Maintaining rejected distractors in working memory during visual search depends on search stimuli: Evidence from contral
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Maintaining rejected distractors in working memory during visual search depends on search stimuli: Evidence from contralateral delay activity Lauren H. Williams 1 & Trafton Drew 1
# The Psychonomic Society, Inc. 2020
Abstract The presence of memory for rejected distractors during visual search has been heavily debated in the literature and has proven challenging to investigate behaviorally. In this research, we used an electrophysiological index of working memory (contralateral delay activity) to passively measure working memory activity during visual search. Participants were asked to indicate whether a novel target was present or absent in a lateralized search array with three visual set sizes (2, 4, or 6). If rejected distractors are maintained in working memory during search, working memory activity should increase with the number of distractors that need to be evaluated. Therefore, we predicted the amplitude of the contralateral delay activity would be larger for target-absent trials and would increase with visual set size until WM capacity was reached. In Experiment 1, we found no evidence for distractor maintenance in working memory during search for real-world stimuli. In Experiment 2, we found partial evidence in support of distractor maintenance during search for stimuli with high target/distractor similarity. In both experiments, working memory capacity did not appear to be a limiting factor during visual search. These results suggest the role of working memory during search may depend on the visual search task in question. Maintaining distractors in working memory appears to be unnecessary during search for realistic stimuli. However, there appears to be a limited role for distractor maintenance during search for artificial stimuli with a high degree of feature overlap. Keywords Visual search . Visual working memory . Electrophysiology
Visual search is an everyday part of the human experience. Most readers have likely had the frustrating experience of searching seemingly everywhere without success for their keys before leaving the house. In these situations, it would be beneficial to be able to keep track of where you have already searched to prevent multiple evaluations of the same object. In fact, most models of visual search assume that each distractor is evaluated only once per search, which implies a strong role for memory in visual search (Treisman & Gelade, 1980; Wolfe, Cave, & Franzel, 1989; though see Wolfe, 2007). However, behavioral evidence on this topic has been surprisingly mixed, and it remains unclear if rejected distractors are reliably maintained during visual search.
* Lauren H. Williams [email protected] 1
Department of Psychology, University of Utah, Salt Lake City, UT, USA
The strongest candidate for a mechanism that biases attention toward new locations during search is inhibition of return, or IOR (Klein, 1988), which refers to the delay in response time (RT) toward probes in recently attended locations relative to novel locations (Posner & Cohen, 1984). This pheno
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