200 MIND IN EVOLUTION CHAP. 



Billy's method of solving a problem is quite distinctive. His 

 principle is never to stay still. He slips all over and round the 

 box like a drop of quicksilver, sniffing and pawing and gnawing 

 with a vast amount of superfluous energy, and greatly delaying 

 himself thereby. 1 He was but a young thing, however, and 

 rather like a kitten in his ways, mewing with excitement while 

 the box was being adjusted. He learnt the bolt after seeing it 

 done twelve times, but how far by seeing it done, I am unable to 

 judge. Billy was taught by his keeper. When I visited him 

 he showed a distinct inclination to increase his meal at the ex- 

 pense of my legs. At the same time, by an odd coincidence, I 

 found that a better view of the proceedings could be obtained 

 from outside the bars. So Billy's education was left to Mr. Cray- 

 thorn, who has taken great interest in his development, and has 

 frequently assisted me by taking notes in my absence. 



The bolt was pulled out twelve times, the otter being left each 

 time to open the box by the lever. The otter then pulled out 

 the bolt three times running, with some delay. The next day 

 he had to be shown the first time, but after that he always suc- 

 ceeded, though by no means always with equal neatness. He would 

 often bite at the bolt a good deal, and sometimes on the wrong side 

 of the staple, but he would soon correct himself. Sometimes, 

 too, he would pull the bolt half out, leave it hanging, and then 

 try the lever. After a struggle with it, he would go back, and 

 finish with the bolt. 2 At times he would take a run round after 

 pulling out the bolt, or gnaw irrelevantly at the lever or the 

 extracted bolt itself. At other times, when the door was swollen 

 with damp, and would not open easily, his persistence in pushing 

 at the lever was really remarkable. On the whole Billy's 

 behaviour may be understood best by regarding the proper plan of 

 action as a kind of centre from which he kept deviating always 

 to return again. 



(5). Push-back bolt. 



A similar box was fastened by a bolt furnished with a 

 knob. It could not be pulled out, but had to be pushed 

 back. This turned out to be much harder for the 



1 Mr. Small's description of his rats ("An Experimental Study of the 

 Mental Processes of the Rat," W. S. Small, American Journal of 

 Psychology, Jan. 1900) often reminds me of Billy. Superfluous movements 

 of the kind make it difficult to measure intelligence, especially when they 

 intervene between two actions. Mr. Small rightly remarks (p. 142) that 

 extra hunger sometimes increases rather than diminishes the useless 

 movements, which, of course, come nearer to the normal methods by 

 which hunger is satisfied. 



2 He is now, I am told, very perfect with the bolt, but he has been used 

 to it for between two and three months. 



