Internal selective attention is delayed by competition between endogenous and exogenous factors.

External selective attention is mediated by competition between endogenous (goal-driven) and exogenous (stimulus-driven) factors, with the balance of competition determining which stimuli are selected. Occasionally, exogenous factors "win" this competition and drive the selection of task-irrelevant stimuli. Endogenous and exogenous selection mechanisms may also compete to control the selection of internal representations (e.g., those stored in working memory), but how this competition manifests and whether it is resolved in the same way as external attention is unknown. Here, we leveraged the high temporal resolution of human EEG to determine how competition between endogenous and exogenous factors influences the selection of internal representations. Unlike external attention, competition between endogenous and exogenous factors did not prompt the selection of task-irrelevant working memory content. Instead, it simply delayed the endogenous selection of task-relevant working memory content by several hundred milliseconds. Thus, competition between endogenous and exogenous factors influences internal selective attention, but in a different way than external selective attention.