STANFORD RESEARCH INSTITUTE
Menlo Park, California 94025
U.S.A.
12 March 1974
Progress Report No.
Covering the Period 28 January to
1 March 1974
Stanford Research Institute Project 3183
PERCEPTUAL AUGMENTATION TECHNIQUES
by
Harold E. Puthoff
Client Private
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I
OBJECTIVE
The purpose
of
the program is
to determine
the characteristics
of
those perceptual modalities
through which individuals obtain information
about their environment,
wherein such information is not presented to
any known sense.
The program is divided into two categories
of investigation of
approximately equal effort,
applied research and basic research.
The
purpose
of
the applied research effort
is
to explore experimentally
the potential for applications of perceptual abilities
of interest,
with special attention given
to accuracy and reliability.
The purpose
of
the basic research effort
is
to identify the characteristics
of
individuals possessing such abilities,
and
to identify neurophysiological
correlates
and basic mechanisms involved in such functioning.
II
PROGRESS DURING THE REPORTING PERIOD
A,
Applied Research
1,
Remote Viewing
A number
of efforts were begun with respect
to obtaining
further information concerning remote viewing phenomena.
First,
an
experiment has been designed in consultation with
SRI psychologists
which will yield precise statistical data as
to discrimination ability.
Ten sites known
to the
subject
are
to be visited
in random sequence by
a
target demarcation
team.
The subject must then make
a choice
as
to
which site
is being visited,
in addition to providing descriptive material
for content analysis.
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B
.
Basic Research
1.
Testing Program
During
the first month
of
this program,
the Wechsler Adult
Intelligence Scale
(WAIS)
instrument was administered by
to three subjects screened in other
programs
as being gifted in
the area of paranormal perception.
They are
Mr, Patrick H. Price,
screened for remote viewing ability,
Mrs,
Hella Hammid,
screened for EEG correlates
to remote
stimuli,
and Mr. Duane Elgin,
screened for high scoring response
to
a random target generator.
Further
in-depth interviewing of
the first
two subjects was carried out by
technical representatives when completed.
On the basis of discussion with technical representative,
SRI representatives have consulted with a number
of
Bay Area neurophysiologists concerning administration of
the Halstead-
Reitan
(H-R) Neuropsychology Test Battery,
Those contacted include
Dr.
Karl Pribram of
the Stanford Medical School,
Dr,
Robert Ornstein
of
the Langley-Porter Neuropsychiatric Clinic,
and Dr. Donald Lim of
the Veteran's Administration Hospital in Palo Alto.
To date satisfactory
arrangements for administration of
the H-R instrument have not yet been
made,
as only the
latter facility has personnel experienced in its
administration,
but not ordinarily available for subcontracted consulting.
The
three individuals named above have,
however,
agreed to help
locate
an appropriate individual
or facility to carry out
such testing so no
difficulty is anticipated in meeting this requirement.
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A measure
of
the visual acuity of
one subject
(P.P.)
was
obtained utilizing one
of
the instruments available in the optics
group
of
the Electronics
and Bioengineering Laboratory of
SRI,
The
measurement method involves forced-choice discrimination on the part
of
the subject between alternate zero and finite-contrast grating images,
for each of
a number
of spatial-frequency gratings,
(See Appendix
II*)
The
system,
which
is automated,
tracks and records
the subject
f s
forced-choice responses
to yield
a curve of
threshold
(75% correct choice)
contrast sensitivity as
a function
of
spatial frequency.
As might be
expected,
higher contrast
is required
at
the
low and high frequency
tails
of
the distribution,
as compared with the middle
range,
to
discriminate between grating and uniform images.
The purpose
of
the
test with regard
to our program was
to determine whether
a subject
possessing
an unusual ability
to view remote stimuli
also possessed
an
unusual visual acuity response in a threshold~determining instrument,
either because
of unusual acuity in the ordinary sense,
or through the
use
of
an extraordinary ability to discriminate between
a target
and
a
blank under conditions
of vanishingly-small information content.
The resultant curve
lay within the range
of expected human
variation indicating no unusual response activity,
2,
Measurement Program
A 10-channel polygraph facility under
the direction of
Dr.
Jerry Lukas
of
the Sensory Sciences Research Center has been brought
into the program and certain functions tailored
to our specification.
The facility will
be used initially to monitor GSR,
blood flow
(plethysmograph)
,
and EEG activity of
subjects carrying out
tasks
involving perception of
remote stimuli.
For our purposes,
the display
of raw data has been augmented by
a computer program which has been
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written and debugged
to provide on-line 5-second averages
of EEG activity
in the
theta,
alpha,
and beta bands.
Discussions
are now in progress
on experimental protocols
to be employed in the utilization of
this
facility.
EEG data taken prior to this program,
but unanalyzed,
has been
subjected to analysis in an effort to determine whether
a particular
protocol was
a viable instrument for defining correlates
of remote
perception.
The description of
the experiment
and the results
of
the
analysis
is given in the EEG section
of
a paper submitted for publication
to Nature ,
given here
as Appendix
I
.
In an effort
to determine
the effects of motivation on
paranormal functioning,
the following test procedure has been initiated.
One subject
(P.P.) has completed 7075 trials on guessing the state
of
a
four-stage electronic random target generator without monetary reward
being associated with the scoring,
and is now repeating
the series with
a monetary reward scaled to scoring.
Upon completion of
the series,
the results will be analyzed to determine whether the difference between
scoring under the two conditions
is significant.
The reward system,
shown in Table
1,
is scaled linearly with difficulty.
Table
REWARD SYSTEM FOR SCORING ON 25-TRIAL RUN,
P=l/4 PER TRIAL
Nr. hits/25-trial run,N
Prob.
of
at least N hits
Reward
0.071
$
0.030
0.010
0.0034
0.00092
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FIGURE CAPTIONS
1.
Target pictures
and responses
drawn by Uri Geller under shielded
conditions
.
2.
Computer drawings
and
responses
drawn by Uri Geller.
a.
Computer drawing stored on video display
b.
Computer drawing stored
in computer memory only
c.
Computer drawing stored on video
display with zero intensity
3.
Occipital
EEG spectra,
to
20 Hz,
for one subject
(H.H.)
acting as
receiver,
showing amplitude changes
in
the 9-11
Hz band
as
a
function of
strobe
frequency.
Three cases:
0,
6,
and
flashes per
second
(12
trial averages)
.
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INTRODUCTION
In this paper we present
results
of experiments
suggesting
the
existence of one or more perceptual modalities
through which individuals
obtain information about
their environment,
wherein
this information
is
not presented
to
any known
sense.
Such perceptual abilities
are often
1-3
considered
to be paranormal.
The literature
in
the
field
coupled with
our own observations have
led
us
to conclude
that such abilities
can be
studied under
laboratory conditions.
The phenomena we have investigated most extensively pertain
to
the
ability of certain individuals
to describe graphical material
or remote
scenes
shielded against ordinary perception.
In addition,
we also performed
pilot studies
to determine
if
elec troencephalographic
(EEG)
recordings
might
indicate perception
of
remote happenings even
in
the absence
of
correct overt responses.
In
these experiments we concentrated on what we considered
to be our
primary responsibility—namely ,
to resolve under conditions
as unambiguous
as possible
the basic issue
of whether
a certain class
of paranormal
perception phenomena exists.
Therefore,
we conducted our experiments with
sufficient
control,
utilizing visual,
acoustic,
and electrical shielding,
to ensure
that, all conventional paths
of
sensory
input were blocked.
At
all
times we were vigilant
in
the design
of our experiments
to
take
measures
to prevent sensory leakage and
to prevent deception, whether
intentional or unintentional,
on
the part
of
our subjects.
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The. overall
goal
of our research program Is
the determination of
the
laws underlying
these phenomena.
That
is,
our goal
is not just
to catalog
interesting events,
but rather
to uncover patterns
of cause-effect
rela-
tionships
that
lend themselves
to analysis
and hypothesis
in the
forms
with which we are familiar
in scientific study.
The results presented
here constitute a first
step
toward
that
goal,
in that we have established
under known conditions
a data base from which departures
as
a function
of
physical and psychological variables can be studied
in future work.
in this paper we describe three related experiments which we consider
to represent
a single ability exhibiting different rates
of
information
transmission.
First,
we conducted experiments with Mr.
Uri Geller
in
which we examined his
ability, while located
in an electrically shielded
room,
to
reproduce
target pictures drawn by experimenters
located at remote
locations.
Second, we conducted double-blind experiments with
two
individuals, Mr.
Ingo
Swann and Mr.
Pat Price,
in which we measured their
ability
to describe remote outdoor scenes many miles from their physical
location.
Finally, we conducted preliminary tests using electroencephalo-
grams
(EEG)
,
in which subjects were asked
to perceive whether
a remote
light was flashing,
and
to determine whether a subject could perceive
the
presence of
the light,
even
if only at
a noncognitive level
of
awareness.
REMOTE PERCEPTION OF GRAPHIC MATERIAL
We describe here
a series
of experiments
in paranormal perception
with a
27 year old Israeli subject,
Uri Geller.
In preliminary testing
Mr.
Geller apparently demonstrated an ability
to reproduce simple pictures
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in order
to eliminate
the possibility
of pre-experiment
target
forcing,
Mr.
Geller was kept
ignorant
as
to
the
identity
of
the person selecting
the
target and
as
to
the method of
target selection.
Mr.
Geller
T s
task
was
then
to reproduce with pen on paper
the line drawing being generated
by
the experimenters
at
the
target location.
Following
a period
of effort
ranging from a
few minutes
to half
an hour,
Mr.
Geller either passed
(when he did not feel confident)
or indicated he was
ready
to submit
a
drawing
to
the experimenters,
in which case
the drawing was
collected
before Mr.
Geller was permitted
to see
the
target.
In order
to prevent
sensory cueing of
the
target information,
Experiments
through
10 were carried
out using
a shielded room in
SRI
T s
facility
for EEG research.
The
degree
of acoustic and visual
isolation
provided
for
this
experiment
is
that afforded by
a double-walled steel
room,
locked by means
of
an inner and outer door,
each
of which
is secured
with
a
ref rigerator- type locking mechanism.
The person inside
the
room
is
continuously monitored by means
of
a one-way audio monitor.
The
target picture was never discussed by
the experimenters after
the picture
was
drawn
or brought near
the shielded
room.
In our detailed examination
of
the shielded room and
the protocol used
in these experiments,
no sensory
leakage has been
found.
The conditions and results
for
the
ten experiments carried out
in
the
shielded
room are displayed
in Table
1.
As
indicated
in
the Table,
all
experiments,
except
Experiments
4 and
5, were conducted with Mr.
Geller
closeted inside
the shielded room.
In Experiments
4 and
5,
the procedure
was reversed— i.e.,
the
target was
located inside
the shielded room, with
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(line drawings) which had been drawn and placed
in opaque sealed envelopes
which Mr.
Geller was not permitted
to handle.
However,
since each of
the targets was known
to at least
one experimenter
in
the room with
Mr.
Geller,
it was not possible on
the basis
of
the preliminary testing
to discriminate between Mr.
Geller
* s
direct perception of envelope
contents
and perception via some mechanism involving
the experimenters, whether
paranormal
or subliminal.
Therefore,
an experimental study was undertaken
to examine
the
phenomenon under conditions
specifically designed
to eliminate all
conventional information channels,
overt
or subliminal.
This was accomplished
by separating Mr.
Geller from both
the
target material and anyone knowledgeable
of
the
target material,
as
in the recent experiments by Musso
and Granero
.
The
first part
of
the study consisted
of
a series
of
thirteen separate
drawing experiments
carried out over
a seven day period.
The thirteen-
experiment data set
constitutes
the entire
set
of consecutive experiments
carried out
in
the time available
for
the
study, with no experiments
deleted.
The protocol
for
the experiments was
as
follows:
At
the beginning
of
the experiment
either Mr.
Geller
or
the experimenters
entered
a shielded
room so
that
from
that
time
forward Mr.
Geller was
at
all
times visually,
acoustically,
and electrically shielded from personnel
and material
at
the
target
location.
Only following Mr.
Geller
T s
isolation from the experimenters
was
a target chosen and drawn,
a procedure designed
to eliminate pre-
experiment
cueing.
The method of target selection involved random
procedures,
such
as randomly opening
a dictionary and selecting
the
first
word describing an object
that could reasonably be
drawn.
Furthermore,
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TABLE
1.
SUMMARY:
REMOTE PERCEPTION OF GRAPHIC MATERIAL
Experiment
Date
Geller Location
Target Location
Target
Figure
i
8/4/73
Shielded room #ia
Adjacent room
(4.1 m)^
Firecracker
la
8/4/73
Shielded room #i
Adjacent room
(4.1 m)
Grapes
lb
8/5/73
Shielded room #i
Office
(475 m)
Devil
lc
8/5/73
Room adjacent
shielded room
to
#1
Shielded room #1
(3.2 m)
Solar system
Id
8/6/73
Room adjacent
shielded room
to
#1
Shielded room #1
(3.2 m)
Rabbit
No drawing
8/7/73
Shielded room #1
Adjacent room
(4.1 m)
Tree
No drawing
8/7/73
Shielded room #1
Adjacent room
(4.1 m)
Envelope
No drawing
Ln
8/8/73
Shielded room #1
Remote room
(6.75 m)
Camel
le
8/8/73
Shielded room #1
Adjacent room
(4.1 m)
Bridge
If
8/8/73
Shielded room #1
Adjacent room
(4.1 m)
Seagull
lg
8/9/73
Shielded room #2°
Computer
(54 m)
Kite
(computer CRT)
2a
8/10/73
Shielded room #2
Computer
(54 m)
Church
(computer
memory)
2b
8/10/73
Shielded room #2
Computer
(54 m)
Arrow through heart
2c
(computer
CRT,
zero
intensity)
aEEG Facility shielded room
(see
text)
Perceiver-target distances measured in meters,
c SRI Radio Systems Laboratory shielded room
(see
text)
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Mr.
Ge.LI.er on
the outside
in an adjacent
room.
For those experiments
in
which Mr.
Geller was inside
the shielded room,
the
target location was
in
an adjacent room at
a distance of about
4 meters,
except
for Experiments
3 and
8,
in which
the
target
locations were,
respectively,
an office
at
a distance of
475 meters
and
a room down
the hall at
a distance
of about
7 meters
.
In Experiment
1, the object drawn
on
the basis
of random dictionary
so. Lection was
a firecracker,
shown
in Fig.
1(a).
Mr.
Geller
T s
immediate
verbal response via
the audio monitor was
that he saw
"a cylinder with
noise coming out
of
it."
He made
two responses
to
the
target,
also shown
in
Fig.
1(a).
In Experiment
2,
the
target—also chosen by random dictionary selection-
was
a cluster
of
grapes.
Mr.
Geller said that he was
quite certain
that
he. had
the picture.
Both
the
target picture and Mr.
Geller
T s
response
have
24 grapes
in
the cluster
(Fig.
1(b)).
In Experiment
3,
Mr.
Geller was
locked
in
the shielded room with one
experimenter outside
as
a monitor while
the
target was
drawn
in another
building 475 meters
away.
The
target,
again randomly selected from the
dictionary,
was
a devil
(Fig.
1(c)).
Mr.
Geller spent
30 minutes
on his
drawing and expressed considerable difficulty
in getting
the
target.
The
results
are interesting from
the standpoint
of possible insight
into
the
process
that
they provide.
His
drawings
consisted of representations
of
Biblical symbology,
including
the
"Moses tablets,"
an apple with
a worm,
a snake,
and
a concluding composite picture with
the
tablets
on
top
of
the world and
the
trident outside.
Of
these
only
the
trident corresponds
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v
\
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UNDER
SHIELDED
CONDITIONS
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directly
to
an element
in
the
target drawing.
One
is
led
to speculate
that
the Biblical elements
in these
three drawings are perhaps associational
material
triggered by
the
target.
The
target picture
for Experiment
4 was drawn by
an experimenter
while he was
inside
the shielded
room, with Mr.
Geller outside the room
with another experimenter.
In this
case
the
target
(Fig.
1(d))
was
a
representation
of
the solar
system.
Mr.
Geller
T s response
to
the
target
while outside
the room coincides
quite well with
the
target
drawing.
In Experiment
5,
the person-to-person link was
eliminated by arranging
for
a scientist outside
the usual experimental
group
to draw a picture,
lock
it
in
the shielded room before Mr.
Geller
T s arrival
at
SRI,
and
leave
the
area.
Mr.
Geller was
then led by
the experimenters
to
the
shielded room and asked
to draw the picture
inside
the
room.
He said
that
he
got no clear impression and
therefore did not
submit
a drawing.
The
elimination of
the person-to-person link was examined further
in
the
second series
of experiments with
this
subject, which
is described
later.
Experiments
6 and
7 were carried out while we recorded Mr.
Geller
! s
EEG during his
efforts
to perceive
the target pictures.
The target pictures
were,
respectively,
a
tree and an envelope.
He
found
it difficult
to hold
adequately still
for good EEG records,
said
that
the experienced difficulty
in getting impressions
of
the. targets,
and again submitted no
drawings.
For Experiment
8,
the
target picture was
a camel
and Mr.
Geller
T s
response was
a horse
(Fig.
1(e)).
In Experiment
9,
the
target was
a bridge.
Mr.
Geller
f s drawing bears
some resemblance
to
the
target
(Fig.
1(f)),
but
before
seeing
the
target picture
he stated
that he did not know what
the
picture was.
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At
the beginning
of Experiment
10,
Mr.
Geller expressed extreme
confidence and entered
the shielded room.
The target
then chosen for
Experiment
10 was
a bird
in
flight.
Mr.
Geller
said
almost immediately,
via
the audio monitor
in
the shielded
room,
that he
saw
a swan flying over
a hill and
that he was
sure
that his
drawing was correct
(Fig.
1(g)).
Experiments
through
13 were carried out
in SRI
1 s Engineering
Building,
to make use
of
the computer
facilities available
there.
For
these experiments,
Mr.
Geller was secured in
a double-walled,
copper-screen
Faraday .cage
54 meters
down
the hall
and around
the corner
from the
computer
room.
For Experiment
11,
a picture
of
a kite was
drawn by one of
the.
experimenters
on
the
face
of
a cathode ray tube display screen,
driven
by the computers graphics program.
Mr.
Geller
T s
response,
shown
in
Fig.
2(a), was
a square with diagonals.
For Experiment
12,
a picture
of
a church was drawn and stored
in the
memory of
the computer.
Mr.
Geller
T s responses are shown
in the drawings
of
Fig.
2(b).
Although his responses have some elements
in common with
the
target drawing,
he did not recognize
the target
as
a church.
In Experiment
13,
the
target drawing,
an arrow through
a heart
(Fig.
2(c)),
was drawn
on
the
face
of
the cathode
ray tube and
then
the display intensity
was
turned off
so
that no picture was visible.
Mr.
Geller immediately
*
The Faraday
cage provides
120
dB attenuation
for plane wave radio
frequency
radiation over
a range
of
KHz
to
GHz.
For magnetic
fields
the attenuation
is
dB
at
KHz and decreases
to
dB
at
Hz.
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FIGURE
GRAPHICAL
MATERIAL
FROM
COMPUTER
DRAWING
EXPERIMENTS
WITH
URI
GELLER.
(a)
PICTURE
STORED
ON
VIDEO
DISPLAY,
(b)
PICTURE
STORED
IN
COMPUTER
MEMORY
ONLY,
(c)
PICTURE
STORED
ON
VIDEO
DISPLAY
WITH
ZERO
INTENSITY.
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drew an arrow under
a rectangle and
then drew another arrow inside
a suit-
case,
which he considered
a better representation of
the
target.
To obtain an independent evaluation of
the correlation between target
and response
data,
the experimenters submitted
the data
for judging
on
a
"blind” basis by
two
SRI scientists who were not otherwise associated
with
the research.
For
the
ten cases
in which Mr.
Geller provided
a
response,
the judges were asked
to match
the response data with
the
corresponding
target
data
(without
replacement).
In those cases
in which
Mr.
Geller made more
than one drawing
as his response
to
the
target,
all
the drawings were combined
as
a
set
for judging.
The two judges
each
matched
the
target data
to
the response data with no
error.
For either
judge such
a correspondence has
an
a priori probability,
under
the null
hypothesis
of
no
information channel,
of
p
=
(10!)
=
3 x
^
.
The quality
of match between target
and response
in certain cases,
together with
the overall probability
of matching obtained by
the judges,
constitute strong evidence
for
the existence
of
a potentially useful
information channel.
A second series
of experiments was
carried out
to determine whether
direct perception
of envelope contents was possible without
some person
knowing of
the
target picture.
One hundred
target pictures
of everyday objects were drawn by
an
SRI
artist and sealed by other
SRI personnel
in double envelopes containing
black cardboard.
The hundred
targets were divided
randomly
into groups
of
for use
in
each
of
the three days
T
experiments.
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On each
of
the
three days
of
these experiments,
Mr.
Geller passed.
That
is,
he declined
to associate any envelope with
a drawing
that he made.
On each
day he made approximately
12 recognizable drawings, which he
felt
were associated with
the
entire target pool
of
100.
He seemed
to be
disturbed by
the existence of
such
a large
target pool.
On each of
the
three days,
two
of his drawings
could reasonably be associated
with
two
of
the
20 daily
targets.
On
the
third
day,
two of his
drawings
were very close replications
of
two
of
that
day
T s
target pictures.
We
consider
that
the drawings resulting from this experiment
do not depart
significantly from what would be expected by
chance, which appeared
to
be Mr.
Geller
! s conclusion also,
leading
to passes
on his
part.
Thus,
it would appear
that eliminating a person knowledgeable
of
the
target degrades
the quality
of
the information channel.
However,
based
on Mr.
Geller
! s subjective impression,
there
is
also
the possibility
that
advance preparation of
a large target pool,
in comparison with single
target preparation
, results
in
cross
talk--i.e.
,
diffuses
the identity
of
the target
.
In
a simpler experiment Mr.
Geller was successful
in obtaining
information
in which no persons were knowledgeable of
the
target.
A double
blind experiment was performed
in which
a single die was placed
in
a small
steel box.
The box was
then vigorously
shaken by one of
the experimenters
and placed on
the
table.
The orientation of
the die within
the box was
unknown
to
the experimenters
at
that
time.
Mr.
Geller would
then write
down his perception as
to which die
face was uppermost.
Thus,
in
this
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case
the
target pool was known,
but
the
targets were individually prepared
in a manner blind
to
all persons
involved
in
the experiment.
This
experi-
ment was performed
ten times,
with Mr,
Geller passing twice and giving
a
response eight
times.
In
the eight
times
in which he gave
a response,
i
he was correct each
time.
The probability of
this occurring by
chance
is approximately one
in
a million, (1/6)
.
To summarize
the work with Mr.
Geller, ^ we observe
that
in certain
situations significant
information transmission can take place under
shielded conditions.
Factors which appear
to be important and
therefore
candidates
for
future investigation include whether
the subject knows
the
set
of
targets
in
the target pool,
the actual number of
targets
in
the
target
pool
at any given
time,
and whether
the
target
is known by
any
of
the experimenters.
REMOTE VIEWING OF NATURAL TARGETS
In experiments carried out
in our program
to
investigate
the abilities
of
a New York artist,
Mr.
Ingo
Swann,
he expressed
the opinion
that
the
insights
gained during experiments
at
SRI had strengthened his ability
to
view remote locations
that had been researched before he joined
the
SRI
program.
To
test Mr.
Swann’s
assertion,
a pilot
study was
set
up in which
a
fThe distribution of responses consisted
of
three
2s,
one
4,
two
5s,
and
two
6s
.
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Data
from
the nine experiments
are presented
in
the following para-
graphs.
Final judging indicated
that several descriptions yielded
significantly correct
data pertaining
to and descriptive
of
the target
location.
REMOTE VIEWING PROTOCOL
In
the nine double-blind remote-viewing experiments,
the
following
procedures were used.
An experimenter was closeted with Mr.
Price at
SRI
to wait
30 minutes
to begin
the narrative description of
the remote
location.
The
SRI
locations
from which
the subject viewed
the
remote
locations consisted of an outdoor park
(Experiments
1,2),
the double-walled
copper-screen Faraday cage discussed earlier
(Experiments
3,
4,
6-9),
and
an office
(Experiment
5)
.
A second experimenter would then obtain
a
target location from an
individual
in
SRI management,
the director
of
the
Information Science and
Engineering Division,
not otherwise associated with the experiment.
This
location was either
in
the
form of
traveling orders previously prepared,
sealed,
and randomized by
the target selecter
(Experiments
1,
2,
5,
6),
or by his driving
the
target demarcation team
to
the target himself without
any written indication
(Experiments
3,
4,
7-9).
The set
of
targets was
chosen from a
target-rich environment by asking
the selector
to use his
judgment
in providing
a
set
of nine target locations which were clearly
differentiated from each other and within thirty minutes driving
time
from
SRI.
In all
cases,
the
target demarcation team proceeded directly
to
the
target by automobile without
communicating with
the
subject
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or experimenters remaining behind.
Since
the experimenter remaining with
the subject at
SRI was
in ignorance both
as
to the particular
target and
also as
to
the
target pool,
he was
free
to question Price
to clarify his
descriptions.
The demarcation team then remained
at
the target site
for
an
agreed-upon thirty minute period following
the
thirty minutes allotted
for
travel.
During
the observation period,
the
remote-viewing subject
would describe his
impressions
of
the target
site
into
a
tape recorder.
A comparison was
then made when
the demarcation team returned.
To
represent
best
the detail and
style of these narratives,
we have included
the entire
unedited
text
of one of
the better narratives containing very
few incorrect
statements.
Experiment
7,
in an appendix.
In general,
the descriptions contained inaccuracies
as well
as correct
statements.
To obtain
a numerical evaluation of
the accuracy of
the remote
viewing experiment,
the nine original target locations were subjected
to
independent judging on
a blind basis by
five
SRI scientists who were not
otherwise associated with
the research.
The judges were asked
to match
the nine
locations,
which
they independently visited,
against
the
typed
manuscripts
of
the tape-recorded narratives
of
the remote viewer.
The
transcripts were unlabeled and presented
in random order.
The judges
were asked
to
find
a narrative which
they would consider
the best match
for each
of
the places
they visited.
A given narrative could be assigned
to more
than one
target
location.
The hypothesis
is
that
the judges,
when asked
to match
the actual
targets with
the
transcripts,
would place
the actual
target
in
the most
favored category more often
than
they
would
be expected
to by chance.
Table
shows
the distribution of
the
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PLACES
VISITED
BY
JUDGES
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TABLE
2.
Distribution
of
correct
selections
by
Judges
A,
B,
C,
D,
and
E
in
remote
viewing
experiments.
Of
the
selections
(5
judges,
choices),
were
correct.
Boxes
heavily
outlined
indicate
correct
choice.
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judges’
choices.
For purposes
of display we present
the table such that
the main diagonal corresponds
to
the correct
choices.
The number of
correct matches by judges A through
E
is
7,
6,
5,
3,
and
3,
respectively.
The expected number
of correct matches
from the
five judges was
five;
in
the experiment
twenty-four
such matches were obtained.
Among all possible analyses,
none
is more conservative
than
a
permutation analysis
of
the majority vote
of
the judges
selections
assuming assignment without
replacement.
By majority vote,
six of
the
nine descriptions
and locations were correctly matched.
Under the null
hypothesis
(no
remote viewing and
a random selection of descriptions
without replacement)
,
this outcome has an
a. prior i probability of
p
=
—
5.6
x
,
since,
among
all possible permutations
of
the
integers
one
through nine,
the probability
of
six or more being
in their natural
position
in
the
list has
that value.
Therefore,
although Price’s
descrip-
tions contain inaccuracies,
the descriptions
are sufficiently accurate
to permit
the judges
to differentiate among
the various
targets
to
the
degree indicated.
EEG EXPERIMENTS
An experiment was undertaken
to determine whether
a physiological
measure such
as EEG activity could be used
as an indicator
of information
transmission between an isolated subject and
a remote stimulus.
We
hypothesized
that perception could be
indicated by such a measure even
in the absence of verbal or other overt
indicators.
’
In other words,
this experiment examines
the hypothesis
that perception may take place
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at noncognitive
levels
of awareness and be measurable,
even though not
expressed verbally.
It was assumed
that
the application
of remote stimuli would result
in responses similar
to
those obtained under conditions
of
direct
stimu-
lation.
For example,
when normal subjects
are stimulated with
a flashing
light,
their
EEG typically shows
a decrease
in
the amplitude
of
the resting
rhythm and
a driving
of
the brain waves
at
the frequency of
the
flashes.
We hypothesized
that
if we stimulated one subject
in this manner
(a sender),
the EEG of another subject
in
a remote room with no
flash present,
(a
receiver), might
show changes
in alpha
(9-11
Hz)
activity,
or possibly
EEG driving similar
to
that
of
the
sender.
Applying
this
concept,
we informed our
subject
that
at certain times
a
light was
to be
flashed
in
a sender’s
eyes
in
a distant
room,
and
if
the. subject perceived
that
event,
consciously
or unconsciously,
it might be
evident
from changes
in his
EEG output.
The receiver was
seated
in
the
visually opaque,
acoustically and electrically shielded double-walled steel
room previously described.
The sender was
seated
in
a room across
the hall
from the EEG chamber
at
a distance
of about
7 meters
from
the receiver.
In order
to
find subjects who were responsive
to
such
a remote
stimulus,
we initially worked with four
female and
two male volunteer
subjects,
all
of whom believed
that success
in
the experimental situation
might be possible.
These were designated "receivers.”
The senders were
either other subjects
or
the experimenters.
We decided beforehand
to
run one or
two sessions
of
trials
each with each subject
in this
selection procedure, and
to
do
a more extensive study with any subject
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whose
results were positive.
A Grass PS-2 photostimulator placed about
1 meter
in front
of
the
sender was used
to present
flash trains
of
10 sec duration.
The receiver's
EEG activity from the occipital
region
(0^)
,
referenced
to linked mastoids,
was amplified with
a Grass
5P-1 preamplifier and associated driver
amplifier with
a bandpass
of
to
120
Hz.
The EEG data were recorded on
magnetic
tape with
an Ampex
SP
300 recorder.
On each
trial,
a
tone burst
of
fixed frequency was presented
to both
sender and receiver,
and was
followed
in one second by either
a
ten-second
train of
flashes
or
a null
flash interval presented
tfo
the
sender.
Thirty-
six such
trials were given
in an experimental
session,
consisting
of
12 null
trials— i.e.,
no
flashes
following
the
tone— 12
trials
of
flashes
at
fps,
and
trials
of
flashes
at
fps,
all randomly intermixed.
Each
of
the
trials generated
an 11-second EEG epoch.
The last
seconds
of
the epoch
was selected
for analysis
to minimize
the desynchronizing action
of
the
warning cue.
This 4-second segment was subjected
to Fourier analysis
on
a
LINC
8 computer.
Spectrum analyses
gave no evidence
of
EEG driving
in any receiver,
although
in control
runs
the receivers did exhibit driving when physically
stimulated with
the
flashes.
However,
of
the
six subjects studied
initially,
one subject
(H.H.)
showed
a consistent alpha blocking effect.
We
therefore undertook further study with
this
subject.
Data from
7 sets
of
trials
each were collected from this
subject
on three separate
days.
This comprises
all
the data collected
to date
with
this subject under
the
test conditions described above.
The alpha
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hand was
identified from average spectra,
then scores of average power
and
peak power were obtained from individual
trials
and subjected
to
statistical analysis.
Of our six subjects,
H.H.
had by
far the most monochromatic EEG
spectrum.
Figure
3 shows
an overlay of
the
three averaged spectra from
one of
this
subject's
36-trial
runs,
displaying changes
in her alpha
activity for
the
three stimulus conditions.
Mean values
for
the average power and peak power for each
of
the
seven experimental
sets were given
in Table
3.
The power measures were
less
in
the
fps
case than in
the
fps
in all seven peak power measures
and
in six out
of
seven average power measures.
Siegel's
two-tailed
_t approximation
to
the nonparametric randomization
test
was applied
to
the data from all
sets, which included
two
sessions
m which
the sender was
removed.
Average power on trials associated with
the occurrence of
fps was significantly less
than when
there were no
flashes
(t =
2.09,
df
=
118, £
<
.04).
The second measure,
peak -power,
was also significantly less
in
the
fps conditions
than
in the null
condition
(_t
—
2.16,
df
=
118,
_p
<
.03).
The average response
in
the
fps condition was
in
the same direction
as
that associated with
fps,
but
the effect was not statistically significant.
Spectrum analyses
of control recordings made from saline with 12K
ohms resistance
in place of
the subject with and without
the addition of
a
Ilz,
50 pV test signal applied
to the saline solution,
revealed no
indications
of
flash frequencies, nor perturbations
of
the
10 Hz
signal.
These controls suggest
that
the results were not due
to system artifacts.
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VOLTAGE
—
arbitrary
units
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5 Hz
10 Hz
15 Hz
THREE CASES —
0,
6 and
16 Hz
flashes
(12
trial
averages)
FIGURE
OCCIPITAL EEG FREQUENCY SPECTRA,
0 TO
Hz, OF ONE SUBJECT
(H.H.)
ACTING AS RECEIVER SHOWING AMPLITUDE CHANGES
IN THE
9-11
Hz BAND
AS A FUNCTION OF STROBE FREQUENCY
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TABLE
3.
EEG data
for H.H.
showing average power and peak power
in
the
-
11 Hz band,
as
a function of flash frequency and sender.
Each table entry is an average over
12 trials.
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Further
tests also gave no evidence of radio
frequency energy associated
with
the stimulus.
Subjects were asked
to
indicate their conscious assessment
for
each
trial
as
to which stimulus was
generated.
They made
their guesses known
to
the experimenter via one-way telegraphic
communication.
An analysis
of
these guesses has
shown
them
to be
at
chance,
indicating
the absence
of any supraliminal
cueing.
Thus, we note
that
in
this pilot
study,
one of
six subjects showed
significant EEG changes associated with
the presence of remote stimuli
under conditions
of
sensory shielding.
This
form of noncognitive arousal
evidenced
by alpha blocking has also been observed by Tart
(1963)
,
using
a small
electric shock stimulus applied
to himself
as sender
in
a similar
experiment.'
We hypothesize
that
the protocol described here may prove
to be useful
as
a screening procedure
for latent remote perceptual ability
in
the general population.
DISCUSSION
We have presented evidence
for
the existence
of
a biological informa-
tion channel whose characteristics appear
to
fall
outside
the
range
of
known perceptual modalities.
The precise nature
of
the channel
or
channels
is
as yet undefined,
but may involve either direct perception
of hidden information content,
perception of mental
images
of persons
knowledgeable of
target information,
precognition,
or some combination
of
these
or other information channels.
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We have worked with three individuals,
two
of whom are reported on
in detail here, whose remote perceptual abilities were sufficiently
developed
that
they were able
to describe both pictorial and geographical
material blocked from ordinary perception.
In addition
to experiments which centered on subjects
conscious
perceptions,
we have also conducted EEG experiments
in which we have
found
statistically significant
evidence
of direct physiological indications
of nonconscious perception of remote stimuli.
The observation that
a
nonconscious
link with physiological correlates
can exist between separated
individuals
is
one
that merits considerable study.
From these experiments we conclude
that
° A channel exists whereby information about
a remote location can
be obtained by means
of an as yet unidentified perceptual modality.
As with all biological systems,
the information channel appears
to
be
imperfect,
containing noise along with
the signal.
° While
a quantitative signal-to-noise ratio
in
the information-
theoretical sense cannot
as yet be determined,
the results
of our
experiments
indicate
that
the functioning
is
at
the
level
of
useful information transfer.
It may be
that remote perceptual ability
is widely distributed
in
the general population,
but because
the perception
is
generally below an
individual's
level
of awareness,
it
is repressed or not noticed.
For
example,
two
of our subjects
(H.H.
and P.P.)
had not considered themselves
to have unusual perceptual ability before
their participation
in these
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experiments.
We conjecture that
it
is partially
the prevailing philosophical
attitudes
of
the
times
in which we live
that prevent
such ability as may
exist
from surfacing
to
a greater extent.
Our shared cultural constraints
deny permission for
the demonstration of such abilities.
With regard
to
the methodology itself,
our observation of
the phenom-
ena leads
us
to conclude
that experiments
in the area of so-called paranormal
Phenomena can be scientifically conducted.
The results presented here
offer
a basis from which departures
as
a function of other observables
can be studied.
Our goal
for
future experimentation
is
the investigation
of
the physical and psychological laws underlying these phenomena,
rather
than just
the addition of
further demonstrations
of
the statistical
appearance of paranormal phenomena in
the
laboratory.
ACKNOWLEDGMENTS
ihls
researcli was
sponsored by The Foundation for Parasensory Investi-
gation,
New York City.
We wish
to
thank its president,
Mrs.
Judith
Skutch,
and their representative,
Dr.
Edgar
D.
Mitchell
of
the Institute of Noetic
Sciences
as well
as
our
SRI associates,
Mr.
Bonnar
Cox,
Mr.
Earle Jones,
and
Dr.
Dean Brown
for their support and encouragement
throughout
this
work.
We also wish
to acknowledge
Dr.
Wilbur Franklin
of Kent State Uni-
versity for his contribution,
especially
in
the early phases of
this
research.
Finally,
we acknowledge
the many constructive suggestions provided
us
through conversations with Mrs.
Jean Mayo,
Dr.
Charles
Tart,
University
of
California,
and
Dr.
Robert Ornstein and
Dr.
David Galin of
the Langley
Porter Neuropsychiatric
Institute.
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REFERENCES
1.
J.
Pratt,
J.B.
Rhine,
C.
Stuart
and
J.
Greenwood,
EXTRA SENSORY PERCEPTION
AFTER SIXTY YEARS,
New York,
Henry Holt,
1940.
2.
S.
Soal and
F.
Bateman, MODERN EXPERIMENTS
IN TELEPATHY,
London,
Faber
and
Faber,
1954.
3.
L.L.
Vasilliev,
EXPERIMENTS
IN MENTAL SUGGESTION,
Hampshire,
England,
ISMI Publications,
1963.
4.
J.R.
Musso and M.
Granero,
"An ESP Drawing Experiment With
a High-
Scoring Subject,"
J.
of Parapsychology,
Vol.
37,
pp.
13-37,
March,
1973.
5.
It has been widely reported that
Mr.
Geller has demonstrated
the ability
to bend metal
by paranormal means.
Although metal bending by Mr.
Geller
has been observed
in our laboratory,
we have not been able
to combine
such observations with adequately controlled experiments
to obtain
data sufficient
to support
the paranormal hypothesis.
6.
K.
Osis, ASPR Newsletter,
No.
14,
Summer,
1972.
7.
C.T.
Tart,
PHYSIOLOGICAL CORRELATES OF PSI COGNITION,
Inti.
J.
of
Parapsychology,
Vol.
V,
No.
4, Autumn,
1963.
8.
E.D.
Dean,
"Plethysmograph Recordings
as ESP Responses,"
Inti.
J.
of
Neuropsychiatry,
Vol.
2,
October,
1966.
9.
D.
Hill and
G.
Parr,
ELECTROENCEPHALOGRAPHY:
A SYMPOSIUM ON
ITS VARIOUS
ASPECTS,
Macmillan,
New York,
1963.
10.
S.
Siegel,
NONPARAMETRIC STATISTICS FOR THE BEHAVIORAL
SCIENCES,
pp.
152-156,
New York, McGraw-Hill Book Co.,
Inc.,
1956.
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APPENDIX
Following
is
the unedited transcript
of remote viewing Experiment
7,
where
the
target
was
an Arts and Crafts Garden Plaza.
This
is
a
large
plaza resembling
a California mission.
There are craft
shops around
the
perimeter
of
the plaza.
in
the plaza
area
are many gardens,
flowers,
ceramic
pots,
fountains,
and
paths.
Overhead are
vines
on arbors
of
redwood.
Price's description
is accurate
in almost every
detail
and he
omitted little
of
importance.
1:40
THIS
IS A REMOTE VIEWING EXPERIMENT WITH PAT PRICE,
DEAN BROWN
AND RUSSELL TARG
IN THE SHIELDED ROOM
IN BUILDING
30.
THE TRAVELLERS TO
REMOTE LOCATION ARE BART COX,
HAL PUTHOFF,
JUDY SCHMICKLEY AND PHYLLIS
COLE.
WE EXPECT THE TRAVELLERS TO BE AT THEIR PLACE
IN ABOUT
10 MINUTES,
IT
S
1:58.
OUR TRAVELLERS
SHOULD BE NEAR TO ARRIVING AT THE PLACE.
OK.
Why don't
I
start scanning by quadrant using
this
as
a
center point
12-3,
6-9
I
go from 12-3
first.
Seems
to me right now that I'm picking
them up
m
the
12-3 quadrant,
but
I'll
go on in
the
rest and
look.
I
haven't
actually identified
them,
I
just
feel
that they're
there.
Nope,
I
don't
get
them
there.
Now I'll
go
from 6-9.
While
I
was
looking at
6-9,
it
looks
to me
like
I’m looking
at
an
iris,
a
flower of some
kind.
I'll
come back and
identify that
later.
Just wanted
to
get
it down as having
a
flash of
an
iris
flower-purplish.
I'll continue
to
scan
that quadrant.
Nope
don't
get
them
there.
I'll
S°
9-12.
Don't
get
them
there.
I
go back
12-3,
Yeah,
I
get
them
in
that quadrant.
Now
I'll
see
if
I
can
locate them physically and identify
the
area.
I'm looking at something
that
looks
like an arbor,
trellis-work arbor.
Seems
to be cool,
shaded.
Doesn't seem to me
that
they’re
out
in
the
direct sunlight.
Be more
like there’s
lots
of
trees,
in an arbor area.
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Tho arbor appears
to be made of wood,
possibly redwood.
They're
just. ... looks
like
it's
a
dirt
path,
quite wide,
I’d say
maybe
feet.
I
can see
some grass.
Looks
like possibly
a
fountain
of some
kind.
Yeah,
I
can see Bart
in his
red shirt and what
looks
like kind of
a
gray paisley
tie
-
I
didn't really
look at
that when he was
down
there.
The
red
shirt,
I
did.
Looks
like he has
on
a
gray paisley
tie.
It appears
they're walking along quite
leisurely.
Looks
like
there's some red brick laid into
a walkway.
They
don't
seem
to
be on
it,
they just seem
to pass
over
that.
I
got
-
it
seems
like
a
little ways away from them there are quite
a
few people but
right where they're walking
it doesn't appear
to
be many right
in
there.
This
is
an
arbor area.
Back
of
that
arbor,
back here
I’d
say 50
feet
from
that
arbor
to here,
seems
to be
a
lot of people
in here.
They
were walking along here on what
looks
like about
a
foot dirt
path.
WJJAT KIND OF PLACE
IS THE ARBOR
IN?
IS
IT A FIELD OUT
IN THE OPEN?
No,
I want
to say
park,
but
it
doesn't exactly feel
like
a
park.
If
you took
a
-
the
feeling I'm getting
-
it's
not
the specific place
-
but
Like the Town and Country Market.
That
type
of an atmosphere,
with quite
a section of
it
into
a
little outdoor park,
but basically
I'm getting
a very strong feeling
of
flowers.
Like
the
first
one
I
saw was
an
iris.
TELL ME ABOUT THE TOWN AND COUNTRY ASPECT.
IN WHAT WAY DOES
IT REMIND
YOU OF TOWN AND COUNTRY.
The buildings,
not
right
where
they're
at,
but very close
to
them have
that
same kind of architecture
and
look.
The parking
lot
looks
similar
grand,
sweeping,
not
cluttered,
it's more expansive area.
You
take
a
place like Sears Mall
-
it
seems cluttered.
This
seems more
leisurely
paced.
People are moving about slower
-
there's not
the hustle and bustle
-
more
or
less meandering.
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TOWN AND COUNTRY MEANS TO ME A COVERED WALKWAY.
Yoah,
the back
of
them
it seems
to be
- where
they are
seems
to be
a
very
large arbor
like vines growing over
it and
things,
and there possi-
bly
-
I
haven't
looked
in there
yet
to
see
if
there's
any displays
like
pottery and things
-
I
get
the
feeling that
there
is right close
to
it.
ALSO,
OUTDOORS?
Yeah,
it
seems
like
fairly high
shade trees
-
kinda
bordering.
The center
part doesn't seem
to have
it
-
this part
in here.
The
trees seem
to be
way up
in here along
like
this
over here.
This seems
to be shaded
in
here,
but
it
f s
sunny
out
here,
I
just saw something
that
looked
like
a windmill
-
not
a farm
type wind-
mill
-
a Dutch-type windmill.
It's
smaller
-
it's
not
a huge
thing,
but
I'm getting
a definite
feeling that
it's
like
a windmill.
The area
in there
feels
damp
-
not wet
-
they're not walking
in water,
but
it’s very moist.
The
temperature
in there... it's
secluded.
Feels very comfortable.
A
little
on
the shady
side.
WIIAT DO YOU FIND AS THE BOUNDARIES OF THE PLACE THEY'RE AT?
Outside of
this
little park-like affair
that
they seem
to be
in,
there's
a
street.
One
side
of
it
seems
to be
a kind of
a residential ... the other
seems
to
be
a
little bit more heavily
travelled.
Let me pick up
a
little bit more.
I
can see one
very
large oak tree
- exceptionally
large.
Right now Bart
is
trying
to point something out
that
is basically
the
significance
of
the whole place.
It’s
like
that
key
thing,
well,
if
you’d have mentioned
a
salt pile
I'd have blown my
lid.
Well,
this has
^
® ^
1 If
nee
that
s just about comparable
to
that.
I'm screening
it
out
.
Thing
that just flashed
in was kind
of like
a
stadium structure
—
like
looking down
into
a
stadium.
Just when
I
did
that
I
-
I'll have
to reorient
to make sure
I’m looking
in
the same
area
now.
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Seems
like
they’re
-
I
still
get them in
the same quadrant
I had them
m originally.
Seems
like some decorative brick walls.
THE QUADRANT YOU HAD THEM
IN
IS BASICALLY THE NORTHEAST QUADRANT?
Yeah.
I
got
them out about
this
far
-
it's
not
far
away
-
I’d say in
this
direction over here about
-
feels
like
a mile
to
a mile and
a half
They
don’t
feel
as
far away,
and
I’m not
looking at
the
time
continuum.
They actually
don't
feel
as
far away.
I’d say
that
it
is
about
-
not
alf
the distance
they were
to
the marina,
and
it
seems
to be on
a
line
just
about
in
that direction but
just
a hair more
-
rather than
a
direct
line
from here
to
the marina
-
they seem to be just slightly more
to
the
I
was
looking back
to where he had
the car parked and
it
seems
like
it's
on asphalt
then
a
curb
in
front,
and
then it's
like
a
dirt walkway and
then
a sidewalk.
But
I
can see eucalyptus buds
on
the ground and some
branches
of eucalyptus
there.
One
of
the most dominant
things
to me
in the way
of unusualness
is
the
size
of
the oak tree
that
I'm looking
at.
Looks
like an arboretum,
or
I
get
the definite feeling of flowers.
Almost
get
the
feeling
like
it's
commercial
flowers.
In
fact,
the most predominant
feeling
that I’m getting right now
is
flowers
Don’t know why
iris particularly.
There's something about
the windmill
that
I
was
going
to
look
at.
Wasn't
that what
you
were.
.
. .?
Be
like
one you’d almost
see
in
a miniature golfcourse.
.
. the windmill.
Has
all
the construction and detail
but not
as
large
-
it’s
fairly small
Seems
to be made out of
dark redwood and it’s
kind of aged.
I'm going
to try
to
look more directly
to
them.
Let’s
see,
there’s Bart
and Hal,
and behind Bart
is Judy and behind Hal
is Phyllis,
kinda
stag-
gered
there.
Looks
like
a
possible
small pool
of water
-
like
a garden pond.
Looks
like
a
little bridge.
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I
was
trying
to get
the
feeling
of what
type
of an area
it
was.
Let me elevate
a
bit.
I'm looking at much too small
an area.
There's
some greater significance there
that
I
feel
I'm definitely not
looking
at -let's jack up
a
bit... maybe 500
feet.
I
see
a
lot
of
trees.
I
see Judy's red hair and her brown eyes and her flashing
teeth
-
she
has beautiful
teeth.
Hadn't really looked at
them before.
Phyllis and her are
talking about something and Hal and Bart
are talking
about something and he's pointing
at something and
it seems
to me
that
he's pointing over
to what
I'd call
a windmill
or something
that
looks
like
a windmill.
The water
I
see
looks more
like
a pool
or
a pond
than
it
does
-
you
know,
it's
not big like
a
lake
-
not very
large,
but
it
looks
like
a definite
poo l
.
Right where
they
re at
I
don't hear
too much
traffic noise
—
it
seems
to
be
fairly quiet.
Looks
like
a
little wooden walkway.
Feels
a
little
early,
but
it
kinda seems
like
they’re retracing
their
steps heading back
toward
the
car,
but
they're
still moving quite
leisure
IF YOU LOOK DOWN ON THE PLACE FROM ABOVE,
CAN YOU GET ANY FEELING FOR
THE
-
IS THERE ANY OVERALL LAYOUT OR PLAN?
When
1 went up
I
could
see
trees and
stuff,
and
I
kind of
got
the
feeling
of
like
in
a corner
of
a
golf course,
you know
— where
there would be
a
lot
of
trees overhanging the green and some things
in there
-
that seemed
to be out
of
context,
but when
I
elevated,
that's what
I
got.
It
kind
of
looked
like an overlap
to
me,
so
I
didn't
talk about
it,
but
I
will.
When
I
elevated
it
kind of
felt
like
it was
right over
the
corner
of
a
golf course
of
some
kind,
with
a street running down one
side,
and
they
are fairly close
to
that.
In
fact,
the bricked area
that
I
looked at or
like
a patio
thing kinda
looks
like
a
walkway.
Seems
like there's
small building
-
small meaning
not
tall
-
looks
like
a
single story building.
Looks
like
it
has
a
flat
roof
—
slightly pitched.
Looks
like 4x4 poles supporting
it
—
has
a
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canopy out
over
it.
They're painted white,
place
looks
like very possible
light yellow or cream color.
They're walking not
too
far from that.
Still
seems
to me
that
they’re
on
a
dirt pathway.
In
the area
that
they’re
in now
I
get
flowers again
- where before
they
kinda
fell
out
of
the
flowers.
Looks
like maybe 80-100 yards from where
they are
-
looks
like
guys
on
a motor
scooter.
They can see
them.
WHAT WOULD YOU SAY
IS THE INTEREST TO THIS PLACE?
WHAT’S SPECIAL ABOUT
THIS PLACE?
It seems
to be
a
kind of
a recreational,
relaxed ... not energetic
-
looks
more
relaxed.
I’d say
it’s
kind of combination recreational
and relaxation
area
that
I'm getting out
of
it.
That would be
the
general character
of
it.
Two aspects
-
one
is aesthetics and
the other
is
a
kind
of
a mild recre-
ational
area.
There
seem
to be some unique
features
-
I
don’t have
it
totally into
context
as
yet.
There’s
a
number
of
things
that
I’ve rejected
-
looked
at
and rejected
saying.
first,
I
got
the
impression
that
it was
kind of
like
a miniature
golf
course
-
I
rejected
that.
Merely from saying
it
-
I
didn’t reject
the
principle
-
I
just rejected saying
it.
Then
I
kind of got
the
idea
of
a
standard golf course
-
I
also rejected
that
on
the same principle,
so
I'm just trying
to describe
the
terrain.
Seems expansive
-
doesn’t seem cluttered.
Just
got
a
flash
of something that reminded me
of
the gyroscope
-
gimbals
on
the gyroscope.
Drinking
fountain
-
looks
like
it’s made
out
of
kinda
like field stone
built
up
into
a
fountain
.
.
. bowl
.
I'm going
to elevate again
and
go
through
a
search quadrant again.
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I
still
got
them in that general
location,
so
that
seems
to
set
all right
Distance
- maybe
a mile,
mile and
a
half.
Doesn’t
seem much farther-
seems
fairly
close.
The area has an awful
lot of grass,
lot
of
trees
-
looks
like
dirt walk-
ways,
well
trimmed.
I
can see
the
arbor,
and
the arbor could be
a place
to sit and be out
of
the direct
sun.
May be
a
few
little
tables and benches
and chairs
in there.
That
outlooks
over quite
a grassy area
-
there are quite
a
few
trees.
I
see basically
an
oak.
Right after
they
got out of the car
I
could
see
some eucalyptus buds
and branches
on
the ground,
and
it seemed
like
the
trees were
there.
Looked
like
they got out of
the car,
stepped upon
a
curb,
dirt parkway,
a sidewalk,
and
then
they went into this
area.
I
get
the
feeling
this windmill
type thing
-
that all
seems
fairly
real.
The
feeling
is
still
that
it's relaxing and has
some recreational
aspects
I
just haven't put
it
totally
together
as
to giving
it
a
name.
Right now
I
get
a
very strong impression of
flowers
again.
It seems
like
right now they're back
to right where
I
originally spotted
them only
they're going
in the opposite direction
-
like
they're moving
toward
the direction they originally went.
While
they were
there
they walked on several pathways
- walked out quite
a
ways,
then swung over and come over and worked around and
looked at...
One peculiar thing
I might note
-
so far
I haven’t
sensed,
seen nor heard
an airplane.
Cars
seem quite distant
-
outside
of
that
little motor scooter affair
with
the
two guys
on
it.
That’s about
the only vehicular
traffic
I've
seen
- except out
in
the parking
lot.
It seems
like
t o me
that
they've got most
of
their attention off what
they were
looking at
and they've got
their attention more
on the car
now.
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T want
to look and
find out
was
talking about.
what
the significant
thing was
that Bart
There’s something quite unusual
there and
I
up.
Damned
if
I
can pick
it
WAS HAL DOING ANYTHING BESIDES WALKING ALONG
FOR HAL TO DO?
WAS THERE ANY ACTIVITY
Most
of
the
time
I
was
looking at Hal, he was
kind of listening
to Bart
and Bart was pointing
out
a number
of
things.
by“udj.“
e
tlB° B8rt ™S ” lklnE Wi“ H8l;
Part
°f
the
tlme he
back
When
I
£lrst saw them,
it was Bart in the
front on the
left
side
Hal
^ WaS SllShtly
- •!«»* between Bart'and
Hal but behind,
and Phyllis
to her right.
They wandered around but
the
first
way.
time
I
picked up
-
they were
that
When they were coming back,
they just about reversed
Bart
front
.
When
they were coming back,
it
looked
like Bart w^s
with Phyllis,
and Judy was walking more behind Bart and Hal
when they were
coming back out
of
there.
would be
in
in front
on her right
They're actually at
the
car.
2:30
SHALL WE GO DOWNSTAIRS AND SEE HOW THEY’RE DOING?
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CPYRGHT
Perception & Psychophysics
1973. Vol.
14. No.
2. 313-318
A study of sine-wave contrast sensitivity
by two psychophysical methods*
D. H. KELLY and R. E. SAVOIE
Stanford Research Institute, Menlo Park, California 94023
In
the
literature
on
visual
contrast
thresholds
for
sine wave
gratings,
little
attention
has been
paid
to
the
psychophysical methods used to obtain these spatial-frequency response curves. Here we report a comparison of such
data obtained by two quite different psychophysical methods, but otherwise under identical conditions usmg five Ss.
Both experiments were run bv computer: (1) In the method of adjustments, the computer program merely controls the
order of the sdmuh^md records S’s contrast settings. (2) In the forced-choice staircase (FCS) technique, the program
determines how often S can discriminate the sinusoidal grating from a uniform field, informs S of his accuracy, controls
the
stimulus
contrast on the basis of S’s preceding responses, and brackets his threshold by
a
series of successive
approximations. Method 2 eliminates criterion effects that occur in Method
1, and hence tends
“
“"'Xtain eaSlv
differences
However,
the FCS
technique
requires
, an
order
of magnitude more
observing time to
obtain equally
ZZrLZ sensitivity curves. FCS
...» inc,.,*, the <,,,,,» sensitivity of some Ss by. much « ta me
. but
does not
significantly change the shape of the contrast sensitivity curve; both methods show strone effects ot
inhibition at low spatial frequencies.
Measurements
of
the
contrast
threshold
for
a
sinusoidal
grating as
a function of its spatial frequency
have been used to study the effects on the visual process
of
optical,
neural,
chromatic,
' temporal,
and
other
factors. Van Meeteren (1966) has reviewed
a number of
these
stpdies. We
. are
particularly
interested
iri
the
low-frequency
region
of
such
data,
below
about
cycles/deg
(cpd),
because
the. monotonic
increase
of
contrast sensitivity with increasing spatial frequency in
this
region
may
represent
a
simple
form
of
lateral
inhibition (Kelly, 1973).
In certain cases,
little or no low-frequency falloff \vas
reported
(e.g., Westheimer,
I960; Campbell & Green,
1965), but
this has been attributed to the use of small,
sharp-edged
targets
(Davidson’,
1966;
Kelly,
1970)
or
flash
, presentations
. (Kelly,
1971,
1973),
which
are
unsuitable for isolating the steady-state response to very
low
spatial
frequencies. However, some' Ss report
that
fire
task
of
detecting
a
low-frequency
grating seems
different from
the
high-frequency
detection
task; this
raises
the question of whether the apparent
inhibition
would
persist
at low frequencies if criterion effects weie
eliminated.
Many of the data in the literature have been obtained
by the psychophysical method of adjustments, which
is
the
easiest
and
fastest
procedure
when
Ss
are
experienced
iit
this type of judgment; variations of the
method
of
limits
have
also
been
used.
But
more
sophisticated
psychophysical
methods
have
been
developed
in
recent
years
which
are
essentially
independent of threshold criterion; these have not been
*Our work was partly supported by NIH Grant No. NS-08322
and NSF Grant No. GB-11571. Some of the data were reported
at the October 1971 meeting of the Optical Society of America
in Ottawa, Canada. We thank T. N. Cornsweet for suggesting this
study.
applied
to
the
measurement
of
sine
wave
contrast
thresholds. We therefore undertook to compare the sine
wave thresholds obtained by the method ot adjustments
with those obtained by
a forced-choice staircase (FCS)
paradigm,
in which the S was always informed
ot
the
correctness of his choice. Our main purpose was to find
out
whether
the
low-frequency
inhibition
was
independent of criterion effects, but our results are also
relevant to other sine wave contrast experiments that use
subjective judgments.
METHODS
,
The
stimulating
apparatus
is
described
in
detail
etpvvhere
(Kelly. 1966, 1972); its components are shown schematically in
Fig.
i.
S
is
seated
. comfortably,
viewing
a cathode
ray
tube
(CRT) 50 cm distant through an artificial pupil,, 2.3 mrn in diam.
He
sees
an
8-deg
circular
field,
filled by
, a
vertical
sinusoidal
grating. -The. spatial frequency
- of, this grating
is controlled by
a
(LINC 8)
computer. The dependent
variable
is, the Michelson
contrast (m)
of. the grating, defined as
Bmax + Bmiri
where] B max and. B min are the maximum and minimum values of
the stimulus waveform,
in trolands
(td)
of retinal illuminance.
This contrast
is under the control of either the computer or the
S
depending on
the mode of operation. Since the grating does
not
flash
or
flicker
in
the
present experiments, our temporal
waveform source was not used (see
I
ig. IT
Adjustments Mode
In the method of adjustments,
tile S controls the contrast of
the grating, using a geaxed-down potentiometer without stops or
other
mechanical
cues.
Spinning
the
knob
about
1,200 deg
covers
the
entire, adjustment range, which may be either 0-1
or
0-0.1
contrast,
depending
on
a
switch ^controlled
b\
the
b.
Another
switch
gives him
the
option
of viewing
zero or
tull
contrast
at any
time, without
losing
his potentiometer
setting.
When
the
setting
meets
his
threshold
criterion,
he
pushes
a
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314
KELLY AND SAVOIE
(it)
METHOD OF ADJUSTMENT
Ibt
FORCE D -CHOICE STAIRCASE METHOD
Fig.
1.
Signal-flow
diagrams
of
the
CRT
stimulator,
(a) Configuration
for method of adjustments, (b) Configuration
for forced-choice staircase (FCS) procedure.
button which enters this contrast into the computer.
He
is instructed to fixate the center of the grating and to find
the contrast at which
it can just be discriminated from a uniform
field.
(This
criterion,
which
we
always
use
for
sine
wave
thresholds, should come close
to matching
S’s performance
in
the forced-choice task described below.) S spends as much time
as he wishes “hunting” back and forth to tind his threshold, but
we instruct him to make his final judgments only
in the steady
state;
i.e., after he has refrained from changing the contrast for
several
seconds. Twelve
spatial frequencies were
tested
in one
experimental
session; each
pattern was presented
five times
in
random
order, for a total of 60 judgments. The means of these
five
settings
gave
fairly
smooth
spatial-frequency
response
curves, as described below. An experienced S can complete such
a run in 20-25 min.
Forced-Choice Staircase (FCS) Mode
Our
criterionless
psychophysical
procedure
combined
the
staircase method of ordering stimuli (Bekesy, 1947; Cornsweet,
1962)
with
the
forced-choice method
of response
collection
(Blackwell
1946; Heinemann,
1961).
In
this
application,
the
two
techniques complement
each
other
in such
a way
that
S
spends most of his time making discriminations near threshold.
The
S’s task
is much simpler
in the FCS mode. The same
stimulus patterns
are
used, but their contrast
is now under the
control
of
the
computer. One
stimulus
cycle consists of two
successive
intervals,
each
5 sec
long;
a
pattern
of
nonzero
contrast
is
presented
in
only
one
of these
intervals, which
is
determined by
the computer from
a table of random numbers.
One second
after
the beginning of each interval, a marker tone
sounds to notify S that the stimulus may be visible. He makes his
choice of interval by pushing a button, which also starts the next
trial; but
this button has no effect until after the second tone. In
other words, S must make
a choice in order to start a new trial,
but he cannot do so until after the second interval has started.
As
soon
as
he
makes
his
choice,
he
hears
a
pleasant
tone
(different from the marker tone) if he
is correct or an unpleasant
noise if he
is not.
His only other control
is a “pause” switch, which interrupts
the experiment
for
rest periods.
S may use
this switch also to
abort
a given
trial
(if,
for example, he happened to be looking
away when
the
marker
tone
sounded).
The
aborted
trial
is
repeated when the pause switch is reset, but the stimulus will not
necessarily occur in the same interval.
In order to avoid transient effects (Kelly,
1971,
1973), as we
do in the adjustments mode, the temporal waveform of the FCS
stimulus
is carefully controlled. The mean luminance of the CRT
screen
is held constant throughout the experiment. When a given
pattern
is presented,
its contrast
is smoothly “faded
in” from
zero
to whatever
value
is
set by
the
computer,
as shown
in
Fig. 2a.
The
temporal
envelope
of
the
fade-in
waveform
resembles
a half-cycle of a 0.5-Hz cosine wave, so that the
full
contrast of the pattern
is present after
1 sec (this contrast always
being zero in either the
first or second interval, at random). The
pattern is also faded out the same way.
All 12
staircases
are independent and randomly
interleaved,
which
helps
to
eliminate
subjective
bias
effects
(Cornsweet,
1962). On
each
trial,
the
contrast
of
the FCS
stimulus
is
contingent on the correctness of the preceding responses to the
same pattern, according to an algorithm described in detail in the
Appendix. When
the
responses
indicate
that
S can detect
the
pattern, the contrast
is decreased; when he cannot, the contrast
is increased, by a constant logarithmic increment in either case.
Thus,
the
contrast
is forced
to cross and recross the threshold
level
(which
is about 75%
correct).
At
first,
the
size
ot
the
increment
is decreased each time the response sequence indicates
that
a contrast increase has probably crossed S’s threshold. But
the
third
time
this
indication
occurs,
the
smallest
increment
(30%
contrast
change)
is
maintained
and
the
staircase
is
terminated with a fixed number of additional
trials.
A
typical
staircase
illustrating
these
properties
is shown
in
Fig. 2b.
Each
stimulus
is
first
presented
at
full
contrast,
to
familiarize S with its appearance and to provide a suprathreshold
baseline,
if he detects
it
correctly,
its next presentation
is
at a
contrast
of 0.02; the
staircase then enters
the main algorithm
(see Appendix).
TIME -
seconds
TRIAL NUMBER
Marker
Tones Oclj?
,il
ttie Amjvv
“m"
is Control 't’d b*
Itv- Conti,m Algorithm
Stimulus Otcuis
in
(he
First
or Second
Interval
at Random
|a)
FORCED -CHOICE PRESENTATION CYCLE
lh!
TYPICAL STAIRCASE
Fig, 2. Details of the FCS procedure, (a) Temporal waveform
of one stimulus cycle and timing of alerting tones, (b) A single
staircase, reassembled to show all contrasts presented, increment
sizes, wrong responses, and calculated threshold.
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-
..
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Several
hundred
trials
are
required
to
terminate
all
:aircascs;
an
experimental
session
usually
takes
65-75 min,
igardlcss
of
the
skill
or
experience
of
the
S. Most
of the
inability in length of the individual staircases (Rose et al, 1970)
averaged
out by
the
large number
of
staircases being
run
multaneously. 1
The threshold for each pattern is calculated as the mean of the
ist
eight
contrasts presented, no adjacent
pair of these being
jparated by more than the smallest increment. The intersession
ariability of PCS data obtained in this .way is no greater than in
he
adjustment
mode,
but
is
mainly
random
rather
than
ystematic.
Thus,
to
obtain
equally smooth
spatial-frequency
ssponse
curves,
one
must
average
the
data from
three PCS
?ssions, as described below.
RESULTS
Figure 3
shows
some
contrast
sensitivity
data
ibtained
with
a
20-year-old emmetropic
naive
S. The
ipper
curve
(filled
circles)
represents combined
data
rom
three
FCS
runs;
three
comparable
adjustment
:urves
are
plotted
separately (open circles). These data
,re typical of our results in three ways.
First, the shape
)f the FCS curve
is
essentially the same as that of the
idjustment curves; in both cases, the contrast sensitivity
ncreases
steeply
at
low
spatial
frequencies,
to
a
naximum
near
4cpd.
Second,
the FCS
sensitivity
is
ystematically greater than that in any ol the adjustment
uns,
by
a
factor
of
to
5.
Third,
there
are
also
iystematic differences among the Individual adjustment
;urves, but
these
are smaller than
the FCS-adjustment
iifferences.
The
lowest
sensitivity
in
Fig. 3
represents
the
first
SPATIAL FREQUENCY
(cpd)
Fig. 3.
Contrast
sensitivity
vs
spatial
frequency
for
S K.S.
Retinal
illuminance,
1,300 td;
artificial
pupil,
2. mm.
Filled
circles
are the means of three FCS runs. Open circles represent
three successive adjustment runs.
SINE-WAVE CONTRAST SENSITIVITY
315
Fig. 4.
Contrast
sensitivity
vs
spatial
frequency
for S D.K.
Same conditions as Fig. 3.
experiment
with
S K.S.
Her
adjustment
sensitivity
increased
subsequently,
but
leveled
off between
the
second and
third adjustment
runs. Typically,
a naive S
starts with
a
high
threshold
criterion, which he
then
lowers
after
some
experience
with
the
method
of
adjustments. However, his adjustment thresholds seldom
get
as low as his FCS thresholds; apparently he adopts a
criterion
in
the
range
of 90%-100%
probability
of
detection
(compared
to the 75% imposed by
the FCS
mode).
Figure 4 shows
a
similar comparison
for another
S.
S D.K. (one of the authors) is somewhat atypical, having
had hundreds of hours of practice in experiments with
this
particular
apparatus.
If
practice
lowers
the
adjustment threshold, his adjustment
sensitivity should
be
greater than
that of SK.S.; and
it
is, relative to
Ills
FCS
sensitivity.
His adjustment
sensitivity may
still be
slightly
less
than
his FCS
sensitivity, but
the two
are
much
closer
together
than
they
are
for our other
Ss.
Evidently he uses
a lower threshold criterion, closer to
the FCS level. As in Fig. 3, the FCS curve in Fig. 4 was
obtained by averaging data from three sessions, a total of
about 3.5 h observing time.
However,
the
contrast
sensitivity
curves
obtained
from individual FCS sessions
are
also instructive; these
are shown
for
a
third S
in
Fig. 5. Each of the dashed
curves
in
this
figure connects
the end points of the
staircases obtained
in
a single experimental session (see
Fig. 2b). The mean curve
for these three FCS sessions
is
shown
for
comparison
with
the
previous
figures.
Figure 5
also shows some
systematic
variation among
three
adjustment
runs
for
this
S.
(S H.P.
was
more
experienced
than
K.S.. but even an experienced
S will
not always hold the same adjustment criterion from one
run to the next.) Again, the FCS sensitivity
is about five
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KELLY AND SAVOIE
Sub). HP
CPYRGHT
CO<
0.02
H2O
°
0.05
Adjustments
—z-
1st Run
-a-
2nd
Run
k-
3rd Run
0,2
0.5
SPATIAL FREQUENCY
(cpd)
Fig. 5.
Contrast
sensitivity
vs
spatial
frequency
for S H.P.
Same conditions as Figs. 3 and 4. Dashed lines show data from
three FCS runs, averaged to obtain filled-cirde points.
times greater than the adjustment sensitivity.
The
most
important
result
shown
in
Fig. 5
is
the
nature
of the
variability among FCS runs and among
adjustments
runs. Although the FCS data
are about as
variable
as
the
adjustment
data,
the
adjustment
variability
is
mainly
systematic,
while
the
variability
among the FCS runs seems random. (Note that the FCS
curves from
individual
sessions
cross and
recross each
other and the mean curve several times.) The data were
subjected
to
a
chi-square
test
of the
hypothesis
that
mean rank contrast sensitivity
is independent of session
number.
This
hypothesis
can
be
rejected
for
the
adjustments data (p< .001), but cannot be rejected for
the FCS data (p - .1).
Now, if the FCS method eliminates systematic intra-S
variability
from
one
run
to
the
next,
and
if
this
intersession variability is caused mainly by changes in S’s
criterion,
then
we
would
expect
this
method
to
minimize
the
variability among Ss
as
well. The
data
shown im Fig. 6 tend to confirm this expectation. Here
the mean FCS curve for S H.P. is repeated, together with
similar data
for two other young, emmetropic
Ss. Note
the
close
similarity among
all
three contrast sensitivity
curves,
particularly
at
frequencies below 2 cpd. These
data (and others not reported here)
all tend to confirm
the presence of a low-frequency inhibiting effect with a
relatively steep slope (about 2 in log-log coordinates).
DISCUSSION
adjustment curves so similar
in shape to the FCS curves.
One
should
not
assume
that
our
results
would
be
obtained
if S were instructed to detect the presence ot
a
grating, or to report
its orientation, count
its fringes, etc.
The use of other subjective criteria can doubtless change
the shape of the sine wave threshold curve.
When minimum threshold values are not required, and
occasional criterion differences among and within Ss can
be
tolerated,
the method
of adjustments
is obviously
preferable,
because
it
yields
equally smooth
curves
in
about
a 10th of the time required by the FCS method. 1
However,
the
FCS
method
eliminates
criterion
differences
and
provides
information
about
S’s
performance (not just his judgments).
Summarizing
our
results
with
five
Ss,
ranging from
naive
to quite experienced: (1) Both methods yield
the
same
curve
shape ,
but
the
FCS
method
gives
significantly greater sensitivity than that obtained by the
method of adjustments: the increase may be as great as a
factor
of
(depending
on
S’s
adjustment
criterion).
(2) Presumably
because
it
is independent of threshold
criteria,
the
FCS
method
does
not
show
systematic
changes of sensitivity from one run
to the next
(as the
method
of
adjustments
sometimes
does.)
(3) The
variability
of the FCS data
is mainly random and can
therefore
be made
quite small by
taking enough
data.
(4) When
this
is
done,
individual
differences (among
young, emmetropic Ss) tend to disappear.
These results are essentially what would be expected,
based
on
the
differences
between
the
two
psychophysical methods. We conclude
that,
if the S
is
appropriately
instructed,
the
shape
of
his
sine wave
grating
sensitivity
curve
is
not
affected by
using
the
method of adjustments. Moreover,
it seems
likely
that
this negative
result would be maintained
if the present
study
were
extended
to
other
criterion-dependent
Forced-Choice Stiircase
Subj. HP
-o-
Subj. EB
—o-
Subj. RS
_i
I
J
0.5
SPATIAL FREQUENCY
(cpd)
Instructing § to try to detect any perturbation of the
Fig. 6.
Contrast
sensitivity
vs
spatial
frequency
for
three
uniform
field
may
be
important
in
making
the
young, emmetropic Ss, obtained by the FCS technique.
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CPYRGHT
f-y 9J 91mra* MmM V*
Ti
*411111^411 Vllf^llllilftT
SINE-WAVE CONTRAST SENSITIVITY
SELECT NEW
STAIRCASE
JZ~
CONTRAST
FADING.
RESPONSE.
REINFORCEMENT
INTERFACE
CONTROL
INHIBIT
F'JPTHER
\
SELECTION
/3\
/avrr'X
sSEOUENCES,/
/
LAST
3 \
^PRESENTATIONS
\
OQNE’ /
STAIRCASE
CONTROL
/
WAS \
Jli
<1PRESENT
RESPONSE^
V.
\
RIGHT’
RESPONSE
HISTORY
N
, /
WAS
^
LAST RESPONSE
V«R"
RIGHT 7 /
/
WAS \
'RESPONSE BEFORE
XTHAT RIGHT’/
/
WAS \
Contrast change d>
\ CAST
TIME
X
3<d X
•Y/RfT
SEQUENCE
SET INCREMENT
TO NEXT
SMALLER LALUE
y
MARK CONTRAST
NOT CHANGED
J— — 4 "
\tras71
' ENT
DECREASE CONTRAST
BY INCREMENT
CONTRAST
CHANGE
Fig. 7. Flow-chart representation of the FCS computer program.
psychophysical
methods
in
general.
Thus,
our
results
tend
to support the
sine wave
threshold data obtained
by these methods.
APPENDIX
The Forced-Choice Staircase (FCS) Computer Program
V
The operation of the FCS computer program can be
divided
into
five
functional
categories:
executive,
interface control, staircase control, response history, and
contrast change (see Fig. 7).
The
executive
section of the program
initializes the
experiment, selects (from
a random table) one of the 12
stimulus patterns for presentation at each trial, performs
various bookkeeping functions, and calculates and prints
out
the
average
data
at
the
end
of
an
experimental
session. The
staircase
control
portion
of
the program
operates on a parameter table for the staircase currently
selected;
it keeps track of the previous three responses,
the
previous
eight
contrasts,
the
present
contrast, and
contrast
increment
size
(and
other
parameters
for
internal
use). These
historical
data
are needed tor each
staircase to determine its subsequent contrasts.
The interface control portion of the program controls
the
stimulator
interface,
which
operates
the
entire
sequence
of
each
trial:
stimulus
generation,
contrast
fading, marker tones, and reinforcement. When S makes
a response, the computer reads data trom the interlace,
indicating whether the
response was right or wrong (or
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