MECHANISMS OF LEARNING 179 



The experiments clearly reveal a very peculiar re- 

 lation of the cerebral cortex to this habit. After de- 

 struction of the visual areas of both cerebral hemi- 

 spheres, rats can learn this habit as readily as do nor- 

 mal animals; but if rats which had acquired the habit 

 with the cerebral cortex uninjured were then deprived 

 of the posterior thirds of both hemispheres, then the 



Fig. 41. — The total extent of all of the lesions in rats that lost the 

 habit of visual discrimination after operation (stipple). The solid black 

 area was common to all. After Lashley. 



habit was totally lost. Upon resumption of training 

 after the operation the habit was reacquired in about 

 the same number of trials as were requisite in the ini- 

 tial training. Figure 41 illustrates in stipple the total 

 area involved in all of these operations and in solid 

 black the area common to all of them. The latter field 

 coincides approximately with the visual projection 

 area as defined anatomically (area w of Fig. 38, p. 

 158), Clearly this area is related with the perform- 

 ance of the habit, but it is not necessary for its acqui- 

 sition. 



More than a hundred and fifty animals were 

 trained in this habit, and the effects of various opera- 



