

CEREBRAL FUNCTION IN LEARNING 75 



the door to move inward against the second latch. In this po- 

 sition of the door the first latch could not catch again. Pres- 

 sure on the second platform (b) would now release the second 

 latch and allow the door to open. 



As a result of this arrangement the door could be opened only 

 by depressing the platforms in succession, beginning with the one 

 nearest the door (a) . Pressure on the first platform (a) caused 

 only a faint click, pressure on the second platform (b) caused the 

 door to open, but only after the first platform had been depressed. 



Food was placed in the box and this was enclosed in a re- 

 straining cage which allowed a space of about 30 cm. around the 

 sides and top of the box. The animals were admitted through 

 a small door in the restraining cage, opposite the door of the 

 problem box. A stop-watch was started as soon as the animals 

 entered the restraining cage. The times required to trip the first 

 platform, to trip the second platform, and to enter the box were 

 recorded. If the animal failed to open the box in an hour, except 

 on the first trial, he was taken out and not fed. On the following 

 day the latches were set as he had left them and the trial was ; 

 continued. On the first trial inactive rats were allowed to re- 

 main in the restraining cage over night if necessary. Since none 

 of the animals was fed in the problem box until after the first 

 trial, the time of the first trial is significant only as a measure of 

 general exploratory activity and it is not included in the com- 

 parison of times required for learning. 



As it was not possible to breed rats in the laboratory in time 

 for the work, the ancestry and exact age of the animals used in the 

 experiments is unknown. All were young when purchased, how- 

 ever, and their age could be estimated roughly. All were be- 

 tween 120 and 180 days old at the time of operation, with the 

 exception of numbers 1 and 17 which were older. Training was 

 begun at intervals of from 13 to 43 days after the operation. 



As a measure of learning the following arbitrary criterion was 

 employed. The animal must go directly from the door of the 

 restraining cage to plane a and push down the platform; he must 

 then go by some constant path to plane b and after pushing it 

 down must go directly to the open door and enter the problem 



