PERFORMANCE OP RHBSUS MONKEYS ON
A PORM-INTENSITY PROBLEM
ROBERT BRUCE GRAHAM, B.A.
A THESIS
IN
PSYCHOLOGY
Submitted to the Graduate Paculty
of Texas Technological College
in Partial Pulfillment of
tlie Requirements for
the Degree of
MASTER OP ARTS
Approved
June, 1959
TEXAS TKCHNnLOCICAL CULLEGE
Í.UBUOCK.. TEXAã
UfiUAIU
T3
Ho.S'J
Cop. 2*
TABLE OP CONTENTS
Page
LIST OP TABLES
lii
LIST OP PIGURES
iv
I. INTRODUCTION
1
II. METHOD
4
Apparatus
4
Subjects
6
Procedure
•
III. RESULTS
12
IV. DISCUSSION
V.
8
41
SUMMARY AND CONCLUSIONS
LIST OF REPERENCES
45
4?
ii
LIST OP TABLES
TABLE
I.
Page
Trlals Required for Relearnlng After
Intensity Equation
ili
l4
LIST OP PIGURES
PIGURE
Page
1.
Stimulus Porms Used in the Experiment
2.
Abe:
Intensity Equating Steps
3.
Abe:
Successlve Retraining Days Pollowing
the Equatlng Steps
4.
Abe:
Intenslty Reversal Steps
5.
Abe:
Successlve Retralnlng Days Pollowing
the Reversal Steps
6.
Noname:
Intensity Equating Steps
7.
Noname:
Successlve Retraining Days PolloWing
the Equating Steps
8.
Noname:
Intenslty Reversal Steps
9.
Noname:
Successive Retraining Days Pollowing
the Reversal Steps
10.
Rex:
Intensity Equating Steps
11.
Rex:
Successive Retraining Days Pollowlng
the Equating Steps
12.
Rex:
Intensity Reversal Steps
13.
Rex:
Successive Retraining Days Pollowing
the Reversal Steps
14.
Joe:
Intenslty Equating Steps
15.
Joe:
Successive Retralning Days Pollowing
the Equating Steps
16.
Joe:
Intensity Reversal Steps
17.
Joe:
Successive Retraining Days Pollowiig
18.
19.
the Reversal Steps
Mo: the
Successive
Intenslty
Equating
Equating
Retrainlng
Steps
Iv Steps
Days Pollowing
7
17
l8
19
. 19
22
22
23
23
24
24
25
25
27
28
29
29
31
V
Plgure
Page
20.
Mo:
Intensity Reversal Steps
21.
Mo:
Successive Retrainlng Days Pollowing
the Reversal Steps
22.
Jlm:
Intensity Equating Steps
23.
Jlm:
Successive Retraining Days Pollowing
the Equatlng Steps
24.
Jlm:
Intenslty Reversal Steps
25.
Jim:
Successlve Retrainlng Days Pollowing
the Reversal Steps
26.
Bo:
Intensity Equating Steps
27.
Bo:
Successive Retralnlng Days Pollowing
the Equating Steps
28.
Bo:
Intenslty Reversal Steps
29.
Bo:
Successive Retraining Days Pollowing
the Reversal Steps
30.
Tom:
Intensity Equating Steps
31.
Tom:
Successive Retrainlng Days Pollowing
the Equating Steps
32.
Tom:
Intensity Reversal Steps
33.
Tom: Successive Retrainlng Days Pollowing
the Reversal Steps
32
32
33
33
3^
34
3^
3^
37
37
38
38
39
39
CHAPTER I
INTRODUCTION
In a previous study with primates at Texas Technological College, Allison found that intensity was more effective
than form as a stimulus variable In a shock-avoidance learning situation (l). Allison's monkeys were given a task in
which the positive stlmulus object could be discriminated
from the negative one elther by its shape or by the amount
of llght being transmitted through it (intensity).
The in-
tensity difference between the positlve and negative stimuli
was effected by supplying different voltages to the light
banks behind the stimulus forms. When the subjects had
learned this dlscrimination, with both form and intensity
cues present, an attempt was made to eliminate the latter
cue by equating the voltages for both light banks.
Since in-
tensity (as defined for this study) has two aspects, the
amount of light per unit area and the total intensity of
light emitted, and the equating of voltages only eliminates
the differences in light per unit area, then it is possible
to have some intensity difference remaining after the voltage shift.
In other words, the total intenslty is dependent
on the area of the light source (stimulus form) as well as
the amount of light being emitted for each unit area.
If
two stimulus forms have dlfferent total areas then there will
also be a dlfference in total light emitted.
In Allison's study, only one palr of stimulus forms
differed greatly In area.
Hence, it Is fairly certain that
the animals were no longer able to use the intensity cue
after the equating of voltages, but instead were respondlng
to the differences in form or were making their cholces randomly.
By the time the last step in elimlnating the intensity
cue had been accomplished, all subjects were scoring below
chance.
With continued testing two out of four subjects re-
leamed the discrimination problem, apparently by form.
A
more difficult problem was then given these two animals.
The
intensity cue was reintroduced but the greater Intensity was
now assoclated with the negative form rather than the positive.
Only one animal reached criterion on this problem,
These results seem to bear out Allison's statement that "In
a shock-avoidance learning situation, intensity is more effective as a stimulus variable than is form (l)."
There is some evidence that the Wisconsin Qeneral Test
Apparatus (WGTA) presents a different situation to the primate
subject than the Shock-Avoidance Maze Apparatus (S-AMA).
In
primate studies done at Texas Technological College (2), it
was noted that some subjects learned color and form discrlminations more quickly in the WGTA than in the S-AMA.
This
difference between testing sltuations might also appear in
learnlng scores for still other test problems.
Allison's
results, then, might not apply in the WGTA situation.
From
these uncertaintlés arises the question for this study:
Will form be more readily learned in the WGTA than in the
S-AMA?
This question Is dealt with through four separate
measures of performance which will be descrlbed in Chapter
II (Procedure).
CHAPTER II
METHOD
Apparatus
A modified form of a shock-avoidance maze apparatus
described and pictured by Melching, Kaplan, and Vogt was
used (3î7).
The S-AMA consists of two identical sections,
each containing a starting box, center runway, and end box.
The two sections are Joined so that the end box of one leads
to the starting box on the other, thus providing a continuous
runway for as many trials as desired.
At the end of each
runway are two doors which swing out into the end box.
On
each of these doors a stlmulus object is mounted, one of
which is positlve, the other negative.
The door with the
negative stimulus is locked while the positive door is left
unlocked.
When the door of the starting box is raised the
monkey enters the center nmway and responds to one of the
stimulus objects by attempting to open the door to which it
is attached.
A partition between the doors, extending out
into the center runway, prevents the subject from responding
to both doors simultaneously.
If the subject makes an error
he must retrace around the center partition ajid go through
the correct door.
A Plexiglas top made observation possible.
The maze was modified by Allison (l) to present illuminated stimulus patterns.
for the present study.
This modlfication was retained
Behind each of the two doors at the
end of the center runway a bank of General Electric 7 1/2
watt (7C7A) bulbs was mounted.
A rectangular hole was cut
in each door and Plexiglas diffusing screens inserted.
A
cut-out of the stimulus form could be placed in front of
each of these screens so that the subject would view the
stlmulus as a lighted pattern.
A drawing of the Wisconsin General Test Apparatus
(WGTA)
The
may be found in an article by Meyer and Harlow (4).
WGTA
consists of a barred cage for the monkey and an
adjacent compartment in which the stimulus objects are presented,
The latter are placed on a wooden tray so that each
covers a hole In which food may be concealed.
In a discrim-
ination problem two stimulus objects are placed on the tray
wlth the food reward under the correct object.
The monkey
is allowed to move Just one of the objects on each trial.
Thus, the subject is rewarded only when he makes a correct
choice.
Modifications of the WGTA, for purposes of this experlment, were similar to those made on the S-AMA.
Holes
(about 4 1/2 inches by 4 1/2 inches) were cut in the stimulus tray, Plexiglas diffusing screens placed in the holes,
and light banks attached beneath each hole so that light
would be transmitted through the diffusing screens.
screens form the bottoms of the food wells.
These
The 5 inch
square stimulus patterns were cut out of 1/8 inch Pibreboard
and glued to 1/4 inch thick Plexiglas diffusing blocks of
the same dimensions.
When the stimulus blocks are placed
over the lighted food wells the stimulus patterns become illumlnated in the same fashion as they did in the S-AMA.
The four pairs of stimulus patterns used are shown
in Pigure 1.
All were taken from a set of twelve devised
by Melching, Reid, and Kaplan (5). These forms have all
been used In research wlth monkeys at Texas Technological
College.
Subjects
Eight male Macaque rhesus monkeys, Abe, Tom, Bo, Rex,
Jim, Joe, Mo, and Noname, were used.
With the exception of
the last monkey, all had been used by Allison in his study.
The first four, Abe, Tom, Bo, and Rex, were trained by Allison on the same series of intensity-form problems used in
this study.
The forms used in the present experiment, how-
ever, differed from Allison»s.
The next three monkeys, Jim,
Joe, and Mo, had been used by Allison on a similar problem
in whlch intensity was random with respect to form.
The
last monkey, Noname, had received training on a delayedresponse, light-dark problem In a shock-avoidance apparatus.
None of the subjects had recelved any training on a formintenslty problem in the WGTA previous to this experiment.
All animals were fed Purina Laboratory Chow supplemented
with one orange per day.
Pair 1
Pair 2
Pair 3
Pair 4
Positive
Figure 1.
Negative
Stimulus Patterns Used in the
Experiment
8
Procedure
The hypothesis that form will be more readily learned
in the WGTA was investlgated through four separate measures
of performance.
These measures were:
(1) The extent to
which the performances dropped below chance during or after
the equating of intensltles.
(2) The number of trials re-
quired to reach criterion with intenslties equated.
(3) The
extent to which the performances dropped below chance during
or after reversal of intensities.
(4) The number of trials
requlred to reach crlterlon with intensities reversed.
The procedure, then, consists of four parts which
correspond to the four measures,
Before these four main
parts of the procedure could be undertaken, the subjects had
to be trained to a statistically reliable level of performance
on a dlscrimination problem involvlng four pairs of stimuli.
Trainlng was begun with one pair.
When the crlterion (10 or
more correct out of 12 trlals for 3 consecutive days) was
reached on this pair, a second pair was added and the subject
again trained to criterion.
This procedure was continued
until the subject reached criterion with all four pairs combined.
These four stimulus pairs were used throughout all
phases of the experiment.
Each subject received 24 trials a day; 12 in the S-AMA
and 12 In the WGTA.
The order in which the animal was tested
in these two apparatuses was randomized from day to day.
ÍKils procedure was followed throughout the experiment.
As soon as the animal had performed above chance for
three consecutive days on all four stimulus pairs the actual
testing of the hypothesis began.
The stimuli provided two
dlscrimination cues; namely, a difference in intensity between the positlve and negative forms, and differences between the patterns.
The flrst of the four measures listed
above concerns the effect on performance of the removal of
one of these cues--intensity.
The intensity difference be-
tween the positive and negatlve stlrauli was reduced in 3
volt steps—1 step a day for 10 days.
The original settings
were eighty-five volts for the positive stimulus and flftyfive volts for the negative.
Most of the intensity differ-
ences had been eliminated at the end of these 10 equating
steps.
Voltages for both stlmuli were set at seventy volts
so that the amount of intensity per unit area was equivalent.
The remainlng differences in the total intensities, which
were due to the dlfferences in area between the positive and
negative stimuli, were too small to be discrimlnable by the
experlmenter.
Allison's study showed that performance would fall to
a less-than-chance level with the intensity cue ellminated.
The hypothesis of this study states that thls drop in performance level will be more pronounced in the S-AMA than in
the WGTA.
In other words, the number of days in which the
animal performs below ohanoe should be greater in
the S-AMA
10
and thé scores should be poorer.
At the end of the 10 steps of equating intensities
the subject was retralned until a statistically reliable
level of performance was reached.
The second measure con-
cerns the nuraber of trials required by the animal to regain
this level of performance, and, according to the hypothesis,
fewer trials should be necessary In the WGTA.
Some of the data in Allison*s study indicate that a
reversal of Intensitles (lesser intenslty paired with the
negative stimulus) constitutes a more difficult task than
equating of intensities.
One subject of the two who relearn-
ed the problem by form lost this ability to discriminate
when Intensity was reversed.
This was interpreted as inter-
ference, i.e., completely contrary to the prevlous training.
If this situation is more dlfficult then it would constitute
a more critlcal test of the hypothesized superlority of the
WGTA as a learning situation.
The next step in the procedure,
therefore, is to reverse the Intensity in 10 steps.
That is,
starting from seventy volts on the positlve stimulus and
seventy volts on the negative, chance to eighty-five volts
negative and fifty-five volts posltive in ten days.
measures of behavior are now available:
Two more
The extent to which
the performances drop below chance during or after this reversal of intensities, and the number of trials required to
reach criterion once more after the last step of the reversal.
In both cases performances should be superior in the WGTA.
11
t Is possible, however, that interference may not
always be inherent in the above situation.
The animal might
é,ttempt a sort of Intensity discrlmination by responding to
the lesser intensity each time.
This would neither constl-
tute an interference situatlon nor would It provide any information relevant to the hypothesls of this study.
To evaluate the results of the reversal phase the subJect was trained on a thlrd problem.
Twelve to 36 trials were
given in which Intenslty was randomized with respect to form.
When the positive form was paired with the lesser intensity
It was the only one through whlch reinforcement could be obtained, but when the negative form was paired with the lesser
intenslty the reward was avallable for either choice.
Thus
the subject would be reinforced for responding to either the
Intensity cue or the form cue.
It should become apparent,
then, which cue is being used.
If the subjects show by thls
test that they are responding to form then the data from the
second phase can be used to support or refute the hypothesis.
CHAPOER III
RESULTS
The hypothesis that learning would be easier in the
WGTA than in the S-AMA was tested by four measures of performance.
The first of these measures concerned the niimber
of animals failing to maintain above-chance performance during the 10 steps of equating intensities.
The data for this
are shown in Plgures 2, 6, 10, l4, 18, 22, 26, and 30 (pp. 17,
22, 24, 27, 31, 33, 36, 38). On the S-AMA, six of the elght
subjects dropped to chance performance while on the WGTA
only three did so.
The second measure concerned the number of trials
taken to relearn the problem after the equating of intensities.
These data are presented in Pigures 3, 7, 11, 15, 19,
23, 27, and 31 (PP. 18, 22, 24, 28, 3I, 33, 36, 38). It
should be noted that the two subjects (Tom and Tex), which
did not fall below criterion whlle intensitles were being
equated, did receive less-than-chance scores on the first
and second days immediately following the tenth step of
equating.
There were also two subjects which fell below
criterion in the WGTA post-equating trials.
All eight sub-
Jects, then, eventually dropped, in their scoring, to the
chance level in the S-AMA while only five did so in the WGTA.
Upon applylng the second measure to the data, a large
difference is found between the WGTA and the S-AMA performance
12
13
for most of the animals.
Not only is there a dlfference of^
392 trlals between the last subject to reach criterlon in
the S-AMA and the last to reach criterion in the WGTA but
there is also a greater range of errors in the S-AMA.
The
greatest number of errors for any animal in the WGTA was six
out of twelve while In the S-AMA six and seven out of twelve
was not uncommon.
Table I shows the trials to criterlon in the S-AMA
and the WGTA.
The mean difference is I60.8 trials. These
data proved to be difficult to analyze statistically.
A t^
test comparison between the S-AMA and the WGTA would have to
be one for repeated subjects.
In three cases, however, test-
ing was dlscontinued before the subject reached criterion in
the S-AMA.
Thus trials-to-crlterlon scores were available
for all subjects in the WGTA, but for only five subjects in
the S-AMA.
The data supplied by the five subjects reaching criterlon on both apparatuses were analysed statistically by
means of a t^ test.
A t^ value of 2.24 was obtained.
A value
of 2.77 was necessary to reach the O.05 level of confidence.
The data supplied by Abe and Bo were not included in
the above test of significance because their performance
never reached criterion.
They were run for 348 and I56
trlals, respectively, before their testing was discontinued.
A t^ test between the S-AMA and the WGTA performances for all
animals, except Noname, ylelded a value of 3.24.
This was
14
TABLE I
TRIALS REQUIRED POR RELEARNING APTER INTENSITY EQUATION
Subject
WGTA
releaming
trials
Abe
60
348*
+ 288
Rex
120
204
+ 84
Joe
48
492
+ 444
Mo
84
168
+ 84
Jim
36
96
Bo
36
156*
+ 120
Tom
36
168
+ 132
Total
420
1632
+1212
64.8
Mean
*
S-AMA
releamlng
trials
225.6
Difference
+
60
+ 160.8
Testing discontinued before criterlon was reached
15
significant beyond the 0.02 level.
The inclusion of the data
from the two monkeys, Abe and Bo, is a departure from the
normal procedure, however.
Consequently, a sign test was
performed, with the two incomplete sets of data included.
In the case of the sign test the degree of difference is irrelevant, as the direction of the difference is the only
thing being considered.
Whether or not all the animals
reached criterion, then, is unlmportant for this statistic.
The results of the test show a p < .01 for the S-AMA - WGTA
difference.
All signs were in favor of the WGTA for faster
learning.
The third measure of performance concemed the number
of subjects receiving less-than-chance scores durlng the reversal of intensitles.
Reversal scores are available for
all eight subjects in the WGTA but only four reached the reversal stage in the S-AMA.
All four of these subjects even-
tually received below-chance scores in the S-AMA (see Pigures
4, 8, 12, 16, 20, 24, 28, and 32; pp. 19, 23, 25, 29, 32, 34,
37, 39). Qnly one of them, Rex, scored below criterion in
the WGTA.
When discrimination was lost, the drop in perform-
ance was more severe in the S-AMA than in the WGTA.
It
should be noted that all subjects but one scored above the
chance level on step 20 In the WGTA.
The data for the fourth measure (which concerned the
number of retraining trlals following intensity reversal)
are shown in Pigures 5, 9, 13, 17, 21, 25, 29, 33 (pp. 19,
16
23, 25, 29, 32, 3^s 37, 39). Seven subjects reached criterlon In the WGTA, while only three did so in the S-AMA.
The maximum number of trials to criterion for any subject in
the WGTA was 84 as opposed to 2l6 in the S-AMA.
These data
were not considered suitable for statistical treatment as
there were only three subjects common to each experimental
condition.
To check the possibility that the subjects might have
been respondlng with a reversed intensity dlscrimlnation,
twelve trials were given with intensity random with form
(see Procedure).
the S-AMA.
Scores were obtained for three subjects in
All were above criterion on the form variable
but below wlth respect to the lesser intensity.
data were obtained for six subjects in the WGTA.
The same
The sub-
Jects that reached criterion after reversal then, apparently,
did so by learning form.
The remainder of the results will
be dlscussed in case history form.
Abe.
On the prellminary training (leaming the four
stimulus pairs), Abe required 228 trials to reach criterion
in the S-AMA and 312 in the WGTA (see Plgures 2, 3, 4, and
5).
As soon as these preliminary discriminations were
leamed, equating of intensities began.
In the S-AMA per-
formance fell below chance on the third step (day).
Por
seven days the animal performed below criterion with a position habit developing on the fifth day and remaining throughout the rest of the steps.
The development of a posltion
17
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hablt (responding ålwáys to one slde régårdless of which dôôr
is open) at this point in the training constltutes a sort of
"regressive" behavior and seems to imply that the animal has
reached a point where the problem demands more than he csm
glve.
(The term "regressive" here refers to the fact that
many animals seem to lesim
a discrimination by successive
elimination of progressively more complex **hypotheses" until
one is reached by which the animal is successful in securing
the reward.
Return to a prevlous, unsuccessful "hypothesis"
jnight be termed "regression.")
In the WGTA, below-criterion
scores occurred on Steps 7, 8, and 10. At no time, however,
did the daily score drop below 8.
During the retraining trials in the S-AMA the position
habit persisted for the first 264 trials.
This was corrected
by placing the positive stimulus on the side not chosen by
the animal until the undesirable habit was eliminated.
As
soon as the experimenter began, once more, to provide rein'forcement on each side 50 per cent of the time, the subject
immedlately returned to hls position habit.
Apparently,
then, learning was impossible and testing in the S-AMA was
discontinued for this animal.
Retraining in the WGTA re-
qulred only 48 trials with the subject scoring below criterion for Just one day.
Durlng the reversal trials in the WGTA, half of the
scores were ten or above; releaming took place in seven
days.
21
Noname.
'niis subject requlred 684 trials in the
S-AMA and 348 trials in the WGTA to reach criterion for the
preliminary training (see Pigures 6, 7, 8, and 9).
During
the steps of equating intensities, less-than-chance scores
occurred on the second day In the S-AMA and on the seventh
day in the WGTA.
In the latter situation the scores were
never less than 9 while in the former they dropped to 5,
the pattem of scoring indicating a developing position
habit,
Plve days were spent below criterion in the WGTA
agalnst seven in the S-AMA.
S-AMA testing was discontinued after Step 10. Although WGTA testing began on the same day as the S-AMA testing this subject finished all four stages of WGTA work before he completed even the preliminary leaming in the S-AMA.
Retraining following intensity equating (WGTA) required three
days.
Perfonnance fell below chance during intensity rever-
sal and releaming was obtained in 6o trials.
Rex.
This subject took l44 trials to reach criterion
on his preliminary training in the S-AMA and 444 trials in
the WGTA (see Pigures 10, 11, 12, and 13).
Rex was one of
the two monkeys that did not receive less-than-chance scores
in the S-AMA during equating.
His scores also remained above
criterion throughout the steps of equating Intensities in
the WGTA.
Discrimination did break down, however, in both
situations directly following the intensity equating.
The
lowest score in the maze was 5 while in the WGTA it was 9.
22
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In the S-AMA twelve days were spent below criterion agalnst
three in the WGTA.
Below-chance scores occurred again on Step 11 (intensity reversal) in the S-AMA and on the thirteenth step in
the WGTA.
The extent of the discrimination breakdown was
again more severe in the S-AMA, as Judged by the number of
below-criterion scores and the extent to which they were below the criterion.
Performance on the last few steps, in
fact, showed the beginning of a position habit.
Attempts
at breaking the habit continued through 120 subsequent retraining trlals with no success.
There were less-than-chance
scores on only three days of the WOTA reversal steps, with
9 being the score on the last step.
Training was discon-
tinued after Step 20.
Joe.
Joe took 156 trials in the S-AMA and 372 trials
in the WGTA to reach crlterion on the preliminary training
(see Flgures 14, 15, 16, and 17). He received less-thanchance scores on the sixth day in the S-AMA
through four of the last five steps.
and lasted
In the WGTA a high
level of performance was maintained until the tenth step of
equating intensities, and retraining occurred in only 48
trials.
Joe required more trials than any other subject to
reach criterion in the S-AMA (see Pigure 5).
He took exactly
ten times as many trials in the S-AMA as he did in the WGTA.
Training in the S-AMA was discontinued before the reversal of
intenslties.
27
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50
Discrimination was malntained throughout the intensity
reversal trials in the WGTA so that retrainlng was effected
in three days.
Mo.
This subject reached criterion on the preliminary
trainlng for the S-AMA and the WGTA in 192 and 288 trials,
respectively (see Plgures 18, 19, 20, and 21). During equating in the S-AMA, Mo's performance fell below criterion and
a position habit developed, which lasted through seventy-two
trials of the retraining perlod.
Discrlmlnation was not lost
during the ten steps in the WGTA.
One below-criterion score
of 6 (out of 12 correct) occurred on the first day of the retraining trials but on the following day a score of 12 was
obtained.
After one more day below criterion retraining was
completed.
Intensity reversal resulted in discrimination breaJcdown in the S-AMA and a subsequent 2l6 retraining trials.
In
contrast, there was no breakdown in the WGTA and hence only
36 retralning trials.
Jim.
Jim reached criterion on the preliminary train-
ing in 180 trials for the S-AMA and 484 for the WGTA (see
Pigures 22, 23, 24, and 25). During the equating of intensities in the S-AMA his performance went below criterion on
Steps 5 and 7, rose to criterion on Steps 9 and 10, and then
fell below once more.
Retraining required 96 trlals. Dis-
crimination continued in the WGTA during and following the
equating steps.
51
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35
The contrast between the two test situations was even
more pronounced during the reversal steps and the subsequent
retraining,
Near perfect scoring was obtained in the WGTA,
while in the S-AMA the discrimination habit broke down pronouncedly and releaming was slow.
Ject's score dropped to 2.
At one polnt the sub-
A position hablt occurred during
the retralnlng and was broken in 84 trials with weighted
pattems.
Bo.
To reach the criterion for the preliminary train-
ing thls subject requlred 324 trials in the S-AMA and 204 in
the WGTA (see Plgures 26, 27, 28, and 29).
Hls performance
on the intensity-equating phase resembled that of the other
subjects in that he maintained an above-chance level of scoring in the WGTA and fell to below-chamce performance in the
S-AMA.
The first indicatlon of habit break-down in the equat-
ing phase occurred on the fourth step, with four days in all
spent below criterion.
l44 trials.
Retraining was discontinued after
Thirty-six trials were required to reach cri-
terlon in the WGTA.
Reversal of intensities in the WGTA pro-
auced a fall to less-than-chance scoring followed by a quick
retum to a significant level of performance.
Tom.
Thls subject required l80 trials in the S-AMA
and 204 trlals in the WGTA to reach criterion on the preliminary training (see Flgures 30, 31, 32, and 33). Discrimination was maintained durlng the equating phase In both the
S-AMA and the WGTA, but performance became less-than-significant
36
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40
in the S-AMA trials immediately following equating of intensitles.
Retraining was accomplished in l68 trials. Identi-
cal results were obtained for the reversal stages with l68
trials required to relearn the problem in the S-AMA.
CHAPTER IV
DISCUSSION
In general, the data from this study tend to verify
Allison's finding that intensity was more effective as a cue
than was form.
In the S-AMA the subjects performed at a
higher level than they dld in Allison's study, but this can
probably be attributed to practice.
Even though Allison's problem was very similar to the
S-AMA problem of this study the subjects exhibited the same
difficulty in using the form cues and apparently responded,
In most cases, to intensity.
Practice, then, did not seem
to have any appreciable Influence on the effectiveness of
form as a cue in conjunction with intensity.
The hypothesis that form would be more readily leamed
in the WGTA was verified.
Positive results were obtained
with all four measures of performance.
The way is now open for future research on the nature
of thls difference between the apparatuses.
The motivational
aspects of the situation probably provide the best source of
hypotheses.
The nature of the incentives used in the two
apparatuses is particularly interesting.
In the WGTA food
is glven as a reward for the correct choice; in the S-AMA
the incentive sltuation is not as clear. Before a naive
monkey can be used in any apparatus he must be put through
a perlod of pre-training called "wlsing."
41
Thls is equivalent
42
to^ giving him Instruøtions as to what he 1» to da in the
apparatus.
In the WGTA he is first taught to surmount his
fears and take a grape from the stimulus tray, then to move
a block in order to obtain the grape undemeath, and lastly
to choose correctly between two stiraulus blocks.
S-AMA the "wising"
In the
procedure is possibly quite different in
its theoretical implications.
The animal is placed in the
first compartment and the door to the next compartment is
raised.
If the animal does not move, a mild shock is applied
through the floor-grid, producing wild and frantic movements
which eventtially coordlnate into a running response.
If the
monkey stops before he reaches the end compartment he is
shocked again.
The end compartment is "safe" until the door
to the next compartment is opened.
Again, if the monkey
does not run through the door he is shocked.
What the sub-
Ject learns, then, is to run when the door is opened and not
to pause between end compartments.
After the running re-
sponse is firmly established he is ready to be given a discrimination problem.
While he is leaming this discrimina-
tion it is rarely necessary to use the shock.
The animal is
being constantly reinforced in the WGTA, then, and is on
extinction in the S-AMA.
Another point to be noted is that there is no readily
discernable association between the incentive (shock) and
the discrlmination response to the correct door in the choice
compartment.
The animal was taught to run from the start
4-3
compa"?tment to the end box, but as iong as he was moving he
was not shocked.
Thus the incentive was associated with the
act of running but not necessarily with the response to one
particular stimulus.
If shock had been given for incorrect
responses the S-AMA procedure would have been analogous to
that of the WGTA.
However, the shock incentive was never
directly connected with the discrimination itself, but only
with the running.
Possibly the most significant aspect of the S-AMA
procedure, with regard to incentive, is the fact that It involved a correction technique, whereas the WGTA procedure
allowed no correction.
Thus, in the S-AMA the animal which
chose the wrong door retraced and opened the correct one,
In the WGTA he was allowed to move only one block on any one
trial.
The hypothesis that can be drawn is that the incen-
tive to leam the discrimination was weaker in the S-AMA
than in the WGTA.
This hypothesis could easily be tested
by giving naive monkeys a food reward for each correct choice
in the S-AMA
WGTA.
while malntalning the normal procedure in the
The difference between the apparatuses should be sub-
stantially reduced under these conditions, or fail to appear
at all.
Motivational differences are by no means the only
factors that could be responsible for the scoring differences demonstrated by this study.
The physical differences,
such as vertical (S-AMA) vs horizontal (WGTA) stimuli or the
44
différence In levels of backgro\md illumination, might influence the scoring.
The fact that more effort is required
of the monkey in pushing open the S-AMA doors might even be
considered relevant.
Studies are now in progress at Texas
Technolo^ical College to investigate some of these variables.
CHAPTER V
SUMMARY AND CONCLUSIONS
This study grew out of previous work at Texas Technological College which had indicated that:
(l) Intensity is
a more effective cue than form in a shock-avoidance leaming
situation; (2) There may be differences in performance in
the Wisconsin Oeneral Test Apparatus and Shock-avoidance
Maze Apparatus.
This study was designed to discover whether
form can be more readily leamed in the WGTA than in the
S-AMA.
Eight rhesus monkeys were trained on the same multiple
discrimination problem in both the S-AMA and WGTA.
The prob-
lem consisted of four pairs of stimuli differing in both
form and intensity.
The intensities were then equated be-
tween positive and negative stimuli, leaving only the form
cue.
The resulting loss of discrimination occurred more
often and with a greater drop in scoring in the S-AMA than
in the WGTA.
The monkeys were retrained to criterion on the form
cue and an intensity difference was reintroduced in such a
manner that the positive form was now paired with the negative intensity.
The resulting drop in performance was again
greater in the S-AMA.
The subjects were once more trained
to criterion and in both cases of retraining the speed of
relearning was greater in the WGTA.
45
46
It was concluded that a leaming difference existed
between the two apparatuses with the faster leaming occurring
in the WGTA.
A hypothesis, based on Incentive condition, was
presented as a possible explanation of the difference.
Now
that it has been shown that primates will perform differently
in two dissimilar apparatuses, while being tested on the
same problem, future research can be directed at the nature
of this difference.
47
LIST OP REFERENCES
|
(1) J, T. Allison. "The Relative Importance of Intensity
and Porm in Multiple Discriminatlon Leamlng by
Monkeys." Unpublished Master's Thesis, Texas Technologlcal College, 1957.
(2) S. J. Raplan and K. S. McCutchan. Unpublished Research
Done at Texas Technological College, 1956, 1957.
(3) William H. Melching, Sylvan J. Kaplan and Robert Vogt.
"Behavior Test Apparatus Employing Shock Motivation
with Monkeys," USAF School of Avlation Medicine,
Project No. 21-^501-0003,fteportNo. 5. Aprll, 1954,
pp. 1-5.
(4) D. R, Meyer and H. P. Harlow. "The Development of Transfer of Response to Patteming by Monkeys," Journal
of Comparative and Physiological Psychology, 42
11949); P. 455.
(5) William H. Melchlng, Jackson B. Reid and Sylvan J. Kaplan. "An Investigation of Concept Pormation in
Transfer of Trainlng," USAP School of Aviatlon
Medlcine, Pro^ect No. 21-3501-0003, Report No. 13.
December, 1954, pp. 1-13.
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