During the first week of work on this problem, Skirrl improved markedly.
His performance was somewhat irregular and unpredictable, but on the
whole the experiment seemed fairly satisfactory. Cold, cloudy, or rainy
days tended to diminish steadiness and to increase the number of
mistakes. Similarly, absence of hunger was unfavorable to continuous
effort to find the right box.

The period of confinement, as punishment for wrong choices, was
increased from thirty seconds to sixty seconds on April 26. But there is
no satisfactory evidence that this favored the solution of the problem.
Work on May 4 was interrupted by a severe storm, the noise of which so
distracted the monkey that he ceased to work. Consequently, observations
were interrupted on the completion of trial 132, and on May 5, the
series was begun with setting 3. On this date, eighteen trials were
given in succession, and in only one of them did a mistake occur. Since
the ten trials numbered 133 to 142 were correct, Skirrl was considered
to have solved problem 1, and systematic training was discontinued.

On the following day, as a measure of the extent to which the animal had
learned to select the first door at the left no matter what its position
or the number of doors in the group presented, a control series was
given in which the settings differed from the regular series of
settings. These supplementary settings are presented at the bottom of
table 1 together with the records of reaction in ten trials.

Since in only six of these ten control settings was the first choice
correct, it is scarcely fair to insist that the animal was reacting on
the basis of an ideational solution of the problem. Rather, it would
seem that he had learned to react to particular settings. A careful
study of all of the data of response, together with notes on the varied