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