Age differences in inhibition and episodic retrieval in task switching: a drift diffusion model analysis of <i>N–2</i> repetition costs

Successful task-switching performance is thought to rely on inhibitory mechanisms suppressing no-longer-relevant tasks, indexed by the n–2 repetition cost. Recent work has shown that episodic retrieval contributes to this cost, confounding estimates of inhibition. This study examines age-related differences in the contributions of inhibition and episodic retrieval to the n–2 repetition cost using a paradigm that controls episodic interference. We also applied the drift diffusion model (DDM) to estimate latent processes underlying these effects. Results showed robust n–2 repetition costs for younger and older adults in response times which reduced when episodic interference was controlled. However, only younger adults showed this pattern in error rates. The DDM showed n–2 repetition costs and their modulation by episodic retrieval were isolated to drift rates, reflecting changes in evidence accumulation. Only younger adults’ drift rates were affected by episodic retrieval, with n–2 repetition costs reduced under episodic match conditions. Older adults showed n–2 repetition costs in drift rate regardless of episodic match, suggesting age-related differences in episodic retrieval at the latent level. The results provide insight into age-related differences in inhibition, the importance of controlling episodic retrieval effects in task switching, and the value of computational modelling in revealing age-related differences.