362 K. S. LASHLEY 



reduced the tendency to emotional disturbance. This is shown 

 by the following averages times for successive trials in group B 

 (ten trials per day) on the second day of practice. 



Trial 123456789 10 



Seconds 38 22 20 17 22 8 5 5 5 13 



The time of successive trials falls steadily throughout the practice 

 period. The rats in group D, on the contrary, showed a much 

 more marked tendency to flight reactions in the food compart- 

 ment than did those in the other groups. They would frequently 

 advance to the food dish, then turn, run quickly into the cul de 

 sac, and gnaw for some time at the wire cover of the food dish 

 there. Apparently owing to the presence of the screened food 

 in the cul de sac, as offering the stimulus of food without associ- 

 ated handling, these animals frequently persisted in their avoid- 

 ance of the food compartment and in their efforts to get at the 

 food in the cul de sac throughout the practice period. This is 

 shown by the following average times for successive trials in the 

 second day's practice. 



Trial 123456789 10 



Seconds 14 34 33 11 27 22 35 20 36 154 



The prolonged time toward the end of the day's practice is char- 

 acteristic of the early days of practice of this group. 



The summation of the exploratory impulse and of emotional 

 disturbance thus seems to be characteristic of the groups showing 

 marked retardation of learning in concentrated practice. Fur- 

 ther, the extent to which such summation occurred varied with 

 the different conditions of training and resulted in corresponding 

 variations in the amount of retardation. It thus seems clear 

 that a great part of the retardation resulting from concentrated 

 practice is due to this summation of instinctive reactions. Even 

 in group B, which showed the least loss of efficiency in ten trials 

 practice per day, there was some indication of a tendency for the 

 animals to avoid the place where they had been caught and it seems 

 probable that a large part of the retardation shown by this group 

 is due also to the interfering effect of this emotional factor. The 



