The sun., 1901-07-07
ACT OF THE EYE IN SEEING.
PROP. DOD0Es DTsCovERY o. A VIEW
LAW or vISfON.

Law or vIsI0N.
Expertueuts At Wesleyan Unfversisy Thaa oAsw
That the Eye 20 See Any object Msss 1s-
msia at Rest-Dtmeslttes sf ths lnvsstags-
fien-Ths Eyss hovsmsnss.
MIppLErowN. Conn July a-Prof Ray
mond Dodge OF Wesleyan University In
shh city was asked few days ago to tell
in detail shout the new law Of vision dis
covered by him and his associates At the
time Prof Dodge happened TO be'in the
midst OF a critical inspection Of examina-
tion papers Of students Of tho university.
end he was therefore unable TO comply with
- request; but he referred the reporter
= some papers which he had recently pre-
pared on this subject and In which he said
oil the desired information could be OBJ
tained.
Several years ago Prof. Dodge. In ssso-
citation with Prof Benno Erdmann, then
Of the University OF Halle. Prussia. brought
forward the theory that the eyes do not
move regularly over q page OF reading
matter, but make series Of distinct pauses
@ they pass over each printed line He
sought to show by experiment that the
eyes actually $50 tho words only during
these pauses. This new theory was dis
cusssd widely and the conclusions OF the
two investigators were Questioned BY
well-mown authorities both here and
ohroad During the past year Prof. Dodge
Aas definitely established by experiments
hh theory that the eyes when In motion
can distinguish nothing In any compiler neld
Of vision over which they roam
In other words, In order to 80 any object
ct rest, the eye must remain motionless.
looking at some definite part Of tho object
for q reasonable length Of time. Prof.
Dodge says In the Psychological Rsvisv.
describing his experiments. that one
sndesvos to distinguish by mere intro
spection between visual data acquired
during tho eye movements and those OF
the hxation pauses, an insurmountabls
dificulty will be discovered. namely, all
self-observation OF the eye movements
and hxation pauses 70 utterly untrust-
worthy. He goes on to say:
Il have no confldence In my own 5udg-
ment In this matter unless verified by the
direct observation OF an assistant or by
some form or registration. The trained
psychologist is unable TO give reliable
account Of points flxated at these stops.
or even Of their number by mere self
IL quite unable TO tell whether given eye
movement was broken by a stop or not.
In the experiments carried on during
the past yoar at Wesleyan BY Prof. Dodge
and his student assistants. direct observa,,
ton by an assistant. the simplest and
The assistant was not allowed TO attempt
to follow any point Of the moving eyeball
In its excursions but had to fix upon some
point OF the lid or eyelash which was rela-
lively at rest. In some cases II was neoes-
sary to construct an artificial nxation
these precautions II IL not impossible that
even trained investigators are led into
believing they see during eye movement
that which is really seen during an un-
noticed fXstion pause.
s. sU%TS H4nSs Of eFS, IN he bos 5odc
"is the familiar difficulty Of distinguishing
the centrally conditioned elements OF q
percept from those which are peripherelly
conditioned. IL 10 perhaps most widely
known as the proofreaders fallacy. A
striking s1ampse "a pie n S,vs Pens5 With VIZ &.
Kaleidoscope. When q long word or
phrase is grasped even those parts eeem
TO stand out clear and distinct, which IN
continuous exposure shows to have been
go far out Of the field Of direct vision a. to
present hopelessly indistinct blur u,
Prof Dodge and Prof. Erdmann made the
first experiments TO determine how much
of a complex field Of vision could be appre-
hended during the uninterrupted move
ments Of the eye, In an attempt TO explain
the meaning of those strangely rhythmic
palises OF the eye in reading every page OF
printed matter. 1t was then the two pro-
fessors chanced upon the observation that
when the head was held perfectly still one
could never catch ones own eyes moving
In mirror
One may watch ones eye a. closely a.
possible. even with the aid Of q concave
reflector. but whether one looks from one
eye to the other or from some more distant
object to ones own eyes, the eyes may be
seen now In one position and now In another.
but never In motion. Then Prof. Dodge
'ayisi; 'ayii on. s,ates tn. beginning o, . lin.
on a page OF reading matter the words
In the middle OF the line will be altogether
illegibe. Tho same will be true when the
right end Of the line Is fixed upon. though
the general character OF the line is seen
from both fxation points; II we look
quickly from one end Of the line to the
other 1t viii seem as though We saw the
letters and words during the movement
but an analysis Of what was seen will show
that we have not seen particle more than
we saw from one fiIauon point or the other
If the observer takes the precaution TO
have some one watch his eyes he will find
that what in sef-observaton passes for
a slow movement Of the eyes Ia In reality
broken by one or more clearly defined
full stops. An assistant watching the OBJ
servers eyes will be able 20 predict with
absolute correctness when the middle
Of the line was clearly seem and when not
by the presence OF absence OF these full
stops II simple letter or figure is placed
between two fxation points 30 as to be
irrecognizable from both. no eye move
ment Ia found TO make It clear which does
not show a full stop between them. Four
or fve lines, close enough together to pre-
vent counting, may be substituted for the
letter with the same result This Is moro
easily explicable when the lines are per-
pendioular TO the line Of movement, but
the same results also obtain when they
are parallel
The possibility early occurred to Prof.
Dodge that the movement OF the aye
might condition momentary visional
anRsthesia. This seemed to be supported
by the fading Of after images during eye
hypothesis u. however. false according
10 Prof Dodge. II Is rendered improbable,
he says, by the perception OF long streaks
OF light seen when the retina moves across
the Image Of a bright point OF light on a
dark ground. II Is disproved by the fol-
lowing experiment:
A disk OF black cardboard fourteen
inches In diameter In which a circle OF
one-eighth inch round holes one-half
inch apart had been punched close TO the
periphery all round was made to revolve
1T such velocity that. while the light
from the holes fused TO bright. circle