to runway D, where it awaits its next trial.

As rewards, bananas and peanuts were found very satisfactory, and
although occasionally other foods were supplied in small quantities,
they were on the whole less constantly desired than the former.

Four problems which had previously been presented to other organisms
were in precisely the same form presented to the three primates. These
problems may be described, briefly, by definition of the right reaction
mechanism, thus: problem 1, the first mechanism at the subject's left;
problem 2, the second mechanism at the subject's right (that is, from
the end of the series at the subject's right); problem 3, alternately,
the first mechanism at the subject's left and the first at its right;
problem 4, the middle mechanism of the group.

It was my intention to present these four problems, in order, to each of
the three animals, proceeding with them as rapidly as they were solved.
But as it happened, only one of the three subjects got as far as the
fourth problem. When observations had to be discontinued, Sobke was well
along with the last, or fourth problem; Skirrl was at work at the third
problem; and Julius had failed to solve the second problem.

For each of the problems, a series of ten different settings of the
doors was determined upon in advance. These settings differ from those
employed in a similar investigation with the pig only in that the
numbering of the doors is reversed. In the present apparatus, the boxes
as viewed from the front (entrance) are numbered from the left to the
right end, whereas those of the pig apparatus were numbered from the
right end to the left end.