104 PSYCHOLOGICAL METHODS OF TESTING INTELLIGENCE 



tions of ages into account without special half-year 

 steps (see p. 105, below). 



Finally, mention may be made of other desires, 

 curae posterior es: differentiation of the scales for 

 children of different social strata, for the two sexes, 

 and especially series devoid of the speech factor for 

 the testing of the deaf and dumb, etc. 



(d) The computation of the final values. There 

 are two main difficulties that demand our attention 

 here. 



The one consists in the limitation of the measures 

 of the mental age and the chronological age to ivhole 

 numbers. This necessity of using whole numbers 

 must often entail an arbitrariness that renders im- 

 possible the carrying out of the method with pre- 

 cision. 



For instance, a child who, when tested, lacks four months of 

 completing his eighth year of life, must of necessity be classed as 

 "8 years." If he passes the 7-year-old tests and two more, he still 

 receives the mental age of 7 years, and is, accordingly, credited 

 with a mental retardation of one year, although in reality there is 

 practically no retardation at all. 



Bobertag 29 tried to circumvent this difficulty by 

 taking for his testing only those children that were 

 close to their birthday (at least within 2 months). 

 But usually there is no chance for free choice like 

 this : there are certain children to be tested, regard- 

 less of what their age happens to be at the time. Be- 

 sides, that kind of selection at most only lessens the 

 difficulty for the chronological age, not for the mental 

 age. The failure to consider the two or three ex- 

 cess tests passed still remains as a defect in the cal- 

 culations. 



29 40, I, p. 110. 



