246 'Journal of Cof?iparative Neurology and Psychology. 



training series, but thereafter they make fewer errors and their train- 

 ing is completed with fewer series than that of the males. In other 

 words, the general averages of Table 5 indicate that a group of twenty 

 female dancers, ranging in age from one month to twelve months, 

 acquired the habit of discriminating between two boxes, whose only 

 considerable difference was in amount of illumination, and of choos- 

 ing the white box much more quickly than did a comparable group of 

 twenty male dancers. This is especially interesting in view of the 

 fact next to be noted. 



(3) The one-month males exhibit a considerably less strong 

 Ijreference for the black box than do the one-month females and, at 

 the same time, they acquire the habit much the more quickly. The 

 reverse is true of the four-month groups : the males exhibit the 



TABLE 6. 

 Indicks of Plasticity fob Dancers of Different Ages. 



* One male and two females whose ages were twelve months are included. 



stronger preference for the black to begin with and learn somewhat 

 less rapidly. 



(4) The males acquire the white-black habit more quickly at 

 the age of one month than at the ages of four, seven, or ten months. 

 And the females likewise acquire the habit most readily at one month 

 of age. 



Several of the above facts are clearer in the light of the results 

 of Table 6, in which are arranged the indices of plasticity for the 

 several groups of dancers, and the number of trials which, in the 

 case of each group, preceded the first correct series of choices. The 

 indices are given in the columns headed "total number of training 

 tests." Judging by these indices we may say that the plasticity of the 

 male dancer, as measured by the particular habit under consideration. 



