On April 10 the apparatus was painted white in order to increase the lightness and thus render it easier for the experimenter to observe the animal’s movements, and when on April 12 Skirrl was again introduced to it for further preliminary training, he utterly refused to enter the boxes, giving every indication of extreme fear of the white floors and even of the sides of the boxes.  Finally, the attempts to induce him to enter the boxes had to be given up, and he was returned to his cage unfed.  The following day I was equally unsuccessful in either driving or tempting him with food into the apparatus.  But on April 14 he was so hungry that he was finally lured in by the use of food.  He cautiously approached the boxes and attempted to climb through on the sides instead of walking on the floor.  It was perfectly evident that he had an instinctive or an acquired fear of the white surfaces.  As the matter was of prime importance for the success of my work, I inquired of Doctor Hamilton, and of the men in charge of the cages, for any incident which might account for this peculiar behavior, and I learned that some three months earlier, while the animal cages were being whitewashed, Skirrl had jumped at one of the laborers who was applying a brush to the framework of one of the cages and had shaken some lime into his eyes.  He was greatly frightened and enraged.  Evidently he experienced extreme discomfort, if not acute pain, and there resulted an association with whiteness which was quite sufficient to cause him to avoid the freshly painted apparatus.

Having obtained an adequate explanation of this monkey’s peculiar behavior, I proceeded with my efforts to induce him to work smoothly and rapidly, and on April 15, by covering the floor with sawdust, I so diminished the influence of the whiteness as to render the preliminary training fairly satisfactory.  At the end of two more days everything was going so well that it seemed desirable to begin the regular experiment.

On the morning of April 19, Skirrl was introduced to the apparatus and given his first series of ten trials on problem 1.  This problem demanded the selection of the first door at the left in any group of open doors.  The procedure was as previously described in that the experimenter raised the entrance doors of a certain group of boxes, admitted the animal to the reaction-chamber, punished incorrect choices by confining the animal for thirty seconds, and rewarded correct choices by raising the exit door and thus permitting escape and the obtaining of food.  The trials were given in rapid succession, and the total time required for this first series of ten trials was thirty-five minutes.  Skirrl worked faithfully throughout this interval and exhibited no marked discouragement.  When confined in a box he showed uneasiness and dissatisfaction by moving about constantly, shaking the doors, and trying to raise them in order to escape.