RETENTION OF HABITS BY THE RAT 



9 



Experiment 3. HI 9 . Ninety-two days old. Learning was com- 

 pleted in 21 trials with 2 trials per day. No overtraining. 



Operation through two trephine holes, with little hemorrhage. 

 Retention was tested twenty-two hours after the operation. The 

 rat oriented in the starting compartment, ran promptly and without 

 exploratory smelling, and never explored the maze in a way compar- 

 able to that of normal animals in their first trials. She entered the 

 cul de sac on the first, fifth, eleventh, and thirteenth trials but turned 

 back promptly before reaching the end of it. On the errorless trials 

 she followed the path marked in figure 1. The records of learning and 

 retention were the following. 



Animals tested after overtraining 



Experiment 4- Glcf . Seventy-three days old. Learning was com- 

 pleted in 21 trials with 10 trials per day. Training was continued for 

 170 trials. 



Destruction of frontal lobes through large transverse opening, fol- 

 lowed by little hemorrhage. Retention was tested twenty hours after 

 the operation. The rat oriented correctly in the starting compart- 

 ment and advanced promptly when the door was opened. On the 

 first trial he turned into the cul de sac and stopped with his head in 

 the first corner, then backed out and went directly to the food. He 

 made a second error on the fourteenth trial. The other trials were 

 correct but were delayed by a peculiar reaction. When he reached the 



