_Problem 1. First at the Left End_
Sobke was somewhat afraid of the experimenter when the investigation was
undertaken, and instead of willingly coming out of his cage when the
door was raised, he often had to be coaxed out and lured into the
apparatus with food. Whereas Skirrl was frank and rather aggressive,
Sobke was stealthy in his movements, furtive, and evidently suspicious
of the experimenter as well as of the apparatus. He was perfectly safe
to approach, but would not permit anyone to touch him. After a few days,
he began to take food from the hands of the experimenter.
Preliminary work to acquaint this monkey with the routine of the
experiment was begun on April 13. As in the case of Skirrl, he was lured
into the apparatus and was taught the route through the boxes to the
starting point by being allowed to obtain food once each day in each of
the nine boxes. The procedure was simple. The entrance door and the exit
door of a particular box were raised and the animal admitted to the
reaction-compartment and permitted to pass through the box whose doors
stood open, take its food, and return to the starting point. Sobke very
quickly learned the route perfectly and came to work steadily and
rapidly. After five days of preliminary work of this sort, he was so
thoroughly accustomed to the apparatus that it was evidently desirable
to begin with regular training experiments.
The first series of trials was given on April 19. Both punishment and
reward were employed from the first. The punishment consisted of
confinement for thirty seconds in each wrong box, and the reward of a
small piece of banana, usually not more than a tenth of a medium sized
banana for each correct choice. The total time for the first series of
trials was fourteen minutes. This indicates that Sobke worked rapidly.
My notes record that he worked quickly though shyly, wasted almost no
time, made few errors of choice, and waited quietly during confinement
in the boxes. In this, also, he differed radically from Skirrl who was
restless and always tried to escape from confinement.
Throughout the work on problem 1, punishment and reward were kept
constant. Everything progressed smoothly; there were no such
irregularities of behavior as appeared in the case of Skirrl, and
consequently the description of results is a relatively simple matter.
Sobke invariably chose the end boxes. His performance was in every way
superior to that of Skirrl.
As previously, the detailed results are presented in tabular form (table
4). From this table it appears that, whereas the expected ratio of right
to wrong first choices for this problem is 1 to 2.5, the actual ratio
for Sobke's first series was 1 to .67. This surprisingly good showing is
unquestionably due to his marked tendency to choose the end box of a
group; and this tendency, in turn, may in part be the result of the
preliminary training, for during that only one box was open each time.
But, if the preliminary training were responsible for Sobke's tendency,
it should be noted that it had very different effect upon Skirrl, and,
as will be seen later, upon Julius.
The results for the ten different settings of the doors for problem 1 as
they appear in table 4 are of interest for a number of reasons. In the
first place, the setting 1. 2. 3 appearing twice,--at the beginning of
the series and again at the end--yielded markedly different results in
the two positions. For whereas no mistakes were made in the case of
setting 1, there were fifty per cent of incorrect first choices for
setting 10. Again, satisfactory explanation is impossible. It is
conceivable that fatigue or approaching satiety may have had something
to do with the failures at the end of the series, but as a rule, as is
indicated by settings 1, 2, and 6, if correct choices were made at the
beginning, they continued throughout the day's work.
In this problem, Sobke's improvement was steady and fairly rapid, and in
the eighth series, trials 71 to 80, only correct first choices appear.
Consequently, seventy trials were required for the solution of the
problem. This number is in marked contrast with Skirrl's one hundred and
thirty-two trials.
Immediately following the first perfect series, Sobke was given two
series of control tests on April 28. Conditions were unfavorable, since
the day was stormy and the rain pattering on the sheet-iron roof made a
great din. Nevertheless, he worked steadily and well up to the sixth
trial, which was preceded by a slight delay because of the necessity of
refilling some of the food boxes. After this interruption, wrong choices
occurred in trial 6. And again after trial 9, there was brief
interruption, followed by wrong choices in trial 10. The ratio of right
to wrong choices for this first control series was therefore 1 to .25.