Mental Aspects of Ageing 39 



})rinie, we cannot tell whether a low score on one or many 

 tests betokens a neoligible decrement on an originally low 

 achievement or, on the other hand, a gross falling off from a 

 previously high attainment. It is true that we attempt to 

 distinguish between these by devices which assume that some 

 abilities (especially vocabulary) are almost wholly retained 

 while others decline; we therefore detect and measure the 

 dechne in terms of this disparity. But such devices are, in 

 practice, weak: they hardly do justice to the individual differ- 

 ences in constancy or otherwise of vocabulary and information 

 as people grow older, and they cannot tell us at what rate 

 decline has occurred, or will occur in the future. Moreover, the 

 decline must be fairly gross to be detected with confidence. 



It has been urged that the degree of decline in any indivi- 

 dual is inversely related to the optimal level of intelligence: 

 the more stupid he is, the faster he will become stupider still 

 as he grows old: if he is bright he will remain bright. These 

 findings bespeak an academic bias. It is true that in 45 

 University professors, aged sixty to eighty, exacting tests 

 showed no unambiguous evidence of decline: but perhaps 45 

 manual labourers aged sixty to eighty who had lived satisfy- 

 ing and healthy lives would also show no unambiguous evi- 

 dence of decline from their more modest level of intelligence. 

 Moreover in old people so many allowances must be made for 

 sensory and motor defects and unfamiliarity with test 

 procedures that assertions about the more rapid decline of 

 intelligence in the less intelligent must be scrutinized very 

 critically. 



On the question of deterioration in the highly intelligent, 

 however, we can profit by the painstaking labours of Harvey 

 Lehman. Limiting himself to the relationship between 

 chronological age and outstanding achievement in science, 

 medicine, philosophy, music, art and literature, he found that 

 in all of these the maximum production of first-rate work 

 had occurred before the age of forty, but that there are many 

 instances of exceptional powers retained into the eighth decade 

 of life. Verdi, for example, composed Otello at seventy-three 



