Differences in Behavior 



2 73 



persisting in my efforts to obtain comparable data for the 

 seven ages which have been mentioned. 



The detailed results for the one-month old individuals 

 appear in Table 43 ; those for the four-month individuals in 

 Table 52. The general averages for the former are to be 

 found in the third column of Table 46, under the heading 



130 

 120 



no 

 100 



80 



80 

 70 



] -4 7 . 10 13 



FIGURE 33. Plasticity curves. In the left margin are given the indices of 

 modifiability (the number of tests necessary for the establishment of a perfect 

 habit). Below the base line the age of the individuals is given in months. Curve 



for males, ; curve for females, ; curve for both males and 



females, . When these three plasticity curves are completed, they will repre- 

 sent the indices of modifiability as determined for ten individuals at the age of 

 i month, and similarly for the same number of individuals at each of the ages, 

 4, 7, 10, 13, 16, and 19 months. 



" 10 tests per day" ; those for the latter in the last column of 

 Table 52. Mere inspection of these tables reveals the curious 

 sex difference which goes far towards justifying the presenta- 

 tion of this uncompleted work. The index of modifiability 



