y and rarely thirty trials were given on
the same day. In such cases the series of settings was simply repeated.
The only pause between trials was that necessary for resetting the
entrance doors and replenishing the food which served as a reward for
success.

III

RESULTS OF MULTIPLE-CHOICE EXPERIMENTS

1. Skirrl, _Pithecus irus_

_Problem 1. First at the Left End_

Systematic work with the multiple-choice apparatus and method described
in the previous section was undertaken early in April with Skirrl,
Sobke, and Julius. The results for each of them are now to be presented
with such measure of detail as their importance seems to justify.

Skirrl had previously been used by Doctor Hamilton in an experimental
study of reactive tendencies. He proved so remarkably inefficient in the
work that Doctor Hamilton was led to characterize him as feeble-minded,
and to recommend him to me for further study because of his mental
peculiarities. With me he was from the first frank, aggressive, and
inclined to be savage. It was soon possible for me to go into the large
cage, Z, with him and allow him to take food from my hand. He was
without fear of the experimental apparatus and it proved relatively easy
to accustom him to the routine of the experiment. Throughout the work he
was rather slow, inattentive, and erratic.

Beginning on April 7, I sought to acquaint him with the multiple-choice
apparatus by allowing him to make trips through the several boxes, with
the reward of food each time. Thus, for example, with the entrance and
exit doors of box 7 raised, the monkey was allowed to pass into the
reaction-compartment E and thence through box 7 to the food cup. As soon
as he had finished eating, he was called back to D by the experimenter
and, after a few seconds, allowed, similarly, to make a trip by way of
one of the other boxes. By reason of this preliminary training he soon
came to seek eagerly for the reward of food.

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 fo