A decomposition of age-related differences in multitrial free recall

The relative roles of acquisition and forgetting in mediating age-related differences in multitrial learning were evaluated by having 258 adults (18 to 94 years of age) complete five study and free-recall test trials of 15 words. Performance across trials was decomposed into (a) gained access, corresponding to the proportion of items recalled on trial n+1 of those that were not recalled on trial n (hence tapping processes related to acquisition), and (b) lost access, corresponding to the proportion of items not recalled on trial n+1 of those that were recalled on trial n (hence tapping intertrial forgetting). Age-related differences occurred both in gained access and in lost access, although acquisition seemed to play a larger role in mediating age-related differences in learning than did forgetting. Also, a composite measure of processing speed shared 63% or more of the age-related variance in measures of free recall. The overall pattern of results is consistent with the view that age-related decreases in the speed of completing elementary encoding operations contribute to poorer learning by leading to weaker representations of the to-be-remembered items.