Abstract
What determines when filtering irrelevant items is efficient? In 3 experiments we investigated perceptual load and individual differences in working memory (WM) capacity as determinants of filtering efficiency, using both behavioral and electrophysiological markers. Participants performed a visual search task that contained a target, neutral distractors and a flanker distractor. We used the contralateral delay activity (CDA) to monitor the amount of information being stored in visual WM. The assumption is that when filtering is efficient only the target should be processed in visual WM and irrelevant items could be filtered out early in processing, but as filtering becomes inefficient, more and more irrelevant items will be stored in visual WM. The results indicated that individual differences in WM capacity and perceptual load both independently influenced the filtering of irrelevant information from visual WM. Namely, filtering the flanker was efficient only under high perceptual load (as indicated by behavioral measures), but in both low and high perceptual load, individual differences in WM capacity correlated with filtering efficiency (as indicated by the CDA amplitude). Furthermore, the results identified the target search process as responsible for the inefficient filtering. Interestingly, facilitating the search process by presenting a spatial cue that signaled the target location made filtering more efficient in general, but high WM capacity individuals still benefited to a larger extent relative to low WM individuals.