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 



] -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, 1 6, 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 



