========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========
| No. | S.1 | S.2 | S.3 | S.4 | S.5 | S.6 | S.7 | S.8 | S.9 | S.10 | | | | | Ratio
Date | of | | | | | | | | | | | R | W | R | W | of
| trials | 1.2.3 | 8.9 | 3.4.5.6.7 | 7.8.9 | 2.3.4.5.6 | 6.7.8 | 5.6.7 | 4.5.6.7.8 | 7.8.9 | 1.2.3 | | | | | R to W
--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+--------
April | | | | | | | | | | | | | | | |
19 | 1-10 | 1 | 8 | 3 | 9.7 | 6.2 | 6 | 7.5 | 4 | 9.7 | 1 | 6 | 4 | 6 | 4 | 1:0.67
20 | 11-20 | 1 | 8 | 3 | 7 | 2 | 6 | 7.5 | 8.4 | 9.9.7 | 1 | 7 | 3 | 7 | 3 | 1:0.43
21 | 21-30 | 1 | 8 | 4.3 | 9.7 | 2 | 6 | 5 | 8.4 | 7 | 1 | 7 | 3 | 7 | 3 | 1:0.43
22 | 31-40 | 1 | 8 | 3 | 7 | 6.2 | 6 | 6.5 | 4 | 7 | 3.1 | 7 | 3 | 7 | 3 | 1:0.43
23 | 41-50 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 9.7 | 3.1 | 8 | 2 | 8 | 2 | 1:0.25
24 | 51-60 | 1 | 8 | 3 | 9.7 | 2 | 6 | 5 | 4 | 7 | 2.1 | 8 | 2 | 8 | 2 | 1:0.25
26 | 61-70 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 3.1 | 9 | 1 | 9 | 1 | 1:0.11
27 | 71-80 | 1 | 8 | 3 | 7 | 2 | 6 | 5 | 4 | 7 | 1 |10 | 0 |10 | 0 | 1:0.00
--------+-----------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+---+---+---+---+--------
| | | | | | | | 2.3.4 | | | 1.2.3.4.5 | | | | |
| | 2.3.4 | 6.7.8.9 | 3.4.5 | 4.5.6.7.8.9 | 6.7.8.9 | 1.2.3.4.5 | 5.6.7.8 | 3.4.5.6.7.8 | 5.6.7 | 6.7.8.9 | | | | |
| +--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+--------------+ | | | |
28 | 1-10 | 2 | 6 | 3 | 4 | 6 | 5.4.1 | 2 | 3 | 5 | 5.4.2.1 | 8 | 2 | | |
" | 11-20 | 2 | 6 | 3 | 4 | 6 | 2.1 | 2 | 3 | 5 | 1 | 9 | 1 |17 | 3 | 1:0.18
| | | | | | | | | | | | | | | |
========+===========+==============+==============+==============+==============+==============+==============+==============+==============+==============+==============+===+===+===+===+========
Six minutes after completion of the first control series, a second was
given under slightly more favorable conditions, and in this only a
single wrong choice occurred, in that box 2 was first chosen in trial 6
instead of box 1. From the results of these two control series, it is
evident that Sobke's solution of problem 1 is reasonably adequate. He is
easily diverted or disturbed in his work by any unusual circumstances,
but so long as everything goes smoothly, he chooses with ease and
certainty. Whether it is fair to describe the behavior as involving an
idea of the relation of the right box to the other members of the group
would be difficult to decide. I hesitate to infer definite ideation from
the available evidence, but I strongly suspect the presence of images
and relatively ineffective or inadequate ideation.
It is perfectly evident that Sobke is much more intelligent than Skirrl.
In practically every respect, he adapted himself more quickly to the
experimental procedure and progressed more steadily toward the solution
of the problem than did Skirrl. The contrast in the learning processes
of the two monkeys could scarcely be better exhibited than by the curves
of learning which are presented in figure 18. The first, that for Sobke,
is surprisingly regular; the second, that for Skirrl, is quite as
surprisingly irregular. These results correlate perfectly with the
steadiness and predictability of the former's responses and the
irregularity and erraticness of the latter's.
_Problem 2. Second from the Right End_
On the completion of problem 1 Sobke was in perfect condition, as to
health and training, for experimental work. He had come to work quietly,
fairly deliberately, and very steadily. His timidity had diminished and
he would readily come to the experimenter for food, although still he
was somewhat distrustful at times and became timid when anything unusual
occurred in the apparatus.
As preparation for problem 2, a break in regular experimentation
covering four days followed the control series of problem 1. On each of
these four days the monkey was allowed to get food once from each of the
nine boxes, both doors of a given box being open for the trial and all
other doors closed. For this feeding experiment, the doors were opened
in irregular order, and this order was changed from day to day.
Systematic work with problem 2 began on May 3, with punishment of thirty
seconds for mistakes and a liberal reward of food for each success.
Early in the series of trials it was discovered that Sobke was likely to
become discouraged and waste a great deal of time unless certain aid
were given by the experimenter. On this account, after the first two
trials, the method was adopted of punishing the animal by confinement
for the first ten mistakes in a trial, and of then, if need be,
indicating the right box by slightly and momentarily raising the exit
door. Every trial in which aid was thus given by the experimenter is
indicated in table 5 by an asterisk following the last choice. In the
first series of trials for this problem, aid had to be given in seven of
the ten trials, and even so the series occupied seventy-one minutes. It
is possible that had no aid been given, the work might have been
continued successfully with a smaller number of trials than ten per day.
But under the circumstances it seemed wiser to avoid the risk of
discouraging and thus spoiling the animal for use in the experiment. It
should be stated, also, that it proved impossible to adhere to the
period of thirty seconds as punishment in this series. For the majority
of the wrong choices confinement of not more than ten seconds was used.
For the second series, given on May 4, the conditions were unfavorable
in that it was dark and rainy, and the noise of the rain on the roof
frightened Sobke. He refused to work after the fourth trial, and the
series had to be completed on the following day. The total time required
for this series was seventy-eight minutes.
The work on May 6 was distinctly better, and the animal's behavior
indicated, in a number of trials, definite recognition of the right
door. He might, for example, make a number of incorrect choices, then
pause for a few seconds to look steadily at the doors, and having
apparently found some cue, run directly to the right box. No aid from
the experimenter was needed in this series.
On the following day improvement continued and the animal's method of
choosing became definite and fairly precise. He was deliberate, quiet,
and extremely business-like. The time for the series was thirty-one
minutes.
The period of punishment was increased on May 12 to thirty seconds.
Previously, for the greater number of the trials, it had been ten to
fifteen seconds. This increase apparently did not disturb the monkey,
for he continued to work perfectly throughout the series, although
making many mistakes in spite of deliberate choices and the refusal of
certain boxes in each trial.
An interesting and significant incident occurred on May 13 when at the
conclusion of trial 5, Doctor Hamilton came into the experiment room for
a few minutes. Sobke immediately stopped working, and he could not be
induced to make any choices until Doctor Hamilton had left the room.
This well indicates his sensitiveness to his surroundings, and his
inclination to timidity or nervousness even in the presence of
conditions not in themselves startling.
Work was continued thus steadily until May 28 when, because of the
failure of the animal to improve, it seemed wise to increase the period
of confinement as punishment to sixty seconds. In the meantime, it had
sometimes been evident that Sobke was near to the solution of his
problem. He would often make correct choices in three or four trials in
succession and then apparently lose his cue and fail utterly for a
number of trials.
After June 1, in order to hasten the solution of the problem, two series
per day were given. In some instances the second series was given almost
immediately after the first, while in others an interval of an hour or
more intervened. It was further found desirable to give Sobke all of his
food in the apparatus. When the rewards obtained in the several trials
did not satisfy his hunger, additional food was presented, on the
completion of the series of experiments, in one or more of the food
cups. On days marked by unwillingness or refusal to work, very little
food was given. Thus, the eagerness of the monkey to locate the right
box was increased and, as a matter of observation, his deliberateness
and care in choice increased correspondingly. Sixty seconds punishment
was found satisfactory, and it was therefore continued throughout the
work on this problem.
It was evident, on June 9, from the behavior of the monkey as well as
from the score, that the perfect solution of the problem was near at
hand. This fact the experimenter recorded in his daily notes, and sure
enough, on the following day Sobke chose correctly throughout the series
of ten trials. The time for this series was only ten minutes. The
choices were made deliberately and readily.
An analysis of the data of table 5 reveals five methods or reactive
tendencies which appeared more or less definitely in the following
order: (a) Choice of first box at the left, because of experience in
problem 1. This tendency was very quickly suppressed by the requirements
in connection with problem 2. Indeed one of the most significant
differences which I have discovered between the behavior of the primates
and that of other mammals is the time required for the suppression of
such an acquired tendency. The monkey seems to learn almost immediately
that it is not worth while to persist in a tendency which although
previously profitable no longer yields satisfaction, whereas in the
crow, pig, rat, and ring dove, the unprofitable mode of response tends
to persist during a relatively large number of trials. (b) The tendency
to choose, first, a box near the left end of the group, to go from that
to the box at the extreme right end of the group, thence to the one next
in order, which was, of course, the right box. This tendency appears
fairly clearly from May 7th on. (c) The box at the extreme right was
first chosen and then the one next to it. For example, in setting 2, box
4 would be chosen first, then box 3. Or, if this did not occur, the
method previously described under (b) was likely to be employed, as for
example, in setting 8, where such choices as 7.6.5.1.8 appear. (d) In
certain series there appeared a marked preference for a particular box,
usually box 3 (see results for May 24). This was doubtless due in a
measure, if not wholly, to the fact that box 3 was the right box twice
in each series of ten settings. But it should be added that the same is
true of box 7, for which no preference was manifested at any time. (e)
Direct choice of the right box.
The five reactive methods or tendencies enumerated above roughly
appeared in the order named, but there were certain irregularities and
the order as well as the time of appearance varied somewhat from setting
to setting. In general, method c was the most frequently used prior to
the development of method e, the direct choice of the right box.