Effects of aging on the speed and attentional cost of cognitive operations

Abstract

Normal aging is associated with slowing and increased attentional cost of both early and late stages of information processing in discrimination and search tasks. We examined whether increased attentional costs in older adults are modulated by age range (young‐old vs. old‐old), encoding‐stage duration, and amount of practice. A dual‐task paradigm involving a successive letter‐matching task and a probe‐reaction time (RT) task was used. Probes were presented at different temporal locations during the matching task to probe both early (encoding) and late (matching/response selection) stages of processing. Aging was associated with increased attentional costs (as reflected in probe RT) of encoding at 50 msec after letter presentation but no later. However, this effect was largely due to very fast responding to encoding probes by young adults. Older adults showed greater attentional costs for the late stage of processing than young adults. This effect was present for both young‐old (60–69 years) and old‐old (70–79 years) subjects and was not attenuated by practice. The results indicate that the attentional demands associated with late matching and response‐selection stages increase with age and are most responsible for age‐related slowing in choice RT. These age differences are not attenuated with practice.