THE METHOD OF AGE GRADATION 95 



Since the process of mental development brings 

 into maturity in succession a series of different part- 

 functions, it follows that for each age there should 

 be a series of tests to correspond to the phenomena 

 of development that have just appeared; it must be 

 possible, with the aid of the principle of decided ad- 

 vance with age, to pick these tests out from a num- 

 ber of others. 



Again, the matter of correspondence between the 

 results of different investigations must be consid- 

 ered in the selection of the tests. A test that grades 

 the same or nearly the same with German, French, 

 English and American children has naturally more 

 claim to be included in the final system than one that 

 varies markedly with the examiner or with the ex- 

 aminees. The table that Bell (32) has prepared is 

 instructive in this connection. He presents, side by 

 side, the age-rank that each of the Binet-Simon 

 tests would have attained on the basis of the results 

 of Binet, Levistre and Morle, Johnstone, Groddard, 

 Bobertag, and Terman and Childs. 23 



In many of the tests the variations are quite large; thus, the 

 test of "comparing two objects from memory" ranges from the 6th 

 year (Johnstone) to the 9th year (Terman and Childs), the test 

 of "naming 60 words in three minutes" from the 10th year (God- 

 dard) to the 15th year (Levistre and Morle, Terman and Childs). 

 The assignment of such a test to a single age-level becomes, then, 

 evidently an arbitrary matter. Over against these are other tests 

 that show great constancy, at least so far. Thus, "counting 13 

 pennies," "esthetic comparison," "showing right hand and left 



23 It must be remembered that the tables and materials from 

 which Bell had to construct his summary have been assembled so 

 differently by the different investigators that their gauging of the 

 several tests is not really directly comparable, so that Bell's tables 

 must be regarded merely as a preliminary attempt at checking up 

 the results of various investigations. 



