Selection for visual short-term memory (vstm) provides a basis for many cognitive functions. Saccadic eye movements sway this selection in favor of stimuli previously seen at locations congruent with their target. In three experiments, we provide converging evidence that this saccadic selection is implemented as a fundamental, inevitable selection process, rather than a top-down strategy. In particular, benefits for congruent over incongruent items were largely constant across set sizes ranging from two to eight items (Experiment 1), showing that saccadic selection imposes priorities on vstm irrespective of memory load and is effective even when only few representations need to be maintained. Moreover, a decrement in performance for incongruent items occurred reliably, whether the congruent location contained a task-relevant item or an irrelevant noise patch (Experiment 2). Finally, saccadic selection was immune to a strong manipulation of the observer's attentional priorities (Experiment 3). Given the prevalence of saccades in natural vision, our results demonstrate a fundamental and ecologically relevant selection mechanism for vstm: Saccades systematically eliminate information seen at non-target locations, while information at the saccade target remains available to recall. This simple heuristic is effective in the absence of informative cues and may incapacitate voluntary selection mechanisms that are incongruent with ongoing movement plans.
In the present study, we observed that saccadic selection occurred in vstm, largely independently of memory load, irrespective of the task relevance of the stimulus seen at the saccade target, and irrespective of how likely it is that memory is probed at the saccade goal. Saccades therefore selectively protect memory at locations congruent with their target, and eliminate information at nontarget locations without compromise. Using this powerful and ecologically relevant selection mechanism, the visual system is equipped to make rapid choices in the absence of informative cues, deciding what to remember and what to forget.