THE METHOD OF AGE GRADATION 105 



Hence, however enticingly simple they may be, we 

 shall have to give up the use of the rough whole-year 

 designations, like 1, 2, 3 years of retardation, and 

 make use of fractional values: it is enough, of 

 course, to carry them to the first decimal place. In 

 figuring mental age each single test passed in excess 

 must, then, represent a fraction of a year. If, for 

 example, two of the five 8-year tests are passed, then 

 2/5 is to be added to the mental age; the child in 

 our example just above would then have obtained a 

 mental age of 7.4 years. Terman and Childs (64) 

 are already making use of such a mode of calcula- 

 tion, only theirs is made rather awkward by the pres- 

 ence of different fractional values in the several 

 years : when the year contains seven tests, each test 

 has only the value one-seventh, when five tests, one- 

 fifth. This feature, too, confirms our desideratum al- 

 ready expressed that every one of the years should 

 contain just five tests, then each test would have the 

 same value, 0.2 of its year. 



But now, once the use of the convenient whole 

 numbers be given up, every objection against the in- 

 troduction of the mental quotient is removed, for this 

 furnishes us a single fractional value in place of the 

 two fractional values, chronological age and mental 

 age. This quotient lies for normal children in the 

 neighborhood of 1.00 and grades off continuously 

 from this value in both directions. As compared 

 with the older method of dividing by the rough units 

 of the age-levels, the use of the quotient has surely 

 the advantage of affording a certain smoothness and 

 continuity in the results, since the fraction (mental 

 age divided by chronological age), when the deci- 



