Modification by Experience 267 



experimenter was able wholly to overcome this reaction, 

 especially with one gifted individual. After two months 

 of training, "all that was necessary to bring the specimen 

 up when it had disappeared from sight was to slightly jar 

 the dish or the table on which the dish was located, and 

 the insect would quickly come up to the upper side of the 

 rock and make for its feeding place.". Here again, the 

 conscious aspect of the learning is probably a reversal of 

 the emotional tone of the situation : originally unpleasant, 

 it has become pleasant. Where the method of reward is 

 used to train animals in discriminating stimuli, the influ- 

 ence of the reward is combined with that of the tendency 

 to drop off useless movements. Cole's raccoons learned 

 not only to climb up when the food signal was given, but 

 to stay down when the no-food signal appeared. The 

 rabbits studied by Miss Abbott and the writer (756) were 

 taught to push at a door carrying a piece of red paper, and 

 to refrain from pushing at a door carrying gray paper. 

 The original stimulus for the pushing was the odor of 

 food which was in the compartments behind both doors. 

 The "gray" door was always bolted on the inside, so that 

 pushing against it was in vain; the "red" door opened 

 freely so that the rabbits could get at the food. The actual 

 securing of the food acted, along with the smell of it, to 

 suppress all useless hesitations on the part of the animals 

 and to make them more inclined to push the doors at once ; 

 the gray stimulus acquired a tendency to lose its motor 

 effect because the movements to which it gave rise were 

 useless. 



So-called "puzzle-box" experiments also depend for 

 their training effect upon the combined tendencies to the 

 survival, through their prepotency, of movements result- 

 ing in the satisfaction of an instinct, and to the dropping 



