100 PSYCHOLOGICAL METHODS OF TESTING INTELLIGENCE 



other, their combination does little more that the 

 testing by any one of them would do. Binet and 

 Simon did not keep this principle sufficiently in 

 mind : some of their age-levels contain only linguistic 

 tests and no tests of activity. 



Furthermore, the age-levels, considered as wholes, 

 must also be adjusted, for to demand that particular 

 tests be passed and to demand that all five tests of a 

 given age-level shall be passed are two entirely dif- 

 ferent things. This adjustment is rendered more dif- 

 ficult by the fact that in computing mental age one 

 must not only deal with the tests of one age-level, but 

 also make supplementary use of tests from the higher 

 levels; accordingly, in this adjustment of the levels 

 as a whole attention must be paid to the interrela- 

 tion of tests that come into consideration in connec 

 tion with different near-by age-levels. 



The controlling principle for the adjustment or 

 standardization of the age-levels is that approxi- 

 mately symmetrical distribution of the mental ages 

 must prevail for each level. That is, the tests are 

 properly arranged and skillfully assembled into a 

 system if, when a large number of unselected normal 

 children of a given age are tested, a large middle 

 group stand 'at age' and the rest are divided fairly 

 equally between advanced and retarded cases. 



To carry out such investigations practically it 

 will be necessary to try as many tests as possible 

 with each pupil; in this way it will be feasible to 

 assign the passing of each particular test to this or 

 that age-level and to discover the general arrange- 

 ment of the tests that furnishes the closest to a sym- 

 metrical distribution. 



