42 L. W. SACKETT 



mentation, one fundamental difference should be noted. The 

 attention of the monkey is easily distracted; the cat seldom 

 takes any problem seriously; the dog is always ready to do 

 his master's bidding rather than to solve a problem of his own; 

 the birds are afraid to abandon themselves to the task; rats, 

 mice, and guinea pigs are each handicapped in their own way; 

 and so it might be continued. With the porcupine there are 

 few, if any, of these disturbing factors. One can depend upon 

 the porcupine's best effort most of the time. More than that, 

 he goes about getting his dinner with an abandon which would 

 suggest that he had not an enemy in the world and had never 

 depended on anyone but himself for his survival. 



Conclusions from Puzzle-box Experiments. — 



1. Porcupines do not show very great individual difference 

 in methods of attack on any new lock or device, but each evolves 

 a characteristic way of operating it after a few trials. 



2. Any fortuitous movement which proves successful usually 

 persists and is gradually reduced to its simplest form. 



3. When a habit is once formed by the porcupine it tends 

 to persist unless an accidental variation happens to be in the 

 direction of simplification. 



4. In so far as tests have been made the porcupines have 

 shown an ability to form associations between sense stimuli 

 and motor response which is quite comparable with that of 

 other animals. 



5. Retention of such a problem as the puzzle-box shows that 

 associations on the mental side, or at least in the more general 

 adaptations, persist more perfectly than muscular co-ordina- 

 tions. Or, more concretely, on memory tests the animal directs 

 his efforts to the proper devices in the proper order far more 

 successfully than he co-ordinates his movements in operating 

 those devices. 



Form Study. — The apparatus to test the porcupine's ability 

 to discriminate form was designed to appeal directly to the 

 denning proclivities of the animals. Eight blocks of planed 

 lumber nine inches square and one inch thick, approximately 

 symmetrical and similar, were used. Out of the middle of the 

 blocks the desired forms were cut with a fine saw. The form 

 used, however, was the opening through the block rather than 



