AGING, COGNITIVE PERFORMANCE, AND MENTAL SPEED

Measures of four-choice reaction time (RT), inspection time (IT), and scores on a speeded coding-substitution task obtained from 104 subjects aged from 54 to 85 years were found, separately or together, to account for almost all age-related changes in cognitive performance on a number of performance indices reflecting general fluid ability. However, measures of information-processing speed did not entirely predict some aspects of memory performance. These correlations were not due to the inclusion of persons who had lower than average IQ scores or who were over 80 years old, or to the fact that some psychometric tests were scored to a time limit. The results also showed that higher intelligence does not serve to protect against the effects of aging, because rates of decline with age in scores on tests of spatial ability, and in memory and in information-processing tasks were the same within two subgroups selected for higher and lower verbal crystallized abilities.