STUDIES OF CEREBRAL FUNCTION. IX 39 



injuries in the auditory area are probably significant, but 

 even with so extensive a series of cases as are included in our 

 study, the statistical reliability of our data is low. 



INFLUENCE OF THE COMPLEXITY OF THE PROBLEM 



To test the question whether an increasing number of culs 

 de sac in the maze offers a progressively greater difficulty for 

 animals with cerebral lesions than for normals, we have made 

 a comparative analysis of the learning records of normal and 

 operated animals trained on mazes I, II, III, and IV. The 

 individual records of the normal animals have been presented 

 in tables 4 to 11. 



Equation of groups 



Since, as was pointed out in our discussion of methods, it 

 is necessary to use a separate group of animals with each of 

 the mazes in the tests of complexity, some method of equat- 

 ing the groups is desirable. Members of the groups were 

 taken at random from the stock colony and were presumably 

 a random sample of the colony. An attempt was made to 

 obtain four identical series of animals with destructions of 

 from 5 to 60 per cent of the cortex, by the method described 

 on page 15. Comparative data on the extent of lesion have 

 been presented in table 2. Group I shows the smallest aver- 

 age percentage destruction, but also the greatest range. The 

 averages for the other three groups are practically identical, 

 with a somewhat smaller range in group IV than in the others. 

 In the loci of the lesions the groups seem sufficiently alike to 

 permit of direct comparison. 



As a test of the equality of the groups, all were trained on 

 maze V after completion of training on the comparison mazes. 

 The average scores for the eight groups in maze V are pre- 

 sented in table 19. Measurement of the equality of the groups 

 by the use of a second maze is complicated by the possibility 

 of differential transfer from the different mazes used in the 

 initial training. The table gives some indication that such 

 a transfer has taken place. Converting all the constants of 



