Distractor-relevance determines whether task-switching enhances or impairs distractor memory.

Richter and Yeung (2012) recently documented a novel task-switching effect, a switch-induced reduction in "memory selectivity," characterized by relatively enhanced memory for distractor stimuli and impaired memory for target stimuli encountered on switch trials compared with repeat trials. One interpretation of this finding argues that task-switching involves opening a "gate" to working memory, which promotes updating of the task-set, but at the same time allows for increased distraction from task-irrelevant information. However, in that study, the distractor category on a switch trial also represented the task-relevant target category from the previous trial. Thus, distractors were only intermittently task-irrelevant, such that switch-enhanced distractor memory could alternatively be because of remnant attention to the previously relevant stimuli, or "task-set inertia." Here we adjudicated between the open-gate and the task-set inertia accounts of switch-enhanced distractor memory by assessing incidental memory for distractors that were either intermittently or always task-irrelevant. While we replicated switch-enhanced distractor memory in the intermittently irrelevant distractor condition, this effect was reversed in the always-irrelevant distractor condition. These results speak against the open-gate account, and instead indicate that switch-enhanced distractor memory arises from task-set inertia, and will not be observed for truly task-irrelevant stimuli presented during switching.