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THE MAINTENANCE OF THE INDIVIDUAL 



Intelligence of Apes 



Because of their relationship to man, the higher apes have been the 

 source of much fruitful experimentation of late years. Kohler ^ has 

 demonstrated that the chimpanzee shows evidence of emotionalized 

 response as well as a comparatively high degree of intelligence. 

 A chimpanzee shows emotion not only by actions, but also in facial 



Yale LaboTotOTies of Primate Biology 



Chimpanzees are the most emotional as well as intelligent of the apes. 



expression. The ape jumps up and down to show excitement, knocks 

 its head on the floor of the cage when unable to solve a difficult 

 problem, or looks vacuously into space and smiles when lost in con- 

 templation of some object that interests it. Yerkes ^ shows that 

 chimpanzees have wide differences in emotional or intelligent conduct. 

 One may be gloomy, another happy, one lethargic, another active, 

 one dull mentally, and another bright. They may be as tempera- 

 mental as some human beings or just as stoical. They also show 

 great differences in mentality and like man have their "off" days. 



Kohler describes one series of experiments which show that apes 

 have intelligence to solve problems difficult enough to test the inge- 

 nuity of a young human child. The ape Koko was the subject. 

 In his cage was placed a box and from the top of the cage a banana 

 was suspended well out of reach. The ape first tried jumping for the 



1 Kohler, W., The Mentality of Apes, Kegan, London, 1924. 



2 Yerkes, R. M., and Learned, B. W. : Chimpanzee Intelligence and Its Vocal Expression. 

 liams and Wilkins Co. 



Wil- 



