Cautionary response strategy and impairment of post-conflict response selection underlie age-related differences in an object-based Stroop task

Research suggests that older adults have deficits in selective attention, an effect often queried through the Stroop task. To tease apart whether this is due to failures to inhibit distracting information or to upregulate attention to target information, younger and older adults completed a task called the Shape Stroop in which they had to name the color of a shape that was occluded by another shape. Critically, congruent or incongruent Stroop words were placed in either the target shape, the occluding (distractor) shape or in the background. We first modeled performance as a function of age group, Stroop word congruency and location. The results indicate that older adults were more accurate but slower than younger adults to choose the correct shape color. To further probe how early and/or late attentional processes contribute to performance and to interrogate the decision strategies adopted across different conditions, we also fit the dual-stage two-phase model of selective attention to our data. Our results indicate that older adults have more conservative response and stimulus selection boundaries. They also showed a lower rate of evidence accumulation in the second, but not in the first phase of response selection, suggesting that inhibitory processes are spared in older adults. These results suggest that typical age-related deficits in the Stroop task may be due to older adults requiring more information to make a decision and having impairments during the later stages of attentional processing.