42 



K. S. LASHLEY AND L. E. WILEY 



ing from the simplest to the most complex. The scores by 

 other criteria are less consistent, but show in general the same 

 trend. The averages of all scores, expressed as percentages 

 of the scores on maze I are given at the right. 



The ratios of practice required for learning by all criteria 

 for mazes II, III, and IV on maze I are given in table 23. 

 The objective complexities of the mazes, expressed in numbers 

 of culs de sac are in the proportions of 1:2:3:4. The rela- 

 tive difficulty for normal animals, in terms of the most con- 

 sistent criterion, error scores, is as 1:3:4: 5.5. The ratio of 

 difficulty for the operated cases (1 : 3.7 : 4.2 : 5.6) is not signifi- 

 cantly different from that of the normal animals. The indica- 



TABLE 23 

 Comparison of scores in learning tests for normal and operated animals in the 

 four comparison mazes, expressed as ratios on scores in maze I. N = normal 

 group, Op. = operated group, 0p.<40% = cases with lesions of less than 40 

 per cent, included as a control of the effects of exclusion of cases which failed 

 to get through the maze on the first trial 



tions from time and trials are essentially the same. There 

 is no evidence that the longer mazes are disproportionately 

 more difficult for the operated animals than for normals. 



The indication in table 19 that operated groups III and IV 

 are superior to the others, even allowing for differential trans- 

 fer, suggests that the selection of cases brought about by 

 failure of some cases to get through a single trial may have 

 favored those groups. We have therefore computed the aver- 

 age errors for the operated animals exclusive of cases having 

 more than 40 per cent destruction, thus eliminating the most 

 badly deteriorated cases from groups I and II. The ratios 

 of these averages on the scores for maze I for the four groups 

 were the following : 



