Parsing inhibitory and mnemonic contributions to age-related decline in cognitive flexibility

Cognitive flexibility is the ability to shift between mental sets in response to changing goals or environments, and it is known to decline across the adult lifespan. Competing accounts attribute this decline either to weaknesses in specific abilities such as inhibition or memory, or to more global challenges in managing the interaction between them. Efforts to disentangle contributing processes through targeted, single-function tasks have produced mixed findings, potentially due to confounding variability in stimuli and task demands.The current work contributes to the field's understanding of cognitive flexibility decline by focusing on \emph{inhibition} as both a subcomponent and as an independent process, given its central role in both specific-deficit and integrative theoretical accounts. In particular, we designed a unified task that engages both 1) cognitive flexibility through shifting requirements to encode task-relevant mental sets and inhibit them once they become outdated; and 2) discrete item-level inhibition of perceptual distractors. We tested 86 adults aged 18–73. Accuracy analyses revealed asymmetric interaction effects between aging and these two operations: while learning after a rule-switch worsened as age increased, inhibition of perceptual distractors inhibition improved. We then applied a computational model to quantify how memory precision and the inhibition of previously-relevant sets each contributed to performance. Model fits indicated that age-related decline in learning across rule-switches were driven primarily by reduced memory precision, not by deficits in inhibition.