The attentional demands of encoding and retrieval in younger and older adults: 2. Evidence from secondary task reaction time distributions

Three studies examined the effects of encoding or retrieval on properties o f secondary task reaction time (RT) distributions in younger and older adul ts. Relative to full attention conditions, encoding and retrieval increased secondary task RT medians and standard deviations more for older adults th an for younger adults, and the age-related RT increase was most pronounced among the slowest RTs. Hierarchical regression analyses revealed two age-re lated mechanisms underlying these effects, which were interpreted as cognit ive slowing and reductions in attentional resources. Cognitive slowing affe cts the entire RT distribution regardless of the memory task. By contrast, reduced attentional resources result in very long RTs, especially when the tasks require self-initiated encoding or retrieval operations.