550 



THE CENTURY MAGAZINE 



NO. 5. CEBUS CAPUCINUS ; FEMALE, 

 SEVEN YEARS OLD 



She was an old inhabitant of the Park, always hungrj', 

 always working to get food, afraid of persons, but her 

 record in learning was equal to that of Jack's. 



must be moved to the right through an arc 

 of about 30 degrees. 



The apparatus for the string experiment 

 was arranged as follows : Strings were 

 dropped from the top of the cage down- 

 ward along each of the corner posts to 

 within eight inches of the floor. In a sim- 

 ilar manner three other strings were 

 dropped from the top along the back of 

 the cage. In the back of the cage near the 

 bottom was a circular opening two inches 

 in diameter. On the outside of the cage 

 was a small chute, the bottom of which 

 was on a level with the circular opening 

 in the cage. In this chute was a trap-door 

 to which could be attached any one of 

 the strings which hung on the inside of the 

 cage. It was originally intended that the 

 experiniient could be varied by attaching 

 the several strings in succession. In the 

 actual carrying out of the experiments, 

 there was time for using only one string. 

 Food was supplied to the trap-door by the 

 feeder used in the chute experiment B.. 

 When the monkey pulled the string, the 

 food dropped to the bottom of the chute 

 and rolled into the cage through the cir- 

 cular opening. 



The seven problem devices which have 

 just been described were perfected only 

 after extended preliminary experimenta- 

 tion with the two monkeys in the old cage. 

 Provisional devices were set up, and the 

 monkeys were given opportunity to manip- 



ulate them. As a result of observations on 

 their behavior, the devices were improved 

 and adjusted in the new cage. When all 

 was complete, the new cage and the tvvo 

 animals, each of which had been trained 

 to get food in one or another of the ex- 

 periments, were shipped to New York. 

 Thanks to the generous interest of Dr. 

 Hornaday, director of the park, it was 

 possible to continue the investigation un- 

 der exceedingly favorable circumstances. 



From the large number of monkeys in 

 the Primates' House, eight were selected 

 for the investigation. Five of these were 

 Cebus monkeys similar to Jack and Jill, 

 and three were Macacus. The latter is 

 an Old-World genus embracing about 

 twenty-five species. They are larger than 

 the Cebus, have short thumbs and non- 

 prehensile tails. They are strong, very 

 vigorous, and less inclined to be tamed. 



The method of experimentation was as 

 follows: First, a monkey w^as given an op- 

 portunity to solve a problem by itself. For 

 this purpose it was put into the experiment 

 cage, fifteen minutes at a time, on five 

 successive days. In case it did not learn 

 to get food alone, it was given an oppor- 

 tunity to see another monkey manipulate 

 the device. After this, it was given an- 

 other opportunity to do the trick alone. 

 The imitator was given ten minutes after 



NO. 5 GETTING FOOD IN THE PLUG 

 EXPERIMENT 



She has just pulled the plug, which hangs down 

 the post in the new cage. 



