80 PSYCHOLOGICAL METHODS OF TESTING INTELLIGENCE 



The results of Chotzen that now lie before us per- 

 mit us to test the feasibility of a relative measure of 

 this sort. I should like to recommend the relating 

 to chronological age not of the difference, but of the 

 mental age itself. We would then obtain the mental 

 quotient that has already been mentioned (p. 42). 

 This quotient shows what fractional part of the in- 

 telligence normal to his age a feeble-minded child 

 attains. Mental quotient -- mental age -f- chrono- 

 logical age. An 8-year old child with a mental age 

 of six has, then, a mental quotient of 6/8 = 0.75. A 

 12-year old child with a mental age of 9 has the same 

 mental quotient. 



TABLE XII 

 AVERAGE MENTAL QUOTIENT OF THE CHILDREN IN TABLES X AND XI 



Chronological Not Doubtful 



Age Feeble-minded Defect Morons Imbeciles 



8 0.92 0.84 0.76 0.71 



9 0.85 0.81 0.77 0.67 



10 (0.80) (0.80) 0.74 0.62 



11 (0.73) (0.68) 0.71 (0.64) 



12 (0.75) (0.75) (0.73) (0.61) 



13 (0.73) 



Now when we turn into quotients the values cal- 

 culated from Chotzen in Table XI, we obtain Table 

 XII. The idiots have been omitted for reasons that 

 will appear later. The figures in brackets are those 

 that cannot be deemed reliable averages on account 

 of too few individuals included in them. The table 

 reveals mental quotients for the two main forms of 

 feeble-mindedness that are, it is true, not constant, 

 but that are, however, very similar through several 

 chronological years. The morons, in especial, show 

 surprisingly uniform values ; their average quotient 



