46 FREDERICK S. BREED 



impulse had begun to gather force. There is a nice middle 

 ground here that gave the best results. There were great indi- 

 vidual differences in the animals. Some stood about for a while 

 before the impulse to escape seized them, others rushed imme- 

 diately toward the screen door. The experimenter stood back 

 of the entrance box between the two windows of the room, and, 

 after releasing the chick from A, remained as quiet and motion- 

 less as possible" until the animal found its way out of the appa- 

 ratus. I had practically no success with the device Yerkes 

 used with the dancing mouse, the card by which he gradually 

 forced the animals toward the electric box. Chicks that won't 

 work without force won't work with it, is a rule that can be 

 generally relied upon. After the animal had escaped to the cage, 

 the experimenter secured it again, brought it back to the. en- 

 trance box, and the procedure as described above was repeated. 



At the beginning of a set of experiments the animal was 

 familiarized with the apparatus, as well as tested for its prefer- 

 ence of the stimuli presented in the card-holders, by a number 

 of " preference trials," usually one series, which consisted of ten 

 trials. Sometimes a second series was given. These series are 

 denoted in the tables by A and B, respectively. During the 

 preference trials the exits at H were both left open, the two 

 sets of cards were alternated right and left after each trial, and 

 no electric shock was used. To show the readiness with which 

 the chicks reacted in the preference trials as well as to suggest 

 the availability of the animals for certain kinds of labyrinth 

 training, I present below as typical the average time in seconds 

 for each preference trial, from one to ten, of chicks nos. 32, 33, 

 38, and 39, Group I, at the beginning of their black-blue work: 

 69.2, 24.1, 18. 1, 3.8, 3.4, 2.6, 2.1, 1.9, 2.2, 1.9. Chicks thus 

 tested for an experiment were continued in that experiment, un- 

 less they were found to have a preference for the stimulus, to 

 which it was desired they should form the habit of positive 

 reaction. A chick that revealed a preference for this stimulus 

 prior to training was rejected. 



After the preference trials had proved a chick satisfactory, it 

 was subjected to the regular conditions of training. The "wrong" 

 side of the apparatus was closed at the exit and the animal was 

 given a shock if it entered the electric chamber on that side. 

 This was done by quietly pressing the key previously referred 



