THE HUMAN SIDE OF APES 



exhibit ideational behavior; they act with insight. It remains 

 for further patient, critical research to analyze this behavior 

 more adequately and to compare it with our own action 

 under identical conditions." 



One of the striking characteristics of apes and monkeys 

 is the time and effort they spend in mere play. A cow, 

 when her hunger is satisfied, is content to rest indefinitely. 

 But not so the ape. He must be actively exploring, romping 

 with his fellows, climbing, swinging, or pulling things to 

 pieces. In this way he learns much about the properties 

 of things in his environment. His ability to use his hands 

 in manipulating objects gives him a great advantage over 

 the lower mammals in adding to his store of knowledge. 

 Along with his better structural equipment he is endowed 

 with a strong natural curiosity, which is not confined merely 

 to things that immediately affect his welfare but manifests 

 itself in a sort of pure intellectual interest in objects per se. 

 As the ape grows older his playfulness and his spontaneous 

 curiosity gradually diminish, and he becomes more stolid, 

 inactive, and incurious, like so many uneducated human 

 beings. 



Chimpanzees express joy and satisfaction by smiles and 

 laughter, especially in play and when they are tickled or 

 given a favorite food. They often show sympathy and 

 affection in very human ways. Madam Abreu, in describing 

 her efforts to catch one of her chimpanzees that had escaped 

 and taken refuge in a mango tree, writes: "I went to the 

 tree, and speaking to him pretended that I was injured in 

 the arm and suffering. Immediately, on seeing that I was 

 in trouble, he jumped from the tree and coming to me held 

 my arm and kissed it strongly. And so we were able to 

 catch him." 



''Impressive indeed," says Dr. Yerkes, "is the thoughtful- 



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