What is still working in working memory in old age: Dual tasking and resistance to interference do not explain age-related item loss after a focus switch

Abstract

Objectives.In 2 experiments, we examined the oft-replicated finding of age-related differences in accuracy at retrieving items stored in working memory, but outside the focus of attention. Specifically, we investigated whether such differences could be explained by (a) age-related differences in coping with the dual-task nature of swapping items into and out of the focus of attention and/or (b) age-related differences in resistance to interference.Method.We used a modified version of the N-Back task with stimuli of different levels of difficulty, and experimental manipulations aimed at isolating the dual-task and interference effects.Results.We found both explanations lacking: We obtained a dual-task cost (Experiment 1) and an interference cost (Experiment 2), as well as a large age effect (Cohen's d = 1.6 in Experiment 1 and 0.7 in Experiment 2) but neither the dual task nor the interference effect was sensitive to age.Discussion.These findings, combined with previous failures to find an explanation for the age effects, suggest that item availability after a focus switch might be an important new and fundamental variable - a cognitive primitive - potentially necessary for a full understanding of age effects in higher order cognition. © The Author 2012. Published by Oxford University Press on behalf of The Gerontological Society of America. All rights reserved.