thout change in
experimenter, or method of procedure, and above all without the
disturbance of the painting, Sobke might have solved problem 4 within a
few days. This is by no means certain, however, for in problems 2 and 3
the ratio of right to wrong choices instead of increasing steadily
increased very irregularly.

The detailed results for this problem are given in table 7. Reactive
tendencies which appear are: (a) persistent choice of the end boxes
followed, subsequently, by (b) the tendency to locate the middle box
directly. This proved fairly easy when the number of boxes involved was
only three as in settings 1, 4, 7, and 10. Setting 4 was most difficult
of all, because box 9 was avoided or ignored. When the number of open
boxes was as great as five, as in settings 2 and 8, the task was
obviously more difficult, but whereas success in setting 2 appeared
early, in setting 8 it failed to appear during the course of
experimentation. For the settings 3, 6, and 9, involving either seven or
nine open boxes, the direct choice of the middle box was next to
impossible, and Sobke tended to choose, first of all, a particular box
toward one end of the series, for example, box 2, in setting 3, and box
7 in setting 9. To the experimenter, as he watched the animal's
behavior, it looked as though effort each time were being made to locate
the middle member of the group. This appeared relatively easy for groups
of three boxes, extremely difficult for as many as five boxes, and
almost impossible for seven or nine.

3. Julius, _Pongo pygmaeus_

_Problem 1. First at the Left End_

The orang utan, Julius, was gentle, docile, and friendly with the
experimenter throughout the period of investigation. He at no time
showed inclination to bite and could be handled safely. As contrasted
with Skirrl and even with Sobke, he adapted himself to the
multiple-choice apparatus very promptly, and only slight effort on the
part of the observer was necessary to prepare him, by preliminary
trials, for the regular experiments. But in order to facilitate work, he
was familiarized with the apparatus by means of regular route training
and feeding in the several boxes from April 5 to April 9.

On April 10 the apparatus was painted white as has been stated
previously, and on the following Monday, April 12, Julius when again
introduced to it gave no indications of fear, uneasiness, or dislike,
but worked as formerly, making his round trips quickly a