CEKEBBAL FUNCTION IN LEAKNING 103 



control of the thumb in the chimpanzee after the normal area had 

 been destroyed. They did determine that the function was not 

 taken up by adjacent areas. It would have been possible to 

 make such determinations in the present series by operating sub- 

 sequent to training but a second operation makes it difficult to 

 delimit the first lesion exactly and it seemed best to restrict the 

 present work to the investigation of the vicarious functioning of 

 the cerebrum and to postpone the working out of the exact areas 

 functioning to a later time. 



Third, the existence of a special area for attention or for 

 " higher psychic functions" is ruled out. If there is any differ-^ 

 ence, the operated animals show somewhat more definite limita- 

 tion of behavior to reactions to the problem situation than do 

 normals and the double-platform box certainly demands " intel- 

 ligence" if we can use the term in reference to any animal. 



Finally, the experiments raise another question of fundamental 

 importance. What becomes of the concept of sensory and 

 motor projection areas if the entire cerebral cortex of the rat is 

 equipotential in learning? The following sections of this paper 

 record an attempt to answer this question. 



V. THE FUNCTION OF THE CEREBRUM IN THE RETENTION OF A 

 HABIT OF VISUAL DISCRIMINATION 



The formation of the double-platform box habit involves at 

 least the linking up of tactile and kinaesthetic impulses with 

 motor reactions. Other sense organs probably play only a minor 

 r61e. We do not know the position of the kinaesthetic projec- 

 tion area in the rat, but it probably has some such position as in 

 the cat (Barenne, '16) where it seems to be not clearly separated 

 from the motor area. Whatever its position, if it is definitely 

 localized, it was certainly destroyed in some of the experiments, 

 yet none of the animals gave evidence of loss of kinaesthetic im- 

 pulses. The exact function of these in the behavior of the rat 

 is difficult to determine, however, and it seemed desirable to 

 have data on learning involving some stimulus which can be ex- 

 perimentally controlled, in order to determine whether there are 



