2.  Skirrl, Pithecus irus

Box Stacking Experiment

The monkey Skirrl was tested by means of the box stacking experiment much as Julius had been.  On August 23, with a carrot suspended six feet from the floor of the large cage and three boxes in distant corners, the animal was admitted and his behavior noted.

The boxes, which were made of light, thin material, ranged in size from one six inches in its several dimensions to one twenty inches long, thirteen inches wide, and eleven inches deep.  Only by using at least two of these boxes was it possible for the animal to reach the carrot.

Immediately on admission to the cage, Skirrl began to gnaw at the boxes, trying with all his might to tear them to pieces.  After some thirty minutes of such effort, interrupted by wanderings about the cage and attempts to get at the other monkeys, he suddenly went to the largest box of all, set it up on end almost directly under the carrot, mounted it, and looked up at the food.  It was still beyond his reach and he made no effort to get it, but instead, he reached from his perch on the big box for the next smaller box, which was approximately sixteen inches, by fourteen, by twelve.  This he succeeded in pulling toward him, at the same time raising it slightly from the floor, but his efforts caused the large box to topple over and he quit work.  The experiment was discontinued after a few minutes, the total period of observation having been thirty-five minutes.

Skirrl handled the boxes with ease and with evident pleasure and interest.  He also noticed the carrot at various times during the interval, but his attention was fixed on it only for short periods.

The test was continued on August 24 when, instead of a carrot, a half banana was used as bait.  It was placed only five feet from the floor, and three boxes were as formerly placed in distant corners of the cage.  When admitted, Skirrl looked at the banana, then pulled one of the boxes toward it, but instead of mounting, he went to the smallest box and began to gnaw it.  Shortly, he mounted the middle sized box and looked up toward the banana, but the box was not directly under the bait, and in any event, it would have been impossible for him to reach it.  He next went to the largest box, gnawed it vigorously, turned it over several times, and then abandoned it for the middle sized box, from which by skillful use of his teeth and hands, he quickly tore off one side.

By this time, apparently without very definitely directed effort on the part of the monkey, all three of the boxes were in the center of the cage and almost directly beneath the banana.  Skirrl climbed up on the largest box and made efforts to pull the middle sized one up on to it, the while looking at the banana every few seconds.  He did not succeed in getting the boxes properly placed, and after a time began moving them about restlessly.