HABIT FORMATIOX IX THE DOG 49 



seemed evident that they were localizing the sound, at any 

 rate. It seemed well, therefore, to ascertain what effect inter- 

 change of the buzzers would have on the dogs' reactions. In 

 this control-experiment, designated as problem 9, buzzer i was 

 placed over door X' and buzzer 2 over door X. The sound of 

 buzzer i was to be associated with food in compartment F, and 

 that of buzzer 2, with food in compartment F', as in problem 8, 

 just learned. The difference in conditions was that food was 

 now to be obtained in the compartment opposite, instead of at 

 the sounding buzzer. 



Each dog was continued for five days on problem 8, which 

 had been learned some three weeks earlier. The animals had 

 done no work meanwhile, but the feeding hour had remained 

 the same. Each animal had given at least three successive days 

 of perfect records immediately preceding the beginning of prob- 

 lem 9. The first day's record of each animal on problem 9 

 immediately follows. The letters R and L signify right and 

 left compartments, respectively. 



This control test shows quite clearly that the location of the 

 source of sound with respect to food is the characteristic of 

 the stimulus which had been determining the animal's reac- 

 tions. Each dog had been simply going to the compartment 



* The problem was "learned" on the ninth day. The record of the tenth day 

 is of a control-experiment, described on page 53, made to show the disturbing 

 effect of variable position of the animal when the stimulus is given. 



t The animal's work on this day was disturbed by the falling of a heavy door 

 near food-compartment F while the series was in progress. For the remainder 

 of the day she refused to choose F under any conditions. She was left to run freely 

 in the cage all night in order to overcome the disturbance. 



