CEREBRAL FUNCTION IN LEARNING 79 



With this area as a basis, I have reanalyzed the data on 

 postoperative retention of the habit based on brightness dis- 

 crimination to determine whether or not the frequent inva- 

 sion of the area by large lesions was responsible for the 

 correlations found. The method of analysis was the follow- 

 ing : The cases (numbered from 50 to 98 ; Lashley, '26, table 

 3) were divided into three groups: a) in which the areas 

 critical for pattern vision were destroyed completely in both 

 hemispheres; b) in which the critical areas were invaded, 

 but not completely destroyed, and, c) in which there was no 

 invasion of the critical areas. 



a. Cases with complete destruction in both hemispheres of 

 the areas essential to pattern vision. This group includes 

 nos. 56, 60, 65, 66, 72, 76, 77, 78, 79, 80, 81, 83, 86, 87, 88, 89, 

 90, 91, 92, 93, 94, 95, 96, 97, and 98— a total of twenty-five 

 cases. The average extent of lesion in these cases was 20.2 

 per cent of the neocortex. In postoperative retention tests 

 the average records were : trials == 62.0, errors = 19.7. 

 Eank order correlations have been computed^ for extent of 

 destruction with trials and with errors in relearning for these 

 cases. The constants obtained were : 



p trials = 0.727 ± 0.075 

 p errors = 0.718 ± 0.072 



This grouping of cases excludes most of the animals with 

 small lesions, thus markedly reducing the range of variation 

 included in the computation of correlation. Nevertheless, the 

 correlations found are practically identical with those ob- 

 tained when the entire group of forty-eight cases is included. 



b. Cases with partial destruction of the areas essential for 

 pattern vision on one or both sides. This group includes 

 nos. 51, 52, 54, 57, 61, 63, 64, 67, 68, 69, 70, 71, 82, 84, and 85— 

 a total of fifteen cases. The average extent of lesion in these 

 cases was 12.2 per cent of the neocortex. In postoperative 

 retention tests the average records were : trials = 28.9, 

 errors = 7.5. Correlations between extent of lesion with 

 trials and with errors were the following : 



^ By the formula p = 1 — — ^s:^ 



