STUDIES OF CEREBRAL FUNCTION. IX 13 



learning, and constants computed from the error records are 

 emphasized in our treatment of the data. Constants com- 

 puted from time and trials are also included as contributory, 

 but less reliable evidence. 



The early trials, especially the first, are scarcely compar- 

 able with later trials in the maze after the preliminary explor- 

 atory period is passed. Lashley ( '17) has shown that in early 

 trials there is a strong tendency to explore all parts of the 

 maze. Various means have been suggested to correct the 

 learning records for exploratory errors in early trials (Thur- 

 stone, '33). We have not yet sufficient data for evaluation 

 of the methods or to judge which of the errors are signifi- 

 cant for learning. In the first trial the animal has had no 

 opportunity to associate the maze with food and hence the 

 motivation in this trial differs from that in all later trials. 

 For this reason we have omitted the records of the first trial 

 in the computation of all constants reported. 



Among the animals with cerebral lesions many failed to 

 reach the criterion within 150 trials. This affects the error 

 scores very little; inspection of the records reveals that 80 

 per cent of the total errors are made in the first 50 trials, 

 and that by 150 trials the animals have settled down to 

 rather stereotyped runs with at most 2 or 3 errors per trial. 

 In computing correlations based on trials for learning, we 

 have used total trials minus the number of errorless runs 

 made before the termination of training, to avoid throwing 

 all of these cases into one rank. 



None of the conclusions which we have drawn is dependent 

 upon any of these special methods of grouping the data. That 

 is, the group differences and correlations are essentially the 

 same, within the limits' of reliability which we have required, 

 whether we use total trials, trials less errorless runs, total 

 errors, or total errors less errors in the first trial, total time, 

 or total time less time for the first trial. 



In view of the large number of animals which failed to 

 reach the criterion of learning within the training given, some 

 method of extrapolating the learning curves and predicting 



