THE METHOD OF AGE GRADATION 37 



pressed by the stage whose tests could just be passed 

 by the child: a subject who readily passed all the 

 tests up through the 9-year ones, but failed with the 

 10-year and subsequent ones, would, accordingly, 

 possess a nine-year grade of intelligence. 



But things are never quite so simple in actuality 

 as they are in theory. The varying tests of any 

 given age-level we may call them a. b. c. d. e, are 

 not all equally difficult for all children, but there are, 

 on the contrary, quite remarkable individual varia- 

 tions. One child passes a to d, but fails with e; an- 

 other passes a, c and e, but not b and d. This is due 

 in part to momentary fluctuations of attention, 

 fatigue, etc., that must, of course, always be reckoned 

 with, but in part also to qualitative differences in in- 

 telligence. The correlation between the different 

 phases of intellectual functions is truly never so high 

 that a positive accomplishing of test a must neces- 

 sarily entail a like accomplishing of the approxi- 

 mately * equally diffcult' tests b, c and d. 



And so it comes about that there is no hard and 

 fast boundary between the age-level that a child 

 passes completely and the levels that are unquestion- 

 ably beyond his powers ; rather is there an interme- 

 diate territory of greater or less extent within which 

 successes and failures are scattered in irregular 

 fashion: we shall call this the area of irregularity 

 (Gebiet der Staff elstreuung). It is impossible to de- 

 rive a mean or average value from the data afforded 

 by this area without proceeding in a somewhat arbi- 

 trary manner, but the formula proposed by Binet 

 and Simon seems to have answered very well so far. 



