STUDIES OF CEREBEAL FUNCTION IN LEARNING. VII 9 



same time to eliminate seasonal variations and progressive 

 changes in the experimenter's technique. 



Since I knew the extent of the lesions roughly from the 

 character of the operations, there is a chance that precon- 

 ceived theories might modify the training of particular ani- 

 mals, even when the point where such a personal equation 

 might enter could not be detected. The only control which I 

 can offer for this is the observation that in five cases where 

 I greatly misjudged the extent of the operation the behavior 

 of the animals conformed to the actual extent of the lesion as 

 determined at necropsy and not to my earlier expectations. 



In the series of cases reported some are included which 

 were trained in earlier experiments (Lashley, '20, '21 a, '22). 

 These are marked with an asterisk in the tables. The initial 

 training of cases 50, 53, 54, 55, 56, 65, 66, 87, 88, 94, 109, 110, 

 111, and 112 was done by Miss Dorothy Hunter and Mr. L. E. 

 Wiley. I have computed constants both including and exclud- 

 ing the cases from these sources. Their exclusion does not 

 significantly change the results, except to increase the prob- 

 able errors. 



The possibility of reaction to other than visual cues must 

 be considered. To determine the effective stimulus the fol- 

 lowing procedures and criteria of visual reaction were used 

 after completion of training or retention tests : 



1. Trials with both lamps extinguished. Failure to advance 

 beyond the discrimination compartment indicated that the 

 previous reactions had been to visual cues. 



2. Trials with both lamps lighted. Initial confusion with 

 rapid development of a position habit. 



3. Control of reaction to temperature. With one lamp 

 lighted the animal was started into the discrimination com- 

 partment. When he entered the illuminated alley, the lights 

 were reversed, leaving the lamp bulb heated but dark in the 

 alley chosen, lighted but not yet hot in the other. Turning 

 back when the light was extinguished and prompt entry into 

 the newly lighted alley gave evidence that the reaction was 

 not to temperature. 



