It was my aim so far as possible to present to a given subject each day the ten settings under a given problem in order, without interruption.  If for any reason the series of observations had to be interrupted, it was resumed at the same point subsequently.  Occasionally it was found desirable or necessary to present only five of the series of ten settings in succession and then to interrupt observations for an interval of a few minutes or even several hours.  But as a rule it was possible to present the series of ten settings.  All things being considered, it proved more satisfactory to give only ten trials a day to each subject.  Frequently twenty 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.