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Hengqing Chu, Brian Levinthal, Alejandro Lleras; Semantic marking in preview search. Journal of Vision 2008;8(6):1114. doi: 10.1167/8.6.1114.
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In visual search tasks, if a subset of the search items (without the target) is presented at least 400ms before the full set is in view, visual search efficiency is improved dramatically, almost as if only the second set of items had been searched. This phenomenon is known as visual marking, and is thought to involve inhibitory-tagging of old items. This study investigates whether this inhibitory-tagging can be semantically mediated. Subjects searched for a sideway T among Ls of identical color and regular Ts and upside-down Ts of a second color, and reported the orientation of the target T. In addition, to eliminate the contribution of bottom-up attentional capture by the onset of the second set of items, we included a 200ms blank display between the initial preview and the final search display. In Experiment 1, we tested four conditions: feature search (T amongst Ls), conjunction search (T amongst full set of distractors) and two preview conditions. In the control-preview condition, all distractor Ts were presented first, before the full display appeared. In the semantic-preview condition, we simply showed the words “BLUE” or “RED” at fixation (and in blank ink). As in the control-preview condition, the color word indicated the color of the distractor Ts in the final display. Our results showed an identical preview benefit in both preview conditions, indicating that semantic knowledge of the color of a subset of distractors was sufficient for “marking” these items in the full display. In Experiment 2, we tested whether this “semantic marking” could be used to prioritize the target color. Surprisingly, search efficiency was identical in the control and “target-marking” preview conditions. These two experiments strongly suggest that advance knowledge of either the distractor color or the target color is sufficient to produce preview benefits.
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