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UBC Theses and Dissertations

The role of inter-item symmetry in visual search for shape Roggeveen, Alexa B.

Abstract

Does visual search involve a serial inspection of individual display items (Feature Integration Theory) or are there perceptual processes that group and segregate items from one another prior to their consideration as a possible target (Resemblance Theory)? For example, for targets defined by motion and shape, there is strong support for grouping processes (Kingstone & Bischof, 1999). The present study looked for evidence of grouping based on shape symmetry. Participants searched for target shapes among distractors that were mirror images over either the vertical or horizontal axis. The results indicated: (1) symmetry between items strongly influences search, (2) search was influenced by grouping among target and distractor items in the display, and (3) symmetry was influential in between-distractor grouping only when displays were 'cortically magnified' in order to equate the salience of symmetry across display locations. These results confirm that static shapes are grouped on the basis of their symmetrical similarity to one another, prior to their explicit identification as being either 'target' or 'distractor'. Thus, as with items in motion, static items are grouped and segregated prior to consideration as a target, in accordance with Resemblance Theory.

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