick in E. A. Schilfer, Text-Book ofA.

Physiology, 1900, II, 1164-1194; B.

Beoherohes sur I’organedeWaetzmann,

the inner

ear

des

1851, 109-169, esp. 131-127 and,op,

for the dimensions of tlio organ of139

hearing,(heexamined

200

coehleas of beef, pigs, sheep, cats,rabbits, moles,

Reissner,mice and men); E,

De auris inlemac forma-

iione, Iffil,[n.v,];

V. Hensen, Stu-

dien fiber das Gehiirorgan der Deca-

poden,

know

are

of

route des mammif^es, Z. loiss. Zool.,
8,

J.

nerve

Z.

toiss.

Zool,

13,

1863,

819-412, esp. 397-399 for the resonance of hairs of crustaceans tofemes; Zur Morphobgle der Sohnecke

des Menschen und der Siiugelhlere,aid., 13, 1863, 480-512, esp. Fig.

S

20 for the dimensions and shapethe basilar membrane; G. Betzius,

Gehewgm der 'WkhetiUere,
1881-1884, esp. for man, II, 328357 and Plates 33-39 (two hugevolumes with many plates of figures

Dos

now classical); Sir Arthur Keiur in
T. Wrightson,

An Enifuky into the

Mechanism of the Internal Ear, 1913, 161-254 (a more
recent careful anatomical and kineAnalyticalmatic study of the inner ear).

Die

Remanztheorts

HBrens,
eft.,

ture,

1912; T. Wrightson,
35-59 for the simple struc-and loo.

cit.

for Keitli’s ana-

fejmical appendix; G.

A. A. Gray,

Wilkinson and

The Mechanim of the

Cochlea: a Restatement of the Resonance Theory of Hearing, 1924; S.
S. Stevens and H. Davis, Hearing,
1988, 249-287.

H.

Helmhollx’s

accountofliis

theory is in his Die Lehre oon den

2 ed.,
Tonempfindungen,
1863;
1865; 3 ed., 1870; 4 ed., 1877; theend of Chap. 6 in any ed. Of course,
one compares die 1870 ed. witheither of the two preceding to notethe oliange from the rods of Corti
to the basilar membrane. The actual
date of this change is fixed by Helmholtz's
Ueber die Sohallschwingungen in der Schneeke des Ohies,
Verhomll naturhlst, med. Verein
Heidelberg, 5, 1869, 33-38, [n.v.,
but reprinted in his Wissenscltaftliohe

Ahhandkmgen,II,582-^88].

Helmlroltz published no preliminary

papers on the mechanism of hearing

NOTES
beforebut

1863,

afterwards

workedmeohaniasof

was ho who

it

out

the

exact

tlie

ossicles;Ueba

die Meohanik der Gehorkuochelchen,ibid.,

in153-161,

1867,

4.

AWiandi.,

WIss.

but

fn.v.,

II,503-514]i
Gehoiknoohel-

Die Meohanik derohen und des Trominolfolles, Arch,

1869, Separatabdruck,ees, PhysloL,

433

regions have to be not to overlap.

Thus the perceptual “dumb-bell" or“double paddle," that lies between
perceiving one point and two points,
corresponds

to

case

tire

of

tonal

The two-Cf. E. G. Boring,beats.

point limen and the error of locali-Amer. /. Psychol, 42, 1930,
448-449. Also see pp. 484 f. Infra.
zation,515-

G. E. Shambaugh’s first argument for the fibers of the tectorial

Mach’s parsimony of specificenergies occurs in his Analyse dermembrane os resonators is bis A re-1886 or any later
edition, ihe chapter on Tonempfindungen (Chap. 13, sect 17 instructures in the cochlea with con-[n.v., but in Wiss. AblmndL, II,

581],

E.

P,mpfrndvngen,later ecUtions,
first

but the chaps, in ihe

were fewer and unnum-ed.

W. Kohler's analogous

bered). For

parsimony, see his Akustiache Untei'suchungen, Z. Psychol, 64, 1913,

96-105, esp. 103-105.
A. A. Gray showed how the changing size of the spiral ligament along
the cochlear tubechangeofmignl load to aon the basilar

On a modification of tireinfiberstensionHelmholtz theory of hearing, /. Anat.
Physiol,

34,

324-350.

1900,

The

notion that ihe long h.asilar fibers aremost heavily weighted by the inertia and friction of the columns oflymph in the cochlea was first apparent to H. E. Roaf, The analysis
of sound waves by the cochlea, Phil.
Mog., 43, 1922, 349-354, and thenindependently to G. Wilkinson in
Wilkinson and Gray. op. cit., 1924.

study

of

the

minuteanatomy ofclusions bearing on the solution ofproblem of tone perception,
Amer. I. Anat., 7, 1907, 245-257.
His later articles are Die Membrana
tectorla und die Theorie der Tonempfindung, Z. Ohrenhellk., 59,
1909, 159-168j Dns Verhhltnis zwisehen der Membrana teetoria unddenr Cortischen Organ, ibid,, 62,
1910, 235-240 (which has the best
theplatesof thenewpreparations of

the orgnn of Corli),

On models of tire inner ear andcamerae aoustiene, see M’Kendtick,op. ctt., 1900, 1182 f.j A, Lehmann,
Ueber die Schwingungen der Basilarmembran und £e Ilelmholtzsche
Resonanztheorie, FoUa rteuroMol,
4, 1910, 116-132; Wilkinson andGray, op. cit, 1924, 82-105.
On tonal gaps and islands, see C.

Stumpf,Tonpsychclogie,

L

1883,

me determination of pitch and lo-

411-419; F, Bezold, Demonstration
einer kontinuietlichen Tonreihe znm
Nachweis von GehSrdefekten, inbesondere bei Taubstummen, und die
Bedeutung ihres Naohweises fiir
Hehnholtzsche Theorie, Z. Psychol,calization of touch

13, 1897, 161-174, esp.

57-59.
Gray’s principle of maximum am-

and his analogy between

plitudesisin his op,

ctt.

Had Gray known that the(1900).

The

investigations of

172 f.
the effects

tactual error of localization is smaller

upon the organ of Cortl of bng ex-

than

tlie

two-point limen for thisposure to tones are K. Wittmaack,very

same reason, be could haveUeber Schiidigung des Gebors dutchpressed his analogy further. The error of localization

measures the ac-

curacy with which the center of the

Schalleinwirkmg,

Z.

OhrenheiVc.,

37-80; Zur Frage derSchiidigung des Gehorsorgan dutch

64,

1907,

stimulated region is placed, but the

Schalleinwirkung,two-point

211-220; U. Toshii, Experimentelle
Untersuchungen uber me Schiidl*

large)

limen ( three times asshows how far away two

iBid.,

59,

1909,

AUDITORY THEORY

434

Missouri Studies,giing des Gchfiisorgai] dnrch Scliall-

inner

201251. The final verdict has not. how-

Sd Ser,, 2, no. 1. 1907; E. ter Kuile,

ever, supported Yoshii, for sthnula-der Grundmembian auf die Haarzel-

tiau detdoess spreads over too largelen.

a part of the cochlea to give the146-157; Die riohtige Bewegungsiorm der Membrane basilaris. Ibid.,
79. 1900, 484-509, esp. 499-509

elnwiiltung.

ibid.,

10OB,

58,

specificity of loss desired for the res-onance theory.

On

see

point,

this

H. Kemp, A oritioal review ofexperiments on the problem of stimnlation deafness, Fsychol Bull, 32,
1935, 325-343.
E.

For the general summaries, besides Waotzmann and Wilkinson andGray, opp. citt., see H. Hartridge,

A vindication of the resonance hypothesisofaudition,

Brit.

Psy-

J.

chol, 11, 1B21, 277-288; 12, 1921,

142-146;

12,

1922,

362-382;

13.

1922, 48-51, 185-194.

(7nio.

ear,

Die Uehertragung der Energio vonArch. ges. Physiol, 79, 1900,(theory);

Amer.

for

localization,

Psychol, 37,

J.

157-

1926,

188, esp. 176-183.

Phce-non-resonance theories; C.
H. Hurst, A new theory of hearing,Trans. Liverpool Biol Soc., 9, 1895,
321-353; H. J. Watt, Psyohologicnl
analysisJ.

and theory of hearing, Brit.
7, 1014, 1-43, esp. 27-

Psyclml,Frequency-resonancetheories;
Hensen, opp. citt. in first section ofthese notes:

referencesandvolumetensity,48.

Other Theories
The

G. Boring, AuditoryE.

theory udth special reference to in-thetmnanca theory are given

placethein

W. Wundt, Grundzilge

der physiologischen Psychohele, 4ed., I. 1803, 478-480; 5 ed., H,

preceding section. Below are the ci-

1002,

tations indicated in the text for the1910,

other theories.

Iiaus,

Paitem-resomnee(pressure-pattern) theories: A. D. Waller, Intro-

1902, 313-329; L. T. Troland, The
psychophysiology of auditory ijunllties and attributes, J. general Psycho!., 2, 1929, 28-58, esp. 36-47.

duction to Human Physiology, 1891,

458-462, esp. 461 f., or 2

1893.
464-469, or 8 ed., 1896, 470-475;
J. H. Ewald, Zur Physiologic desLabyrinths: eine neue Htirtlieorie,
Arch. gea. PhpsloZ., 76, 1899, 147-

131-133, 187 f,; 6 ed.. R,
136-138, 143 {.; H. EbbingGrundzilge der Psychologle,

Dtrplichy theory:

E. R. Jaensoh,

Die Natur der menschlichen Sprachlaute,Z.

219-290,Sinrwsphjslol.,

Cor eleven of these theories

Old., 93, 1903, 485-500.

holtz,

idem:

die

1913,

47,

256-260.
good secondary sourceesp.

A fairly

Erzeugung vonSchallfaildem in der camera acustica.
188;

hearing, I. Anat. Physiol, 21, 1886,(HelmLipw,
Hurst, Meyer, Ewald, ter Kuue,
Lehmann, Gitbel, Watt) is H. T.
Watt, The Psychology of Sound,
1017, 139-182 for the others, 162-

166-168; M. Meyer, Ueber I^hin-

175

for

since

1914.

Freoitenop-non-resononce(tele-

phone and leather chair-seat) theories:

W. Butherford, The sense of

atlonsttine

und

dnlge

hierzuin

Rutherford.

Gray,

Watt,

somewhatalteredBeziehuug stehende akustische Erschelnungen, Z. Psychol, 11, 1898,
177-229; thra there are five articles

in ibid., 16, 1897-1898, 1-84, 352372; 17. 1898, 1-14, 401-421; 18,
1898, 274-2935 but the mostplete and final exposition

is

oom-

An in-

troduction to the mechanics of the

Recent Physiology ofHearing
In general on the contents of thissection,

see

E.

G.

Wever,

physiology of hearing:The

the natureof response in the cochlea. Physiol

NOTES
Reo.,

1933, 400-425 (bibliog-

13,

11. Davis, The
phenomena of audition, Uandhook of General Experlmental Fsychology, 1934, 062-988

raphy of 33

titles);physiological39(bibliography of

titles);S.

S.

Stevens and H. Davis, Psychophysi-and loud-pitchacoustics:

ological

acomt. Sec. Amer., 8, 1936,
1-13; Stevens and Davis, Hearing,ness, 1.

1038,

208^38of thebook is 334 titles).
firstelectrical measurement

The

response

theofmechanismofauditorytlie(were they neural acor

potentials

tion

bibliography(totalmioro^tonies?)

is

F.

only
J.

cochlear
Buijten-

J.

dijk.

On the negative variation ofthenervus acusticus caused by a

Akad.

435
to remark, in the obscurity of

fair

these

that bothnotes,

the experi-

ment of Forbes, Miller and O’Connor, op. cit., 1927, and tliese original experiments of Wever and Bray
were stimulated by Boring’s paper,
op. dt., 1926.

£. D. Adrian’s first suggestion of
the cochlear microphonics

of aabstractin hisis

The micro-

paper.

anphonic action of the cochlea:
interpretation of

Wever and Bray’se:q)erimentB,

Fhysiol.,

J.

1981,

71,

xxviii f . His change of mind is mani-

Adrian, D. W. Bronk and G.

fest in

The nervous origin of the
Wever and Bray effect, ibid., 73,
Phillips,

1031, 2Pf.

The isolation of the cochlear re-

Amsterdam, Froc, Sect. Set,, 13, 1910, 049652. The study of synchronism ofclicks (watchman’s rallle) with potentials in the medulla is A. Forhes,

sponse from the auditory action po-

R. H. Miller and J. O’Connor, Eleo-

midbrain oftlie

Science,

74,

trio

responses to acoustic atlinuli in

1931, 205 f.

(brief mention);

Saul

tlie

decerebrate

end

Electricalsound,

Physioi., 80,

Wettensch.

Amer.

animal,}.

sponsetoin tlie

papers:Davis,

auditory tracts of thecat.

phenomena

auditory nerve in restimulation,

The electric response of the cochlea,

Action cur-acoustical

Froc. not. Acad. Soi., 18, 1930, 344-

350

followingthein

H. Davis and L. J. Saul, Action currents

Amer. otol Soc., 22, 1932, 137-145(brief but crucial); Davis. A. J.
Derbyshire, M. H. Lurie and Saul,

W. Bray arein therants

appearsof the auditory meclianism, Trons.

102T. 303-380.

The hiitial papers of E. G. Weverand C.

by Davis and his associates

tentials(preliminary);

The nature of

the acoustic response:

the relation

between sound trequenCT and frequency of Impulses in the auditory

Amer.

332

of theThe

Physiol, 107, 1034, 811-

7.

(full account of die properties

cochlear response);

electrical

Davis,

phenomena of thecochlea and the auditory nerve,

7.

373-387 (main experiment); Pres-215

Amer., 6, 1935, 205(good summary). In generalent possibilities of auditory theory,

see

S.

nerve,

7.

Psydiol

e»p.

Reo.,

Psychol,

37,

13,

1930,

1930,

305-380(volley theory). 'The volley theory

may be said to have been

antici-pated by Forbes and Gregg,
dt.,

1915 ("'platoon

fire”)

loc.

and byop. cit., 1929, 24 f. The
name volley theory emphasizes thesimultaneousdischarge of many

Troland,fibers,whereas the term platoon firettcoust.

Soc.

S.

and H, Davis,

Stevens

Hearing, 1038, 310-855.

On action potentials in the auditorynervefibers,see

Wever andBray, opp. dtt.; Davis et al, opp.
dtt.;

and esp. Saul and Dav&, Ac-tion currents in the central nervous

system: action ounents of the auditory tracts. Arch.

Chicago,28,

Neurol Psyohtat.
1104-1116

1932,

asserts the discharges or successive(^ves seven charajtmlstlcs of true

volleys by diSerent sets of fibers andaction currents); Davis, Forbes andwould seem, for that reason, to be
the more descriptive term. It seems

Derbyshire,

The recovery period ofauditory nerve anditssignificanceAUDITORY THEORY
lor the Uieoiy ol hearing, Science,

Davis,

tion

The action potentials of theear,Amer. J. PhijuoL,
113, 1935, 476-504; Stevens andacou^
Psyoliophysiological
Davis,
tics: pitch and loudness, 1. acoustauditory

nerve,

Soc. Amer., 8

Hearing,,

1938, 1-13, esp. 7-8;

1938, 376-438.

localization of pitch are as follows.

—

War deafness

B. Guild,^reporiof the labyrinths of the animals used
testinginpreventive measures,ofMed., 4, 1919, 153-180,
esp. 169-180 (detonation deafness);
G. Finch and E. A. Culler, Effects],

lab. oiin.

ofexposure

protracted

tone. Science, 80,

by conditinned

a loudto1934, 41 f. ( test
11.
Davis,

reflex);

Derbyshire, E, H. Kemp,
J.
M. IT. Lurie and M. Upton, Func-

A.

and

tionalhistologicalthe cochlea

the

of

changesinguinea-pig re-sulting from long stimulation, /. generalhyehol,

1935,

12,

251-278(cochlear response and histologicalexamination);S.

].

Crowe,S.

R.

Guild and L. M. Polvogt, Observations on the pathology of high-tone
deafness. Bull. Johns Hophna Hasp.,
54,

193A 315-379.

(histologicalesp,

examination);369-377
Culler,Symposium: tone localiiation in
the cochlea, Ann, Otol. Hhlno).
Loryngol, 44, 1935, 807-813 (direct Realization by cochlear reroonse); Stevens, Davis and Lurie,in

The localization of pitch perception
on the basilar membrane, J. general
Psychol., 13, 1935, 297-^15 (cochlear response and histological examination;

B. L.

also

Phys. Ron., 23, 1924, 266-285,
276-284 (counting j.n.d.); II.

Ffetoher, The mechanism of hearing

counting

j.n.d.);

Wegel and C, E. Lane, The

auditory masking of one pure toneon

as revealed through experiment

the masking effect of thermal noise,
Proe. nat. Acad. Scl., 24, 1938, 265-(masking

274

The papers cited on die cochlcai
S.

by another and its probable relato the dynamics of ihe innerandDerbyiJiire

622;

1933,

78,

method).

See

also

symposium of 13 papers by 21
authors on Tone localization in thethecocldoa, Ann. Ofoi. Rhlnol.

harm-

738-837; E. H.
Kemp, A critical review of experiments on the problem of stimulagal,

44,

tion

deafness,

1935,

Psychol.

Bull.,

32,

1935, 325-342; Stevens and Davis,
Hairing. 1938, 356-375; Davis, Thephases of tho
Laryngoscope, SO, 1940, 747-755.
On tho dynamics of the cocldea,
clarification of certain

physiology

see

of

hearing.

Wegel and Lane,

loc.

ctt.i

G.

von Bdkdsy, Zur Theorie des Hdrens:

Die Schwingungaform derBasilar-membran, Phys. Z„ 29, 1928, 793810; Idem: Ueber die ebenmerkbare
Ampliluden- nnd PrequenzKnderuog
eines Tones; die Theorie der Sdweb-

imgen,

ibid.,

30,

1929,

721-745;

Ueber den Knall und die Theoriedes HSrens, ibid., 34, 1933, 577582; H. Fletolrer, A space-time pattheory

ofSoo. Amer.,

1,

tern

hearing,I.

acoust.

1930, 311-343. esp.

316-325; J. A, Bohoul. ThSorie desphenomfines mecaniques se passantdans I’orcille interne, J. Phys. Radium Paris, 9, 1938, 185-194; Les

phdnomdnes

dlectriquesdeI’oreillointerne et leur rfile dans les theories

de I’auditlon, ibid., 9, 1938, 428436; Stevens and Davis, Hearing,4431938,276-287.
372-375,445.

chapter 12

SMELL AND TASTE

T

he experimental psychology of smell and taste has very
little ‘history.’

A thorou^going modern handbook, like von
4e facts gives also nearly all the

Skramlik’s, in giving all

history, for there has not been time and thought enough for manyfacts to go out of style or many theories to be proved wrong, The

history of these ‘chemical senses’ must lie largely in the future.

Why?
WTiy have the ‘chemical senses’ had no true scientific development? It is easy to say that not all fields can mature at once, thatsome must wait upon discovery in other fields and upon suchchance insights as procreate successful research, that smell andtaste are nowadays like sight and hearing in 1750, that there is alimited body of fact which interests a few men but no sure method
for going further. Such an account, however, is a description, notan explanation, of the present state of these two fields.

One explanation is that these senses are too simple for elaborate
description; lacking as drey do the complex organization of sightand hearing with their analytical receptor systems, there is, therefore, little to find out about them. That theory, however,cannotstand. Smell, at least, shows such a great complexity of qualities

that it has been likened to vision, and the olfactory membranecompares well in absolute sensitivity with the retina and the or-

gan of Coiti, even though its differential sensitivity is not so good,
There is still plenty to find out

Another theory is that smell and taste are so unimportant in hu-

man civilization as not to interest men. If human culture could
have been founded on a dog’s life, smell and not vision would be
the great chapter of sensory psychology, and Helmholtz would

have written ihi-ee huge volumes of a Handbuch des physiologischen Geruchs, as well as a Die Lehi-e von den Gesohmacksemp-

findungen als physiologische Grundlage fur die Theorie der Geschmackslehre. To a certain extent this theory must be correct;
437

SMELL AND TASTE

438

there can be no doubt that human interest excites intellectual activity, which in turn, by its very amount, begets the

happy coinci-

dences that are the insights which lead to scientific progress. Suchan explanation, however, is not enough. No amount of sti'ongly
motivated inteUeotionisgoing to provide the occasion for die

correct insight, when the tenns of die insight, to be drawn fromseemingly unrelated fields, are not yet discovered. In any case thistheory r^uces to the next.

The real reason for the undeveloped state of the experimental
psychology of smell and taste must be that their stimuli have notyet been discovered. Of their stimulus-objects we know, yes. Sugar
tastes sweet, and violets smell—-like violets. Yet what property is
it that iscommon to sugar and all other sweet sapid substances? In

respect of what physical or chemical attribute are all fragrant objects alike?

And how does one fragrance vary from another? Inother words, what are the mp of smell and the c.p.s. of taste? Until
tire

stimulus-object has been analyzed so that its essential prop-

erty is known, until the true stimulant is discovered, until, in short,

we have a correct ‘theory’ of olfactory and gustatory quality, notuntil then shall we have die means to control and predict odors
and tastes in new situations and thus to determine the psychophysical conelations which make the bulk of systematic knowledge
in any department of sense. It has long been possible to write hugebooks about odors, but the material is casusd and anecdotal without a generality to hold it together. Zwaardemaker spent a largepart of his professional life looking for new physical principles
that would give him the key to smell by an understanding of thetrue nature of its stimulus. He did not succeed, perhaps becausethat essential physical or chemical discovery—if physical or chemi-—cannot he made until some other seemingly unre-

cal it is to belated discovery has occurred or some apparently remote error of

habitual thou^t has been corrected.

Smell
The amount drat is written on a given subject is not an exact
measure of how much there is to say. About smell a great deal has

been written.-Cloquet in 1821 and Zwaardemaker in 1895 contributed the knportant books for their periods, but it was the hand-

EARLY OLFACTORY RESEARCH

439

books tliat created a demand for systematic treatment of the subject.

An editor of a general handbook of physiology could not very

well leave out an entire sense. Let us, then, call the roll of chapterson olfaction in handbooks and special treatises, for, in so doing, weshall outline the history of this field and indicate where the knowl-edge within it can easily be found.
Albrecht von Haller in his Elementa physiologiae of 1763 devoted sixty-one pages to the diapter Olfacius, His treatment,
casual, anecdotal, pathological, was not very systematic, although

he made an attempt at classification. Charles Bell in 1803 had only
four pages to write about smell, but Cloquet in 1821 achieved abook of 758 pages. He dealt, as systematically as one could in
those days, with the classification of odors, the physiological seatof olfaction, its mechanism, its pathology, its practical uses

andindividual diCerences in sensitivity. For over seventy years Cloquet's book was the most frequently cited systematic source on
this topic. Johannes Muller in 1838 could, nevertheless, find only

seven pages of really solid fact on smell for his handbook, and Bid-der contributed in 1844 only eleven pages toW agner’s H ondworter-

buch der Physiologie. Van Vintschgau in Hermann’s Handhuch in
1880, however, had sixty-two pages, because by that time there

had been some experiments on smell and the receptor-cells had
been described. It was shortly after, in 1887, that Zwaardemakerthought of the olfactometer and began his experiments, contributing so much fact and stimulating so many others that in 1895 hecould write his classical Fhysiologie des Gemchs of 324 pages. In
the same year Passy published bis forty-eight-page review of theexperiments on smell. For Schafer’s Text-Book of Physiology Haycraft wrote in 1900 a 113-page chapter, which included a report ofsome of his own researches. Briefer again, Nagel in his HaMbuch
in 1905 had only thirty-two pages, but in 1916 Henning brought
his articles in the Zeitschrift fur Psyohologie together into a bookof 533 pages, the largest since Cloquet. There wore seventy-ninepages by G. H. Parker in 1922, and flien in 1925, thirty years after
the first treatise, Zwaardemaker published in French a revisionand reafifiimation of his treatise, L’odorat. The next year von Skramlik issued his handbook with 345 pages on smell~now the standard

source, since it recounts the opinions and experiments of othersfrom the very beginning. The Handbook of Generd Experimentd

SMELL AND TASTE

440

Psychology in 1934 had sixteen pages by Crozier, and Woodworth's Experimental Psychology in 1938 nineteen pages. One hun-dred seventy-six years, seventeen treatments, 2717 pages.
‘The organ of smell is the nose,’ but at first it was not clear as towhere in the nose the olfactory receptors lie. In 1862, during aperiod of very active histobgical research. Max Schullze, who had

founded the Archie fiir mikroscojrische Anatomie, and who later
distinguished between the cones and rods in the retina, localized

the olfactory membrane high up in the nasal cavity. He foundthere in a small area the olfactory receptors, long cells with halrlikc processes, a discovery which was

confirmed and made moredefinite by von Brunn much later in 1892. Von Brunn described

the olfactory cells and their supporting cells, fixing the area as little

mote than a centimeter across in one of the least accessible partsof the cavity.

Schultze’s location of the organ so high in the cavity raised tirequestion as to whether odoriferous air can reach it as readily andpromptly as olfactory acuity requires. To answer this question,Paulsen in 1882 out the head of a cadaver in half along the medianplane, fixed little squares of Utmus paper at different points inthe nasal cavities, put tire head together, and pumped ammonia

through the nostrils mto the trachea. When the blueness of thelitmus paper showed that the main currents had passed well below

the olfactory region, it became evident that smell must be initiatedby small eddy currents or by diffusion. Franke, repeating this experiment in 1893 with hall of a cadaver’s head covered in the planeof section by a glass plate, drew smoke through the nose and con-firmed Paulsen’s conclusion. Zwaardemaker in 1895 got the same
result with a horse’s head and a plaster model of the nasal cavity.

The effect of these researches was to emphasize the sensitivity ofthe olfactory organ.

Another of the early questions concerned the nature of the stimidus. Did it have to be a vapor or diffused particles, or might it bea liquid? E. H. Weber in 1847, studying the effect of cold andwarmth upon nerve-conduction, had found not only that cold andwarm odorous liquids cannot be smelled when poured into thenostrils of the inverted head, but that eau de Cologne and acetic

add are not sensed at body temperatm'e. He concluded, therefore, that the temperature of these liquids is irrelevant,
it istheir liquidity

and thatwhich renders them ineffective as olfactory

OLFACTOMETRY44]

who had evidence to showde Cologne in the nostrils irritates and thus perhaps

stimuli, In 1886, however, Aronsohn,that eauanosthelizes the sensory cells, questioned this conclusion, He re-peated Weber’s experiment in a more tender manner, filling thenostrils first with normal saline solution, and then gradually intro-

ducing the olfactory stimulus. He got odor, but Haycraft in 1900
failed to confirm his result and was of the opinion that Aronsohn

had trapped air in the inverted nostrils. Thus the decision went
against liquids as direct stimuli,

Haycraft also decided that diffusion is not an adequate stimulus,that the air has to be in motion for the stimulating particles topenetrate to the olfactory membrane. If a person by continuous

deep breathing renders himself apnoeic so that he does not haveto breathe for two or three minutes, if a bottle of ammonia is thenheld for one or two minutes beneath his nose, andifthen hepinches his nose, filled with anunonia vapor, and goes out of theroom into the fresh air and takes a breath, tlien he smells the ammonia only when tire air within the nostrils is set in motion by his
inspiration.
It was Zwaardemaker, a cultivated and erudite Dutch physiologist,

who really created an interest in the psychology of smell.

His own concern about olfaction came out of his conviction thatsmell is like vision, and that the standard laws for vision—sensitivity, adaptation, mixture, compensation,

analysis into specific ener-

gies— could be worked out for smell. As early as 1884, when ho
was acting as physician in a mflitary hospital in Amsterdam, he“asked Nature which are our principal and most elementary smell
sensations and

.

.

.

how do we become conscious of them? But

Nature did not answer.” It seems that the reason for her silence atthat time was that he lacked both an idea and a laboratory, but in1887 at the College of Veterinary Medicine in Utrecht he had both.
The idea was the principle of the simple olfactometer (Fig, 74).
A glass tube, bent up at one end to enter the nostril; a piece ofindia-rubber tubing as stimuhis to slip loosely over and along
the other end; a small screen between the observer and the rubber;a scale on the tube to show how far the mbber projects beyond theglass and thus how much rubber is exposed for the air, sniffed by

the nostril, to pass through. With such a device the threshold could

be measured, and Zwaardemaker called the number of centimetersof exposed rubber necessary to produce a just noticeable odor anSMELL AND TASTE

442

using it as a unit of intensitive measurement. “That is

olfactle,

beautiful,” remarked Dondeis, Zwaardemaker’s teacher, when hesaw the olfactometer, “for it is simple.” “It is also useful,” Zwaardemaker replied, “for now we canmix odors, as you mix colors inyour double-slit spectroscope, using odor equations

instead ofcolor equations.” And mix odors

Zwaardemaker did, determining
the laws

compensation, inof

terms of olfacties, and the rates
of adaptation.

The
Sossia Osjaotometer;
ZwAABDKMAKEH (1888)

first

determinationofthe absolute threshold for smell

Fig, 74,

S is a tube o£ odoiitetous substance, like india-rubber, winch
sbdes Qvei the glass tube T.
scale

The

on T measures the distancebeyond the end ofthat S projects

hence

T,

the

distance

that

air,

N, passes
over the olfactory stimulus, hence

sniffedtheby aintensity

nostril

of

the

at

stunulus.

A

double olfactometer consists of two
sunple olfactometers, one for eachhad been made, however, before Zwaardemaker’s inventionin 1884 by Fischer and Penzoldt,

By allowing, fii'st, an odorous substance to diffuse in a standard

chamber, weighingitcarefully

before and after diffusion andfinding

then

its

loss inweight, anddetermining thedilution

in

air

for

greatest

which thenostril.

odor could be sensed, they determined the minimum perceptible concentration of the stimulus.

It

was in this research that the much quoted figure formercaptan was found, a dJution of 1 in 60,000,000,000 parts being
perceptible, or 1/400,000,000 mg. in 500 co. of inspired air—asensi-

tivity which these investigators computed to be three times as great

as the sensitivity of the spectroscope to sodium. Inasmuch as thismethod of dilution has been used by most of the investigators subsequent to Fischer end Penzoldt, die handbooks now give tablesof thresholds for a considerable list of materials. With the true

nature of olfactory stimulation still unknown, however, no generalstatement of the threshold in energetic terms has ever been possible as it has for vision and hearing.

The advanjiage of the olfactometer became obvious in Zwaardemaker’s subsequent researches. The technique of his instrument

he devekped as olfactometry, and the measurement of intensity

LAWS OF SMELL

443

as odorimetry, bringing tlie accumulating body of fact together
in his book in 1895.

Although he determined differential limens

with tlie oUaclometer, it was not until later that the question of
the validity of Weber’s law was definitely raised. Gamble in 1898

found the Weber fraction to vary between% and with nearly% and %, an av-

two-thirds of the determinations lying between

erage ratio of about .32; and Hermanides, Zwaardemaker’s pupil,
to 1909 found equally great variabflity

and an average ratio of

about .88. Because neither of these investigators discovered great
differences in the fraction at different intensities, they both con-cluded that Weber’s law appbes approximately to smells; but Hgler

and Holway with an improved technique showed in 1935 that thefraction for india-rubber decreases steadily from the low intensities
to the high, reaching a minimal ratio of about .10 at about 200 olfacties.

From the start it was clear that adaptalion in smell is considerable and rapid; Zwaardemaker by use of the olfactometer was able
to plot its curves.

The most interesting thing about adaptation,

however, turned out to be its mutuality. Aronsohn found in 1886
that adaptation to ammonium sulphide diminishes sensitivity tohydrogen sulphide and to chlorine and bromine vapors, and also
prevents the perception of certain ediereal odors; that adaptation
to camphor abolishes the perception of ether and eau de Cologne.

In this discovery there seemed to lie the possibility of a classification of olfactory stimuli and an insist into die nature of the stimulus by a determination of the chemical community of equivalentstimuli, but nothing ever came of it.

Perhaps the most important result of Zwaardemaker’s use of theolfactometer to find for smell the analogies of the laws of color

mixture was his discovery of olfactory compensation in 1889. He

was able then to designate various pairs of odors whidi act antagonistically—pairs which, in mixture, result in the perception of

only the stronger component or even in mutual cancellation. Suchantagonism he held, moreover, to be physiological: if one stimulus

be presented to one nostril and the other to die other by use of adouble offactometer, there is still compensation. Ammonia andacetic acid tend thus to neutralize each other. ’They would, to be
sure, neutralize each other chemically if allowed te react, but it

was Zwaardemaker’s claim that cancellation comes about likewise

when each is presented to a different nostril. In this finding there

SMELL AND TASTE

444

seemed to lie another hint for an understanding of the nature of
the olfactory stimulus, but unfortunately the relationships are by
no means simple or predictable. For instance, of the four substances, beeswax, paraffin, tolu-balsam and india-rubber, Zwaarde-

maker reported that every one of the six possible pairs except
paraffinand tolu-balsam act antagonistically. When stimuli an-tagonistic to the same stimulus are still antagonistic to each other,all

we learn about the nature of stimulation is that not so manydifferent processes of smell can be excited at once. Hcrmanides,

although verifying Zwaarderaaker for both “unilateral” and “bilateral” stimulation, noted that cancellation is more often incom-

plete than complete, and that there can be alternating rivalry be-

tween the two odors.
In 1915-1916 Hans Henning adopted from Stumpf s terminology
for tones {monotic, diotlc, dicholic, p. 382) the terms monorhinic
for smelling witli a single nostril, dirhinic for smelling the same

stimulus with both nostrils, and didiorhinic for smelling a different
stimulus with each nostril. He contended that there is never any
didhorliinic compensation,

pensation,and that dirhinic or monorhinic com-when it occurs, is chemical. Wlion Zwaardemaker,

nevertheless, reaffirmed his position in 1925, the matter was left in

the air, with die admission that complete compensation is rare andrequites, at any rate, very careful adjustment of the stimuli,

The clas^fkailon of odors on the basis of qualitative similarity
is themost obvious and therefore the oldest form of tboir scientificccnsideratian. The earliest classification which remains of impor-tance today was made in 1752 by the great botanist, Linnaeus, who

was forming a system for the description of the odors of plants.

He made out seven classes; (1) aromatic, (2) fragrant, (3) ambrosiac,(4) affiaceous, (5) hirdne, (6) foul, (7) nauseous. Haller,

the physiologist, on the other hand, offered in 1763 but a threefold dassifioation; (1) sweet-smelling or ambrosiao odors, (2) in-

termediate odors, (3) stenches. Besides these, there were also in
the eighteenth century two classifications based on chemical characteristics of odoriferous substances, one by Lorry in 1784 and one
by Fourcroy in 1798; and then there were at least five other littleknown attempts in the nineteenth century before Zwaardemakertackled the problem in 1895. Zwaardemaker ended by accepting

the classification of Linnaeus and adding one dass of Lorry's andanother of Haller’s to give nine:CLASSIFICATION OF ODORS

445

1.

Ethereal odors (Lorry): the fruity etliers of perfumes, bees-

2.

Aromatic odors: camphor, spices, anise, citron, almond, etc.

wax, ether, etc,

3.

Fragrant odors: flowers, vanflla, balsam, etc.

4.

Ambrosiao odors: amber, musk, etc.

5.

Alliaceous odors: onion, acetylene, iodine, etc.

6.

Empyreumatio odors (Haller) roasted cofiee, tobacco smoke,:

xylol, naphthahn, etc.
7.

Hircine odors: goaty odors, cheese, sweat, chestnuts, etc.

8.

Foul odors: narcotics, some bugs, coriander flower, etc,

9.

Nauseous odors: carrion, carrion flower, feces, etc.

Actually there were in all these groups subclasses, for which

Zwaardemalcer gave long lists of examples. This classification, having the authority of the expert on
smell,

met with general accept-

ance up to the time when Henning invented the smell prism.

The smell prism was the resultof an elaborate investigation of

the qualitative similarity of odors

by Henning in 1915, Having had
his observers arrange great num-bers of olfactory stimuli in many
qualitative series,

construct a

he sought tosuperordinate con-tinuum into which all the series

would

fit.

The

result

was the(prism of Fig. 75. In it there areThe

six principal groups of odors. In-

six1915 )

principal

classes of odors are

qualitative

shown. Inter-termediates between the groups

mediate qualities lie on the edges

are represented as lying on theor in the surfaces,*

edges or in the surfaces, but not in the inside. Though the principal groups are related to Zwaardemaker’s, the instances differ considerably, Tliese are Henning’s principal classes:
1.

Ethereal odors (£), corresponding to Zwaardemaker’s ethereal group,2.

Fragrant odors (F), corresponding to Zwaardemaker’s fragrant group.

3.

Spicy odors (S), corresponding approximately to part of

Zwaardemaker’s aromatic group

SMELL AND TASTE
4.

Resinous odors (R), corresponding approximately to the5.

Burned odors (B), corresponding to Zwaardemaker's empy-

other part of Zwaardemaker's aromatic group.

reumatic group.
6.

Putrid odors (P), corresponding to Zwaardemaker’s foul andnauseous groups.

Zwaardemaker’s alliaceous odors fall for Henning in the middleof the FPSB face (Fig. 75). His hircino odors do not fit the prism.

For instance, myrtle is hirdne for Zwaardemaker, but SR for
Henning. Balsam

isresinous for Henning;it

was fragrant for

Zwaardemaker. The animal fetors lie on the PB line; Henning,
missing examples for this part of the figure, found them in the

Table V. IlEPKESENTATtvB Stimdlus-Objects job Henning's Smell Phism
Simplex odors(comers)

F = violet
E = lemonS= nutmeg

B = balsam

B = tai
P = hydrogen sulphide

Duplex odors

Quttdruplex odors(edges)(faces)FE = Kranium

FESH = cedar

FS — Siyme

FPSB — gnrlio

ES=pineEPBB = grapefruit

SR = cmnBmon
FP = carrion flowers
PB = animal fetors
SB = roasted coffee

EP = ahnond
RB = incense

Hamburg zoological gardens. Arbor vitae and its botanical relatives of the thuya genus lie in the middle of the

FESR face. Shad-dock (grapefruit?) is in the middle of the EPRB face. Common
objects which represent the comets, edges

and surfaces of theprism according to Henning are listed in Table V.

At least three experimentalists have undertaken to confirm thequalitative relationships implied by Henning’s prism. All by differ-ent methods reached the same result; as a gross approximation theprism can be verified, but the verification fails as to detail. Apparently Henning never meant that it should be taken too exactly,
for ffiere are some difficulties inherent in the system itself. Must,for example, every

PR odor be ipso facto an ES odor? Henning

does not say so, but the prism implies it.

Alfhough ^ell is always said to be one of the two chemical
senses, there is nodear evidence that chemistry will eventuallyprovide the knowledge of the essential nature of the olfactory:

CHEMISTRY OF SMELL

447

stimulus. The mere fact that different substances have different

smells and also different chemical constitutions does not make ofsmell a chemical sense. Different substances have likewise differ-ent colors and different chemical constitutions, and yet color vision
is not for diis reason a chemical sense.

The nature of the olfactorystimulus still escapes the psychologists; yet we may consider here
three attempts to fe its chemical nature.

At the very beginning of this period of experimental interest in
smell. Sir WUliam Ramsay suggested (1882) that theadequacyof a stimulus for smell might depend on its molecular weight, thatthe olfactory threshold might lie at a molecular weight in theregion of 30. He noted the marsh-gas series ( CnH^+a )Methane, CH,, with moleeniar weight
Ethane,CiHo, with molecular weight
Propane, CiHi, widi molecular weight

Hydrocyanic acid (molecular weight= 18, odorless;= SO, odorless;= 44, has an odor.

= 27)

is

is

is

smelled by someand not by others; and Ramsay cited other instances as well toshow tliat substances with light molecules tend to be odorless. Hisview received support in 1892 from Passy, who showed that therelative effectiveness of the various alcohols increases with theirmolecular weights, as indicated in Table VI. It was Ramsay’s idea

Table VI. Olfactohy Eftectiveness or Alcohols as a FoHcrnoN
OP Molecolak Weight
FormulaSubstance

Metlwl alcohol

caoH

Ethyl alcohol
Butyl alcohol

C.H,OH
C.H,OH
C.H,OH

Amyl alcohol

GHaOH

Propyl alcohol

Molecular weight

Relative efectiveness

32
46
60
74
88

4
100
1000
10000

1

that smell. Like vision and hearing, may be a vibratory sense, that—the lighter molecules vibrate too rapidly

gen at 44^he set the rate for hydro-

X 1-0“ vibrations per second—to affect the receptor

cells.

Haycraft, in 1887 and later, undertook to relate odor to Men-deleev’s Periodic Table of the chemical elements. That table wasreceiving considerable attention just then, for in 1886 the third of
the unknown elements that MendeMyev had predicted from his
table in 1871 had just been discovered. Haycraft sought to use
this new chemical system to order the smells. That chemicals re-lated in the periodic series often have related quahties of odor heSMELL AND TASTE

448

was able to demonstrate. Thus sulphur, selenium and tellurium
constitute a series of closely related elements, and their compounds
tend to form an olfactory series of similar odors, with the odor of
the selenium compound lying always between the odors for thesulphur and tellurium compounds. It is the same for the halogens(chlorine, bromine and iodine) and Haycraft was able to point tosome similar organic series. The view, nevertheless, although it
was suggestive, id not go far enough, partly because organic substances(compounds of hydrogen, carbon and oxygen) are thechief source of olfactory stimuli; hence the key to smell is not likely
to be found in the Periodic Table.

For this reason Henning in 1916 undertook to fit an organic
chemistiy to his prism. He centered his theory upon the odors of
the substitution-products of the benzene ring, which is a closed
ring of six carhon atoms with one hydrogen atom attached on tlieoutside to each carbon atom. Other groups of atoms can be substituted for a hydrogen atom; the character of the resultant com-pound depends, when there are two such substitutions, upon
whether the substitutions occur at adjacent corners of dio ring(ortho-substitution), corners next but one (incta-subslilution), or

opposite coiners (paia-substitution). Although such compounds

may to a large extent account for F, E, S and R, Henning had toconsider other elements for the P and B groups. Here is his theory
for the six principal qualities:

Fragrant; ortho-disubstitution (at adjacent corners)on thebenzene ring.
Spicy: para-disubstilution (at opposite corners) on the benzene
ring.

Resinous: closed disubstitution on the ring, where a single substitution group is united with the ring at two corners.

Ethereal: monosubstitution at one corner on the ring of a forked

group of atoms.

Burned; smooth heterocyclic ring which involves nitrogen at

one comer instead of carbon.
Putrid; forked stracture ( no ring) involving elements in the Vthand Vlth groups of the Periodic Table, like ai'senio, bismuth, phos-

phorous, sulphur, selenium, tellurium.

About the FESR-faoe of the prism Henning was able to be logical.

A trisubstitution product which is a combination of ortho-

CIIEMISTRTf OE SMELL
substitution449

and para-substitution would lie, he said, on the FSedge; and similarly the other binary combinations on the otheredges.

As a test of the theory Henning called attention to the

FFSR-point near the middle of the FESR-face, a point where thethuya genus of evergreens ( aibor vitae, cedar ) belongs. The active
principle of these odors is thuyol, and tlie structural formula for it
isactually a combination of ortho-substitution and para-substitu-

tion at three comers of the ring, with a closed chain across twoother corners and a fork to one of the substitution products, The

theory is logically beautiful as it applies to the FESR-face of the—^presumahly because

prism; yet it has failed of general acceptancethere are many exceptions to it and many odorous substances that

do not come under it. Psychology still lacks a chemistry of odor.

The handbooks used to carry discussions of the olfactory specificneroe energies. Tlic complexities of color had been reduced tothree elementary nervous processes by Helmholtz, or six by Hering, just as, in like manner, the complexities of touch had in 1883-

1884 come to be understood as combinations of four specific energies (pressure, warmth, cold, pain). If there are as many odors
as colors— and some said there were—must not there be a similar

reduction in smell? The classifications might have provided thisanalysis, but they did not.
it,

A chemical theory might have provided

but there has never been a thorough-going chemical theory. The

failure to make the analysis is simply a phase of the failure to makethe crucial discovery about smell, to find the essential nature ofitsstimulus.

Taste
The experimental psychology of taste has even less history thanthe experimental psychology of smell,

We can deal with it ex-peditiously.
If a physiologist discussed the senses, inevitably he had to dis-cuss aU of Aristotle’s five; and of these taste is one. So Haller—withwhom we may start in 1763—had his book on Gustus, in which hedescribed the various forms of papillae. Inasmuch as anatomy was
far ahead of physiology, his account was pretty good. That these

papillae might be the organs of taste seemed reasonable enough,for the tongue can taste and they were the only special structuresin sight. Furthermore, he made out a classification of tastes underSMELL AND TASTE

450

six heads with a discussion of the sapid objects cliaracteristic ofeach class, concluding with die observation that substances, if they
are to be tasted, must be soluble in saliva.

Johannes Muller, on the other hand, in 1838, was primarily interested in showing that taste corresponds to one of the five spedflc

energies of sensory nerves, in other words, that mechanical andelectrical stimulation, as well as sapid,

quality,

can give rise to the taste

Because he knew about Horn’s research in 1825 {videinfra), an experiment showing die different papillae to be differ-

ently sensitive, he could, with more assurance than Haller, assertthat the papillae are the gustatory organs— or even with more as-

surance than Charles Bell, who had made the same statement in
1803. Muller also, although he noted that sapid substances must be
soluble, hazaided the incorrect guess that some gases may be di-recdy tasted. Remarking on the fusion of tastes and smells in flavors,

he pointed out that the smells can be eliminated and thetastes left simply by stopping the nostrils. Repetition of gustatory

stimulation,

he suggested, renders the perception lessdistinct;

neverdieless it is only recently that die long skepticism about gustatory adaptation has been finally dismissed by the disooveiy thatit occursquite rapidly.

Bidder’s contiibution on taste to Wagner’s HandwMerbuch in1846 did Httie to advance the knowledge of the subject, but vonVintsohgau’s to Hermann’s Handbuch in 1880, introducing, as it
did, a period of active research, marks the beginning of the belief

that sweet, sour, saline and bitter are the four elementary qualities—a belief that was not fully accepted, however, for twenty years.
Haycraft’s contribution to Schafer’s Text-Book in 1900 was important, partly because of his chemical theory of taste; but Zwaarde-

maker’s chapter in 1903 had in it nothing very new. ’The best mod-em discussions are those of Parker in 1922, von Skramhk in 1926,
and Crozier in 1934. The field has not, however, been active inthese last two decades. The classical experimental investigations

were made by Oehrwall in 1891 and Kiesow in 1894-1896.

As we have seen, the papillae on the tongue were early selected
as the organs

d taste. ’Ihat was Haller’s opinion (1763), asCharles Bell’s (1803)

it wasand Johannes Muller’s (1838), The taste-buds were discovered in 1867 independently by Schwalbe andLoven. Schwalbe was a pupil of the Max Sohultze who described:

ORGAN OF TASTE

451

the olfactory cells and the retinal rods and cones. He called the or-gans taste-beakers, presumably having in mind some kind of glassthat curves in at the top like a modem brandy glass, Loven called

them taste onions or buds, for the spindle-shaped gustatory cells
bulge out from the root and come together at the taste-pore, verymuch like the petals of a bud, These Tiuds’ they both found in the‘ditch’ around the papilla, many in the wall of the papilla itself,some in the opposite wall. Though Schwalbe was uncertain how
many buds there might be in a single papilla, his sketches show
as many as ten at different depths in the side of a papilla hig
enough to allow for 42 buds armmd its circumference. Tliat would
make over 400 buds in the walls of the papilla with still more on
the outside of the ‘ditch.’ Von Wyss in 1870 estimated the number of buds at about 400 per papilla, and Krause in 1876 thought
there might be as many as 2500. An accurate count by Heiderichin 1906 showed 508 as a maximum, 83 as a minimum, with theaverage lying somewhere near 250. So there were plenty of receptors to go around among the qualities, which no one seems to havethought would be more than a dozen and which eventually turned
out to be four.
Charles Bell in 1803 had strengthened belief in the papillae as
the organs of taste; he demonstrated that, not only is the tongue
insensitive to taste where there are no papillae, but gustatory sensibility is generally confined to the tip and edges of the tongue andis absent in the

middle of its surface. Horn in 1825 took a further

step in showing that different papillae are differently sensitive tovarious sapid substances, thus indicating the possibility of a physiological analysis of the many tastes into a few. Later, when the four

elementary qualities were coming to be accepted, there were more
careful investigations of the differences in sensitivity among papillae.

Oehrwall in 1891, having discarded his saline solution as

unsatisfactory, published the foDowing inventory of the sensitivities of

125 papillae to his particular stimuli (sugar, tartaric acidand quinine at predetermined concentrations)
Sweet, sour and bitter 60

Sweet only3

Sweet and sour

12Sour only

12

Total

Sweet and bitter

4

Bitter only

0

125 papillae

Sour and bitter

7

None at all 27=

SMELL AND TASTE

452

He might, if he had used the base of die tongue, have found papillae sensitive to bitter alone. As it was, he left little doubt of tlie

physiological distinctness of these three tastes.

That sensitivity to the four elementary tastes varies with the region of the tongue was Shore’s contribution in 1892. Using glycer-

Fio. 76.

DisTBiBimoN of Taste SENsrnvini Along tue Edge of the
TonguE! Hanio (1901)
and is plotted as aThreshold diita (ram Ilanig. Saune and sow

Sensitivity is the leclpiocal of the thresliolcl value
tatio of maximal sensitivity—

1.

are least clearly differentiated. Staeet and hltfei' oio antithclical, and clearly
differentiated {torn each otlier and from saline

and sour.

ine for sweet, sulphuric acid for sour, quinine for bitter and sodium

chloride for saline, and determining thresholds for all, he reported
relative sensitivity according to the difierences

shown in Table

VII. Kiesow in 1894 verified Shore’s generalization, and Hanig inTable VII. Relative Gustatoby Sensitivity of the Tongue;
Shore (1892)
Region

Sweet

Sour

BitterSalineTip of tongue

high

low

Edges of tongue

low

high

low
low

Base of tongue

mediummediummediummedium

Dorsum of tongue

low
high
no sensitivity, even for strong solutions

1901 worked out the quantitative functions which have beenplotted in Fig. 76. These researches, showing the existence of four
different patterns of sensitivity, indicated clearly that there mustbe at least fouj different physiological processes of taste. They did
not, however, show that there are only four.

The question of the number of gustatory qualities first arose in

ELEMENTARY TASTE QUALITIES453

the classifications of the tastes. Bravo listed nine classes in 1592,

Linnaeus eleven in 1751, and Haller, also in 1751, twelve, which

he reduced to six in 1763. English equivalents of all their Latin adjectives are given in Table VIII. Of the sixteen qualities in tliat table, only five appear in all four classifications:saline (the four that eventually survived)

meet, acid, bitter,and sharp. All three

men gave insipid as basic, but Haller dropped the class in 1763. It
is hard to make some of the distinctions real, as between insipid andaqueous, sharp and pungent, spirituous and aromatic,

Table VIII. Early CLAasmcAnoNs or Tastes
Bravo: 1592

—
—

sweet
.

acid

sharp

Linnaeus: 1751

•spirituous

acid

•acid

aslringenl

sharp

aromatic——•sharpliai£

harsh
viscous
fatty

fatty

bitterbitterinsipid

msipidsaline•sweetpungent

miugent———

HaUer: 1751

—
—

sweet

aaueous—salinenauseous•bitter

Insipid"•salineurinousputrid• Haller’s six classes in 1708

From multiplicity in the eighteenth century, opinion changed toparsimony in the nineteenth. Zenneok in 1839 and Valentin in 1848
held that there are only two qualities of taste; meet and bitter.
Physiologists were beginning to be aware that they must abstract

the tastes from the tactual qualities. Thus Valentin referred sour,
saline, sharp, burning and cool to touch. Stich then in1857 wasobliged to argue that sour is after all really a quality of taste be-cause it cannot be got from all parts of the mouth cavity, which arenevertheless tactually sensitive. Similarly SohifE in 1867 held thatsour cannot be tactual because add too weak to be perceived assour can nevertheless be felt. Still Duval in 1872 was arguing that
only sweet and bitter are incontestable as qualities, that acid, saline

and alhiline are dubious and probably due to touch.

Meanwhile the problem had become important because the tale

SMELL AND TASTE

4S4of the qualities was seen to be also the tale of the specific nerve

Von Vlntschgau in 1880 decided definitely in favor ofenergies.

four specific nerve energies: sweet, sour, bitter and saline. Thisdecision he made after his experimental deteiminations of gustatory thresholds had shown that sensitivity varies independently forthese four tastes. He naturally chose the smallest number of ele-mentary qualities possible, because the pressure of the theory of
specific energies

was toward parsimony. In spite of Helmholtz’s

extravagance with specific energies in his theory of hearing, thechief use of this principle was to show how the organism can get

multiplicity of qualitative discriminations out of paucity of physiological processes. Wundt in 1880 and 1887 held to six qualities:

sweet, sow, bitter, saline, alkaline and metallic (the last a newword for what had been called astringent). Oehrwall in 1891, however, supported the basic four, with the result that Wundt in 1893

and thereafter expressed doubt about the alkaline and metallic
tastes. Oehrwall believed that he had definitely analyzed the alkaline, metallic and astringent tastes into fusions of taste and touch.

Insipidity he concluded to be also a matter of touch, due to theabsence of carbon dioxide. Water, he found, always tastes insipid

when all the carbon dioxide is removed from it; and, conversely,
insipidity is always removed from a solution by the addition of carbon dioxide. (Thus sodawater and carbonated drinks.) Kiesow,

who also in 1894 held to these four basic qualities, nevertheless, in
1896, designated insipidity as a quality due to the mixture of sweet—a Mischempfiridung

and saltlikeorange from red and yellow.

Although this ‘discovery’ of a fifth quality by Eiesow was never
the researches of Oehrwall, Shore, Kiesow and
Hanig in 1891-1901 on the differences in distribution of the four

finally accepted,

accepted basic qualities (vide supra) were enough to establish—even though Sternberg did argue as

themlate as1898 for only

sweet and bitter as basia Wundt kept on in the editions of his
Fkysiologische Psychologie saying that alkaline and metallic are
doubtful, until Herlitzka in 1908 administered the coup de grice
to metallic by a special study in which he reduced it to a fusionof tastes, smells and touches.

Along with this problem of specific nerve energies, which had
been under consideration since 1880, there had been coming up
the question of moddities. Helmholtz had said that different qualities belong to different modalities

when they have no intermediates.

TASTE QUALITIES455

Red and yellow are of the same modality because they are connected by the oranges, but color and tone are of different modalities, Does taste thenconsist of four modalities? is it four separate

senses? Oehrwall was inclined to say Yes, but his view was neverpopular. Finally in 1916 Henning constructed the taste tetrahedron(Fig. 77) settling the problem to everyone’s satisfaction. Sweet,
sour, bitter and saline arc, accordSALINC

ing to him, principal qualities
that lie at the four corners of thisfigure.

In between them on the

edges

lie

intermediate qualities

like the salty-bitter of potassium

iodide, which is just as simple as

an orange or a purple. These intermediates arise, he thought, notfrom mixtures of the stimuli forthe principal tastes, but from simple substances

Fie. 77. Tasti Tbtrahbdrom:

Hsnning (1916)

whose chemical

properties are intermediate be-

tween the chemical properties ofThefour principal qualities oftaste are shown. Intermrfiate qualities lie on

the substances that lie at the corners of the figure

the edges or in the sur-faces.

{Me infra).

The olwmi^ry of the sapid stimulus has never been successfully
worked out for all the tastes. Haycraft in 1886 studied the subject
in relation to Mendeleyev’s table, as

he did later for smelL His

chief conclusion was that saline, for which NaCl (sodium ddoride)isthe representative stimulus, depends upon the combination ofa metal (like Na) from group I of the periodic series with a halo-gen (like Cl) or a similar substance from group VII of the series.
Fluorine and chlorine combined with any metal of group I taste
saline, but the heavier halogens(bromine and iodine) combinedwith the same metals taste sdly-bitter. So do the sulphates of these
metals, compounds in which the S04-radical acts like an elementof group VI. It is also true that the chlorides of the metals of group
II are salty-bitter. Haycraft’s generalization was that any oonsider-ahle chemical deviation from sodium chloride (to group II fromI,

or to VI from VII, or to heavier elements) introduces bitterness

with the saline taste.
In 1884 Arrhenius published his important paper on the electrolytic theory of solutions, a crucial paper although slow of ac-

SMELL AND TASTE

458
ceptance.

By 1898, however, there wore two men who saw that

this new theory might contribute to an understanding of the gusta-

tory stimulus, tliat attention must be paid to the ionization of solutions, since it is only solutions tlrat stimulate taste. Richards pointed

out that, since all sour acids have free hydrogen ions, the stimulus
to sour must be

the hydrogen ion. For inorganic acids (hydro-

chloric, sulphuricand nitric) he was able to show that sourness

varies with the degree of ionization, but he was baffled by the factthatsome organic acids(tartaric, citricand especially acetic),

though much less ionized tlian the inorganic acids, yet taste more
sour. Kahlenberg came to the same conclusion at the same time.

His decision was that acetic acid is four times too sour tor its degree of ionization. That it must be the hydrogen ion wlrich is effective for sourness both these men were convinced, for Ihe othercomponent of the acid may occur in a salt solution without giving
rise to the acid taste. Hydrochloric acid, for instance, provides

Hand Cl ions; sodium chloride provides Na and Cl ions. The former
tastes sour, the latter saline. Hence it must be the

H ions that taste

sour.

This same logic would indicate that it

is

the

Na in sodium

chloride which tastes saline, since Cl is also in hydrochloric acid.

Kahlenberg thought not, however, because sodium acetate,al-though ionized, is not salty. He believed that the H ions to HClmust be more effective than the Cl ions, which may still be the true
stimulus to the saline taste.

Sternberg, who published to 1898, took up the problem so far

avoided by the others: die stimulus for sweet. It was his conclusionthat the lighter elements from the groups in the middle of theperiodic table enter into sweet substances,muth, carbon, nitrogen, and oxygenfrom group II to group VI—are apt—

all

Thus beryllium, bis-

light elements ranging

to make stimuli sweet, as does

also lead, which is heavy but lies to the very middle of the series ofgroups. The stimuli for bittei' Sternberg placed outside this zone atdie extremes of the table, thus recognizing an antithetical relation

between sweet and bitter.
Although Cohn to 1914, in an elaborate study of sapid substances,attempted especially to get at the nature of the stimuli for sweetand bitter, he met with little success, It was plain to him that theanswer to this question would be found in organic chemistry andnot to the periodic table. The alcohols and sugars are the natural

.

CHEMISTRY OF TASTE

457

stimuli for sweet; the hydroxyl ion is swcel, but beyond that there
is little generalization possible for the “glucogenes,” asCohn caDed

the essential stimuli for siueet. Bitter comes from the alkaloids, hesaid, likequinine and especially stiychnine. The NOs-radical isNO2 alone

bitter if present in the molecule in sufficient amount;isnever bitter, (NOj )2 is sometimes bitter, (NO 2 )3 is always bitter.
Finally Henning in 1916, reviewing this literature and testingout chemical series for himself, was able to list certain elements

and radicals that characterize the four comeis of his taste tetrahedron, and to find some chemical intermediates which represent theintermediate qualities along the six edges. Here are some of his
stimulating elements:
Salt; NaCl is the best.

Sour;

H ions.

Sweet: Al, Fe, Be, Pb; the radical

OH hydroxyl
NO 2(

Bitter: two or mote units per moleaile of S or
Sall-biiter:).

K is more bitter than Na; tlie scries Cl, Br, I moves

toward bitter; hence the series NaCl, KCl, NaBt, KBr, Nal, KI
progresses from pure saline well on toward tlie bitter corner.
Salt-sour: sodium carbonate, ammonium chloride, the reasons forwliioh are not clear.
Salt-sweet: potassium hydroxide, in which thesalt and tlie

K furnishes the

OH the sweet.

Sour-sweet: CO.OH, in which the

OH furnishes the sweet; lead

acetate, in which the Pb famishes the sweet.

Sour-bitter: calcium sulphate, in which the SO4 is bitter.

Sweet-bitter: NOa or S, occurring only once in the molecule;CO(carbonyl).
It is plain from this account that the stimulus to taste is stiU un-

known, except for such gross generalizations as that hydrogen ionstaste sour, salts taste saline and may deviate toward bitter or sour,alcohols and sugars are sweet, alkalies are salty-sweet, alkaloids

are bitter.

Although there have been in addition other investigations in thesense of taste, they do not add materially to the historical account.

The experiments on mixture, compensation and contrast seem tohave been inconclusive. Adaptation, suggested by Johannes Muller,

was doubted, or was believed to lake a very long time, until B.

Mayer in 1927 showed that it is rapid and that recovery too is rapid.
Since Mayer there have been several other studies. Von Vintschgau

SMELL AND TASTE

458

and Honigschmied in 1875-1876 published the classical results ongustatory reaction times, and these differences of times were used
to differentiate the taste qualities. The times may, however, indicate, not the latent time of the receptor, but its degree of inaccessibility in the papillary ‘ditch.’ There were many determinations of

the threshold in terms of the concentration of solution necessary to
excite the taste, but no satisfactory detennination of the Weberfunction until it was made by Holway and Hurvich in 1937. If

only the nature of the gustatory stimulus were to become known,

undoubtedly all these problems would receive a new lease of life.

Notes
1925; E. von Sbamlik, Handhuoh
der Physiologte der niederen Sinne,

Smell
The important treatises and handbook cliapters cited in the text for
smell are as follows: A. v. Haller,

Elementa phijsialagiae, 1763, Bk.
XIV, whiolt is Vol, V. 125-185 of
the Lausanne ed.; H. Cloquet, Disaertation mr lea odmra, sur le aena
et lea orgones de I’olfactlon, 1815,
In.v.], of which the very much enlarged 2 ed. (practically a newbook) had a new title, OsphfdjioZogle, ou traits des odeura, du aena
et dea organea de I'olfacHon, 1821;
F. Bidder, in R. Wagner’s HandteSrterbuch
1844,
in

L.

der

Hermann's

Fhyeiologte, III,J.

FhysioZogte,

018-926; M.
li,

v,

II,

Vintschgau,

Handbuchder1880, 225-286;

Pasay, Revue gdndrale sur les sen-

Die Phijslologie des Geruche- undGeschmackssitmea, 1926, 1-345 (diestandard
andfullesthandbookX,source);W.

J.

Crazier,Cbeinore-

ception, Ilanabook of Geneial Ex-

perimental Psychology, 1934, 9871036 (bibliography of 130 titles);R. S. Woodworth, Experimental Psychology. 1038, 477-495.

On die location of die ol/actory
membrane, see M. Scliultzc, Untersuchungen liber den Bau dor NasenAhhandl.

schleinmaut,

GeaeU. Halle,

7,

naturforach.

1863, 1-100, csp.

70-78; A. von Brunn, Beibage zui
mikroscopischen Anatomle der menEchlichen

Nasenhoble, Arch. mikr.

Anof., 89, 1892, 632-651.

On

the

mooement

of

the

air

from Z. Psychol. 74-78, 1916-16);
G. H, Parker, .Smell, Taste and Al-

through the nasal cavides, see E.
Paulsen, Experimentelle Untersuchungen iiber die Strdmung der Luftinder NasenhShle,
Silzungsher.
Akad. Wise. Wien, 85 ( 3), 1882,
352-373; G. Fianke, Experimentelle
Untersuchungen iiber Lufldmok,
Lnftbewegung und Luftwochsel inder Nase und diren Nasenhdiile,
Arch. Laryngol. Rhinol, 1, 1893,
230-240; Zwoardemaker, Die Phyaiologte dea Gerudha, 1895, 49-51;

lied Senses in the Vertebrates, 1922,

Hayeraft, op.

sations olfactives, Antide paychol, 2,

1895, 363-410; H. Zwaaidemaker,
Die Physiologie dea Oeruchs, 1895

(the olMsical experimental treatise);J.

B. Hayeraft, in E. A,

Schafer’s

Text-Book of Fhtjaiologi/, n, 1900,
1146-1258; W. Nagel, in Us own
Handbuch der Phusiologie, HI,
589-620; H. Henning. Der
Ceruoh, 1916 (reprints four papers
1905,

23-91 (bibliography of 80
dues); H. Zwaaidemaker, Vodorat,
eap.

cit.,

1900, 1256 f.

On the adequacy of liqttida as
olfactory stimuli, see E.

H. Weber,NOTES
Ueber den Einfluss der Erwarmung
und Erlcaltung der Nerven aui

459

general

Psychol,,

12,

1935,

372-

382.

Amt,

On adaptation and fatigue, see E.

Fh^M, Berlin, 1847, 342-3S6, esp.

Aronsohn, op. cfi., 1886, 342-349;
Zwaardemaker, op. cit,, 1895, 203207; Hermanides, op. cit,, 1909, 1421
On compensation, see Zwaardemaker, Compensation von Gerilchen

Leltungsvermogen, Arch.

ihr

351-354; E, Aronsohn, Experimentelle Untersuchungenzur PhysinGeruchs,

des

logie

330; Hayciaft,

For

see hiscit.

ofZwnarde-mittelst

smcU andFoitsohr,

history

invention

his

loc,

the

olfactometer,

731,

An intellectual history of a

per';

of

physiologist

with psychologicalpirations, inA Uiitory of Psychol-as-ogy in Autobiography, I, 1930, 491516,

esp.

491^04. Altogether

papers on smell out of a

On Mssificaiion of odors, see in
who

213,

All thefromearly papers deal with the olfacto-

fully,

titles.

meter. but the paper that marks its
inventionis

Die Bestimmung derGeruelisschiirte, Berliner liUn. Woch-ensohf.,1888, 950 f. On thesea Die P/iysioiflgte

25,

olfactometer,

des Geruchs, 78-130.

14

gives

oil.,

198-

classifications

Linnaeus to Henning quitewith Usts of substances thatfall in the classes. For the classifications menlioned in the text, see K,
von Linnd (Linnaeus), Amoenteies
ecademicoe,

1756, the chapter

III,

Odores medicamentorum,[n.v.,

buthave seen what is apparently a1764 reprint of die volume, end
this chapter i» W’ 183-201, and isitself dated ITm, which becomesI

On sensitivity, see, for the method
and F. FcnUeber die Empfindlichkeit desof dilution, E. Fischer
zoldt,

Doppelreichmessers,

general von Skrnmlifc, op.

total

bibliography of 186

desMed. Berlin, 7, 1889, 721which is tlio ‘discovery paDie Physiologie des Geruchs,

165-174; Vodorat, 1925, 124-137;
Hermanides, op, cit,, 60-100; H.
Henning, Der Geruch, 1916, 98-158.

be-tween 1887 and 1932 he published
fifty

.

thought aboutdiemakei’s

Fhysbl.

Arch.

1886, 320-357, esp. 322-

Leipzig,phys.-

therefore the date of the classifica-

med. Soz. Erlemgen, 18, 1886, 7-10
(the paper was read in 1884). On
differential sensitivity and Weber’slaw. see Zwaardemaker, Die Plwsla-tion]; A. V. Haller, Elements physio-

Geruchssinnes,

Sitzungsber.

lagle des Geruchs,

K A.

188-194;

logiae, 1763, Vol.
ii,

5, Classes

D.

Lorry,

parties

Sac. ray.

Weber’s law to smell, Atner. J. Psychol, 10, 1808, 82-142; E. ToulouseA.

and N. Vaschide, Note sur un nouveau moyen de verifier la loi deWeber-Fechner sur le rapport de lasensationit

Texcitation

et

sur

le

de cede loi par la mesure de I'odorat au moyen des solu-

v&lfication

tions

ddcimales,

C.

R.

Soc.

Biol

640-642; J. HermaDoer de constanten der inde olfactometrle gebruikeUjke negenF.

I’espril

sect,

Hist
annde 1784(published 1788), 306-318;
volatiles

McC, Gamble. The applicability of1785

V, Bk. XIV,

odomm, pp. 162-188;
Observations
sur
les

Mid.

et odorantes,

Paris,

Be Fourcroy, Mdmoire surrecteurdeBoerrhaave,

Tarome des chimistes trangais, ou
le principe de I’odeur des vAgdtaux,Ann. cm., 26. 1798. 283-250;
Zwaardemaker, op. cit,, 1895, 207238; Henning, Der Geruch, 1916,
51-98. The odores tetri of Linnaeus

Zwaardemaker

Paris, 51, 1899,

andnides.

translated as fool, putrid, repulsloe

standaardgeuren, 1909, 56-^0; M. J.

and virulent. Haller was not so rigid
a classifier as Linnaeus: he named
the pleasant group odores ambro-

Zider and A, H. Holway, Differential
sensitivity
as determined byamountofolfactory

substance,

J.

are

variously

and then shifted to callingthem odores suaveolentes, and mostsioci

SMELL AND TASTE

460
this

persons cite

mote ap-secondpropiiale term. His third group was

simply foetores.

whomentalists

Thetlireeexperi-

Henning's

verifiedprism in its gross relations, thou^
not in detail, arc M. K. Macdonald,
Experimental study of Henning’s

two parents at Cornell who tried tomake dieir little son’s olfactory life
as rich as his visual and auoitoiy
were nevertheless embarrassed when
he begun to sniff at Uieir guests.

Taste

system of olfactory qualities, Amer.
3.

The

Psychol, 33, 1922, 535-553; A.

E. Findley. Furtlier studies ofning’s systemHen-of olfactory qualities,

1924, 436-445; F. L.
25,
Dimmick, Note on Henning’s smell
series, ibid,, 33, 1922, 423-425; The
ibid.,

investigationofolfactory

qualities,

321-335

discussion

of

taste

the

to

handbooks is as follows; A. v. Halhr,ElmeniaBk.

xm, which is Vol. V, 99-124

physiologiae,

1763,

of the Lausanne ed.; Job. Miiller,

Handbuch der Physiologic des MensrAen,

II,

1838, Bk. 5, sect.
Bidder, in R.

4,or

On tile chemistry of smell, sec, in

En^.
ners

cormection with molecular weights,

ohgie.

W. Ramsay, On smell, Natwe, 26,

Vintschgau, in L. Hermann’s flond-187-180; J. Passy, L’odeur
dans la sdrie des alcools, C. R. Soc.

buofi der Physiologic, III, U, 1880,

44, 1892, 447-449; inconnectioa widi the peiiodie table,

Schafer’s

Psi/c/iol Rev,, 34, 1927,

1882,
Biol.

J.

Paris.

B. Hayoraft,

The sense of smell.

Wag-trans.; F.

UmrdwditerbuchIII,

145-224;

i,

J.

1846,

der

Phtjsi-

M.

1-11;

v.

B. Hayoraft, in E. A.

Text-Book of Physiology,n, 1900, 1237-1245; 11, Zwaardemaker, in L. Ashor and K. Spiro,

Proa. toy. Soc, Edlnb,, 14, 1887, 207-

Etgebnisse der Phijsiohgle, 2, 1903,

219 (reprinted
168-178);699-725 (bibliography nf 66 Uiles);G. H. Parker, SmeH, Taste ond Al-

ganiclied Senses <)» the Vertebrates, 1922,

in Brain,

11, 1888,

in oonnecUon widv orcompounds, Henning, Der

110-168

Cemch, 1916, 281-305.
’The handbooks say so much about
smell

as

a

—thus

degenerate sense(bibliographies

I,

organ and our lack of knowledge

shtnes, 1028,

about its laws—tliat these notes
should point out how E. B. Tltcbener took the opposite view, cham-zier,

pioning the sense in lectures and in

1036.

A Be-

Psycholo^,

49-51.

ginner’s

1915,

where he noted that smell "has moresensations,probably,

tlian

all

the

rest of our senses put together," andwhere he told how die Malays track
game by scent, how man can regain an appreciation of this ground'
sense prone on the dining-roomfloor, and how Gallon learned to doby smell. In this connecit must be recalled that thenrlihroetictionthreshold for smell

isastonisliingly

130

Die Physlologle des Geschmach346-520 ( the best andaccounting for the simplicity of tlie

textbook statements, as in hisofE. V. Skamllk, Handbuch
der Physiologic der niederen Sinne,
titles);most detailed account); W. J. Croin Handbook of General Experimental Psychology, 1934, 1005-

The

classical

psychophysiobglcal

studies are H. Odirwall, Untcrsucli-

ungen uber denGeschmackssinn,
Shand. Arch, Physiol, 2, 1891, 169; F. Kiesow, Phil, Stud,, 10, 1894,
329-368, 523-561; 12, 1896, 255278, 484-473,

On the tastedsuds, see C. Lovkn,
Bidrag till Kilnnedomen oiii fungane
smahpapiUer,

1867; Beih'Sge zur
Kenntniss vom Eau der Geschmack-

warzchen der Zunge, Arch.

mikr.

Anaf., 4, 1868, 96-110; G. Schwalbe,

bw. Modem bulture, on the other

Das Epithel derhand, puts a taboo i^on the freeuse of smell in social relations. The

ibid,, 3,

Papillaevallatae,

1867, 504-508; Ueber dio

Ceschmacksorgane der Saugethiere

NOTES461

und des Mcnschen, ibid,, 4, 1S68,
154-187; H. von Wyss, Die heckfdrmigen Orgnno der Zunge, ibid.,

Handbuch der Physiohgie, III, ii,
1880, 145-224; W. Wundt, Grund-

W. Krause, All-ogie, 2 ed., 1880, 1, 382-384 ( sweet,

6,

1870, 237-380;

md mikroscopiiiche Am-

gemelnezUge

der physiologischen

Psychol-salme, allcalino, metal-

sour, bitter,3 ed., 1887, I, 411-418 (sametamie, 1876, 186-183, esp. 189; F.

lic);

Heiderich, Die Zahl und me Dimen-

Cesctunacksknospen der
Papilla vaUata des Menschen in den
versohiedenen Lebensaltem, Nachr.

4 ed., 1893, I, 433441
and metaUio doubtful);
no change in 5 ed. (1902) nor 6
ed. (1910); H. Oehrwall, op. cit.,

Gesell. Wiss. GirtHneen, math.-phus.

1891;

F.

Cl, 1906, 54-64.

1894,

523-561

der

sion

On

tlie

of

distribution

the oral cavity

laste

Insipidity

as mixture ot

cit.;

C. Bell, Anat-

W.

Ueber
den Gescbmackssinn dee Menschen,
Horn.

Oehrwall,[n,v,];

op.

1891, 39-60; L. K. Shore,

A con-

knowledge of taste

tribution to our
I,

cit.,

Physiol,

13,

1892,

191-217; Kiesow, op. cit,, 10, 1894,
333-362; D. P. HSnig, Zur Psyehopbysik des Gescbmaexs.slnnes, PUl
Stud.,

17, 1901, 576-623.

On the classincatlon of tastes, see
J. Bravo, De saponim et adorum difcausis

ferentiis,

elaffectionibus,

Linnd (Linnaeus), Amoenitates academicae, II.
the chapter Sapor medlcamentorum,
dated 1747. [n.v., but pp. 33S-35S
in 2 ed., 1762]; A. v. Haller, Lime
primae physiologiae, 1751, Chap. 14.
[n.v., but pp. 218-224 in the Eng.
1592,

[n.v.];

K.

v.

10,

ci(f.,

four principal

and over the tongue,

but in die 1809 American ed,,sensations,

opp,

(for

1896, 266-270

12,289-201];

1825,

Kiesow.

qualities);omy of the Human Body, HI. 1803
[n.v.,(alkaUnein

see Haller, loo,in,as 1880);(forsweet andW. Sternberg, Beziohungpn
xwlschen dem chemischen Bau siiss
saline);undschmeckenden

bitterstanzenundschmeblten. Arch.

451-483;

1898,

Subzu

Eigenscliaft

ibrer

Physiol,A,

Leipzig,

Sul

Ilerlitzka,“sapore metnllico,” suUa sensazioneeastringenteArch. Fisiol,sulsaporedei

sali.

1908, 217-242;

5,

II.

Henning. Die Qualitiitsreilie des Geschmacks, Z. Psychol, 74, 1916,
203-219, reprinted in Der Geiuch,
1918, 497-513,

The

attempts

todiscoverthechemistry of taste are in J. B. Hay-

On die objective cause of sen-craft,

sation; taste, Proc. roy, Soc. Edinb.,

13,

961-975

1886,

Brain,

1887,

10,

Bichards,(reprinted

in145-183); T,W.

The relation of the tasteof acids to their degree of dissociation. Amer.

chem. J., 20, 1898, 121-

126; L. Kohlenberg,

The action ofphysio-solutions on the sense of taste, Bud.

1763, V, 117. On the elementary qualities, see Zenneck, Die
Geschmackserscheluungen, Repertoritm fiir die Fharmacie, 1839, 65,

Unto. Wis., sci. Ser., 2, 1898, 1-31;

trans.,

1779];

Elementa

logfae,Sternberg, loc.

cit.;

G.

Cohn, Die

organisenen Gcschmacksstode, 1914,[n.v.];

H. Henning, loc. cit.

On

Lehrbuch der
Physiologie des Menschen, 2 ed., II,ii, 1848, 293-306; A.
Stich, Ueber
die Schmeckbarkeit der Case, Ann.

adaptation, see B. Mayer,
Messende Untersuchungen iiber die
Umstimmung des Gesdimackswark-

Chmtti-Kranhefnhnusea

8,133-152. For the history of other

1857, IOS-115, [n.v.]; M. ScUff.
Lefons sur la phystologfe de la di-experimentation on adaptation, see
H. Abrahams, D. Krakauer and K.

gestion, 1867, 1, [n.v.]; Duval, Gout,

M. Dallenbach, Gustatory adapta-

nouveaution tn salt,[n.v];G.

Valentin,

Berlin,de mddidne
el de chirurgie, 16, 1872, 530-552;
M. V. VIntschgau, in L. Hermann’s
dictionnaire

zeugs,

Z.

Sirmesphyslol, 58, 1927,

Amer. j1 Psychol, 49,

1937, 462-469. esp, 462.
On reaction times, see

M.

v

SMELL AND TASTE
Vintscligau, Verauohe uber die Re-

acbonszeit
findung,

einei

Arch

1875, 1-48,

12,

1877, 529-592.

Geschmadtsempges

Vhysiol,

10,

1876, 87-132; 14,

On the Webef fiactton for taste,
see

A H. Ilolway and L. M. Hur-vieh, Differential gustatory sensilivity

to salt,

Amet.

1937, 37-48.

J.

Vsychol, 49,

Chapter 13

TACTUAL SENSIBILITYT

O THE older physiologists touch, the fifth sense, presented
a baffling problem. Even Aristotle recognized its difference

from the other senses, for he assigned to it several sense-

qualities—hard and soft, hot and cold, smooth and rough—making

touch a complex sense or, as some have interpreted him, several
senses.

When E. H. Weber began the experimental investigation oftouch as reported in his De taciu of 1834 and his Der Tastsinn und

das GemeingejM of 1846, he left part of the field quite vague, for,although he was pretty specific about the Tastsinn, he left theGemeingefiM as a classificatory catch-all for everything that did
not fit the Tastsinn—for pain, tidde, shudder, shiver, itch, the muscular sensations, the vasomotor sensations, nausea, thirst and hunger. Nevertheless, even the Tastsinn lacked a convincing analysis

until it yielded to the search for specific nerve energies by Blix andGoldscheider in 1882 to 1885, an advance which enabled von Freyat the end of tire century to establish the modern doctrine of four

qualities(specific energies): pressure,

warmth, cold and pain.

For a while it looked as if Henry Head with his theory of epicritic

and protopathic sensations (1905 et seq.) was going to substitutea new picture of the ‘truth,’ but eventually von Frey prevailed.

Meanwhile the Gemeingefiihl itself was becoming definitized by
the analysis of some of its pails. For instance, Mach, Breuer andCrum Brown in the 1870’s pul the sense of rotation, the “ampullar
sense” of the semicircular canals, on a satisfactory foundation; andGoldscheider in 1889 analyzed the kinesthetic sensations into theconventional triad of muscular, tendinous and articular. Von Freyin 1894 was most instrumental in getting pain out of the Geminge-

fuU. The other organic sensations, like hunger, thirst and nausea,
simply turned into perceptual patterns of pressures and pains in ac-

cordance with the conventions of introspective psyqhology after
1910, or else persisted as functional terms. Cannon’s discovery thatthe stimulus for hunger pangs is the rhythmic contractions of463

4e

TACTUAL SENSIBILITY

464

stomach ( 1912) did much to remove the mystery Irom this visceralsense-datum. The GemeingefuM was, however, never abolished; itmerely disappeared.
Underlying all the history of research on somesthetio sensibility
before 1920 lay the felt need for analysis, Investigators wanted toknow how many senses, or sensations, or specific energies, or qualities there are in the body. Because diflerent criteria of differentia-

tion were used without being distinguished one from Uie other,

the literature is greatly confused; but we ourselves, with die perspective of the present, can easily be clear; there were four ways
in which one sense (or sensation) was distinguished from another,and diey are as follows:(1) Physiological, as

when articular sertsation was given its

special name because the joints were found to be sensitive, or die

ampullar sense because the semicircular canals are sensitive, or
epicritic

and proiopathic sensibiltiy because they are differently

disWbuted afferent systems, or pressure and cold because they are
aroused by different spots on the skin.
(2) Functional, as when temperature was called a sense be-cause the organism can appreciate differences of heat, or hunger

because the organism knows when it needs food, or kinesihesis
because the organism is aware of its own movement and position.
(3) QuoUtatloe, as when temperature was divided into loomthand cold because diose sensations are inb'ospectively different, or
prick was distinguished from ache, or heat from wamth, on introspective grounds.

(4) Perceptual, as when wet is distinguished from dry, or hun-ger from nausea, because they constitute different patterns of simpler qualities.

These criteria constantly out across one another. According to
the doctrine of specific nerve energies, a qualitative difference al-ways means a physiological difference, a difference in the specificfibers excited, Later the theory of evolution mademen look for afunctional specificity whenever they found a separate neural sys-tem, since a system to have evolved must have a use, and—con-versely but less logically—to look for a new system when theyfound a new function. In the present century it has become clearthat different functions may be carried by different patterns of thesame qualities; nevertheless Gestalt psychology has in general refused to sanction such analyses, tending thus to identify quality

TACTUAL DIFFERENTIATION

465

with function. All these diflerences we must keep in mind as we
trace the history.

Tactual Differentiation
Since Aristotle had left the question of die eomplexity of touch

unsetded, the ancients and their successors tended to make lists oftactual sense-qualities. All told, there was considerable agreement

among these lists. That touch is adequate to the perception oflight and heavy, hot and cold, wet and dry, nearly all the classifiers agreed. Some added tickle or thrill; others pain; still others theantithetical pair, pleasure-pain. In addition, they mentioned the

deep-seated qualities that Weber put in the Gemdngefuhl—hun-

ger and thirst, which almost no one forgot, and other sense-qualities
like shudder, suffocation,and sexual and muscular sensibility.

These early classifications are not important, however, except as
they gave notice of the existence of a problem.

We may pass at once

to the much more recent Weber.

In 1834 Ernst Heinrich Weber (1795-1878) published a Latinmonograph on the pulse, absorption, hearing and touch, which wasfor the most part a discussion of experiments upon touch; De subtilitate tactus.

He divided his exposition into De loco, De pondere—place, wei^t and heat. This work exerted little

and De calore

Influence, but in 1848 he contnbuted to Wagner’s Handwbrterbuch

der Physiologie his soon-to-be-famous Der Tostsim und dasGemeingefuhl, which echoed the original work in subdividing theTastsim into an Ortsinn, a Druchim and a Temperaiursim. In
this analysis

Weber was not using the word Sinn in a technicalphysiological manner; he was merely listing the functional capacities of the skin for sensory discrimination, saying Sinn as

we might

speak of a sense of proportion or a sense of deooium. By the Ortsinn he meant the capacity of the sldn to distinguish the localizations of the two points in the compass test; for he intended in thisanalysis to show only that touches on the skin can be distinguished

as to their pressures, their temperatures and their positions. Sincesuch a statement is nothing more than saying that cobis can bediscriminated in respect of saturation, brightness and extension,
it isplain that Weber was distinguishing three attributes, rather

than three separate senses, although the formal problem of attributes did not exist in those days. Actually Weber was at pains

4fi6

TACTUAL SENSIBILITY

not to separate these functions, but to show that they go together

and that they are interdependent He appealed to their concomitances, pointing out that all three are missing together in the tissueof wounds and in the alimentary canal. By his often-cited experi-

ment of the silver Thder, he demonstrated that temperature andpressure are interrelated. (A Thaler is a German coin intermediate
in size between the American dollar and half-dollar.)

A cold coin,placed upon the forehead of a recumbent subject, feels heavier
than a warm coin; in fact, it feels heavier than two warm coins,when one warm coin is stacked upon the other. If temperature affects perceived pressure, then the 'senses,’ Weber argued, cannot
be separate. Nor can the ‘place sense’ be regarded as independent,
since there cannot be a localization unless there is something tolocalize.

In the next thhty-flve years only slowly did opinion shift toward

the belief that temperature and pressure are independent senses.

Wunderli in 1860 argued for identity, noting that a tuft of cottonwool brought in contact with tlie sldn and a warm object broughtnear the skin cannot be consistently distinguished. Szabadfbldi too
in 1805 showed that a warm object, alUtough it seems lifter thana cold, also appears heavier than an object of neutral temperature.

There were, on the other hand, at this time some findings thatpressure and temperature do not always vary together in pathological conditions, and the histologists, using their new techniques

to hunt for end-organs in the skin, began to find enough organs tomake it seem diat the skin might have more then one sense resident in it. Thus, after Funke and Hering in 1880 agreed that thepressure sense and the temperature sense are really separate,

Hering undertook to build a theory of the temperature sense analogous to his theory of color vision. Pbenomenologist that he was,he noted that cold and warmth are qualitatively dfflerent (likeblue and yellow), that, since adaptation to one means sensitization
to the other, drey seem to represent antagonistic processes, thatthey are separated by a physiological zero {NuUpunhtemperatur)

which varies with the adaptation, and that an object of medium
temperature feels warm after cold stimulation, cold after warm.
This last fact John Locke had remarked, but Hering’s theory complicated the tactual sense further by making warmtii and cold de-pendent upon different, though interrelated, physiological proo-SENSORY SPOTS

467

Meanwhile pain had, for the most part, been left in flie Gemeingefuhl. Such a classification was consistent with the view ofpain as a form of common sensibility and with the beUet that all
intense stimuli are painful. Certainly very bright lights, very loudsounds, very strong pressures, great heat and great cold are all
painful. Weber had even worked out the thermal thresholds for

pain, for it was obvious to him that the GemeingefuM is not ex-

cluded from the skin. Johannes Muller’s theory of specific nerve
energies was, however, opposed to this intensive theory of pain,
since on that theory every nerve must have its own and only its own
quality. He had been able to cite evidence to show that direct surgical stimulation of the optic nerve yields a flash of light but nopain. In 1858, moreover, Schiff came out against the intensive the-ory on the ground of experiments and the study of many abnormalcases, whidi led him to localize pain and touch separately in the

spinal cord. Incisions in the gray matter of the cord sometimes interfered, he found, with the conduction of pain but not of touch,whereas division of some of the tracts in the white matter interfered with touch but not pain. Nevertheless, Erb in 1874 declared
for the intensive theory of pain, although Funke in 1880 made theopposite decision. Herzen in 1885 noted that, when a cutaneous

nerve is anesthetized by pressure block, sensibility to cold andtouch is lost first, then pain, then heat, and that the return is in thereverse order after the block is removed. Altogether there was,when Blix began his experiments on cutaneous specific nerve energies in 1882, no certainty about pain as an independent sense; theseparation of pressure and temperature, however, though not of

warmth and cold, was generally accepted.
The independent discovery of sensory spots in the 1880’s, firstby Blix in Sweden (1882), then by Goldscheider in Germany(1884), then by Donaldson in America (1885), came about be-cause this next step was so obvious. Helmholtz had made the doctrine of specific nerve energies basic to sensory psychology. Thatmeant that the number of cutaneous qualities must be the numberof kinds of nerves to be found in the skin. In investigation small
stimuli were called for. They had not been used before except inWeber’s experiments on localization. Blix, trying faradic stimulation of the skin (a single electrode from an induction coil), foundseparate spots that responded independently widi the qualities ofpressure, cold, warmth and pain. That seemed to indicate four

TACTUAL SENSIBILITY
specific energies. Then Blix rigged up an apparatus with a hollow

conical metal point through which warm or cold water could hepassed, and used this stimulus to map the cold spots and the warm
spots.

When he got them in diEerent places, the cold more numer-

ous than the warm, he knew that he had definitely separated thetemperature sense into two.
Goldscheider. who read the German translation of Blix’s Swedish

paper when he was about to publish his own, used cork points andneedles for pressure, needles for pain, drops of ether from a bmsh
or caplllaiy tube for cold, and warmed conical brass cylinders forwarmth. He mapped the skin for spots. What he found was separate warm spots, cold spots

and pressure spots—aU very muchsmallei' and more numerous than those charted by any other inves-tigators who followed him.

He also, in his early work, found pain

spots, very much more numerous and closer together than the other'spots,

but that discovery he took back later. He described theaction of the pressure spots precisely.

A light pressure with a cork

point on a pressure spot gives a quality of “lively contact”; aheavier pressure gives "granular pressure” as if a grain were forced
into the skin;a strong pressure, a ‘Tjruising, pressing pain.” A

needle on a pressure spot gives a “lively contact" for light pressure

and an intense “neuralgic pain” for strong pressure, On a pain spot
a needle gives a “fine, sticking pain” or, at greater pressure, a“lancing pain.” In between the spots the cork points give dull contacts and the needles dull pricks. Goldscheider did not, therefore,claim that the skin is completely anesthetic between the spots, northat pressure spots are insensitive to pain when the stimulus isstrong.

Blix and Goldscheider may thus be said to have established pressure. cold and warmth as three separate qualities, or specific energies, as they were called then. The separation of the spots implied

the existence of independent nerve endings beneath them. Bothmen also presented good evidence for pain as a fourth sensory system-evidence which, however, was less convincing because the‘spots’ were so numerous and dose together that it was practically

impossible to find pressure, cold or warm spots which were analgesic. Both eventually, reversing their original positions, held thatpain is eammBn sensibility. Later, in the 1890’s, when von Frey wasarguing that pain is a fourth cutaneous modality, Goldscheider
vigorously supported the opposing intensive theory. He showed.

VON FREY’S RESEARCHES
among otlier things, that stimuli, separately adequate only to pressure, will, when given at the right frequency, summate to give pain.

Thus the intensive theory of pain was sometimes called a summation theory. Goldscheider believed that pain has no separate receptors in the shin, but that pressure or thermal excitations

may sum-

mate so as to excite, in addition to their proper ti-aots, the pain
tract in the spinal cord, and thus, presumably, a pain center in thebrain. This scheme makes of pain a Mitempfindung, although actually giving it a specific energy within the central nervous system.

What came later to be regarded as the classical theory of theskin was put forth by Max von Frey ( 1852-1932) in four papers
in 1894-1896. Von Frey was clear, definite, assured, and,what ismore, he ofiered a doctrine that was congenial to current belief
in the specific energies of nerves. This in itself was an accomplish-

ment. His contributions were as follows. (1) He made the argu-

ment for pain as a fourth separate modality in the skin (1894),
demcnsti-ating the existence of pain spots, much more numerous

than the other three kinds of spots and not necessarily coincident
with them. Between the spots he found regions analgesic to that
intensity of the stimulus which was adequate to the spots. (2)He

discovered paradoxical cold (1895), the response of a cold spot,with the cold quality, to a warm stimulus in the region of 45° to
50° C,, that is to say, far above the threshold for warmth on thewarm spots and a little below the threshold for thermal pain. Later
Alrutz’s doctrine of the heat quality was based upon this fact, but

at the time the discovery served only to reenforce the theory of

cutaneous specific energies and the separation of warmth and coldas

two separate modalities. (3) He found for each of the fourmodalities a specific end-organ (1895): for pain the free endings

between the epithelial cells, for cold the Krause bulbs just beneaththe skin, for warmdi the Ruffini endings deeper down, for pressure
the free-endings around the hair-foUides or, in the palms and soles

where there are no hairs, the Meissner corpuscles. This correlation,although it was not collect, was accepted for many years largely

because of the weight of von Frey’s authority. At the timeitseemed to settle the question about four modalities: if there are
four kinds of spots and each has its peculiar organ, what more can

one ask? (4) Finally, he discovered (1896) that themature of thestimulus to pressure is not simply the force of the stimulus, nor theforce per unit area, but the tension, the force per linear unit of theTACTUAL SENSIBILITY

470

depressed area on the skin. On that finding he based his tension
theory of cutaneous pressure. To the question of heat and to thesignificance of the pressure stimulus

we must refer again in theproper places, but it is right that we should here see von Frey’s important contribution as a whole.

Von Frey’s argument about the raitaneous end-organs was mostly
Let us see how he determined the organs for the four

indirect.

modalities.

(1)

Most of his pressure spots, he found, lay over hair-folhcles,that is to say, to 'windward’ of the hair as it emerges from the skin.

In one good correlation he found 73 spots for 70 hairs; in anotherpoor one 70 spots for 96 hairs. Naturally he concluded tliat the freeendings at the foUicle are the receptors. It must be observed, however, that aU the spot-finders ignored those “dull, contentless contacts," vaguely sensed between the definite positive spots, and thatGoldscheider, even when he excluded these intermediates fromconsideration, got in one case 66 spots for 36 hairs and in another(his worst correlation) 147 spots for 15 hairs. In the palms and thesoles, where there are no hairs but where there are Meissner cor-puscles, von Frey chose the latter as proper to pressure. They arevery numerous and spatial discrimination is quite fine in theseregions. Of odier evidence he had none.

(2) Because no other endings are numorous enough to accountfor the great frequency of pain spots, von Frey assigned the freeendings between the cells of the epidermis to pain. He was thus
requited to explain why pressure should be mote easily elicitedthan pain when the organs for pain lie nearer the surface than thosefor pressure; but he met this objection by noting that the pressureorgans, lying in the soft tissue underneath the hard epidermis,
would be affected first through the epidermis which would bepressed down as a whole, whereas organs in between the hard epi-

dermal cells would require a more violent stimulus to crush thecells or penetrate between them.

(8 )The Krause bulbs he assigned to cold because they occur inthe conjunctiva and the glans penis which are insensitive to cutane-ous pressure, and in the outer edge of the cornea which is insensitive to warmth. Von Frey himself found one Krause bulb in ordi-

nary skin, bufethere is no evidence that they are nearly so numerous
as cold spots.

(4) Finally, he gave to warmth die Rufflni endings, which are

HEAD’S THEORY

471

known to lie in the finger pulp and one of which he found in ordinary skin. Although the fact that they are located deeper in the skinthan the Krause bulbs corresponds with the fact that the reaction
tune for warmth is longer than for cold, in general von Frey was

doing little more here than delegating the last unassigned organ tothe last available sense.

A strange thing about this theory of von Frey’s is that it wasformulated by him—and ultimately accepted into textbook psy-chology—without any reference to the earlier direct experimentsof Goldscheider in 1886, which should have been known to vonFrey. The fact is that both Donaldson in 1885 and then Goldschei-

der had excised cold spots and warm spots, yet had been unable

by histological examination to locate any receptors but free endings. Inasmuch as these findings were confirmed later by Haggqvist(1913), Dallenbaoh (1927)

and Pendleton (1928), the wholecorrelation is now discredited after many years of service.

Von Frey’s division of cutaneous sensibility into four modalities
was challenged only once—by Hemy Head, the famous English
neurologist, who came at the problem of differentiation from theclinical side.

He had observed that, after an injury to a cutaneous

nerve, there are generally, besides a region of complete anesthesia, boundary regions in which sensitivity to light pressure isabohshed, sensitivity to pain is increased, localization is disturbed,

and accurate spatial discrimination is lost. He also found that thereturn of sensibUity to the anesthetic skin, when an injured nerve isregenerating, passes through this same state of crude, primitive

sensory response, a state which he later named ‘protopathic sensibility.

Since clinical patients make poor observers and disappear

from experiments as soon as they are nearly well, he decided to
substitnte the experimental for the clinical method. Severing anerve in bis own arm, he studied the state of cutaneous sensibility
after the section and during the regeneration of the nerve. With
him were associated Sherren, the surgeon, and Rivers, the psychologist. They published their first report in 1905 and a full accountin 1908.

Head’s tlieory—it is impossible at first to separate the facts fromthe theory—was that three differently distributed neural systems
are involved in the normal stimulation of the body’s surface. (1)Deep sensibility lies in the tissues immediately underneath thesldn, is not disturbed by the section of a cutaneous nerve, and funo-

TACTUAL SENSIBILITY

472

tions surprisingly well through the sldn for dull pressure and dull

pain. Not only will a couple of grams pressure on the skin arouse

deep sensibility, but the capacity to localize a single point is about
as great for deep sensibility alone as when cutaneous sensibility isadded. (2) FrotopatMc sensibility is a primitive cutaneous system,

crude and strong in widely dispersed action, overlapping the regions supplied by adjacent nerves, and first to return when a sev-

ered nerve regenerates.

(3) Epkfitic sensibility, rarely foundalone, is superimposed upon protopathic sensibiUfy in normal sen-Fio. 78.

Pbotofatbio akd EKCEmo Sembiwuw in IIenrv Head’s Asm
IN Maz, 1903

One month after the ladiol and external cutaneous nerves bad been diA = anesthesia; P = protopathic sensibility; E = epioritio senslbibty;
Normal sensibility, P -p E lies outside die enclos^ areas. Deep sensibility
was not disturbed. The light line is inner boundary of epicritic sensibility, thevided.

heavy line the inner boundary of protopathic sensibility. Of. Table IX.

sibility

and is a later and more finely discriminatory capacity,

mediating the qualities of light pressure and the lesser degrees ofwarmth and cold but not pain, inhibiting the more violent reactionsof the protopathic system, and returning in regeneration after the
protopathic. Certain primitive surfaces, Uko the glans penis, show

only protopathic sensibility. Ordinarily, after a nerve has been injured or severed, there results on the skin a central area of cutaneous anesthesia, where there is only deep sensibility, surrounded byan irregular region of protopathic sensibility, in turn surrounded

by a normal region. As sensitivity recovers, both regions shrink, theprotopathic returning centripetally in the anesthetic region, andnormality
to the—due presumably

to the addition of epicritic sensibility

protopathio-foUowing centripetally. The boundaries are

PROTOPATHIC AND EPICRITIC SENSIBILITY
irregular.

473

Head claimed to have found on his own arm one area

where epicritio sensibility existed without protopathic—a situation

which, however, has not been duplicated in later experiments(Fig. 78, area E.). The list of functions for the two systems, muchgreater than this paragraph slates, is given in Table IX. The distribution of sensitivity in Head's arm one month after the sectionof his nerves is shown in Fig. 78.

Table K. Head’s Thbbe Systems or Tactual Sensibiuty (1905)
Frotopathlc and epicritic sensibility are cutaneous; deep sensibility is subcutaneous.

Deep
1.

Dull pres-

1.

sure.

2.

Dull pein
fnsm
heavy

EplcHMc

Protopathic

Hair

a

sensibility,

tin-

1.

BecogDilion of Ught touch

gling or formication fromoverstimulating the hain.

shaved skin.

by pricking, burn-2. Pain,ing,

freezing,S.

hahlessorskin

No pain of any kind.

electric

stimulation, or plucking

stimuli.

hairs.
3.

Heal from temperatures

S.

above about 45”C.

Discrimination of warmthfor

optemperatures

toabout 40°C.
4.

Cold from temperatures
below about 20*G.

4.

Discrimination

of

cold

for temperatures down toabout 25‘C.
3.

Localiza-

5.

No thermal adaptation.

5.

Thermal adaptation.

8.

Localization

6.

Cutaneous localization ac-

sensations radiate wMely,tion of sin-

gle

point

are verycurate,diffuse or are

remotely referred.

accuratetoperverted;% inch7.

Discrimination

of

two

points as two.
7. All thresholds high.
8.

8. Partially

All sensations intense.

reaction

inhibits

(both

over-

intensityand bad localizatian) of
protopathic system.
9. Allsensations disagree*able.

10. Sensory spots have pane*tifoimsldn.

distributionin9.

Warmth and

cold

not

puncUfaimly distribatedin skin, and pressure puncUfomi only when associated with hairs.

A careful examination of Table IX raises about Head’s theory
certain questions that cannot be answered. Protopathic “hair sensibility” seems to be a kind of pressure sense, although the theory

asserts that the pressure quality is only epicritio. It is hqt clear how

474
in areaTACTUAL SENSIBILITY
E of Head’s arm(

Fig. 78) there could have been sensibility

to mild temperatures and insensibility to extreme temperatures. If

a point can be localized in deep sensibility to half an inch, oarmot

two points, an inch and a half apart, be discriminated as two without epicritio sensibility? (A later experiment showed that theycan.) Yet such matters are trivial. In the main Head’s discovery
proved correct: there is a genetic course of returning sensibility
after nerve injury. The extreme stimuli, thermal and algesic, areeffective first, when sensation is intense, unpleasant and badly lo-

calized; mild stimuli become effective later as sensitivity improves,

as intensity and unpleasantness diminish, and as localization be-comes accurate. So far as these facts go, there need never havebeen controversy about Head’s theory.

There was, however, controversy. The theory was one put forth

by a neurologist without regard to von Frey’s theory of the fourmodalities already accepted by the psychologists. With warmthand cold each divided between the two systems, it cut across theconventional view.

The textbook writers did not know which

theory to accept, whether von Frey’s four afferent systems or

Head’s two. Sometimes they printed both without spthesis.

In 1909 Ti'otter and Davies, two British surgeons, divided sevendifferent nerves in one or the other of themselves and studied thereturn of sensibility during the period of regeneration. As far as
the general statement of facts given above goes, they confirmed

Head Since, however, tliey did not find the different areas sharply
bounded, they preferred not to accept the two-system classification.
In 1910 the audior of the present book published an account of the
return of sensibility in his own arm after a small cutaneous nerve

had been divided for experimental purposes. Undertaking this experiment for the purpose of resolving the seeming incompatibility

between von Frey’s and Head’s views, he too confirmed the latter asto the general facts, but faffed to get sharp boundaries between theregions, rejecting, on this account, the concepts of protopathic andepicritic sensibility as not useful for explaining the results. Headcomplained that this experiment, involving the section of too small
a nerve, was therefore only a “miniature experiment”; yet there isnothing in Head’s theory that ought not to be demonstrable within

a single square centimeter. Alffiough there have been other experiments since, the fact seems to be that Head’s theory has gradualty dropped out of the textbooks while

von Frey’s has stayed.

'

PROTOPATHIC AND EPICRITIC SENSIBILITY

475

There has never been a generally accepted synthesis of the twoviews, but the basic facts, common to aU experiments, appear to be
admitted by everyone. All four modalities return during regeneration gradually and continuously; pain tends to be early and pres-sure late; and in the initial stages there is exaggerated sensory re-sponse which is later diminished (inhibited?). The present author
suggested that the fact of diminished sensitivity around an anesthetic region after nerve-division shows that there is considerable

overlap of nerve supply from different trunks, that most sensory
spots are multiply innervated, and that a second fiber growing intoa spot may have an inhibitory effect upon a first which is already—thus explaining what

functioning thereisperhaps Head’s mostimportant finding, the inhibitory Sect of the ‘epieritic’ upon the‘protopathic.’

Nobody, however, has taken this suggestion very

seriously.

The result of the century of cutaneous psychology since Weberis,therefore, that we have settled down to a belief in four modali-ties,

even though we cannot distinguish four kinds of nerve end-

ings. Each of these senses is distributed in a punctiform manner inthe sldn; there must be receptors and the receptors, being nerve
endings, cannot be continuous sensitive films. The spots are thepoints where stimulation is most effective. The more intense thestimulus, the larger the spots, because they can be activated at agreater distance by a strong stimulus. Although the order of nu-

merousness of the spots tends, in general, to be pain, pressure, cold,

warmth, no such slatement can be exact, Inasmuch as more effective stimuli create larger and fewer spots. In this sense von Frey’s

notion that a cold spot cannot lie within a warm spot is not correct;
albeit we must remember that von Frey was thi^ing only of thedear strong sensations which come with their characteristio Uerhmale, not of all the vague sensory ghosts that can be aroused in
the less effective regions between tiie spots.

The Two-Point Limen
For Weber the Ortsim was important because he had a methodof measuring it and the measurements seemed to him to have direct physiological meaning. His device was, of course, the compass
test, the determination of the distance apart on the sldn at which

two points will be felt as two. Such a method measured, he thou^t,

TACTUAL SENSIBILITY

476

the separation of end-arborizations of the cutaneous nerves. This

determination (1834, 1846) of what was called later the two-point

limen or the limm of dual impression he supplemented in 1852 by
his “second method” for measuring the perception of tactual space,the determination of the enor of localization when the subject
tries accurately to indicate the location of a sin^e cutaneous point

which has been touched. While this second method has been called

Fro. 79,

Webbu’s Sensoby Ciboles ( 1852)

Wehei’s pictures of sensory 'elides' as end-zones of oeive fibers in thesensory drclcs. A
poor disnerve fibers, a', b', o', d'skin, a, b, 0 , dcrimination. B==== good dlscrlmbialion. C, D = transverse disorimination bet-

ter than longitudinal, as in forearm.

localization, it is plain that the first method, ina more precise

sense, is also a bcalization. Any localization has to be made withrespect to some frame of refei'ence; in the compass test one per-ceived point becomes the reference for the other, since the subject

has to say whether the two are the same or different. Weber in1846 made the limen of dual impression a measure of the Ortsinn,
but later this limen was said by him and others to measure theRaumsinn, whereas the error of localization was then regarded as
an index of the Ortsinn, From this early start, there grew up quitea large literature on each of these determinations, and in general

the two measures were kept distinct—

as they

were by Head

(1905), who assigned the capacity for localization to deep sensibility, but the power to discriminate two points to epicritio sensi-

b% (Table IX).

It was Webjer’s belief that die skin is divided into sensory circles,a mosaic of small regions each of which represents die terminationof a nerve fiber. Weber’s picture of these ‘circles’ as hexagons is re-TWO-POINT LIMEN

477

produced in Fig. 79, which also shows how they might be shaped

when the threshold of duality is greater in one direction than theother. The threshold, according to Weber,measures the average

distance between two circles next but one to each other, If the twopoints of the compass fall in the same circle, one feels, he thought,a single impression; if they fall in adjacent circles, the impression isstill single,

though elongated; let them skip a circle, however, andthen two separate points are perceived.

Although Weber discussed the successive simulation of points,
the first systematic investigation of this sort was made by Czermak
in 1855.

He got smaller thresholds than Weber’s, but then one

might expect such a difference; adjacent circles in successive stimulation, being discrete in time, would not fuse into a simple impres-sion. Czermak was primarily concerned, however, with the ques-tion of whether the sensory circles actually correspond to different

nerve endings, as Weber tiiought. First citing a current neurological investigation to show that the total number of nerve fibers does

not increase as the organism grows larger, he tlien went on todemonstrate that the space threshold for boys is less than for men.

The implication he drew was that, since the number of nerve fibers
is constant, the sensory circles and the limen ot duality grow withthe organism.

Weber noted that longitudinal and transverse thresholds may bedifferent in size (Fig. 79,
this fact,

C and D), and Vierordt in 1869 stressed

presenting the ratios, which ranged from 1.0 to nearly

4.0 in various bodily regions. Discrimination across the arm is, forinstance, much more accurate than discrimination up and down,a fact which Weber took as support for his simple physiologicalhypothesis.

On the other hand, Vierordt was able in 1869 and 1870 to formulate his law of mobility as a condition for the threshold. The thi'esh-old on the aim decreases continuously, he found, from the shoulder
to the finger tip; in any single rigid member, like the upper arm or

the forearm, the decrease is proportional to the distance from thenext proximal joint, but the rate of decrease— different in different

members— changes

at each joint Fig. 80 shows this relationship.

For each member of a limb the threshold can be thought of as thesum of a constant, which is greater the more proximSl the member,and a variable, which increases with the proximalily of position
within the member. The significance of Vierordt’s law is that sen-

478

TACTUAL SENSIBILITY

Fig. 80. Verordi’s

Law of MoBiirry (1870)

The size of the two-point thieshold (in per cent of die threshold at theshoulder) plotted against the position on tie arm (in per cent of the dis-

tance frata shoulder to £nger tip). Averages of longitudinal and transveisethresholds, and of dorsal and vdai thresholds. Plotted from VieiordFs data

(and similar to a figure of Henri’s). The tliresbold at any point can be regarded as the sum of a constant for the particnlar member (the rectangle
in the diagram for the upper arm, forearm, hand or finger)

and a variable

proportional to the distance of the position from the neatest proximal joint(triangle

above the rectangle). The solid lines are drawn to give the best

approximation to the theory. Vierordt himself did not construct this figure.

sitivify increases with,mobill^—continuously toward the more mo-bile end of a member, and abruptly where a joint increases mobility. There is a suggestion in thislaw that the tlueshold may depend
upon use and not merely upon the distribution of nerve-endings.

PARADOXICAL TWOS

479

The discovery of pressure spots in 1882 immediately raised thequestion whether these spots correspond to Weber’s sensory circles and whether every pair of spots can therefore be discriminatedspatially. Goldscheidei',

who found many more spots than did his

contemporaries, supported his figures in 1885 by finding also muchsmaller space thresholds than the others. Von Frey and Metzner in
1902, using successive stimulation as

Czermak had done earlier

for the same purpose, reported that, under optimal conditions ofobservation and optimal time between stimulations, they could

always get a spatial discrimination of every pressure spot fromevery

otlier.

These results, therefore, favored Weber’s originalphysiological llieory.

The situation was, however, complex. Henri, in his classical
Veher die 'Raumwahrnehnungen des Tastsinnes in 1898, was able
to add to the simple anatomical basis for the thresholds all the evi-

dence for the effect of practice and fatigue. It was difficult at thattime to say whether the threshold was dependent more upon innate

anatomy or upon learning.

The complexity of the physiological basis of the threshold was
also made apparent by the discovery of Veslrfehler or paradoxicaljudgments. In the earlier psychophysics it was usual to include
control stimulations called Vexiroermche: in the compass test, forinstance, single stimulations were mixed in with the double as acheck on the objectivity of the observer and with the expectationthat a good observer would never call a single point “two." Kotten-

kamp and Ullrich, pupils of Vierordt, found, however, in 1870 thata single point was often reported as two. Camerer, applying themethod of right and wrong cases in this field in 1883, discoveredthat these VexirfeUer can be so numerous as to interfere with thecomputation of a limen. For instance, averaging the results of fiveobservers, he found IS per cent of the single points judged “two,”and 10 per cent judged as “more than one." Henri and Tawney
made a special study of these judgments in 1895. There are, according to their observations, diflerenoes in the frequency of the paradoxical twos in different persons as well as on different parts of the

body for the same persons; in addition, the paradoxical twos are
more often perceived as separated in the longitudinal direction on—

the forearm than in the transverse direction

all data which sug-gest that the basis for the judgment may lie in the anatomical dis-tribution of the nerve endings. But they also found that expectation

TACTTUAL SENSIBILITY
and fatigue increase the number of Vexirfehler—{acts which indicate a judgmental origin. The paradoxical twos, especially numerous for single points which are not mixed in with double stimulations,decrease when wide separations of the double stimuh areused along with the single points. Contrast, in other words, reduces
the Vedrfehl&r. Henri summarized the whole matter in 1898 andFoucault again in 1910, but there was no decision on the issue ofanatomy vs. judgment.
In 1918 ICinoaid reported a case in which the frequencies of twosin the psychometric function were as follows;

2 mm.

8 mm.

14 mm.

20 mm.

26 mm.

57%

47%

65%

72%

94%

The Vexirfehler make the twos more numerous at 2 mm. than at
8 mm. The statistical limen for this function, the separation whichshould give one and two equally often, is computed as 4.08 mm.,but it is obvious that there are really two Hmens, one above and theother below 8 mm. The present author suggested in 1916 that theparadoxical twos may actually represent the multiple innervationof the spots in the skin, and drat the report “two" for multiple in-nervation may become actual only when favored by attention orother judgmental facilitation. Certainly Head’s work indicated theoccurrence of many Vexirfehler under the conditions of sensibility

which he called ‘protopathic.’That something more than anatomy affects the threshold wasclearly indicated by the effects of practice.

The history of thatproblem goes all the way back to A. W. Volkmann who, after working with Fechner and himself as observers, published in 1858 thedeterminations of their thresholds for the past two years. There

was a striking decrease in the threshold distance, which they took
tobe the consequence of practice. Camerer in 1881 reported asimilar result for two children whose thresholds had been deter-

mined on various occasions from 1875 to 1880. In spite of the factthat both children were growing bigger and that the threshold, according to Czermak, grows up with the child, their thresholds decreased in five years to a little less than three-fourths the originalvalue. The most remarkable functions were, however, pubhsbed

by Tawney in,1897. Testing observers on each of twenty successivedays, he got decreases in Ae threshold as great as from 50 mm. to
0.6 mm.l Some of his praotioe curves were quite smooth and regu-

JUDGMENT OF DUALITY
lar.

481

Although these results oast great doubt upon Weber’s theory,

Henri in 1898 noted that practice must affect the interpretation of

any sensory disparity, and that anatomical differentiation would
stiU represent the limit beyond which practicecannot go.

About this same time Griesbach (1895) and Vanned (1890) discovered that mental fatigue increases the threshold. It was theiridea to test school cMdren throughout the school day. Vanned

found discrimination diminishing from 8 a.m. to 5 p.m.; Griesbachfound it improving from 7 a.m. to 10 a.m. and then diminishing to
2 p.M. Griesbach’s interpretation was like Henris. Drawing a picture of overlapping end-arborizations of the cutaneous nerves, hesuggested that a certain amount of resulting confusion tends toincrease the threshold unlessmaximal attention is available fordiscrimination. For a while after 1900, therefore,

what Weberthought was a test of differentiation of nerve endings in the skin

was used as a practical test of fatigue in school children.
Comparable with these finding for practice and fatigue was
McDougall’s discovery (1903) that the Murray Island savages of
Torres Straits had an average threshold of 19.8 mm. (range, 2-40mm. ), whereas the Englishmen whom he tested when he got backto England had an average threshold of 44.6 mm. (range, 10-90mm, ) It looked as if savages were more practiced, or less fatigued,,or at any rate keener than civilized men.

There was, however, thus far no good explanation of how judgmental factors enter in to affect these sensory discriminations; justsuch an insight was, nevertheless, to attend an understanding of
dre categories and criteria of this judgment. Weber originally noted
three perceptual patterns that come from two stimulating points:

one (single sensory circle), extended (two adjacent circles) andtwo (two separated droles). Kottenkamp and Ullrich (1870) recorded essentially the same three categories: point, elongated,double. Camerer (1883) used four categories: one, undecided,

more than one, two. Foucault (1910) was actually able to distinguish eight serial perceptual patterns: (1) a precise point, (2) acirclewith a distinct contour, (3) an extended circle without adefinite contour, (4)an elongated rectangle, oval or line, (5) anelongated area with two centers of pressure within it, (6) two

overlapping areas of pressure, (7) two circles tangent, (8) twocircles with empty space between them. Finally Gates (1915)
chose five categories, point, ciide, line, dumb-bell, two, added the

TACTUAL SENSIBILITY

482

four intermediate doubtful categories(like point-or-ciTcle)

tomake nine in all, and then determined the eigjit tliresholds that
separate these nine categories.

What does 4is situation mean? It means that tiiere is a series ofdifferentiated perceptual patterns, that the criterion for two musthe placed at some critical point in the series, and that the meaningofie judgment two is indeterminate unless the criterion has been

established, Titchener was the first ( 1916 ) to see this point. Against

McDougall’s interpretation, he argued that the Murray Islanders,
trying to do well before the white men, would naturally select somecategory low in the series as the definition of two, a line or an ocal,

whereas the cultivated Englishmen, trying to be accurate and logical, would call one everything below two impressions with a space

between them. Titchener was at pains to show that accurate spatial

discriminations of subliminal separations can be made widi

effort and attention, if subliminal means anything below the limen

for two-with-a-space-betweon-them.

Later FriedUne, Titchener’s student, published in 1918 a systematic investigation of spatial disciimination of two-point stimulation below the normal threshold

On a part of the foreaim, where

die usual limen is about 20 mm., she found that observers can distinguish, often with 100 per cent accuracy,

no separation from

5 mm., 2 from 7 mm., 5 from 10 mm., and even sometimes no separation from 2 mm., and 2 from 5 mm. She found further that forsuch discriminations these observers required strong motivationand full attention, since fatigue or distraction readily reduced theirperformance from perfection to randomness. Thus she was in aposition to explain the effects of practice and fatigue. Practice iseffective when the observer learns to choose a finer but more diffi-

cult criterion in the sensory seiies. The finer criteria are, however,more difficult to use, because tiiey are not so clearly delimited as
the gross criterion. Hence fatigue, working against accurate perception, sends the Hmen up. The Murray Islanders were not tired

nor distracted, and they tried hard.

Except perhaps to indicate that the sensory circles are not clear
cut, these results do not actually contradict Weber’s hypothesis.

Presumably the distribution of sensory ‘spots’ is complicated byoverlapping ipnervation. Nevertheless, the existence of discrete
receptors

must constitute the basic fact which establishes the

ERROR OF LOCALIZATION

483

sensory series, whereas the judgmental factors must just as surely

be regarded as additional determinants.

The Error of Localization

We must turn now to the second method of Weber (1852), thedetermination of the error of tactual localization, In this experi-

ment the observer closed his eyes; the experimenter touched hisskin with a blunt point dipped in powdered charcoal so that itmarked the spot on the skin; then the observer tried to touch thesame place with another pointer; and the experimenter measured
the distance from the marked spot to its localization. This method,

devised in the same year that Lotze formulated his theory of local
signs, was destined to seem a truer form of localization than the

two-point discrimination; it measures localization with respect tothe body as a frame of reference, whereas the first method measures only the localization of one point with respect to the other.

We had better analyze the problem first in order to examine its
We have here what in modern terms, a stim-

history afterward.

is,ulus-response situation, a disoriminatoiy reaction; the subject, after

being stimulated, designates the locus of the stimulation. Many
forms of localizing reaction can be used. (1) Kinesthesis (K), as

when the subject brings the pointer in his hand to what he thinks
is the correct position and docs not move it after it has touched theskin, or else localizes by pointing at the spot on the sldn through a

glass plate. (2) Touch ( T), as when the subject identifies a second

stimulation as different from the first or as the same—the procedureof von Frey and Metzner in determining the successive two-point
threshold. Though pure touch without a localizing movement is

not generally supposed to be a case of localization, logically it

should be classed here. Weber’s method used kinesthesis and touch
together (KT), since the subject was allowed to move the localiz-ing pointer after it had made contact with the skin; he could moveby trial and error until he got a touch that felt hke the first. (3)Vision (V), as when the subject localizes the spot on a photographor plaster model of the bodily member stimulated, In the 1890’s

there also emerged the question of the use of visual imagery (o),so important for localization with most persons. It is possible for a

subject to inhibit visual imagery; thus the localizing reaction is

TACTUAL SENSIBILITY

484

KTV if the subject looks at his aim and moves the pointer aroundon the skin to get the best localization, or KTv in Weber’s method,or pure KT if visual imagery is completely inhibited. Altogether
there aie eleven possible combinations of these factors, nine ofwhich were used from 18S2 to 1902 {vide infra).
It is possible to conceive of ways in which all of these elevenforms of reaction should also he used for the stimulus. Tactual localiTsaiion means, of course, that the stimulus is T. Weber's method

could be symbolized as T-KTv. Henri used a K-V method, however, when he held the subject’s finger over the point to be local-

ized ( stimulus= K) and then had him
the position on a
= V). A V-V method would be one where
localizephotograph (reaction

the subject is shown a point on his sldn and then presently asked to
identify it visually. Thus there are possible 11

X H = 1-21 meth-ods of localizing cutaneous points. The following list shows themethods (with somesthetic stimulation) that have been used inimportant ways and the name of the originator.
r-KTVjVolIanajm.l844
r-KTo; Weber. 1852
T-Ko; Aubert and Kamm1870

let,T-V; Hemi, 1893
TY-KTo; Barth, 1894
K-V: Hemi, 1895
T-KV: Henri. 1806

T-jK.- Parrish, 1897

TV-Kv, Parrish, 1897
T-Ts von Frey and Metzner, 1002

r-KriPinsbmjr.l89S

Weber’s finding in 18S2 was that the error of localization varies
with the bodily region and, although roughly proportional to thetwo-point limen, is always larger flian the two-point limen. The

upper half of Table X shows this proportionality, wliich was actually the reason for Weber’s thinking that ho had in such a method asecond measure of the Ortsinn. Kottenkamp and Ulhidh vei'ified
this relationship in 1870 (lower half of Table X), showing that theen'or of localization, as well as the two-point limen, follows Vierordt’s law of mobility. Because there remains, however, the factthat one measure is three to four times the size of the other, thisdiscrepancy seemed to spoil the possibility that both are measuresof tie size of sensory circles. By 1898 Henri was ready to argue thatthe two judgments are based upon diSerent physiological mech-—a view whichanismsinfluential leaders, like

Wundt, were in-clined to accept. Henry Head (1905), as we have seen, assigned

the two capacities to different afferent systems, There is really,

however, no fundamental incompatibility between these two measures.

A single stimulation gives rise to a dispersed region of exoita-,

ERROR OF LOCALIZATION

485

tion such that two points at the limen of duality are quite far apartand yet lie at the center of regions tangent in the perceptual pattern. If the error of localization lies always within this region ofdispersion, so distributed that on the average it is, say, at half theradius of the region from the center, then the error of localization

TiUJLE X. Rilation of the Two-Point Limen to the Ebbob

OF Locauzahon

Webek (1848, 1852)
2-pt. ftmen

Error local.

Anterior thigh

87.5

15.7

4.3

Volar forearm

40.5

8.5

4.8

Back of hand

31.5

6.5

4.8

Forehead
Lips
Finger tip

22.5

6.3

3.6

4.5

1.1

4.5

2.3

1.1

= t (mm.) = E(mtn.)

Location

L/E

2.3

Av.

= 4.0

KoITENEAMP and UliBICH (1870)
2-pt. limen

Volarupper am;cm. from

Volar

L/E

5.9

87.4

14.2

2.6

13.6

36.2

10.6

3.4

21.3

38.8

9.4

3.6

2.2

27.0

8,7

3.1

6.4

22.6

8.4

2,7

11.3

20.7

8,0

2.6

18.2

21.0

6,2

3.4

21.1

14.2

4.4

shoulderfoream;cm. from
elbow

Error local= L (mm.) = E(mm.)

LooaHon

3.2

Av.

= 3.1

would be half a radius, and the two-point limen would be the distance between the two centers, or two radii, The supposed dis-

crepancy would seem to be more a function of method than ofphysiological fact. Tliis argument, made first by Czermak in 1855,

has been recently repeated { 1980, 1935 )In making tactual localization most persons use visual imagery.
The conscious ‘local sign’ of a touch is the look’ of tire place where
it is.

Only the congenitally bbnd and a few other persons who lackvisualimagery make their localizations entirely in kinesthetic

terms. In the 1890’s, when consciousness was so important in psy-

TACTUAL SENSIBILITY
ohology, there was considerable discussion as to tlie extent to which
visual imagery aids localization. PiUsbury found in 1895 that theerror is largest in the Weber method when visual imagery is in-hibited by the subject(T-KT), smaller when visual imagery isfreely allowed ( T-KTo), smallest of all when vision is encouraged

by allowing the subject to look at his skin while he is making the
localization(T-KTV). Parrish similarly reported in 1897 that theerror is largest when the subject localizes kinesthetically by point-

ing at the spot without touching it and also inhibits visual imagery(T-K), smaller when visual imagery is allowed (T-Ko), smallest
when the visual Imagery is encouraged by allowing the subject towatch the stimulation, having closed his eyes during the localization (TV-fCo). In short, the error diminishes as follows;

Pillsbury;(T-KT) > (T-KTt?) > (T-KTV)

Parrish;(T-K)> (T-Kv) > (TV-Ko)

The more vision is favored, the smaller the error, but it was neverclear that the effort of inhibiting visual imagery by normal visualizers did

not act as a distraction and increase the error in thatmanner.

Another fact of importance in localization is that tliere ai‘e usually large constant eiTors. Both

Lewy (1895) and Parrish (1897)

found that points in the middle of the volar forearm tend to belocalized considerably toward the wrist, that points near the wrist

are also displaced toward the wrist, although less, but that points

near the elbow are apt to be shifted in localization toward 4e el-bow, Such errors Henri attributed to attention. In perception theskin is laid out in respect of certain points or regions of anchor-

age {Ankaltspunkte), which provide a frame of reference. Localizations of points remote from these orienting regions tend to

migrate toward them, because attention is upon the frame andthere are no definitely perceived intermediate points to make themigration seem wrong. Not often does a localization on a finger

spread across a knuckle or from one finger to the next.

There has been other work on the error of localization, such as
die determination of the effect of the time-interval between stimulation and localization (Barth, 1894)

and the measurement of thesize of the error for different modalities (Ponzo, 1911-1913), but

in general the history of this problem has

shown less progress

STIMULUS FOR PRESSURE

487

toward psychological insight than the history of the other measureof cutaneous space perception, the limen of duality.

Stimulation

How the psychophysiologies of smell and taste have been heldback by the failure to discover the essential natures of the olfactoryand gustatory stimuli we have already seen, The study of cutaneous
sensibility has been only a little more successful:

we know some-thing of the characteristics of the stimuli, but we have not yet
identified the receptors.

To Weber and his predecessors it was obvious that the perception of pressure is caused by pressure; thus the sensation could

properly be named for its stimulus. As early as 1859, however,—the man who discovered thereceptor-corpuscles—^pointed out that physical pres-Meissner‘tactile’in the skin of the palms and soles

sure is actually in itself imperceptible. If a hand or a finger is im-

mersed in water or mercury of the same temperature as the skin,
there is no consequent sensation except at the ring where thatmember emerges from the liquid. For this reason Meissner concluded that the stimulus to the pressure sensation is not physicalpressure itself, but the deformation of the skin, that the true stimulus is, inmodem phrase, a pressure-gradient in the skin. Meissnereven made paraffin casts of regions of the skin, applied them socarefully ihat the entire surface of die cast came in contact withthe skin at the same instant, and decided that only the edges of

the cast could then be perceived.

The gradient theory of the pressure stimulus was carried further
by von Frey, at first in independent publication (1896), and laterin more detail with Kiesow { 1899 ) . For this investigation von Frey

invented two instruments that later became classical. The firstwas the limen-gauge (Fig. 81). It is an instrument through which
force can be applied mechanically to a spot on the skin at any pre-determined rate of loading. A kymograph actuates it; a scale indicates the maximal force applied. The stimulus is often a bluntwooden point on a lever-arm, but for what von Frey called "ma-croscopic” stimuli (0.5 mm. diameter and larger) a cork or card-board disk of the right size was placed beneath (^is point. The
other instrument which von Frey invented was the stimulus-hair

TACTUAL SENSIBILITY

488(Fig, 82),

which he used for “microscopic” stimulation (of theorder of 0.2 to 0.05 mm. diameter). After the end of the hah, S,

has been applied to the point to be stimulated, the stick-handle isdepressed in such a manner as to keep the point of inflection, P,

Fig. 81.

Limin Gaoge: vqn Frey ( 1898 )A spring-driven kymogiapb defiects a lever (not shown) at a predetermined rate. This lever pulls the thread, T, raising the lever, A, and exerting downward force at S through the spring, B, and the lever, C, The scaleshows the amount of force, S is a blunt wooden stimulus-point, but "macroscopic” stimuli of different areas can be had by placing small cork or card-board disks of the desired sizes between S and tlic skin.

directly over die point of application,

S (Fig. 82B). With such

use the force remains perpendicularly directed upon the skin, andthe loading is practically instantaneous, because the hair acts likea loaded long column in which the maximal force is required tomake it bend at the start. Hairs of different diameters are chosen;
for a given hair the force depends upon the length of the hair.

Von Frey also consti-uoted another hair stimulator in which thehair projected throng a long narrow hole in an adjustable sleeve
width permitted the extrusion of a short length of the hair forheavy loading or a long length for light loading.

The two chief results of von Frey’s investigation were as follows,STIMULUS FOR PRESSURE

489

The threshold for pressure varies inversely with the rate at(1)

which force is applied; it is less the more rapid the loading. For
instance, in one experiment withA

a macroscopic stimulus of about

21

sq.

mm., the threshold force

decreased from 2 to 1 grm. when
the rate of appHcation

was in-creased from 1 to 2 grm. per sec.
(2)

With microscopic

stimuliand rapid loading—that
say,

is

to

with the hair-stimuli—thethreshold is constant for various
Fig. 82.

of stimuli

sizes

if

Von Fnisv IIaibs (1896)

expressed ingrm. per mm., the quotient ofHairs(horse,ofvaiying

human)

anddiameters

varying

the force by the average radius oflengths are fastened with scaling

the hair. (See Table XI.) Thiswav to the ends of sticks. Whenrule does not hold, however, forlargerstimuli,forwhich pre-sumably more than one receptor
isexcited. With large stimuH thethresholdishigherthelargertheofapplication,

even

area

when expressed in grm. per sq.
mm.

the stick is depressed, the force isapplied perpendicularly to the sldnIt

the point of inflexion, P, is kept
above the point of appli-

dliectly

calion, S. These are “mlorosoopio”

and the loading is “rapid"
like a bng
column in which the maximal
bending bad must be applied at

stimulibecause the hail acts

the beginning of the bending.

On the invariance of the threshold in grm. per mm. with microscopic stimulatian von Frey based his theory of the pressure stimulus. The effectiveness of this stimulus is not measured by the total

force (grm.), nor by the hydrostatic pressure (grm. per sq. mm.),but by the tension (grm, per mm.). He drew, consequently, ananalogy with surface tension which also depends, not on the area,

but on the linear dimensions of the surface film. The adequate
stimulus to the pressure sensation under these conditions seems to

be tension set up within the skin or its own stretching. Another way
of stating the same generality is to say that stimulation depends onthe deformation of the skin where the tensions are set up, principally, that is to say, at the edges of the deforming stimulus. Thisview that a pressure gradient excites the receptors for pressure was
supported further by von Frey’s discovery that traction is as gooda stimulus as a bad; hfting an object attached to the skin elicits thepressure sensation as readily as applying downward force. A pres-

TACTUAL SENSIBILITY

490

Table XI. Lminal Pbessube Stmoli: von Pbey and Kiesow ( 1899)
For “miaoscopic” stimuli (hair-stimuli)tire“tension” is constant for dif-ferent sizes of stimulus; force (“loading”) and pressure (“atmospheres”) arenot. This relationship does not hold, however, for the larger(“macroscopic”)

stimuli These data are interpolated from the continuous functions of vonFrey and Kiesow.

BadiusArea

Pressure

mm.®

Fores
grm.

Tensionmm.

grm./min.

grm./mm.'

Micro*

.02

.0018

.017

.835

13.30

scopic

.04

.0050

.034

.850

6.76

stimuli

.06

.0113

.051

.858

4.55

.03

.0201

.068

.850

3.38

.10

.0314

.085

.852

2.71

Macro-

.40

.5026

.152

.380

.30

scopic

.50

.7854

.251

.502

.32

stimuli.80

1.1310

.547

.911

.48

1.5394

.970

1.386

.63

.70

sure gradient is established, of course, for either direction of theforce which deforms the skin and introduces tensions within it.

The specification of the thermal stimuhis is complicated by tire
fact of liennal adaptation. In his account of the nature of second-ary qualities John Locke in his famous Essay of 1690 touched on
this problem. Inasmuch, he observed, as the same water may feel

hot to one hand and cold to the other, the reason must be that thesensations of heat or cold depend on the “increase or diminution of

the motions of minute parts of our bodies, caused by the corpusclesof any other body.” Thus, “if that motion be greater in one band

than in the other, [and] if a body be applied to the two hands

which has in its minute particles a greater motion than those in
one of the hands, and a less than those of the other, it will increase the motion of the one hand and lessen it in the other; andso cause the different sensations of heat and cold that depend
thereon.” Thus Locke’s ‘theory’ of the thermal stimulus is that thehand feeb warm when it is being warmed, cool when it is being
cooled, and that the same stimulus that warms a cold hand may

cool a warmed one.

Weber’s theory in 1840 was the same as Locke’s; when the temperature of the skin rises, one perceives warmth; when it falls,
cold. Vieroidt, however, having at first accepted Weber’s theory,

objected in 1871 that a flow of heat without a change of tempera-—cold when the flow

ture may elicit the thermal sensation

is out-THERMAL STIMULUS

491

ward, warm when it is inward. For illustration he cited the persistence of the sensation of cold when a very cold object, having

been in contact with the skin, is removed. It was his contention
that the outer skin is in this case so cooled by the object that heatfrom the blood continues to flow toward the skin while the skiniswarming up. On Weber’s principle warmth should be felt be-cause the sldn is warming up; on Vierordt’s, cold because the conduction is outward. As a matter of fact, this situation probably involves a positive after-sensation, a neural rather than a thermallatency, yet Vierordt’s case

is

also

supported by other factors.

Warmth, for example, can be felt for such long times in the presence of radiant heal that it would seem stable temperatures mustbe established before the sensation ceases and while the flow ofheat still continues. The converse situation also holds, of course,
for cold.

The next step in establishing a theory was taken by Hering. Having published in 18T7 a theory of thermal sensation, modelled after
his theory of vision,and having written in 1879 the section on

Temperatursim in Hermann’s Ilandbwh, Hering noted certain
difficulties with Vierordt’s theory. Since the blood is warmer than

the skin, there is a constant outward flow of heat, which is notsensed as cold and indeed gives rise to no thermal sensation at all.

Thus, if the skin is warmed up from neutrality, the initial stimulus
to warmth is not conduction inward, but a diminution of conduc-tion outward. Arguing that a diminution of outward conduction

can be equivalent to inward conduction only if conduction has

some relation to an equilibrium of the sense-organ, Hering undertook to describe the operation of the thermal organ in terms of fatigue (adaptation), contrast and physiological zero {NuUpunkts-

temperatur ) The stimulus to temperature, he said, is the amount of.

heat conducted to the sense-organ, and conduction outward must

be considered as a greater or lesser amount of negative conduction
inward. Positive conduction inward sets up in the organ a processthat may be called dissimilation; negative conduction inward, thereverse process of assimilation.

When such stimulation is con-tinued, however, the organ becomes fatigued until the process,diminishing, ceases; there is adaptation, and a new 'NuUpwnkts-

temperatur is established. Thereafter, increase in positive conduction again arouses the dissimilation process, whereas decrease inpositive conduction(or an increase in negative conduction)

TACTUAL SENSIBILITY

492

arouses assimilation, a contrast effect. There is no problem as towhy a decrease in positive conduction should have the same effectasan increase in negative oonduclion, because dissimilation andassimilation are probably both going on all the time, and what ismeant by dissimilation is merely the preponderance of the dissimilative process over the assimilative, and conversely, Although
Hering’s notion of these two antagonistic excitatory processes has

not been generally accepted, his basic principle is regarded as valid
today: the organ adapts to any continuous thermodynamic situation, establishing a new point of equilibrium or physiological zero.

Thereafter, any deviation from this steady state toward the conduction of more heat to the receptor is a stimulus to warmth, and thecontrary deviation a stimulus to cold.

In this connection certain facts must be recalled. Weber, believing that the temperatureand pressure senses are one, con-sidered that he was dealing only with different modes of stimulation of the same sense. Hering, however, decided that these twosenses are independent, although warmth and cold he thought ofas belonging to a single temperature sense. Von Frey, on die con-trary, held diat warmth and cold are separate senses with differ-ent organs. Von Frey’s theory would have been fatal to Hering’s
had it not been for the fact of successive contrast between warmtli
and cold, a fact that John Locke used to prove these qualities sec-

ondary, a fact that made it plausible to suppose the existence ofsome connection between the organs for cold and warmth.
In spite of the ascription of thermal sensibility to a temperature
sense and the habitual specification of thennal stimuli in terms oftemperature, it is true that no sophisticated investigator of theseperceptions had ever, since Weber, regarded temperature as anadequate measure of the thermal stimulus. Hering was at pains toshow that thermal conductivity of the stimulus-object is important;at agiven temperature wood is less cold or warm than metal.

Sherrington in 1900 listed the effective properties of the thermal
stimulus;

temperature, thermal conductivity, specific heat, in-timacy of contact with the skin, and the increments or decrementsof radiation.

He might have added mass, for a tiny drop of boilingwater has in it insuflficient heat to excite even a single warm spot.

Von Frey carried Heiing’s neural theory of thermal sensitivity
one step further in 1895 by his discovery of paradoxical cold, thestimulation of a cold spot with a warm stimulus (above 45° C. inSTIMULI FOR WARMTH, COLD AND PAIN

493

some parts of the skin) resulting in the elicitation of the sensation—of coldasought to happen under the theory of specific nerve

energies. Although recent research makes it doubtful whether thephenomenon is as universal as von Frey believed, this discovery
has nonetheless been amply verified.

We shall see later how Alrutz

argued that the perception of heat is a fusion of normal warmthand paradoxical cold (pp. 504 ff.). If the same stimulus can give

warmth at one place and cold at another, then there must be twokinds of receptors.

Two recent theories of thermal stimulation are Jenkins’ andNafe’s. Jenkins, who failed to verify von Frey’s exact localizationof cold and warm spots and also the universal occuiTence of para-

doxical cold, formulated in 1938 a theory analogous to Hering’s.

Assuming the existence of a “pseudo-reversible reaction,” in which
stimulation causes the reaction and a catalyzer the reversal, he ex-plained most of the normal phenomena in this fashion. Nafe andhis associates, on the other hand, also opposing von Frey’s theory,

have presented evidence that warmth is the proprioception of therelaxation of the vascular muscles in the skin, and cold of die contraction of the vascular muscles. This theory also is a return toHering in so far as it makes of warmth and cold a single system.
It cannot be said, however, that either of these theories has as yet

received general acceptance.

The adequate stimulus for cutaneous pain has never been so
predsely specified as it has for the tirermal sensations and for pressure. Although a sharp needle or thorn penetrating the cells of theepidermis will elicit pain, the sharpness of the stimulus seems to

be more a way of getting at the receptor than the property for exdting it. It is not easy to give piedse specification to the sharpness of a pricking point, and the threshold for prick-pain, whenforce is varied, seems to depend primarily upon the hardness ofthe superficial layers of the epidermis. For quantitative determinations von Frey used a flat areal surface and a force far above thethreshold for pressure; yet it does not seem that a blunt applicator

should constitute a normal stimulus. Since it is true, moreover,that the pain threshold thus determined may be no higher than thepressure thresholdifenough of the superficial cells of the epi-

dermis have been scraped away, one seems here alsq to be measuring the adequacy of an obstruction to excitation rather than thenature of excitation. The best algesic stimulus, the most constantTACTUAL SENSIBILITY
and reliable, is radiant heat, as Hardy and his associates have recently (1940) shown. They found that die threshold for pain on

the forehead is remarkably constant from point to point, fromtime to time, and from person to person, and that sensitivity topain is diminished by opiates in the system, by acetylsalicylio acidat the spot, by intense pain elsewhere in the body, but not by oo-

clusion of the blood supply, Even this exoellenl method provides,

however, no hint as to the fundamental nature of the algesic stimulus.

The persistent ignorance about the nature of the algesic stimulus
is, oicourse, consistent with the equivocal status of pain as an in-

dependent sense. We have already seen how Weber consigned
pain to the Gemeingefuhl, and how later investigators regarded it
as common sensation or the consequence of intense excitation of

any sense. Goldscheider especially made the argument that painisaroused by the summation of pressure excitations. It was not

until 189S that von Frey seemed to establish pain as a separate

modality with independent receptor-s of its own, tho free nerveendings in the epidermis. With the discovery that the free endings

must also mediate warmth and odd and perhaps some pressurestoo, however, his argument lost some of its force. Headseq.) associated pain(

1905 etwith extreme warmth and cold in proto-

paflrie sensibility. It is no wonder dren that the stimulus for painisunknown, when the existence of pain as an independent sensewith separate receptors has rmlil recently been in doubt.
It is true that von Frey had a theory of pain, but it was tied up

with his belief about the receptora for pressure and pain. Having
demonstrated, as he thought, that pressure depends upon the excitation of the free nerve endings about the hair follicles beneaththe epidermis, and that pain depends upon the excitation of thefree nerve endings between the cells of the epidermis, he had toshow why the deeper organs are so much more readily excited thanthe more superficial ones. His answer was, of course, that the toughepidermis, protecting, as it does the endings lying within it, trans-

mits a dispkdng force to the organs in the softer underlying tissue.

Thus he showed, using hair-stimuli with enough force to elicit pain,that the pain threshold is about constant for difierent-sized hairs

when hydrostatic pressure (grm./mm.*) is used, and that surface tension ( grm./mm. ) is not a measure of stimuli equivalent for

pain as it is for pressure. Such a result would be natural; the pres-WEBER FUNCTION

495

sure per unit area would be the most likely measure of the force

necessary to get at receptors within the leathery epidermis. The
theory, however, gives us insight neither into the properties of thepain receptor nor into the means whereby intensitive degrees ofpain can be uniformly aroused.
In general, then, it may be said that the psychology of cutaneous
sensations is held back by lack of knowledge of the nature of theadequate stimuli and of the receptor organs. The history of the
field waits upon

new insights.

Weber Function
When Weber found that 14% and 15 ounces, and also 29 and30 ounces, as well as 14% and IS drams, placed successively on thefinger,could be discriminated “only wifii the greatest difficulty,”

he naturally concluded, without investigating a long range of
weights, that Weber’s law, as it was called later, holds for weightin the Tastsinn, The discrimination ratio for the finger he therefore
set down at

so that the Weber fraction, in modem phrase,

was %o,Next he raised the question as to how discriminatory capacity

would vary with sensitivity of the skin. The Ortsinn (two-point
threshold ) is one-ninth as fine on the forearm as on the finger, anda five-ounce weight on the forearm feels about as heavy as a four-

ounce weight on the finger. Weight-discrimination in these two regions turned out, however, to diange in an amount proportional
to neither of these other changes.

On the finger the ratio was

H we convert these^%o)> and on the forearm
fractions into comparable figures, add the value that Weber got
for muscle (weights held by the fingea:s in a cloth sUng), and write

the Weber fractions, we have;

Finger muscles :Finger skin;Forearm skin:% o = 0.025o%oo = 0.04

= 0.09We must now, as we trace the history of Weber function for theskin,exclude from consideration the accurate muscle sense. The

firstdetermination of this function, the variation,of the Weber

fraction throughout a considerable range of weights, was made by

Biedermann and Lowit and reported by Hering in 1875 when he

TACTUAL SENSIBILITY
was discussing Weber’s law. It is natural that Weber should nothave made observations through a long range of intensities; hecame to the problem with a conviction that the “Weber fraction’isconstant and that the Weber function’ is therefore a straighthorizontal line. Biedennann and Ldwit’s values are given in Table

XII and Fig. 83. This figure shows how much they vary and how
they vary, a continuous fimction except at one end.

What im-pressed the psychologists of the nineteenth century and even later

was, however, the relative constancy of the fraction in Uie middle

Fm, 83. WsBKH Functions foh PaBssmiEs; BmuEnMANN and Lbwii ( 1875)
AND Gath and Dodob (1020)
Biedennann and Lbwit used deep pressure, Gattl and Dodae cutaneouspressure on an isolated pressure spot. The function obtained by Galti andDodge is smootlier than Kiesow’s (1922).
range. If the absolute weight is quadrupled from 100 to 400 grm.,

the fraction is not quite halved (0.024 lo 0.013); from 200 to 450

grm. it is even more constant. These values of the stimulus, 10 to
500 grm. mean, of course, that deep pressure, not truly cutaneouspressure, was being studied. Neither Weber nor any other of thepsyohophysiologists before von Frey ( 1895 ) and Head ( 1905 real)

ized that it takes very light loads to test only the skin and not theunderlying organs.

There seems to have been no thorough determination of theWeber function for the skin alone until the investigation by Kiesow
in 1922. He used von Frey hairs on single pressure spots, establish-

ing the function for intensities from 1 to 8 grm./mm. Gatti andDodge by an even more careful technique verified his findings in
1929. See Table XII and Fig. 83. In one respect both curves
resemble the Weber functions in many other departments ol sense(though not all); they show that the Weber fraction, far from

WEBER FUNCTION

497

being constant in accordance with Weber’s law, has a minimumin the middle ranges of intensity.

The problem of the validity of Weber’s law for temperature atonce comes up against the question of the location of zero intensity in the scale of temperature.

The I for warmth must be

Table XII. Webeb PoNcnons fok Deep Peessuhe andCutaneous Feessuee

=

=

=

just noticeable difference.
AZ/I
Weber fraction.
intensity. AI
I
Biedormann and Lowlt ( 1875 ), who used weight in grm. as I, were determining a function for deep pressure. Eesow (1922) and Gatd and Dodge(1929), using tension in grm./’nim. as I, were determining functions
isolated pressure spots in the shin.

WeightBiedemamTendonin grm.

and Lowlt

In gm./mm.

Gam
jCtes0w

and Dodge

I

AI/I

1

AI/I

AI/1

10

.070

1

.2100

.1854

.034

2
3

.1504

.1529

.024

.1647

.1411

.018

4

.1404

.1425

.015

5

.1385

.1356

.013

8

.1453

.1442

.014

7
8

.1705

.1486

.1948

.1548

50
100
200
300
400
450
SOO

.051

measured up from zero temperature, and the 1 for cold measured

down. Webor did not attempt to setde the question. Fechner, however, in 1855 conducted some experiments, adapting two fingers

to the same temperature in water,

and testing differential sen-sitivity by immersing one finger in water of one

temperature andthen the other finger in water of another temperature. For thezero of his system he chose 18.5°C., which is halfway between thetemperature of the blood, ST’C., and freezing, 0°C. (Actually heused the Reaumur scale of temperature, but we may translate his
figures into Centigrade. ) His results in terms of temperatui’e, T,

and in terms of degrees above and below this arbitrary zero, I, wereas follows:

Cold

r= 5

tol3"C.
tolS.S’C.

I—

13.5to-5.5"C.

AI=0.00a734P

I=- S.Sto

O'C.

AI is hjo small Id meas-

Warmth r= 18.5 to 25“ C.

1=

0

6.5“C.

AI is too small to meas-

r=25

1=

eAto20.S"C.

r=13

ure accurately
toure accurately

to39“G.

AI is approximately
proportional to I

TACTUAL SENSIBILITY
Wifli this zero, Weber’s law is approximated only above 25°C,

but this is a strange zero. Feohner did not know die temperature of
the skin. He did know that body temperature is too high to be thezero, for body tempei'ature feels warm to the skin. Thus he took

the average between body temperature and the artificial zero of
the R&umur thermometer (freezing point of water),

In 1867 Nothnagel deteimined the temperature of the skin as
lying between 33°

and 36°C. when room temperature is about

18°C. By a method similar to Fechner’s and by the use of cold andwarm metal cylinders, he satisfied himself that Af is minimal in
the region of skin temperature and just below, whereas above andbelow this region it increases slowly at first and then rapidly. Sucha mode of variation, although it hes in the direction of Weber’slaw, does not validate the strict proportionality tiiat it requires.

Notwithstanding the fact that there have been other attempts todetermine this relation, it has been hai'd to get consistent functions.

Miss Abbott in 1914 published a thorough study in which she

showed (1) thatM

isminimal at skin temperature (32.5°G.)

whatever the state of adaptation of the skin, (2) that 47 increases
steadily above and below skin temperature although not sMctlyin accordance with Weber’s law, and (8) iliat the rate of inci'easein 47 is more rapid the greater the deviation of adaptation-tem-

perature above or below 32.5°C. In other words, normal skintemperature furnishes a fixed point of orientation for the sensory

system inespective of the migration of physiological zero above or

below it.

The failure to discover the nature of the intensitive stimulus topain has left the investigation of the algesic 47 and of Weber’s law
for pain an impracticable undertaking.

Summation
That temperature sensations are stronger when the area of stimulation is larger was observed by Weber. Warm water feels warmer

to the immersed hand than to a single immersed finger, cold watercolder to the hand than to a finger. “It appears,” he said, “that impressions of warmth elicited by many sensory points summate in

the brain, whither they are conducted, bringing about a total impression.” This thermal summation he had to localize in the brain

because he believed that all the sensory circles are isolated at the

SUMMATION
skin and projected upon the brain, thus accounting for spatial dis-

crimination under the Ortsinn. Similarly he explained the elicitation of pain by exti'eme warm or cold stimulation as due to sum-mation. In addition he noted that thermal summation occurs lessreadily when the points of stimulation are far removed from one

another than when they are adjacent.

That Weber’s theory of summation for warmth and cold is correct has been subject to some doubt. Barnholdt and Bentley in 1911

thought he was wrong. Their experiments indicate that the larger
area feels warmer (1) because it more often includes the moresensitive warm spots and (2)because the larger area is a more

adequate stimulus for every receptor near its center. A similarargument would hold for cold.

We have aheady seen how Goldscheider in 1892 elaborated thenotion that pain is due to summation, especially—and inthishewas unlike Weber—the summation of successive pressures (pp.
408 f ) While this theory of pain had its adherents for a long time,.

.

von Frey’s notion that pain is a separate modality with its own receptors finally won out.

Hardy and his associates (1940), using

radiant heat as a stimulus, moreover, found no evidence at all foralgesic summation.
It was von Frey’s pupil, Bruckner, who in 1901 established thefact of the summation of pressures. Although Weber’s theory of

the Ortmn seemed to require that pressures should not summate,

Bruckner showed that there was no reason why two adjacent stimulations, fused into one, should not give a single impression thatappears more intense than either of the component stimulations
alone. His data exhibit

many instances of two weak pressures,

whose stimuli are separated by distances of from 2 to 30 mm.,yielding a single more intense pressure when applied simultaneously. He also descnbed, less extensively, oases of inhibition or“subtraction,” as he called it. Inhibition occurs at wider separations( e.g.,

62 mm., 84 mm. ) ; at such separations two sensations may be

weaker, stimulated simultaneously, than either of them when thestimulation is given separately. Bruckner also found that two weaksuprahminal stimuli, when given simultaneously and not too doseto each other, sometimes give rise to but a single sensation; and insuch a case he beheved that it is attention that determines whichof the two is felt.

500

TACTUAL SENSIBILITY
Adaptation

Because of the reciprocal relation of themal adaptation andsensitization in respect of warmth and cold, more has been writ-

ten about adaptation to tempeiatuie than to pressure. The fact ofthermal adaptation has, indeed, always been embodied in common
sense. John Locke in his discussion of primary and secondary qual(p. 490) simply alluded to the phenomenon as something
known to all. Weber based his theory of the TempercUursinn upon

ities

it.

Hering’s concept of a variable Ntdlpmktstemperatur is a theoryof it. The principle, in short,

was indubitable. It was necessary

only to work out the quantitative functions.

Of these quantitative studies there have been a number, but,
since they have not settled the question of the nature of the thermal—the upper

stimulus, they furnish little more than handbook data

and lower limits of adaptation in terms of temperature, the rate ofadaptation, the effect of adaptation upon differential sensitivity.

Miss Abbott ( 1914), in the study already cited (p. 498), was able
to adapt the skin of the fingers to all temperatures between 17°

and 40°C., in the sense that 18° would feel warm to skin longexposed to 17° and that 89° would foci cool to sldn long exposed
to 40°. Under these extremes of adaptation, skin temperature does

not vary so much from its norm (32.5°C.) as does adaptation
temperature, a fact which favors Heting’s theory over Weber’s.

Miss Abbott also found, as we have seen, that normal skin temperature remains tire orientation point of the functions for discrimination, even though the actual skin temperature may differ

from it somewhat and the adaptation temperature even more. Someof these findings Gertz confirmed in 1921, although he was notable to get complete adaptation to temperatures above 35°C.

Jenkins in 1937, studying adaptation for isolated cold spots, foundthat complete adaptation is often attained in four seconds, but thatlong exposure to cold after adaptation renders recovery slow andsensitivity still unstable after apparent recovery.

Adaptation to pressure has also been long embedded in com-

mon sense—the unfelt ring on the finger, the spectacles lost because they have been pushed up on the forehead. It is taken for

granted that sensations should ‘fatigue.’ ’There has not, however,been much measurement of pressure adaptation, perhaps because
the phenomenon has not had as great theoretical sigi^oance asADAPTATION

501

thermal adaptation. The early phenomenological papers, in describing the course of the pressure sensation with a continuing
stimulus, note how its intensity diminishes or how the sensation

fades out. Both von Frey (1896) and Kiesow (1898) gave suchaccounts. Many of the quantitative relations have recently been

determined by Zigler ( 1932), who has shown that adaptation time
is directly proportional to theweight of the stimulus and inversely

propoitional to its area. On the hand he got complete adaptationin 2.4 sec. for 50 mgrm., and in 9.5 sec. for 2000 ragrm. The times
for the face were longer.

The occurrence of adaptation for pain has been doubted. The
lapse of time does not seem to relieve the pain of neuralgia, of

peptic ulcers, or of aitaneous burns. Cutaneous pain, however, thekind that comes from a light prick of a needle or a thorn, should
not be judged by these traumatic instances. There is evidence thatthe initial prick of a needle may fade out quickly if the needle is

kept perfectly stOl. Miss Murray in 1908 suggested that it is “quite
hkely that cutaneous pain is mediated by two sets of endings, theintense but quickly fading variety

.

.

.

and the more severe andlasting (including ache).” Strauss and Uhlmann in 1919 obtainedcomplete adaptation to a 3-grm. load on a needle in from 4 to 28
sec.,

and to an 8-grm. load in 13 to 72 sec. The interpretation ofthis result is not certain, sincenobody knows how the pain re-

oeptois work or whether, indeed, the free nerve endings are re-

ceptor-oigans or simply free endings, excited directly after themanner of pain fibers in a pricked nerve trunk. If the pain sensation fades out merely because the needle throws the fibers out offunction by creating a tiny lesion in the neural tissue, then weshould not be considering the kind of effect that is ordinarily called
adaptation.

After-Sensations
Tactual sensation may persist after the removal of its stimulus,or, having been lost under adaptation,

may recur upon the removalof its stimulus; it may even recur a brief interval after the removalof the stimulus. The hat on the head is no longer sensed but isfelt after being

taken off. Although not so frequently as adapta-

tion, the fact of tactual after-sensation is often recognized in com-

mon sense. Nevertheless Weber did not mention it, nor Feohner.
As soon as the active period of research on cutaneous sensibility

TACTUAL SENSIBILITY

502

got under way, however, the after-sensation began to be mentioned
in print, either as an incidental phenomenon, or as a difficulty

which interfered with an experiment. Kottenkamp and Ullrich, forinstance, in their study of tactual localization in 1870, found that itwas necessary to have the subject wait, before making the localization, until the after-sensation from the stimulus had disappeared.
In 1880 Funke mentioned after-sensations for pain as well as pressure; in 1881 Prcyer noted after-sensations for warmth

—

^the

and cold

positive after-sensations of persistent warmth or persistentcold, not the familiar negative after-sensations where warmth fol-lows cold, or cold warmth, due to the shift of the physiological zero.

Thereupon, after Goldscheider (1882-1885) had described theafter-sensations for all four qualities, Urbantschitsch, in 1887, meas-

ured their duration and, in those cases where the sensation lapsed

and then recurred, the duration of the latent interval. In the 1890’s
there were at least a dozen descriptions of these phenomena, in-cluding von Frey’s accounts of adaptation and the persistence ofsensation after the removal of the stimulus, experiments which wehave just cited.
It was in 1892 that Dessoit pointed out that

we have here really

two phenomena: ( 1 ) the persistence of sensation, which he called"continuous after-sensation,” and (2) the recurrence of sensation
after

an interval, which he called “intermittent afler-sensation,"

This is a useful distinction, because all sensations necessarily havesome lag in cessation, but recurrence after cessation implies theoperation of some special receptor process. Later the two kinds

were distinguished respectively as primary and secondary aftersensations, and also as sAer-sensations and after-images.

Likewise in 1892 Goldscheider published, witli the assistance ofGad, an elaborate study of after-sensations, a study which was directed almost entirely to the support of the summation theory ofpain which we have considered elsewhere ( pp. 468 f ),.

It was theirdiscovery that weak electrical or mechanical stimulation yields
pressure, strong stimulation pain, and a controlled series of stimulations (like four or five induction shocks 30-60 millisec. apart) a

primary sensation of pressure but a secondary afler-sensation, fol-lowing an interval,

prick pain (sine stechende Empfindung).

One shock wa^s never enough to give the after-sensation of prick,which could, however, be got with from two to seven shocks, provided the timing was right. The greater the number of shocks, theAFTER-SENSATIONS

503

more rapidly did they have to be given. This secondary pain,
Goldscheider inferred, is due to summation of successive effectsof stimulation. Occasionally the after-effects appeared, not as pain,

but as a secondary pressure—a case of their being

felt without sum-mation, he fhought.

Thunberg in 1902, although concerned to discredit Goldscheider’s summation theory, reported in great detail on ‘double pains.’

A small disk of metal—he called it a Temperator—could be takenfrom hot water and laid on the skin. It cools off rapidly, but inso doing it gives rise to a primary sensation

which Thunberg

fhought was a mixture of pain and pressure, and then, after abrief interval, there is a secondary after-sensation which Ihun-

berg described as pure pain wiffrout the pressure. Needles too,
applied with constant pressure and without subsequent move-

ment on the sldn, give rise to two successive pricks, a fact which
Miss Murray, as we have just seen, thought might mean the successive excitation of different receptors. Although the conclusions

here are confusing, the fact that the secondary pricks are not felt
until after the stimulus has ceased to act was nevertheless estab-lished without question.

Urbantsohitsch in 1905 reported a study of the localization ofafter-sensations. The secondary after-sensation, he found, may belocalized differently from the primary sensation, may “irradiate”

over an area, or migrate within the area. If a second stimulus beapplied at the time when the after-sensation is about to appear,then the after-sensation is likely to migrate toward the second
stimulus. It is also true that the appearance of an after-sensatiou islikely to—especially in the case of cold—thebring with itre-arousal of sensations localized at other points which have been
recently stimulated. There are, in other words, after-effects which

may result in after-sensations; in a tactual mechanism so complex
a sensory spot does not act in isolation. One has thus to regard
fairly large areas of skin as interrelated in an excitatory system.

Mrs. Hayes, publishing in 1912 a study of the time-relationships
of primary and secondary after-sensations and of the intervening
intervals,

found great variability. By limiting stimulation to theskin, Dimmick in 1916 sought to get more constant results for pres-sure. With von Frey hairs too weak to excite subcutaneous pressure,

he worked on isolated pressure spots. These ratios of durations
he found to be approximately constant-primary after-sensation:

TACTUAL SENSIBILITY

504
latent interval:

secondary after-sensation=

2;l:7.

There were,

however, huge individual differences in actual times, which were,indeed, about seven times as large for the slowest observer as forthe fastest.

Finally Holland showed in 1920 that the instabiHty and variabilityof after-sensations is dependent in part upon the adventitious

introduction of central factors. It makes a great difference whether

the observer assumes a passive receptive attitude, or an active attitude in which he attempts to secure as much cutaneous experi-ence as possible, With the passive attitude the primary after-sensations lasted only from 0.7 to 2.0 sec.

and the secondary after-

sensations were few and brief, whereas with the active attitude theprimary after-sensations lasted on the average about 4 sec,

( al-thouglr sometimes as long as 200 sec.) and the secondary aftersensations were both very numerous and often of very long duration. Whether these numerous delayed persistent after-sensations

were true after-sensations (peripherally excited) or voluntary
imagery (centrally excited sensations), Holland could not, ofcourse, tell.

Heat
One of the interesting and controversial problems of thermal
sensitivity

concerns the nature of the perception called /leot, a

special quality to be distinguished from warmth. Von Frey, as wehave seen, discovered in 1895 the paradoxical arousal of cold froma cold spot by a warm stimulus, a discovery which was crucial in
supporting the tiieories that cold and warmth have different specific energies, are in fact independent senses. In 1896 Alrutz, work-

ing in the Physiological Laboratory at Upsala, having verified vonFrey’s findings on the independence of the two ffiermal senses,

proposed the theory that the quality heat depends upon the excitation of warm receptors simultaneously

excitation of adjacent cold receptors.

with the paradoxical

Such heat is qualitatively

unique, he argued. Coming from the concurrent stimulation of

warmth and cold, it occurs under ordinary conditions when stimulus-objects with temperatures above the threshold for paradoxical

cold (ca. 45°C.) and below the threshold for pain (ca, 50° C.) arein contact with both cold and warm spots. Using Thunberg’s Temperatoren, the thin silver plates whose effectiveness depends upon
their temperature and mass, he arranged graded series of stimuli

HEAT

SOS

extending from one giving no thermal sensation up to one giving
painful heat. On regions that contained both warm and cold spots

he got, with this series of stimulators, first wamth, then a newstinging quality which he named heat, and finally at the top of theseries pam'ful heat.

On regions where there were warm spots but

no cold spots, warmth passed directly over into pain witliout heatas an intermediate. On regions where there were cold spots but

no warm spots, he got no thermal sensation in the lower regions

where he had before got mild warmtli, then paradoxical cold, thenFig. 84.

Heat ane the Theiimal Series of Sensations; von Frey
(1895, 1904) AND ALRim (1897)

The curves show the excitation of the receptors for warmth, cold andpain ns n function of stimulus temperature. The terms at the top of the dia-gram show the resulting thermal sensations, with heat as a fusion of warmthand paradoxical cold. 'Ine idea is Almtz’s, but the diagram is von Frey's
pain, but no heal. Thus heat, he concluded, is a fusion of warmthand cold, just as gray may be a fusion of blue and yellow, gray being unique and neither bluish nor yellowish. Sometimes, however—so Alrutz reported—the heat can be analyzed introspectively
into warmth and cold (espedalfy on the forehead), an taperfectfusion that makes heat resemble more the blending of red andyellow in orange.

Von Frey was happy enough to accept Alrutz's theory which
supported so well his own. In 1904 he published the diagram ofFig. 84 showing how the three excitations for wajmth, cold andpain would combine to give a thermal series of perceptions; burning cold (freezing), cold, cool, thermal indifference, warmth, heat.

TACTUAL SENSIBILITY

506

burning heat. This theory, being simple, positive and empiricallyfounded, was generally accepted by the textbooks; among the experts, nevertheless, controversy arose. The controversy has centered

upon the question as to whether the heat quality is imiquo (likegray) or merely a Mischempfindmg
in which the dements remain intro-

spectively recogniaable (like a tonal

dyad, c-g), and more recently as towhether heat is a good word withwhich to describe the fusion.
Thunberg, before Alrutz published,

had built what others later called aheat grill. In 1896 he devised an instrument consisting of two coiled
Tuunbebo’s ThertiUL Gbh-l (1396)

Fig. 8S.

spirals of parallel metal tubes, so ar-ranged that cold water (ca. 24‘’C,)

Two adjacent metal tubes,

could be run through one tube, andeach 3 mm. diam., are colledwarm water (ca. 44°C.) through theintoa double spiral of 5.S

cm. diam., whleb is applied
to the skia. Cold water ispassed through one tube andwarm through the other. Although Thunberg reported aleaultunt cold-warm

Mlsch-

the numerous
progeny of this apparatus(1913 et aeq.) are called
heat grills, because theirmpfindiing,

constructors
rutz’scold

theory= heat.

acceptedthatAl-

waxm +

adjacent tube, to stimulate the samegeneral area of the skin simultane-

ously with both temperatures. (See
Fig.

85.)

He got imperfectly the
He wrote that

Alrutz phenomenon.

the perception,

when the cold wasadded to die warmth, was “as if thetemperature were suddenly raised

and a feeling of Tiot’ ensued.” Thunberg, however, held that the perception was but a MUchempfindmg inwhich the warmth and cold could still be separately perceived in
an imperfect fusion.

Kiesow in 1901 and Hacker in 1913 agreed with Thunberg thatthe fusion is imperfect. Meanwhile Goldsoheider insisted in 1912
that the perception is not what can be called heat unless pain is in-troduced.

At this point in the history both Rubin and Goldscheider, publishing independently in 1912, discovered paradoxical

warmth.

Rubin reported that cool stimuli just below skin temperature(0.1-1.5°C. below) arouse from warm spots a faint sensation of

warmth, whereas Goldscheider reported getting faint warmth from

HEAT

S07

wann spots stimulated at 6-10°C. below sldn temperature. This discovery creates a difficulty with von Frey’s diagram of Fig. 84. Heat

ought to be felt for a cool areal stimulus. Paradoxical warmth -jcold ought to feel the same as warmth -j- paradoxical cold; paradoxicality refers only to the inadequate mode of stimulation and not
to the resultant innervation or quality. This point made no difficultyfor Goldscheider, of course, because he believed that heat requires

the admixture of pain in any case. On the other hand, Rubin, who

accepted Alrutz’s theory, suggested that the mild paradoxical

warmth might simply inhibit the cold incompletely and thus giverise to the perception cool, whereas the paradoxical cold, which isalways intense, when mixed with intense warmth gives a different resultant. Inasmuch as there have remained still other doubts

about the Alrutz theory, this matter has never been settled.

Next Cutolo at Cornell, the headquarters of introspective psychology in America, undertook in 1918 a careful study of the quality of the warm-cold fusion. After first localizing

warm and cold

spots he then used a thermesthesioraeter, an instrument with two

blunt hollow points which can be fixed at a predetermined separation on a bar. Putting cold water (ca. 1S“C.)

through one point

and warm water (ca, 44°G.) through tire other, he applied thecold point to a cold spot and the warm point to a warm spot. He
also built a heat grill of apposed glass lubes, in which cold water

ran through the odd tubes, and warm water through the even,

From both these experiments his observers got what was certainly
at times a unique experience, for one of them remarked that "itis laughable to think of heat as conditioned upon warmth andcold.” The experience was, they said, like pain or a “sting” or a“smack.” Since they were agreed that the quality is more likepressure and pain than like warmth and cold, Titchener later assigned heat a place intermediate between pressure and prick in
his qualitative continuum of the touches.

Cutolo decided that this kind of heat is not a Mischempfindun^
nevertheless, even with punctiform stimulation, his observers often

repotted the simultaneous occurrence of warmth or cold or bothalong with the heat, the three qualities being interpenetrated in acomplex pattern of localizations. In 1930 FerraR and Dallenbach,using a grill, came to the same conclusion, that the^warm-cold fusion is a unique quality in the pressure-prick continuum, somewhat

nearer pressure dian prick.

TACTUAL SENSIBILITY

508

There were also at tliis time al least three other paper's which
suppoi'ted the Alrutz theoi'y by getting the observers to identify
this kind of heat and then determining some oi the properties of
itsarousal, Alston in 1920, using an esthesiometer like Cutolo’s,

found that the warm-cold fusion can occur when the stinmlated
spots are as far apart as 10 to 15 cm. Burnett and Dallenbach in
1928, using a grill, compared the intensity of a heat in one arm
witli the intensity in the other, and concluded that the intensity ofheat varies directly with the quantity (32-C) -)- 3(W-33), where

G is the Centigrade temperature of the cold water in the grill andW the temperature of the warm water. Miss Knight in 1922 showedthat warmth, stimulatedby radiant heat, and pain, got from a

sharpened hair, can fuse to give a burning heat, quite in accordance with the von Frey diagram (Fig. 84).
Until W. L. Jenkins attacked it in 1938, this theory was, there-

Jenkins had not been able to elicit

fore, pretty well established.

paradoxical cold as regularly as had previous investigators. Now,

working with a large number of untrained subjects, he discoveredthat hot is not an adjectiva which people ordinarily apply to describe the war-m-cold fusion.

Among his 126 subjects, when hestimulated them by means of heat grills, he failed to get anyone
to describe the experience as hot

When he added electric shockto the warm-cold stimulation, he got frequent reports of heat. By

adapting a region to cold, so that paradoxical cold could not beelicited from it, he was still

able to get ‘heat’ if the temperature

was high enough to arouse pain.
The final status of the problem is really not so. confused as
Jenkins’ polemics against AJrutz and DaUenbaoh imply. It is be-

coming dear that the four tactual modalities are related. Warmtli
and cold fuse to give a something which in part resembles bothpressure and pain. Yet this fusion is often so imperfect that warmthand cold can still be perceived in it or at least in pai't of the pattern.

A heat grill, however, favors analysis because it gives a wide-

spread pattern of warmth, cold and the fusion. When the fusion ispoor with a grill you call it a Mischempfindmg, hut at the sametime may note, as have hundreds of college students to whom thegrills have been demonstrated, the unique and interesting noveltyof the fusion. When the fusion is good, you believe in Alrutz, espe-

daUy if you have been told to call the fusion heat.
The rest of tire problem lies in vocabulary. Mildly hot objects

TOUCH BLENDS

509

can feel only warm. Hotter objects may arouse paradoxical cold
witli warmth, and small wonder is it if some persons learn to callthe resultant perceptual fusion heat. The object is actually fairlyhot (45°-50°C., say). If the temperature is above this narrow
range, pain is elicited; since obviously that object is hot too, every-

one calls it hot. If Alrutz had been content to call the fusion stick,then he never would have had Jenkins upon his back,and he would have been quite free to add that the stimulus to thelet us say,‘sticking’ quality may

be a fairly hot object that stimulates bothwarm and cold spots, and is even sometimes called heat. The words
that people use about perceptual fusions and patterns are some-thing different from the facts of sensory fusion,

Touch Blends
The perceptual world of touch presents us with many stablefusions, blends, spatial patterns and temporal modes of change, allcomplexes which represent special objects, like metal or doth, or

spedal secondary qualities, like roughness, hardness or stickiness.

Heat and burning heat, as we have studied them in the last section,
are such perceptions. So also are the organic patterns, like hunger,
suffocation and effort, which we shall consider in the next chapter.

Table XIII lists, in addition to four thermal complexes, nine ofthese cutaneous blends and patterns which have been subject toexperimental analysis. Those perceptions are, of course, the modern descendants of the contents of Weber’s old Gemeingefiihl,

now at last brought under analysis into the elements of the Tastsinn.
This particular series of studies, undertaken almost entirely atCornell, starts off with Bentley’s synthetic experiment for the per-ception of loet, It is easy in most of these blends ( except perhaps in

the fusion for hot; vide supra) to note introspectively the involve-

ment or absence of the classical tetrad: pressure, pain, warmth andcold. It is also easy to apply common knowledge of the nature of
the objects perceived in specifying spatial, temporal and intensitive characteristics for the stimirlus.

Hard objects ought to yield

more pressirre than soft; wet objects should be moist. Such ananalysis may, however, be in error. Not only is the mere listing of

qualitative components never enough, but the analyst’s attention

may go to the wrong aspects of the stimulus. Thus a synthetic checkupon analysis is needed. To make this point Bentley undertook in

TACTUAL SENSIBILITY

510

1900 to synthetize wet. Introspection analyzes wet into pressure

and cold. Bentley asked: can wet be synthetized merely from apressure and a cold? Trying out a great variety of cold, warm andthermally indifferent pressures, he came to the conclusion that apressm'e, to be perceived as wet, must always be cold, and that it

must also be as uniformly distributed ovei' an area as is the actualpressure from a liquid, Cold cotton does not give a very convincing wet, but cold liquid does. At first it seems bke begging thequestion, to say that liquids feel wet. Of course they do. Bentley’scontribution lay, however, in his discovery that a dry cold liquid
feels just as wet as a moist cold liquid; moisture is not essentid tothe perception of wet. His diy liquids Bentley got by covering thefinger with a tight-fitting thin rubber membrane or with lycopo-

dium powder, and then immersing it in cold water. If moisturewore essential to wetness, then the membrane or the powder, since
they keep the finger dry, would prevent the perception.

Except for Miss Murray’s analysis of ticlde (1908) into an instable, spreading pattern of light pressures plus unpleasantness andthe kinesthesis of the reflex tendency for withdrawal, Bentley’s

experiment was not followed up until America ielt the inJluoneeof the Germans’ concern with perception—that concern whichre-sulted in the Gestalt school Then in 1922-1927 Titchenor, facingtire

new perceptual problems and convinced that the old four con-ventional qualities must still constitute the bases of description,

put his students

—

^for

the most part Miss Sullivan and Zigler'—onto the synthetizing of seven of the perceptions listed in Table XIII.
It is impossible to retail here the various ingenious devices which

they contrived for controlling the stimuli in order to duplicate theseperceptions. The table shows tire gross analyses tirat resulted.

We

may mention a few special matters.
Tung (1921), Bershansky (1923) and Sullivan (1923) aU confirmed Bentley on tire finding tirat wet is pressure and cold. Miss
Sullivan, studying especially the series from liquidity to solidity,

argued that temperature is most important at the liquid end andpressure at tire solid end. The nature of this series she indicatedby listing twelve points on it: vaporous, wet, oily, gelatinous, slimy,
greasy, muddy, mushy, soggy, doughy, spongy, dry—a list of ai
jectives which indicates how great may be the task of phenomenologizing the Geme»nge/uW,

The movement of the stimulus in relation to the skin, either ac-

Bl

Touch

Xm.

TACTUAL SENSIBILITY

512

lively or passively, is important.

A hard object (Sullivan) is not

smooth to tire finger, unless it moves in relation to the finger(Meenes and Zigler). Roughness, stickiness and probably oUinessalso require movement.

The table is, however, almost a caricature of these studies because

itsperceptions are not simple qualitative blends, but

complex temporal-spatial patterns. Take clamminess (Zigler). It
is essentially a cold softness perceived

with movement and supple-

mented by unpleasant imagery. An objective attitude by the perceiver kills the imagery and thus the perception. Sullivan, however,

had found that softness without movement involves warmth. Is
there thus warmth as well as cold in clamminess, and would such

warmth and cold make heat? (Cf. items 8 and 13 in the table.)
Seemingly not. The warmth becomes unnecessary to softness whenthese other' factors arc introduced.

There would seem to be no question about tlie scientific importance of this type of perceptual analysis, for if all tactual perceptions can be reduced to spatial-temporal patterns of the fourbasic qualities, then tlrere is no need to look for more than fourkinds of cutaneous receptors or more than iour alloreut systems.
Nevertheless, the job seems now to have been pushed fat enough.

Since Titohener’s death iir 1927, interest in the reduction ol the

many kinds of objective perceptions to their basic afferent components has almost disappeared, and the phenomenologisls of the
Gestalt school have taken over. They have pirblished two elaborate

accounts of the phenomenology of touch; one in 1925 is by Katz

and another in 1938 by Edvesz. Katz, consistent with his earlier
work on color (1911), distinguished the modes of appearance ofthe touches; surface touches, unlocalized touches (analogous tofilm colors), volumic touches, and the mediately perceived sur-faces ( like the paper at the end of the pencil ).( For the analogous

phenomenology of color, see pp. 135, 255 f. ) Revdsz’s phenomenology, drawing especiafly upon the space perceptions of tlie blind,

goes broader and includes all of somesthesis. The importance ofsuch phenomenology only the future can decide. It was many
years before Puildnje’s comparable descriptions of visual phe-nomena became the basis of important chapters in the psychology
of vision.

NOTES

513

Notes
Only

has

recentlyavailable a thoroughthere been
handbook forthe tactual sense: E. von Skramlik,

Psychophysiologie

derTastsinn^Afch, ges, PsijSwl, Ergbd. 4, 1037,

955 pp, {1-510 for the skin).
There are a number of good chap>
handbooks, of whi^
the two best (as of their dates) are
C. S. Sherrington in E. A. Schafer^sters In earlier

Text-Book of Physiology, 1900, II,
920-1001, and T. Thunberg in W.
Nagel’sHandhuch derdes Menschen,III,

Physiolog^e

1905, 647-733.

ein

Generalsinn.”

It

a

is

Two

papersfollowing

tliat,

Weber, argued for the identity or
the pressure and temperatiu'e senses,
are A. Wunderli (an address paraphrased by A. Pick), ExperimenteHe Bdtiagc zur Fhysiologie desTastsinnes, [Moleschott’s] Vntersneh-

tmgen zur Naturlehre des Menschen und der Thiere, 7, 1860, 393400, esp. 394-396;

M.

Szbadfoldi,

Bcitrage zur Physiologie des Tastsinnes, ibid., 9, 1865,

624-631, esp.
Lehrhuch der

A good, briefer but more recent,625 f.

En^isb chapter

Physiologie des Menschen,

is

in

L.

Luciont,

distinct

general capaci^, not a special sense.

J.

M.

Schiff,I,

1858,

Human Physiology, IV, trans. 1917,^7-262, gave an elaborate discus-

1-56.

sion of conduction of pressure

pain inTactual Differentiation

tluit

pre-eimerimental

and

early

tile

and

spinal cord, concluding

tractsareseparate.

The

support for the
separation of pressure and temperafirst

The

tlie

authoritative

The experiments of E. H. Weber
bedn in liis De piilsu, resorptionB,

was agreed upon by Funkeand Hering in their related chapters In Hermann’s Handhuch! 0.
Funke, Der Tastsinn und die Gemeingeftihle, in L. Hermann’s Handbuch der Physiologie, HI, ii, 1860,
208-414; E. Horing, Der Tempera-

auditu et iaciu: annafniiones ana-

tursinn,ibid.,

tomicaechapter

contains

experimental history of tactual dif-been given by K.
M. Dallenbach, Fain: history andresent status, Amer. J. Psychol., 52,
939, 331-347.
ferentiation has

physiohgiae, 1834, esp.
44-175 {De taciu), but the classicalelpaper which drew attention and ex-ture41^30.
his

Heiing’s

theoryofwarmth and cold as dependent
upon antagonistic processes, analo-

erted Influence was his Der Tastsinn
und das Cemeingefiihl, n chapter^us to Ills color theory. A. Herzen,

in R. Wagner’s Hnnatoorferbuch dertursinoes In zwei gesonderte Sinne,

481-588
1851 and
1905). As to what Weher meant bySinn, we may note the opening sentence of his later paper on the twopoint threshold and the error of
localization, a paper in which hehad substituted the term flawm^inn
for Ortslnn; Ueber den Raumslnn

Arch.

Physiologie,

III,

ii,

1846,

(reprinted separately inund die Empflndungskreise in derHaut und Im Auge, Ber. sHchs. Ges.
Wiss. Leipzig, math.-pbys. Cl., 1852,

85-164.

The

Haiunslnn

Istsentence reads:"Derbesondere

Sinn,

ein

aber nlcht ein Specialslnn, sondem

Ueber die Spaltung des Temperages.

Phtjsiol.,38,

1885, 93-

103, esp. 94, argued for the inde-

pendence of warmth and cold, presumably without knowing of Biix’s
and Goldscheider’s finding of separate spots.

The original papers of M. Blix areE^^erimentela bidrag till losning af
fragan om hudnerveras speclflka en-

Uppsala Ldkfdren. Fdrk, 1
1882, 87-102; 18, 1883,
427-440. The first paper was pubergies,

ser.,

18,

1882 in the
1882-1883 voL, and is generally fnconectly given as 1883,^ecause thelished as of October,

TACTUAL SENSIBILITY

514

volime generally bears that

data.

This date demonstrates BUx’s priorhis

for

ity,

publl^ed

Energies, 1902;
i. M. Dallenbach, Fain; history andandpresent status, Amet. I. Psychol, 52,

1882,

short

first

1884. Bits failed toofcovered,paper in

1939, 831-347.

^
Germanof temperature s^ts is H. H.

dis-

until

course,translations of his papers were pub-lished in 1884, so that inGermanhe and Goldscheider were almostThesynchronous.

and the Theorypa^ wasOctober,inColdschelder’s
July,

short

first

Sensation of Fainof Specific Sense

translationsofBlix are Experimectelle Beitrage zur

Losung der Frage iiber die apei^sche
Energie des Kautnerven, Z.

Biol,

20, 1884, 141-156i 21, 1885, 145160. The first paper declares for four

The third independent discovererDon-

On the temperatui'o sense.
Mind, 10, 1885, 399-410. He was
aldson,working under G. Stanley Hall in
America’s first founded psychological laboratory at Johns Hopkins.

M. von Frey’s four classical paare; Beitrage zur Physiobgie
des Schmetzsinns, Ber. sacks. Ges.

persmath.-phys.

Wise.,

Cl.,

1894,

40,

and mur kinds of spots;
the second rejects pain spots andSinnesphysblogle

pain os a modality.

47, 1895, 166-184; Untersudiungenmodalltica

185-196,283-296;

Beitriige

zur

Haut,

ibid.,derA. Goldacheider are Die spezifisoire Energie
der Temperatunmrven, Monatshe/teUber
db SinnesfuncLtonen dermenschlichen Haut; Druckempfindung und Schmerz, Abhandl sachs.

prak, Dermatol., 8, 1884, 198-208,

Ges.

The

initialpapersofWiss.,

malli.-phys.

Cl.,

23,

Energie

1898, 175-206. The nrst two papers

der Gefiihlsnerven der Haut, Ibid.,(1894) insist on pain spots; thetiiird (1895) Is die argument forDie

225-241;3,

speziflsohe

1884, 283-800; Uebet

Kalte-

WStme-,
und Druckpunkte, Verhandl,

physiol

Gesell21-26.

These are respectively

Berlin,

1885,

10,

re-

printed in his Gesammelte Ahhandlungen, 1898, 1, 53-78, 77-93, 100-fourorgans

’Die

E

nerve

sadien fiber dio Hautsinnesnerven,suchungenArch. Physiol Leipzig, 1885, Suppl-

weiseBd., 1-110 (Gcs. Abhandl,

I,

107-

218). His final view for pain as asummationofintensive

sensations

appears in J. Gad and Goldscheider,U^er die Sunnnation von Hautreizen, Z.

Win. Med., 20, 1892, 339-

(Ges. Abhandl, I, 397-482),
and in Goldscheider, Ueber den
Schmerz in physiologisoher undwhoesperimenterswarm andGoldscheider

modalities

and pain Ilmens.

acknowledges
Blix’s priority, of course. In these
he was against pain as amodality, but in his full account he acc^led it; Neue That108.

four

for

(paiadoaloal cold, pp. 172 f.); ilia
fourth (1896) is on lire pressure
excisedand foundand free endings, but

coldfibersspots

no coipuscles or special endings, are
Donaldson, op. oil, 1885, 408f.; A.
Goldscheider,

Histologische

liber

die

Unter-

Endigungs-

der Hautsinnesnerven beim
Menschen, Arch. Physiol Leipzig,
191-231
SuppL-Bd.,(re1886,
printed in Gesammelte Ahhandlunr
gen, 1898, I, 219-249); G. HSggqyist,

Histophysiobgischefiber dieStudienTemperatursinne der Haut373

des Menschen, Anat. Anz., 45, 1914,

kUnischer Hinsioht, 1894, esp. 3-36,

48-63, esp. 57; K. M. Dallenbach,
The temperature spots and endorgans, Amer. J. Psychol, 39, 1927,

for the rest is clinical (not in Ges.

402-427; C. R. Pendleton, The cold

Abhandl.). In this connection, see

receptor, Aid., 40.

a later review dr the literature andDallenbaoh, whose enthusiasm Is re-ulthnate

defensetheory of pain: A.

of
J.

the

Intensive

MoKeag, The

1928, 353-371.

sponsible for the rediscovery of lliis
lost’

paper of Goldscheider’s,

dis-NOTES

515

A bibliography

cusses this matter in

Two-Point Limenof tbe attempts to identify the func-

andThe classical exposition and standard secemdary source for the work

Sherren cot the two nerves inHenry Head’s arm on April 25,
1903. The papers are II. Head,W. H. R. Rivers and J. Sherren,
The afferent nervous astern from a
new aspect, Brain, 28, 1905, 99-

in the nineteenth century on boththe two-point Ilmen and the error

end-organs

tionalcoldofwarmth, ibid,, 41, 1929, 344.

of localization

Ueber

V. Henri,is

Baumioahmehmungm des Tastsinnes, 1898. Much less general andon the two-point limen only is M.
die116, reprinted in Head, Studies inFoucault, Lulusion paradoxale et leNeurology,

1920, I, SS-65, but
without ^e plates; Rivers and Head,seuil

A human experiment in nerve-divi-

see his opp.

Brain,

sion,

1908,

31,

323-450de Weber, 1910.
For E. H. Weber on the Orfsinn,

IlandviMerhuch(Studies in Neurology, I, 225-329).

Wagner’s

The later paper is me tliorough ac-

Physiologle, HI,count; the first establishes the date.

also,

In general, sec Studies in Neurology,

tile furtherI,

and for a long

tor these

Head and

paper byclinicalandII, 810-832, for references to Head's
critics, including von Frey, and for
Head’s trenchant criticism of his
critics. The first two experimental
papers, which verified Head’s mostSherren,De pulsu, resorp-

citt.:

Hone, audllu et tactu, 1834, 45-81;

ii,

der

1846, 524-543;

method” andfor his "second

discussion of sensory cir-Ueher den Raumsinn und die
Empfindungskreise in der Haut undcles,

bn Auge, Bar.

sdehs,

math.-piys.

1852, 85-164.

For

Cl.,

toe

Ges.

systematic

first

Wise,,

workwith successive stimulation and theevidence that the Ifanen grows larger

Important findings and rejected biswith the growth of the organism, seeinterpretation of them, are W. Trot-

T.

ter

and II. M. Davies, Experimental
theof

innervation

theStudiesinshin, ].

thyHol, 38, 1909, 134-146;

G. Boring, Cutaneous sensation

E.

after nerve-division, Quart. J. expet.

Physiol,
the

10,

1918,

discrimination

On how

1-95.
of

two

pointsmay be mediated by deep sensibility, see Boring, The relation of
the

limen

of

dual

impression

toHead's theory of cutaneous sensibility, Proc. VIII Internet.
Congr.
Psychol, 1923, 57-62.

N. Czermak, Beilrage der Fhysio-

logle

Tastsinnes,

desSitxungsber,Weln, matb.-phys. Cl.,
IS, 1855, 466-521; reprinted in his

Afaid. Wtss.

Gesammelfe Schriften, 1879, 1, 303353,
K, Vlerordt discussed longitudinaltransverse limensvs,and first men-tioned the law of mobility in Ueber

Ursachen der verschiedenen
Entwickelung des Ortsinnes derHaut, Arab. ges. Physiol, 2, 1869,
297-306. He developed tiie law ofmobility in Die Abhiingigkeit derdiedes Baumsinnes derden Beweglichkeit der
XBrpertheile, Z. Biol, 6 1870, 53-

Ausbildung

Haut vonSpace Perception,

The

questionoftactualspace

perception in connection with nativ-

ism

and

theoryof72.

For A.

Goldschelder's

small

li-

empiricism

andLotze’smens, see his Neue Thatsaobeu liber

local

has

alreadydie Hautsuinesnerven, Arab. Physiol

signs

been discussed, in Chapters 1, 2 and 7(pp. 29-81, 79-82, 226-228, 234-

Leipzig,

1885,

reprinted

in236). Thanks to Weber, the study ofhandlungen, 1898, 1, 194-196. For

tactual space came early, before thethe spatial

study of tactual qualities.

sure spots by successive stimulation.

Suppl,-Bd.,his

84-87,

Gescmmelte

discriminationof pres-TACTUAL SENSIBILITY

516

Metener,son influence sur la sensibility cuta-

Die Haumschwelie der Haut bei Sucoesslvreizung, Z. Psijchol, 29. 1902,

nde. See. mid. suisse Bsmande, 16,
1896, 712-751; Henri, op. cit., 33-

181-182.

35;

M. von Fiey and R.

see

On the paradoxical twos (Vexif-

Friedline,

op.

cit.

esp.

infra,

415-419.

Kottenkamp and H.

On savage and ciwlized limens,

Versuohe iiber den Raumsinn der Haut der oberen Extremitat, Z. Biol., a. 1870, 37-52; W.
Camerer, Versuohe uber den Raumsinn der Haut nach dec Methode dersee W. McDougall, Reports of Cam-fehler) see R.
Ullrich,undbridgeAnthiopologicalto Torres Straits, II.

il,Expedition
1903, 189-

193.

On sensory categories under dual

falschen Falle, Ibid.,

stimulation,

see

Kottenkamp

and280-300; V. Henri andTawney, Ueber die Trug-dt.;

Camerer, op.

cit,,

rlchtigcn
19.

1883,

Ullrich, op.

G,A.

1883, 282; Foucault, op. cit., 124 f.;

wahmehmung

E.

der

the limens of single and dual Im-

zweier Punkte bei
Berubrung eines Fuuktea derHaul, Phil. Stud., 11, 1895, 394405;

M,

doxale etFoucault,

Vllluslon para-le aeuilde Weber, 1910,

The determination ofGates,

J.

pression by the method of constantstimuli, Amer.

152-157.

Psychol, 26, 1915,

1.

On the utilization of dif-

13-118 ( history ol paradoxical judg-

ferent sensory categories as the crl-

ment, 13-28); M. ffinoald, An analysis of the psychometric function for

terton for duality, see E, B. Titch-

On ethnological tests of sen-ener.

and perception withthe two-point limen with respect tosationthe paradoxical error, Amer. 7. Psy-

reference to the tests of color vision29, 1918, 227-232; E. G.
Boring, Cutaneous sensatian after

and

chol,

Quart.

nerve-division.

expet.

1.

Physiol; 1-95, esp. 93.

On reduction of the Ihnen with
see A. W. Volkmann,
Ueber den Einfluas der Uebung auf
das Erkennen raumlicher Distanaen,

praotioe,

tactile discrimination

the

in

reportsofthespecialdescribed

Cambridge

Anthropological Expedition to TorPfoc.

Amer, phtl

res

Straits,

55,

1918, 204-236,

esp.

Soc.,

206-215;

L. Friedline, Discriminadon ofC.

cutaneous patterns below tire twopoint limen, Amer. J. Psychol, 29,

The

Ber. sdohs. Oes. Wise., math.-phys.

1918, 400-419; E. G, Boring.

Cl, 10. 1858, 38-69; W. Camerer,
Veisuche uber den Raumsinn der

stimulus-orror, ibid., 32. 1921, 449-

471, esp. 465-470.

Haut bei Endera, Z, Biol, 17. 1881,
1-22; G. A. Tawney, Ueber die

Wahmehmung zweier Punkte

Error of Localizationmit-

des Tastsinnes, mil Riloksicht

For a thorough discussion of the

Frage der Uebung und
Entstehung der Vexirfehler,
Pha Stud; 13, 1897, 163-221; V.

research on the error of localization,

telst

auf

die

die

Henri,

Ueber

die

Ratirmahmeh-mungen des Tastsinnes,
36;

Friedline,

op.

dt.

1898, 23Infra,

esp.

413-415.

On the increase of the limen withfarigue,

see

BeziehungenEimudunemogen daUiinchen,Vaiuiod,H,

Griesbach,Uebergeistiger
zwischenund Empflndungsr'erHaiit,

24,

Arch.

1895,

Hygiene124-212; T.

La fatigue intellectuelle etsee V. Henri, Ueber die Saumuiahr-

nehntungen90-141.

desTastsinnes,

1898,

Tills is E. H. Weber's “second
meUiod," and it is given briefly withthe results in his Ueber den Raumsinn und die Empfindungskreise inder Haut und ira Auge. Ber. sSohs.
Ces. Wiss; math.-phys. Cl, 1852,

85-164, esp. 87-89. The fact is that
W. Volkmann, in his investiga-A.

tion of vision,

had used a form of

the method earlier in order to study

NOTEStherelationoftactuallocalization:

see

his

dibcussioninHandwHrterbuch der

Wagner’sR.

visualto570-572.

Plujsiologie, II, 1844.

of

knowi

sensory

circlesbecame1846.

Weber’ssecondInmath.-naturwiss.

577-600,

1855,

esp.

Cl.,

370-391,I.

374-376;esp.

The two-point limen

E. G. Boring,and the error of localization, Amer.
Psychol, 42, 1930, 446-449; M. ].

J.

The eroerlmental relation of

method and his furtlier discussionof the Kaumsinn were published in
1852, which was also the year inwhich R, Lotze, Uedidniscfie P^chologiet 1852, 325-435, put out

Zigler,the tlieory of local signs. Lotze dis-lion

cussed the relation of sensory circles

see Pillsbury, Parrish, opp.

to395-410, and Czer-

local signs,

mak,

dt.

op.

largely

in/ro,

concerned

1855,

with

was

bringingW^jer and Lotze into relationdiip.
See pp. 233-237 on the empiricistic

and nalivistic theories of space
which grew out of Lotze’s original
genetic

the two-point limen to the error of

1935, 316-332.

On the displacement of bcaliza-

H. Aubert and A. Kammler,
iiber

und Raumsinn derden Druck[Mola-llaut,

W.

Lewy, Experimentelb UntersuchUDgen iiber das Gedachtnis, 2, Psychol, 8. 1895, 231-292, esp. 254^
292, and on this particular point,
277-281; M. Ponzo, R6cherches surla localisation des sensations tactiles
et des sensations dolorifiques, Arch,For the fact that the error ofchanges with modality,

localization

gettingcoldSalargerpain,

pressure,

and warmth(in that order),de b localisation

zur

Na-

see Ponzo, fitudederdes sensations thermiques de chaud

Vfitersucliungen

turUhrs

desThere, 5, 1858, 145-179, csp. 176Henri,

Rficherches

dessensations,

localisation

orientation,

Mensclm undschotl’s]V.

toward points ofital Biol, 55, 1911, 1-14.

dieory.

Untersucliungcsn

179}

general Psychol, 18,

lociilization, J.

The other important papers cited
are:

17,

582-584, re-printed in his Gesammelte Schrrften,
1870,

Weber’s first metliod and die concept

517

Weln,

sur

la

de

et

froid,

Arch,

iial

Biol, 60,

1918, 218-281.

Arch.

norm, pathol, 5 ser., 15,
1893, 619-627; Rccherches sur la

Thyslol

localisation

desAnnec psijchol,sensations2,

1895, 168-192;

W. Baitli, a Russian paper,

1894,

which Henri cites and translates as £tudes de la sens du lieu
et sur la mSmoire de ce sens; W. 6.
[n.v.],

Fillsbury,

Stimulation

tactiles,Some questions of cutane-

ous sensibility, Amer. J. Psijchol, 7,
1895, 42-57; C. S, Parrish, Localiza-

For C. Meissner on cutaneous deformation as the stimulus to touch,

Untersuchungen uber den
Z. rat. Med,, 3 ser,, 7,
1859, 92-118. For M. von Prey on

see

his

Tastsinn,

the pressure stimulus, see hisUn-tersuchungen iiber die Sinnesfunctionen
der
Haut:
menschlichen
Dnickempfindung
und Schmeiz,tion of cutaneous impressions by
amr movement without pressure
upon the skin, ibid., 8, 1897, 250-

Abkandl. sdohs. GeseU. Wiss,, math.pbys. CL, 23, 1896, 175-266, esp.

267.

223-237

On the argument that the error ofequivalent(specifications
hairs,

forthree

229 f.); Beitrage

would necessarily be a

zui Sinnesphysiobgie der Haut, Ber.

a quarter of the two-point
limen because of the relation of themethods, see J. N. Czermak, Weitere Beitrage zur Physiobgie desTaslsinnes, Sitsungsber. Akaa. Wiss.

sQchs. GeseU. Wise., math.-phys. CL,

localization

third or

1897, 462-468; suad von Frey
and F. Kiesow, Ueber die Function

49,

der Tastkoiperchen, Z. Psychol, 20,
1899,

126-163, esp. 143-155.

The

TACTUAL SENSIBILITY

518

last article Is the fullest and tlie onethat all the texts dte.

The

term

Psychol, 49, 1937, 1-22, esp. 13Studies in thermal sensitivity:

15)

pres&ufe'gradientminor ooutiihutions,exper.

1.

Psy-(Dmclge/sBe) was first used by
von Frey and Kiesow, op. flit., 15015S, although they had mote to say
about defoimation and the conse-

chol, 22, 1938, 178-185, esp. 178 f.
W. L. Jenkins’ theory of tiro re-uent intiacutaneous tension. The
that a pressure-gradientisproduces deformation which in turn

adaptation withSleoryproduces tension, and texts in citing

von Frey rm
have sometimes spoken of the presthe pressure stimulus

sure-gradient, sometimes of deformation,Onout infrequently of tension.
the nature of the thermal

An Essaystimulus, see John Locke,

Human Understanding,Concerning1690,% Chap.

Bk.

sect.

8,

21

(which should be taken in context
with thediscussion

secondaryofversible reaction in the receptor

a series of small
annular stimulators. 1. exper, Psychol, 22, 1938, 164-177, esp. 172177. For Nafe’s vascular theory ofthermal sensation, seeof warmth, cold andPsychol, 2, 1036, 421-431.

experiences
heat,

J.

For M. von FVey on pain, see his
two opp. citt., esp. the second

first(1895), in lire early section of tliis
iapta-’s notes, Tactual Differentia-

On the use of radiant heat to

tion.

1846,

pain:

a

100 f.i K. Vietordt,
Gmndriss aer Flit/siclogie, 2 ed.,(where he accepts
1862, 241 f.
Weber's view)i 4 ed., 1871, 301 f.
(where he objects to Weber’s viewpainthreshold)spatialsummation oftire)!

sinn,

in

E.

buch der Phi/smagie,
100-110,

III,

ii.

esp.

and gives his own)) E. Bering,
Gtundzuge einer Theorie des Temperaturslnns,
Silaungsber,
Akad,
Wise, Wien, math.-naturwiss. CL,
101-135
(the
(S),
75
1877,
thorough paper)) Der Temperatursinn, in L. Hermann’s Hartdbuch
der Phusiologie, IH. ii, 1879, 415439 (briefer and more conven-

D. Hardy, II. G.
J.
Goodale, Studies on
method for measuringelicil pain,

see

Wolff and

II.

new

on

observations
pain,

J,

din.

19, 1940, 849-657) Wolff.
and Goodale, Studies on
paint measurement of the effect ofmorphine, codeine and other opiates on the pain threshold and anal-

Incest,,Hardyysis of their relation to die

pain ex-perience, ibid,, 19, 1940, 059-880)

G. A. Schumacher, Goodale, Hardy
and Wolff, Uniformity of fte pain
threshold in man, Science, 92, 1940,
110- 112.

tional)) C. S. Sherrington, in E. A.

Schafer’s

Nofe,

F.

J.

Handbook of General Experimentd
PsyAobgy, 1934, 1047-1049, 1058KBB) Nate and K. S. Wagoner, The

general. Chap. 8 enH. Weber, TemneralurllandwBrterWagner’sin R.

qualities

isin his Studies in thermal sensitivity:

Weber Function

Text-Book of FhysUihgu,

1900, n, 950-954.

On paradoxical cold, see M. vonFrey, Beitrage zui Sinnesphysiologie

W&.,

For Weber on the Weber fraction, see E. H. Weber, Z>e pulsti,
etc.

(op.

flit.),

1834, 86-92,

132-

math.-phys. O., 47, 1895, 155-184.
On the verification of this phenome-

159-101) Der Tastsinn und
das Gemeingefuhl, in R. Wagner’s
HandwSrfermoh der Physmogie,

non by five other lirvestigators, seeHI,

der Haut,

L. Lucianl,Ber.

sSohs.

Ges.

Human Physlolagy, IV,

1917, 83) but Jenkins failed withnaive observers etc get confirmation

142,

ii,

1846, 546-549(

98-100in

the 1905 reprint).

For the early determination of thein most cases: W. L. Tonkins, Adap-

Weber function for what was reallydeep pressure, see the data of W.

tation in isolated cold spots, Atner.

Biedetmann and L8wit, publishedNOTES

519

by E. Bering, Zui Lehre von deradaptation on the temperature dif-Bezlehung zwischen Lelb nnd Seele,
Sitzmgsber.
Wetn,
Akad. Wiss.

ference Ilmen, Psychol Momgf., 16,matli.-naturwiss. CL, 72(

1914, no. 2.

3), 1875,

310-348, esp. 342-345. The text
does not mention Stratton's classi-

Slimmation

cal paper for the reason that he used

On summation of thermal stimu-

weightsfromvarying

10

to

200

und

sinn

ing a function for deep pressure.

cit.),

Working

Wundt's laboratoryinatLeipzig, he Invented, for the controlled successive application of two

finished form

the

Drucktoege that inthepressures,isE, H. Weber, Dec Tast-lation, seegrm. and was mns really determin-

dasCemedngefuhl(op.

1848, 553 f.; S. E. Barnholdt
and M. Bentley, Thermal intensify

and the area of the stimulus, Amer,
Psychol, 22. 1911, 325-332; J, D.
Hardy and G, W. Oppe], Studies in/.

seen in so many oftemperature sensation: the sensitiv-

See G. M.

ify of the body to heat and the spa-

older laboratories.

Stratton, Ueber die Wahrnehraung
von Druckanderungen bei versehiectenen Gesohwindigkellen, PM. Stud.,12. 1890, 525-580, esp. 535^38 forthe tables.

summation of the end organ re-tial

sponses,1937,

On pain as sununation, see the
on

notes

For the Weber function as de-cUn. Invest., 10,1.

533-540.
TactualOiSerentistion,

termined with van Frey hairs on

D. Hardy, H. G.
J.
Wolff and H. Goodale, Studies on

isolated pressure spots, see F. Kie-

pain: asow, Ueber die taktile Unterschieds-

pain threshold; observations on spa-

empfindlicbkeit bei snczessiver Helz-

tial

ung

vest.,

Empfindungsorgane,
Psychol, 43, 1922, 11-elnzeluarArch. ges.

23

(p.

16 for the data of Table

XII)j Zur Frage nach der Gtilligkeit

desWeberschen Gesetzes im

Gebiete der Tastempfindung, ibid.,47,

1-13; A.

1924,

Gatti

and

R,

supto. See also

new method lor measuringsummation of pain, J. cUn. In~
19,

1940, 649-057.

For summadon of adjacent pressures and inhibition of somewhat
more remote pressures, see A. Bnickner. Die Raumschwelle bei Simultanrelzung,Z.

Psychol, 25, 1901,

83-60, esp. 38-47.

Dodge. Ueber die Unterschiedsempbei der Relzung eines

findlichkeit

Adaptation

elnzelnen isolierten Tastorgans, ibid.,405-425On thermal adaptation, vide supra(p. 400 for thedata in the table). For a comparisonof tliese functions with others fromunder Stimulation and Weber's Law;other departments of sense, see A.

tion

09, 1929,

orlminatian, Psychol Rev., 43, 1936,

and for the history of experimentaon it, see E. Gertz, Psychophysische Unlersuchungen uber die
Adaptation im Cebiot der Temperatursiim nnd Uber firren Einfiuss euf

322-340.

die Reiz-

H. Holway and C. C.
Weber-ratio

for

Pratt,

The

intcnsitivedis-

On the Weber function for temperature,see

G, T. Fechner, Eie-

mente det Psychophysik, 1800, I,
201-210 ( the experiments were performed in 1855); II. Nothnagel,len, Z.

und UnterscbiedsscbwelSimesphyslol, 52, 1921, 1-

51, 105-156, esp, 1-18; also Abbott, op. cit. (in the preceding section), 1-7.

For die papers oiled in

the text, besides Gertz and Ahhott,m iso-

Beitriige nir Physiologle und Pathol-see W. L. Jenkins, Adaptation

ogie des Temperatursinns, Deutsch.

lated cold spots, Amer. J. Psychol,Arch. Bin. Med., 2, 1867, 284-299,

49. 1937, 1-22.

esp.

287; E.

Abboth The effect of

On adaptation to pressure, see M,

TACTUAL SENSIBILITY

520

von Prey, Unlersuohungen iiber die
Sinnesfunotionen dei mensoWicbeii

ungen undHaut. Ab}iandl. sSchs. Gesell Wiss.,
math.-phys. Cli, 23, 1896, 175-266,
esp. 177-188 (Die Waliinelimungesp. 442-471; Il.tyos, op.

andaueindet Belastung); F. Kiesow,
Sur I'exoilation du sens do pression
produite par des diformations con-de la peau. Arch, itah Biol,
417-442| M. J. Zigler,
Pressure adaptation-lime! a functionof intensity and exlensity, diner. I.
Fsychol, 44, 1932, 709-720.

Gediichtnisbilder, Arch,

Physiol.,

gee.

110,

437-491,

1905,

oil.;

P, L.

Dimmick, On cutaneous nfter-Lnages,
Amer. J. Psychol, 27, 1916, 586'
571; H. T. Holland,On the 'after-

sensation' of pressure,I.

exper. Psy-

chol, 3, 1920, 302-318,

stantes

26,

1896,

On

Heat
For von Frey on paradoxical cold,
see the notes on Tactual Differentia-

see

E.

tion, supra.

analysisof

Psychol, 19, 1908,

S. Alnitz first published a paper
confirming von Frey on tlie inde-289-344, esp. 304 f.j H. H. Strauss
and R. F. Uhlmann, Adaptation topendent specificity of the warm andcold spots ( he began his research inadaptationA

Murray,pain,

qualitative

tickling, Amer. J,

superBclal

to

pain,

ibid.,

30,

1919,

April,sen,

2,

trans.,

excellent Iiistory of the experi-mental psycholoOT of after-sensations
is given by M. if. S. Hayes, A studyof cutaneous after-sensations, Psychol Monogr,, 14, 1912, No. 3, 1-

29 (bibliography of 39 titles, 87The important experlnionts
89).
mentioned in the text are: II. Kottenkamp and H. Ullrich, Versuche
iiber

den Raumsinn der Haut deroberen Extremitilt, Z. Biol., 3, 1870,
87-52, esp. 41| V. Uibantschitseh,
Ueber den EInfluss von Trigeminus-

Eeizen auf den Tast- und Temperaimsinn der Gesichtshaut, Arch. ges.
41, 1887, 46-69, esp. 61,
65 f.j M. Dessoir, Ueber den HautPlij/sIoZ,,

sinn.

till

Iciinnedo-

hudens kail- och vatmpunktei, Uppsala Liikfuren, Path., 2

After-Sensations

An1896): Biding

men om422-424.

Arch.

Physiol Leipzig,

175-389, esp. 195;

J.

Germanund VMnno-

246-263;
Kaltc-

porimcnlal contributions towards ourknowledge of the cold- and warm.skin, Mind, 2 ser., 6,

spots of the1897, 445-443. His theory of hootIsin hisOm fflrnimmclson “hett,”

Uppsala Ldkforen. Fdrh., 2 ser., 2,
1807, 840-359; German irans., Die
Hitzeempfindung. Skond. Arch. Physiol, 10, 1900, 340-352; Eng. abstract, Tile sensation '7iot,” Mind,
2 ser., 7, 1898, 140-144. For the
diagram of die thermal series ofperceptions (Fig. 84), see M. vonFrey, Vorlesungen Iiber Pliuslologie,
1904, 313,

T. Thunberg onttoated Alrutz in

1892,

Gad and A.

1898,

Zu dennnklen, Skond. Arch. Physiol, 7,? 897, 321-341; Eng, abstract, Ex-

the study of the effects ofwarm-

Goldseheider, Ueber die Summation

cold sttoiulatlon; FBmbnmelseme vidvon Hautreben, Z. klin. Med., 20,
1892, 339-373 (in Goldsoheider’sGesammeke Abhimdlungcn, 1898, 1,
397-432); T, Thunberg, Untersuohungen uber die bei einer einzdnan momentanen Hautreizung auftietenden zwel stechenden Empfind-tillungen,

12,

covered independently by E, Rubin,394-442, esp. 432-438; Ur-

Beobachtungen fiber 'Temperatuicmpflndungcn, Z, Sinnesphysiol, 46,

1902,

Sfeind, rArcli.

bantschilsch,

Physiol,

Ueber SinnesempBnd-

saminastlillelokalisciad,sam-tidigt pkg&ende kSld- ooh vStmeret-ning, Uppsala Lakfdren, Fdrh., 2 ser,,1,

1396, 489-405 ( ilie picture of thegiill is on p.

489).

Alrutz Med to discover paradoxical

warmth and failed. It was dis-

NOTES
1012. 388-393, esp. 302 f.. and by

521

warm -f cold

stimulation,

J,

eas,

The

Emp-

PsijM,

22,

1938, 451-481;

flndung dm Hitze, Z. Win. Med., 75.

reoctionsofuntrained

1012, 1-14, esp. 4f.j Revision dersimultaneous

A. Goldscheider, Ueber die

Lehie vom Temperatursinn, Bef. V
Kongr, exp, Psijchol, 1912, 222-228,
esp.

ibid.,

warm -f cold d- shock,1938, 564-572; Further
evidence against the AI-

22,synthetic

rubs theory, ibid., 23, 1938, 411-416;

227 f.

On heat as an imperfect fusion of
warmth and cold, see F. Kiesow, Zui

Analytic evidence against the Alrutz
theory, ibid,, 23, 1938, 417-422.

For different forms of heat grills,
op. cil,, 1896; Cu-

Analyse der Temperaturempfindung,Z, Psychol,

Hacker,tosubjects

26. 1901, 230-246| F.

Beobachtimgen

an

einer

HantsteQe mit dissozilerter Empfind-ungslahmung,

Z.

Biol,

231-263, esp. 239-253.

1913,

61,

On heat asnecessarily involving rain, see Goldsclieider, op. cit., Z. kiln.

Med,, 75,

1012, 1-14.

used two-point .warm-

F. Cutolo

see Thunberg,

op, cit., 1918; N. C. Burnett
and K, M. Dallenbach, The experience of bent, Amer. J, Psychol,
38. 1927, 418-431, esp. 419; H.
tolo,

A

Schlosberg,

simpleheat

grill.

Ibid.,

43. 1931, 119 f.; G. L. Free-man,

A stmpliBed heat grill, ibid,,45, 1933, 344.

cold stimulation and also a heai grill
to make his introspective analysis ofheat as a pressure-pain quality:

Touch BlendsA

On heat, burning heat and cool,preliminary study of the psychology

peceding secHere are the references for theof heat, Amet. }. Psychol, 29, 1918,

see die notes of die442-448. E. B. Tltohener thereforetion.

placed heat belween pressure andodier perceptions.

prick in bis touch pyramid:

ModelsdcmonstraUan of

sensorythetorqualities, ibid.,81,

1920, 212-214.

L. Knight showed that pick pain is

an element in burning heat:
integration
ibid., 33.

lall

of

warmth

and

The
pain,

1922, 587-500. S. C. Fer-and K. M. Dallenbach placed

Wet as a cold pressure: M. BentThe synthetic experiment, Amer.

ley,

Psychol, 11, 1900, 405-425, esp.
414-425; S. Tung, ’The integrationof -punctiform cold and pressure,ibid., 32, 1921, 421-424; I. Bershansky, Thunberg’s illusion, ibid,,J.

34, 1923,

291-295 (after-sensations

heat between pressure and prick andof cold and pressure give an illusory

showed that prick enters into burning heat: The analysis and synthesisof burning heat, ibid., 42, 1930, 72-wet); A. H. Sullivan, The perceptions of liquidity, semi-hquidiiy andsolidity, (bid., 34,

OUy

1923, 531-541.

warm pessure:W.

N. C. Burnett and Dallenbach
worked out the formula for the intensity of heat as a function of the

Cobbey and A. H. Sullivan, An ex-

warmof oiliness. Ibid., 38, 1922, 121-127.

82.

intensities

of

tlie

constituent

asL.

perimental study of the perception

warm pressures do not,common objectivo perception; R. S. Mahnud, The

and cold: Heat intensity. Ibid., 40,
1928, 484-494. ]. H. Alston showedtliat the worm and cold stimuli can
he widely separated; The spatial

Punctiform

conditions for the fusion of warmthand pressure, ibid,, 32, 1921, 571674; I. Beiubansky, The areal andand cold

in

heat,

ibid.,

31,

1920,

integrationofpunctiform

303-312.

W. L, Jenkins’ attack upon the
Alrutz dieoiy is to be found for themost part in his The reactions of
untrained

however, yield any

subjects

tosimultaneouspunctiform

integrationofwarmthwarmthand pressure, ibid., 33, 1022, 584587,

Tickle: E.

Munay, A qualitative

analysis of tickling:its

relationtoTACTUAL SENSIBILITY
andcutaneous
ibid.,

organic

sensation,

Hard and

soft:

A.

stioldnesa,

ibid.,

H.

Sullivan,clamminess,

ness and hardness,

561.

10, 1927,

etp. Psychol.,

447-462.

J.

Zigler,ibid.,

34,

1923,

550-

D. Katz published a monograph!

Smooth and rough; M. Meenes
and M.

73-84.

1923,

mental study of the perception of

The cutaneous perceptions of soft/,

34,

Clammy: M, J. Zigler, An experi-

1908, 289-344,

19,

An experimental

Der Aufbau der Tastwelt,
chol.,Z,

Psy-

Ergbd. 11, 1925 (see esp. 21-

study of the perceptions of rough-74 for touch patterns). G. Rfo&z

and smoothness, Amer. ]. Psy-

published a two-volume book: Die

nesschol, 34, 1923, 542-349.
Sticky;M.

j.

Zigler,An experi-mental study of the perception ofFonnentoelt

dec(seo esp.

83-161 for the percep-

I,

Tastsimes,

1938

tion of space, things and forms).

Chapter 14

ORGANIC SENSIBILITYRGANIC sensibility is a loose tem used to classify events
dependent upon the excitation of receptors inside the skin—sensations from the tissues immediately beneath the skin,from the muscles, tendons and joints (Idnesthesis or proprioception), from the viscera, alimentary canal, flioracic and sexual or-gans,

and sometimes—though it is stretching a definition—the

semicircular canals. These internal ‘senses’ are subject to all thedassificatory equivocalities which we have considered in the intro-

ductory paragraphs of the preceding chapter (pp, 463 f.). Their
classification may be physiological by organ(muscle sense), func-

tional by meaning (appetite), introspective by quality (ache), or

perceptual by pattern (nausea or dizziness as analyzed into a sensory complex ) In this chapter we shall proceed by considering the.

sensibility of organs or groups of organs, treating the perceptualand functional aspects secondarily.

Deep Sensibility
In the nineteenth century, tactual and cutaneous sensibility were

thought to be identical. Warmth, cold, pressure and pain wereelicited by thermal, forceful and penetrating stimuli applied to theskin. Since a needle, loaded within the ordinary limits of toleration, pricks only the skinand since the receptors for warmth andcold lienear the surface, no great confusion could result in respectof these three senses. Pressure, on the other hand, was usually ap-

plied with loadings that brought into function a second set of sub-cutaneous receptors. All the work of the last century on the validityof Weber’s law for pressui'e, the tactual two-point limen and theerror of tactual localization involved both cutaneous and subcu-

taneous receptors. Research like Goldscheider’s, in which the skinof the arm was anesthetized and deep pressures and aches broughtout by heavy loadings, was really concerned with the sensibility(23

ORGANIC SENSIBILITY

524

of muscle, and tlius with what came to be called kinesthesis or

proprioception. Von Frey, on the other hand, limited his study ofpressure to the skin by his use of small forces—applied solely to the pressure

hair stimuli—the “microscopic”

spots.

Deep pressure was not, therefore, recognized as dependent on a
separate subcutaneous system of receptors until Ileniy Head in1905 made the distinction (pp. 471-474). The cutaneous and the

subcutaneous nerves are differently distributed, for the former

come to the surface and often progress for a short distance before
reaching the outskirts of the region where their receptors lie. The
eoui’se of such a nerve can he traced on the skin by faradic stimu-

lation with a single electrode, which produces a fluttering sensa-

tion referred to the region where the receptors he. Head, severingsuch a cutaneous nerve, found drat the center of the region whichitsupplies, although anesthetic to warmth, cold, prick and lightpressure,

was nevertheless sensible to heavy pressure. A fairly

heavy pressure gave the dull pressure quaUly, a very heavy pressure gave dull pain. Sensed pressm'os could still be localized as accurately as when the skin was normally sensitive. Thus Head estab-lished deep sensibib'ty as a special sensory system, to which manyof die older experiments which used loadings of several grams ormore had thei-eafter to bo referred.

The distinction between deep sensibility and Idnesthedc may
be only functional, the former having to do with stimuh superficially applied and the latter with movement of the joints. The
Pacinian corpuscles directly beneath the skin are usually assigned
to deep pressure, but they also lie deep in the tissues, especiallyaround Ae joints, and thus presumably in that location have akinesthetic function.

Kinesthesis
Though his eyes be shut, a man knows about the position andposture of his body, and whether its parts are moving or exerting
effort in sustaining

a weight or in pressing against resistance. If

this he kinesthesis, then no philosopher can over have doubted its

existence, Descartes in 1637 remarked on how a man is aware of

distance by perceiving the directions of his

two eyes, just as ablind man might feel out a distance with two staves, one in eachhand. Berkeley in 1709 included the perception ol straining in theeyes as one of the criteria of the perception of distance. Conver-

KINESTHESIS

525

gence and accommodation—both, lands of kinesthesis—wa'e thus
early given tliis formal status. Some have said that Aristotle implied

the existence of muscular sensibility; be that as it may, it was certainly Aristotle who so long delayed the recognition of a sixth

sense by his doctrine that there are but five senses.

The classical and most successful argument for the independent
status of the muscle sense was Charles Bell’s in 1826. Although themuscle spindles wore not discovered until 1863, physiologists afterBell all accepted the muscle sense as a “sixth sense,” arriving in thelatter part of die

nineteenth century at a considerable body ofresearch on the perception of weight, effort, resistance, movement

and position. It was Bastian who in 1880 pointed out tliat theseperceptions are so complex—involving,as they do, tlio sensibilities

of muscles, tendons, joints and skin—that it is better to refer them
to a “Sense of Movement” or kifwslliesis. In general, the psychologists accepted this word kitiestheals as proper, and the teim loomed

large in the sensory introspections, so important in the experi-mental psychology of 1890 to 1920. The physiologist, Sherrington,on the other hand, having contributed to Schafer’s Text-Book in
1900 a chapter on “The Muscular Sense,” invented in 1906 a newword with a physiological sound, proprioception. Tlie proprioceptors, as distinguishedby him from exteroceptors and intero-

ceptors, mediate the kinesthetic sensations. It

decline of introspective psychology

was the ultimate

and the consequent rise ofphysiological psychology that has today gone so far toward thereplacement of Bastian’s word by Sherrington’s.
All through the second half of the nineteenth century there persisted confusionand controversy about the distinction between

muscular sensations and sensations of innervation. Most of theimportant physiologists and psychologists of this period, including both Helmholtz and Wundt, believed that the innervation ofefferent-tracts in voluntary action establishes sensations that arise

wholly within the brain and not by way of afferent fibers from theactivated muscles, These sensations of innervation, forming ihe

sensory conscious basis of the experience of volition, were relinquished, along with the wfll, only reluctantly by the psychologyof the twentieth century. In the nineteenth century it was nevercertain whether an experience of effort was a muscular sensation

or a sensation of innervation.

Now we take up these matters separately.

ORGANIC SENSIBILITY

526
1,

The Muscle Sense. According to Sir William Hamilton, wio

sought in 1846 to set down the history of the muscle sense, dieearliest recognition of this sfacth sense as independent of Aristotle’s
five was due to two Italian philosophers, Julius Caesar Scaliger in

1557 and Caesalpinus of Arezzo in 1569. It is doubtful, however, if
Descartes and Berkeley needed any such formal sanction to justify
their appeals to the muscular sensibilities of the eyes in the forma-tion of dieir theories of space perception. In the early part of thenineteenth century the French physiologist, Bichat, in 1812 presented evidence for sensitivity of the muscles, and the Scottish
philosopher, Thomas Brown, in 1820 insisted that “our muscular

frame” forms a “distinct organ of sense,” without which the perception of spatial extension could not be developed. It is also tine that

Steinbuch in 1811 based a theory of space perception—all these

men were anticipating the space theories of Lotze and Wundt—
upon a sense of movement, but he, as wo shall see presently,
thought of the Bewefftngsideen as occuning for inneivation before
the actual movement of the muscles and was thus really the originator of the conception of sensations of innervation.

The muscle sense, since it was not discovered by Charles Bell,might be said to have been ‘founded’ by him in 1826, when heread before the Royal Society his paper “On the Nervous Circle

which Connects the Voluntary Muscles with the Brain.” At thattime the hard-and-fast distinction between motor and sensory
nerves, the Bell-Magendie law as it came to be called, was still

new. Bell had shown, in an obscure pamphlet in 1811, that thefibers of the posterior nerve roots at the spinal cord are all sensory,and the fibers of the anterior roots all motor, but the world atlarge did not soon learn about his discovery, for Magendie in Parismade the discovery again in 1822. Now, four years later. Bell was
arguing that the nerves of the muscles must contain sensory fibers
as well as motor.

He cited the sensory experiences of ovorexertionand muscle spasm, of running and walking, and of the maintenanceof balance by the bhnd.

He remarked on the capacity of a person

to judge small difierences in the weights of objects by weighing

them in the hand—that was eight years before Weber first gave
as file just noticeable difference.

He noted how muscle sensa-

tions, as well^as sensations from the skin, must participate in thetactual perc^tion of distance, size, form, weight, hardness andMUSCLE SENSE

527

rou^ness, and how visual perception is dependent upon awareness of the movements of the muscles of the eyes.

Bell also described— and this instance was crucial to his argu-

ment—a case of a woman with an insensitive arm. She could holdher baby to her breast only so long as she looked at her arm;

when she looked away, the arm would drop and the baby start tofall. The case was probably one of tabes dorsalis. In the latterpart of the century many such cases were cited as indication of

the important function of Idnesthesis hr directing movement. For
instance, in locomotor ataxia the patient cannot walk without lean-

ing forward slightly in order to use vision for the correct place-ment of his feet. This is exactly the point that Bell was making
about the “nervous circle”: precise movement depends not only on

motor innervation which originates in the brain, but also on muscular sensations which originate in the muscle. “Between the brain

and the muscles there is a circle of nerves,” he wrote; “one nerve
conveys the influence from die brain to the muscle, another gives
the sense of the condition of the muscle to the brain.” In otherwords, the brain can make the muscles move correctly only becauseithas from them a continuous report as to how the movement

is getting on,

Bell’s argument about tlris nervous circle finds itself

amply sustained today in our knowledge of proprioceptive reflexes
and of the reflex circle, where Idnesthesis is necessary for correct

movement unless vision be substituted for the Idnesthesis.
After Bell the existence of muscular sensation was good doctrine.

Both Weber and Johannes Muller accepted it, and Kiihne’s establishment in 1863 of the muscle spindles as sensory receptors in themuscle clinched the matter, if anything more were needed. One
could, however, believe in the muscle sense and still hold the conviction about the existence of sensations of innervation.

2.
isSensoWons of Innervation. It was the conviction that the will

an experienced entity which supported the belief in sensationsof innervation. At the beginning of the nineteenth oentuiy British

empiricism had become sensationistic, Locke (1690) analyzed experience into ideas, but Hume (1739) and James Mfll (1829) put
sensations first and regarded ideas as but copies of them. Certainty
willing is conscious.

One knows that and how he moves or isabout to move. If consciousness is sensory, there ought to be will-

OHGANIC SENSIBILITY

528

ing sensations. Steinbuch in 1811 called them Bewegungsideen,

and argued that they arise directly from the innervation of motor
nerves. That was the beginning of this theory.
Johannes Muller in 1838 accepted sensations of innervation, in
addition to the muscle sense; “The idea of weight and pressure in
raising bodies or in resisting forces may in part arise,” he wrote,“from the consciousness of the amount of nervous energy transmitted from the brain rather than from a sensation in the muscles
themselves.” Sir WiUiam Hamilton in 1846 believed in them andai'gued for them, calling them the “locomotive faculty,” which pro-vides for our appreciation of the “mental motive energy” that initiates movement. Ludwig, the physiologist, in 1852,

Wundt in 1863,

Bain in 1864, Helmholtz in 1886, and many others after them, Uke
G. H. Lewes

m 1878 and Mach in 1886, all held to these sensationsof central origin. Wundt oven listed them in his inventory of sen-sations as late as 1910.

There were three arguments, (a) A person with an anestheticarm may will to make a given motion and think that he has madeit until he looks at die arm and sees that ho has failed, Thus he has.
it

was said, the consciousness of movement without the correcting

perception that the muscle sensations would have added, (b) A

person can be conscious of an amputated limb and of moving it,even though the muscles which would have been involved havebeen amputated too. (c) If a finger is immobilized, one can will
to move it, and the effort of ivill does not vaiy in degree with thestrain in the muscle. This experiment, howovei', seems not to havebeen adequately controlled.

One of the first to oppose this doctrine was Landry in his studyof paralyses and anesAesias in 1859. He considered all these phe-nomena and, admitting that the mind must bo aware of its own
volition, concluded nevertheless that the perceptions of resistance,

weight and movement cannot be precise vrithout the mediation of
the muscle sense. Bastian came to the same conclusion in 1869;

and Perrier in 1876. James formulated the argument against thesensations of innervation in 1890. The case was not open and shut.

Now what was it that took these sensations out of the literaturein the twentieth century?
tail in his

Why did Sherrington discuss them in de-chapter on die muscle sense in 1900 and ignore themcompletely in his Integrative Action of the Nervous System in 1906?

SENSATIONS OF INNERVATION

529

The answer lies in the coming of age of the theories of ideomotor
action and of reflex action.

The theory of ideomotor action was not new. Lotze ( 1852) had
given examples of it. So had many others, James (1890) stressedit.

In the present century it became more important because in-terest shiftedaway from observation toward correlation, awayfrom the dhect observation of functions toward the discovery offunctional relations between observed terms. In 1850 or 1890 it wasenough to perceive directly that innervation is immediately sensed.
In 1920 it would have been necessary to show, at the very least,that the innervation occurs before its sensation

is felt

and that

there is no nervous circle operating by way of the muscle between
it

and the sensation. Attention to the Bewegungsideen showedmerely that they were present before the consequent and appropriate movement, often a long time before it. Since movement fol-

lowed them, they could not be caused by the movement. They

were sensations for, not of, innervation.
For a similar reason the theory of the reflex, furthered by Sherrington, has flourished in the present century. Interest in the reflex

takes attention away from mere excitation or mere movement andplaces it upon the causal relation between excitation and move-

ment. This theory is, moreover, physiological in that it accepts
conventional physiology and ignores introspection. Since nothingisknown of the activation of sensory centers by motor centers,

there is left for the explanation of this phenomenon only the nervous
circleject’sthrough the muscles— or tiirough the eyes when the subown movement becomes for him a visud stimulus. Such areflexologioal picture was early adequate to the facts. Since thenthe increase of knowledge about proprioceptive reflexes, as ac-

counting for postural, articulatory and motor mechanisms, has
fixed it firmly in psychophysiological thought.

That is why sensations of innervations went out of style after
1900.

8.

Kinesthesis. Certainly kinesthesis got its full share of atten-

tion from 1850 to 1920.

Fedmer, with his Elemnte der Psycho-

physik in 1880, made the disoriinmation of lifted weights the representative psychophysical experiment,

There must have been

Lifted within the next sixty years hundreds of thousands of pairs

ORGANIC SENSIBILITY

530

of weights, all for the purpose of studying sensitivity and judg-

more to the develop-

ment, for the lifted weights contributed

ment of the psychophysical methods than to a knowledge of Idnesthesls.

Tile important kinesthetic problems were the detertnination ofsensitivity in the perceptions of weight, resistance, effort, position

and movement, and the discovery of the sensory mechanisms forthese perceptions. Here Goldsoheider in a series of papers published from 1887 to 1898 made themost notable contribution,

while the physiologists established the existence of receptors inmuscle and tendons and around the joints. Let us consider first thediscovery of the kinesthetio receptors.

What we now call Pacinian oorpusdes, or Vater-Pacini corpuscles, were first discovered by Abraham Vater sometime prior
to 1741.

He described them as tiny bodies lying along the cutaneous

nerves. After that they were forgotten, until Pacini rediscovered

them along the nerves of the finger in 1835. By 1840 he had foundmany bodies of this sort, differing greatly in size and lying in the
deep subcutaneous tissue, the mucous membrane and the internalorgans. Pacini’s name became attached to the corpuscles becauseof the completeness of his description and also because he madehis discovery at a time when the new sixth sense

needed deep-

lying organs to mediate it, It was Rauber who, in 1865, showed diatiese corpuscles are associated with the tendons and the ligamentsof the joints, although they do not lie directly in the joint surfaces.
Naturally then Goldsoheider and others

known to be sensitive—attributed the—since thejointswere

sensibility to these corpuscles

and supposed that they function in the perception of the position
and movement of a limb and to some extent also in the perceptionof weight and resistance. This argument was strengthened by thefact that introspection seems to show a qualitative similarity be-

tween deep pressure and articular sensibility—perhaps even an
identity.

The second Idnesdietic organ to be discovered was the musde
spindle. After 1850 there were several histological descriptions ofsmall structures in voluntary muscle, structures not identified as
to their functions. ESlliker in 1862 certainly did describe the muscle spindles—“nerve-buds" he called

them—but he thought they

were centers of growth. Then in 1863 Kiihne gave a more precise
account of these organs, named them muscle spindles, and sug-

KINESTHESIS

631

gested cautiously that they might be receptors for the musde sense.

In 1892 RuSlni actually identified the spindles as neural tissue withnerve fibers leading from them, and Sherrington in 1894, by sectioning the nerve root at the spinal cord, showed definitely that theirfunction is sensory. Finally, in 1928 Fulton and Pi-Sufier, studying

neural action currents from musde, came tentativdy to the conclusion tiiat the spindles are actuated by stretching the muscle, an

hypothesis that was fully confirmed by Matthews in 1931 when hesucceeded in isolating a single musde fiber and spindle from themusde of a frog and in showing that stretching is the tme stimulus
for this receptor. This finding implies that muscular contraction isperhaps unconsdous, that the direct sensibility of the muscles occurs only on stretching. Such a conclusion would have seemed astrange outcome for the analysis of the muscle sense—a conclusionthat the muscles ate only slightly involved in Charles Bell’s "muscu-

sense”—had it not been for the fact that other researches

larshowed most of the kinesthetic perceptions, like movement, position, weight and resistance, to be dependent on the sensibility ofthe tissue neai' tire joints and, when intense, of the tendons.

The receptors in the tendons were the last to be found. They
are called the Golgi spindles but were first described by RoUettin 1876, who studied diem in the frog’s tendon. Golgi gave them
their complete description and his name in 1880,

and the argument as to their sensory function and innervation was made in 1900
by Huber and DeWitt. In general, it has been supposed thattendinous sensibility enters, as additional to articular sensibility,
in the perception of heavy weight, great resistance and perhaps

extreme effort.

There was also in the late nineteenth century a great deal of interest in kinesthesis

and movement. Five fairly important texts,

published between 1887 and 1903, dealt with this topic, but there

were nt) far-reaching systematic discoveries. We must content ourselves, therefore, with noting certain important conclusions, no oneof which ought to be entirely omitted from this book.
(a) Goldscheider in 1889 established the fact that sensitivity ofa limb to movement is great—seemingly more precise than cutane-

ous space perception. At a rate of 0.3 degrees per sec., the thresholdfor passive movement of the shoulder lies between,0.2 and 0.4 degrees.

The ankle is from a third to a fifth as sensitive, and the

Aresholds for seven other joints lie in between .the thresholds for

ORGANIC SENSIBILITY

532

the anlde and the shoulder. If sensitivity is measured in terms ofspeed of movement, then the shoulder still appears as the mostsensitive joint, for movement in it is perceived at slower speeds

than in other joints. Active voluntary movement shows sensitivity

a Uttle greater than passive involuntary movement. The fact thatsuch small angular displacements can be sensed at such relatively
slow speeds did much to direct attention upon the importance ofkinesdiesis.
( b ) It was also Goldscheider s opinion that the joint contributes
more than the muscles to the perception of movement. He anesthetized the sldn and the underlying tissues with cocaine andfound that sensitivity is not greatly diminished. Also he partiallyanesthetized the joint by passing a faradio current thi'ough it, finding that sensitivity is lien greatiy decreased. Other clinical evi-

dence bore further on this point. Duchenne about 1853, describing a case where muscular and iactual sensitivity were lost thoughsensibility was retained in the joint, noted that the perception of

posture and movement were but little affected. Much later Striimpell in 1902 described the opposite condition: the joint was anestlietic, the tendon

and musde not, and the patient’s perception of

posture and movement was abolished. Rillsbury in 1901 verified
Goldscheider’s finding that faradization of the elbow reduces its
sensitivity to movement, but showed that faradization of the vraist

also reduces the sensitivity to movement of the elbow—as if faradi-zation acted more as a distraction than as an anesthetic. In general,nevertheless, Goldscheider’s analysis has been accepted.

(c) Itwas Goldscheider again who formulated the conven-tional threefold classification of kinesthesis into muscular, tendi-

nous and articular sensibility. He was supported by the finding of
three appropriate receptors, by such analyses as we have noted in

the preceding paragraph, and to some extent by introspection.

(d) In 1889—the year of Goldscheider’s most important contributions—Muller and Schumann publishedtheir famous analysisof the mechanism of the discrimination of lifted weights. It was
their contention that a second weight is judged heavier or lifter

than an immediately preceding first weight, because the subject,

being set {eingestelU) for a certain effort by the first weight, exerts the same ^ort upon the second. If the second comes up easilyand quiddy, dien it seems lighter than the first. If it comes up
slowly, then it isjudged heavier. This view, which, because of

KINESTHESIS AND PROPRIOCEPTION

533

the importance of its authors, received much attention in psychophysics, was not taken by Muller and Schumann to support thetheory of sensations of innei-vation. They held that the Einstellungor motor impulse is unconscious imti] its effect, the speed withwhich the hand lifts the weight, is noticed. Certainly an Einstellung of this sort enters into the size-weight illusion (a large weightfeels lighter than a small weight which actually weighs the same).

Thus it appears that besides kinesthesis we have in this field totake account of motor predispositions.
(e) Finally a word must be said about the increasing impor-tance of kinesthesis in the introspection of those days. The Wundtian school reduced all space perception to a consciousness of

movement. Visual extent was supposed to be due to an awarenessof eye-movements, and accommodation and convergence to fur-nish kinesthetic cues in the visual perception of depth. Then, besides muscular' sensation,

Wundt, in his tri-dimerrsional theory(1896 et seq.), introduced strain and relaxation as a dimension offeeling, thus sanctioning the constant use of fhese terms in thedescription of consciousness.
Later, when Kiilpe’s Wiuzburg School had failed to validate theBewusstheii as an imageless element of thought, Titchener pro-

posed as a substititte the conscious attitude, which again and again
found its description in terras of kinesthesis. Introspective protocols on the thou^t processes were filled wiih sensory accounts ofwhat the observer’s body was doing. Take, for instance. Miss
Clarke’s introspective study of fifty-nine conscious attitudes—suclr

conscious states as approval, awfubess, baffled expectation, caution, comfort, confidence, and so on

down the alphabet. According

to the present author’s count, she listed here 168 mental processes—distributed as follows:—sensations and images

Kmesthetio or organic

113

Verbal (kmeslhetic, auditory, visual)21

Visual18

Tactual9

Auditory

B

Some of fhese mtrospectrons make biological sense. For iirstance;
PHde "slight tendency to straighten up my ned&and simle.” Ir“sensation from frowning; visual image of frownmg
ritation==face; tendency to lower and shake the head; hot sensation in head

ORGANIC SENSIBILITY

534

and back.” Others were more general. Disgust— “organic sensa-

tions throughout the body.” Strongeness='‘weak organic feeling
all over body; strain; sensations from breathing; and special sensa-

tion from diaphragm.” There were many papers at this time ( 1909-1916) which showed how pervasive is the kinesthetic content ofconsciousness. "The great god Kinesthesisl” someone remarked ata meeting of the Society of Experimental Psychologists when several of these introspective studies had been reported.

(4) Froptioception. In 1895 Mott and Sherrington showed conclusively what BeU had asserted—that sensory impulses are neces-sary for accurate voluntary movement. They sectioned at the spinal

cord die posterior nerve roots of a monkey’s limb and found thatthe animal let the limb drag and did not use it in locomotion oreven to get food when prevented from using his other Umbs. Nevertheless the limb with fce cut sensory connections was activated inviolent general action, like struggling

showing that the motor

fibers, which pass through the anleiior root, were still intact. Of

course, this finding was not novel: it was simply new and excel-

lent proof, after seventy years, that Bell’s conception of the ‘nerv-

ous circle’ was correct.

The next decade saw the birth of reflexology—in psychology, in
physiology. In psychology there was John Dewey’s defense of thereflex arc concept in 1890, Pavlov’s work on the conditioned reflex

which began about 1903, and of course ultimately behaviorism, thestimulus-response psychology of Watson after 1913, Sherrington,

however, made an equal contribution on the side of physiology.

The general effect of the Bell-Magendie law’s separation of thesensory and motor neural systems and of the discovery of sensory
and motor centers in the brain had been to separate the afferent andefferent neural systems. Sherrington, following the path marked

out by Bell and seeing that the entire reflex arc must be considered
as a whole, finally formulated this point of view in 1906 in his

Silliman Lectures at Yale and in the resultant The Integrative Ac-tion of the Nervous System, a very important book which was long

fundamental to thought in neural physiology and in behavioristic
psychology.
It

was in an article published just before these lectures that

Sherrington invented the term “proprio-ception”: “since in the

deep field the stimuli to the receptors are delivered by the or-

VEBUGO

535

ganism itself, the deep receptors may be termed pwprio-ceptors,

and the deep field a field of proprio-ceptlon

he wrote. He alsocoined at the same time the terms intero-ceptor and extero-oeptor.
Proprioception is, of course, nothing else than kinesthesis, exceptthat it is the afferent part of a reflex physiologically considered,

whereas Mnesthesis is sensation considered in its own right andfunctioning for introspection. The decline of interest in the sensory

data of consciousness and the rise of physiological conceptualism inmodem psychology has led, however, almost to the abandonmentof Bastian’s word and to tlie general acceptance of Sherrington’s.

Proprioception in the Inner Ear
The history of what has been called vestibular equihbration,
the static sense, ampullar sensation, giddiness, vertigo, the senseof rotation, and the sensibility of the semicircular canals is volumi-

nous and simple. It is voluminous because there has been so much
written about it: in 1922 Griffith cited 1685 titles from 1820 on. It
is simple because it can all be organized about Furkinje’s descrip-

tions of dizziness (1820-1825), Fburens’ discovery drat lesions of

the semicircular canals produce muscular incoordination in die

plane of the affected canals (1824-1830), the Mach-Breuer-Brown
experiments and their theory of the function of the canals ( 18731875), and the discovery of vertiginous habituation by the psychologists of the U.S,

Army (1918), Griffith (1920) and Dodge(1923). Here is the story.

Vertigo in its dependence upon bodily rotation, the motion of aship at sea or vision downward from a great sheer height did nothave to be discovered by scientists; such things man could noticewithout special training or technical aids. It required scientists,

however, to describe the phenomenon, and one of the early descriptions was assembled in 1801 by Erasmus Darwin, die grand-father of Charles Darwin and the author of Zoofiomio. He told how

on spinning around one sees the environs rotating in an opposite
direction, slowing up, and then, if the actual rotation is stopped,

appearing to revolve in the opposite direction. Apparent negative
after-rotation thus became a matter of record, The rest of Darwin’s

discussion had to do with dizziness from the tops, of tall towers,
sea-sickness, nausea, and the Inability of a “hoodwinked” person
to walk a straight line.

,

536

ORGANIC SENSIBILITY

From 1820 to 1827 Purkinje, the phenomenological physiologist(pp. 117 f. ), contributed five descriptive and experimental papers

about vertigo. He established the method of rotation—spinning theobserver around—for the study of the phenomenon; other methodsof inducing veitigo were used later. He described fully the appar-

ent movement of the visual field during rotation and after rotation

has ceased.

He discovei-ed that the axis of the apparent after-

rotation moves with the head, a fact which indicated to him thatthe organ for this perception must He in the head. He suggested
that the brain itself, being soft and pHable, might lag behind therotation of the hard skull, thus giving rise to this perception. That

was an appeal to the principle of inertia which Mach and theothers used in the 1870’s to explain the action of the semicircular
canals. Purkinje, when he suggested this theory ( November, 1825 )had only just learned of Flourens’ initial experiment (vide infra)
in which he sectioned the canals of pigeons, but, since the inter-

pretation of Flourens’ results was not yet clear, Purkinje pointed

out that the inertia of tire brain might explain, not only the perception of rotation, but also the perception of rootiliuoar move-

ment By 1827 he had ceased to mention this theory, being content
what happens
when a lesion is effected in the cerebellum (Flourens).
Meanwhile on November 15, 1824, Pierre Flourens, tire outto note the similarity of the effects of rotation to

standing physiologist to use in that half century the method of
ablation for tire determination of the functions of the different
parts of the brain, sectioned two corresponding semicircular canals
in a pigeon, one on each side, and allowed the wounds to heal.

Hofound that the bird had become, as a result of this operation, incapable of accurate coordinated movement, showing the maximal
distarbance of movement in the plane of the sectioned canals. An

amazing discovery—that spatial ordering of bodily movement
should depend upon the operation of the organ of hearitigl He
took the pigeon to a session of the Acad6mie des Sciences on Jan-uary 10, 1825, for exhibition. Later in that year he published his

new fact briefly, and then in 1828 undertook careful systematic research on the functions of the canals, publishing those results in1830.

Flourens ma^e it clear in these papers that sections of the canals
give rise to radical disturbances of equilibrium, incoordinations
simflai to what he had found for experimental lesions of the cere-FUNCTIONS OF THE SEMICIECULAR CANALS

537

bellum and Purkinje had found for vertigo. The pigeons could notwalk or fly, Tliey ‘tried' to move, and did indeed move, yet could
not move as they ‘wished.’ Instead diey tended to jerk flieir heads

back and forth violently and purposelessly, mostly in the plane of
the cut canals. The section of a single canal, he found, had only asmall effect. The violent movements came from the section of cor-

responding canals on both sides. Cutting of all six canals produced
convulsions. Flourens verified these conclusions

firstwith morethan half a dozen other kinds of birds, and then with rabbits.
After Flourens nothing much happened for forty years. In 1853

both Harless and Brown-S^quard told how tliey had

verified

Flourens’ experiments. Harless’ account was brief, but

Brown-

Sdquard described tlie turning movements in frogs that occur on
section of the canals and also on experimental injury to the audi-

tory nerve. He disagreed with Flourens’ conclusions, preferred toaccount for ihe turning movements as a result of the nerve injury.

In 1866 Toynbee, m a six-line note, repoitcd the case of a patient

whose vertigo disappeared permanently when his inner ear was
extruded. Toynbee removed a piece of bone from the external

meatus only to find on examination lhal it consisted of the vestibule, cochlea and canals of that car!

The 1870's, on the other hand, were the important decade in thishistory. Out of more tlian a hundred published papers there were

contributions by such well known men ns Goltz, Hitzig, Mach,

Breuer and Crum Brown. Let us consider first some of the factfinding and then the Mach-Broucr-Brown theory.

We must begin by noting the development of methods of research and thus of the knowledge of the essential stimulus forthese phenomena, Mach (1873-1875) arranged for the experimental control of rotation( Fig.

by constructing his huge rotation chair86 ) in which an observer, seated erect in the chair, could be,

rotated about his own vertical axis (aa), or about another axis(AA) eccentric to his body. This gigantic instrument, built of
4-by-4-moh timbers, over four meters long and rotating consequently through a circle of four meters diameter, was later repro-

duced in several American laboratories which could in the earlydays extract sufficient space from a reluctant administration.

The surgical method of Flourens was perfected

W Cyon (1873-

1878) and Bflttcher (1874). Cyon acquired a high degree of operative skill, learning even to insert foreign matter into a single

ORGANIC SENSIBILITY

538
canal

{Me infra). Goltz (1870) found that hot and cold waterin the external ear produce vertigo,

nausea and nystagmic eye-movements, and Hiteig (1871) perfected the method of arousing
vertigo and eye-movements by passing an electi'ic current throughthe head, a technique aheady mentioned by Purkinje ( 1826).
Goltz’s experiments (1870) were design^ to show that the ear

Fro. 86. Rotation Framb:

Mach (1873)

The subject sat blindfolded in the chair, whose angle could be changed
about the horizontal axis a. The back and sides piotected him from aircurrents on rotation and he could also be boxed in with cardboard. He could

then be rotated by hand about his own vertical axis, on, or about the eccenliic
axis,

AA. In later models the radius oA could be altered and there werecounterweights on the frame Ril to balance the subjects. In the original
instrument RH was 4 m. long, built of 4 X 4-in. thnbeis.

furnishes a basis of orientation primarily for the head, that orientation is changed when the head is moved after the rotary effecthas been established. Lflwenberg (1873) devised other experi-ments to prove that the disequiUbration arising from stimulation of
the canals or injury to them depends upon positive excitation by
the canals and is not merely a partial paralysis due to the canals’
ceasing to function.

Now for the theory, Purkinje had suggested that vertigo of rotation might depend upon the inertia of the brain tissue, but by

AMPULLAH SENSIBILITY

539

now it was pietly coitain that the cause of the peiception must be
found in the cai. Goltz ( 1870), noting what would be the efteol ofinertia within tlie canals, aigued that oiientation must be due to apattern of piessuies set up

m the ihiee canals. Since the canals are

at light angles to eadi othei, these three piessuies could, by a soitof Gaitesian cooidmates, come to lepicsent any position in space.

Fm. 87

Spatial Relations or
THE Sekucibciilaii Canals

The canals, tremendously magnified with lespect to the shulI, areshown horn behind as if on glass
platesTlie anterior canal on theleft

puned with theIS

posVeilorcanal on the light and synunetrical
to It

The

left

postciioi

canal

is

symmetiiully paued with thelight .uiteiioi canal, and the two
1101170111,11 canals form the tliiid
also

synimctiic.\l

p.iii

Alter Ewald.

In 1873 Mach developed this idea by showing that lotation might

be expected to cioate in any canal a piessute which vaiies inamount accoiding to the component of the lotation that lies in theplane of that canal. Hoiizontal piessuie would

affect only thehorizontal canals. Rotation about a bansveise hoiizontal axis

would affect all foiu vertical canals, since they lie at about a fortyflve-degrec angle with the plane of rotation (Fig. 87). But

Ma^went fuithei. He pointed out that the principle of inertia would
opeiate, not for lotation, but only for a change in speed of rotation, that is to say, for acceleiation or deceleration. Thus his theory

made angular acceleration the stimulus to the pressure-pattern
upon the nerve endings in the ampullae of the canals. This conception explams, oi course, why rotation is perceived during the acceleration of starting rotation from rest, why there is adaptation(no perception of rotation) when speed is steadily maintained,

why deceleration or stopping arouses the negative after-effect(perception of reversed rotation). In part Mach was arguing tele-ORGANIC SENSIBILITY

540

ologically: the structure of the canals is such that they ought towork thus. The chief difficulty with his theory was that the canals
are so small (about half a millimeter diameter inside the bonytube) that the lymph could not be expected to flow within them.

Mach believed that it did not actually flow, but that the pressureswould be created by its tendency to move.
Mach also proposed that the macula in the vestibule may be asimilar organ for the perception of acceleration in a straight hne.

Such acceleration can be perceived; the canals ought not to beaffected by it; the macula is an extra organ waiting to have a function assigned to it; it could work as he suggested.

In 1873, the year of Mach’s first contribution to tliis theory,
Breuer also had the same idea, deriving it, as did Mach, from
Goltz’s discussion. The theory was thus independently conceived,

except as Purkinje, Goltz and others had already indicated its
general nature. Mach was explicit in 1873, but Breuer’s first full
discussion came out in 1874, when he argued tliat the dynamic

system of the canals can work only if the lymph flows freely in thecanals. Mach had thought that the lymph could not flow hi tlie

tiny canals, that only differentials of pressure would be set up by

angular acceleration. Breuer held that pressure differences would
too soon be equalized unless the liquid were free to kg behind inpositive acceleration or coast ahead in negative acceleration, Thereisa real dilemma involved in this discrepancy; each argument

seems adequate against the other theory.
Breuer’s most important paper, developing his dieory, oiltidzing

Mach, and recounting experiments on birds and dogs wliich verified Flourens' results,

came out in 1876. Here, being concernedmore with equilibration than with rotation, he applied to thesensory functions of the canals the name static sense, a designationthat held for a long time, even though the perception of rotation,

not the maintenance of balance, was so often the subject of investigation.

The third independent originator of this theory was Crum Brown
in England, who discovered Mach’s and Breucr's first papers after

he had formukted the theory himself but before he published in
1874. His name has, therefore, rightly been added to what is called

the Maoh-Breuer-Brown theory.

Crum Brown, agreeing with Breuer as to the actual movementof the lymph in the canals, added one new feature to the theory.

AMPULLAR SENSIBILITY

541

Mach had supposed that each canal mediates all the componentsof rotation that he in its own plane, both positive and negative.

Clockwise acceleration about a vertical axis for the erect observer

would move the ampullar organs in both the right and left horizontal canals in the same angular direction, and counterclockwise ac-celeration (clockwise deceleration)

would exert pressure in the

opposite direction. Crum Brown doubted that the same ampullarorgan could operate for both directions of rotation, could have two
specific energies, as it were, and he observed that such a double

functioning would be unnecessary because of the symmetrical ar-

rangement of the canals. The canals are paired. The left canal isalways the reversed pattern of its mate on the right. Thus Brown

assumed that the left canal might function for one direction of acceleration, say clockwise, and be ‘silent’ for counterclockwise acoaloration. Its mate on the right, being reversed anatomically,
would also be reversed in function, operating when the left canal

was silent. It was a plausible view which fitted in with Flom'ens’
finding that disequilibration in a given plane is relatively small

when only one canal in that plane is sectioned and more thandoubled when its mate is also cut. Mach presently accepted
Brown’s contribution.

Crum Brown also accepted Mach’s idea that the macula in thevestibule should be regarded as an organ for the perception ofrectilinear motion. Having simplified the functions of the ampullarorgans so much, he could hardly avoid relieving them also of thecapacity for excitation in rectilinear acceleration.

Not all the theorizing of the 1870’s was done, however, by Goltz,
Mach, Breuer and Crum Brown. Bottcher ( 1874), after criticizing
the whole history of thought on this problem from Flourens on,

decided that the function of the entire ear is auditory. Cyon, in apolemical paper in 1873, made a similar argument, maintaining,

however, that auditory space perception is basic to the perceptionof bodily space in general and to die orientation of the head in particular. The canals seemed to him to be, because of their anatomi-

cal arrangement, a natural spatial organ, so of course their injury

would lead to disorientation. (See pp. 386 f., 401-403.) In 1878
he used his operative skill to drain the canals of pigeons, fill themwith gelatin, and plug them with filaments of dry«sea-weed (La-manarian) which would presumably absorb moisture, swell, increase the internal pressures,and in any case immobilize theORGANIC SENSIBILITY

542

lymph. When he found that the pigeons did not show disequilibration after this violent treatment, he concluded tliat Mach’s theoryof pressure as the stimulus to the ampullar organs must be wrong.

Nevertheless the Mach-Breuer-Brown theory remained in favor.
It prevailed, but not everyone was sure that the ampullar Sense
is like other senses in giving rise to sensation.

Both Mach and Cyon

noted that introspection fails to reveal for rotation any uniquequality. The perception consists rather of a pattern of kinesthetic

and cutaneous sensations referred to the periphery of the body.

They concluded, therefore, that the ampullar sense is a reflex sense,
giving rise directly to reflexes which establish (or disestablish)
equilibrium and only indirectly by way of these reflex changes tothe characteristic kinesthesis.

Confiimation of the theory that vertigo depends on the actionof the semicircular canals was next got from the behavior of deafmutes. Crum Brown had suggested in 1878 that, since many deafmutes are found to have impairment of the canals as well as of thecochlea, these persons ought not to be subject to vertigo. It was

William James who put this idea to the test in 1882, lie arrangeda sort of swing, a boai'd suspended by two ropes. The subject sat
on the board; the ropes, kept apart by a cross-bar above the subject's

head, were twisted togethm- above the bar by tmming theboard around continuously. Then, when James let go of the board,
the subject spun around rapidly as the ropes untwisted themselves,

and told, after he had come to rest, whether he was dizzy. Of two
hundred Harvard students and instructors, none of whom was adeaf mute, all but one were made dizzy. Of 519 deaf mutes, 199

were dizzy, 134 others only slightly dizzy, and 186 not dizzy at all.

They all had their eyes closed, of course, and some performed theexperiment with their heads on one side, a disorientation which
normally gives greater vertigo if the head is

moved afterward.

James also reported that some deaf mutes cannot swim, because
they lose orientation almost completely

when the visual andkinesthetic cues for position are diminished under water, He noted,
too, that there are cases of swimmers who could no longer swim

after they had lost their hearing—their hearing, and presumably

also their ampullar sense.
Ifreidl in 1801,

confirming James’ finding, amplified it. Aboutfifty per cent of his deaf mutes failed to

become dizzy or to shownystagmic eye-movements after rapid rotation. A quarter of themVESTHULAR AND CENTRAL ADAPTATION

S43

failed to note a displacement of the vertical on rotation. Later, hefound that 84 per cent of congenital deaf mutes show no vertigo
after rotation. The pathological findings that he cited from post-

mortems gave die figure of 50 per cent of deaf mutes with defective
semicircular canals. Poliak in 1893 failed to get veiligo from thepassage of an electric current through the head in 80 per cent of
the deaf mutes on whom he tried this experiment. The point hereis, ofcoume, that the percentage of live deaf mutes without vertigo

is roughly

comparable to the percentage of dead deaf mutes withdefective canals,

Subsequendy there was enough research on vestibular equilibration— over a thousand papers published from 1900 to 1920 but—

no radical change in basic theory until 1918. Gagllo in 1899 intro-

duced the ancsdielic method of research, destroying die sensitivityof the canals by the use of cocaine and noting consequent disequilibration. Alexander in 1910 demonstrated clearly what others

had reported incidentally, diat pressure on the ear produces nystagmus. But these discoveries applied only to methods of researchand did not change the basic facts.
In the World War of 1914-1918 the French, as aviation became
important, hitroduccd the Bdiilny test for aviators. That is a testof sensitivity to rotation, and it was argued, in analogy to the deafmutes who cannot swim undei walci, that oquilibratoiy sensitivity
ought to be a property of a good aviator. After the Unitod States

had taken over the test, it turned out tliat good experienced pilots
were often not very susceptible to vertigo, showing up poorly on
the test. Griffith, with the War over in 1920, was one of the firstto bring this problem to a laboratory solution. All the effects of—^nystagmus, nausea, changes of circulation—wear

rotationoff, heproved, with practice. They decrease rapidly from day to day,and some decrease in noticeable degree in ten successive trials ona single day. He did not find, however, that such vertiginous habituation decreases sensitivity to the perception of rotationi practice destroys, not the basic perception,

but the accessory phe-nomena.

Dodge in 1923, however, showed that die basic perception, whencarefully studied, is much more complicated and subject to adapta-

tion than the simple dynamics of the semicircular canals lead one
to expect. He found (a) a positive after-image of rotation which

precedes the negative whenever both occur, (b) adaptation, notORGANIC SENSIBILITY

544

merely to constant speed, but actually to constant angular acceleration. (c)an occasional negative after-image during acceleration,and (d) adaptation to oscillatory movement. These phenomena
occur both for the perception Itself and for the accompanying eyemovements. It is true the perception of such anomalies may nbt be
as intense as the experiences which occur according to the nowclassical theory, yet Dodge worked under certain limitations—such

as the fact that the acceleration of an observer cannot with safety

be continued indefinitely in order to get adaptation. His findings
seem to mean that the organism adjusts itself, temporarily or evenrelatively permanently (consider the whirhng dervishes) in such amanner that frequently repeated conditions come to have less effect upon it, Since such adjustmcnls cannot occur in the mechanicsof the ear, they must, it would seem,depend upon the central

nervous system. Dodge called rotational adaptation of tlio kindthat is explained by the Mach-Breuer-Brown theory “peripheral

sensory refractoriness, mechanical type.” He ascribed these otheradaptive phenomena to the operation of a “central compensating
factor.” As in vision and hearing, so now in the vestibular sense,

the progress of research had forced theory to take accoirnt ol thebrain as well as the sense-organ.

The question of a unique ampullar quality was settled by GrifMach and Cyon had doubted that there is any special
sensation, available to introspection, for tliis sense. They noted

fith in 1920.

that the conscious data of the perception are visual and kinesthetic.
GriflBth confirmed them. Dizziness is ( a) kinestlresis from the eyes,neck and arms, (b) pressure from the regions of the viscera, chestand head, and (c) sensory processes which depend upon vascularchanges. This pattern becomes less intense and less complex under
habitiratian. It varies with attention, attitude, the character of thevisual field, and the mode of ocular fixation. Since these phenomena

are all accessory, arising immediatelyfrom other receptors, itwould seem that the semldrcirlar canals do actually provide us
with a sense that furnishes us with no sensation, a ‘refiex sense,' asCyon called it.
Internal Sensibility
Except of thq muscular sense, not much of scientific Importance

was said concerning internal sensibility before the present century. Everyone knew about hunger and thirst, and a great deal was

INTERNAL SENSIBILITY

545

written about these two experiences; yet the writers had little

comprehension of the nature ol those perceptions either as interoception or as motives. So too everyone knew about bodily pain thatooours in injury and sickness; yet there was no method for discovering how it is aroused or where it arises. Being inaccessible, the insides of die body seem to be fairly insensible. The philosophers andphysiologists tended, moreover, to ignore the viscera in their dis-cussions of sensation, because sensation, which was regarded as

the avenue by which the mind learns about things, must normally

have an object, whereas pain, pleasure, tickle, shudder, hunger,
nausea, and tlie sense of well-being appear to have no objects.

Albrecht von HaUer (1763) in his systematic inventory of thesensory capacities of the human body mentioned under Tactus

only the sensations from sweating and from vasomotor changes.
After finishing with the five senses, he wrote, indeed, a chapter on

Senm inlerni, but there he considered perception, imagination,
attention,

memory, thought, judgment, delirium, emotion,will,

pain, pleasure, desire and sleep—all the menial events that are, as
itsoomed to him, wholly contained witliin the skin. It is tine thatelsewhere he commented on internal pain as well as hunger andthirst, that he had written an article in 1752 showing

how insensitive

are the internal organs to ordinary handling, although responding
readily to their adequate stimuli; nevertlieless, tire problem of inleinal sensibility was not clearly drawn for him.

Trying to be systematically complete in 1829, James Mill could

add to the five senses only “the sensations of disorganization,” bywhich he meant pain, both external and internal, musculat sensations,and the sensations of the alimentary canal. Bain, however,in 1855, could discuss organic muscular’ feelings (pain, fatigue,sensations from the bones

and ligaments), sensations of nerve(pain, fatigue, health), organic feelings of circulation and nutrition (thirst, starvation, consdoosness of animal existence), feelings of respiration (relief, suffocation), and sensations of the ali-mentary canal (digestion, hunger, disgust). Sir William Hamilton
in 1859 also considered the problem of the general tactual sensitivity of the body, the consciousness of well-being and ill-being,listing the facts under theconventional terns, coenesthesia andcommon sensibility, that were then available. Weber, of course,
in 1846 had already given the GemeingefUhl its status as a class,including in it all pain and also the other inaccessible internal sen-

ORGANIC SENSIBILITY

546
sations,

In spite of this preparation, physiological psychology’s

greatest systematist, Wundt, turned out later to have almost noth-ing to say about internal sensibility in any of the successive en-largements of his great handbook that appeared from 1874 to 1910.
In his last edition he gave but six pages out of his 21fi5 to kinesthesis,

and but four to tickle, shudder, itch and internal pain as

representatives of the Qemeingefiihl. All in all there was, in thenineteenth century,

moresilence than

wisdom about

internal

sensibility.

In the present century there have been four chief lines of research: (1) the study of the sensibility of the viscera, especiallyof the alimentary canal, in respect of pressure, pain, warmth andcold;(2) the analysis, both physiological and introspective, of

hunger; (3) the similar analysis of thirst; and (4) the inti'ospective
description of other organic perceptions, like appetite and nausea.

Let us consider these topics in order.

Visceral Sensation
That the viscera can give rise to pain is the direct evidence from
disease and injury. The sensory content of ‘bodily suflering’ or ‘apainful death’ does not seem to be entirely cutaneous, Common

sense has long asserted the existence of internal algesia.

Weber, however, in his well-known chapter of 1846, undertook
to inquire into

the exact natureof organic sensibility.

Hie

GemeingefuU, including as it did pain, he assigned to the internal organs

and tissues, but he denied the existenceof theTastsinn inside the body. Since he was convinced that the Tastsinn
consists of the Temperatursim, theDmehsim and the Ortslnn,

this conclusion meant for him that warmth, cold and pressure, as

well as their precise localization, must occur only in stimulationof die body surface. He thought it obvious that touch is hot aninternal sense, since food disappears after it passes the pharynx

and is seldom perceived during its passage through the alimentary
canal. Thus, if the viscera lack die Tastsinn, they ought to be insensitive to temperature as well as to touch. Weber, to find out

about this matter, drank quickly large doses of ice-water and of
hot water, also jnjecting them into the colon. Ordinarily he felt onthese occasions no cold or warmth.

When the amount of water

was great and the temperature was extreme, it is true that he got

VISCERAL SENSATION

547

sometimes a faint cold or warmth, but he ascribed such sensations
to diermal conduction to orfrom the body-wall, being able attimes to obseiwe a slight change of temperature (1°C.) in a ther-mometer bound against the skin at a spot nearest the intemal
stimcilation. That, then,was Weber’s dictum; only pain and theother nondescript perceptions of the Gemeingefuhl

come fromthe intemal organs, not pressure nor wairali nor cold.
Psychologists could accept Weber’s rale and still not be dis-turbed about perceptions like hunger, nausea and suffocation because those sensations, being nondescript, might well belong to
the Gemeingefuhl. Conceivably a considerable account of internalsensations might have come to be based on introspection alone,

had doubt not been thrown on introspection as a reliable index
of the place of origin of internal sensations. It was Hilton in 1803

who first described referred pain. He called it “sympathetic pain,”showing how disease in an internal organ is often accompanied
by a pain that is localized at some characteristic place on the surface of the body, and warning physicians, therefore, against trying
to find disease in Ihc region of the pain. lie believed that afferent

nerves from tho intemal organs are in some cases so associated in
the central nervous system with particular afferent nerves fi-om

the sldn, lliat algesic stimulation at an organ leads to excitation of
nerves of pain from tho surface of the body. Disorders of the viscera
habitually give rise to pains between the shoulders, he said, anddiseases of the spine to pains in the back of the head. His finding

thus robbed introspection of its validity for the localization of or-

ganic processes. II what one feels on tire outside may ‘really’ be inside,then what one localizes somewhere mside may easily turnout to be somewhere else. Even hunger, which seems so surely to

be in the stomach, may actually depend on a lack of nutrition in
the blood, being ‘referred’ to the stomach only because the hungry
orgairiSm ought to pay attention to his stomach.

Although the late nineteenth century was not without its researches on visceral sensibility, interest in the problem did not

become acute until after 1900. Then, in 1901, Lennander published some observations on abdominal operations performed un-

der local cocaine anesthesia. He found that he got no sensation
at aU from cutting, pinching or burning the tissues of the stomach,intestines, liver, gall bladder and kidneys. From the parietal peri-

toneum, on the other hand, he easily got pain faom cutting andORGANIC SENSIBILITY

548

from heat, although not from pressure or cold. Thus he concluded
that all abdominal pain must come from the parietal peritoneum,
explaining

how colic might produce sucli tension on the peri-

toneum as to produce pain. For a few years surgeons accepted
Lennander’s conclusion as final, and, indeed, their woik seemed
to confirm it.

Presently, however, Letmander’s generalization was challenged.

Kast and Melteer in 1906 and Ritter in 1908 showed that the superficial injection of cocaine reduces the sensibility of underlying or-gans and that exposure to air also diminishes their sensitivity. Dogs,

under the effects of morphine but without other anesthetic, gave
evidence of pain when the visera were pinched or burned and theperitoneum left untouched. This discovery was also consistent withthe finding of Head, Rivers and Sherren who, presenting evidence
in 1905 that very hot or cold water introduced into the severedcolon of an operated patient produces a mild thermal sensation,

concluded that “protopathic” sensibility is thus shown to extend
to the viscera.

Meanwhile the increasing importance of the James-Lnnge theoryof emotion was disposing psychologists toward a belief in a varietyof visceral sensations. Meumann, first in 1907 and later in 1909,

undertook to examine the whole situation, reviewing the litoratiu'c,
inventorying his own visceral experience (he seems to have boon
habitually aware of his own alimentary processes), performing a

few experiments and criticizing Lennnnder, He described as different perceptions hunger, stomachic emptiness and repletion, heart
oppression and suffocation. Becher, on the other hand, performing experiments in 1908 and finding the esophagus everywhere
sensitive to pressure, cold and warmth,

was unable to discoversensibility in the stomach. Hot and cold water in small amounts

produced for him no thermal sensations, whereas amounts large

enough to yield warmth or cold were suspect as possibly affecting
the thermal receptors in the body-wall. So Becher decided forstomachic insensibility and there was, therefore, a little controversy between him and Meumann until the problem passed into
other hands.
It was also in 1908 that Hertz, Cook and Schlesinger got results

somewhat more inclusive, They
showed that the esophagus is everywhere sensitive to warmth,

similat to Becher’s, althoughcold and pressure. They aroused the thermal sensations by inject-VISGEflAL SENSATION

549

ing hot or cold water througli a thick-wallcd stomach tube which

was introduced

to different points in theesophagus, and got

pressure, not by contact, but by die inflation of a robber balloon

on the end of a stomach tube. It was muscular pressure (althoughfroitnplain'rauscle), continuing as long as the balloon was kept
inflated and disappearing at once when the air was let out. Rapid
inflation of the balloon gave rise to deep pain, an ache. None ofthese effects could they get, however, from the stomach, which

proved, nevertheless, to be chemically sensitive to alcohol, oil of

peppermint and oil of cloves. Hertz argued later that tire occasional apparent thermal sensitivity of thestomach must reallycome from the esophagus, sometimes because the stomach tube
had walls tliat were too thin, sometimes, when no tube was used,because the hot or cold water accmnulated at the endof theesophagirs before the final deglutition. Hertz also found in 1911that the colon responds as does the esophagus for die inflation ofa balloon, yielding pressiue for slow inflation and pain for rapid.

He pointed out at this time that cutting, pinching and touchingarc probably not adequate stimuli for the plain muscle of the ali-mentary tract, whereas distension is.

The present author in 1915 verified dio general conclusions ofHertz, Cook and Schlesingcr in respect of thermal and chemical

stimulation and of distension, but showed further that the stomach
is afteritaU sensible to warmth and cold. The earlier experimenters,

appeared, had failed to find thermal sensitivity in the stomach,because the gastric tissues and contents tend to neutralize thetemperature of the stimulus. In this new experiment the actual
temperature of the stomachic contents was measured by a ther-mocouple, with its wires running dirough a small rubber tube inside the larger stomach tube. Thus it turned out that 25 cc. ofwater at 60°C. would raise the contents of the stomach to 40°C.
in aboht 6 sec., producing a sensation of warmth, and that 25 cc.
of water at O^C. would lower the contents of the stomach to 30°C.
in about 6 see., producing a sensation of cold. No change of tem-

perature could with these stimuli be found on the skin of theadjacent body-wall, wher e it required 500 cc. of water at 0°C. tolower the temperature by 0.05°C.

There still remained al this time, however, a cgntradiction between common sense and experiment. Casual experience showsthat food seems to disappear after it passes the throat and may, if

ORGANIC SENSIBILITY

550

very warm or very cold, seem to reappear in the region of thestomach. Experiment, on the other hand, shows that the esophagus
is sensitive to its

lies

adequate stimuli throughout its length. Hereina contradiction;

what is its explanation? It was again thepresent author who resolved the difficulty by showing that thesensations

from the esophagus are referred either up or down(or occasionally both up and down); they seem to come either

Fig. 89.

Extehnxl Localization or Bsofiiacsal Stimulation) Boiunq(1915)The higher stimulations ara referred up; the lower, down, S murks thelevel of the stimulus (electric shock). The 25 dots on each diagram indicate
the level of the 25 localizations on Ihe chest or neck, but arc not correct as
to transverse localization which

was almost always close to the median line.

From Amef. J. Psychol, 29, 1915, 38.

from the throat or from the stomachic region. He placed in theesophagus a stomach tube carrying on its outside five metal rings,
spaced evenly, five centimeters apart. Then, producing electric
shocks at each of these positions, he had the subject localize theregion stimulated by touching the proper place on his chest or
neck. The results of this experiment are diagrammed in Fig. 88.

The esophagus, separated from the skin of the chest by the hardthoracic wall, turns out not to be associated, each point with thenearest external position on the chest. The higher esophageal stimulations are localized outside above the clavicle, the lower below

the sternum, and the stimulations in the middle either up or down
or occasionally both up and down.

The general conclusion is, then, that the viscera are sensitive.

HUNGER

5S1

but only to their adequate stimuli— as, indeed, Haller had said in
1752. Cutting, pinchingtissues,and touching arc inadequate lor most

but adequate for tlie peritoneum. Distension may excite

pressure or, if rapid, pain from most portions of the alimentary
canal. Warmth and cold ate adequate stimuli for the esophagus

and stomach, diough probably not for the intestines. At this point
the unpopular teleological argument usually slips in to increase

assurance about the thermal insensitivity of the intestines. The

esophagus and stomach can easily be stimulated thermally andmight therefore be endowed with means for thermal perception;
but why should the intestines have thermal receptors, when frombirth to death they meet with almost no thermal change except

from enemas, surgery, accidents or conceivably hara-kiri?

Hunger
The important word hunger is ambiguous. It means (a) thedesire for food and also (b) a pattern of dull gnawing pain refoi'red to the region of the stomach. The hunger pangs are almost

always accompanied by the desire for food, but the converse is nottrue,

A little food or other substance in the stomach may abolishthe hunger pangs but leave the phagoal desire remaining. A man

who is always well-fed or who has had his stomach removed may
never feel the pangs, yet often he experiences a strong urge to dine,
This distinction has long been recognized. Haller vaguely suggested the duality when, in 1747, he wrote: “We are solicited totake food, as well from the sense of pain which we call himger, asfrom that pleasure which is received by the taste." Magendie in
1817 separated painful hunger from pleasant hunger, noting thatin fasting a man may desire food while feeling no pangs. Beau-mont in 1833 drew explicitly and at length this distinction between'hunger and appetite. Busch wrote in 1858: "In hunger two
sensations must be distinguished,” and went on to show that one
isdependent upon a general condition of the nervous system cre-ated by need of the body for food, and the other upon the specificstate of the stomach. Longet said in 1861 that appetite may occur

without stomachic pains, and that these pains, when ihey dooccur, are caused by appetite and are not the cause of appetite.

One would think, tiierefore, that there could have Seen no
confusion on this matter, and yet there was. The question arose

5S2

ORGANIC SENSIBILITY

as to whether hunger is a general sensation (appetite) or spedflc

gastric sensation (the pangs).

When one man argued for the seathunger in the stomach another met him witli evidence that
hunger can exist without the stomachic pains or with the vagusofnerves to the stomach cut.

Even Magendie and Longet," whopointed out the ambiguity, took the trouble to ‘prove’ that ‘hunger’ is not gastric in origin,

For nearly a century this unnecessary

verbal difficulty impeded the clarification of the problem of hunger, for Cannon and Carlson had to make the argument about dual

meaning all over again in 1912, and Caimon found it necessary tokeep insisting upon the distinction for twenty years thereafter. In
this case, as in so many others, words have obscured ideas.
It follows, of course, that the main distinction in theories of hun-ger arose along these lines:ishunger a general or a specific sen-sation?

Magendie in 1817 lent the weight of his opinion to the theory
that hunger is general, “Hunger is produced like all other internalby the action of the nervous systesm, and it has rro
than this system itself, and rro other cause tlinn tiro
general laws of organization,’’ If the body needs alirnoiri, Its wholesensations

otlier seatslate is affected, and the nerves bear information of this state lo

the brain—that is what Magendie thought. Tire ‘seal’ of hurrger
isin the whole body or in the nervous system or, if you please,in the brain. The sensation, as regards its origin, is general

—

if,

in-

deed, such hunger can be sensation.

In 1829 Sedillot showed that section of the vagus nerves in arri-mals does not aboUsh the desire for food, thus throwing his support to the theory that hunger is general by proving that stomachic
sensations are not essential to appetite. Indirectly, Tiedemann in1830 also supported the notion that hunger is not specific by discussing in great detail the needs of animals and plants for nutriment and their ways of getting it without (at least in plaifts) the

functioning of a stomach. Similarly Busch in 1858 described thecase of a woman with a fistula just below the duodenum. Her intestine was entirely separated and no food from her stomach could

be assimilated until later when Busch had connected the two parts
with a rubber tube. She lacked, consequently, nourishment andwas obsessed by an inordinate desire for food, even when her
stomach was filled with food; but she felt no hunger pangs with afull stomach. Longet in 1852 argued that hunger is need, like tireTHEORIES OF HUNGER

55S

need for sleep or sexual need. In 1897 Roux said that hunger arises
from every ccU in the body, for it is a sign of starvation, whereas
the stomachic sensations are merely a consequence of such hunger. Bardier, in his sophisticated review of the theories of hunger

in 19G6, supported a similar theory, stating, however, tlrat this general hunger

isunpleasant, whereas appetite is pleasant. Even aslate as 1915, L. R. Milllar insisted that hunger arises,

not from

the stomach alone, but from all the organs of the body, which de-termine a condition of the blood that has an effect in the brain.
After that the work of Cannon and Carlson was sufficient to makethe distinction between sensory pangs and motived desire fairly
clear,

although some confusion

stillarisesbecause the sense-

physiologists use the word hunger to mean the stomachic pangs

and the animal psychologists use the same word for the hunger
drive, whiclr is the modern successor of the general sensation.

The theory that hunger is of central origin, a 'brain sensation,'cannot be separated from the theory of hunger as a general sensation. Magerrdie, thirrking that there mirst be a center for himger

in die brain,

and having, of course, to say how this center is ex-

cited, appealed, as

wo have seen, to the action of the nerves (andperhaps also of the depleted blood) upon the center. Others later
held similar views, like L. R. Miillor, who in 1915 echoed Magendie’s theory, pointing to giddiness and weakness in .starvationns

evidence of the widespread origin of hunger and noting that

die hunger contractions of the stomach may thus be caused by the
excitation of a center in the brain.

This theory of hunger as a general sensation with appropriate
central excitation has never been refuted, except as modem motivational psychology has made it clear diat sensationisa poorword to apply to a drive. How could it be refuted? Hunger as adrive is known to exist without the stomachic pangs; animal psychologists make full use of such hunger as an incentive. The present book, however, is concerned with the nature of the pangs,

and to those theories we now turn.
There have been five important theories of hunger as a speoifio
stomachic sensation, and we may consider tiiem in what seems tobe the order of their antiquity.
(a)

Hunger is caused by the contractions of the ^omach which

stimulate the gastric mucosa mechanicaUtj. This was Haller’s viewin 1747 and 1764. The proximate cause of hunger is "the grindingORGANIC SENSIBILITY

554

or rubbing of Uie delicate and villoid folds of the gastric mucosa
against each other, through a motion or contraction inherent in thestomach, aided by the diaphragm and die abdominal muscles.” To
this statement he added the remarks that he considered the facts

already demonstrated, that the empty stomach is so contracted
that no lumen exists in it any longer, that its normal state may berestored by congestion of the blood, and that hunger is lessenedinprolonged fast because the contractions are diminished.

He

noted furdier that in hunger “the naked villi of the nerves on the

one side [of the stomach] grate against those of the other, after amanner almost intolerable. Thus we are effectually admonished ofthe danger ensuing from too long abstinence or fasting, and excited to procure food or nourishment by labor and industry.” It is
important to note that the earliest theory of the hunger pangs, likethe latest, ascribes them to stomachic contractions.

(b) Hunger is caused by the gastric juice which sHmulates the

mucosa chemically. Haller himself suggested tliat gastric secretion

may be an auxiliary stimulus to hunger, but it was Soemmerring in
1801 who argued that this action is the sole cause of the hunger
pangs. This theory is wrong in the sense that the hunger contractions of Cannon and Carlson, giving rise to hunger pangs, occur

without gastric secretion; yet Aere is a spook of tmth in Soemmerring’s view because hyperacidity may, especially when there
is a gastric ulcer,

give rise to pains that some patients have occa-

sionally mistaken for hunger.

Once a man complained that, notbeing always able to tell hunger from indigestion, he could not

be sure whether to eat or fast.
(c)

Hunger is caused by the quiescence of the normally active

stomach. This is a logical, if incorrect, view—that the stomachshould relax when it has nothing to do. Erasmus Darwin first madethe statement in 1801. Johannes MiiUer formulateditagain in

1838; “the aliment is an ‘adequate’ or ‘homogeneous’ stimulus to

the digestive organs; when this stimulus is wanting, the state of
the organ is made known to the sensorium by the nerves.” Muller

has been said to have equated hunger to a “negative sensation,” theabsence of the perception of the normal aliment, but that critioism
has no more validity than the argument that black is not a sensation because ij is due to the absence of light. The trouble with
Miiller’s theory was only that it turned out to be wrong.

(d) Hunger is caused by the turgescence of the gastric mucosa.

THEORIES OF HUNGERThis is Beaumont’s vascular theory of 1833.

SS5

He argued against—

Haller’s friction theory, holding that the hunger pangs^but notappetite—would bo caused by the distension of the vascular vessels, or possibly of the gastric glands, in the stomach.

{eY Hunger is caused by certain slow rhythmical contractionsof the stomach which, having a specific temporal pattern, can be
identified as hunger contractions. This

1912, which turned out to be rightits

isCannon’s discovery of

We need therefore to examine

development in some detail

The theory had been anticipated, in a way, by Haller and E. H.
Weber. Haller, as we have seen, held that the hungry stomach is
not quiescent but in continuous contraction, a fact that he re-garded as fully demonstrated in 1764. He was wrong, however, in
supposing that the pangs arise from the rubbing of the folds andvilli

upon one another. The pangs are muscular, not tactual, sen-sations; contraction, not contact, is their adequate stimulus. Webersaid in 1846 that “the sensation which we call hunger” is due to“strong contraction of the entirely

empty stomacli, which com-pletely obliterates the gastrie cavity,” but he did not detail his

evidence.

In 1892 Nicolai showed that hunger is allayed by the introduction of all sorts of substances into the stomach: food, water, saline
solution, indigestible material or a

stomach tube. It is also in-hibited by the act of swallowing. lie knew nothing about the contractions,however.

Boldiieff, a pupil of Pavlov’s using Pavlov’s methods, studied in1905 the gasti'ic contractions of stamng dogs. He introduced arubber badloon into the dog’s stomach so that the contractions
could be recorded on a kymograph—the first use of this technique. His paper shessed the periodicity of all alimentary functions, describing the hunger contractions, but without indicatingthat they are related to the periodic hunger pangs. He noted fur-ther that the contractions are abolished by gastric juice in thestomach.

In 1910 Cannon and Lieb verified Nicolai’s observation drat

swallowing inhibits the stomachic contractions.

Then in 1912 Cannon with A. L. Washburn, using Boldireff’s
technique on Washburn as a subject, established Jthe correlation

between the hunger pangs and tiiese slow contractions. Fig, 89
illustrates their method.

With a balloon in the stomach its con-

ORGANIC SENSIBILITY

556
tractionswere recorded on the kymograph, while Washburnpressed a key to indicate on the same record the appearance anddisappearance of the pangs. Another tracing recorded the move-

ment of the abdominal muscles to show that they ar6 not the causeof the contractions or tlie pangs.

"

Immediately Carlson verified this discovery and amphfled it.

He had available a patient with a gastric fistula whose stomach
could be reached directly ihrough an opening in the abdominal

Fro. 89.

Hongbb CoNraAcnoNS of the Stomacb: Caniton and WasiiBUBN (1912)

Ai kymograph record of volume of stomacliic balloon, B. C; time recordin minutes,

D; record of subject's signals, showing when he felt hunger

pangs. E; record of contractions of abdominal muscles from pnernnographabout the waist, showing that the hunger contractions are not contractionsof the abdominal muscles.

From Cannon, in Foundations of Experimental

Etycholog!/, 1929, 437.

wall. Carlson noted that the synchronism of hunger with contractions did not quite prove that it is the contractions that cause hunger. If the hunger had been of central origin it might have been

the cause of the contractions. Carlson, however, supplementing
Nicolai’s finding, made out a list of inhibitors of the contractions;sapid substanpes in the mouth, chewing, smoking, swallowing,

and the ingestion of warm water, cold water, coffee, tea, beer orwine. When these events occur, the contractions stop and theHUNGER CONTRACTIONS AND DRIVE

5S7

pangs disappear^^Hencc the contractions are the cause of thehunger sensationy
Since then thae have been many verifications of these facts,

most of tliem’ by Carlson and his pupils. Rogers and Martin in
1926 also verified them, using X-ray projections to observe thecontractions instead of tire balloon. There is now no doubt llrat

tho contractions cause the pangs. Do they also cause the hunger
drive?

In respect of this point Wada showed in 1922 that restlessness

and activity tend to accompany the hunger contractions, A subject sleeping with a balloon in Ids stomach tends to move and tosswhen the contractions occur, For the waking subject the balloon
indicates that the hunger contractions are apt to be accompanied

by maximal effort in musadar perfoimance, and maximal achievement in intellectual tests. Richter in 1927 found that rats, accus-

tomed to being fed at two-hour intervals, are maximally active atthese times even when no food is given them. He drew the oonolusion that the hunger conti'actions arc therefore the seat of thehunger drive as well as of the hunger sensation, Others have madetho samo assumption, but such a broad conclusion seems to ignore
the history of tho knowledge of hunger as an ambiguous concept.
If tlio hunger drive

depend upon hunger conlraolions, then mostfood-seeking must be under tire direction of some other drive. It
isalso not clear that hunger pangs act differently from the othermUd pains or potential distractors which are known to spur attention and effort.

Nowadays hunger is slipping back to its alternative meaning, tothe denotation of what Beaumont and Cannon and Carlson cdled
appetite.

The change from sensation to drive has come about

gradually in animal psychology. At first, around 1900, hunger was

simply the incentive used to get animals to solve a problem. In

1908 M, F. Washburn in her The Animal Mind listed hunger as a“physiological condition” under which behavior changes, and her

account in 1917 was similar. Watson classified hunger in 1914 as

a “stimulus to activity.” Miss Washburn in 1926 called it a drive
or incentive, and in 1936 included it in a chapter on drives andincentives. It was always obvious tlrat the degree of hunger canbe measured by the time for which an animal is dej)rived of food,and Tolman and Honzik in 1930 used this quantitative definition
to specify the strength of the hunger drive. In 1934 Elliott meas-

ORGANIC SENSIBILITY

558

ured degree of hunger inversely by the amount of the ration fed
the animal, and Skinner determined the strength of hunger by therate at which the animal eats. In all this work on animals hungeriswhat Beaumont called appetite. Food deprivation determinesand strengthens it. Rate of eating measures it. Whether the'stomach contracts or not is largely irrelevant. An animal with insufficient food can be trusted to try to get food even though his hun-ger contractions are inhibited by any of the means which Carlson
listed, just as a

man can be tmsted to go on with a dinner after die

soup has stopped his hunger contractions.

Thirst
The history of the psychophysiology of thirst has, indeed, little
to teach us that we have not already learned from the study ofthe psychophysiology of hunger. Thirst as a ‘sensation’ has always

been described as dryness of the mouth and throat. It is not present

when the mouth is wet, but it is not relieved for any length of time
unless water is intooduced into the body. Loss of water from flio

body by sweating or excessive secretion induces thust, Introduction of water into the intestines or the veins without wotting themouth reduces thirst. Hcnco there have boon those who argued
that thirst is a general sensation, in spite of the localization of tlio

sensation in the mouth. Nevertheless, anesthetization of the oral

and pharyngeal membranes implies a local ‘seat,’ since it abolishes
thirst without water. The confusion

here is exactly analogous to

the similar dilemma in the case of hunger. Cannon has, however,advanced the problem somewhat farther than anyone has yet done
for hunger, for he has shown why the mouth becomes

iy whenthe water content of the body is diminished, whereas the cause of

the hunger contractions is still uncertain.

Much less has been written about thirst than about hunger; yet
the standard sources aU discuss it, at least briefly. Haller, in 1747,
diaracterized thirst as dryness of the tongue, fauces, esophagus

and stomach He said that it would be relieved by an increase of
the water in the blood which would restore the moisture and secre-

He noted how perspiration increases thirst,
how acid liquprs relieve it more than plain water because theytion to the mouth,

provoke secretion of the humours.

Dnpuytren and Orfila (both oa, 1821) showed that introduction

THIRST559

of water into the veins of thirsty dogs abolishes the desire of theanimals to drink, The great Claude Bernard in 1856 described anexperiment on a dog with a gastric fistula. Wlien this dog, after
being deprived of water, was permitted to drink and the water

was allowed to run out of the stomach through the fistula insteadof into the intestine, the animal kept on drinking and drinking
until (apparently) too tired to continue, whereas, when the water

was allowed to pass into the intestine, the dog soon satisfied himself. Another important ease

was described by Lepidi-Chioti andFubini in 1885, who told about a boy with polyuria who passed
great quantities of urine. Unless he was allowed to drink constantly, he became tormented by a severe thirst. In 1931 Greger-sen verified experimentally what Haller had remarked from com-

mon observation, that profuse sweating increases thirst. He also
showed (1932) that animals do most of their drinking right after
eating, explaining tliis phenomenon as due to the loss of water inthe digestive secretions. The water is secreted in the various digestive juices, is mixed with the food, and is presumably not entirely

rcasshnilatod in the intestines. There seems not to have been for a

century at least much doubt that the primary cause of thirst is lackof water in the bodily system,

Thore can be no doubt that the thirst drive is more closely associated with the thirst ‘sensation’ than the hunger drive is associated with tire hunger pangs. Lepidi-Chioti and Fubini showedin 1885 that the thirst of their patient was immediately relievedby painting his throat with cocaine. Valenti found in 1910 that
dogs, deprived of water for several days, refused to drink when

the backs of their mouths had been cocainized. Nevertheless, there
is an appetitive thirst.

The present author discovered in 1915 thatmild thirst is consciously little more than “going to get a drink.”

The thirsty person finds himself with his hand on the faucet oron the knob of the door that leads to the faucet, when he remembers that he is performing an experiment and is not allowed todrink. Winsor discovered in 1980 drat a man, deprived of water,

may presently develop a strong craving for liquids, even thoughdrpess of the throat and thus the thirst ‘sensation’ are prevented
by the salivation due to the constant chewing of tasteless gum. He
called the oral sensory thirst "false thirst,” and the craving thatdevelops with a moist mouth and dehydrated system “tme thirst.”
The distinction here between ‘false’ and ‘true’ is analogous to theORGANIC SENSIBILITY

560

question as to whether hunger is the pangs of the gastric contractions or the appetite of desire for food.

The saliva furnishes the link between the water content of the
body and the moistness of the mouth. In 1852, Bidder and Schmidt,
after tying the salivary ducts in a dog, found tliat he was always
ready to drink unless his mouth was kept moist by being kept
closed.

A dry mouth stimulates saUvary flow. Zebrowski showedin 1905 that more saliva is secreted when the mouth is open thanwhen it is closed, and Pavlov in 1902 that salivary secretion isgreater for dry food than for moist.

Cannon took up the problem of thirst in 1918. He measured
salivary secretion by collecting the saliva when tastelessgum ischewed for five minutes. By this method he found that deprivationof water increases salivary flow and thirst very little in the first

four hours, but that thereafter salivation diminishes and thirstincreases.

When the organism in this stale ingests water, the orig-

inal satisfied condition is rapidly restored.

that increased perspiration

He also verified the fact—tie body was wrapped in warm

blankets—reduces the flow of saliva and increases the thirst. Wlion
the saliva was ahnost stopped

by a subcutaneous injection ofatropine, tliirst became intense although tho water content of the

body remained, of course, undiangod. Sb'ong emotion loo may inhibit salivary flow and create a thirsty mouth. In fear the tongue
cleaves to the roof of the mouth because tiro saliva is diminishedand sticky. In the ancient ordeal of rice, the fearful person, who,
because of his dry mouth could not swallow tho rice, was adjudged
giulty. Aeneas in fear, could not speak:“Vox haesit in faucibus.”

He needed more saHva.
There have been various confirmations of Cannon’s conclusion
about thirst since he first made it, but they have not changed theessential picture.

As to the theories of thirst there have been, of course, thbse who
contended that thirst is a general sensation. Schifi ( 1867 ) was oneof the first to make this argument as he made it also about hunger. He held that the pharyngeal sensations are no more of theessence of thirst than are ie sensations of heavy eyelids of theessence of sleepiness. Mayer in 1900 reasoned that deprivation ofwater produces thirst by increasing the osmotic pressure of thebbod, but Wettendorfl (1901) pointed out that osmotic pressure
is raisedmuch more slowly than the thirst comes on. L. H. Muller

THEORIES OF THIRST

561(1924), who also held that hunger is of central origin, proposedthat thirst must depend on the direct stimulation of a brain center by the stale of the blood. Tlrese theories may be correct as ofappetitive thirst which occurs when tiro oral cavity remains moist,

but Garmon’s view would still seem to be correct for strong thirstwith the sensory accompaniment that occurs when the oral membranes are too dry.

In general, then, it would appear that the need of the body forwater is more often accompanied by the oral sensations of thirstthan is the need of the body for food by the stomachic hunger
pangs. Aldiough many people are so well fed as never to feel thehunger pangs, few are so well watered as never to experiencethirst.

On the other hand, most ordinary drinlting under the con-ditions of civilization is appetitive with a fairly moist mouth.

A

man may get himself a drink with little consciousness of a dry
mouth; nor did Cannon find much diminution of salivary flow in
the first four hours of his experiment.

Organic Sensory Patterns
There were two characteristics of the thought of the ninoteenlhcentuty psychologists which affected their attitudes toward the

problem of organic sensation. The firel was that they were looking, with one eye on the chemists’ periodic table of elements, for

new sensory qualities. Touch was resolving itself into pressure,pain, warmth and cold. Might not hunger or dizziness or sex, they

wondered, reveal stiU otlier qualities, new ‘sensations’? The second
characteristic was that they expected conscious needs to be repre-

sented by specific sensations. If the organism consciously seeks
food, it must know—that was the lesson of British empiricism—that it needs food, and what more natural than that an important

speciahneed should have its special sensation, just as pain, as they
thought, gives knowledge of danger? Thus they held to a poorly

recognized isomorphism between need and sensation, between
function and quality, and it seemed to them as if salt-hunger or

sex-hunger must somehow have each its own peculiar quality,
such that the mind, apprehending, as it were, a specific nerve
energy, would know what it had to get its organism to do.

A great many of the physiological states and needs were recognizedly conscious: thirst, hunger, nausea, the calls to defecation

ORGANIC SENSIBILITY

502

and urination and the processes themselves, sex, dizziness, andnot new qualities ^were added
suffocation. Other perceptions——

from time to time to the common list.

Meumann in 1909, on the basis of his own introspection and an
examination of the clinical literature, argued that, besides Inuiger,

both emptiness and repletion are recognizable stomachic states.

To them he added oppression as a cardiac sensation and suffocation as a pulmonary sensation, but it is tmo that he was not pri-marily concerned with the question of quality so much as withthe discriminability of these perceptions. The present author in1915 sought to analyze thirst, hunger, nausea, and the excretoryneeds and processes by arranging the proper situations and obtaining introspective descriptions for them. Those results revealed

various unique spatial-temporal patterns made up ot the familiar
qualities—deep pressures, deep pains and sometimes warmth andcold.

In 1915 Carlson formed the opinion that appetite has its peculiar
sensory basis. He and Braalladt, demonstrating the varied sensibilityof die gastric mucosa, noted that the introduction into ahungry stomach of “modci'ately cold water, beer, wino, weak acids
or weak alcohol” not only stopped the unpleasant hunger oonlraotions but also gave rise to a pleiisant “^aracteiistio sensation,"

which was “the exact opposite of that caused by the hunger contraction”

and which stood out from tlie hunger pangs by “suc-cessive contrast.”

Miss Luce and the present author tried to confirm this findingof Carlson’s in 1917. They set hungry subjects before meals, in-hibited their hunger contractions with a little food, and bade diemintrospect and eat and introspect again.
it turned out,

Some of dieir subjects,

were pleasandy aware of the food when it reached

the stomach, thus confirming Carlson on the sensitivity of die gastricmucosa. The bright pressures involved in these perceptions

were, however, neither unique nor universal. The chief characteristic of appetite seemed to be a serial behavioral pattern, The needfor food expressed itself first in a resdessness of the subject’s handto take the food; then, if the hand took the food, in its tendency
to move it toward the mouth. Thereafter the other events of in-gestion ran off smoothly. With the food at the mouth the saliva

flows and the lips open, the food goes in, mastication ensues, thefood passes to die back of the mouth, deglutition follows. WhenORGANIC SENSORY PATTERNS

563

Carlson’s ‘sensation’ of appetite was felt at all, it came merely as

the final perception in this chain of events. In other words, the ex-periment revealed a need, which was satisfied by a series of actions, most of,which came to consciousness as perceptual patternsof tlin usual somesthetio qualitios. Just as mild tlurst is going to

get a drink, so appetite is merely latog and ingesting food.

Such is die story of one defeat of nineteenth-century elementism.
Its atoms—atleast what it hoped might prove to be atoms—turnedout to be complex molecules; the plausible qualities of organic
sensibility

were unmasked as needs. In the twentieth century it

eventually became apparent that the organism behaves first andfeels

afterward—-feels its behavior, just as James, speaking of

emotion, said it does.

Although recapitulations are tedious, perhaps decency requiresthat we should now write epitaphs for eleven organic qualities.

Here they are;(1) Thirst, as we have seen, is the perception of the dryness ofmembranes at the back of the moutli (Cannon, 1918) and consists of a pattern of pressures and warmths, with pain added when
Uto thirst is extreme (Boring, 1915).
tlian behavioral,

A mild thirst is less conscious

being primarily the automatic act of getting adrink (Boring, 1915). There may also be in extreme dehydrationa behavioral ‘tiiirst,’ even though the mouth be wet (Winsor,
1930).
(2)

Hunger is die perception of the hunger contractions (Gan-non, Carlson, 1912) and consists of a pattern of muscular pressure

and muscular pain (Boring, 1915). Behavioral hunger without
the pangs is in these pages called appetite,(3) Appetite is the perception of the normal process of getting

food and ingesting it (Boring and Luce, 1917), and occasionaUy
this process

ends in pleasant bright pressures from the gastricmucosa (Carlson and Braafladt, 1915).
(4) Emptiness of the stomach can be perceived(Meumann,1909), but the pattern is most easily recognized when it includes
other factors, like general muscular weakness.

(5) Repletion can also be perceived (Meumann, 1909).
(6)

Nausea can be perceived, and includes gastric pains, which

may in exceptional circumstances be confused with hunger, and,
when extreme, the pressures and aches of incipient or actual vomiting; but it is also attended, when strong, by dizziness, blurring of.

ORGANIC SENSIBILITY

564

muscular weakness, circulatory disturbances, sweating,vision,goose-flesh and cold (Boring, 1915). Any one of these secondary

phenomena may come by itself to mean nausea to the person who
thinks much about his own digestive processes.

(7)

The excretory needs and processes are all perceived as pat-terns of pressures and sometimes pain (Boring, 1915).
(

8 ) Sexual needs and processes have not come under controlled

experimental introspection, but the evidence is that tliey too areperceptions like the others (Titchener, 1910), perhaps with pleasant pain more involved in the male process than has usually been

supposed. The histological search for lust receptors has not led
to certain results.

(9) Dizziness, as we have seen, is the kinesthetic perception ofreflex processes in the eyes, neck, arms, viscera and vascular sys-

tem induced, it would seem, by stimulation of the ampullar organsof the semicircular canals (Griffith, 1920).

(10) That cardiac oppression is perceived is the evidence ofclinical observation(Meumann, 1909), but Ihero is no reason tosuspect a novel quality hero, and the location of the receptors is

not established.
(11) Suffocation is the porcoplion of Ihe behavior of tho or-

ganism in its effort to get more air ( Meumann, 1909 )So died many extra conscious quaHtics. If to Aristotle’s five we

had added three more for the skin, and some others for proprioception, then these eleven might have been, let us say, the twelfth

to the twenty-second ‘senses’—liad they lived. Instead they under-

went such metamorphosis that we are now pretty sure thattwentieth-century psychology is not like nineteenth-century chemistry.

Notes
In

generalseeoigans, in his

Human Physiology, IV,sensi-

trans. 1917,

57-125; E. von Skram-accounts

theintemd (mostly kinestlietic)
bility in die handbooks:

C. S. Sber-lik,

Psychophysiologlo der Tastsinne,

The muscular sense, in E.
A. Schafer’s Texl-Bool< of Physiology, 1900, II, 1002-1025; W, Nagel,
Die Lege-, Bewegungs- und Wlder-

ArcK ges. Psychol, Erghd. 4, 1937,

his

own

Physlologfe

deswell documented with references tothe literature. To them must be

Mensdhen, III, 1905, 734-806; L.
LuoUmi, Sensibility of the internal or-added the excellent review by V.
Henri. Revue gAnerale sur le sens

lington,standsempSndungen,

Bandbuchdet-

in

Sll-898, which is especially full lor
the muscle sense and the perceptionof posture. All these accounts are

NOTES
Ann^e pmjchol, 5, 1898,
398-557, which contains an anno-

S6S
2

musciilaire,thetated bibliography of 391 titles.

mnsculor sense is treated on pp.
145-156, a section whiclr gives theillustration of the mother with theCreation.

anestlietic

Deep Sensibility

In

ed.,

1835,

arm, mentioned

tire

the

in

On Bell and tire significance oftext.

If tins term is Ihnited, as it wasby Head, to the sensibility of thehis contribution, see L.

tela subcutanca, tlrus excluding thethe history of physiological psychol-andmechanism,
then the proper reference is H. Head,
H.
H.
Rivers and J. Sherren, TheW.
afferent nervous system from a newmuscles

articular

Brain,

aspect.

28,

in

nerve

99-115iA human experi-Rivers and Head,

ment

1905,

division,

ibid.,ogy) Fsychol

217,

Neu-

esp.

Carmichael,a contribution toRet).,

204-209,33, 1926,

On

the188Bell-

Magendie law, see Carmichael,op.

191-198; E. G. Boring, A History of Experimental Fsychologt/,
at.,1929, 35-38, 44.

On the Muskelslnn after Bell, see

31,1908, 323-450, esp, 355-367! bothCharles Bell;

Sir

J.

Miiller, Handbuch der Physlologle

foWj/, 1920, 1, 55-65, 225-329, esp,des Mensohen, 1838, Bk. 5, sect. 5(pp. 1329-1331 in Eng. trans.);

246-256,

E. H, Weber, Der Tastsinn und das

reprinted in Head, Studies In

Gcmeingefuhi, in R, Warner's Handwdrterbuch der Physiologie, III, ii,
1846, 580-584 (pp. 144-150 in ihe

Muscle Sense
On

history

tiro

of

tlie

muscleWorksof Thomas Reid with Notes and Vissense, SCO William Hamilton,

sertatlons,ed„ 1846, 867-809, or

11905 reprint).

On the description of the muscle
spindles by W. Kiiline in 1863, vide
infra under Einestbcsls.

samo pp. in 3 cd., 1852; V. Ilcnri,
op. clt; 1898, 408--413i Luclanl, op.
at., 88 - 100 ,Explicit

innervation, see William Hamilton,

Flujslologfe

op.

beforeSteinbuen,

Belirug

zur

der Sinne,

1811,[n.v,];M.

F. X.

Anatamle gdniiale appllqude i la phtjslologie et d la modecine, 2 ed., 1812, U, art. 3, sect. 2,
pp. 263-266, [n.v.], and T. Brown,
Bichat,tlie

On tho history of sensations

Bell

ol

senstfillity

Lectures on

Sensations of Innervation

muscukr
were J. G.

proponents

Fhllosophxj of tireof1846 or 1852, 884-807; H.
The Brain as an Organof the Mind, 1880, 691-700. For acit.,

C. Bastiau,

genemldiscussion,

see

W.

James,

Principles of Psychology, 1890,

II,

492-522; Luciani, op. at., 100-106.
Henri said tliat the doctrine of

Human Mind, 1820, I, 498-503 etsensations of innervationpassim. The citation of Bichat is due

per on tlris topic is On Ure nervous

by Steinbuch, op. cit., 1811, 30-76,[n.v.], quoting him at length, but
it seems from these quotations as if
Steinbuoh’s Bewegungsempfmdungen resembled more nearly the ideas

which connects the voluntaryof ideomotor action than sensations

toHemi: and the passage does notoccur in Bichat’s 1 ed„ 1301.
Charles Bell’s most important pacircle

was begun

who believed

muscles with the brain, Fhil. Trans,,of innervation. Others

1828 (ii), 163-173, See also his The
Hand: Its Mechanism and Vital En-

inthe sensations of innervaOon, oratleast entertained the hypothesis

dowments as Eoincing Design, 1833.
[n.v.], which is Bridgewater Treatise
No. IV on tire Power, Wisdom andMiiller, Handfavorably, were;J.
buch der Physloloffe des Menschen,
Bk. 5, 1838, sect. 5 (Eng. trans., II,

Goodness of God

1329 f.); Hamilton,

as Manifested in

loo.

at.i

C. F.

ORGANIC SENSIBILITY

566

W* Ludwig, Lehfbuch der PhyiHologie des Uenschen, 1, 1852, 359-362,
esp. 361; W. Wundt, Vorlesungeniiber die Menschen- und Thiefseele,
1803, 1, 221 f.; Gnmdziige der pliijsi-

covery of the Vater-Pacini corpuscles
sometimes called VatcFsche(stillologischen Psychobgle, 1 ed., 1OT4,

not Filippo Pacini '(1812-1883)
gave the full account of his rediscovery in his Nuooi organi scoperti
nel cotpo umano, 1840, [n.v.]. See,on the contributions of the two men,
G. Herbst, Die Padni’schen Korper
und ihre Bedeutung, 1848, [n.v.].

278, 318; 6 ed., II, 1910, 30; A.
Bain, The Senses and the Intellect,

2 ed„ 1804, 92-95 (not In 1 ed.,1855); H. Helmholtz, Handbuch derphysiohgtschen Optik, HI, 1866,

3 ed.. Ill, 1910, 203 f.,

598 i, 605(

209; Eng.

trans.,

HI,

1925, 2441.,

Korper) by Abraham Vator (16841751). I do not know whether Vater
had published his findings earlier orOn the localizadon of these corpus-

250); G. H. Lewes, Motor-Ieelings
and the muscular sense, Bratn, 1,
1878, 14-28 (be also argued againstcles

the Bell-Magendle law and invented

zum sogenannten Muskelsinne, 1865,

at the joints, see A. Bauber,
Voter sche Kdrper der Bander- undPeriostnervenundBeziehungihre

Untersuchungenthe concept of fccuirenf Impulse in[n.v.];

order to get sensations from motor

Vorkommen und Bedeutung der Va-

nerves); E. Mach, Analyse der Emp-

terschen Korper, 1867,^dungen, 1886, 57 f., 65-69 (somewhat

modified,however,

in

later

eds.).

As finding sensationsof innerva-

an unnecessary addition to themuscle sense, see 0. Landry, Traiid
complet des pardtysies, 1, 1859, 213-

tion

316; H. C. Bastian, On the "muscusense” and the physiology of

lar

med.

1869 (1),
SOBSIB; The Brain as an Organ of theMind, 1880, 541-547, 091-700; D.

thinking,

Brit.

I,,

394-390, 437-439, 481-463,

Perrier, Functions of the Brain, 1870,

219-229; G. E. Muller and F. Schu-

mann,

Ueber

die

psychologlschen

Gnmdlagen der Vergleichung gehobener Gewichte, Arm. ges, Physiol,

For A.

Khllikcr’s

das

fiber

[n.v.].

descriptionofNeruenbiib'pscben, whioh hedrought were growtlr centers, sec
his Ueber die Endiguiigeii dor Nervcn in den Muskcl cl^ Frosehos,Z, wiss. Zool, 12, 1863 (tiro paper
was read Sept. 5, 1862), 149-164.
the

For

W. Kilhne’s further descriptionof tho buds, Uio assignment of thename muscle sjdndles io them, andbis correct guess as lo their function, see his Ueber die Endigimg dor

Nerven in den Muskeln, Arch, pathol Anat. Physiol Idin. Med,, 27,
1803, 508-533, esp. 520-529; Die
Muskclspindeln, ibid., 28, 1863, 528538. The second paper is the complete account. A. Ruffini proved the45, 1889, 37-112, esp. 80-91; James,

spindles neural in Sulla terminazione£. B. Delabarre, Ueber
Bevoegungsempfindungen, 1891, 10-

nervosa nei fusi musculari e sul loro

81.

Lincei, Cl. sd., 5 ser.,

loc,

cit,;

signlficato

2,

Kinesthesis

fisiologico,31-38; French

Biol,

18,

1893,

Atti
1,

Accad.

1802, sem.

trans.. Arch,106-114.

ital

C.

S.

Sherrington proved them sensory inOn the substitutton of the wordkinesthesis for muscular sense, see

H, C. Bastian, The Brain as an Organ of the Mind, 1880, 540-544,

On

the anatomical constitutionofnerves of skeletal muscles witli remarks on the recurrent fibres in theventral spinal nerve-root, I. Physiol,

5^.

17,

G. Lehmann; De consensu par-For the recent evidence on the func-

tium corporis humni, 1741, In.v.],
is said to have described the dl^tioning of these spindles as stretch-

esp.
].

1894,

211-258, esp. 237-248.

receptors, see J. F. Fulton and

J.

Pi-

NOTES
SnScr,

A nolo concerning llio prob-

S67

Leipzig,

1889, 369-502 (Ges. Ab-able lunction of various affcrenl end-

handl,

II,

organs in skeletal muscle, Amor.

Snppl.,

1889,/.

%fiol., 83. 1928, S5d-562j B. 11.
C. Matthews, 'The response of asingle end organ, I. ThjsUil., 71,
1931, ^4-110;

The response

97-200); idem, ibid.,141-218 (Gee, Abhandl, II, 201-281). Tire second
reference deals with passive move-

ment andincludesthe limens forathe joints; the third paper considers

muscle spindle during active contraction of a muscle, ibid., 72, 1931,
153-174. On the history of this dis-weight and resistance, position andactive movement.
G. A. B. Duchenne de Boulogne

Handbuch

was the prolific author of muchwork on the electrical stimulation

covery, sec A. ESUiker,

ofdel Gewehelelwe des Menschen, 6ed., I, 1889, 394-408; Sherringtoa,
op. cit., 238 1.; J. F. Fdton, P/ijsloI-of muscle,

electrical therapy oftlie

ogp of the Nerooos System, 1938,

muscular pathology, and la conscience muscuhUre, as he called it,

7-18, era. 7-9.

meaning the capacity of the patient

On

the

spindles indiseoveiyofthetendon, see A.

Golgi

Rollelt,

Uobor einen Nervenplexus und Nervenendigungen in eincr Seline, Sitzmgsber, AKod, Wise, Wien, math.naturw. Cl., 73 ( 3), 1876, 34-55;
C. Golgi, Sui nervi del tondini;

un uuovo organo nervoso lerminalo
musculo-tcndinco, Mem. Accad. Scl.
Torino, 32,

1880, 350-385;

G. C.

to

move accurately without muscle

and thus presumably in terms of sensations notin the muscles (at the jointP). See
his Faralysie de la conscience musculaire ou de Vapiitude mortice indipendante de la me, 1853, [n.v,],
for tlie early evidence and the casedied in Ihe text, and also in gensensations or vision,eral bis

De MecMsation localisee etHuber and L. M. DcWllt, A contribulion on nerve torminalioas inde son application h la phystologie,
i la pathologie et kh therapeuttyue,

Iho ucuro-lendinous nerve-organa, 1.

1855,

comp. Neurol, 10, 1900, 159-208.
Tlie five lexis on kinesthesia andmovement, jnuhlishcd in 1887 to

14. Also on the relation of muscidar
to articular sonslbility in the percep-

Das kdrper-

buiy. Does the sensation of move-Uche Ceflihl, 1887; H. Beaunis, Lessensations internes, 1889; E. B. Delabarre, Ueber Bewegunesempfind-ment originate in tlie jointP, Amer.

mgen, 1891; A. Goldscholder, Physi-

BewegungbelAnasthesie

elnes

1003, are:

E. Kroner,des Mushelsbmes,

ologtewhich

isGesammelte Abhandhngen, 11,1898; R. S. Woodwerth, Le mouaement, 1903. There is an excellent

his

or

[n.v.].

2

1861, chap.

cd.,

tion of movement, see

W. B, PUls-

I Psychol., 12, 1901, 346-353; A.
Striimpell,

Ueber die StBrungen der

Stickverletzung

voUstiindlger

fast

Armes

durch

Hilekenmarks,

desDeutsch. Z. Neroenhellk., 23, 1902,
1-38.

For G. E.

summary of the status of psychology

Milllerand F. Schu-in respectof kinesthesls in E. B.

mann on the motor Einstellung, see

Tltchener,

A Text-Book of Psychol-

theirogy, 1910, 160-171.
For A. Goldscheider' s work, see his
Ges.

Abhandl,, op.

ott.

The threemost important papers, all reprinted
there, are: Ueber den Muskelsinn

und die Theorie dcr Alaxle, Z. klin.
Med., 15, 1888, 82-161 (Ges. Aihandl.,

II,9-89); Untersuchungenfiber den Muskelsinn, Arch. Physiol

Ueber die psychobgischen
Grundlagen der Veimeichung gehobener Gewichte, Arch. ges. Physiol,
46, 1889, 37-112, esp. 42-63,

For

W. Wundt's inlrodnetton ofstrain and relaxation into the theoryoffeeling,

Psychoh^,

see

his

Grundriss

1896' orEne.

sect 12-13; Gmndzfige&

ohgisdien

5

Psyidtologle,d^trans.,

physl-

ed.,

If,

568

ORGANIC SENSIBILITY

1902, 283-369, or 6

cd., II,1910,

274-283.

On conscious aulludes see, first,
E.

B.

Lectures on the

Titchener,

Expeiimental

Psychohgy

ofthede Bureime, The labyrlntlilno andpostural mechanisms. Handbook ofGeneral Experimental Psychology,
1934, 204-248.

Erasmus Darwin’s Mocount of verZoonomta, the Laws

Thought Processes, 1009, 1S7-194.

tigo is in his

Then, for the study cited in the text
from Titchener’s laboratory. H. M.
Clarke, Conscious attitudes, Amer.
J, Psychol, 22. 1911, 214-249, esp.
218-221. Other rmresentativo intro-of Organic Life, I, 1794. 227-239;
hut the fuller account of rotationand the negative apparent aftereffect does not appear until tire 3

spectivestudiesRom Cornell andshowing the

ed..

340-

327-358. esp.

1801,

I,

347.
J.

E. Pin-ldnje’s contributions toimportance of kinesthesis in sensationistic introspection, are T. Okabe,

tiresubject of vertigo are not easilyAntiiigeClark Universities,

experimental

all

study

of

belief,Md., 21, 1910, 583-596; E. Jacobson,

On meaning and understanding,(bid.,

5S3-S77;

1911,

22,

E.

L.

Woods, An experimental analysis of
the process of recognizing, ibid., 26,

313-387;

1915,

process of

S.

C. Fislier,generalizingTheabalracilon

and its product the general concept,
Psychol Monogr,, 21, 1918, no. 2,

The first paper

accessible.

naherenzur

Schwindels

aus

Then

three

papers79-125,

read

to

and

the

Breslaureported

kind.

Kultur, nalurw.

by

its

182S;

no.

10,
also

Sekt.,

no. 4,

1825; no, 2,

1826;

respectively

Ncite

Breslaner Zeilung, aussororacnlliclio

Proprioception
Sherrington and propriocep-

tion, see F.

1820,

secretary; Bull Schlos. GesaU. voter-whlcb areOn

6,

1825-1826 he hadinGesellschuft

desheautognostisclren

Staates,[n.v.].

Bei-

Daten, Med. larhb.

[introspective]

Oeslerr.

is

Kgnntniss

W. Mott and C. S. Sher-

upon tire influence of sensory nerves upon movement and nutrition of Ure limbs,
rington, Experimenls

Beilage, no. 86, 1825; no. 8, 1826;
no. 43, 1826. None of tlieso originals

have

I

seen, butthey areprinlod in order with

these

all

ro-

refer-

ences in y. Delage and H. Aubort.
PhysiologischeStudien ilber die
110-122, The

Proo. roy. Soc„ 57, 1895, 481-488;
Sherrington. On the propriooeptive

firstsystem especially in its rmex aspect.

larhesber. Schles. GeseO. vaterldnd.

The In-Kultur, 1825 (1826), 32 f. Tire fifth

iegrattve Action of the Neroous Sys-

paper is Ueber die physiologisehe
Bedeutung des Sehwindms und die
Beziehung desselben zu den neuesten Veisuchen fiber die HimfuncUonen, Mag, ges. Heilk., 23, 1827,

Brain, 29. 1908, 467-482;

tem, 1906, esp. 129-132, 338-349;
F. Fulton, PTiysioiogy of the Neroous System, 1938, 7-11, 156-163.

J.

Oiientiemng,

paper

M.

A full and detailed account of
C. R. Grif-

is

fith,

An historical survey of vestibu-

larequilibration.

1575

of

Illi-

which gives atitlesfromnois, 20, 1922, no, 5,bibliography

Unio.

Bull

also

summarizedin284-310,

Vestibular Sensibility

vestibular sensibility

1888,

is

1701

fire

P,

J.

Flourens’ discovery offunction of the semicircular ca-

nals is found in tire following places.

expMmentales sur les
proprlMs et les fonctions du systime neroeux dans les animaux oerBecherches

Ubres, 1824, says nothing about theifel. It is an invaluable

canals, but gives, esp, 3^-42, Flour-

source although not always accurateens’ account of the functions of theto

as to details. See alsoJ.

G, Ousser

cerebellum,

which supplements L.

NOTES
Rolnndo's work in 1809,(On Ro-lando, SCO E. G. Boring, Ilistoiy ofExperimental Psi/o/iologg, 1929, 59 f.,
74. ) Flonrens’

experiment is in

first

his Exp6ricncce sur le sijstdme ner-

1825,' 441,,

veux,

(or

iihstracted

1842, 4521.

infra.,

ctt.

[n.v.],

wliicli

reprinted?]

is

op.

in

The hill ac-

Kopfesentstchend StBrungen der
Muskolinuervation and dor Vcrstellung vom Verhalten hn Raume, Arefi.
1871, 716-770. A.
Lowenberg's evidence that section
Phxjsiol Leipzig,

of tire canals

excitatory in func-

istion is in his Ueber dio nach Duroh-schneidung

Bogengiingedercounts ol the experimenls performed

Ohrlabyrintlies aultretenden

1828 are Expdrienccs sur lescanaux somi-oirculaires de Toreillenngsbtorungen, Arch. Augen.
enheiH., 3 (1), 1873, 1-12,

hr

dans

oiseaux (pigeons

les

Mem,

birds),

Acad.

and other

Sci,

Paris,

9,

1830, 455-460 (reprinted in op. dt.
infra,,

1842, 454-468); Exp&iencos

canaux semi-^culaires deroreillc dans les mammlferes (rabbits), Ibid,, 487-477 (reprinted in
op. cit, infra,, 1842, 469-482). Thus
one finds the full account in the 2
sur

les

ed.,

op,

cit,

supraiRechercim ex-

jidrlmmialas sur les propriStSs et les
foncllons

du syslime neiveux, etc.,

For E. Mach's

desBewegOhr-

coniributions, see

his Fhysikalische Versuche fiber den

Gleichgewlchtssinn
SItxungsber.

math.- natuiw.

124-140; 69

Cl.,

(2),

Menschen,

des

Akad.

Wise,

Wien,

08

1873,

(

8),

121-135;

1874,

Gmndltman der Lehre von den Betoegungsempifmdimgen (one of theclassics of experimental psychology
inthe nineteenth

century),esp. 22-54, 07-124. Later

18fS,

Mach re-viewed the whole problem and de-Ms apparatus for the visual

2 ad., 1842, 438-501,

scribed

There wore oiliet early papers on
oqtiilihrallon but no important conIrikuiion. Ono ol the most complete,
tollowing Purklnje and not mentioning Flonrens, was M. II. Rombere,
Znt Lchro von dem Selwlndof,

obsorvalion of small animals during

Wag-rotation In his Analyse
dor Empfindungen, 5 ed., 1907, orEng. trans., 1014, chap. 7,
Brouer's papers are Ueber dio
J.
Bogengiinge des Labyrinths, Allg,
Wien, med, Zeitung, 18, 1873, 598,
600 (two short notes); Ueber die
Function der Bogengiiirgc des Ohrlabyrinthes, Med. larni. Wien, 1874,

Handwdrterbuch der ffti/siowgie. IV, 1853, 422 f. C. E. Brown-

72-124, esp. 120-124; Beitrllge zur
Lehre vom statischen Shine ( Gleich-

Wocliemolir, gas,liellk,,

2,

1833,

1057-1070.
C.

Hoi'less

reported

experiments in

Flonrens'

vetilylng

H.

ner's

Soquarddescribed his experiments

witli frogs in his

Experimental Re-

searches Applied to Physiology

Pathology,

1853,

18-23,

rmd

09 f.

J.

their rapid

gewiclrtorgan, Vestibularapparat desOhrlabyrinths)(he hadtodefinehis new term, the static sense, in his
title), ibid.,

1875, 87-156,

vertigo witli the extrusion of the en-

A. Crum Brown’s contributions are
in On the sense of rotation and thea human subject inanatomy and physiobgy of the semi-

and semicircular
canals extruded during life. Tram,path, Soc. London, 17, 1866, 272 f.

circular canals of the internal eat,

Toynbee reported thetire inner ear of

cessationofVestibule, cochlea

Golte's most important paper
Ueber die physlobglsohe Bedeutung der Bogengiinge des Ohrla^-F.

isrinths,Arch. ges. Physiol.,3,

18'?0,

172-192, csp. 187-190. E, Hilzig^spaper on mectrical stimulation is

Uwor

die

beim Golvanisiren

desAnat. Physiol, 8, 1874, 327-331;

Cyon’s researches on the ear, Noture, 18, 1878, 683-635, 657-659.
The other two important theorists
of

tlie

1870's,both

men who per-fected the surgical method of stimulatingor

elhnkating thecanals,are E. Cyon, Ueber die Function derhabfoirkelformlgen Caniile, Arch, ges,

ORGANIC SENSIBILITY

570
Fhyaiol,

300-327;

Re1873.
chetches expMmentales mr les [onc8,

tloiw des Ctttiaux semi-oirmhites etInternal SensibilityFor

sur leur rdle dans les formations de

lack

early

tire

and

infonnation

about internalof infonnation

la notion de

Vespace, 1878, esp. 38and A. Bottcher, Ueber die
Duichscbneidung der Bogengiinge

sensibihty,

44;

menta physiologiae corporis humani,V, 1763, Bk, 17, 529-827 (Sensus

des Gehorlabyiinths und die siohdaran knilpfenden Hypotbesen, Arch.

Intemi); also Primae lineae physiu-

OhrenheiUc., 9. 1874, 1-71.

trans.,For the early history of the belief
that the canals function for hearing,see pp. 401-403; for Jaensch’s belief that the vestibule functions fornoise, see p. 364.

On dizziness in deaf mutes, see
W. James, The sense of dizziness indeaf-mutes, Amer. J. Otol, 4, 1882,
23B-2S4; A. Kreidl, Beilrage zur
Fhysiologie

desOlulabyrinlbs

auf

see

1747,

logiae,A.

Haller,v.

Elc-

but in Eng.

[n.v.],

1760, chap.
18, 290-311(Haller actually anticipated C. G.

Lange's theory of emotion on p.
217 f.); De partibus corporis humani senslbiubns et irritabilibus.
Comment. Soc. rag. Sci. Gottingensls{CeseUsch.

Gottingen),

Wiss,

2,

1752, 114-158; James Mill, Anolysis of the Human Mind, 1829, cbm.

Handbiich der

Miiller,

1, sect. 6; J.

Physiologic des Menschen,

Bk.

V,

Grund von Versuehen an Taubstummen. Arch. ges. Physiol, 51, 1891,
119-150; J. PoUalr, Ueber die "galvanlschen Schwindel” bei Taubstummen und seine Beziehung zur

1338,

Function des Ohrlabyrintbes iUd,,

the64, 1893, 188-208,

Hamilton, Lectures on Logic andMetaphysics, 1859, I, Iccl. 27, esp,

On the effects of anesthetizing Iho

scot.

5 (in Eng. irons., 1324-1332); E. H. Weber,

Das Ccmcin-

Wagner’s

Ilandworlar-

gcfiihl,R.

buck der Physiologic, 111, ii, 1846,
562-570; A. Bain, The Senses andIntellect,

sulla anestcsia del canal! semicircolari

377; W. Wundt, Grtmdxilge
Psychologie,
physiologischendel! orecohio. Arch. Sci. med. To-

1910,

see

canals,G.

Gagllo,Experienze

On the use
induce vertigo, see

1899, 41-64.

rino, 23,of pressure

toG. Alexander, Weitere Studien fiberdem durch Kompression und Aspiratian

auslfisbaren

labyiinthiiren

Nystagmus, Monatschr. OnrenheUk.,
44. 1910, 941-944.

On

vertieinous

habituation,

24-29,

W.

132-145;1866,

47-51;

G,

der
II,

Ladd

T,

and R. S, Woodworth, Elements ofPhysiological Psycholom, 1911, 350(only nine lines, which include!
can be done at present
toward a physiological explanation"Littleof these sensations[hunger,nausea,well-being,

suffocation,

thirst,
ill-

see

ness]

excepttocall

C, B. GrifBm, The organic effects of

theirexistence");

L.

Luciani,Hu-repeated bodily rotation, I. esp. Psy-man

Physiology,IV,trans.

1914,

chol,

3,

1920, 15-46.

On the evi-

dence for central compensation in
addition to peripheral mechanicalattentionto

57-88 (the most extensive accountin thisadaptation, see R. Dodge, Habitua-

list

except for Bain's).

Visceral Sensibilitytion to rotation, ibid., 6, 1023, 1-36.

On the introspective nature of dizziness and the absence of a uniqueFor

historicalsensibility, see A.

notes

on

visceral

Neumann. Ueber

An experimental

die Sensibilitfit der inneren Organe,study of dizziness, {bid., 3, 1920, 89-

ZM. Grentgeb. Med. Clur., 13, 1910,

126, In short, the role of the brain in-

401-415, 449-460, 481-501, 629538, 573-593, 617-628, 850-676,
696-708 (biliography of 09 titles);quale, see Griffith,creases, but the role of Introspection

decreases.

NOTES
J.

F.

Mllelioll,

SeasMity

o{

571

the

Hungerperitoneum and abdominal viscera,

On the history of theories of hun-

Amer, med, Assnc,, ff7, Iflll,
709-712; also Memnann (1007),ger,

Heilz, Boring ,(pp. 2-5), opp. dtt.

C. Ricliet’s Dlctionnaire de physiolo-

Infra,

gie, VI. 1903, 1-29, esp.

I.

Tbs' following are the roferenoea
indicated in the text: E. H. Weber,

Wagner’s Ilandwdrterbuch der
Physiobgle, III, il, 1846, 497 f,
514 f„ 562-568; J. Hilton. On the
Influence of Mechanical and Fhysiohgical Rest and the Diagnostic
Value of Pain, 1863, esp. 63-82; K.
G. Lennander, Ueber die Sensibibtiit der Bauchhohle und liber lokale

in R,

und

nllgemeine

Aniistheaiebei

Brudi- und Bauchopemtlonen, Zbi.
Chlr., 28, 1901, 209-223; Abdominal pain, J.

Amer. med, Assoc., 49,

E.

see

B. Cannon,

Bordler,

La

faim,

in

14^19; W.

A consideration of thenature of hunger, in The Harvey
Lectures: 1911-1911, 1912, 130152; Bodily Changes in Pain, Hun-

Fear and Rage, 2

ger,

ed..

1929,

268-298; Hunger and thirst, in
Handbook of General Experimental
Psychology,247-263, esp.
1934,
247-254; A. J. Carlson, The Controlof Hunger in Health and Disease,
1918, esp. 16-29 (history), 30-83

803-316(facts),(bibbogtaphy of

284 titles).
For tire theories that hunger is aW. H. R.

general sensation or of central ori-

Rivers andSherren, The afferentJ.

gin or both, see F. Magendie, Prdcls

new aspect,l(ementi>ire de physiologle, H, 1817,

1905, 99-115, osp. 112-24-31 (or Eng. Irons., 196, [n.v.]);C. E. SMillot, Du nerf pneumo-

1907, 838-840; H. Head,

nervous system from a
Bnrin, 28.

115; L. Knst andS.

J.

Mollzor,On

the sonsibillty of the abdominal or-

gastrlquegans and the Inlluencc of injections[mv.];of cocaine

1906,

upon it, Med.

1017-1019;

Frage derC.

Rec,, 70,

Ritter,Ztir

Sensibibliit

der Batioh-organo, Zbl. Chlr., 35,

1908, 609-

615; E,

Meumann, Zur Frago det

Sensibilitiit

dot

inneren<>gane.

etsesfonctlons,1829,

Tiedemann, Physiologle
des Menschen, 1630, I, 233-2OT;
W. Buscli, Beitrag zur Physiobgio
dor Vordauungsorgane, Arch, paihol
Anat. Plujslol, 14. 1858, 140-186;
F. A. Longet, Trolti de physiologle,
2 ed., 1861, I, 18-31 (1 ed.. 1852,
F.

La

Arch. ges. Fsijchol., 9, 1907, 28-62;[n,v.]);

Weiteres zur Frage der Sonsibilitat

physio-p^chologique. Bull Soa, Anthropol Lyon, 16, 1897, 409-455,

der inneren Oigane und det Bedeu-

lung der Organempfindungon, ibid.,
14, 1909, 279-310; 16, 1909, 228235; E. Becher, Ueber die Sensibilitiit
der inneren Organe, Z. Psychol, 49,

esp.

J.

Roux,

faim:

4lude

415-439; E. Bardier, op.

cit.,

1903; L. R. Muller, Ueber die Huugerempfindung, Dtsch, med, Wochenschr., 41, 1915, 1207-1801,

1908, 341-373; Einige Bemerkung-For the theories that hunger is aen iiber die Sensibilitat der inneren
Organe, Arch. ges. Psychol, 15, 1909,

specific sensation which origlmtes in

856-379; A. F. Hertz, F. Cook andE. C. Schlesbiger, The sensibility oftire stomach and intestines in man, J,
Phi/sioL, 37, 1908, 481-490; Hertz,

lineae pkydobgfae, 1747, sect. 638,

The Sensibility of the AUmentary Caned, 1911; E, G. Boring, The sensa-

rishummi, VI, 1764, Bk.

2,

164-187,etsids);

tions of the alimentary canal, Amer. J,

Psychol, 26, 1915, 1-57; The thermal sensitivity of die stomach. Ibid,,26, 1915, 485-494.

the stomach, see A. v, Haller, Prbnae[n.v.], Eng. trans.,

1766 or the 1779

reprint, 3OT; or Eng. trans., 1786, II,81 f.; Elementa pm/siologiae corpo-

oarporls

S.

T.

19, sect,181-187 (Fames
Soemmerrlng, De

humanl fabrics, 1801, VI,

236-238; E. Darwin, Zoanomla,
1801, HI, 198 (not in the earber

ORGANIC SENSIBILITY

572

W. Beaumont,eds.)iObsemtUm

andEsperiinents

on

the

Gastric

Juice and the Physiology of Digestion, 1833 (lacsimile ed.,1929), 53-

00; J. Miiller, Handbuch dot Physiologie des Menschen, 1, 1838, Bk,
2, sect. 4,

chap. 1 (p. 485 in Eng.

bans,,

ed.;1

Mlf., German,pp.

3 ed.); E. H. Weber, in R. Waaer’s
Jiandwikterbuch der Physi^gie,m,

1846, 580 f.

ii,

On the discovery of the hunger
conbactions, see

W, Nicolai, Veber
Hungerg^hfs,

die Bntstehung des

W. N.

Le

Boldbcfi,

1892,[n.v.l;travai]pdriodique de I'appareil di-gestifendehors

de

la

Arch.

Sei.

biol,

11.

1905,

osp.

25-32, 50-^6;

digestion.

1-157,

W. B. Cannon

and C. W. Lieb, The receptive relarcnUon of the stomaeli, Amer. J,
Physiol, 27. 1910, p, jiii; Cannon,
The Mechanical Factors of Digestion,

1911 (wliioh leads up to theimportant discovery);Cannon and

A. L, Washburn, An explanation ofhunger, Amer. J. Physiol, 29. 1912,

44W54; Cannon, opp, da.; F. T.
Rogers and C, L. Martin, X-ray observations

on hinmer contractlnna inanimal psychology, see M. F.
Washburn, The Animal Mind, 1 ed.,1908, 71 f., 81 f., 211-213; 2 ed..
1917, 253-255; 3 ed., 1920, 325828; 4 ed., 1938, 387-397; ]. B.
Watson. Behacior: an introduction
to Comparative Psychology,'’Wli,
57-61; £. C. Tolman, Purposive Behavior in Animals and Men, 1932,271-289, esp. 278-280; Tolman and
C. H. llonzik. Degrees of hunger,
reward and non-reward, and mazelearning in rats, Univ, Calif. Publ
Psvchol, 4, 1930, 241-256; M, H.
Elliott, The effect of hunger onvariability of performance, Amer. 1.
ofPsychol, 40, 1934, 107-112; B. F.
Skinner, The Behavior of Organisms,
1938, 341-351, 368-371.

ThirstOn thiret and the history of its
soe W. B. Cannon,
Changes in Pain, Hunger,
Fear and Rage, 2 cd., 1920, 290investigation,

Bodily333; Handbook of General Experlmental Psijcholoffj, 1934, 245-263,
esm 254-263.

For A.

Haller’sv.

man, Amer. 1. ^i/siol., 70, 1926,349-^53; A. J. Carlson, The character and movements of tire empty
stomach in man, ibid., 31, 1912,
151-108; The relation between theconbactions of the empty stomachsion,

and the sensation of hunger, ibid.,81, 1913, 175-192; also nine more

esp. 179-181.

articlesbyCarlsonin

ibid.,

vols.

31-34, 1913-14; also Carlson, op.
cit.,

On the relation of hunger contractionstoactivity

and thus todrive, see T. Wada, An experimental

study of hrmger in
activliy,logiac,[n.v.],

Arch.

its

Psycholrelation to

N.T.,

8,

1922, no. 57; C, F. Richter, Ai^aldisous-1747, chap. 20, soot, 039,
but p. 337 f. In Eng, bans.,

1766 (or the 1779

icprinl);Ele-menttt phy.riologfaa coqjoris himanl,VI, 1764, Bk, 19, sect. 2, 164-187,

On how

thbsl

depends on thelack of sulBcient water in the body,
see

tlie

citation(apparenily

oral communication)

1918.

early

see bis Friniac Ihteae physlo-

fromof the experi-ments of both G, Dupuytrennand P.
Orfila by F. RulUer, Dlctlonnaire dessciences mddicales, 51, 1921, 448490, esp. 408-472; Claude Bernard,
Lepons sur la phjsiologie expMmerrtale appUquee i mddlctne, II,behavior and internal drives, Ouoft.

1856, 26-169, esp. 50-52; G. Lepidi-

Hep, Biol., 2, 1927, 807-343, esp.
307-320.

Chloti and S. Fubini, Influenza della

As Indicating the chanceuse of the word hunger
sation to drive,

pencllazioni

faringeedicloridratn

in thedi cocaina nella sensazione della setemrm sen-e nella secrezione deUa saliva para-

under tire influence

tidea

umana, Giom. Accad, Med.

NOTES
Torino,L

A inclhoil for unilorm

while panting, Aid,, 102, 1932, 336-

48,

Giugei'son,

9051.!

1885,

M.

sUmuIiitiuu of tlic salivary glands inthe uuanusthetiMd dog by exposure

warm enfironment, witli some

to a

573

glands on the water intake of dogs

observations

onquantitativetlie343, which answers Montgomery,On thirst as a general (or brain)sensation, seeJ.

M. Schiff, Lefomde la Age^on,

sur la physiologicchanges in salivary flow during de-1867, 1, 29-42, esp. 41 f.; A. Mayer,

Amer. 1. P/iysioI., 97,
1931, 107-116; Conditions affecting
tile daily water intake of dogs as

Variations de la tension

hydiation,

registered continuously by a potom-

On the relief of thirst by cocaine
anesthesia of the throat, see Lepidi-

and Fuhini, op.

Chioticit; A.

Va-

Sur la gen^se des sensations
de fnim et de soif. Arch. itcl. Biol.,53, 1910, 94-104, esp. 100-102.

lenti,

On appetitive lliirst wilhout theoral scusaLian, see, for the mild de-

E.

gree,

G.

Boring,Processesre-ferred to die alimentary and urinary
tracts:liquldes, C, R, Soo. Biol, 52, 1900,

158-155; Begulalion de la tension

osmotique du sang par actions vaso-

102, 1032, 344-349.

eier, ibid.,

osmodquedu sang chez lea animnux prives demotrices.

du

sang,

dorff,

888-392;

ibid,,-

621 f,; H. Wetten-

du sang sous

ModifleadonsdeI'influence

Tnroatrx

laprivaUon

Ldboratorie

Bruxelles,

4,

Centresk pression osmotique

1901,

d’eau,

SolvayInst.

353-484,esp.

401-419, which refutes Mayer; L.
R. Muller, Die Lebensneiven, 2 ed,
1924, 530-537, [1ed..

n.v.].

a qualitative analysis, Psy-

chol Reo., 22, 1915, 806^31, csp.
807-3Ili for the extreme depee, A.
L. Winsor, The cfleot of cmliydi'a-on parotid secretions, Amer. 7.
1930, 602-007.

lion

ibid.,

rdgulateurs de

Psijobol, 42.

On the relation of salivation
thirst. SCO

toF, Bidder and C. Schmidt,

Organic Patterns
For the chief relorenccs on organic
patterns and tire altitudes related
to bodily needs, see E.

Meumann,

Woiteres zur Frnge der

Sensfhilittit

der inneren Orgaue und der Bodeu-

md

Stoffweclwal,

1852, 1-28, csp. St.

E. V. Zebrow-ges,

Psychol,

Ziu Frago der sckreloriscben
Funktinn dor Forotis helm Monsclion,
Arch. ges. Physiol, 110, 1905, 105-esp.

29^298; A. J. Carlson and L.

H,

Braalladt,

VordumnpfHIte

I

ski,

173;

I.

P. Pavlov,

Digestive Glands,
or. better,

The Work of the1ed.,1902, 68,

2 ed.. 1910, 70, 82; W.

B. Cannon,

The physiologiool basis

tung der Organompflndungen, Arch.
14,

1909,

279-310,On the sensibility of

the gastric mucosa, Amer. J. Physiol,
36.

1915,

152-170, esp,

162-165;

The Control of Hunger in
Health and Disease, 1916, 98-118;

Carlson,London,E. G. Boring, Processes referred tothe alimentary and rrrfnary tracts; a0OB, 1918, 283-301 (the importantqualitative analysis, Psychol Rev., 22,

of

Froc.

thirst,article);roy.

also loc.

Gregersen,

op.

cit.,

cit.,

Montgomery, The

Soe.

1929; M.

1931;

M.

I.

F.

role of the sali-vary glands In the thirst mechanism,

Amer, ]. Physiol, 06, 1931, 221227, which is against Cannon's theory; Gregersen and Cannon, The
effect of extirpation of the salivary

1915, 308-331! Boring and A. Luce,

The psychological basis of appetite,
Amer. J. Psychol, 28, lOW, 443453! C. R. Griffith, An experimental
study of dizziness, /, exp, Psychol,8,

1920, 89-125; E. B. Tilchener,

A Text-Book of Psychology, 1910,
191-193.

Chapter 15

THE PERCEPTION OF TIME AND MOVEMENTThe physiologists have always classified sensations in respect of the five sense-organs and their related neural sys-tems—sight, hearing, smell, taste, touch. Wundt started

the fashion in psychology of classification in respect of sensory di-mensions—qudity,intensity, space and time. He himself regarded

quality and intensity as the two attributes of sensation, whereas

space and time represented for him modes of complex perceptualorganization. Thus the main chapter headings for about half ofexperimental psychology were sensory quality (the five .senses),sensory intensity (psydiophysics and the Wober-Fechnor functions), space perception (the organization of perceived space on

the basis of various sensory data),

and temporal perception (asimple analogue of space perception). Modern psychology, however, has reverted to the physiologists’ schema because

it is

no

longer possible to keep the problems of quality, intensity andspace separate. Hue, brightness and saturation, for instance, turnout to be interdependent variables, each differently related tothe same dimensions of the stimulus. Hue and brightness ai'e also
related to visual size; pitch and loudness are not independent of

tonal volume. Phenomenal intensity, moreover, nearly always ap-

pears as the intensity of a quality. Weber found space (the Ortsinn) fundamental to the understanding of the cutaneous mechanism. Recently auditory theory has
intensity (loudness)

had to become adequate toand space (localization) as well as quality(pitch). In short, modem psychology, being physiologically ori-

ented, has to put all the sensory attributes together and to giveup WundFs distinction between sensation (quality and intensity)and perception (space and time). This book has, therefore, dealt
separately with the senses, rather than with the attributes of
sensation.

„

There are, however, many problems of the inten-elation of thesenses; the facilitation or inhibition of one sensory impression by674

PERCEPTION OF TIME

srs

anoRier from a different modality, the comparison of two extensions or intensities or biightnesses that occur in different modalities, the cooperation of sense-data in attention, memory, imagina-

tion and thought. Tliese topics are omitted here. Attributive com-

parison across the modalities has already been considered (p. 27),and many of the other topics belong in a book on the history of
the Tii^er’ or ‘complex’ mental processes.

Two general sensory problems, nevertheless, remain, each of
too great historical importance to permit of omission. The oneis the perception of time, the ZeUsinn; the other, the perception of

movement. Although most of the temporal intervals investigatedhave been heard, and most of the movements seen, both perceptions have been considered to be, in their essentials, independentof the properties of the particular organs of sense and thus almost

wholly dependent upon the action of tire central nervous system.

Whatever their destinies, they are still general sensory problems,
and to them we address ourselves in the present chapter.

Perception of Time
Into philosophers’ many theories of temporal perception

weneed not enter in detail. Nidiols in 1891 considered more than
three score of their opinions, extending his survey from Plato toWilliam James. He made it dear that the early philosophers had

Time was taken by them for granted,
however—the school that made philosophy

little of importance to say.

British empiridsra,

psychological—had to meet the problem of temporal perception.

They said ( Hobbes in 1655, Locke in 1690, Berkeley in 1710, Humein 1739) that the idea of time arises from the succession of ideas,

The mind has a temporal dimension which gets to be known after
the manner in whidi its other properties are known. There was,
howeVer, an error in this view. A succession of ideas is not equivalent toan idea of succession. Reid (1785) and Thomas Brown(1820) pointed out that the perception of time must, tiierefore,

depend upon memory, thatearly terms of a series must be

held over if they are to unite with the later terms to form the composite of a perceived succession. James Mill ( 1829 ) made the same
point, and William James (1890)

observed that “our conscious-

ness never shrinks to the dimensions of a glow-worm spark,’’ “illu-

minating the point it immediately covered, but leaving all beyond

570

PERCEFnON OF TIME AND MOVEMENT

in total darkness.” “The knowledge of some other part of the stream[of consciousness], past or future, near or remote, is always mixed
in with our knowledge of the present thing.” Thus

Wundt (1874)

also came to recognize a temporal range ol consciousness, meas-

ured by the duration of the rhythm that remains recognizable as aunique pattern without being counted or reflected upon.
This difficulty about the introspection of a duration arose because consciousness was conceived to be ‘immediately given,’ tliat
is to say, introspection

was not believed to be a process that takes

time; to have a perception is in itself to know that one has it—that

was accepted doctrine. But how then can a duration that takes
time be immediately known, since the duration, not being instantaneous, is itseK not all immediate? At what time in a time does one

perceive that time? That was the problem and there have been
three solutions for it.

The first is the solution of the conscious present. E. R. Clay,
writing in 1882, noted that tlie present is specious. It is merely apoint without duration, where the past meets the future, and lime
consists consequently “of three nononlltios—the past, which does

not exist, the future, which does not exist, and their contorminus.
the present,” which, having no duration, also docs not exist. Yet
die “sensible present,” as James called it, oiling Clay, has duration, specious thougli that duration be.

tain durationis

Wundt was right. A cer-held together as a conscious present, whichisknown immediately as soon as it is complete in actuality or in
anticipation. This solution is satisfactory as long ns one does notpress too vigorously for refinement in the dating of events.

The second solution lay in the denial of the validity of such
temporal analysis. Mach originated this view, when in 1880 heregarded time as a sensation, and when later, in his Analyse derEmpfindmgen (1886), he discussed both space and time as if
they were sensations. In this innovation he was indirectly ’aided
by Kant’s authority which had established the analogy between
thne and space as a priori intuitions, with the result that whatever

could be said of space might be presumed to be applicable totime too, A succession, when it is perceived as a duration, is not astring of sensation-beads any more than a perceived line is a rowof perceptions. ^That was essentially Mach’s doctrine, but

it isdoubtful if it ever became dear until modern Gestalt psychology
effectively did away with the analytical attitude toward the prob-

TIME-^ENSE

STY

lems of both extension and duration. For Gestalt psychology an
extensionisan extension, not a row of sensations. Similarly an

intensity is an intensity, not a sinn of quanta, and a duration is aduration, not a series of events. Extensity, intensity and protensity

are al\ given just as directly as quality. This was also Titchener’s
final view(1915) after he had turned from sensation to attributefor his ultimate

datum.

In modem positivistic psychology this problem has disappeared,

and that is the third solution. The substitution of differential response for the old-fashioned dated esdstential consciousness doesaway with immediate experience. Any conscious event, for the
positivist, is a relationship that oeemrs in time, a form of discrim-

ination. Dm'ations, although

not instantaneous, can be discrim-

inated, a long from a short, and as such are conscious. The processof discrimination can also be dated as accurately as any otlrer

temporal process; yet from Ibis point of view dating is no longer
very important.

The Time-Sense
In 1857 Czermnk suggested that Uiero is for duration a “general
sense,” a Zallslm analogous to Webor’s Raumsim for space. He

made his point by laying down a program for the investigationof the time-sense, a program which included the determination of

the sliortest perceivable intoi'vals in eacli of the other senses and of
the perceivable rates of visual and tactual movement. He did notexperiment; ho only set the general problem.

Experiments were, however, easy to get under way in thosedays when Feohner’s new psychophysics provided so many new

problems in sensory physiology; and it was Mach who undertook
the first experimental work, starting in 1860 and publishing in
1865. His particular project was to test the application of Weber’s

law to’time. He had, of course, to determine the j.n.d. of duration
for intervals of different lengths,

and he used intervals ranging—thatfrom 0.016 to 8.0 seconds, filling them with beatsisto say,the observer heard first one series of beats and then another, being

required to say whether the second series was longer or shorter

than the first or of the same duration. Mach got the beats for the
short intervals from a metronome, for tlie longer intervals from a
special apparatus, and for the longest by striking an anvil by handwith a hammer while he noted the time on a watch. He found

578

PERCEPTION OF TIME AND MOVEMENT

the greatest sensitivity for an interval of 0.375 seconds, where theWeber fraction proved to be about five per cent. Since the fraction
was not constant but greater for both shorter and longer intervals,
he concluded that Weber’s law does not apply to the perception'of tinie.

After Mach came Vierordt and lie indifference point. The firstpublication in this new work actually anticipated Mach’s. It was apaper in 1864 by Boring, one of Vierordt’s pupils. Boring usedempty intervals, each of them bounded by two beats of a metronome, and the method of right and wrong cases, which Vierordt

had invented in 1852. Be employed intervals ranging from 0.8 to
1.4 seconds, finding that the constant cnor was least in the interval
between 0.36 and 0.45 seconds, that is to say, at about 0,4 seconds.

The shorter times, as he put it, were estimated as too long and thelonger times as too short. Tie indifference point is the duration forwhich there is no constant error, the point where the positive errors—nschange to negative. In this particular experiment it is not

Woodrow pointed out much later—quite correct to say that tire

short times are judged too long and the long limes loo short, be-cause Bdring was judging the relation between two successive
durations. Actually he was determining the psychophysical limeerror for the judgment of successive times.

He found that, forshort intervals, the second duration, seeming shorter,

must bephysically longer than the first if the two are to appear equal, and,conversely for the long intervals, the second, seeming longer, must

be shorter than the first if the two are to appear equal. Thus thefirst short interval is ‘overestimated’ as measured by the second,although it is just as true that the second is underestimated’ asmeasured by the first. Boring’s result was, however, interpreted
in this way because such a statement is consistent with the find-ings for the reproduction of intervals, a method which came next.

In 1868 Vierordt himself published his Der Zeitsim, the classic
in this field. He used Boring’s apparatus and method, but he alsostudied the reproduction of durations. For this purpose he ar-ranged a metal lever with a writing point that traced a line on a

kymograph. The experimenter gave first the standard interval in
auditory terms by striking the lever twice with a brass rod, thus

presenting the^ interval and also recording its duration on the

kymogra^. ’Then the subject duplicated the interval, as well as
he could, by depressing the lever twice so as to mark off a second

TEMPORAL INDIFFERENCE POINT

S79

interval on the record. Vierordt also used other variants of method,

but these two procedures were the most important.
Vierordt found that the place of the indifference point varies

from persoo fb person, from time to time, and from the ear to theeye, Its total range was from 1.4 to S.5 seconds, but the shorter

times are most often cited, because they come closer to threefourths of a second, a value which was later accepted as correct.

In respect of Weber’s law, Vierordt discovered that the Weber
fraction varies continuously ftom about 18 per cent with a positiveFid. 90. Positive and Negative

Constant Eheoes in the Judgment of
Dubatiok: Kdu-eut (1882)

The indifferonco point ( zero constant enor) lies at 0.755 sec., with positiveenors (“overestimation") for shorter durations and negative {"underThe results are smoothed in accordance with aestimation”) for longer.

mathematical function. Adapted from KoUert

error for durations under 0.5 seconds, through a minimum of about

3 per cent with little enor between 1,0 and 1.5 seconds, up toa maximum of about 41 per cent in the region of 5 to 8 seconds.
This result was taken as confirming Mach’s conclusion that Weber’s

law does not hold for time.
After Wundt’s new laboratory got under way in 1879, the timesense was one of the subjects investigated there. There were im-portant papers in Wundt’s VMosophische Studien by Kollert,
Estel and Mehner, all of which Fechner criticized. One point wasthat Wundt wanted the method of least perceptible differencesused instead of Vierordt’s method of right and wrong cases.

For this reason Kollert introduced the method of least perceptible diffei'enoes in 1882.

He had two metronomes, one for thePERCEPTION OF TIME AND MOVEMENT

580

standard interval, and the other for die compai'ison.

Ho usedstandards from 0.4 to 1.8 seconds, His intervals were empty, being

each die duration between two beats of a metronome. After excluding certain anomalous results, he found an indilFerence point
at 0.755 seconds. Fig.

90 shows the way in which his erfors ol‘overestimation’ and ‘undeiestimation ran.

Then Estel in 1884 with a new apparatus elaborated and con-

Ho got die indifference point at 0.75

finned Kollert’s findings.

seconds, but he also interpreted his findings as showing that theerror of estimation is reduced at even multiples of 0.75 seconds—at1.50, 2.25, 3.00,

.

.

.

seconds. His curve looks like Kollert’sin Fig. 90 with a periodic curve superimposed upon it.

He arguedthat a law of conti'ast is operating, that a short fli'st standard interval makes the second comparison intervals longer by contrast,

and conversely. This relationship would seem, however, to be

more one of assimilation than contrast. A short first interval shouldmake the second seem short by assimilation, so that the second
has to be lengthened physically in order to seem equal to the first.

In 1885 Mehner repeated Estel’s work, found an indifference
point at 0,71 seconds, and interpreted his results as indicating lliat

the error is minimal at odd multiples of 0,71 and maximal at evenmultiples. Glass, however, criticized in 1887 botli Eslcl’s conclusions and Mehner’s, failing to confirm either kind of periodicity

and showing that the evidence for periodicity was not significant as against the great variability of tlic data. L. T. Stevens in1886 also failed to find periodicity and got great variability of
the indifference point, although his averagewasclose to Uie

others (0.71 sec.).

What these men in Wundt’s laboratory were hoping to find wasa psychological unit of time. May there not be, they wondered,some absolute duration, near 0.7 seconds, which is always available to the mind as a standard, which is most accurately judged

both in respect of estimation, being neither overestimated nor
underestimated, and in respect of variability, being the point

where the Weber fraction is least? James later regarded this interval as a measm'c of the sensible present, and neatly everyone took
it to bethe right interval for the warning signal before maximal

attention is needed for a stimulation or a reaction. The discovery

of a physiologically absolute duration was a reasonable aspirationin the days of the new psychology when the mental chronometry

ESTIMATES OF TIMES

S81

of tlic reaction times seemed also to be providing natural durations
for appeicoption, discrimination, cognition and ohoicc. Nevertheless, thosemen were wrong. The indilferente point is variable andhas no regulaj- periodicity.

Mitasterberg was nearer' the truth in 1889. Ho said that it was
futile to look for fixed mental units of duration, that what

we mustseek is the physiological measm'es of the time-sense. Thus he de-

Fic

91 ApFARAros fob 'nia Tims-Scnse:.

A kymogiapb (right)

Meumann ( 1894)

on whleti ttie
projecting Unger trips tire electrical contacts to opeiate the stimuli ( sounders, lights ) that limit

drives tire graduated disk

(left),

die judged Intervals.

scribed the manner in which the perception of duration depends

upon the perception of the sensory tensions (Spannungsempfindungen) that fill the conscious interval, ihe tensions of ie rhythmof breathing and of many other strains beside. Mimsterberg wasthus one of the first to emphasize the importance of klnesthesis in
the conscious life(cf.

pp. 533 f.).

After this came Meumann’s extensive study of the time-sense(1892-1896). His papers have always been regarded as the sec-

ond classic in this field alter Vierordt, but the fact is that he contributed no generalization as basic as Vierordt’s on the indiEer-

ence point. He invented an important apparatus (Fig. 91), a diskthat can be geared to the Ludwig-Baltzer kymo^aph (then themost accurately controlled ‘dock’) in such a way as to make elec-

582

PERCEPTION OF TIME AND MOVEMENT

trical contacts forany desired interval according as tlie contact

points are adjusted on

tlio disk.

He studied the relation of tlie

estimates of times to the intensities of the limiting sounds, torhythm, to the difierence between sound and light, and to thedifference between filled and empty intervals.

’^

We may omit consideration of the numerous investigations of
the time-sense in the present century and content ourselves withnoting the final outcome in

Woodrow’s experiments. Woodrow

showed conclusively (1930) that there is nothing absolute about

The individual differences are too large.
Some of his subjects overestimated almost all the intervals that hethe indifference point.

used (from 0.2 to 30. seconds); others underestimated them. On
the average, it is true that an indifference point comes out at about
0.6 seconds with his data (1934); there may be some underlying

tendency of the sort that Vierordt asserted. One factor that determines the estimates—so Woodrow found— is attitude, a para-

meter that had not been controlled in the early cxpeiiments, He
set up in 1933 two instructions. In one, tlie “auditory instruction,”

the subject was to keep his attention solely on lire sound, to forget about his reacting finger', to remain unanalytical. In the other,die "strain instruction,” die subject was to attend carefully to Iho
interval between the sounds and to his reacting finger. The audi-

tory instruction gave

him almost entirely underestimation, thestrain instruction almost entirely overestimation. It was ns if thesecond instruction had filled the interval with strain and expanded
it in perception,in the way that filled visual extents seem longer

than empty. Thus the finding of an indifference point may mean

merely that the attitude of observation tends to change with thelength of the duration judged.

While it is disappointing to realize that the hopes of Vierordt

and the Wundtians were unfulfilled, it is no news to remark thatthe discriminating organism seldom operates simply and 'would

hardly carry around with it a temporal unit as great as threefourths of a second. If the indifference point had been of the orderof a physiological constant like the refractory period of nervous
tissue, that would have been a different matter.

RANGE OF CONSCIOUSNESS IN RHYTHM

583

RhythmRhythm has played a larger role in psychology than in experimentation, principally because it is involved in the problem of
esthetic form, although also somewhat because there is an atmos-

phere of mystery about natural physiological rhythms. Of the 714
items in Ruckmioh’s bibliograpliy of rhythm we need to mention
less than a score here.

There is a story tliat G. Stanley Hall, entrepreneur and spellbinder among psychologists, travelled about the United States,
shortly after Bolton had finished his experiments onrhythm at

Clark in 1894, lecturing to Sigma Xi audiences on rhythm and fascinating diem with the magic of his tongue. When one looks at
Bolton’s dull account of how men group a uniform series of clicks
into natural patterns, one wonders what it was that Hall had tosay, butti'ue

when one examines Bolton’s introduction, done in thespirit of Hall’s “synthetic

psychology," one begins to un-derstand. There Bolton discussed cosmic rhythms, physiologicalrhythms, the periodicity of attention and of speedi, fte emotional
effects of rhythm on savages and children, the place of rhythm inpoetry and music. Rhythm is a large subject.

In experimental psychology the investigation of rhythm has

been undertaken in connection with three important problems:(1 ) the determination of the temporal range of consciousness, (2)the establishment of the subjective nature of auditory rhythm andits

objective conditions, and (3) the decision as to the extent towhich kinesthesis is required to fix a rhythm. Let us consider thesematters in order.

Wundt, when he first formulated his system in 1874, conceivedof consciousness as having a given spread over what he called theBlickleld (focus -f- margin), containing wiffiin it the Blickpuvkt(fooui’) of clear attention. The span of the Blidspunkt constituted

the range of apperception, whi^ Wundt later measured by theamountof differentiated material correctiy reproducible after

tachistoscopic presentation.

The span of the Blickfeld was therange of consciousness, which Wundt thought was measured by
the content of a perception which can be identified as a wholewithout specification of its parts. Later he emplc^ed rhythmicalgroups as representative of this sort of perceptual material. Six

unrated beats constitute, he believed, the maximal range of con-

PERCEPTION OF TIME AND MOVEMENT

584

soiousness, for six such beats can be perceived as different fromfive or seven even tliough they liave not been counted. Grouping

increases the number of beats within the range to sixteen, Wundt—eightthoughtpairs, or four pairs of pairs.

In 1885 Dietze’s experiment in Wundt’s laboratory wa.!! instituted in the interests of this theory. He provided subjects with alarge number of rates of uniform beats, rates ranghrg from fourbeats per second to four seconds per beat, and tabulated the subjective rhythms that the subjects perceived. The largest group was

40 beats, five groups of eight each at the rate of four per second, a
perception that makes the range of consciousness in that case 10
seconds. His longest group in respect of time was 12, three foursat the rate of 3 seconds per beat, a perception that took altogether

36 seconds.
Bolton’s experiment in 1894 was similar to Dietze’s, but ho got

no unitary group of more than eight beats. WiOi rapid rates hefound a range of consciousness of about one second; with slower
rates the range

averaged about 1.8 seconds. Koflka,ina verythorough study of rhytlun in 1909, obtained durations of therhythmical groups varying from 0.65 to 5,6 seconds with a mode

between 1.1 and 1.6 seconds. It seems probable that Bolton’s andKoftka’s subjects may have adopted more rigorous criteria of unitariness than Dietze’s; but the matter is not likely to come to final

experimental determination, because the problem of the rangeof consciousness lost its motivational support when tlie very con-

cept of consciousness was seen to be ambiguous and its usefulness as a systematic tool became dubious,

The objective concliUoTis of rhythm have been worked out by aa number of investigators. The most important conditions are relative intensity of the members of the group ( accent ) , relative duration of themembers and relative duration of the intervals be-

tween members.

Meumann in 1894, contributing a pioneer paper in this field,
varied the relative loudness of sounds and concluded that a loudsound tends to lessen the subjective interval preceding it, to increase the subjective interval following it, and thus in general toconclude the rhythmic foot, A series of sounds at equal objective
intervals would thus be heard as an iambic, not a trochaic rhythm,

but Meumann’s conclusion was not confirmed by subsequent workers.

DETERMINANTS OF RHYTHM

585

Bolton, also in 1894, observed tlial any regularly recurrent contrasting members ol a series tend to determine rhythmical feet,that loud sounds tend to begin the group and weak to follow, thatsounds of long duration tend to end the group and weak to precede, J[Ie also found tliat all rhythmical feet are separated by intervals subjectively longer than the intervals within the feet, eventhough objectively all the intervals are equal.
Then, in 1903, Robert MacDougall found that a loud soundtends to increase the apparent duration of the interval precedingitand to decrease the apparent duration of the interval succeedingit,thus showing that Boltons Rrst finding depends on his second.

MacDougall was able to measure the strength of this effect byreducing tlie objective duration of an interval immediately pre-—hadceding a loud sound until he had just destroyed the rhythm

found, as he put it, the “indifference point." If all intervals areequal, dien the interval before the accented

members seems

longer than the interval after it; thus the accented member initiates the fool. If the Interval before the accented member is madeshorter tlian the other intervals, however, a point can be found—the indiflerenco point—where it seems equd to the other intervals in duralion. At the indiffei'enco point the rhythm is destroyed.

Miner, also in 1903, worked with visual rhythms and verified
the fact that the interval between feet is always perceived as longest.

He noted in addition that the duration of a light increases its

apparent intensity, but that may have been in part a retinal phe-nomenon.
Finally Woodrow in 1909 brought this whole matter to a satisfactory conclusion. He found, in the first place, that of two-rhythms

the trochee is more natmnl than the iambus, tlius confirming Bolton and MacDougall in respect of the fact that the accented mem-ber tends to begin the foot and that the apparent interval between
feet isTongest.

becomes subjective(1) Objective-- -On the other hand, the member of longest duration tends to end
the foot and thus to be followed by an interval of great apparent
duration; thus:

becomes subjective(2) Objective— or even-

Similarly the dactyl is the natural tliree-rhythm and the same rules

apply:

'

PERCEPTION OF TIME AND MOVEMENT

586

'

'

(3) Objective- - becomes subjective

-

-

I

becomes subjective(4) Objective

The lengthening of the objective interval in the middle of a ttochee—

mayj however, change it into an iambus; thus;- is heard subjectively as(5) Objective
^ -J
'

—

(6) Objective— —is heard subjectively'asThis finding led Woodrow to measure these effects by the determination of indifference points after the method of MacDougall.

For instance, if the objective interval after an accent is in-creased, the rhythm may fail or be reversed;(7) Objectivet—'- - may become subjective

—

'

-

/

The tliii'd historically important problem about rhythm is the
all rhythmizalion demands kiupslhests.

question as to whether

Again we must recall that the atmosphere of the late ninetccntli
century favored motor theories—motor theories of the perceptionof space and, by analogy, motor theories of tho perception of time.
Ever' since Lotze (1852) there had

been the suspicion tlmt all

visual extent miglrt be given in terms of cye-movomont. Wundt

made kinesthesis—the “great god Kinesthesis”—basic to all spaceperception. MUnsterberg made it basic to the perception of diu'ation.

A discovery that rhythm depends upon, or even reduces to,kinesthesis could have outraged no one. Rhythm is, moreover, agood subject for motorization. Both Wundt and Stanley Hall
drought iat the bilateral symmetry of the human locomotororganism provided, espcciaUy in walking, the genetic basis forrhythmical perception, making the two-rhythm more ‘natural’

than the three-rhythm.
All investigators discovered that auditory rhythms tend to be—Bolton, MacDougall,accompanied by kinesthetic accentuation

Stetson, Miner, Koffka. The head, the toe or the finger tends tokeep time. Titchener, after reserving judgment as to the existenceof purely auditory rhythms, finally concluded (1910) that, whenother kinesthesis is lacking, strains in the ear (kinesthesis from thetensor tympani, he thou^t) provide the accentuation. Titcheneralso helped the kinesthetio theory of rhythm by introducing at thisRHYTHM AND HNESTHESIS

587

time (1909) his context theoiy of perception, the tlieory that every
sensoiy “core” of a peroepliou is given its meaning by the addition
to it of a sensory or imaguial “context.” Ehytlim formed for tliis

theory the example par excellence. The auditory series is the core
which,is marked off into groups by the addition of the recurrent
kinesthetic context,

The frontal attack on this problem was undertaken by Ruckmick in 1913. He found, Uke his predecessors, plenty of kinesthesis.

He was inclined to conclude, moreover, that some sort of kinesthesis is theinvariable accompaniment of both auditory and visual

temporal rhythms in the initial stage of their formation, but thatthe kinesthesis in an established rhythm may nevertheless drop out

and the perceptual pattern continue in purely auditory or visual
terms, In some cases it is a visual context that fixes the pattern foran auditory core. Thus Ruckmick helped to diminish tlie prevalence of motor theory in the explanation of temporal and spatial
perceptions, at a time when motor theory was aheady being deserted and the alternative phenomenological theoiy of Gestalt psy-

diology was about to be brouglit forward.
After all, the question of the universality of kinesthetic context

Many percepMany arc not.

lor rhythm might be only a question of definition.
tions aregrouped by concomitantkinesthesis.

Tachistoscopic presentation of Schumann’s checkerboard (Fig.

35A, p. 248) or Rubin’s figures (Fig. 36, p. 251) may show grouping without eye-movement. The unitary nature of a trill that occurs in a melody does not depend upon kinesthesis of the large

muscles or even of the tensor tympani. There are perceptual pat-terns— even recunent temporal auditory patterns—wlfich occur
without kinesthetic context. Are they rhythms? One could define

rhythm as the kinesthetic determination of visual or auditorygrouping, just as readily as one could define emotion as an affective

experience which includes prominent organic processes. Such a
definition of rhythm would, however, narrow the concept unrea-

sonably and require the dropping off of kinesthesis in an habitu-

ated rhythm (Ruckmick) to be interpreted as a disappearance ofthe rhythm. In general, the broader definition has seemed better;kineslhesis is not a sine qua non of rhythm.

588

PEHCEPTION OF TIME AND MOVEMENT
Perceived Movement

At first the perception of movement did not seem to be a special
problem. If one can localize visual and cutaneous impressions andifthe localization changes continuously in time,

why theri one

must perceive movement— or so it seemed. If a circukr excitationon the retina gives rise to a seen circle, must not a moving excitation result in a seen movement? In Johannes Miiller’s time, and—exceptmuch later too, perception raised no problem

in tlie illu-

sions where excitation and experience do not exactly agree. Only

then had something to be explained. It was for this reason that interest in perceived

movement began with the discovery of thestroboscopic movement where a discrete—

illusions of movement

displacement of the stimulus gives rise to the perception of a single
continuously moving object, and the negative after-sensation of

movement where watcliing one movement makes stationaiy objects seem afterward to move the other way.
This history starts in the 1820’s willi Purkinjo’s phenomenological description of seen and fell movement in giddiness (see pp.

535 f.). The rotated giddy subject feels himself revolving in one
direction and secs his environment spinning in Iho opposite direction, continuing to spin after he has slopped.

Did Purkinjo thus

discover the negative aftcr-sensation of seen movement? Perhaps.

Such movement is, of course, complicated by the negative afterimages of felt movement and by the nystagmic eye-movements,

The period under discussion—about 1825-1850—^was, however,an era of popular scientific interest in the magic of illusions, theperiod of the invention of the stroboscope, the stereoscope, thekaleidoscope and numerous other trick instruments for exciting

wonder by deceiving the eye, instruments which the scientists described and which then found their way into the parlors of theVictorian intellectuals (see pp. 266, 268-270, 285-287, 307^.

Thus it came about, in the same year that Purkinjo was discussing giddiness (1825), that Roget, the man who wrote the Thesaurus, published a description of the appearance of a moving

carriage wheel seen through the vertical apertures of a paling fenceor palisade. The wheel may seem to move horizontally without
rotation and with the spokes curved, convex downward on bothsides. Roget pu?)lished a picture of the illusion and an explanation.

He noted how the successive appearance of the different parts of

STROBOSCOPY

589

a spoke, as the wheel moves along and (he spoke moves up or

down, would combine to give a total impression of a curved spoke,a curve for which ho wrote the formula. This is not a simple stro-

boscopic phenomenon, but the observation was an appropriate
introiijction to it.

In 1831 Michael Faraday published a paper on what is morenearly a true stroboscope.

He cut from white cardboard two

Fio. 03. Platead’s Stooboscopb(1833)The disk is mounted so that(1831)The two while cardboard wheels
rotate inopposite directions andthe spohes

are viewed

against a

dark background with theregard parallel townoels,Oneline oftlie

axis of theastationarysees"spectral” wheel with double theitcan be ^un around its center. It
is turned to lace a mirror, aod theobserver behind it views an imageof a dancer in die mirror Ihroum
the rectangular sbts (black in ngnre).

As the slots successively ex-pose the successive pictores, thedancer is seen to execute a turn.

number of spokes and spaces. The

Plateau called

illusion anticipates the stroboscope.

phenakistoscope.

this

instrumentawheels, each with rectangular teeth or spokes and with spaces be-

tween the spokes equal in size and shape to the spokes. (Fig. 92.)

He mounted them on the same axis but on different axles, arranging for them to be rotated in opposite directions. Then he spedthem up until the white teeth, seen casually at an angle, fused asa gray blur. Sighting the spokes along a line parallel with theaxis in such a way that one wheel was directly behCid the other, hefound, however, that he could see a ‘spectral’ stationary wheel with

590

PERCEPTION OF TIME AND MOVEMENT

double the number of ill-dcfincd teeth and with as many blurred
spaces between them. His explanation was not wholly clear, but

Plelmholtz later gave this account. When the spokes coincide, witha front spoke obscuring a back spoke, the total field is relatively
dark, half black (the background)and half white; whgn the

spokes are staggered, the total field is light, all white for an instant.

The lighter field prevails over the darker. The spokes of bothwheels are seen, though bluiTed, near the time of maximal illumination. Then this impression is reenforced at the next moment of— one with—through the distance between spokes. Thismaximal illumination when the wheels have rotatedrespect to the other^theexplanation makes the phenomenon truly stroboscopic.

In November, 1830, Plateau, die Belgian scientist who contiib-

uted so much to visual science, constructed an instrument which
consisted of the disk pictured in Fig. 93.

One holds the disk,

mounted so that it can be spun around, up to a mirror, with theface shown in the figure toward the mirror, and one stands behindit,looking, while the disk is spun, at the mirrored image tliroughthe slots cut in the disk. He sees, of course, successive instantane-

ous images of the dancei' depicted on the face of tlic di.sk, withthe dancer revolving through one sixteenth of a complete turn ineach successive image. The image appears to move contmuously,

and Plateau, imbued with the nineteenth-centiuy belief that tlio
normal function of the senses is to teU the mind die tnidi about
the external world, called the machine an ‘eye-deceiver,’ a phenahstoscope. Plateau gave his first model to Quetelet (the Bel-gian who invented statistics and applied the nonnal law of enur
to the distribution of human characteristics) to give to Faraday,

because he believed that the instrument threw light on the explanation of Faraday’s wheel-and-spoke illusion. Later—in January, 1833—he published an account of the instrument and of thephenomenon.

Meanwhile Stampfer in 1832 had invented a similar device
which he described in a brochure whose preface is dated July,
1833. He called the instrument a ‘visual whirler’ or stroboscope, of

which he is often considered to be the inventor. It is true that heconceived the principle without knowledge of Plateau and madeup fire name which was finally adopted, but Plateau has priority'

for the idea.

In 1834 Homer invented the cylindrical stroboscope, similar to—
AFTER-SENSATIONS OF SEEN MOVEMENT

591

the one in Fig. 94. A strip ol paper, bearing piotoes showing Rie
successive positions of some object, is slipped inside die cylinderaroundwall at the bottom

its

and is viewed from above down
tlirougji

the

slits

at

the

top.

Horner thought the ehinination of
the mirror a great advantage andcalled his machine a daedaleum,
after the mythical

Daedalus towhom the Greeks attributed theinventionofmany mechanicalwonders from the minotaur’s labyrinth in Crete to the wings with

Fig. 94. Hodneb’s StiioboscopeThe

which he flew away from Crete.
In thisway the stroboscopic

principle that the discrete dis-placement of the stimulus-object
can give rise to the perception ofcontinuous movement was fully
established.

The word

strobo-scopk has nowadays this mean-eaccessive pictures are ona strip ol paper inside the cylinder
the bottom and ore viewed

atobliquely Uirough the slots above
tliem as the c^inder lotntos. Cf.

Fig.

No minor

0S.

Iloruorcalledthisisrequired.

instiiunoutadaedoleum (1834) and publishedBO picture. This dgurc, with thieesets ni slots, is reproduced from
Ilehnlioltz(1896).

ing in spite of its different ety-mology. The next event was the discovery of the negative aftersensation of seen movement.

In 1834 Addams published “An Account of a Peculiar' Optical
Phacnomenon Seen after Having Looked at a Moving Body”
the water-fall illusion. If one gazes at the moving water of a fall

and then looks away at rocks beside the water, the rocks appear tomove up. The deck of a boat seems to move forward if one turns
his regard to it after inspecting the water over the side moving aft.

Addams sought to explain these illusions in terms of the persistence of compensatory eye-movements: the eyes move with themoving stimulus and, having reached a limit, shift back and move
forward again. The backward shifts continue, he thought, whenregard is changed to a stationary object.
In 1850 Plateau described what happens when one views aslowly rotating disk that has an Archimedes (arithmetical) spiraldrawn upon it (Fig. 95). Mainly he was interested in the rings ofcolor generated by a white spiral on a black groiuid, but he also
noted that such a disk tends to expand or contract, according to its

PERCEPTION OF TIME AND MOVEMENT

592

direction of rotation, that the conti'ary movement is seen if thedisk is stopped, and that tliis eontrary expansion or oonlraction is— the experimenter’s—to which the subject turns his gaze. In 1856 Oppel studied

transferred to any other stationary object

like

head

the phenomena of movement obtained with Plateau’s disk, andthen Mach took up the problem,
putting his student, Dvorak, on
it in 1870,

and later discussing it

in his classical monograph on Be-

wegungsemppndungen in 1875,
H. P. Bowditch and Stanley Hah
used the disk in 1882,

Meanwhile Helmholtz had discussed the water-fall problem in
1866.
Fig. 9S. Plateau’s Spiiul (1850)

The disk is seen to expand os it
rotatesitobekwise, or to contract asrotates counterclockwise. Tho re-verse

motionISperceivedwhen

He pointed out that thesame illusion ocairs in a train;
after viewing the moving landscapo through

lire

oar

window,

the aisle of tho car is seen to movein the opposite directionwhenslopped or when otherthe eyes m'e turned upon it, He

objects are fixated, after the moving
disk has been observed. Cf Fig. 96.

espoused Addams’ theoiy of com-the diskis.

The device is sometimes attributedtoMach, who used a black,broaderalso

spiral.

Plateau’s disk

induce colored rings.

may

eye-movement, andWimdt, who always turned topensatorykinesthesisforthe explanationof spatial perception, lent theweight of his prestige to this theory. Bowditch and Hall even described a mechanical 'water-falT (Fig. 96), to which James’ namehas often been attached because he reprinted a sketch of it in his
Principles (1890). (Or did James build it first?)
Plateau’s spiral, however, told against the eye-movement theory.

The eye cannot execute movements of expansion or contraction.
Thus Dvorak, writing with Mach’s approval, argued against Helmholtz’s view; and Bowditch and Hall, describing a number of illusory rotatory movements, as well as the expansion-contraction of

the spiral, made the same point vigorously. But, if the perception—in the stroboscope, in nega— not due to compensatory eye-movement,of movement when nothing moves
tive after-sensationisto what is it due? Dvorak said it must be a special retinal process.

theories of perceived movement

593

the
Vierordt (1876) appealed to relativity and contrast. When
may
shore
near
water
the
said,
swilt,
heis
mid-stream
current In

appear to move upsti-eam. The moon can be seen scurrying behindweseemingly .still clouds. Often when the background moves,think -ourselves moving, as whenin a railroad car we see anothertrain

start.

If

Vierordt noted,

theforefinger,

held againstisthe forehead andiswhile the head

moved from

is

kept

still

side to side, then the head is per-ceived as moving one

way andthe stationary finger theotlier.

Thus could Silvanus Thompson,
citingnumerous other Instancesof this sort in 1880, lay down ageneral law of “subjective oom-

plementaiy motion.” The retina,

he said, adapts itself to long continued movementj then the fieldsurrounding the movement, or
the field viewed after the move-

ment, tends to be perceived as

moving in the opposite direction
principle

by “contrast”— anotunlike that being invoked at thesame time by Helmholtz andHering to account for simultane-

were

other

The crank moves a striped bond,seen through the aperture, down(or up). The subject sees a reverse movement when the band is
stopped, if he looks at the back-ground or if he boks at anoflier ob-

ous color contrast.

There

Wateb-fall Illusion:
Bowditch and Hall (1682)

Fig. 96.

theories.

Wundt appealed to fusion as wellject.

This instrument is usually at{ Did he build it

tributed to James.

first without describing it in print?)

as eye-movement in order to ex-movement. Marbeplain the perceived continuity of stroboscopic
The school
the fusion in terms of persistent after-images.

plainedof GestaltqualUtit (von Ehrenfels, 1890)

held that perceived move-place
ment is a form-quality, founded on the change ofin time—change of pitch in
Hke a melodic movement which is founded on
but there wasnowhere,got
opinions
andarguments
These
time,

another that brought forth fruit.
held that
Dvorak (speaking, it would seem, for Mach in 1870)

594

PERCEFnON OF TIME AND MOVEMENT

movement depends upon a simple retinal process and must be
understood in its own right and not as a space-time complex,
Vieiordt presented a similar view when ho argued in 1876 thatmovement is nativistic and primary, ending his paper with; “Nihil
est in intellectu, quod non antca fueiit in sensu.” Movement is asensation in itself, Vierordt said—like time in the Zeitsinn.
Exner had meanwhile performed experiments which led him toa similar belief. He had presented the subject with two spatiallyseparated, successive, electric sparks and had found that the time-order of the sparks can be correctly perceived (on the average)

when the interval between them is not less than 0.045 seconds.
Then he put the sparks closer together in space and got, not succession, but the stroboscopic appearance of the movement of asingle spot from the earlier position to the later. Tire tlircshold forthe correct perception of die direction of this moving spaik was
only 0.014 seconds. In other words, movement caused by the dis-placement of position in time can be sensed correctly as to thetemporal order of die stimuli when the time-interval itself is too
small to be perceived as such. Movement must, tiieroforo, involvea special process, and Exner argued that it is dius iv sensation andnot complex like a pcrcoption.

Against diis systematic background G. H, Schneider in 1878
asked the question; Why are objects so much more easily noticed

when they move a litde than when they ai-e at rest? He found thata shadow, too faint to be perceived at rest, is noticeable when it
moves. The ratio of the intensity of die just perceptible moving
shadow to the intensity of the just perceptible still shadow he determined as of the order of 2;1 and 3:1. Similarly the finger’s
shadow cast by the sun on the closed eyelid is invisible until thefinger is moved. Schneider discussed at length the biology of move-

ment—the way in which animals become invisible in ‘(Jeathshamming,’ the manner in which the stalking animal avoids alarming his prey by remaining quiet, how birds and squirrels wiU ap-

proach an immobile person and flies light on a stuffed bird orfrog, and, conversely,

how a kitten cannot avoid attention to amoving ball and how a person will attract attention by jumping

up and down. In other words, the organism does not necessarily
perceive a thing, and then see it move, if it moves; it can perceive afaint or small object only if It moves. Biologically movement isprior to the other conditions of sensation.

b

APPARENT MOVEMENT

595

It may therefore be said that the thought of the 1870’s and 1880’s

pretty well established the fact that seen movement is not due
solely to eye-movement, but is an immediate sensory phenomenon,

in no wise dependent upon an inference based upon change ofplace in time, Thereafter, the adequacy of stroboscopic movement

was aSiply confirmed by Edison’s invention of tlie kinetoscope in1894 and its subsequent development in moving pictures. The
problem of seen movement did not, however, again figure importantly in the psychological laboratories until Wertheimer’s paperin 1912, the paper that begot modem Gestalt psychology.

Wertheimer simplified the observational situation. Instead of
the continuously occurring discrete displacements of the strobo-

scope or the kinetoscope, he arranged, with a tachistoscope, for asingle discrete displacement of a simple geometrical figure, a line

or a curve. The first member presented he designated o, the secondb.

When the time-interval between a and h was relatively long(above 200 millisec.) the subject perceived succession, first a,
Uien b. When the interval was very short (less than 30 millisec.),
the perception was one of simultaneity, a and b together. In be-

tween suocessivity and simultaneity he got movement, the optimal
interval for whioli was about 00 millisec. For times between the

movement-optimum and successivlty tlie subject perceived various kinds of partial movement For instance, as the time-intervalisincreased above the optimum, the seen

movement tends tobreak up into a dual movement in which each part moves witha lack of continuity, or into a singular movement in which one partmoves and the other is stationary. In these cases, instead of sednga single object move, the subject sees two successive objects with

one or both of them moving. Within this interval there is also thecase of pure movement, which Wertheimer named <^, movement

which connects the objects and has direction between them but
seem* not in itself to be an object. The series of phenomenal impressions for increasing time-intervals is therefore something likediis;simultaneity—-optimal movement—partial movement—puremovement (c^i)—succession.
Wertheimer pointed out— essentially—that this finding showsis not essentialthat movement is movement. The succession a—to it. It can occur as 4 without being an object. For optimal move-

ment one sees a single object moving, not an o tujpning into a h. In
thiscontention Wertheimer was following out the tradition of

PERCEPTION OF TIME AND MOVEMENT

596

Mach and Exner, but he went furtlier. He insisted on the validityof movement as an immediate experience without reference tobasic constituents, on the ‘givenness’ of <j> and its irreducibility toterms of space and time. Out of such an intransigent phenomenol-ogy arose Gestalt psychology.
There is one other item of importance in Wertheimer’s paper.

He suggested that seen movement may be the consequence of a"physiological short-circuit” in the brain. Given exactly the righttime-interval, the excitation at one point may be

drawn over tobecome the excitation at the other, the process being—-not a retinal
process, as Dvorak had thought—but a cortical process which isthe physiological substrate of apparent movement. This form ofpsydiophysical parallelism follows the axioms of Mach and G. E.
Muller, and anticipates the isomorphism of K6hler which has be-come so nearly an indispensable for Gestalt psychology (see pp.
88-90).

Wertheimer’s paper, supported presently by the enthusiasm of
the growing school of Gestalt irsychology, was a great success, forit

was the starting point of well over a hundred papers on apparent

movement during the next-thirty years. At first Iherc were Inil a
few studies by Gestalt psychologists in Germany under the influence of Kofika and Kohler, but tlie Americans look up the topic
in the 1920’s

with considerable zeal. The best that we can dowith this large literature is to select seven important topics, considering each of them briefly.
1.

Kinds of movement. Immediately after Wertltoimers paper,

Kenkel (1913), working under Koftlca’s direction, described threedifferent kinds of apparent movement which he named u, (9, and y.

A little later Korte (1915), another student of Koflka’s, added
8-movement, and Benussi distinguishedbow movement in his

study of apparent tactual movements in 1916. To these may be

added DeSflva’s split movement (1926). The meanings of theseterms are as follows;

fi-movment (Wertheimer, 1912) is pure movement, the move-

ment that is seen without a moving object and the basis for theclaim that movement is as primary as any other sensory phe-nomenon.

^^movement (Kenkel, 1913) is the movement of an object fromone position- to another, the land of movement that is most

TYPES OF APPARENT MOVEMENT

597

frequently investigated and the kind that is usually indicatedby tlie phrase optmal movement
a-movement (Kenkol, 1913) is the change of size of an object
under successive presentation, Kenkel was working with the
leijgthening and ^orlening of the central line of the MiiUer-

Lyer illusion (Fig. 33, p. 243) when its two forms are presented successively.

y-mooement (Kenkel, 1913) is the expansion or contraction ofan object as the illumination is respectively increased or decr-eased.

While y-movement, like o-movement, seems to rep-resent a change of size, the experiences are quite different. In

y-movement the object swells out in all directions or closes

up upon itself,
i-mooement (Korte, 1915) is reversed movement which occurs

when the later stimulus is much brighter than the earlier.
Then tlie movement is in the direction opposite to the orderof presentation.

Bato movement (Banussi, 1916) is a curved movement which

does not follow the shortest distance from the first stimulus
to the second. In vision an obstructing stimulus between thetwo successive stimuli may cause the apparent movement tocurve around die obstruction, often out of the plane in which
the stimuli lie.
Split movement (DeSilva,

1926) sometimes occurs in ambigu-

ous cases, as when a vertical line, followed by a horizontal line

perpendicular to it at its base, is seen to divide and rotate bothto tie right and left to form the long horizontal line,
2.

Nature of movement Systematic positions die hard. Titch-ener in 1915 had surrendered his belief in elementary sensations,and was holding that the conscious ultimates are the sensory dimensions (attributes; see pp. 23-25). Under his influence perceptiohs were being studied as integrations of these dimensions(see pp. 509-512). In 1920, from Tit^ener’s laboratory, Dimmick

published an analytic-phenomenological (a contradiction of terms

from the Gestalt point of view) study of seen movement. He concluded thatisa specific integration of quality, duration and ex-tent—a peculiar gray flash between the two members. Dimmick reported^t the quality of</>is always

gray; Higginson denied thisgenerality in 19^, obtaining colored 4>’s for colored stimuli. Later

PERCEPTION OF TIME AND MOVEMENT

598

experiments indicate the quality of seen movement for coloredstimuli to be sometimes gray and sometimes colored.

Several studies at this time showed satisfactorily that optimal

apparent movement, obtained from successive discrete stimuli,

may be indistinguishable from real movement. One of the Jrsl ofthese was by Dimmick and Scahill (1025).

Laws of movement, Korte in 1915 worked out the well-known3.

laws of optimal movement tliat bear his name. They show how
optimal movement depends upon the distance between the stimuli (s), the time between the stimuH (t)and the intensity of thestimuli (1). They are:I. Sopt

II. iopt

III. iopt

t,

if t

l/t, if ss,

if i= const;==<opt

const.;

fopi

const.;s„pt= const.
~if~ 1/i, s = const.
s,

/

if

i,

if i

= constThe first formula is read; if the time-inlcrval is constant, the optimal distance for apparent movement varies directly with tlie intensity. If the spatial separation is increased, the intensity must bo

inaeased, or the optimal movement breaks down. Any two relationships in either of the columns above determine the other four.

A simpler way of roprcsonling this relationship is to suppose thats, tand 1 are rectilinear coordinates in tridimensional sp.ico. Then,in such a system, the optimal conditions for apparent movement

are represented by the three coordinates of every point that lies
in a particular surface which cuts tliis space.

On one side of thesurface lie the conditions for the perception of simultaneity of themembers; on the other side, the conditions for successivity.
Korte’s laws hold under his special conditions, but exceptions

have been found, for there are many other determinants of optimal

movement.
4.

Determinants of optimal movement. Almost every study ofapparent movement has something to say about its determinants,

but there have been few large generalizations. Higginson (1926)

and DeSilva ( 1926, 1928 ) have established the largest numbers ofconditions. DeSilva made it clear that attitudes affect the perception, that the analytical attitude is unfavorable to it, that a com-mon-sense, passive attitude is favorable. Thus he found that meaningful objects move more readily tlian simple lines; the arm of asketched man vvill move up to his forehead in a salute more readily
than one line will rotate toward another through the same angle.

DETERMINANTS OF PERCEIVED MOVEMENT

509

Guilford and Helson (1929), by photographing eye-movements,

proved(if proof were sUll needed)that eye-movements are notdeterminants of apparent movement.

Perhaps tile broadest generalization was made by Brown andYoth (,1937), working in the recent Gestalt tradition with fieldforces. As evidence that all phenomena in the space-time field are
related vectoiiaRy, tending in general to attract one another, theypresented numerous examples of special fields in which particular

movements were predicted on the basis of such dynamic hypotheses, and then they exhibited the confirmations of their predictions.

A simple instance is that of the stimulus-object which actually roa circle. Brown and Voth predicted that the atliaction
among the excitatory traces of the object would tend to pull thetates incircle together, decreasing its apparent size, and that the shrink-

age would increase with the speed of rotation, since the fasterrales would allow less time for the dissipation of the traces. Trueenough: the faster lire stimulus rotates, the smaller is its apparent
circle of rotation.

This paper came, however, late in the period

which wo arc discussing, when Gestalt psydiology was alreadygiving place to general ‘field theory.’
5.

Physiology o/ movement. So well does Wertheimer’s corticalshort circuit fit the isomorphism of Gestalt psychology that Kohler

elaborated and modified the theory in 1923, shortly after he hadlaid down his general principles for isomorphic brain fields in his

Physische Gestallen of 1920. The Americans, however, have al-ways stuck more closely to the conventional neurology of theneurologists, and brain fields have not been popular with many ofthem. Higginson in 1926 published nine instances which heclaimed contradicted Wertheimer’s theory. For instance, he wasable to get simultaneous movement in different directions in thesame^ region of the field, a situation that could hardly occur if localized excitatory potentials are moving in that region so as toachieve equilibrium. The whole question must remain imsettled
until

we know whether the brain is constrained to act under the

all-or-none law of conduction

amongby way of connections formed

insulated fibers, as the neurological facts indicate, orwhether it is free to act by the equilibration of excitatory fields, as
the phenomenological facts indicate.
8.

Tactual movement. In 1885 Stanley Hall an3 Henry Donald-son determined the capacity of observers to discriminate cutane-

600

PERCEPTION OF TIME AND MOVEMENT

ous movement, inventing for this purpose the kinesimetor, an in-strument for dragging a Hght ptessiu'e-sthmilus along the skin at
various uniform speeds. They found that the spatial threshold forthe perception of the direction of tactual movement 'is about onefourth the size of the threshold for the simultaneous discrinjinationof two points, a result which makes the tlucshold for direction

about equal to the thi'eshold for the discrimination of two points
successively applied (of. p. 477). More important than this, however, was their discovery that movement can be perceived correctly as towhether it occurs or does not occur for distances

too small to give a correct perception of the direction. That conclusion, of course, fitted in with Exner’s

and Schneider’s; move-

ment is primary and can be correctly appreciated even when its
direction and extent remain unknown.

Von Frey and Metzner, in their work on the successive twopoint Hmen in 1902, noted that the discrimination of the two points
often takes the form of being a perceived movement—a “shifting”

or a "stroking” (cf. p. 479). It was not until Wertheimer’s paper,

however, that research in apparent tactual movomonl was stimulated. Then Benussi (1913, 1916) undertook to duplicate Werthei-

mer’s visual experiment for touch.

—shiftings, strokings,

Ho got “khiohaplio” movementbows—but it was not “objectless,” always an"Etwas” moving. He concluded, therefore, that there is no pure 0
in touch.

Some of his movements were over great distances, asfrom a finger of one hand to a finger of the odaor with die arms
outstretched, a distance of 140 centimeters. He, an act psychologist, attributed the perception of

movement to an act of judgment,

and one would hardly expect to gel a pure ^ for these huge distances.

Buitt in 1917 was able to confirm Korte’s three laws for touch.

Whitchurch (1921) showed that the conditions for apparent tactual movement are less compulsory than they axe for visual move-

ment. Her optimal conditions yielded movement only about 60

per cent of the time. Andrews (l922) showed that Benussi’s bow

movement does not occur except under an attitude favorable to it;
the same objective conditions can always yield a straight movement. Hulin ( 1927) gave the fullest account of conditions and confirmed Whitchurch on the non-compulsory nature of the conditions, obtaining''apparent movement in 64 percent of die caseswith optimal conditions. His finding that “bewilderment” charac-

TACTUAL AND AUDITORY MOVEMENT

601

lerizod tlio altihido of the subjects in observing apparent tactual

movement accords with Benussi’s conclusion that the perception
ismediated by judgment and is not an immediate
7.

<l>.

Auditory nwoement. If tones can be localized, Urey ought to

movB^when the localization changes. Such auditory movement
has been recognized ever since It was discovered that a continuouschange of dichotic phase gives rise to a continuous change of locahzation (see pp, 387-391). When phase is changed in 4is man-—often called a "phantom”—moves around the headner the soundfrom one side to the other and, when the shift of phase is morethan a wave-length, either “moves” or “jumps” through the headto the otlicr side and starts to move around the head again. It is

more probable tliat the shift "through” the head is a judgment
rather' dian an immediately phenomenal movement, for tlie soundsometimes appears on one side before it has left the other.
Burlt in 1917 undertook to produce apparent auditory movement by the discrete displacements of sounds. He obtained results
similar to Wer-theimer’s and Korte’s but decided against Werthei-

mer’s shoxl-oircuit theory booairse he thought tliat diflerence of
localization would not moan difference of spatial projection in thebrain. Later auditory theory is, however, against him on this point.

Koster,on the otlior hand, decided in 1926 tlrat there is a pureauditory <]b, in which there is movement when no “Etwas” moves.

Then Mathiesen in 1931 indicated that apparent arrditory movement Is even more adventitious than tactual, for she found no conditions which she could regard as compulsory, getting apparent

movement in only about four per cent of her 6000 trials. Those
who, like von Hornbostel, are interested in demonstrating the"unity of the senses” (p. 27), have naturally wanted to see auditory apparent movement turn out to be like visual and tactual.
Brrrt1;’s objection,

however, will continue to be of sigrrificance until

we know more about the relation of auditory localkation to brain
localization.

Such is the history of perceived movement. Beginning with thenotion that there is no special problem, that movement on theretina or skin is a movement of nem'al excitation which can, ofcourse, be perceived as such, sense-physiology found a problem

when tire illusions were first desor'ibed. Movement can be perceived the scientists then realized—when nothing moves. It can—

PERCEPTION OF TIME AND MOVEMENT

602

be perceived for discrete displacement—in tlie stroboscope— orfor no dispkeeraent at all-in a negative after-sensatiou. Still, ex-

cept for tlie eye-movement theory, explanation remained anchoredfor the most part to the logical analysis tliat the cause "of. movementisnothing more than displacement of the stimulus in spa«e andtime, Ulthnately it was Wertheimer’s insight of 1912 that dismissed
this conventional explanation as a false tautology, to show how thephenomenological approach can set the problem and also begin
to solve it. He who would understand the nature of the positive

contribution of Gestalt theory to psychology needs no better tutor

than this history of research and thought on the perception of apparent movement. Problems cannot be solved until they are discovered.

Notes
On the inteirelatioa of the senses
in respect of mutunl fadlitalion
inhibition, see theby G. M.
oililation

andexcellent review

Gilbert, Inter-sensory la-andinhibition,

/.

pmd

Paijohol, 24, 1041, 381-407. On oilier

generalmatteis

Chapters 1 andof
2.

sensation,seo

On the Woher-

Fechner Intcnsltlve functions andon space perception, see tlie chap-

Nature, 1739, PL. 3, csp. sect. 3. On
the notionil

ihe snooessionasameuioiyorsomeunitaryisho pcrw'Ivcd

loduration,

seo

Thos.

limya on the Inlellcotml
Pomra of Man, 1785, III, Chap. S;
Uaid,

Brown, Lcoturaa on the Philosophy of t/io Ilunian Mind, 1820,

Tlios.

I, '293-208;

theters tor the special senses.

that

other inlcgralive process is ncccssniyJmnos Mill, Analyala of

Human Mind, 1829. Cliap. 10.

esp. the diird poragrapli; W. Wnndt,

Grunddige det phjaiohgbchm Paxjchologie, 1874, 680-683, and more

Perception of TimeIn general, see H. Nichols,

psychology of time, Amer.
chol, 8,

1891,

453-529;

J.

4,

The

elaboialely

in

Psy-

/lihrang

dio

1891,

Eng.

In

tans.,

editions;

Ein-

Paijoholo^a,

1911,

later

1912,

esp.

Chap.

1;

68-112; V. Benussi, Psychologic det

Wm. James, Principles of Payohol-

Zeltauffoantne, 1913; E. G, Boring,ogy, 1800, 1, 605-627.

The Physim Dimensiona

of

Con-

On tile consdous though specious

sciousness, 1933, 127-149.

present, see E. R. Ckiy, The Alterna-

For n resumd of the views ofseventy-two philosophers, see Nichols, op. dt., 453-502. On the perception of time as dependent upon

tive,

1882,

lishedthisthe succession of ideas,

James, op. df., 809. All other writers seem to dto James for him, prob-

see Tlios,

Hobbes, De corpora, 1655, or Eng.
tarns.. Chap. 3, esp, sect. 3; John
Locke, An Essay Concerning Kuflian
Vndetatanding, 1690, Chap.
14; George Berkeley, Principles of
Human Knowledge, 1710, sect. 98;
David Hume, rrectise on Humanesp. 167 f., who pubbook anonymously, invented the term apecioua present,
and is dted at some lengUi by

ably because tliey learn about himfrom James and fall to pierce theanonymity of his book, See also
cit.,
608-610; L. W,
Stem, Fsyobische Frasenzdt, Z. Psychol, 13, 1897, 325-349.

James,.

NOTES
On durnllon as a simple sensallon
immudlale experience, sec E.
Unteisuclumgen iiber den

or an

Mach,

der mere,

Ohres,

SUzun^sber.

Wien,mnlh.-natnrw.

10, 1870. 181-200; A.
HBriug, Versuche iiber das Vntcr-

(2)',

1805,

13a-150. esp.

scheidungsoermogen des Horsinims

des

51

Cl..

51 (2),
1865, 133-150; rrorinted in Unfersuch. Naturhhre des Menschen und

Wiss,

Zeitsimi

Akad.

603

Wien, math.-naturw. CL,

150, in’\vhich Uie point of view

Scitrage

implicit;is/uf ZettgrSssen, 1804; K. Vierordt,

zw Amlijse derDer Zeitsinn, 1868; J. Kollert, Unter-

Empjindungen, 1880 or later cds.,
chap, on Zeitcmpflndung (103-112
in 1 ed.), in which the point of viewsnehungen

den

iiber

Zeilsinn, Phil

Stud., 1, 1882, 78-89; V. Estel, Neue

Versucheeft.,iiber den Zeitsinn, ibid,,
1884, 37-85; M. Mehner, Zur
Lehre vom Zeilrinn, ibid., 2, 1885,
546-602; R. Glass, Kritisches und

1938, 127-149, esp. 127-129, 133-

Experimentelles uber den Zeitsinn,

isexplicit;

E. B. Titchener, Sensa-

and system, Amer. J. Psychol,tion

28, 1915, 258-267; Boring, op.

That

137.

psycliology

Gestaltac-2,

ibid, 4, 1887, 423-450; L. T, Ste-On the time-sense, Mind, 11,

cepts all phenomenological givens asvens,valid direct experience, including ex-

1880, 393-404; II. Miinsterberg,
Beiirage zur experimenteUen Psy-

andtensionduration,

is

well

too

known to require documentation
here. To choose one of tho possible

chologic,

score of imporlanl referonoes would

BeitrSgo zur P.syohologie des Zeil-bo invidious.

sinns,On tho atiliude of tho posilivisl

IV,

esp.

II,

1889, 1-68; alsoE.

89-120;1892,

Meumann,

Phil Stud., 8, 1892, 431-509;

9, 1893,264-306; Beiirage zur Psy-

toward duvalion, see E. G. Boring,

ehobgio des Zeilbewnsstscins, ibid.,

Temporal perception and opetallonism, Amer. /. Psychol, 43, 1930,

Psychol,

519-522.

Woodrow, The reproduclion of tem-

12, 1890, 127-254; Berichtigung, Z.
10,poral intervals,

1930,

Time-Sense
In general, on the time-sense, see
Nichols, op.

503-529;

esp.

clt.,

Principles

James,

W.

Psychology,oj011-019; E. B. Titchener,
1890,
Experiment^ Psychology, II, i, 196I.

158-160;

1890,

J.

473-499;

II.

exp. Psychol, 13,

Individiud

differ-ences in the reproduchon of temporal intervals. Amer. 1. Psychol,45, 1933, 271-281; The temporal
indifference interval determined by

the method ofmean enor, J.

exp.

Psychol, 17. 1934, 167-188.

Frobes, Lehr-

On the estimations of bng times

buch der experimenteden Psychologle, I, 1923, 379-395; H. Wood-—minutes, hours, days, years—there
has not been mmm experimental
work. On voluntary waking after apredetermbed interval of sleep and

198;

ii,

393-404;

J.

row,

The temporal indifference in-tervaldetermined by the method ofmean’ error,.

I.

Psychol,

exp.

17,

1934, 167-188, esp. 107-171.

the

text

are asfollows;

J.

N.

Czermak, Ideen zur einer Lehre vonZeitsinn, Sitzungsber. Akad. Wiss.
Wien, math.-naturw. Cl., 24, 1857,
231-236; reprinted in Utttersuch.
Nafnrlehre aes

mere,

5,

Mmsohen und det

1858, 65-71; E. Mach,

Untetsuchungeniiber

des Ohres, Sitzungsber.

denZeitsinn

Akad Wiss.

1

D. Boring and E, G.
Boring Temporal jiu^ments aftereral,

The experiments and papers citedinon the pbysiobgloal ‘clock’ in gensee.

sleep. Studies in Psychology (Tltcb-

ener Cammemorative Volume) 1917,

265-279; E. N. Brush, ObservaHonson temporal judgment during sleep,
Amer. J. Psyenm., 42, 1930, 406411; H. Hoagland, The pbysiologica] control of judgments of duration; evidence for a chemical clock,J. gen. Physiol, 0, 1933, 267-287;

PERCEPTION OF TIME AND MOVEMENT

604
II,

McLeod and M. E. RoH, An

B.

experiment in temporal disorientation, Acta psyahoL, 1, 1936, 381423 (the subjects were placed incamera, deprived of cues from theoutsideworld for long periods oftime).

A

hy of rhythm, Amer.

Psycnol.,

1.

4, 1913, 508-519; 28, 1915, 457459; 29, 1918, 214-218; 35, 1924,

no thorough review of the lileratime of rhythm, butH.

E.

thyme,
no.

is

Stetson,

Rhythmand

Monogr., 4, 1903,
413-466, esp, 413-416 forPsgcliol.

17,

On

the

objective

conditions

subjectivo

rhydims,

see

of

Meu-

E.

mnnn, Untersuchungen zur Psyehologie und Aestlietik dcs lUiylhmus,
Phil Stud., 10, 1894, 249-322, 393-

plo rhythm forms, Psychol Monogr.,

Cl A. Huokmiclt's bibliography of
blblloera714 titles on rhythm isseeC, Miller, Unconsciousness, 1942.

430; T. L. Bolton, op. dt., 1894; R.
MacDougall, The structure of sim-

Rhythm407-413. ThereUie concept of consciousness, see j.

references to J. F. Ilerbart

1812),
Vierordt
(

1903,

4,

Miner,

no.

rhythms,

309-412;17,

Motor,

visualB.

J.

and applied

1903, no. 21;
Woodrow, op. cit, 1909.

On

ibid.,

therhytlim,
Stetson,

E.

5,

role

see

of

Bolton,Miner,

kinestheslsin

MacDougall,

Koffka,TltAener,

11.

opp.

cltl;

A

Text-Book of
Pstjehoiogu, 1910, S44f. (rhythm),
B.

367-371 (context theory); and esp.
C. A. Ruckmick, op. cit., Amer. ).

(1888)

Psychol, 24, 1918, 305-350; Visualrhythm,Studios
Psychology
Intive study of rhytlimi the effect of(Titchoncr
Commemorativeume), 1917, 231-254,

R.

H.

Lotze

K,

(1888),and E. W. von Briiclto(1871); H. Woodrow, A quanlita-Vol-variation in intensity, rate and dura-Arch, Paijchol N.y.,

tion,

no,

esp.

14,

1909,

2,

die objective conditions of rhytlim;

Ruokinick,

Perceived Movement

1-11 lor tlie work on

The rOle of klnaesthesls

in the perception of rhythm,

Amer.

Psychol, 24, 1913, 305-359, esp.
308-311 for the history of opinion/.

on perceived movomont, see II. Ifclmhollz, Ilandbuch
In general,derpltysiologfschcn

Optlk,

1866, sect 22 (stroboscopy),

29

1860sect.

by dining Blicltfeid and
BUckpmkt; 6 ed., HL 1911, 330345, which gives the final development of the theory; G. Dietze, Un-eye-movement)
1 ed., 1867, 348-355, 602-604
3 ed„ II, 1911, 183-100, III, 1910,
207-209
Eng. bans., II, 1924,
218-224, III, 1925, 247-249; W.
Wundt, GrundxUge der physiologischen Psychologie, 1 ed., 1874, 571S75 (pretty meager); 6 ed., II, 1910,
611-626; and cf. intervening ^s. fordevelopment of the topic; E. Mach,
Grundfinien der Lehre von den Be-

tersuchungen fiber den Umfang deswegungsemppndungen, 1875, 54-85;

Bewusstseins bei regelmassig ardein-

W. James, Principles of Psychology,

on the role of kinesthesls in rhythm.
On rhythmical grouping os indicating the range of consciousness,

W.

Wundt,

Grandzugederphysiologischen Psychologie, 1

ed.,

see

1874,

717-719,

which begins thedoctrine

ander

folgenden

Schalleindcucken,

Phil Stud., 2, 1885, 382-393; T. L.

=(after-sensation,

=

=

1890,

II,

171-178; K. Marbe, Die
Erschelnungen,stroboskopischen

Bolton,Rhythm, Amer.

Psychol,

PM. Stud., 14, 1898, 376-401, esp.

6, 1894,

145-258; K. Koffka, Experi-376-385; B. Bourdon, La perception
visuelle de I'espace, 1902, 178-204

mental-Untersuchungenvom Rhythmus,

I.

zur

Lehre

1909, 1-109, esp, 35 f. As the mod-(best reference up to 1902); G. D.
Higginson, The visual appr^ension

em evidence for the ambiguity ofof movement under successive retinal

4Z.

Psychol,

52,

NOTES605

hme note sur de nouvelles applica-

1020,

03-U5,

Psychol, 37,
63-74; W, S.

NslI,

A dilicol investi^atlflu ol tlie

hnpeessions de la ratine. Bull Acad.

Amer,

oxoiliUions.

I.

osp.

visualappreliuiision

ibid,,

48,

thoiougji

maveniODl,

ol

1-42

(most
survey); S. H.
140-184
1941,

1936,
recent

Dortley> Vision,(work since 1926).

The

early

tions curicuses de la persistnnee desBelg.,

Scl.

are

J.

E.

'1820-1826, as cited on
p. 508 mpra; P, M. Hoget, Explanation of an optical deception in theappearance of the spokes of avmeel seen through vertical apertures, Phil. Trans., 1825, I, 181-140(Cennan Irans., Ann. Phys. Chem,,
81, 1825, 93-104); M. Faradav, Ona peculiar class of optical decepPurkinje,

1850, 254-200( 2),156, 1850, 287-292);

J,

Oppel,J.

Neue Beobachtungen und Versuohe
eine

discussions

18(Gorman trans., Ann. Phys. Chem.,

wenig

noch

eigenthumiiche,bekannle

desHeaotionsthiitigkeit

menschliclren

Auges, Ann. Phys.
Chem., 175, 1856, 540-501; V.
Dvorak, Versuche iiber die Naohbilder von Beizveriindorung,
Sftmngsber. Akad. Wiss. Wien, math.naturw. Q., 61 (2), 1870, 257-

H.

262;

Bowditoh and G.

P.

Hall, Optical illusions of motion,

Physiol,

1882, 297-307.

3,

S.
J.

On the1831,

20^

waler-fall

223 (German trans,, Ann.
Chem., 08, 1831, 601-606).

Phys.

and Hall, op, aft., 299 and PI. xviii,

tions,

J.

roy.

Inst,,

1,see

illusion,

Bowditoh

W. James, The perception offig. 1;On the invention of the strobo-

space. Mind, 12, 1887, 516-548, esp.

un

617 (which preprints Principles of
Psychologu, 1890, II, 245 f, with-scope, see J. A. F. Plateau, Siu

nouveau genre d’Ulusions opiiques,
Carraspondance math. phys. ObsarotUolre Umxellcs, 7, 1832 (butdoled Jan. 20, 1833), 385-308(phonaklsioseope); S. Slampfer, Die

SchaAen Oder opZauberscheiben, deren The-out the figure).

For the wo-movemeut theory, see
Addams, Helmholtz, Wundt, loeo.
oitt.
Againsttlio
eye-movement
Dvorak,strabaskofiisclten

theory,tischeditch and Hall, loco,

orte

und wissenschaldiche Anuisnd-

sectheories,

Macli,
oitt.

see Exner, op.

Bow-

On otliet
eft.

infra,'

1833),
the pro-Viorordt, op, cit. infra) S. P. Thomp-

perties of the daedaleum, a new in-

Set, 16, 1870, 234-240; Optical Ulusions of motion, Brain, 8, 1880,

ung,[n.v.];

1833(preface,

July,

W. G, Homer, On

strumentof

opticalMag., 3 sen,

4,

illusion,Phil

1834, 30-41 (Ger-son,Some new optical illusions, J.

280-298;

C.

V.

Ueber

Ehrenfds,

man trans., Ann. Phys. Chem., 108,

“Gestaliquabtiiten,"

1834, 050-655). Helmholtz, loc. oft.,

Pha., 14, 1890, 249-292, esp. 263 f.;

discusses the priority of Plateau over

K. Marbe, op.

who

cit,,

Vfschr,wiss.

1898, esp. 396-

credited

401; P. Linke, Die slroboskoplschenwith the invention. See also Bour-

TSuschungen und das Problem desSebens von Bewegungen, PsycholStud., 3, 1907, 393-545, esp. 455545 (presents Wundt’s views). For
still other theories and references,
see Wertheimer, op. cit. infra, 162-

Stampferisusually

193 (., (or his famous
insiniment in which black sectors
don, dp.

eft.,

on a disk pass continuously by anaperture,

so

that

a

singlesectorseems to move slowly up and thensnap back.

On

the

after-sensation

movement, see R.

Add.iins,

ol

An

seen
ac-

count of a peculiar optical phaenomenon seen after having looked ata moving body, Phil Mag,, 3 ser.,5, 1834, 373 (.; J. Plateau, Quatri-165,

236-246.

The importancethese unimportant theories

by aMarbe on one

hancedofwas en-withand Wundt,

controversy,
side

Wirth and Linke«on the other.

On movement as simple and biologically primary,

not an inference

PERCEPTION OF TIME AND MOVEMENT

608

or a perceptual complex, see Dvorak,On other determinants of move-

Exner, Uebcr das Sehon

ment, sec Iliggmson, 1920, op. cit.j

von Bewegungen uud die Theorie
des zusammenselzen Auges (he lu-

H. R. DeSilva, An experimental in-

op.

S.

cit,;

gued

the

tliat

especially wellinsects arc

forcompound eyesthedcLcrminaiitsofadaptedPsychol, 37, 1926, 469-501; Kinomatographic movement of^parallellines, J. geneial Psychol, 1, 1928,

of

Akad.

Sitzimgsberoi

apparent visual movement, Amer, J.

movement),
Wiss.
Wien,

perception

thevestigationol

Die Bewegungsempfindungen,Slot.,
12, 1876, 226-240; G.

H.

Warum bcmerken

wit

P. Guilford and II,J.
Eye-movements and thephi-phenomenon, Amer. J, Psychol,
41. 1029, 595-606; J. F. Brown and
C. Voth, The path of seen move-leichteralsment as a function ofPhil.,

2,

field,

CL, 72 ( 3) 187S,
156-190. esp. 156-165; K. Vlerordt,

math.-naturw.

Schneider,massig bewegte Dinge
ruhende?, Vjschr.
1878, 377-414.

loiss.

famousJustlypaper is his Experimentelle Studicn
ubei- dasSohen von Bewegung, Z.

Psychol.,

61,

181-265.

1912,

On kinds of movement, see WerUielmer, op. cit., 190-201, 221-227;

Kenkel,F.

Unlorsuchungen

Zusammenhang

Helson,A

zwischon

iiber

Erschcl-Wertheimer, op. cit., 246-250; W.
Kfihler, Zur Theorie der stroboskopiseben Bewegung, Psychol Forsai.,3, 1923, 397-406; G. D. Higginson,
Apparent movemcnl and the Gestalt,
J,

Psychol, 9, 1926, 228-252,
228-239. .See also II. II, Do

exj).

esp.

Silva, All amilysis of tlio viaiuil per-nuugsgrSsse und Erschoinungsbewcg-

ception of inovumenl,

ung belm einigen sogcnanntcn op-

ohd.

Tdiiaohungen,

UsMOii358-4«,

die vector-

1937, 543-563.
physiology of movenient, see

ibid., 49,On

Wertbcimer’sM.

Z.

550-557;

10,

Z.

Psijcm.,Bartley,

esp.

1929,

Brit,

288-305;

J,

Psy-

S,

H,

The relation of retinal 11-442-447;

liuninalioii

to

the

cxpcriuucoofBenussi, 1913, Korte, 1915, DeSilvn,

movement,

1.

exp.

Psychol,

19,

1926, opp.

1936, 475-185.

61.

1913,

cttt. infra,

On the nature of movement, see,On tactual movement, see G. S,

besides Wertheimer. F, L. Dimmick,

Hall and H.

Ansensations

experimental

study

of

visualmovement and the phi phenomenon,
Amer,

J.

Psychol, 81,

1920, 317-

D. Higglnson, The visualapprehension of movement under332; G,

successive retinal

excitations,ihid.,

Dimmick and G.
H. ScahiH, Visual perception of
movement, ibid,, 36, 1925, 412-417.
On hnos of movement, see A.
37, 1928. 63-115;

Klnematoskopische
Untersuchnngen, Z. Psymol, 72, 1915,

Korte,

193-206, esp. 271-296, which showsthat theexposition of

the textismuch simplified. See also F. Cermak and K. Koffka, Untersuchungen
Bewegungs- und VerschmelzungsphBnomene, Psychol Forsch.,

fiber

I,

1921,

66-129a whichdevelops

II. Donaldson, Motor
on tlio skin. Mind, 10,1885, 557-572; M. v. Frey and R.
Motener, Die Raumschwelle der

Flaut bei Successivieizung, Z. Psy-

chol, 29, 1902, 161-182, esp. 179 f.;
V. Benussi, Kinematohaptische Erscheinungen.
29,

1913,

AnalyseArch

385-388;

taktilges,

Psychol,

Versuche zur

erweekter Scheinbe-

wegungen, ibid,, 36, 1916, 59-135;
H. E. Burtt, Tactual illusions of
movement, J. exp. Psychol, 2, 1917,
371-385; A, K. Whitchurch, The illusory perception of movement on
the skin, Amer. I. Psyohol, 32,
1921, 472-489; W. A. Andrews.
Hapttcal illusionsofmovement,
ibid., 33, 1922, 277-284; W, Soholz,
Experimentelle
Untersuchungeneight "parallel laws" of the relation

fiber dieor movement to fusion.

Raumstrecken, die durch Sukzessiv-

phiinomenale Grosse vonNOTES
Diirblclung
wordcii,

219-272;
meiilal

Rciic begienzt

zwoior

Psi/chol,

Fai'sck, 5,1025,

W. S. Hulin, Au experi-

study

movement,of

7,.

apparent

exp.

tactual

Psychol,

10,

1927, 293-320.

607

Psychol,, 2, 1917, 03-75; P. Kester,

Uober LokalLsations- und Bewegungsempiinduiigeii

bei

Geruuschpaaren,

Psychol Forsch,, 8 , 1026, 75-113,
csp.

105-113;A.

Mathiosen,Ap-parent movement in auditory per-On avdltoiy mooettmt, see H, E.

ception, Psychol Monogr., 41, 1931,

move-

no. 4, 74-131; also the experiments

Burtl,

Auditory

illusionsofment—a prebminary study, 7. exp.

where localization dmngos.

chapter 16

CONCERNING SCIENTIFIC PROGRESST T TE comeat last to the conclusion of this book,

Does theVVhistory of science, having no end, have, nevertheless, a

T T

conclusion? Does it teach something? Yes; in exhibiting

the nature of scientific progress,

it

provides an insight into thepresent.

Science is thought. It exists in the minds of scientists. At any mo-ment it consists of what scientists bdieve to bo true, and the best
established facts are, in general, (he oldest ones. Not being philoso-

phy or art, science is controlled by nature, by (lie empirical methods of observation and experiment. Observation and experimentare,however, merely the tools of insight—insight into nature,

we say, having regard to the empirical diaracler of observation.
Scire is, thus, something more (Iran esse. Scieuco is not only objective,

but also personal, depending, asitdocs, onhuman

thought, being limited by tire laws of thought. The psycliologist,

consequently, has a special advantage when he studios the historyof his own sdence, for he is able to perceive how its progress has

been wrought out of thinking, has been achieved, one might almost say, in spite of the limitations of the human mind.

Let us, therefore, seize this opportunity—refeixing for the mostpart to the contents of this book, and less often to the materials of
its predecessor of

1929—to realize how scientific thinking gets on

and what keeps it back—especially what keeps it back. Much canbe said for an effort to understand the nature of scientific progressby an examination of its inhibitors. Someone once remarked thatto comprehend the nature of insight, of correct flunking, one needs
at least to know what prevents it It would be so easy to be right if

one were never wrongl Could Kepler have discovered tlrat whiteis a mixture of colors? If not,why not? Could Haller have discov-ered that the nervous impulse is an electrical wave of negativity?

Why not? Why could not Charles Bell have formulated die resonance theory of hearing? Or could he?
008

'

INHIBITORS
The complete answer to such questions would be another book.
author would have to examine all tlie psychological determi-

Its

nants of scientific thinking on the positive side—tlie occasions fordiscovery, the, insights, the motives— and on the negative side—

the inauspicious moments, the blindnesses, the prejudices.

He

w’ould then disoovei' that he was really writing about every kindof thinking, and that thinking in general can be understood only

when the total peisonality is understoodits wishes—

its motives and drives,and prejudices, its needs and interests. To no undertak-ing of such proportions can we here address ourselves; yet it lies

within reason iiat we should conclude this book with a simple

statement of some of the moie important reasons as to why science
progresses no faster than it does.
1. _Scie niifuiprasresjat .anp point laote on tjig discooerj of In-i

slmmenls^andjechniijues. This limitation, not being psychologi-'
cal, isunderstood by all. Newton would never have discovered

color mixture without a prism. He went to the Stourbridge Fair,bought a prism, and presently knew lliat white is a mixture ofcolors.

Helmholtz would never have formulated the resonancetheory of hearing had not the compound microscope been im-prove enough for Corli to describe ie structure of the inner ear.
It is true that Haller made a guess about resonance before themicroscope was improved, but his guess was wholly wrong. Lacking a good miaxiscope, he lacked facts. Galvani and Volta could
not have told us much about the action potentials in nerves be-cause they had no galvanometers;

du Bois-Reymond did better

widi poor galvanometers, Lucas still better widi a capillary eleo-',ti'ometer, Adrian best of all with the means for amplifying potentials

that the radio provided. Hie scientific workman must have!

tools.
2.

Discoveryis serial,itpresupposes other knowledge. This

limitation on thought is also wdl known. Only because Newton

and Helmholtz had established the laws of color mixture could
Konig show that color blindn«s is best described, without thehazards of introspection, in terms of dichromatic and trichromatic
vision. Bernstein would never have described the nerve impulse

as a wave of electrical negativity had not Galvani first discovered

what he took to be animal electricity and had not Volta then corrected Galvani. Helmholtz, in conceiving the resonance theoryof hearing, depended entirely upon Galileo’s discovery of reso-

010

CONCERNING SaENTIFlC PROGRESS

nance; even Haller could guess about resonance only because
Galileo had preceded him. IIow in lire world could Wertheimer

ever have described the pW-phenomcnon had not Plateau and tlicother's found in tire stroboscope drat seen movemeirt can be createdby discrete displacement of the stimulus? Thought has to build on
something. Ignorance may consti'ain its form but will not fer've fora foimdation.
3.

Insight conforms to the Zeitgeist; onhj rarely does it departwidely pom contemporary thought. Thought, in cralization as in
the individual, is sensibly continuous. While isolated steps of insight may themselves follow an all-or-none law, such quanta are

seldom large. The inertia of tradition is too great for the courseof progi'ess often to be deflected widely and suddenly. It is truethat convention is not so absolute as ignorance in preventing wis-

dom; nevertheless thought is never free from its habits. Consider,for example, the theory of sensory quality. Empedocles believedthat eidola of objects are transmitted by the nerves to the Mind sothat it may perceive tiro objecls by their images. Later there arose

the notion that there arc animal spirits in llie nerves to conduct theeidola. Then, under the influonco ol maleriali.sm, the animal spirits

came to be regarded ns a ols oioo or a vis nrrvnsti. Presently Johannes Mirllcr, seeing that every sensory nerve always produce's its

own quality, substituted lor the vis nervosa five specific nerve
energies. Soon it was seen, however, that Miillcr’s alternative hypothesis, the notion that tire specific energies may lie in the central terminations of Uie nerves, meant nothing more than that thenerves are specific as to their termini. Thus arose the concept of

sensory centers. Now we are beginning to realize tliat the important thing about a center is that it can make certain specific con-nections and not others. Was thei'e anything to prevent Galen or

Haller from conceiving of sensory neural specificities? Only the
habits of thought of their times. Why did Muller prefer to thinkof the energies as more likely to be in the nerves than in the brain,

and why did he call the specificities of the nerves energiesP Because energy is something like a vis nervosa which in turn resembles animal spirits. They are all substantial forces in nerves. It isin the nature of thought to proceed slowly,

There are, of course, notable exceptions, but they are few, The
most original discovery described in this book is Newton’s findingthat white light is a mixture of colors. That idea was simply too

INHIBITORS
silly to seem true,

temerity

611

and Newton at first was made to sufier for his—though the experimental demonstration with the prisms

was so simple and so easy. Not easily do men prefer logic to approbation,
.

4.

.

Ir<4ioiducd thinking also shows its ineiiia; men do not readily

perceive the obvious when it contradicts their habits of thought.

These biases—

forthey are biases

scious. On die unconscious side,—^may be conscioiis or uncon-

we have the persistent failure toappreciate die function of binocular parallax in the perception of
depth. Kepler in 1604 fixed upon the scientists the notion that—a theory

vision is the perception of the retinal image

that wascomfortably consistent with the ancient image theory of perception. The definition of the horopter in 1613 established the conceptof identical retinal points as the reason for singleness of binocularvision. After those events retinal disparity

was described morethan once and explained away by various ingenious logics. No one

was quite able to transcend die established fact of identical points

enough to see that retinal disparity is die reason for binocular perception of depth not for two centuries. Then Wheatstone, aided—

perhaps by current interest in optical magic (the stroboscope, thekaleidoscope), invented the stereoscope. Even he did not at oncesee its full significance, Or consider, in this connection, the para-dox of Gestalt psychology in pressmg its claim that perception
does not mirror the stimulus. The fact is that, for seventy years before

Wertheimer introduced Gestalt psychology to the world,

psychologists had been investigating the differences between per-ception and die stimulus—in die illusions, the constants of psychophysics, Weber’s law, indeed, in everything experimental about
perception. Of course, this aspect of the Gestalt concept was notnew. Yet Gestalt psychology had to fight to get it accepted, allbeoapfe the simpler view^—the views that derive from the oldimage theory of perception, which Johannes Muller loo had fought—persisted along withfacts that contradicted them. Contradiction

does not seriously menace strong habits of thought when theircharacter is not consciously recognized,

On the conscious side, there are aR the clearly held systematic
views, Titchener thought analytically, Under pressure from Gestalt psychology

he shffted from sensations to diinensions for his

ultimates, but he was still making an analysis. He even sought todetermine the color of the pW-phenomenon. Today the positivists

612

CONCERNING SCIENTIFIC PROGRESS

claim to have the fonnulae for reducing consciousness to discrimi-

natoiy response, and sometimes they do it. Yet the dualism of mind

and body, of phenomenal experience and brain, is so well ingrained in conventional thought that not

many follow them,though few refute them. These inertias are conscious and voluntary. Most of the protagonists understand bodi sides, yet each holds

to his own.
5.

Personal attitudes constrain or divert thought. First there are

egoism and the need for prestige. They tend to close the mind incontroversy, a phenomenon which is illustrated in any thorough-going scientific quarrel. Hering quaireled with Helmholtz about
fhe horopter; and, if Helmholtz came off the better, it was only be-cause he was able to see both sides. Wundt quaireled with Stumpf

about die bisection of tonal distances, Wundt loaiiiig through hismajesty and Stumpf wrapping his robe ol musical sophistication
firmly about him. Even tho nativists quarreled with the emphicists,

aldiough, as we have seen, every nativist was something of anempiricist, every empiricist something of a nativist.

Not distinct from egoism is tho need ior self-consistency. Everyquan-el shows that too. When a man takes up a position, his prideprevents retraction, Galvani bad said that tho frogs’ logs move by

animal electricity and was in no frame of mind to accept Volta’s
belief that the leg was simply the cell of a battery. Psychology,

moreover, grew up in Germany where every Gelehrler was fully
entitled to defend liis past commitments. Sometimes it is not re-spectable to be right if you have to change your mind out loud.
6.

Social atlitudes also constredn thought. Here we have the in-fluence of the schools, the need for men to stand together. The in-group magnify their agreements and rise to repel, or at least to
depreciate, the out-group. Gall must have prevented the exact
localization of brain function for years because everyone amongthe ‘propej! scientists was against his exact localizations. Similarly
the psychologists of 1880-1910 wasted no end of time in proving

they were scientific, all because they were fitting philosophy.

Within the school agreement is facilitated. Wundt’s students confirmed the tridimensional theory of feeling; others did not. Wurz-

burg never found images for thought; Cornell did. Is feeling a sensation or not? Laboratory atmosphere largely determinedwhat

would be found in answer to that question, and laboratory atmosphere often extended from a parent laboratory to its offspring.

FACIUTATORS

613

Psychical acts belong to soulhem Germany; contents to northern;

whereas mind that is of use to the organism is American. These
matters need to be worked out more thoroughly, but there can be

no doubt that within the Zeitgeist there are local Geister which determine what theory you shall apply to your experimental findings
di evenliow you shall record your data.
It would be easy

now to end with a moral, to suggest that sciencewould get along faster if the scientists knew their history andcould, by that insight, overcome dreir inertias, egoisms, prejudicesand needs for self-consistency. Such a conclusion would, however,be much too simple. Even if these consbaints to progress could be

removed by die mere act of insight into their nature, the result
might not be a quickening of the scientific pace. Science has perpetually to contend against its own ignorance by honest hard work.

The psychological forces that block or misdirect its progress also
drive it; and all these negatives have their positives. Tlio obverseof the Zeitgeist as inhibitor isknowledge of contemporary re-search. Tlie investigaloi'’s power is increased if be works with thelimes. The obverse of individual inertia is personal integrity.

We

have a right to expect that a colleague will not think one thing on

Monday and another on Wednesday—at least not every Monday
and every Woduesday. The obverse of egoism is pride—pride oftechnique, pride of observation, pride of logic, pride of insight,

pride of achievement. What other guarantee have we of integrityp

Tho obverse of social constraint is loyalty—loyally to colleagues,
capacity for cooperation, generosity of private information. Before

we take science away from men and put it in the hands of impersonal robots, we had better know what sort of personalities wewant to give the robots.
Yet a knowledge of tlie history of science is important. It gives
perspective. It aids humility. It exhibits the kinds of errors that can

be avoided. It even saves tho trouble of discovering the same fact
twice. If scientists need to compute errors of observation and to
determine the constants of their instruments, then they should re-member farther that the primary instrument of all science, thehuman mind, also has its errors and its constants of which theyneed to be aware and to beware. The history of science can teach—them that.

INDEX OF NAMES
The impoiiant item ore given jirsi. Incidental mentions of a name arelabelled 'wc." and given second, Citations of the literature are labelled“ref." and ghen third.

When there are more than four important subjects, therj

ore heyed by subject, No "inc." item is induded when there is an important
subject-item or a “ref," item for the same page.

Abbott, E., 498, 500; ref,, 519

Arrhenius, S. A., 455

Abney, W.deW., ref., 196

Asher, L., ref., 51, 460

Abrahams, H., rrf., 401

Anbert, H., 139, 160-3, 172, 174, 207;

Addame, R., 591; ref., 605

inc., 178,

Ades, H. W., ref,, 95

ref.,Adrian, E. D., refractory period, 59 f.;

809, 517, 568

or none, 60 f.; action poten-

Auerbaeh,tials, 05 f.; frequency tlieory, 08;

896 f.

all

193, 204 f,, 240, 484;

153, 191, 193-5, 218, 260,

F.,

244, 884;

ref.,

261,

cochlear response, 432
inc., 214, 389, 419, 421, 009
ref., 91-3, 95,

Bach, J.S., 318

435

Agalharcos, inc., 205

Bacon, R,, 98

Agullonlus, F„ 79, 226, 228, 271 , 284;

Rain, A., 8, 86, 382 f., 545; inc., 528;

inc,, 157; ref., 257, 305,

Aitken,

J.,

inc,,

Albinus, seeJ,

308104; ref., 191

ref., 05, 566,

Baird, J.

193, 305, 307

P. Lob6

Alcmacon, inc,, 400
Alexander, G,, inc., 543; ref., 570

Alhazen, 98, 222; inc., 155, 165, 192,

207; ref,, 121
Alrutz, S., 504-9, 511; inc,, 493; ref.,

520

570

W„ 281 f,; too., 174 f,; ref.,Baley, S., 304; ref., 394

aerU.,ref.,307
ier, E.,

553; ref., 571

Bomboldt, $. E., 499; ref., 519
Barrow, J., too., 101
Barth, W., inc., 484, 486; ref., 517

Alspach, £. M., ref., 151

Bartley, S. H., ref,, 005 f.

Alston, J, H„ 508; ref,, 521

Bastian, C., 525, 585; he., 528; ref.,565 f.

Anaxagoras, inc., 265

Andrews, W. A., 600; ref,, 606

Bates, W. H., ref., 306

Angelico, Fra, 205

Beaumont, W., 551, 555, 557 f,; ref.,572

Angelll F., 343; ref,, 350

Ansbaclrer, H., ref., 262

Beaunis, H., ref., 567

Appmm, A., 328, 334 f.

Beoher, E., 548; ref., 571

Arago, D. F. J., inc,, 137; ref., 152

Beguelin, N. de, inc., 156

Arcnimedcs, inc., 86

Bffisy, G. V., 305, 429-81; ref., 894,

436

Aristotle, 321, 465, 525; inc., 5, 8, 122,

155 f., 165, 192, 308, 313, 449,

BeD, C., Bell-Magendie law, 63; spedfio energies, 70; cochlea, 402 f .,463

405; taste organs, 451; muscle

Aristoxenos, 315, 318

sense, 525-7

Amheim, F., ref., 398
Aronsohn, E., 441, 443; ref., 459«

inc,, 3, 8, 93, 439, 450, 531, 608
ref., 46, 92, 94,

Aner, M., 281

615

432, 461, 565

INDEX OF NAMES

616

M,, 130, 499, .509-11; inc.,
307|ief„ 151,510,521

Beiilley,

Benussi, V., 6961., 0001.; rel., 602.

51,5-7,

505,

!571,

573,

Boring, L. D., ref,, 603

Bougner, P., 136 1.; inc., 34, 38, 290,

606
Berkeley, G., empiricism, 5 f.; perception,

433-5,

0021.

15;

apparent

size,

2231.;

retinal inversion, 224 f.; percep-

Hon as inference. 263; aerial perspective, 267; convergence, 272,

accommodation, 273; kinestliesis,

ref,, 152, 309•*

Bourdon, B., icf., 604 f.
Bowditch, If. P., 60, 592 f.;Aio., 419;
ref., 92, 605
Boyle, a, 322; ino,. 155 1.. 158; ref,,121 f., 347
Braailadl, L. II., 562 f.; ref., 573

524
inc., 19, 28, 122, 298, 382, 520, 575

Bravo. J., 453; ref., 461

ref., 45, 257, 305, 602

Bray, C, W., 419-23; too., 65 f,; ref.,Bernard, C., 559; r^., 572

93, 435

Bernstein, J,, 58 f., 62, 80-2; me., 60;
ref., 92, 95

Brentnno,
380;

F, 130 f., 208, 245, 378,
inc,, 16.

29. 47; lef., 151,

201, 390

Berschansky, I., 510; ref., 521
Beryl, F., 297; ref., 310

Broil,, G, S., ref., 49

Bezold, W. V.. 132, 333, 410; ref,, 151,

Brener, I., 387, 537, 540-2; inc., 483,

433

53^ rel., 398, 569

Bichat, M. F. X., 526; ref., 505

Brewster, D., 150, 286 f,;

Bidder, F., 560; inc., 430, 450; ret.,

458, 460, 573

199, 268;

ret..

122,

inc.,

131,

150, 190,,3071,

Biddulph, a. 340-2, 346; ref., 349

Bridgman, P, W., 12i,; roI„ 46

Bicdermann, Vi., 495 f.; ref., 518
Bigelow, J., rot., 191

Broca, a, 75; rel., 9.i
ref.,Bitch, T,. ref,, 123

Drodlnm, E„ 189; too., 145;
158 f.
Bronfc, D, W., 422; rol., 435

Bishop, G.H., ret,, 95

Brown, A, Crum,too.,

Biol,J, B„ 333f,;tef., 348

Blanchard, J., inc,, 189; ref., 153
Bliit,

M„ 407 f.; too., 463; ref., 513.5.37,

540-2;

463, 585; ref,, 509

Blake, C. J., too., 335f.

Bloch, E.. 385, 387; ref., 398

Blumenfeld, W., 296; ref., 308, 310
Boerhaave, H,, ref., 91
Bottoher, A., 537, 541; ref., 570

Bois-Reymond, E, du. 57 f.; too., 56,
78, 009; ref,, 91 f,
Bddirefl, W, N„ 555; ref.. 572
Boll,F.. 205; ref,. 218

Bolton, T. L,, 583-6; ref., 604

Boltzmann, L,, 336; ref., 348
Bonnet, C., 7; ret., 45
Borelli, G. A., 54, 322; ref., 91

Boring, E. G,, attributes, 26; massed
pitch, 304; tonal brightness, 378;

auditory boalizntion, 390; Head's

474 f,; visceral sensa549 f,, 562-4; thirst, 5^,

Brown, I, F. 599; rd., 606
Brown, T,, 7. 14, 526, 575; too., 28,
30;rof,, 461,, 565,002
Brown, Wnnier, 40; ref., 51
Brown-Sdquard, C. E., 637; ref,, .569
Bnioke, E., 132, 287; ref., 151, 308
Briicknei, A., 499; lef., 519
Brues, A. M., 362; ref., 394
Bnmn, A. v,, 440; ref., 458
Brmrot, C,, M4; ref., 261
Biunswik, E., 250, 298 f., 301, 303;
ref., 202, 311
Brush, E. N,. ref,. 603
Bryan, W. L., too., 23
Bimer, K,, toe., 135; ref., 152
Buffon, G, L, L., 155 f., 158 f.; too.,
165, 192; ref,, 190

theory,Builendiik, F. J, J., 65, 420; ref., 93,

tion,

435
BuD, 0„ 174 f.; ref., 104563
too., 66
ref., 46-52, 91-6, 123 f .. 152, 261 f,.

Slot. 349-51, 394, 398, 398,

Burch, G, J,, 69, 164; ref,, 02, 191
Burmester, E., ref., 260

Bumell, N. C., 508; ref., 521

.

INDEX OF NAMES
Bumoy, C., rof., 348

Crozier,

Burow, C. A., 274; inc., 119; ret.. 124,
306
Burtt, H. E., 600 f.; ref., 606 f.
Busch, W., 551 f.; ref., 571

617

W. J., too., 440, 450; ref.,458, 460
Culler, E. A., 82. 426; ref,, 95, 436

Cntolo.F.,507f.;rot..S21
Cuvier, G. L. C. F. D., too., 74

Cyon, E., 537, 541 f.; too., 544; ref.,569
Czermak, J. N., 477, 479 f., 577; ref.,Caesalpinus of Arezzo, 528

Cagniard do la Tour, C., 328;

ref.,515,517,603

347
Cajori, F., ref., 122, 346

Daedalus, too., 591

Galkina, M. W.. 22 1.; ret., 48

Dallenbaoh. K. M., 507 f.; too., 471;

Cameier, W., 479-81, 485; ref., 516
Campbell, C. J.. inc., 65; ref., 93
Cannon, W. B., 552-8, 580 f„ 563;
ine., 463; rd., 571-3
Carlson, A. J.. 552-7, 562 f.; ret., 571-

3
Carmichael, L., ref., 92, 565

ref., 481,

513 f., 521

Dalton,]., 108, 184 f.; ref., 196

Darwin, C., too., 159, 535
Darwin, E., 535, 554; too., 159; ret.,
568 571
Darwin, R. W., 159, 165 f.; too., 150,
160; ref., 191

Carr. H. A,, ref., 258, 303

Davies, H., too., 44; ref., 62

Carlwrighi, D., rot., 51

Davies, H. M.. 474; ref., 515

Casserio, G„ 400; ref., 431

Davis, II., action potentials, 65; eom-

Cattoll, J. M., 40; ref., 51

binadon tones, 356; cochlear re-

93
McK.,
Corniak, F., rot., 006

putonlials, 423 f.; sHmulation le-

Cliaffec, E, L., rot,, 348, 394

sions, 425-0; theory of hearing,

Catlcll,ref.,Chamborlaiu, E. M., rol., 194

Chapman, D. W., 24; ref., 49

sponse,auditory

422;

430f.
ret., 52. 93, 95, 347-50, 393-5, 397,

Charles II, inc., 100

432, 434-8
DoForest, L., 332

Chaipcnticr, A., 204 1.; ret., 217

Dolabarrc, E. B., ref., 566 f.

Charcot, J. M., hio., 387

actionChevreid, M. E., 167; rof., 192

Deluge, y., rof., 568

Chladni, E. F. F.. 333 f.; too.. 407,

Dolboeuf, J. R. L., 42, 244; too., 37,412; ref., 348
Churcher, B. G., too., 44; ref., 52

45 f.; ref., 50 f., 261
Delezennq, C. £.
339 f.; Inc., 38;

Clarke, H. M., 532; ref., 568

J.,ref., 349

Clay, E. n., 570; ref.. 602

Democritos, 4 f

Cloquet, H., 438 f.; ret., 458

Derbyshire, A. J., 66, 423 f.; ref., 93,

Cobbey, L. W., too,, 511; ref., 521
Coblentz, W. W., ref., 194, 190
Cohen, N, E., 27; ref., 49
Cohn. G., 458 f,; ref., 401
Colo. R. V,. ref., 303
Collins, M„ref., 196, 216
Collins, R.,385; ret,, 397 1.

Condillac, E. B. de, 7; ref., 45

Coak,F.. 548t,;ref,, 571
Cooper, A., too., 401; ret., 431

435 £,
Descartes, R., sensationism, 7; animal
spirits,

54;

light,

98 f.;

Interactionism,
color,

image, 100, 223; convergence,

271 1 .; accommodation, 21s, 277;
harmonics, 324; kinesthesis, 524
too., 28, 63, 95, 101, 221, 272, 526
ref,, 45. 91, 121, 257, 305 f.
DoSilva, II. R., 59^8; trf., 600

Cornelius, H., 17; ref., 47

Despretz, C., 333 f.

Cord, A., too., 404, 406, 609; ref., 432
Cramer, A., 277 ret., 306 f.

Dessoir, M., 502; ref., 520

Dowey, J., too., 5^4

Crew, H., ref., 122 f.
Crowe, S. J., 425 f.; ref., 436

DeWitt, L. M., 531; ref., 567
Didymos, 316-8;

85;100; retinal

INDEX OF NAMES

618

201 {.; Inc.,
142; ref., ISl, 154, 107, 217
Dietze, G., 584; rd., 604
Dlmmick, F. L., 134, 503, 597 £.; ref.,152,460,520, 606
Dixon, E. T., ref., 307
Dobrowolaky, W., 129 1.; inc., 178;
Dieterici, C., ISO, 187,

151, 195

ref.,

Dodge, R., 496 f., 543 f.; inc., 535;
ref., 519, 570
Donaldson, H. II., 467, 471, 599; ref.,514, 606
Donders, F. C., primary yellow, 129;

W, D., ref., 261 f.
Emerson, W. B., rof., 194, 190
Enunert, E., 292; ref., 310
Empedocles, 4, 84. 400; inc., 610
Epicuros, 5Erasistratos, S3 f.; inc., 63
Erb, W. H., 407
Erlanger,77; ref., 95
J,,
Estel, V., 570 f.; ref., 603
Ellis,

Euclid, optics, 97; apparent size, 223;

convergence, 271; binocular parallax, 282; visual angle, 290;

268

color blindness, 203; color evolu-inc.,

tion. 211; central color processes,

ref., 307,309

212-4; Donders’ law, 230-2; ac-

Euler, L., inc., 287

commodation, 275: vowels, 3702

Eustachio, B., 400; ref., 431

inc.,173, 210, 216, 220, 442

ref,,08, 150, 217, 219, 258, 306,

395
Dove, H. W., 288; inc,, 178; ret., 195,
304, 308
Drobisoli, M. W., inc., 897
Duchenne de Boulogne, G. A. B.,
532; ref., 567
Duncan, J., ref., 347
Dupuytren, G., 558; ref., 572
Dusser de Baronne, J. G., ref., 588
Duval, 453; ref., 481
Duveiney, G. J., inc., 400; ref., 431
Dvorak, V., 5021.;

inc.,

596;

ref.,

605 f,

mu-316

sical scale,

Ewald, E., ref., 218
Ewald, J. R., 413; inc., 407; ref., 484
Ewert, P. II., 237; rot., 259
Exner, S., 163 1., 363, 594, 600; inc.,590; ref., 191 f., 304, 605 f,

Faraday, M., 589 f.; Ino., 58; ref., 605
Fearing, F., lof., 01

Fechner, G. T., ptwcbopbysics, 84-45;
pariillelisni,

87 f.; cxperimcntal-

ism, 1 17; cloud e)q)aiiment, 137;

ntlcr-image, 1591,; size and distance. 291; two-potal limen, 480;

thermal J.n.d., 497 f.; kinestbosis,

529
ino., 10, 55, 68, 89, 95,

116, 120,

132, 136, 189, 220, 342, 350 1.,

Ebbinghaus, H., 148 f., 417 f.; inc.,
130, 150; ref,, 151, 153 f., 219,

434
Ebert, H., ref., 195

Edehaann, M. T., inc., 335
Edison, T. A.,^1; inc., 330, 369,

395, 595

Edmonds, E, M., 362; ref., 394
Edridge-Green, F. W., inc., 210, 216;
ref.,

219

Ebrenfels, C, v., 10 f., 246, 254; inc,,503; ref., 47, 80S
Einthoven, W., 244; ref., 281
Eisler, R., ref., 05

Eissler, E., ref.,262

EkdaH, A, G„ 384; ref., 394
Elliott,J.,

Elliott, M.
Ellis,

inc.,308

H„ ref., 572

A. J„.320; ref., 346

501, 577
rof., 50 f., 153, 191, 309, 350, 519
Femberger, S. W,, 40; rof., 51
Ferrall,?, C„ 507; ref., 521
Ferree, C. E., 175 f., 385; ref., 193 f .,397 f.
Feirier, D., 75; inc., 528; ref., 95, 566
Fick, A., ref,, 513
Finch, G., ref., 436
Findley, A. E,, ref., 460
Firestone, F. A., inc., 44; ref,, 52
Fischer, E., 442; ref., 459
Fisher, S. C,, ref,, 568
Fleming, J. A,, 331
Fletcher,H.,

337 f.;
thermalauditoryaural
noise,

sensitivity,

harmonics,
365;

359;

masking,

387; vowels, 375; pitch in cochlea,

428

INDEX OF NAMES
inc.,

44, 430

ref..

52,

Flourena,

619

Galileo Galilei, 98, 323 f., 378; ino.,

348 f., 393-6, 436

26, 97 f.. 319, 322, 328, 332, 347,

M. J. P,, 74-3, 403, 405,

409, 609 f.; ref., 346

536 f.i inc., 80, 386, 535, 540;
432, 568 f.

ref., 94,

Gall, F. T., 74 f.; inc., 257, 612; ref.,94

Foorster, R.| ref., 309

Galton,Fclio, 0^400; ref., 431F.,

335 f.;

460;

inc.,

ref.,

348

Forbes, A., 65-7, 420; inc., 214, 419,

Galvani, L., 55-7; inc., 64, 609, 612;

421, 423; ref., 91. 93. 435
Foster, M;, ref., 91

Gamble, E. A. McG., 443; ref., 459

ref.,Foucault, M., 481; inc., 480;ref.,

515 f.

Gassendi, P, 322; ref., 347 f.
Gasser. H. 8., 77; ref., 95

Fourcroy, A. F. de, 444; ref., 459

325 f.; ino., 327 f.;
J.,

Fourier, J. B.

347

ref.,

91

Gates, E. J., 134, 481; inc., 21; ref.,152, 516

Gatti.A., 496 f.; ref., 519

P H., inc,, 44; ref., 52

Francesca, F. della, 265

Geiger,Frank, H., ref., 309 f.

898
George I, inc,, 319
Gertz, E., 500; ret., 519
Gibson, J. J., 238; ref., 260
Gilbert, G. M., ref., 602
Gilbert, W., 55
Gloss, R., 580; ref., 603
Gllsson, F,, 54f.i ref., 91
Gelid, 387; ref.,Franke, G., 440; ref., 458
Franklin, B., 55, 158; ref., 190

Franz, S. I., 78; ino., 94

Fraunhofer,v„ 108, 128, 177 f.;

J.

inc., 34,

127; ref., 150, 194

Freeman, E., ref,, 810
Freeman, G. L., ref., 521
Fresno, R, du, ref., 308
Frey,

Godart,do,ino.. 156, 158

M. v., taolual senses, 488-71,

475; Hoad's dioory, 474 1.; twopoint limen, 479, 483 f.; pressure
stimulus, 487-90; thermal stimulatlon, 482 f., 504 f.; pain stimu-

493 f.; heat, SOS, Sll;tactual movement, 600
ino,, 142, 483, 498, 499, 501 f.,
504, 515, 524
ref,, 154, 514, 513-20, 606
FriedW, G. L., 482; ref., 516
Fritsoh, G„ 75; ref., 94
Frobes, J., ref., 348, 603
Fty,H. S.. 388; ref., 398
Fubini, S., 559; ref., 572 f.
lation.

Fullerton, G. S., 40; ref., 51

Fulton,F..

J.

531; ref,. 91{.. 95.

566-8
Funke, 0,, 466 f ., 502; ref., 46, 513

GSbel, 0., rel., 434

Goethe, J. W., 112-6, 128;

ino.,

28,

32, 117-9, 122, 125, 181, 159,

166,

184,

ref.,

123 f.

190, 206, 208, 361;

G6lz, W,. 296; ref., 310
Goldsolreider. A., skin spots, 467-71;

two-pointaslimen,

summation,

479;

499;

pain
after-

502 f.; paradoxical
warmth, 506 f.; kinesthesis, 5302
ino., 463, 494, 523
ref., 514 f., 520 f., 567
Golgi, C., 581; ref., 567
Goltz, F. L., 75 f., 537-41; ref,. 95.
569
Goodale, H., ref., 518 f,
sensations,

Gotch, F., 59; inc., 64; ref., 92
GraiUch, J.. inc., 178; ref., 195

Gad, J.. inc., 602; ref,, 514, 520
Gaglio, G., inc., 543; ref., 570

Galen,

C.,

animalspirits,

53 f.;(diiasma, 79; optic decussadon,227;

binocular

labyrinth, 400
ino., 63. 272, 810
ref.,257, 307, 431

parallax,

233;

Grassmarm, H., 87 f., 141-3, 200; iito.,
89; ref., 96, 154
Gray, A. A.. 408-9; ino., 411, 431;
ref., 432-4
Gregersen, M. I., ref., 573

Gregg, A,, 67; inc, 66, 214, 419, 423;
rd., 93, 435
Griesba^, H., 481; ref., 516

INDEX OF NAMES

620
Griffith,

C. R„ S43f., 564; inc,, 535;

Ifcgg, E., iuc., 174 f.; ref., 194

568, 570. 573

Ilcideiich, F., ref., 461

ref..

Grimaldi, F. M., 98. 101; lof., 121

Helmliollz,II.,modality, 10; empir-

Guericke, 0. v.. 55, 321; ref., 347

icism, 31, 233 f.. 237; velocity of

Guild, S. R.. 425 f.; ref., 436

nerve, 58; spcoiHc energies, 78;

Guilford, J. P., 599; ino., 37; ref,, 51,

expciimenlalisni,

603

120; vi-

117,

Guillaume, P., ret., 282

119; primary colors, 128;
Bezold-Driioko
phenomenon,

Guthrie, F.. 3i30

131 i.;

sion,

Weber’s

137 f.;

law.

color mixture, 140-5; -color tri-

Hacker, F., ino., 506; ref., 521

angle,

Haegqvist, G., ino., 471; ref., 514

HsBstrdm, G.
ref,,

G.,

853 f.;

inc.,

357;

392 f.

147;

after-image,159;

contrast, 167; color zones, 173 f.;color blindness, 183, 185 f.; color

200-3;

tlieory,

apparent

size,

Hanig, D. P., 452; inc., 454; ref., 461

224;

Hall, G. S.. 583, 586, 592 f.. 599; ino.,

240 f., 243; constancy, 255; per-514; ref., 50. 605 f,
Haller, A.

v.,velocity of nerve, 58;

animal spirits, 62 {.; natural stim71; accommodation, 275;

ulus,

horopter, 229 f.;

illusion,

ception as inference, 264; par-movement, 267 f,; acoommodatinn, 273, 275-9; stereallax ofoscopy, 287; perception as judg-

anatomy of ear, 400-2; smell
classes, 444 f,; taste, 449 f.; tastemeul,

qualities, 453; internal sensibil-

hearing, 354; number of pilohos,

hunger, 551, 553-5;

341 f.; comblnnUmi tones, 354-

ity.

545;

tliirst,558

inc., 8, 91,405, 439, 608-10

ref., 46. 94. 308, 431, 458-81. 570-2

280;liming-foilcs,

0;beats,

aural

325;

hiinni>nio.s,

3.30 1.;

3.55 f.;barmmiics,

limitstimbre,
8.50;

of

358;

eonso-

nance, 350 f.; nolso, 363 f,; vow-

Halley, E., ino., 165, 192

ols,

Halverson, H, M., 25, 379; ref., 396

382, 888 f.; tbeoi-y ol bearing,Ham, L. B., ino., 43; ref., 52404-11; sonsalions of lunervu-

Hamilton, W., 528, 528, 645; ref., 48,

tinn,565, 570

Hardy, J.D.. 494, 499; ref., 518 f.
Harless, C,, ino., 537; ref., 569
Harris,J.,285; ref., 308

Hartl^. D., 6, 85, 227; inc.. 8 f.. 95;

367-78; piirccption of pluiso,

aftCT-sonaoUun
525;
movoraonl, 692
ino., 9, 28, 64, 67. 78.

of

87 f.. 110,

112 f., 120, 132 f., 130, 157,160,
103, 165, 170 f,. 185, 187-9, 101,
193, 199, 207, 210 f,, 230, 204,

257
Hartmann, G. W., ref., 49, 201
Hartridge, H., inc., 411; ref., 434
Hartshome, C., ref., 49
Haunt, I. A., raf., 198 f.
Hawkins. J., ref.. 346
Hayoraft, J. B,, 441, 447 f., 455; inc.,
439, 450; ref., 458, 460 f.
Hayes. M, H, S,, 503; rrf., 520

Kelson, H., 253, 599; ref., 202. 600

Hayes, S. P., inc., 189; ref., 197

Henning, H., smell stimulation, 444;

ref., 45,

Head, H., 471-4, 484. 524, 548; ino.,
403, 476, 480, 494. 498; ref.,515, 565, 571
Hecht, S., 181 f,, 215 f.; ref,, 190, 217

Heennann, inc., 119; ref., 124
Hegel, G. W, F., inc., 248
Hegdinaier, F., inc., 40; ref., 51272. 297, 302, 312, 320, 327,
345, 353, 357, 381, 391,
399-401, 417 f., 437, 449, 454,
829,

467, 528, 590, 609, 612
ref., 46. 49 f.. 92,94,1231, 150 £.,153 £., 190, 192, 218 f., 237-62,
304-8, 346-9, 393-5, 432. 434,
566, 604 f.

smell classes, 445 f.; smell chemistry, 448 1.; taste qualities, 455;

taste diemistry, 457
inc.,

439

ref., 458-61

Henri, V., 479-81, 484, 486; ref., 258,515-7, 584 f.

.

INDEX OF NAMES
Hensen, V., 406j inc., 404 f.j ref., 394,

432,434

Hobbes, T„ 5; inc,, 28, 575; ref,, 45,602

Ileraclitos, 4Herbart, T. F., 35; lnc„ 16, 258, 604;
lef.,

50

Ilonigschmied,

J,,

458

Hbring, A,, 578; ref,, 603

llerbst, C.| tcf., 566,

621

tloagland, II., ref., 93, 153, 603

Holaday, B,

HeruiF^^E., nativism, 29, 233, 286 1.;E.,

298 f.;

ref,,pnenomenology, 33, 117, 120;

Holland, R,T,, 504; ref,, 520

adei^uate atiinulus, 71; isomorhi^m, 88 f ,; primary colors, 126;

Holmes, 0,

ght sense, 132 f.; after-imago,
159; adaptation, 161 f,, 164; con-167 f.; color zones, 173-5;
Furkinje phenomenon, 181 f.;
trast,

color blindness, 183; color theory,

208 f.;

color

210 f.;

horopter,signs,

235 f.;

evolution,

229 f.;

illusion,

local

240-2;

constancy, 255; apparent

size,

289; size and distance, 291 {.;tactual senses, 466; thermal stimulation, 491-3; thermal adaptation, 500

74, 118, 128, 135, 160,

inc., 4, 28,262,

310 f.

W„ 287; ref,, 307

Holmpen, F., 188; ref., 197
Holt, E, B.. 131; inc., 12; ref., 151

Holway, A. H., 458; ino., 443; ref.,153, 310, 350, 459, 462, 519
Home, E., 276; ref., 308
Honzik, C. H., 557; ref., 572
Hooke, R., 101, 324, 328; inc., 102;
ref., 121
Horn, W., 451; inc,, 450; ref., 461
Hornbost^ E. M. v., 27, 389 f.; inc.,
601; ref., 49, 398
Homer, W, G., 590 f.; ref., 605
Huber, G. C,, 531; ref., 587
Huddart, J., 183; rof., 196
Ifulin,W.S., 6001,; ret,, 607

167, 172, 187-9, 207, 214, 216,

Hinnboldt, A. v., inc., 92

22H., 230, 280, 293 f., 449, 495,
612

Hume, D., 6, 86; inc., 19, 527, 575;
45, 602ref.,49,04, 96, 125, 150-2,1911.,

Hunter,],, 276 1.; rof., 306

195, 218, 258-60, 262, 307, 309,

Hunter, W, S., 76; ino., 12513, 518 f.

Hurst, C. H., 416; ref., 434

ret.,Herlilzka, A,, 454; ref., 461

Hurvich, L, M,, 458; ref., 462

443 f.; ref., 456
Hermann, L., 368, 370, 372 f.; inc,

Husserl, E. G., inc., 248

Hermanidcs,

450; ref., 46, 94, 309, 395, 458,

460 f,, 513,518
F. W., 185; ino., 153,
J.
188, 197; ref,, 197
Hertz, A. F., 548 f.; ref., 571
Herzen, A., 467; rrf., 513
Hersohel,Hess, C., 129, 168 f.; inc,, 164, 175;
ref., 150,

192-4

H.F. T.,inc., 166; ref., 192
ref.,

604,

280-2, 294 f,;

ref.,

606
HiUebrand,

F.,

Hykes, 0. V., ref., 124

Ibn al Haitham, ref., 121
Ishihara, S., 187
Jacobson, E., ref., 568
Jnensch, E.

378;

Heuschke, inc., 217
Heymans, G., 243 f.; ref., 261
Higginson, G. D., 597-9;

Huygens, C., 54, 98. 108; ref., 121

307,310
Hilton, J., 547; ref., 571

R„ 249, 884, 870, 378,

ino.,

418;

ref.,

261, 310,

394 f., 434
James, W,, 44, 85, 542, 575 f,; ino.,
193, 528 f„ 580, 592 f.; ref., 49,
52, 95, 259, 565 f, 570, 802-5
Jastrow, J., 40; ref., 51
Jeffries, B. J., ref., 197
Jenkins,

W. L., 493, 500, 508; ref.,518 f., 521

Hippel,A, v„ 186; ref., 197
Hire, P. de k, 274; ref., 805

Jones, A. T., ref., 392

Hirschberg, J., ref,, 309

Joule, J. P., 86; lef., 96

Hitzig,E,,75f.,538;ref.,94,569

Jurin, J., 158 f.; ref., 190

Jones, L. A., 180; ref., 151

INDEX OF NAMES
EfimpEe, B.. 343; ref,, 3S0

ino., 11, 120, 142, 144, 149, 210,

609

Kohlenberg, L., 456; ref,, 461

Kame;, Lord, Inc,, 190
Kammler, A,, 484; ref,, 517
Kant, I,, 233 f,; ino,, 281,. 221, 248,
578
Kast, L,, 548; ref., 571
Koto, G,, 60
Katz. D.. 135, 249, 255, 512; inc.,251, 298; ref., 152, 281 f„ 622

ref., 151,

153 1., 190, 195-7, 217-9

Koenig, H., 319 f., 328-32, 334 1., 358,
370, 372-4; inc., 357 f.; ref.. 347,

392 f,. 395
Koffka, K., 300-2, 584, 596; tae,, 13.
152, 170, 250, 252 f,; ret,, 47 f..’96, 152, 193, 262, 308, 310, 604,

608

Keith, A,, ref,, 432

Kollert,Kelvin, Lord, 88; ino., 327, 347; ref.,Korto, A., 596-8; inc., 601; ref., 606J.,

579 f.; ref,, 603

Koster, W., 181; ref., 195

98

Kemp, E. H., 425; ref., 433, 438
Kemp, W., ref., 394

Kottenlcamp, R.. 479, 481, 484 f,, 502;

Kempclen, W. de. 369, 371; ref., 395

ref., 516, 520
Krnhauer, D., ref., 461

Kenkel,F.,598f.;ref..808

Kratzenstein, G. G., inc., 156

projection, 80, 227; optics,

Kepler,98 f.;

image,

relinol

98-100,222-4; retinal inversion, 224 f.;

accommodation, 273, 276 f.
inc,, 97,

Kries, J. V., 130, 180 f ., 188-90, 203-8,
tei., 49.

151, 154, 195, 197, 216,

218,258,3971.

121, 257, 306

KrSncr, E., rot., 567

Kesler, P., 601; ref., 807

Kronocker, 11., 59; rof., 92

Kiesow, F., 452, 454, 487, 490, 496 f.;inc.,

Kreidl, A.. 542; ref., 570

884, 387; ino,, ,50, 142, 210, 364;

122, 155, 237, 272, 274,

608, 611
ref..

Krause, W., 451; rof„ 481

450. 501, 508;

ref.,4801.,

517-21K6hno, W„ 205, 530; inc,, 527; rof.,
196, 21 8, ,505 1.
Kiilpe, 0., number of sonsullons, 10;

Hnoaid, M., 480; ref., 516

aliribulos, 11, 20-4, 375; empir-

King, A. T., inc., 44; rd., 52

icism, 31 f.; psychophysics, 44;

Kirdier.A,, 157, 321 f.; ref., 190

number of colors, 130; nativism,233 f.; local signs, 236; phenomenology, 246; number of pitches,
342; noise, 364

Kirscbmann, A., 189 f.; ref., 193
Klenun, 0.,389f.;ref.,49. 398
KUmpfinger, S., ref., 262
Knight, L.. 508; ino,, 511; ref,, 521

Knudaen, V. 0., 344 f.; rrf., 349 f.
Kohler, W., projection, 83; isomor-

phism, 84,
252;

303; field theory,transposition,

255;

size

constancy, 298; vowels, 370, 372-

inc., 3, 17, 23,

28, 30, 38, 47, 87,

133, 193, 379, 533
rof,,

46, 48-50,

151, 2581,, 349,

393, 398
Kuile, E. ter, 418 f.; ref., 434

Kundt, A., 320; inc., 240; ref., 260

4; tonal attributes. 376, 378, 380;

theory of hearing, 408; apparent

movement, 599

LBborde,J.V.,388;ref.,398

598
ref,, 47 f., 96. 280 f.. 810 f., 395-7,
433,606inc,,

13, 250, 253,

KoUiker, A., 203, 530; inc., 404; ref.,217, 566 f.

LBdd,G. T.. ino., 94, 193; ref., 570
Ladd-Franidin,
inc.,

C.,

129-31,210 f.;

145, 204; ref., iSOf., 216,

219
Lagrange, }. L., ref., 392

KiSnie, A., color j.n.d., 130;

Weber’s

Laird, D. A., inc., 43; ref., 52

law, 138 f., color triangle, 147;
luminosity curve, 179-82; color

Lambert, J. H.. 144, 148; ref., 154odor theory,
201 f.; visual purple, 204

Landolt, E., 172; ref., 194

blindness,

1877,;La Mettrle, J. 0. de, 7; ref., 45
Landry, 0., 528; ref., 566

INDEX OF NAMES
Lane, C. E., 359. 306 f., <127-9; Inc,

395;rer„393f,436

238; ideomotor action, 529

Lange, G. G, Inc, 570
Lange, N, 271; rof, 305

inc.,

Itfef,

Lov4n, C,, 450 f.; ref., 460
Lucas, K., 59-61; inc., 419, 609; ref.,Lashley, K. S, 76 f.; ino, 12; ref, 94
244; ref., 261
Leewenhoek, A. v., inc., 217

Liska,

Lneiani, L..

W, 85; ine, 28, 35. 50,

Leibnitz. G.

95
Lennandcr, K. G., 547 f.; ref., 571

Leonardo da Vinci, contrast, 185; colored shadows, 166; eye as camera, 222; light and shade, 266;
aerial petspeetlvo,

260; binoc-

ular parallax, 283 f.
981,,

91 f.

Luce, A., 562 f,; ref., 573

Lehmann, A., 168, 410; inc., 407; ret,
192 f, 433 f.
Lehmann, T. G., ref., 566

155 f., 192, 206, 208,

268, 303

ref.,

513,

Macdonald, M. K., ref., 460
MacDougall, R., 585 f,; ref., 604
Mach, E., positivism, 12; isomorphism, 88 f.; color theory, 206 f.jcolor processes, 212-4;

ref.,ness. 378; theory of hearing, 408;

vestibular

inc.,

459,

ref.,

13, 126, 150, 220, 407, 463,

96, 122, 218, 257, 396, 433,

566, 569, 603-5
261,

434

MacLeod, R. B., ref., 152, 262, 604
Magcndie, F., 63, 274, 551 f.; be., 3,
8. 93, 520; ref., 92, 305, 571

Lissajous,A., 320, 330
J.

Listing,

B,, 230-2, 275 f.; ref., 124,

258, 306
Lob4. J. P., 276; ref., 306

Locke, J., 5, 69, 238, 490, 500; inc.,,19, 28. 84 f., 158, 190, 198, 221,

466, 492, 527, 575; ref., 45. 257,

Malebranohe, N., ino., 267
Mahnud, R. 8., ref., 521

Mandelstamm, E., 129; ref., 150 f.
Marbe, K., 271, 593; ref., 305, 604 f.
Marey, E. J., 59; ref., 92
Mariotte, E., ino., 155, 171; ref., 121
Marloye, 319, 329

518, 602
Lowenberg, A., 538
Lbwit, 495 f,; ref., 518
Lehmann, W., 162 f.; ref., 191
Longet, F. A., 551 f.; ref., 571
Lorenz, G., 344; ref., 350
Lorry, D.. 444 f .; ret., 459
sensory eontinuum,

lime

after-sensa-

528, 535 f,, 544, 596
ref.,

258;

537-42;576-8;

tion of movement, 592; movement sensation, 593

461
inc.,

sense,

perception,

Linne, K. v., see Linnaeus, K.

R.,76, 94;

Ludwig, C. F. W., 291; ino., 528; ref.,309, 565 f,
Luft,E., 840-2, 345; ref., 349
Lummer, 0., inc., 145; ret., 154
Lurie, M. H„ 426-8; ref., 435 f.

form-qualiW, 255; tonal bright-

Linnaeus, K,, 444, 453;

Lipps, T., 245;

inc.,

518, 664 f.. 570

central304, 308

Lopldi-Chioll, G„ 559; rof., 572 f.
Lewes, G. H., inc., 526; ref., 563
Lowy, W., 486; ref., 517
Lieb,C.W.,S55;rof,. 672
Lillie, R, S., 62; rof,, 92
Linkc, P,, ref., 605

Lotze,

28 f.. 31-3, 38, 72 f,,

526, 580, 604

Langley, S. P., 178 f.; inc., 182; ref,

J,

19,

ref., 46, 50, 98. 259 f., 517,569

Langford,* C. H., ref., 192

rof.,

9,

221, 238, 381, 386, 483, 515,

LangenbeckK M. A, ref, 306

ino.,

623

232; local signs, 234-6; illusion,

Martin, C, L., 557; ref., 572
Martins, G., 293 f.; inc., 299; ref., 810

Masson, V., 137 f.; ref., 152
Mathiesen, A., 601; ref., 607
Mabumoto, M., 385; ref., 398
Matteuccl, C., 57; ri., 91
10;Matthews, B. H. G., 531; inc., 65; tel,,'empiricism. 30, 233. 236 f.; Iso-morphism, 87; eye-movements,

93, 567
Matthews, B., 65; ref., 93

INDEX OF NAMES

624
Maorolycus, F., 532,',

Maxwell,

C,.

J,

reT.,

122, 257

144-6. 185 f.. 201;

139; ref.. 154, 197, 217

toe,.

Mayor, A., 560; ref., S7S
Mayer, A. M.. 365 f.; ine., 895; ref.,394
Mayer, B., 457; ref., 461

120; cortical gray, 133,

vision,213 £.; kinesthetic sot, 532 f.
inc., 37, 42 f.. 87, 135, 182, 210,
216, 220, 247, 249 £., 596
ref., 48, 50 f., 96, 125, 152, 210 f.,
566 f.
Muller, n„ 203; ref., 217

Mayo, H., Inc., 286; ref., 308
MoDonaugh, A. R., ref., 48
McDougau, W., 212, 380, 481 f.; ina.,
210, 216; ref., 219, 396, 516
MoKeag, A, J., ref., 94, 514

Muller, Job., sensation, 8; ifativlsm,
29, 233 f.; nerve impulse, 57;

50,

retinal receptors, 203; retinal in-

McKenariclc,

J.

G.,

410;

ref.,

velocity of norve, 58; speciBc energies, 63, 68, 70-3, 399; experi-mentalism,

117;

vision,118;

432 f.
Meenes, M., 511 f.; ref., 522
Mehner,M..S79f.;rof.,a03

version, 224 f.; horopter, 228-30;

Mdoong, A., 16, 246, 255; ref., 47

ulation, 383; ear, 403; taste, 450;

Meissner, G., 487; ref,, 517

taste adaptation, 457; pain, 467;

Meltzer, S. J., 548; ref., 571

innervation sensations, 528; hun-

Merkel,]..

43,

we-movements, 230; aocommoMtion, 274, 277; auilitoiy stim-

343 f.; liio., 37; ref.,Mersenne, M., 322-4; ine., 357, 409;
rot.,

98,

92,

115-7,

112,

119,

159,

430, 527, 588, 6101.

Molager, W., ref., 304

ref., 46, 49, 91, 94, 124, 190,257-0,

rof.,

516, 606

Meumann, F., 548, 562-4, 581 f,, 584;
ref..

554

160, 191, 190, 217, 402, 404 f„

346

Melller, F. A., ref., 95

Metznor, R., 479, 483 1., 600;

ger,

ine,, 5, 28, 30. 34, 50, 77-80, 84 f.,

51£.. 350

571,873, 603 1.

Meyer, H., 281; Inc., 302; ref., 192,309

305 f.. 307, 432, 480, 566, 670,
572
Miiller,

1 n., 5,53, .560; rof., 571, 673.

Miillci-Lyor, F, G,, 2'lS-5; rc[„ 261

Miiustorborg. II., 27, 387, 581, 588;
ino.,

381, 385; rot,. 49, 308, 603

Moyer, M., 167, 170, 340, 376, 380,

Munk, li., 76 £.; ref., 05413-6; ref., 349, 396, 434

Munson, W. A,, ref., 52

Mill, Jas., 7, 8, 15, 545, 575; ino„ 10,382, 527; ref., 48 £..570, 802
Mill,}. S.. 9. 15, 18; ref., 46 f., 259

Murray, E., 501, 503. 510 f.;
520 £,
Musschenbrook, P, v., 144Miller,D. C., 327, 370. 872; ief„346£.,393f.
MlUer, J. G., ref., 604

Myers, C. S,, 389; ref., 398

MiUer, R, H., 420; ine.. 66; ref., 93,

Nafe, J. P., 403; ref., 518

435
Miner, T. B,. 585 1.; ref., 804
Mitchell, J.F.. ref., 571

Modell.J. D., 370, 374; ref., 395

Nagel, W., 181, 188 f,; ino., 187, 191,
193, 439;

ref.,94, 104-7.-458,

613
Napoleon, inc., 74

Molyneux, W., 22!3-5; ref., 257
Montgomery, M. F., ref., 573
Moore, T, V., 47; ref., 47 f.
More, L.T.. 888; ref,, 122, 398

Natanson, 72; inc., 403; ref., 94

Morgan, C. T., 345; ine., 38; ref., 51,
95, 850

Newman,Mott, F.W., 584; ref., 568

Newton, I,, ohiasma, 79;

Miiller, G. E., atiriliiitea, 21; psycho-

physics, 40; Isomorphism, 80 f.;

ref.,

Necker, L. A,, 268 f.; ref., 804
Neff, W, S„ ref,. 605

Nonmaim, A., ref., 570
E.

B.,356, 359,

390 f.;

ref,, 52. 393, 398

light, 98,
108; color, 101-7, 126; physiology of color,f.; Goethe, 112,

no

INDEX OF NAMES

025
422; lef,, 435

brightness.

132 f.;

color

mixture,139-42;color

circle.

Piei'ce. A. n.,

145 {.;

niter-image,eoa-

Pigot, T,. 325

115;

trast,

158;

165; brightness ol hues,

Pliillips, G.,

385 1.; ref.. 260, 397 f.

Pillbbnry, W. B., 484 f., 532; ref., 617,

567

176 i.: dptie decussation. 227 f.;sound, 322

Piper, A„ 162 f.; ref., 191

100, 112, 119,

IHrenne, M. H., ref., 190

mc.,'fl, 85-7, 97.

122 f., 135, 142, 147, 155, 178,
187,198-200, 207,316.609-11
ref., 122, 153, 190, 194, 257
Nichols, H,, 575; ref., 602 f.

Pisco, inc., 260

Pi-Su8er,
Plateau,

J.

531; ref., 566 f.
A, F., psychophysics, 42 f.;

Talbot-Plateau law, 144 f.; phe-Nicolai, W., 555; ref,, 672

nomenology

Noble, W„ 324 f.

stroboscope, 689 f.; after-sensa-of

156 f.;

eobr,

tion of movement, 591 f.

Noit, C., 343; ref., 350

Nothnagel, H., 498; ref., 519

inc.,

610

Nutting, P. G., ref., 196

ref.,51, 154, 190-2, 005

Plato, inc., 85, 575

O’Connor, J., 420;

Inc., 66; ref.. 93,

435
Oehrwall. II.. 451, 4S4 f.; ine., 450;
ref,, 460 f.
Ogden, 8, M., 379; ref., 896
Ohm, G, S., 326 f.; ino,, 55; ref., 347
Oknbe, T., rol., 568
Oppol, G. W,, ref., 519

Oppel, J. J., 239, 260, 592; ino., 270:r^, 260, 304, 805

PoggendoiB, J. C., 241; ref,, 260
Pole, W., 186; ref., 197
Politaer, A., 383; ref., 397
Poliak, J,. 543; ref., 570
Polvogt, i. M., 425 f,; ref., 438
Ponzn, M., inc., 486; ref., 517
Poppelreutor, W., 296; ref., 810
Forln, G. B.. 222, 227; ret., 257
Porterfield,

C. C„ 361 f.; ref.. 52, 153,
850 f., 894, 510
Pretori, H., 166 f.; ref., IBS
Preyer, W., limits of hearing, 334 f.;

Pratt,

Orbison, W. D., ref., 262
Orfiln, P.,558; ref., 572

Ostwald. W., 02; ref., 92

pitch

Inc,,

340;

coinblnation

291;

ref.,

385-7; aftor-sensaUoD, 502
ino., 857

Pailnaud, H,, 181, 205;ref.,

195 f..

ref.,848, 393, 398

Priestly, J., 200; inc., 155, 183; ret,,

218
Parker, G. H., inc,, 439, 450;

ref.,190, 257, 305. 309

Protagoras, 4458, 400
Parkinson, T. S., inc., 43; ref., 52
Parrish, C. S.. 484 f.;].n.d.,

tones, 356; auditory localization,

Pacini, F,, 530; ref., 500

Fanum, P. L., 288;
308 f,

W., 108, 227, 290; Inc.,

285; ref., 122 f,, 305

ref.,

517

Par^.C, H. H., ref,, 340

Ptolemy, 267, 316-8; ino., 155 f,

Purdy, D, M., 132; ref,, 151
Purkinje, J, E., visinn, 117 f.; indiieot^

171; Purkinje jiienome-

Parsons, T. H., 182; ref., 195 f ., 216

vision,Pas^, J., 447; inc., 439; ref., 4^, 460
Paulsen, E., 440; ref., 458

non, 177 f,, 181; accommodation,

Pavlov, I, P., ine., 534, 555, 500; ref.,573
Peacock, G., ref., 123, 306
Pearson, K,, 12Peirce, C. S,, 40; ref., 51
Peirsec, N. C. F. de, ino., 157

277; vertigo, 536 f.; seen move-

ment, 588
inc,, 115 f., 169, 184, 204. 512, 535,

538, 540
124, 193 f„ 300, 568,005
Pythagoras, 314 f., 318 f., 323; ino.,
ret.,

312

,

Pendleton, C. R.. inc., 471; ref., 614
Penzoldt, F., 442; ref., 459

Quetclet, L. A. J,, Ine., 590

INDEX OF NAMES
Rullier, P., ref,, 572

Rabn, C., 23; ref,, 48
Ramsay, W., 447; ref,, 400
Rand, G., 175 f.; ref,, 193 f,
Raubor, A., 580; ref., 566
Rayleigh, Lady, Inc., 383

Romford, Count, 166; ref,, 192
Rungo, P. 0., 148 f.; ref,, 154
Rudierford, W., 413; inc., 414; ref.,434

Rayleigh, Lord, color blindness, 187;

auditory sensitivity, 336; aural

harmonics, 359; auditory localization,

3^f.; binauralbeats,

388

Sachs, M., ref., 193
Salinas, F., 318 f,

Sander, F., inc., 253

inc., 381, 390

Sanford, E. C., ref., 260, 309

ref., 197, 348, 393, 395, 397 f.
Reboul, J. A., inc., 430; ref., 436

Saul, L. J., inc., 65; ref., 93, 435

Reid, T., 7, 13 f., 975; inc., 19, 74;

SauveuT, J., harmonics, 325; limits ofref.,46 f„ 602

Reissner, E., inc., 404; ref., 432

Rentz, T., 342-4; ref., 350
Retzius, G.. 404; ref., 432

Rente, C. G. T„ ref., 258, 306
R6v6sz, G„ 376, 380, 512; ref., 398,

522

hearing, 332-4; pitch j.n.d., 339;
beats, 352; harmonic fusion, 359
inc., 38, 857
ref., 347 f ., 302

Savart, F., 333-5, 402; inc., 324; ref.,348, 431
Scahill, G. II., ,598; rof., 606

Ribot,T.,ref.,40,258f,
Rich, G.

Sanson, L. J., 277-9; ref,, 306

370, 374, 376, 378-80;

inc,, 21; ref,, 395 f.

Sculiger,
Scltiifcr,

J.

C., 520

E. A.,

ref.,

inc,,

439, 450, 525;

94, 432, 458, 400, 518, 564

Richards, T.W., 456; raf., 461

Schclblcr,

Richardson, L. F., inc., 43; ret., 52

Scheidt, V, P., ret., 196

Riehet, C„ ref., 571

Soliolncr,

Richter, C. P., 557; ref., 572

J,

II,.

319

f.,

329

C„ 223, 273, 275 f.; Inc.,

272, 274; ref., 2.57, 305 f,

Richter, I. A., ref,, 304, 308

Scholske, 11., inc., 174; ref., 194

Richter, J. P., ref., 304, 308

Schcuck, F,, 212; inc., 210, 216; ref,,Rlesz, R. R., 344 f.; ref., 350

Rigaud, ]. F., ref,, 308
Rittenliouse, D., 266; ref., 804

219
Schcrlfer, C., 153; inc., 156, 160; rof.,

191

Ritter, C., rrf., 571

Schiff,Rivers, W. H. R., 471; inc., 548; ref.,Schilf, M., 453; ref,, 401

515, 565, 571
Roaf,H.E.,406,409;ref.,433
Robinson, V., rrf., 124
Romer, 0. C,, 98; ref,, 121
Hoff, M. R„ ref., 604
Rogers, F.T„ 557; ref,, 572
Roget, P. M., 588; ref,, 605
Romndo, L., inc., 94; ref., 568 f.
HoDett,A,,531;ref„587
Romberg, M. H., r^., 569
Homieu, j, B., 353; inc,, 357; ref., 392
Ross, J. S., inc., 43; ref,, 52
Roux, J., 553; ref,, 571
Rubin, E., 249-51, 506 f., 511; inc.,258, 587; ref., 261, 520
Ruckmick, C. A, 587; inc,, 583; ref.,397, 604
Rufflni, A., 531; ref., 566

Schirmer, R,, ref., 194

J.

M., 467, 500; ref., 513, 573

ScMesinger, E. G., 548 f.; ref., 571
Schlick, M., 12

Schbsberg, H., ref,, 521
Schmidt, C., 560; rrf,, 573
Schneider, G, H., 594, 600; raf., §00
Scholz, W., ref., 606

Schopenhauer, A., 115 f.; inc., 199;
ref., 124
Schott, G., inc., 347; ref., 257
Schotiy, W., ref., 394
Schriover, W., ref,, 308

Schroder, H., 266, 269; ref., 304 f.

Schubotz, F., ref., 310
Sehultzo,M., 179, 204, 210,

440;

Ino„ 204, 450; ref., 195,217, 458

Schumacher, G. A., ref., 518
Schumann, F,, 244 f., 247-9, 532 f.;

INDEX OF NAMES
250, SS7j

ino.,193, 201,

ret.,

560 1.

627

Stetson, R. H., inc., 586; ref,, 604

Stevens, L. T.. ref., 603

Schur, E,, ref., 310

Stevens, S, S., attributes, 25 f.; tonal

Schwalbe, G., 450 1.; ref. 400
Scripture, E: W.. ino., 385

quanta, 345; combination tones,
356; aural harmonics, 859; to-Sedillot, C. E., 552; r^., 571

nal attributes, 376-9, 381; audi-

Seebedt, A., 184 1., 319, 329, 340;

tory localization, 390 f.; pitch inInc.,

178, 188, 190, 196, 324,

405; ref., 195, 347
Shombaugh, G. E., 409; ref., 433
Sheehan, M. A., 297; ref., 262, 308,

310

cochlea, 426-8; theory of hear-

430 f.

ing,inc., 33, 44
ref., 40, 49,

51 f., 95. 152, 347-51,

393-8, 432, 434-6

Sheppard, H., Inc., 164; ref., 192
Sherman, F. D., 181; rd., 195

Stewart, B., inc., 87; ref., 95

Sherren, J., 471; ino., 548; ref., 515,

Stioli, A.,

Stewart, D., 7, 14; ref., 46 f.

565, 571
Sherrington,

453; rd., 461

J„ 187; rd.. 197
Stirling W., rd., 92
Stilling.

C.

S.,

492,

71,

525,

528 f., 534 f.; ref., 94, 513, 518,

Stout, G. F., rd, 151

M„ 237; ref,, 269, 519

504, 506-8
ShIaer,S„ 182; ref.. 190

Stratton, G.

Shore, J., 319, 323, 329

Strenger, F., 178; ref., Iffi

Shore, L. E., 452; Inc., 454; ref., 461

Striimpcll, A., 532; ref., 537

Shower, E. G„ 340-2, 345; ref,, 349
Slnden,B.H„rof., 154

Strutt, J, W., sea Rayleigh, Lord

Sinsleden, W. J., 270; ret., 305

Sliickcr, H,,

Slvlaa, L. J,, rd,, 349

Stumpf,Strauss, H. II„ 501; ref., 520

Studnicka, F, K., rd, 124340; rd., 349
continuum, 10;

C., sensory

29 f., 233; brightness,

Skinner, B. F., 558; ref., 572

nativism,

Skramlik, E. v., Inc., 437, 439, 450;

134; local signs, 235; phenomenology, 247, 249; fudon, 360-2;

ref., 458-60, 513,

504

Slade, II., inc., 31

noise, 364; lonal attributes, 376,

Sloan, L. L., ref., 194378; aural stimulation, 382; tonal

Smith, A. H., ref., 190

gaps, 410

Smitli, M. E.. 362; ref., 304
Smiili,R,

inc., 285; ref.,inc., 21,23, 28, 33, 38. 340, 381,

304, 444, 612

190

SneU, W,, 08; ref,, 121

ref.,Snow. W, B.. 385; ref., 398
Soemmerring, S. T., 554; ref., 671
Sorge, G. A., 353; ref., 392
Soury, J., ret., 94

46, 50, 152, 259, 307, 393 f.,

396 f., 433
Sturm, J. C., 275; rd., 306
SulUvan, A. H., 510-2; rd. 521 f.

Swammerdam, J., 55; rd., 91

Spiro, K., ref., 51, 460

Szabadfoldi, M., 466; rd., 513

Spoerl, H, D., ref,, 94

Szokalsky, V.,

Spi&zhcim, C., ref., 94

171;

inc.,

199; rd.,124, 193

Stampfer, S., 590; ref., 005
Starke, P., 344; ret., 350

Talbot, E. B., 22; rd., 48

Starling, S. G., ref,, 347

Talbot, W. H. F., 144 f.; rd., 154, 308

SteinuOT, E., 64; ref., 93
Steinberg, J. C., 385; ref., 398

565
Sielnheil, C. A., inc., 153

Stem, L.W„ref„349,602
Sternberg. W.. 456; inc., 454;

461

Tarchanow, J., 385; ref., 397
352 f.; rd, 392
Tawney, G. A., 479 f.; rd, 516
Taylor, E,, inc., 43; rd., 52
Terman, S. W., ino., 189; rd., 197
Terpander, 314
Theophrastos, i£c., 122
Th%, A., 245; rd., 201

TartinI, G.,

Steinbuen, J. G., 526; inc,, 528; ref.,ref.,INDEX OF NAMES
Thompson, B., see Rumfoid, Count
Thompson, S. P„ 384 £„ 387 f., 593i
ief„397,80S
Thomson, William, see Kelvin, Lord

Umrath, K,, ref., 93

Thouless, H. H., 236, 297. 299; ref.,Urbanlschitsoh. V.. 385,' 502 f.; ref.,Thunberg, T., 503, 506;
ret., 513, 520 f.

ine.,

504;

ValenU.A., 5S0;ref„573

Tiedeniann, F., 552; ref,, 571
Tischer, E,, 343; lef.,

Titchener, E. B.,

3M

numberof sensa-

10; context theory, 17 f.;volume, 21; attributes,
28 f.; imity of senses, 27; empiricism, 31 f,; rayolioplmios, 42 f.;
tonal

Valentin, G.. 458; ref., 481
Vance, T. F,, 340 f.; ref., 349
Vannod, T., 481; ref., 516
Vaschtde, N., ret., 459•

Vater, A., 530; too., 566
Vesallus, A., too., 91

Vierordt, K., psychophysics, 40; lu-

brightness, 134 f.; color mixture,minosity cmve, 178; two-point

conver-Bmen, 477 f.; thermal stimulus,
490 f.; time-sense, 578 {,; attorsensalioii of movcmcnl, 503;
movement sensation, 504
ine., 342 1., 350, 479, 581, 604
ref,, 51, 195,515, 518, 603, 005 f,
Vlclh, G. U. A., 229, 353; rot., 257,
392
Vinci, see Leonardo da Vinci
Viulschgau, M. v., 454, 457; too.,nativism,

148;

233 f.;

gence, 272; limits of heating,336; vowels, 374; tonal attributes, 378, 378, 380; two-point

limen, 482; touch blends, 510,

512; Idnestlietio contents, 533;

rlythm,sexual sensation, 504;

686; apparent movement, 597
ino,.3.fff.. Ilf.. 15.21,28,371.,

130 1,, 136 f„ 152. 611

120,

re£„

46-51,

151 f.. 258-61, 305,

396 1„
460, 518, 521, 567 f„ 573, 803 f.
Toepler, A., 320, 330; lef., 348
Tolman, E. C„ 13. 18. 47 f.. 657; ino.,
12; ref., 47 f,, 572
Torricelli, E., 321
Toulouse, E., ref., 459
Toynbee,
537
J.,
Trenddenbere, W., ref., 196
Trevlranus, G. R., 274 f.; Inc., 119,309, 348-51, 394,307,

439, 4.50; ref., 458, 400-2
Vlviani, V.. 322

Vooslo, IL, too., 164; ret., 192

Volkmann, A. W., 73, 225, 480; ine.,
41, 119, 484; rot,, 94, 124,518
Volkmann, J., 345; inc., 38; ref., 51 f.,
350 f.
Volta, A„ 55-7; too., 609; ref., 91

Volb,A, C., 599; ref., 606

Wada, T., 557; ref,, 672

203, 217; ref., 124, 305 f.

Waet^ann, E., toe., 411; ref., 432,

Trimble, 0. C., 390; ref., 397 £.
Troland, L. T., 66, 164, 418; ino., 215,

434
Wagner, R., inc., 439, 450; ref,, 50,

192 f.,

04, 124, 259, 275, 306, 458, 400,

423;

ref.,

93. 125, 153,

185, 2SS, 396, 434 f.
Trotter, W.. 474; ref., 515

Troxler, D., 171; ref,,'Urban, F. M., 30; ine., 37; ref., 51
520

262, 310 f.

tions,

Unzar, J, A., 55; ref., 91
Upton, M., ref,, 436

193

Tschetmak, A., ref., 191, 217
Tung, S.. 510; ref,, 521
Turbervile, D,, 183; ref., 196
Tnmbnll, L., too., 335
UooeBo, P., 285

Uhlmann,H. P.,501; ref., 520
Ullrich,H„ 479, 481,*'484 f., 502; ret.,

518, 620

513, 510, 518, 569-72

Wagoner, K. S., ref., 518
Wallach, H., 891 f.; ref., 398
Waller, A, D., 412; inc., 417; ref,, 434
Wallis, J.. 324 f,; too,. 357; ref,, 347

Ward, J., too., 258
Warren, H. C.. ref,, ISO
Washburn, A. L., 655 f.; ref., 572
Washburn, M. F., 22; too., 557; ref,,48, 572
Watson, J. B., 11 f.; too., 13, 534, 557;
ref., 46, 572

INDEX OF NAMES

629

Watson, W,, tel., 347

Wilson, G., 1851.; ref., 196 f.

Watt, H. J., 378, 380, 417; ref., 394,

Wilson, H. A, 380; ref., 398

398, 434
Weber, E. F,, 383; ino., 387; ref., 397

Winsor, A. L., 559; ret., 573

Weber, E. Hi, Weber’s law, 34 f.;
42; projection,
80; ..auditory localization, 383;
psycbofihysics,.

smeU

440 f.; tactual
465 f.; pain, 407; two-stimiilus,

senses,point limen, 475-7, 479, 481; error of looalizatton, 483-S; ther-malstimulus,490-2;

pressureW., Inc., 805
Wittmaack, K.. 425; ref., 433
Woinow, M., ino., 174; ref., 194
Wolf, Abraham, ref., 91, 122, 340
Wlrtli,

Wolf, August, 842-4; ref., 350
Wolff, H, G.,ret., 518 f,

Wollaston.

W.

H., 79,227 f., 108,

in, 127 f.. 401; ref., 149, 257,
431

495 f.; thermal summation, 498 h; thermal adaptation,

Woodrow, H., 582, 585 f.; ino., 578;

500; internal sensibility, 545-7;
hunger, 555
ino., 10, 29 f., 81, 288, 851, 387,
463, 487, 494, 497, 499, 501,

Woods, E. L., ref., 588
Woodworth, R. S., inc„ 94, 193, 440;
ref., SOS, 309, 458, 567, 570
Wooster, M., 238; ref., 260

509, 518

Wrightson. 'I'., rd.,j.n.d,

ref.,50 f., 259. 397, 458, 518,

515-9, 565, 570-2

Weber, W. E.. ino., 397
Wegel, R. L., 337 f.. 359, 366 f.,
427-9;

ino,,

895;

ref.,

3481,

603 f.

ref.,4^

Wunderli, A., 466; ref., 513

Wundt, W.,associationism, 9; per-ception,

15 f.; attributes, lEb21,

375; unity of senses, 27; empiricism, 31, 233 f,, 236; color coneand sphere, 148; contmst, 170;
local signs. 235 f.; Illusion, 2404 convergence and accommoda-

393 f., 436
Weinniami, H., rof., 94
Weiss, A. P., ino,, 12;

Weld.H, F..47t.irer.,47tion,

279-81; limits of hearing,

Werner, H., ref., 431
Wertheimer, M., 250-2, 389 f., 595 f,,

834;

fall

599; ino,, 5, 48, 224, 253, 600-2,
810 f.; ref., 60Sf.
Westphal, H., 129; ret., 150

taste qualities,

apparatus for noise,

842; 6ieory of hearing, 416 f.;
454; sensationsof innervation, 525; kinestheHocontents, 533; internal sensibil-

546; time perception, 576;

Wettendorff, H., 560; ref., 573

ity,

Wever, E. G., 419-23; ino,, 65 {.; ref.,93, 434 f.

rhythm, 583 f.; afte^sensatio^ ofmovement, 592; seen movement,

WheaMone, C., 285-7, 371; ino,, 283,

593
ino., 3f., 8f.,

282, 611; ref., 308, 395

11, 13. 28, 28, 30,

Wheeler, R. H„ rd., 48

37, 42, 48. 87. 116, 169, 210,

Whewell, W., ref., 122, 348
Whitchurch, A. K., 600; ref., 606
Whits, S. D., ref,, 349
Whytt, R., 55; ino., 63; ref., 91
Wien, M., 386 f.. 344; ref,, 348, 350

216, 221, 261, 272. 289, 293,
340, 343, 381, 386, 484, 519,

Wilcoclts, R, W., 24; ref., 49

Wilkinson, G,, 409;

ino.,

411;

ref.,

526, 528, 574, 580, 586, 612
ref,,46 f.. 49-51, 154, 193, 218,

258-61, 307, 348, 350 f., 434,
401, 566 f., 570, 602, 604 f.
Wyss,H.v..451;ref.,461

432-4
Williams, H. B., ino., 65; ref., 93

Yokoyama, M,, 24; ref,, 49
loshii, U., 411, 425; ref., 433 f.

Williams, R, E.. 181 f.; ref,, 196

Young, P. T., nrf.,

Wille, H. H„ ino,, 43; rof., 52

Willis, R., 369-71; ref., 395
Willis, T.. 54; ret., 91

WlIska,A.,339;rBf.,340

MO

Young, T., specific energies, 70; Mit,acconhnodatlon,
109 f.,
108;275-7;

color

theory,110-2,

INDEX OF NAMES

630
Young, T., ccmtimed

199-Mlj color, 127; primaiy colors, 128; color triangle, 14fl; contrast,

107; indirect vision, 171;

difference tones, 3S3
ino.,

72, 108, 115, 119, 122, 129,140. 172, 185, 203, 228ref.,122 f,, 192 f., 218,300,892

Ziglcr,M. J., 443, 501, 510-2; rof.,459, 517, 520, 522
Zollner, F., 241; inc., 31; ref,, 260
Zoll, P,M„ 24; ref.. 40

Zotturinnn, Y., 65; ref,, 23

Zurmuhl, G„ 324, 378; ret., 398
Zwaarderaaker, H., handbook, 438 f.;
smell organ, 440; olfactometry,441-3; smell laws, 443 f.; smell
Zatlino, C., 318

classes, 444-6

Zebrowski, E. v., 560; ref., 573

inc.,

438

Zenneck, 453; id., 481

ref.,458-60.

INDEX OF SUBJECTS
Abstractlcm, Kiilpe, 23, 48 f.

Ampullar sense,

Accidental colors, 156, 180

bilityAccommodation, convergence, 279-

82,307cue

tom

Vestibular sensi-

Anagljmtoscope, 266
AnimaTelectricity, 56-8, 91

272-82, 302 f.,

distance,

305-7

Animal spirits, 53 f., 62, 91
Apparent movement, attitude, 598

function,

122 £,

109 f.,

auditory, 601, 607

272-4,

302 f.

cortical short-circuit, 596, 599, 606

theories, 274-8, 306 1.

deteiminants, 598 f.

Young, 109 f., 123

early investigations, 588-92, 605'Acoustics,

Actionm Soundpotentials,

eye movements, 591-3, 599, 605
auditory

field theory, 599

nerve,

423f„43Sf.

illusions, 588-90, 605

sensory, 64-0

Korte’s laws, 598

Adaptation, Auberi, 160 f ., 191
color,

negative aftcr-sonsation, 591-3, 605

optimal movement, 595-8, 606

163 f„ 191 f.

dark, 160-2

V>-phcnomenon, 505-8, 606

Bering, 101

primacy, 594, 805 f.

104, 191

light, 162 f.

sensation given, 594, 605 f.

pdn, 501, 520

stroboscopic, 589-91, 605

pressure, 500 f,, 519 f.

subjective complement,

smell, 443, 459

tactual, 509-601, 606 f,

taste, 457, 461t^es, 595-7, 606

terminology, 191

Wertheimer’s

thermal, 498, 500, 519
vestibular, 536, 539, 543 f., 570
visual,experiment,

Apparent size, 289 f., 309
See also Size Constancy
Appetite, 551-3, 557 f., 562 f., 572

Aerial perspective, 266 f.

See also Hunger

After-images, visual, 157-60, 190 f.

Appunn lamell^ 334

After-sensations, tactual, 501-4, 520

Articular sensation, 532

vestibular, 536, 539, 543 f,, 570

Articulation, 253

visual movement, 591-3, 605

Associationism, 14-6
sensation, 3-10, 46

Alimentai'y canal, exaetory processes,

564

Attributes, S f

astric processes, 583 f.

actuality, 23 f.

unger, 551-8, 571 f.

attention, 22, 24

sensibility,
thirst,596 f.,

602, 606

160-4

Adequate stimulation, 71 £, 94

593

common, 27

546-51, 571

criteria, 20 f., 25 f.

558-61, 572 f.

Alley problem, 290, 294-6, 810

dimensions, 24

All-or-none law, 60-2, 06, 92, 214,

duration, 576 f., 603

419, 423 f.

elements, 22

Hornbostel, 27*e-movement, 597

Kiilpe, 20-8

Amplitication. electrical, 332

631

1

.

1

1

1

INDEX OF SUBJECTS

632

ness, 408; Ohm’s law, 408; prin-

Attributes, conUnued

ciple

learning, 26 f.

ofmaximalamplitude,number, 26 f.

408 f.,

references, 46 f

4061, 4331;

senses, 574

brane, 409 1, 433’; tension, 409,

Stevens, 25 f.

481,

433;

resonators,

mem-

toctorial

438

stimulus, 49, 25 f., 377-81. 396 f.

Tltchener, 22-4

stimulation

lesions,

4K, 4251,

4331, 436

tones, 21f,,25f., 375-81,3901.

unity of senses, 27, 49

telephone, 418
tonal gaps, 410 f., 433

vision, 21

Aural harmonics, 358 f., 398

Wundt, 19 f.
See also Sensation
Beats, beat tone, 353, 356, 392

Aubeit-Fdrster law, 249, 3091

binaural, 387 f.

Au^blllty curve, S86-8, 348 {.

masking, 366 f.

Audiogram, 337 f., 348
Audition, seo Auditory localization,

Au^tory

Noi^

Ear,

llieory.

origin, 352-7, 892

theory, 3551, 408

Behavioral operationism,

Rtch, Tone, VowelsmPositiv-

ism

Auditory localization, apjsaraitnioveBehaviorism, 46

meut, 601, 607

behavioristics, 13

binaural beats, 887 f.

390 (., S97

binaural ratio, 384 f

dichollc differential, 8821, 387-91

dlohotic

Intensity,

383-5, 890

111

BlniuinU ratio, 3841, 390 {., 3971

Binocular pimilliuc, 282-5, 307 f.

3971
dicbotic phase, 884, 887-81,3971
dlchotic stimulation, 382,^-91

dlchotlc time, 889-91, 398

semicircukr canals, 386 f., 398, 541
space continuum, 381 f

886 f.

tactual cues, 383, 387,

8^

Body-mind relation, .wc Mind-bodyrelation, Isomorphism

Bow movomenl, 597
Brain, see Isomorphism, Localizationof brain function

194-6

Auditory theory
action potentials in nerve, 4231.,4351
cochlear dmamics, 429-31, 430
direct cocluear lesions,

tonal, 378, 396

See also CobrBrightness constancy, 255

426^ 436

duplicity, 364, 418

Cerebrum, see Isomorphism, Local-

frequency, 413-8, 434

ization of brain

Haller, 401, 431

ofifl-movt«uaiil, 590

Briglilncss, luminosity curve, 176-82,

tridimensional, 391 1, 398

localization

seitsallon,

Boll-Mag(']]die law, 68, 92 f.

funetbn

Chemical senses, 437 f.
pitch

in

(xmblea,424-9, 436,

See also Smoll, Taste
Circular reflex, 527 f., 565

M. Meyer, 413-6, 434

Closure, 253

models of ear, 410, 438

Coclilea, see Ear

place, 406-11, 4161, 432-4

Cochlear response, 420-3, 435

platoon volleys, 421-4, 435

Coenesthesis, 545

pressure-pattern, 412, 434

resonance,

Gold, see Thermal sensibility

back-Color, accidental, 156, 100^und, 404 f„ 432; beats, 408;

achromatic series, 133 f.

bright and duf, 408, 438; com-

adaptation, 1631, 1911
afeimages, 157-60, 190 1; nega-404-11,

432-4,*

bination tones, 408; diffioulties,

4061; bading, 409, 433: loud-tive, 156 f.; positive,

167

.

.

.

.

.

.

INDEX OF SUBJECTS
Bozold-Brticke phonomenon, 131 f.,

151

033

visual purple, 205,

217 f,

white light, 103 f.

black. 138 f., 151 f.

zones, 172-6, 194

brightness, 106 1., 132-6

See also Adaptation, Color blind-central processes, 212-4

ness, Color diagrams. Color mix-color blindness, 182-90

ture,complementaiies, 139-43, 154

nomenon, Visioncontract, 169 f.

Contmst,Purkinje

Color blindness, anomalous, 189

cortical gray, 133 f.

Dalton, 108 f., 184, 196

discriminable hues, 129 f., 150 f.

deuleranopia, 188 f.

double representation, 135 f., 152early theories, 100 f., 121 {.

dichromatic, 188 f., 197

dementary hues, 127-31, 150 £.

monochromatic, 189

evolution, 210-2

protanopia, 188 f.

Goethe, 112-6, 123 f.
homogeneous Ught, 102

tests,

early cases, 183 f., 196

186 ftypes, 184-9, 197

indirect vision, 171-6, 193 f.

Color diagrams. Ebbinghaus’ pyramid, 148 f.
Helmholtz’s cii’cle, 145

intensity, 132-9
liglit sense,phe-

132 {.

memory, 2ffi fmodes of appearance, 135, 152
Newton, 101-7, 122
objects, 107

Helmholtz’s triangle, 147, 201
KBnig’s triangle, 14'7

Lambert’s pyramid, 148
Maxwell’s triangle, 146 f.

phonomenal green, 131, 151
phenomenology, 113 f., 124, 135 f.,
152
primaries, 104 f., 127-31, ISOt,
2021.
principal hues, 129, 150
refraction, 101-7

Newton’s circle, 139 f.
references, 154

Bunge’s pyramid, 148 f.

Wundt’s oono, 148
Wundt’s sphere. 148
Color mixture, Grassmann, 141-3
Helmholtz, 140-5, 153 f

relation to tones, 104 f

Hering theory, 209

shadows, 157, 192
simplidty, 130 f., 151
spectra, 156, 160
stimulus, 126-32, 149-51

laws. 139-43, 153 f.

theory, all-or-none law, 214;

methods, 144 f
Newton, 108, 139 f.
Newton’s circle, 139 f.

Au-

bert, 207; brain, 212-4; Donders,

212 f„ 219; duplicity, 203-8,
217 f., Ebbinghaus, 219; Edridge-Green, 219; evolutionary,210-2; excitation curves, 200,

Tulbot-Plateau law, 145, 154
Combination tones, distortion, 355-7
origin, 852-7, 392 f.
theory, 408
Common sensihility, see Gemeingefirhl

202; G. E, Muller, 213. 219;
Goelho, 114 f.; Hecht, 215 f..
220; Helmholtz, 173 f., 200-2;

Compass tesl, 475-7

Hering, 173-5, 194, 209-9, 218;

Consonance, 380
Constancy phenomenon, 254-6, 292,
288-99, 308-11

indirectvision.

173-6,

194;

Konig, 219; Ladd-Franklln, 2102, 219; McDougaQ, 212, 219;
Newton, 107, 110 f., 198 £.; references, 216-20; rods and cones,
203-6, 217; Schopenhauer, 115 f.;

von Eries, 205 f.; Wundt, 218 f.;
Young, 110-2, 123, 199 £.

Conscious attitudes, 533 {., 567 f.
Conscious present, 576, 602

See also Size constancy
Context theory, Berkeley, 9
perception, 17 f., 47 f.

rhythm, 586 f., 904
Titohener, 17
47 f
Contrast, apparent movement, 598

.

INDEX OF SUBJECTS

634

stiinnlaiion

CoaliDSt, cottUmted

lesions,

411,

Wcver-liray effect, 420-3, 435

brightness, 188 f

contours, 167, 170, 193

Emmert’s law, 292 1,, 310
Empiricism, 3-6, 49 1.

Helmholtz, 167 f.. 192
Leonardo, 188

bmiavioiism, 331.
Helmholtz, 31

color,

169 f.

visual, 185-71,1921.
Convergence, accommodation, 279-

Kiilpe, 31 1.

Lotze, 30
origins, 28 1.

82, 307cue to distance, 2711., 302 f., 305,
307
Cornea, accommodation, 276, 306

Corresponding

4251.,

433 f„ 436

brain. 170 f., 193

points,disparity,

284 f., 287 f„ 308
Cutaneous sensation, see Touch

sensation, 45

Titchener, 32
visual space, 233-7, 2581.

Wundt, 31
Epimitlc sensibility, 471-5, 515
Equal temperament, 317-9
Equilibration, see Vestibular sensibil-

Daedalciim, 590 f.

Deal mutes, vertigo, 542, 570
Deep sensibility, 47 1-3, 523 f „ 565
Density, tonal, 377, 380 f ., 397
Dlcbolic stimulation, 382, 387-91
Dtoliromatic vision, 187-9, 197

Dioliromio vision, 188, 188
Difference tones, 352-7, 892 1.

Dimensions of consciousness, see Attributes

Diotic stimulation, 382

ity

Enor ol localization, see Touoli
Eye, accommodation, 272-9, 305-7
convergence, 271 [„ 305
retinal imago, 222-5
See also Vision
Eyo-movomcnls, Douders’ law, 230-

'

2,258
Listing’s law, 230-2, 258

space percuplion, 230-3, 258
torsion, 232 1,

Discrimination, see Weber function

il-mcvement, 597

Fecbncr lunctlon, see Psychophysics

Danders' law, 230-2, 258

Field theory, 246-52, 299-303, 311

Double representation, 1351., 152.
300 f.
Drive, appetite, 551-3, 557 £„ 562 1.,572

apparent movement, 599
Figure and ground, 250 f., 253

Formants, 372 1.
Form-quality, 16 1., 47, 246

sensation, 561-3

Fourier analysis, 325-8, 347

thirst, 559-61, 503, 573

Fusion, tonal, 359-62, 393 1.

Ear, action potentials in nerve, 423 1.,

4351.

Galton whistle, 333, 335 1.
Gastric perceptual patterns, 563

anatomy, early knowledge, 400 1,,
431

Gemeingeliihl, 485, 467, 545-7
Genetlcism, see Empiricismrcochlea, early theories, 402-4j his-

Gestalt

tology, 404-7, 411, 432

cochlear dynamics, 429-31, 486
cochlear response, 420-3, 435
direct lesions, 426-8, 438
localization of pitch in .cochlea,

424-9, 436

middle, 401 f., 431 f.
platoon-volley theory, 421-4, 435

round window, 4021.
sensitivity, 339, 343 1.

psycliology,form,252-6,

281 f., 299-303, 311
Gestalten, visual form, 246-^2, 261,

299-303, 311

See also Visual space percepUon
Gestallqualitat, see Form-quality

Giddiness, 535 {., 568
T-movement, 59'?

Golgi ^indies, 531, 587
Crave harmonics, 353
Greek music, 313-8

.

.

,

INDEX OF SUBJECTS
Iliumonics, nuial, 3S8 f ,, 393
grave, 353

Internal sensibility, 544-6, 570

limits of hearing, 333-6

See also Visceral sensibility

nature, 324 £,, 347

Intervals, musicul, 313-8, 346; char-

Ohm’s !nw,_326-8

acteristics,

timbre, 357-9, 393

62,

Hearing, see Auditory

Auditory

theory.

localiratlon.

Ear,

Music,

Noise, Pitch, Tone, Vowels

Heat, ambiguity of term, 508 f., 521

oold-wmm fusion, 504-8, 521

381 f.; fusion, 359393 f.; sensory magnitude,

350
Introspection,

icinesthetic

content,

533 f., 567 f.
Inversionofretinalimage,

223-5,

287 f., 259 f.

506 f., 520 f,
intensity, 508
pain-warmth fusion, 508, 521
quality, 507, 521
Hering window, 168
Horopter, 226-30, 257 f
retinal disparity, 284 f., 287 f., 308
Hue, see Color•Hunger,
appetite,551-3,
557 f,
582 f„ 572
central origin, 553, 571
contractions, 555-7, 572
drive, 551-3, 557 f., 562 f., 572
early tlieories, 551-3, 571
gastric stimulus, 553-7, 571 1.
eneral sonsalion, 552 f ., 671
gleories, 552-7, 571 f.
grill,

I

635

Intensity, frequency theory, 67 f.

Irradiation, 81
Irritability, sense-organs, 71 f„ 94

muscle, 54
Isbihara test, 187

Isomorphism, anticipations, 84 f.
apparent movement, 598, 599, 600
conservation of energy, 86 f., 96
criticism, 00,

06

definition, 83 f

Fechner, 88

G. E, Muller, 89
Grassmann, 87 f.
Ilaitloy, 8K5Mer, 00
Lotzo, 87Mach, 88
parallelism, 85-90

references, 95 f

Idea, Hume, 6

tonal attributes, 377 1,

Ideomotor action, 529

visual depth, 303

Illusions,

Oiledand empty

space,

Isopbonic contours, 377

239 f.
geometrical, 238-45, 260 f,

J,n.d., 36, 38, 43, 52

Helmholtz, 240, 243

magnitude, 350 f.

Hering, 241 f.

Just temperament, 316-8, 346

Miiller-Lycr, 243-5, 261

Foggendorff, 241reversible

perspectives,

268-71,304 f.

Kinesthesis, 524-35, 565-8

conscience musculaire, 567

tbeories, 244 f, 261

conscious processes, 533 f., 667 f.

veitical, 240

Einstellung, 533, 567

Wundt, 242

Golgi spindles, 531, 567

Zbllner, 241

ideomotor action, 529

Indifference point, time-sense, 578-

82, 603
Indirect vision, Aubert, 172

early experiments, 171 f., 193

zones, 172-6, 194

Inner sense, 5
Innervation, sensations, 527-9, 565 1.;

ideomotor action, 529,' r^er action, 529; will, 528

joint vs. muscle, 532
lifted weights, 529 f., 532 f., 567

muscle sense, 526 f., 565
muscle spin^es, 530 f,, 566 f.
Pacinian corpuscles, 530, 566
of movement,

531 f.,

proprioc^tfont 526 f., 534
rhythm, 586 f., 604

568

perception

567

.

.

.

INDEX OF SUBJECTS

636

Memory color, 255 f.

Kinesthesis, continued

sensations of innervation,

527-9,

Mcntitlmeasurement,

see

Fsycho-physici,

565 f.
terminology, 525, 566

Motlrod of average error, 41

wiD. 528

Method of constnirl stiipuli, 38-41
Method of just noticeable dlSeretrces,

Koenig cylinders, 335

Kundt dust metlrod, 833, 335 f.
Lens of eye, accommodation, 276-9,
306 f.
function, 222 f,
Leonardo’s paradox, 233 f.
Light, early theories, 98 f.
refraction, 127 f.
theories, 107 f.
vebdty, 99
See also Cobr, Vision
lumen, absolute, 36, 41 f.
differential, 36, 42
See

also

Psychophysics,

Smell,

Taste, Tone, Touch, Vision

Limits of hearing, 332-9, 348 f.
Listing’s law, 230-2, 258

visual, 232-6

Localization, visceral, 547, 549 f.
visual, 236 f., 288

Auditory

cner^, 86 f.
interactionism, 85
arallclism, 85-90

ee also Isomorphism
Modalities, 10
taste,

4^

localization.

Touchhenornonon, 250-2

Muscle sense, 526 f„ 565
norvous circle, 527 f., 565
spindles, ,530 f., 560 f.
Muscle spindles, 530 f., 566 f.
Music, consonance, 360
Greek, 318-6
pitch standards, 310-21

Localization of brain function, Flouscales,

rens, 74 f.

Fritsoh and Hitzig, 75

Horlng, 29

Lashley, 76 f,

Joh. Muller, 29

references, 94 f

Kiilpe, 31 f,

sensory centers, 75-8

origins, 28

speech center, 75
See also Isomorphism
Logioal positivism, see Positivism
differential

sensitivity,

342-6, 350
tonal attribute, 377 f.
Luminosity curve, 176-82, 194-6

Masting, 365-7, 394 f.
Meaning, Imagery, 47 f.
See

313-8

Nativlsm, Gestalt psychology, 33

Gall, 74 f.

Loudness,f.

Monotic stimulation, 382
Moon illusion, 267
Movement, tinesihoUe perception,
531 f., 567
parallax and distance, 267 1,, 804

Muller’s circle, 228-30, 257 1,

unconscious, 235 f.

also

41

Mind-body relation, conservation of

ee also Anparenl movoment

Local signs, 29-32
tactual, 234-6

See

38

Method of limits, 37 f.
Metlrod of right and wrong cases, 38-

mo Context theory

phenomenology, 32 f
primitive spatiality, 234
references, 49 f.
Stumpf, 29 f
Titehener, 32
visual space, 233-7, 258 f.

Natural scale, 316-8, 346
Nausea, 563 f.

Need, see Drive
Nerve conduction, Adrian, 59-61, 65,
68

Meantone temperament, 318

all-or-none law, 60-2, 66, 92, 214,

Measurement, see Psychophysics
Mel, 351

animal electricity, 56-8, 91

419, 423 f.

.

.

.

'

.

INDEX OF SUBJECTS
miimal spirits, SS f., 62, 91
Boll-Mngendie law, 03, 92 f.
Bernstein, 53 f., 62

637

KInestliesis,

Thirsl,Vestibular

sensibility. Visceral sensibility

Oscillation, electrical, 332

Burolli, 54 f.

current of injiny, 57

Pacinian corpuscles, 530, 566

Descartes, 54

Pain, 465, 467-75, 513 f,

du Bnjs-Reymond, 57 f

adaptation, 501, 520

electricity, 55-62, 91 f.

end-organs, 470

Erasistratos, 53

intensive theory, 467, 469, 514

Forbes, 65-8

modality, 469, 494

frequency tlieory, 67 f

stimulation, 493-5, 518

Galm, 53 f

references, 91-3

summation theory, 469, 499, 502 1.,
519 f.
visceral, 546-51, 571
von Frey’s theory, 494 f., 518
Paradoxical cold, 469, 492 f., 504-7,
518
Paradoxical warmth, 506 f., 520 f.
Parallax, hlnocular, 282-5, 307 f.
Parallax of movement, cue to disstance, 267 f ., 304
Partials, 325

refractory period, 59-62, 66 f., 92

Perception, association, 14-6

Galvani, 55-7
Glisson, 54 f

Haller, 62

Helmholtz, 58, 92
instrumonts, 64
irritability, 54, 71 f.

kinds of impulses, 77, 95
Lucas, 59-61

membrane theoiy, 61 f., 92

sensory, 62-8

auditory localization, 381-92, 397 f.

sensory action poLentials, 64-6

audilory space, 381 f., 386 f.

sensory intensity, 87 f.

Berkeley, 5 f.

sucous nervous, 55

context theory, 6, 17 f., 47 £.

Swaminordam, 55

Cornelius, 17

velocity, 58, 92

aitcria, 264

vis nervo,sa, 55

Dcinocrilos, 4 f.

vis viva, 55

double representation, 135 £,, 152

Volta, 56 f.

Ehrenfels, 16
Empedocles, 4wave of negativity, 58 f,
Wever-Bray edecl, 85
See aUo FrojocBon
Nervous circle, 527 f.. 585
Noise, duplicity theory, 364 f.

Epicuros, 5field theory, 246-52, 299-303, 311,

599
figure and ground, 250 f., 253

eneradon, 363-5

form-quality, 16 f., 47

glermal, 365, 394

Gestalt psycliology, 19

tonality, 363-5, 394

Heraclitos, 4vowels, 373

history of concept, 3 £., 13-9

horopter, 226-30, 257 f.

Hume, 6
Odorimetry, 443

Ohm’s law, 326-8, 347
Olfactie, 441 f.

illusions, 238-45, 260 f.
Jas. Mill,J,

15

S. Mill, 15, 18

Olfactometer, 441 f., 459

Locke, 5

Operationism, see Positivism

Meinong, 16 £.
mental chemistry, 9

Optics, early knowledge, 97 f,, 100 £..

121 f.
eye, 99 f.

Organic sensibility, classiilcation, 523

See also Deep sensibility. Hunger,modes of color, 135, 152
movement, 250-2, 588-602, 604-7
Protagoras, 4reduction, 249 f., 311

.

,

INDEX OF SUBJECTS

638
Perceplion, eontimed

Phrenology, 74, 94

references, 47 1,

Physicallsm, see Positivism

Held, 13 f.

Pitch, dilferenUal sensitivity, 339-42,

retinal image, 222-S, 257

349 f.

rhythm, 583-7, 604

frequency, 322-4, 3461.

Scottish school, 47

lower limit, 332-8, 348

sensation, 13 f.

musical scales, SIS-S
standards, 318-21

Stewart, 14
tactualpatterns

twoforpoints,481 f., 516
T. Drown, 14

stimuli,

323 1„

319 f.,

328-32,347 f.
stimulus intensity, 377 f ., 396

time, 575-7, 602 f.

tonal attribute, 377 f.
upper limit, 332-8, 348
Plateau’s spiral, 591 f,
Positivism, empiricism, 33 f.
Gestalt psymology, 13

time-sense, 577-82, 603

Titchener, 17 f.

Tolman, 18
touch blends, 509-12, 521 f.
visceral patterns, 561-4, 573

perception, 18 1.

visual form, 238-56

sensation, 12 f.,

46 f.

visual modes of appearance, 249 i

9 -phenomenon, 505-8, 606

Wundt, 15 f.

Pressure, adaptation, 500 f ., 519 f

Seemovement.

Apparent

also

Auditory

Color,

localiaation.

Constancy phenomenon. Empiricism, Hunger, Illusions, Kinesthesis,

NaSvisra,

Pressure,

Pain,

PtojeoUon,

Pitch,

Rhyilim,after-sensations, 502-4, 520

end-organs, 470
gradient, 487-90, 617 f.

macroscopic stimuli, 487 1.
microscopic sliinnli, 487-90
spots discriminnblc, 479, 515 f,

Sensation, Size constancy. Small

stimuhition, 487-90, 517 f.

^edfic nerve

energies. Taste,summation, 499, 519

Thirst,
Thermalsensibility.
Time, Time-sense, Tone, Touch,Two-point limen.
Vestibularlonsion, 469 f., 489 f.

sensibility,

Viscerdsensibility.

Vision, Visual space perception,

Weber function

visceral, 546-51, 571

Webor function, 49.5-7, 518 f.
Pressure sense, 465-75, 513 f.
Projection, auitory, 82

Bernstein, 80 f.

Perspective, aerial, 266 f.

quality, 78 f.

cue to distance, 264 f., 304

references, 95

See also Reversible perspective

spatial, 79-82

Fhenakistoscepe, 589 f.

specific nerve energies, 78 f

Phenomenology, brightness, 135 {,,152
experimentalism, 117 i, 124 f,
Cestalt psychology, 33
Goethe, 113, 116, 124
nattvism, 32 f.

tactual, 80, 82,

perception, 19

Pnrkinje, 116-8, 124 f,

tonal attributes, 375 f.
tonal fusion, 861-3

touch, 512, 522
vision, 155-7,

WO"

visual form, M6-52

See also Isomorphism
Proprioception, 526 f., 534 f., 568

Protopathic sensibility, 471-5, 515

Pseudophone, 885
Pseudoscope, 287
Psychometric function, 39-41
Psychophysical axioms, 88-90,

positivism, 13

size con^ancy, 288-99,

visual, 79 f., 82308-11

96,

141 f., 220
Psychophysics,

absolute

limen,

41 f.
average error, 41
constant sdmuD, 38-41
diflerendal limen, 36, 42

36,

.

. .

INDEX OP SUBJECTS
equal category, 40, 51

Savait’s wheel, 334 f., 348

equivalents, 42

Scales, musical, 313-8

Fechncr, 34-7

pitch and budness, 350 f.

.

Feohner function, 36 f., 44 f.

Scientifle progress, dependence on in-

Herbart, 3S

struments, 809
dependence on knowledge, 609 f.
facilitators, 613
individual attitudes, 012
Individual inertia, 611 f,
inhibitore, 600-13
social attitudes, 612 f.
social inertia, 610 f,thought, 608
Secondary criteria of distance, 263-

i.n,d., 36, 38, 43, 52'

639

limits,«37 f.

methods, 36, 51 f.
origins, 34 f.

psychometric function, 30-41
quantity objection, 44 f., 52
references, 50-2
right and wrong eases, 38-41

sense-distance. 37, 42 f.

71, 303-5

sense-ratio, 43 f., 52

ional scales, 350 f.

Semicircular canals, 536-42, 569 f.

Weber function, 34-6, 44 f

Macli-Breuer-Brown theory, 53743. 569
space perception, 888, 398, 541
See also Vestibular sensibility
Sensation, animal psychology, 11 f,

Pupil of eye, accommodation, 275

Purkinje phenomenon, 177-82, 1S5 £.

dark adaptation, 181, 196
rods and cones, 181, 195 f.
visual purple, 181, 196
Purklnje’s

associationism, 8-10, 46

accommodallon,

images,277

attribules, 8,11, 19-27,574

behaviorism, Ilf.

Pythagorean temperament, 315, 318

Bell-Magondie law, 8Berkeley, 5 f.

Quantity objection, 44 f,, 52

cardiac, 564
classiflcalory criteila, 464

Rango of consciousness, 583 f., 604

common attributes, 27

Rectification, eleclrloal, 331 f.

continuum, 10, 38

Reduction, 135, 311

Demooritos, 4 f,

Reflexology, 534, 568

discrimmation, 11-3

Refractory period, 59-02, 68 f,, 92

Empedocles, 4Regression, constancy phenomenon,

empiricism, 3-6, 45

256, 299, 311
Resonance, 324 f ., 347
Resonance theory, see Auditory the-Epburos, 5
excretory, 564
French soliool, 7, 45 f
gastric, 563 f.
Gestalt psydiobgy, 4
HartlCT, 6
Heraentos, 4oryRetinal disparity, 284-8, 308

Reversible

perspective,

fluctuation,

271
shading, 266, 269, 304

history of concept, 3-13

structure, 268-71, 304 f.

Hume, 6hunger, 551-8, 571 f.

Rhythm, early investigations, 583-5,
604
kinesthesls, 586 f 604
objective conditions, 584-6, 604
range of consciousness, 583 f., 604.,

Rotation, see Vestibular sensibility

Interrelation of senses,' 574 f., 602

Ta3.Mill,7f.

Locke, 5magnitude, 44 f,, 52
nerve conduction^ 62-8
neural intensity, 67 f.

Sanson's

images,accommodation,

277 f,
Savtul’s spokes, 334, 348'

number of elements, 10, 46
number of senses, 9 fphenomena, 4

’

,

,

.

INDEX OF SUBJECTS

340
Sensation, oonUmied

handboolis, 438-40, 458

positivism, 12 i,

intcnsiiivc threshold, 442, 459

projection, 78-83

mixture, 443 f.,459
molocuhr weight, 447

Protagoras, 4pulmonary, S64

olfactie,quanta, 38

olfactometer, 441 f., 459

Scottish school, 3, 7, 13 f., 48

periodic series, 447 f.

sexual, 564

441 f.

prism, 445 f., 460

specific nerve energies, 68-73,

94

sense-organ, 440, 458

thirst, SS8-91, 5721.

specific nerve energies, 449

time-sense, 577-82, 603

stimulation, 441 f., 458 f.

unity, 27, 49

stimulus, 440 f ., 458 f.

Watson, Ilf.

Weber function, 442 f., 459

Wundt, 3, 9

Somesthesis,

See also Color, Kinesthesis, Perception, Psychophysics, Smell, Specificnerveenergies.

Taste,

Deepseesensibility,

Hunger,Kinesthesis,
Thirst,Touch, Vestibular sensibility.
Visceral sensibility

Tone, Touch, Vestibular sensi-

Sono, 351

bility, Visceral sensibility, Vision,

Sound, conduction, 321 f., 347

Weber limctlon
Sonsationism, 5-10

See also Sensation

Fourier analysis, 325-8, 347

harmonics, 324 b, 347

Ohm’s law, 326-8, 347

Sense-distance, 37, 42 {,piUh, 322-4, 346 1,

Sense-ratio, 43 f „ 52

rosimuiico, 324 1,, 347

Sensory centers, 75-8, 94 f,

velocity, 322, 847

Sensory circles, 476 £., 515

Smmd cage, 385 b

Sexual sensation, 564

Specific

Shading, cue to distance, 265 b, 304

nerve

Shape constancy, 258
Siren, 319 f., 3281., 847
Size, apparent, 289
309

Bell,

Size constancy, alley problem, 290,

concept, 69

adequate70

cerebral localization, 74-8
color,

mb

consequences, 73 f

294-8, 310
animals, 296 f., 310
children, 297,

eiU’Tgies,

sliiradalion, 71, 04

310

extension to qualities, 72-4, 94

Helmholtz, 73

concept, 256, 303, 310 f.

Toll.

determinants, 297 f.

Locke, 69 f.

early observations, 290-3

projection, 78 f.

Emmert's law, 292 f., 310
law, 256
Martins, 293 f.
phenomenology, 298 f., 303
regression, 299

references, 94

unconscious inference, 299, 303
Smell, adaptation, 443, 459

Muller, 70-2, 94

sensory conduction, 63 f.
smell, 449
tactual, 467-71, 513 f.
taste, 454 f.

tones, 403 b, 408
Young, 70

benzene ring, 448 f
cliemistry, 446-8, 460

Spectra, after-images, 158, 160

classification, 444-6, 459 f

Speech center, 75
Split movement, 597
Statio sense, 540, 569

compensation, 443 1., 459

degenerate sense, 460

dlmorhinic stimijation, 444

Spectrum, energy, 178 b, 195

See also Vestibular sensibility

differential thresho'd, 442 f., 459

Stereoscope, 285-7, 308

dirhinlc stimulation. 444

Stereoscopy, 282-8, 301 b, 307 f,

.

.

INDEX OF SUBJECTS
Stralloii’s experiment, 237

Stroboscope, 680-91, 605

Stumpf’s paradox, 10, 46

Summation, 469,
518-20498 1., 502

Threshold, see Psychophysics, Smell,

Summation tone, 854.Superposition, cue to distance, 264

Tactual localization, see Touch
Tactual sensibility, see Touch
Talbot-Plateau law, 145, 154
Tartini's tones,

641

d^ydration, 558-61, 572 f.
dryness of mouth, 558-61, 572 f.
general sensation, 560 f., 572 f.
salivation, 560 f., 572 f.

352 f

892

Taste, adaptation, 457, 461

buds, 4501., 4601.
clremislry, 455-7, 461

461
460

classification, 453-5,

handbooks, 440
ionization, 456

Taste, Tone, Touch, Vision
Timbre, 35*7-9, 393
fusion, 359 f.
Time, ^nscious present, 576, 602
given in experience, 576 f., 603
perceived, 575 h, 602 f.
‘Hme-sense, apparatus, 581 f.
errors of estimation, 570-81, 603

indifference point, 578-82, 603

long durations, 603 f
units of duration, 580-2
Weber-function, 577-9, 60S
Tonality, tonal attributes, 380, 896 f.

Tone, appnraUis, 328-32, 347 f.

modalities, 454 f.

attributes, 375-81, 306 f.

papillae, 451

audibility curve, 336-8, 348 f.

primary qualities, 453-5, 461

audiogram, 837 f., 348 f.

reaciitin time, 458, 461 f.

auinl harmonics, 858 f., 303

sense-organs, 450 {.

beats, 852-7, 302, 408

sensitivity of tongue, 452, 461

brightness, 378, 396

spoolflc nervo energies, 45A f.

combination tones, S52-7, 392 f„
408
consonance, 360

tatrahcclron, 455

Wtibor function, 458, 462
Tclestcrcoscopc, 287

density, 880, 897

Temperament, musical, 316-8, 346
Temperature sense, see Tliermal sen-difference tones, 852-7, 892 f.
distortion, 355-7

Fourien analysis, 325-8, 347

sibility

Tendinous sensation,
Telrachords, 314 f.

Thermal noise, 365, 394
Thermal sensibility, 405-75, 513 f.
adaptation, 498, 500, 519
after-sensations, 503 f., 520
cold receptors, 470 f., 614 f.
heat, 504-9, 520
Hcrlng’s tlieory, 491 f., 518
fhysimogical zero, 491
518
stimulation, 490-3, 518
summation, 498 f 519,,

theories, 490-3, 518
visceral, 540-51, 571

von Fr^s diagram, 605
warmth receptors, 470 f., 514 f.

Weber function, 497 f., 519
Weber's theory, 490-2, 618
Thermionic valves, tonal stimuli, 3302, 348
Thirst, appetitive, 559-81, 663, 578

farioii,

859-62,360;

intervals,

898 f.;

diatoniolaws,

360 f.;

Stumpf, 800-2
harmonics, 824 f., 347

hlgh^t pitch, 33^8, 348
inteusitive threshold, 336-9,
intensity,

differential

348 f.

sensitivity,

342-6. 850
intervals, characteristics,

361 £.

isophonlc contours, 377
looalizatioD, 884-91, 3Q7 f.

budness, 877 f.; number
345, 350
lowest pitcli, 382-8, 348
masking, 866-7, 3^f.
modulation, 856 f.

Ohm’s law, 326-8, 847
pitch, 822-4, 346 f., 377 f.; differential senritlvlly, 339-42, 349 f.;

numberj’n.d.,

scales, 313-8

341 f.,

849 f.;,.

INDEX OF SUBJECTS

642

heat, 504-9, 520 f.; Weber func-

Tone, continued
piteli standards, 319-21

tion,

497 f., 519

pure, 358

tliormal stiiuulalion, 490-'3, 518

quanta, 345 1., 350

thermal thcorihs, 490-3, 518

H. Koenig, 320-31, 347

tickle,scales of pitch and loudness, 350 f.

two-point

sensitivity, 336-9,

34Sf.

510 f., 521 f.
limen,,

475-85,515 f.;

criteria of ‘two,’ 482, 516; cnor.

spedfle nerve energies, 403 f., 408

of locnlization,summation tone, 354
timbre, 357-0, 393
tonality, 880, 396 f,

tigue,

481 f.,

477 f.,

515;

ments,

vocallty, 367-75, 380, 398

patterns,

479 f., 516; perceptual
481 f., 516; practice,

volume, 377-9, 396

fa-516; mobility,
paradoxical judg-

480-2, 516

Weber function, 342-6, 350 f.
See aha Auditory theory
519 f.
Touch, adaptation, 500
after-sensations, 501-4, 520

apparent

484 f.,, 517;

movement,

VexirfclJer, 479 f

von Frey, 469-71, 475
Weber, 465 f., 513

wet 509-11, 521

599-601,

Transpusillon, 254 f., 262

Tuning fork, 310 f., 328-31, 347

606 f.

Two-point limen, 475' 85, 515 f.

blends, 509-12, 5211.

clammy, 522, 511 f.
deep sensibility, 471-3, 523 f., 585
differentiation, 465-75, 513
end-organs, 469-71, 475, 514

critci'ia of 'two,'

epioltic sousiblllly, 471-5, 515

pnrado.\ical judgments, 479 1., 510

hard-soft, 511,

522

482, 510

crrtir of localization, 484 f,, 517

fnlignc, 481 1'., 516

mobility, 477 f,, 515

perccptiml paltnnis, 481 f., 516

Head’s theory, 471-5, 515

practice, 480-2, 516

localization, anchorage poinLs, 486,

517; sensory cues, 483 f.; visual-

Unity of souses, 27, 49

ization, 485 f., 517

nerve injury, 471-5, 515
pain, 465-75, 513 f.;

Valve, tlicrmionlc, 330-2, .348

stimulation,

Vatcr-Pacini curjniscles, .530, 566

493-5, SIS; von ftey’s tlioory,

Vertigo, .535 f., 542-4, 564, 508

494 f.

Vestibular

paradonical cold, 469, 492 f., 5047, 518

paradoxical warmth, 506 f., 520 f.
pressure, 465-75, 513 f.; gradient,487-90,517 f.;

Ilmen

gauge,

487 f.;
macroscopic
stimuli,
487 f.j microscepic stimuli, 48790; stimulus, 487-90, 517 f.; tension, 489 f.; Weber function,
485-7, 518 f.

protopathlc sensibility, 471-5, 515
sensory circles, 478 f., 515
sensory spots, 467-71, 475, 513 f;
discriminablc, 479, 516 fsmooth-rough, 511, 522
sticky, 511,

.sensibility,522

summation, 469, 490-3,
502 f„ 518-20 ->498 f.,

thermal sensibility; 465-75, 513 f.jadaptation,

536,530,5431,, ,570
after-sensations,

536, 539, 543 f.,

570
anesthetic, 543,

570

aviation, 543

central factors, 544, 570

deaf mutes, 542 f„ 570
Flourens' experiments, 536-9''

function of macula, 540 f,

Mach-Breuer-Brown theory, 53743, 569
Mach's experiments, 537 f., 569
quality of sensation, 542, 544, 570
reflex sense, 542, 544, 570
rotation, 536-9, 569 f.
semicircular canals, 636-42, 569 f.
static sense, 540, 569
tliermal stimulation, 538
vertigo, 535 f,, 542-4, 584, 568

»,

INDEX OF SUBJECTS
visual purple, 181, 190

Visceral sensibility, appetite, 551-3,

Weber function, 130-9, 152 f.

557 f., 562 f., 572
cardiac oppression, 564
cold, 545-51, 571

See also Adaptation, Color, Colorblindness, Color niixtiira, Contrast, Purkinje phenomenon. Vis-

excretory ngeds ana processes, 564
gastric emptiness,,

ual space perception

Visual space perception, accommo-

563

gastric repletion, 563

dation, function, 109 f„

hungenj 551-8, 571 f.

272-4,

insensi^ity, 540-8, 570 f.

278 f.,
305 f.

localization, 547, 549 i,nausea, 563 f.

122 f.,
302 f.;
mechanism,306 f.; theories, 274-8,

alley problem, 290, 294-6, 310

need vs. sensation, 561-3
pain, 540-51, 571

apparent size, 280 f., 300

perceptual patterns, 561-4, 573

binocular parallax, 282-5, 307 f.

pressure, 546-51, 571

convergence,referred pains, 547
sensitivity,

548-51, 570 f.

558-61, 572 f.

Visibility curve, 176-82,

194-0

Vision, accommodation, 109 f., 122 f.

adaptation, 160-4
after-images, 157-60, 190 f.; nega-

158 f.; positive, 157 f.

color blindness, 182-90
contrast, 165-71, 192 f.

dark adaptation, 181, 196
Greeks, 97 f.
Holmholtz, 119
indirect, 171-6, 193 f.
intunsilive j.n.d., 130-9
lens, 99 f., 222 f., 276-9, 306 f.

lens as receptor, 69
light, 98-101,

121 f.

luminosity, 176-82, 104-6

Masson disk, 137 f.

modem research, 120 f., 125
nineteenth century, 116-21, 124 f.

phenomenology, 113, 116-8, 124 £.,165-7, 190
pliotopia, 182, 196
Porterfield, 108, 122 f.
Purkinie phenomenon, 118, 177-83,

195 f.
retiral image, 100, 222 f., 257; in-version, 223-5,

scotopia, 177-82,

corresponding

271 f.,

points,226-30,257 f.
morphism,

warmth, 540-51, 571
See also Ilungor, Tliiist

tivo,function,

deptli, dynamics, 299-303, 311 ; iso-sufEccatlan, 564
thirst,Aubert-Forster law, 249, 309 f

302 f., 305, 307

sexual needs and processes, 564,

643

VexirfoUer, 479 f., 516

237 f.
196

sensitivity, 176-82, 194-6; rods andcones, 179-81, 195

303;

stereoscopic,

282-8, SOU., 3071

accommodation, 272-82,
302 f., 305-7; aerial perspoolivo,
206 f.; convergence, 271 1'., 27082, 302 f., 305. 307; filled andempty, 267; light and sliadc,
265 1, 269, 304; paxallax ofmovemonl, 207 f., 304; perspootive, 264 f., 304; rcvcrsiblo por.spectivo 208-71, 304 f.; second-

distance,

ary criteria, 263-71, 303-5;

size,

264 r. 288-09, 308-11; superposition, 264
Donders’ law, 230-2, 258
double representation, 300 f.
Fmmerl's law, 292 f., 310
empiricism, 233-7, 258 f.
eye-movements, 230-3, 258
form, 238-56, 261 f.; Gestalt laws,
253-5, 261 f.; Schumann, 247 f.;
tridimensional, 299-803, 811
form-quality, 246
horopter, 226-30, 257 f.
illusions, 238-45, 260 f.; reversible
perspective, 268-71, 304 f.
Listings law, 230-2, 258
local signs, 232-6, 288
localization, 236 f.
moon illusion, 267
nativism, 283-7, 258 f.

.

,

.

,

INDEX OP SUBJECTS

644

Visual space perception, continued
retinal imago, 232-5, 257;

inver-

pitches, 371), ,380
theories, 368, 371-5,3951.

sion, 223-S, 237 1,

reversible

octal c rclalicms, 372, 374

perspective,

308-71,304 f.
singleness of vision, 226-9, 257 f.
size,

223 f

Walor-liill illiialon, 592 1.

Webersize constancy, 288-99, 308-11

stereoscopy,

Wimnth, see Tfferinal^scnsihility

282-8,

307 t.ifield

theory. 301 f,

tunetion,louiluiss,

3501,
pressmo, 49,5-7, 518 1.

153

vertical primacy, 230, 260

fliane, 139,

See also Illusions, Size constancy

smell, 442 f., 459

Vocality, tonal attribute, 380, 396

stellar magnitudes,

Volley theory, 421-4, 435

taste, 458,

Volume, tonal attiibute, 377-9, 396
Von Frey hair, 488 ftime-sense, .577-9, 603

Vowels, formants, 372 f

vision, 136-9,

methods, 309, 371-5, 395 f.
noise,

373

153

462

temperature, 407 f„ 519

152 f.

Sec oho Psychophysics

Wcver-Biay ellcel, 420-3, 4.35

343-8,