Modification by Experience 269 



was simplified ; thus the birds learned not to attack other 

 parts of the box, to use the bill instead of the claws, and 

 to stand on the floor beside the box instead of hopping upon 

 it (611). In Rouse's test of the pigeon by the puzzle-box 

 method, it showed less aptitude than that displayed by 

 the English sparrow (647). 



Small (684) tested his white rats with two boxes contain- 

 ing food. One could be entered by digging away the saw- 

 dust which was banked around the lower end of the box, 

 if the digging was done in a particular place ; the other, 

 by tearing off strips of paper which held shut a spring door. 

 The result of the earlier series of experiments with the first- 

 mentioned box was that after an hour and a half on the 

 first day one rat happened to dig in the right place and 

 entered. The second day this rat took only eight min- 

 utes, and the thirteenth day only thirty seconds, to enter. 

 With the second box there was always a tendency to be- 

 gin by digging, and even in the thirteenth experiment, 

 where the rat got in by biting off the papers in fifteen seconds, 

 she began by two strokes of digging. In a later test with 

 this box the rat chanced to be extremely hungry, and dug 

 violently for several seconds, displaying a blunting of 

 the discriminative powers by hunger, analogous to that 

 which we have found in very low animals. The rats 

 were later trained to discriminate between the two boxes, 

 being sometimes presented with one and sometimes with 

 the other. 



In Thorndike's work on cats and dogs, the investigator 

 placed the animals themselves in the boxes, and food on 

 the outside, so that the problem was not how to get in but 

 how to get out. The getting out could be accomplished 

 in various ways, such as pulling a wire loop, clawing a 

 button around, pulling a string at the top of the box, poking 



