110 ROBERT M. YERKES 



of a stick as an object to rub over the teeth, for with this he 

 was able to make a noise that would have satisfied even a 

 small boy. 



Further light is shed on the force of the tendency to imitate 

 man by the saw test. After Skirrl had been given an oppor- 

 tunity to show what he could do with the tool spontaneously, 

 I demonstrated to him the approved human way of sawing. 

 Often he would watch my performance intently as though fas- 

 cinated by the sound and motion, but when given the tool he 

 invariably followed his own methods. Although I repeated this 

 test of imitation several times on three different days, the re- 

 sults were wholly negative. 



Other Activities 



One day as Skirrl was being returned to his own cage by 

 way of the larger cage, he picked up an unfastened padlock 

 and carried it into the cage with him. For more than an hour 

 he amused himself almost without interruption by playing with 

 this lock. The things which he did with it during that time 

 would require pages to describe. His interest in it was very 

 similar to that which he had exhibited in hammer and nails, 

 saw, and indeed any objects which he could play with. The 

 lock was pounded in various ways, bitten, poked with nails, 

 hooked into the wires of the cage, used to pull on, pounded with 

 a stick, used to hammer on the floor of the cage with, and in 

 fine, manipulated in quite as great a variety of ways as a human 

 being could have discovered. Finally it was hooked to the 

 side of the cage and snapped shut, and as Skirrl was unable 

 to dislodge it from this position, he shortly gave up playing 

 with it. 



At the end of the large cage and just outside the wire netting 

 was a faucet to which a hose was usually attached. The valve 

 could be opened by turning a wheel-shaped hand piece. Both 

 Skirrl and Julius learned to turn this wheel in order to get 

 water to play with, but usually the former's strength was not 

 sufficient to turn on the water. The latter could do it readily. 

 The indications are that both animals profited by seeing human 

 beings turn on the water. This unquestionably attracted their 

 attention to the faucet, and probably by playing with it they 

 accidentally happened upon the proper movement. At any 



