48 PSYCHOLOGICAL METHODS OF TESTING INTELLIGENCE 



From the data given it can be computed that there were above the 

 level of their age a full 50 per cent, of the 7-year olds, 20 per cent, 

 of the 8 and 9-year olds and only 14 per cent, of the 10 and 11-year 

 olds. 



TABLE II. 

 PERCENTAGES RETARDED, AT AGE AND ADVANCED AT DIFFERENT YEARS. 



Chronological 



Investigator Age Retarded At Age Advanced 



5 12 35 53 



6 20.5 30 49.5 



7 13 58 29 

 Goddard {8 44 41 15 



9 40 28 32 



10 27.5 56 16.5 



11 56 36 8 



5-6 11 60 29 



Bobertag \ 7-8 7 48.5 44.5 



[ 9-11 34 50 16 



\ 6-7 12 20 68 



Johnstone. . . .\ 8-9 20 40 40 



[10-11 62 25 13 



In the work of the Americans, Terman and Childs (64), and of 

 Mile. Descoeudres (46), of Geneva, we find another method of 

 presenting data, but the same result. The first-named tested 396 

 unselected children and figured the average value of each age; 

 they found that the young children attained a much too high level, 

 the older children a too low average level of intelligence, so that, 

 on the whole, the mental levels were more like one another than 

 were the chronological levels. It follows that the tests fail to 

 bring fully to light the actual differences between the children. 

 Mile. Descoeudres had tested in all only 24 children of six different 

 ages ; the results showed differences of only two to four years in 

 the mental ages of children in the youngest and oldest groups, 

 though the chronological ages differed by six years. 



All these findings show, first of all, that the ar- 

 rangement of the tests set forth by Binet and Simon 

 in 1908 suffer from not inconsiderable errors that 

 must be removed. Binet himself has recognized 

 these defects, too, at least in part, for he subse- 

 quently relegated the tests for 11, 12 and 13-year 

 subjects to higher age-levels. 



