Abstract
Research suggests a larger Stroop interference effect in older than younger adults. However, it is not clear whether this age-related difference is due to a general slowing of information processing, impairment of inhibitory processes involved in selective attention, or cautionary response strategy. To address this limitation, we asked young and old participants to name the color of one of two orthogonally superimposed shapes while ignoring two identical color-names which were either congruent or incongruent to the color of the target shape, and located either in the target shape, in the distractor shape, or in the background. We fit a dual-stage two-phase model of selective attention to each individual’s data. This model assumes that response selection in a Stroop task happens in two stages: an early stage, which is influenced by attentional weight of both the target and distractor, and a late stage, which is derived from the identity of the target. Comparing the estimated parameters across the two age groups indicated that older adults adopted a more conservative response selection boundary and required more perceptual evidence to make a decision. Moreover, at the first stage of response selection, the rate of evidence accumulation for selection of the target was lower in older adults, whereas both groups had a similar evidence accumulation for selection of the distractors. In the second stage of response selection, older adults showed a lower rate of evidence accumulation. However, older adults showed a higher rate of evidence accumulation for the target identification in the later stage of attention selection. These results indicate an impairment of response selection processes in older adults, though they seem to be better at attending the target stimulus at later stages of response selection. In conclusion, these results shed light on the impact of aging on inhibitory processes involved in selective attention.