268 



The Animal Mind 



off of useless movements. The method has been tried 

 with birds, rats, squirrels, cats, dogs, raccoons, porcupines, 

 and monkeys. Thorndike, its originator, made some 

 experiments of this type on chicks confined in pens 

 from which they could be released by pecking at a 

 string or some such object (704). Porter tested English 

 sparrows with boxes containing food, which could be en- 



FIG. 12. Puzzle box used in Porter's work on birds; AB, one method of attach- 

 ing string to latch ; C, a second method. In the first, the loop at B had to be 

 pulled ; in the second, the string had to be pushed in. 



tered by pulling a string fastened to a latch, or by pushing 

 the string into the wire netting with which one side of the 

 box was covered (Fig. 16). The sparrows learned very 

 quickly; one of them by the tenth test had left out all 

 unnecessary movements (610). In later experiments a 

 cowbird and a pigeon also learned to open a similar box. 

 Before beginning the test the birds were accustomed to 

 being fed in the box with the door open. Their first suc- 

 cess in opening the door lay in accidentally clawing or 

 pecking at the proper point, and in later trials the action 



