Processing speed and memory in aging and dementia

We examined the role of processing speed (PS) as a mediator of age- related and dementia-related differences in cried recall and text memory. Consistent with previous research, statistical control of PS significantly attenuated or eliminated age differences on each of the memory measures. However, age-related decline in the ability to benefit from conditions of increased encoding specificity was not mediated by PS. In contrast to the results for age effects, statistical control of PS did not significantly attenuate dementia-related memory differences, suggesting that processing speed is not an important dementia-related memory impairment. The implications of these findings for interpreting residual age effects and the possible influence of preclinical dementia on studies of normal aging are discussed.