334 'Journal of Comparative Neurology aud Psychology. 



The results on four cats are first reported, all of which were practiced until they 

 could release themselves from the box in from i to 6 seconds. Both frontals were 

 then removed. During periods varying from seven to fourteen days after the opera- 

 tion these animals were tested and were found to have lost the habits that they had 

 formed. In these, and in the other cases as well, two minutes were given the animal 

 in which to open the box. On ten monkeys the same operation (severance of both 

 frontals), after the required habit had been formed, resulted in the loss of the habit 

 by six of the animals and its retention by four, although the time of performance, 

 in the latter cases, was somewhat longer than before the operation. 



As the result of the experiments designed to test the ability of the animals to 

 learn a habit for the first time after the operation (on- both frontals) had been per- 

 formed, or to relearn it after it had once been lost as a result of the operation, it 

 was found that two cats easily acquired the box habit after both frontals had been 

 severed from the rest of the cerebrum and that two of the cats and two of the mon- 

 keys could relearn the habit lost after operation. In the case of one of the cats 

 that learned the habit after operation the author remarks that "the curve of learning 

 in this animal was about the same as that in an animal before the removal of the 

 frontals" (p. 57). 



That the loss of newly acquired habits after the removal of the frontal lobes, 

 which is the more frequent result in these experiments, is not due to surgical shock 

 and does not result after the removal of other parts of the cerebrum is shown by the 

 cases in which habits were retained even after the frontal lobes had been severed 

 and by others in which the parietal lobes were removed without detriment. 



The inference that the author draws from his results and from those of other 

 investigators is that "the frontal lobes are concerned in normal and daily associa- 

 tional processes and that through them we are enabled to form habits and, in gen- 

 eral, to learn" (p. 64). Four cases were mentioned, however, in which the formed 

 habit was retained after cutting away both frontals, two in which the habit was 

 learned for the first time after the operation and four in which it was relearned. 

 The author suggests, in explanation, since the learning period, in those cases in 

 which the habit was retained even after operation, was longer than in other cases, 

 that it had become a reflex and was therefore due to the functioning of the lower cen- 

 ters, identifying these cases with others in which he observed that habits of long 

 standing, such as coming on call or jumping on the experimenter's shoulder, were 

 also retained after the operation. The instances of learning and of relearning, after 

 the removal of the frontal lobes, he supposes to have been due to the activity of the 

 still uninjured parts of the cerebrum, in particular of the remnants of the frontal 

 lobes still left intact after operation. Both suggestions are interesting but, as 

 the author himself feels, further and more crucial experiments are needed to define 

 the exact difference between a new habit (not retained after operation) and an 

 old habit (retained). It is unfortunate, in this connection, that no exact record is 

 given of the length of the whole training period for each animal, of the intervals 

 between tests and of the number of trials at each test. Yerkes' has recently shown 

 the importance of such records in determining the efficacy of training. Further, 

 if those portions of the frontal lobes which were severed from the rest of the brain 

 are normally concerned in the formation of habits, ought habits to be learned 



1 Yerkes, R. M. The Dancing Mouse. XewTork. 1907. 



