814 



MEMOIRS NATIONAL ACADEMY OF SCIENCES. 



[Vol. XV, 



with low grades. The present data do seem to establish the fact of a definite tendency for 

 the older men to obtain slightly lower scores than the younger; the difference is as it has been 

 claimed but it is not great. The interpretation of this tendency is another matter; it can 

 not be said on the basis of present information to point to a decrease of intelligence with age, 

 or even to a decrease with age of the ability to succeed in the so-called "speed test" alpha. 



Table 866 gives the comparative data on 15,385 white officers from Group VI of the 

 principal sample. These data are shown graphically in figures 55 and 56. The class intervals 

 of age are those coded in the principal sample; they proceed by two-year intervals within the 

 limits of the draft (i. e., up to 30 years) and thereafter by decades. It will be noted that the 

 A ratings decrease and the C ratings increase with age. The medians regularly decrease. 

 The graphic representation in figures 55 and 56 is striking. The extreme groups (less than 

 21 and above 60 years) are the smallest in size and may be left out of account in the general 

 tendency. 



150 



145- 



J0 140 - 



a 



o 



a 

 m 



r 

 a 



< 



2 130- 

 < 



O 



UJ 



2 

 \2£-\ 



120- 



115- 



II0- 1 



20 & less 



21-22 



23-24 



15-26 



27- 28 



29-30 



31-40 



41-50 



61-60 



AGE GROUPS (YEARS; 



Fig. 55. Intelligence ratings and age. Median alpha scores for different age groups of 15,385 whito officers. 



Table 366. — Relation of age to intelligence rating: 15,SS5 white officers of Group VI of the principal sample. Examina- 

 tion alpha. 



