546 



THE CENTURY MAGAZINE 



with a Cebus monkey as one can well im- 

 agine. 



A somewhat detailed account of the first 

 regular experiment will set in relief the 

 method which I used. The first experi- 

 ment cage was approximately three by four 

 by six feet. The back and one end were of 

 boards, while the front and the other end 



DIAGRAM OF THE FIRST 



EXPERIMENT CAGE 



A, trap-door ; B, device to hold door closed ; C, chute ; 

 D, string, the pulling of- which opened the trap- 

 door ; E, piece of iron fastened to the end of 

 the string; F, cap covering top of chute. 



were of mesh wire. In the top of the cage, 

 near the wire front and the wire end, was 

 a door four inches square which opened 

 inward, and was held shut by a device on 

 top of the cage. At a point in the top, 

 nearer the board end and the back, a hol- 

 low chute two and a half inches square 

 projected perpendicularly into the cage 

 about two feet. From the device which 

 held the door shut, a string passed to the 

 chute, and hung down on the inside to 



within four inches of the bottom. The top 

 of the chute was covered so that no light 

 could come through. In order to secure 

 food, the monkey must leap from the wire 

 part of the cage to the chute, and, while 

 holding to it, must thrust a hand up in- 

 side and pull the string, thereby releas- 

 ing the small door in the top of the cage 

 and allowing the food which had been 

 placed on it to fall to the floor. He 

 must then descend to the floor to get the 

 food. 



To give the monkeys a fair chance to 

 learn the act, each was tried alone for 

 thirty minutes a day for several days. Jack 

 was first put into the cage on January 4. 

 Within a few minutes he had jumped to 

 the chute, but he took no notice of the end 

 of it. On the second trial, his random 

 leaps so jarred the cage that the food-door 

 in the top of the cage dropped open and 

 the peanuts fell to the floor. He ate the 

 nuts and then climbed the wire. Holding 

 with his feet, he reached the swinging door 

 with his hands, and thrust his head up 

 through the opening. He had made one 

 necessary association on the road to solv- 

 ing the problem: he knew where the food 

 came from. On January 8 he made more 

 progress. He was active about the cage, 

 and on his seventh leap to the chute he 

 threw his head and shoulders downward 

 while hanging by his tail and feet. He 

 looked up the chute; then up went a hand, 

 and a moment later there came a vigorous 

 pull which opened the trap, and the pea- 

 nuts rolled on the floor of the* cage. Down 

 he went for the food, and I thought Jack 

 had learned. However, I was too gener- 

 ous in my interpretation, for during the 

 remaining twenty minutes he played about 

 the cage, jumping to the chute twenty 

 times, but never once displaying the slight- 

 est indication that he knew of an opening 

 in the end of it. It required three more 

 days for him to learn to satisfy his hunger 

 by pulling the string. On January 20 he 

 operated the mechanism ten times in 

 twenty-seven minutes. I then counted him 

 to have learned the trick. 



Jill was not so fortunate. She had her 

 first experience in the experiment cage on 

 January 7, and being hungry, she scolded 

 and chattered most of her thirty minutes. 

 Despite her impatience, she searched the 

 floor for food and climbed the wire, but I 

 could not tell that she even looked at the 



