DISCRIMINATIVE ABILITY OF THE TURTLE 23 



in their mode of behavior under experimental conditions. A few 

 of these have already been noted. Some turtles failed partially 

 or completely to solve problems which others acquired with 

 little seeming difficulty. Such cases of individual failure to 

 learn appear to have been dependent upon two factors: indi- 

 vidual lack of mental ability or lack of tractability. It is com- 

 mon knowledge that an animal with a surly disposition cannot 

 be taught tricks. Any turtle that refuses food, retires within 

 its shell upon slight provocation and shows a pronounced dis- 

 position to sulk is useless as an experimental animal. Almost 

 any wild adult turtle will act in this manner when first handled 

 but with proper care should gradually become more tractable. 

 However, some of my turtles never became accustomed to 

 captivity and these were finally discarded. Others would respond 

 most satisfactorily for a time and then gradually or suddenly 

 lose interest or become sulky. Such turtles might or might not 

 change in disposition and be useful for later experiments. With- 

 out doubt turtles also differ greatly in mental ability. Some 

 appeared willing enough to learn, were cheerful and active, yet 

 did not succeed in learning as rapidly as others. 



The persistence of individual characteristic movements. In 

 addition to individual mental characteristics of a general nature 

 some of the turtles showed certain definite peculiarities which 

 were expressed by distinctive movements and reactions. No. 

 lo almost invariably stopped upon entering the food box and 

 insisted on biting the cork behind which the meat was placed. 

 This was the one persistent " stupid " action of this turtle 

 throughout its experimental history. Occasionally it would 

 simply stop before the cork and crane its neck around the blind 

 until the food came into view. Then it would either advance 

 and proceed to take the food or would bite the cork again before 

 doing so. It seemed continually to labor under the delusion 

 that the reward might most easily be obtained by tearing away 

 the intervening obstruction; at least such an explanation pre- 

 sents itself as a plausible human interpretation of this habit. 

 No other turtle acted in the same way. 



Directness or indirectness of approach and entrance into the 

 boxes varied in different cases. As has before been intimated, 

 physical quickness was not necessarily associated with mental 

 alertness or deliberate movements with dullness. Neither was 

 the converse true. The most active turtles were just as likely 

 to choose unwisely as the deliberate ones, and vice versa. But 

 this quality of agility of movement or its reverse usually mani- 



