76 K. S. LASHLEY 



box. Any deviation from the direct path or pause to sniff at 

 the door or other part of the problem box was counted as an error. 



\ Three trials were given daily and three successive trials without 

 error must be made in one day before learning was considered 



/ perfect. 



L 



Experimental data 



Five types of operations were used for comparison and an at- 

 tempt was made to test several animals with each type of lesion. 

 The groups covered by the experiments were the following : 



Group 1. Normal animals 10 



Group 2. One hemisphere removed 6 



Group 3. Occipital regions of both hemispheres destroyed 4 



Group 4. Parietal regions of both hemispheres destroyed. 5 



Group 5. Frontal poles of both hemispheres destroyed 2* 



Group 6. Frontal and parietal regions of both hemispheres de- 

 stroyed 2* 



* The experiments of Lashley and Franz cover these regions and the training 

 of these additional animals was undertaken only as a check on the earlier work. 



The technique used in training all the groups was the same and 

 there is no reason to believe that they differed in any other respect 

 than the amount of functional cerebral cortex. The records of 

 individual experiments follow. 



Group 1. Normal animals. The ten normal animals were 



trained before the operative experiments were begun, as controls 



rin an experiment on the action of drugs. Except for the season 



during which training was carried out, they did not differ from 



Uhe operated animals, and the difference even here was slight, 



since training of the latter was begun before the normals had 



completely learned their problem. The records of the animals 



of this group are given in table 2, together with the records of the 



other groups, and their average time per trial in successive day's 



practice is shown in table 3. 



T^he average number of trials required for learning by members 

 I of the group was 142.6 =t 9.2. 



Group 2. Hemidecerebrate animals. In this group the object 

 was to destroy one hemisphere completely while leaving the other 

 intact. Complete destruction was obtained in only one case, 



