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Naseem Al-Aidroos, Stephen M. Emrich, Jay Pratt, Susanne Ferber; Prioritization of new objects during visual search is limited by the capacity of visual short-term memory. Journal of Vision 2007;7(9):661. doi: 10.1167/7.9.661.
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© ARVO (1962-2015); The Authors (2016-present)
When new items are presented in a visual scene, these items are typically given attentional priority over old ones. While some theories posit that this prioritization of new items is related only to the automatic capture of attention by luminance changes, other evidence suggests that the visual system may mark or inhibit the old items, thereby giving these old items less priority. If the visual system can in fact inhibit old items, the ability to do so may be limited by visual memory capacity (about 4 items). Accordingly, we tested whether the number of old items in a visual scene that could be given reduced priority was limited by the capacity of visual short-term memory (VSTM). We presented participants with a visual-search task in which 0–7 distractors were previewed for one second prior to the presentation of the target. The results demonstrate that the search time is not affected by the number of old items when the old items can be held in VSTM (i.e., when there are fewer than 4 old items). Furthermore, this prioritization occurs even in the absence of luminance changes. We also demonstrate that when the number of old items is greater than memory capacity, performance is benefited by the preview of old items, as search times are equivalent to the removal of roughly 4 distractors. These results provide compelling evidence that the number of old items that can be given reduced attentional priority relative to new items is limited by the capacity of visual short-term memory, suggesting a role for VSTM in the prioritization of new items in a visual scene.
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