SPEED AND INTELLIGENCE IN OLD-AGE

Past research suggests that age differences in measures of cognitive s peed contribute to differences in intellectual functioning between you ng and old adults. To investigate whether speed also predicts age-rela ted differences in intellectual performance beyond age 70 years, tests indicating 5 intellectual abilities-speed, reasoning, memory, knowled ge, and fluency-were administered to a close-to-representative, age-st ratified sample of old and very old adults. Age trends of all 5 abilit ies were well described by a negative linear function. The speed-media ted effect of age fully explained the relationship between age and bot h the common and the specific variance of the other 4 abilities. Resul ts offer strong support for the speed hypothesis of old age cognitive decline but need to be qualified by further research on the reasons un derlying age differences in measures of speed.