about four hundred and seventy
trials.

This method of reaction, although inadequate, proved remarkably
persistent, and it is doubtful whether it had been wholly overcome at
the conclusion of the experiment. In the case of the series of trials
given on June 8, numbered 191 to 200, the method used was either that of
the first at the right and then the next, or direct choice of the right
box.

Throughout the trials with this problem, the end boxes, numbers 1 and 9,
were avoided. This is at least partially explained by the fact that they
never existed, and obviously never could appear, in problem 2, as right
boxes. In trials 601 to 610, given on July 7, there occurred partial
return to the formerly established method of choosing the first door at
the right. This relapse was characteristic of what happened during the
many days which intervened between the definite appearance of this habit
and the final solution of the problem.

Especially in connection with such relapses, Skirrl showed extreme
fatigue or ennui and often would refuse to work and simply sit before
the open doors yawning. This happened even when he was extremely hungry
and evidently eager enough for food.

From July 12 on the hunger motive was increased by feeding the monkey
only in the apparatus and by so regulating the amount of food given in
each trial that he should obtain barely enough to keep him in good
physical condition. An increase in the number of correct choices
promptly resulted, and continued until on July 14 the ratio of choices
was 1 to .54. It appeared from these data that a relatively small number
of choices, say not more than ten a day, the rewards in connection with
which supplied the only food received by the animal, yielded most
favorable results.

On July 16, the period of confinement in wrong boxes was increased to
sixty seconds, and it was so continued for a number of days. But in the
end, it became clear that the period of thirty seconds, combined with a
liberal reward in the shape of desired food and a single series of ten
trials per day, was most satisfactory. The detailed data of table 2
indicate that at this time Skirrl was making his choices by memory of
the particular setting.

Skirrl, on July 17 was evidently hungry and eager to locate food, but
seemingly unable to select the right box. In trial 5 (765th) of the
series, he was punished by confinement in box 8. When the doors were
unlocked in order that the entrance doo