THE METHOD OF AGE GRADATION 83 



There appears a clear separation of the points of 

 maximal frequency for the chief groups, and, it is 

 to he noted, the mental quotient of the ' not-abnormal' 

 children lies mostly between 0.81 and 0.90, that of 

 the morons between 0.71 and 0.80, that of the im- 

 beciles between 0.61 and 0.70 all quite in accord- 

 ance with our earlier figures. In the case of the im- 

 beciles the range of the quotients is wider than with 

 the other groups, as the average values had already 

 shown. Attention should be called to the fairly 

 symmetrical form of the three curves : this brings it 

 about that the point of maximal frequency and the 

 average tend to coincide within each group. 



The transitional character of the group of doubt- 

 fully defective also finds expression typically in that 

 its members are distributed fairly uniformly over 

 the regions that are characteristic on the one hand 

 of the normals and on the other hand of the un- 

 doubted morons. 



The number of the children tested by Chotzen is 

 not yet large enough and particularly their distri- 

 bution over the different age-levels is not wide 

 enough to consider the above figures as having con- 

 clusive value for other sets of material, yet they do 

 seem to me so far removed from objection as to 

 demonstrate that the mental quotient is a very much 

 more useful measure of backwardness than the com- 

 monly used absolute difference. 



The quotient does not seem, however, to afford an 

 actually constant expression of degree of feeble- 

 mindedness, but shows a tendency to fall in value as 

 age increases. This tendency, it is evident, is but 

 slight within the limits of age that have been men- 



