Grouping in a multi-target visual search task

T. D. Grandison, S. K. Hendel, Howard E Egeth

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Abstract

Purpose. Some theories of visual attention assume that when searching through a scene for a target, people first segment the visual scene into groups that contain items with similar features. Search then proceeds group by group rather than item by item. We investigated whether subjects are quicker to process two targets when the targets are in the same versus different groups. Furthermore we examined factors that influence group membership for visual search. Methods. Subjects searched for conjunctive targets (purple Xs and Ts) among an array of distractors (purple Os, green Xs and Ts). Subjects made a speeded response based on the number of targets present in a given display. Each display contained either one or two targets. On critical trials, the items immediately surrounding each target had the same color as the target, thus forming two groups. The type of items that appeared between these two target groups (intervening items) was manipulated. In experiment one the intervening items appeared either in the target color or in a different color. When the intervening items appeared in the same color as the targets both targets could be grouped together, however when the intervening items appeared in a different color, the targets were segmented into separate groups. In the second experiment the intervening space could contain similar items, dissimilar items or could be blank. Results. In the first experiment subjects were faster to respond to two targets when the intervening items were the target color than when the intervening items appeared in different color. In the second experiment subjects were again fastest to respond when the intervening items had the target color, slower when the intervening space was blank, and slowest when the intervening items had a nontarget color. Conclusion. Grouping by target features can speed visual search. At least two factors influence whether search will proceed through two small groups or one larger group. Relative to when blank space appears between the two groups, the presence of similar intervening items facilitates search, while the presence of dissimilar items slows search.

Original languageEnglish (US)
JournalInvestigative Ophthalmology and Visual Science
Volume37
Issue number3
StatePublished - Feb 15 1996

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  • Ophthalmology

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Grouping in a multi-target visual search task. / Grandison, T. D.; Hendel, S. K.; Egeth, Howard E.

In: Investigative Ophthalmology and Visual Science, Vol. 37, No. 3, 15.02.1996.

Research output: Contribution to journalArticle

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N2 - Purpose. Some theories of visual attention assume that when searching through a scene for a target, people first segment the visual scene into groups that contain items with similar features. Search then proceeds group by group rather than item by item. We investigated whether subjects are quicker to process two targets when the targets are in the same versus different groups. Furthermore we examined factors that influence group membership for visual search. Methods. Subjects searched for conjunctive targets (purple Xs and Ts) among an array of distractors (purple Os, green Xs and Ts). Subjects made a speeded response based on the number of targets present in a given display. Each display contained either one or two targets. On critical trials, the items immediately surrounding each target had the same color as the target, thus forming two groups. The type of items that appeared between these two target groups (intervening items) was manipulated. In experiment one the intervening items appeared either in the target color or in a different color. When the intervening items appeared in the same color as the targets both targets could be grouped together, however when the intervening items appeared in a different color, the targets were segmented into separate groups. In the second experiment the intervening space could contain similar items, dissimilar items or could be blank. Results. In the first experiment subjects were faster to respond to two targets when the intervening items were the target color than when the intervening items appeared in different color. In the second experiment subjects were again fastest to respond when the intervening items had the target color, slower when the intervening space was blank, and slowest when the intervening items had a nontarget color. Conclusion. Grouping by target features can speed visual search. At least two factors influence whether search will proceed through two small groups or one larger group. Relative to when blank space appears between the two groups, the presence of similar intervening items facilitates search, while the presence of dissimilar items slows search.

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