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 door might be raised to release him, the lock-bar, sliding under the floor, made a slight grating noise, and the instant the entrance door was opened, he jumped out excitedly. He made no outcry, but as soon as he was out of the box, sat down, and taking up his right hind foot, examined it for a few seconds. Having apparently assured himself that nothing serious had happened, he went on unconcernedly about his task.  The presumption is that the sound of the lock-bar, associated as it was with his painful experience in