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



E s== (38.39) e (0 - 0698)L , in which E is the error score, L the per- 

 centage lesion, and e the Naperian base. 



"Where there is an adequate number of cases, the data con- 

 form quite closely to the regular curve and suggest that the 

 retardation from cortical destruction follows some definite 

 law by which learning ability for the maze rapidly approaches 

 zero with larger lesions. For the lower amounts of destruc- 

 tion, where the number of cases is large enough to give relia- 

 bility to the averages, the experimental data conform quite 

 closely to the derived curve and there is no indication of any 

 critical amount of destruction resulting in a sharp rise in 

 the error scores. 



From this extensive series of cases and from indications 

 given by less adequate earlier series, it seems certain that 

 with increasing size of lesion, learning ability for the maze 

 decreases at a steadily accelerating rate. The exact form of 

 the curve has no significance at present. 



The influence of subcortical lesions upon the mass relationship 



It is impossible to obtain an extensive series of cases with 

 large cerebral injuries without some lesions in the thalamus 

 and archipallium. Lashley ('29) attempted to estimate the 

 influence of such subcortical lesions in two ways: first, for 

 control of thalamic lesions, by computing correlations sepa- 

 rately for all cases with and for all cases without thalamic 

 lesions, as well as for these two classes combined; secondly, 

 by assigning an arbitrary value to each type of subcortical 

 lesion and correcting the ranking for correlation obtained 

 from cortical lesions by these arbitrary values. These 

 analyses gave the following results. Correlations between 

 errors and cortical destruction: 



For all cases, p = 0.86 



For cases without thalamic lesion, p = 0.83 

 For cases with thalamic lesion, p = 0.86 



With arbitrary correction for all types of subcortical lesions 

 the correlations were the following between total destruction 

 and the learning constants : 



