38 K. S. LASHLEY AND L. E. WILEY 



auditory area are relatively less effective, although they also 

 produce a significant deterioration of the function. 8 



We have computed the correlation between extent of lesion 

 and error scores for each of the above four groups with 

 lesions largely restricted to single architectural fields. The 

 constants obtained were the following : Motor, p = 0.66 ± 

 0.12 ; somesthetic, p = 0.58 ± 0.12 ; auditory, p = 0.07 ± 0.19 ; 

 visual, p = 0.36 ± 0.17. 



This selection of cases greatly reduces the range of varia- 

 tion and consequently affects the magnitude of the correla- 

 tions. The mass relation seems to hold within the motor, 

 somesthetic, and visual areas. As in the comparison of aver- 

 ages, the auditory area does not conform to the trend of the 

 others. 



For the question of the exact equivalence of the various 

 parts of the cortex for maze learning our data must be re- 

 garded as inconclusive. Clearly, lesions in any part of the 

 cortex produce marked retardation. For the motor, somes- 

 thetic, and visual areas this retardation is approximately 

 equal, at least more nearly so than the demonstrated retarda- 

 tions from peripheral sensory defect. The lesser effects of 



8 We have attempted to use another method for comparison qf lesions in the 

 different fields. The percentage of the cortex included within the lesion in each 

 field was listed for each animal. On the assumption that the injury within 

 each field contributes to the deterioration of the animal according to some 

 determinant (D) which is constant for that field, the total error score may be 

 expressed as the sum of the products of the percentage destruction within each 

 field by the determinant for that field. This gives, for example, for animals 

 nos. 16 and 17 in maze I the equations — 



13.6 Df/n + 7.1 Dj = 57 

 10.9 Df/n + 7.8 Dj = 33. 



We thus obtained 127 equations for maze V. These were solved by the method 

 of Doolittle to give an average value for D for each of the four chief fields. 

 The results were D ff / n =7; D p = 8; Dj = 18; D w = 27. Using these values, 

 the expected errors were computed for each animal and plotted against the 

 experimental errors. This comparison gave theoretical values consistently too 

 high for the lesser lesions and too low for the greater, showing that what had 

 seemed a promising method is inapplicable to our data, because of the non- 

 linear relation between extent of lesion and performance. We are indebted to 

 Prof. L. L. Thurstone for the test of this method. 



