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[Footnote 1: End of series on May 4.]

By reading downward in any particular column of results, one obtains a
description of the changes in the animal's reaction to a particular
setting of the doors. Thus, for instance, in the case of setting 1,
which was presented to the animal in trials numbered 1, 11, 21, and so
on to 141, it is clear from the records that no definite improvement
occurred. But oddly enough, in the case of setting 10, which presented
the same group of open doors, almost all of the reactions are right in
the lower half of the column. For setting 2, it is evident that mistakes
soon disappeared.

Comparison of the data of table 1 indicates that the number of correct
first choices is inversely proportional to the number of doors in use,
while the number of choices made in a given trial is directly
proportional to the number of doors in use.

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 reac