AGE, SPEED OF INFORMATION-PROCESSING, RECALL, AND FLUID INTELLIGENCE

On three occasions, 63 adults, ranging in age from 26 to 80 years, all in good health, were tested with three speed of information-processing paradigms (the Sternberg, the Posner, and the Hick), two long-term free-recall tasks, and, as a measure of fluid intelligence, the Raven Advanced Progressive Matrices (RAPM) test. Whereas within-condition latencies for the three of the information-processing tasks and recall scores were found to be reliable and consistently correlated with age and RAPM, individual differences in within-condition accuracies and between-condition slopes produced by the three information-processing tasks were found to be unstable over time and unrelated to age and RAPM. As suggested by Salthouse (1985), a large portion of the age-related differences in fluid intelligence was found to be accounted for by age-related declines in a general latency factor (cognitive speed). Furthermore, in agreement with Salthouse, this general latency factor appeared to reflect more than what can be accounted for by the simplest of information-processing tasks (simple reaction time). Finally, given that free recall had a substantial independent effect on RAPM when age and latency were held constant, the results called into question the assumption that cognitive speed can account for all individual differences in IQ.