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UBC Theses and Dissertations

Search for orientation in multiple media : which comes first, the color or the edge Wig, Patrick Shawn


Search for combinations of orientation, shape, color, direction of motion, and binocular disparity should be slower than search for any one of them in isolation. Recent results showing fast search for certain combinations of these features havef prompted theorists to suggest that features like orientation may be represented separately depending on the color, texture, or other medium that distinguishes them from the background (Cavanagh, Arguin, & Treisman, 1990; Treisman, 1988). Enns and Wig (1989) provide evidence that edge orientation is represented independently from the medium in which it is carried, at least for texture and luminance. This thesis examined the effects of multiple colors on search for oriented edges. Experiment 1 compared edges defined by different equiluminant colors (i.e., colors of equal apparent brightness), and Experiment 2 compared color and luminance defined edges. Subjects were able to search for a vertical edge defined by either color in parallel. They could also search for a vertical edge of randomly alternating color among mixed color horizontal distractors without interference. However, search rates became serial if the distractors included vertical edges of another color. This pattern of results was duplicated in Experiment 2. The presence of this Stroop interference is strong evidence for color and luminance independent representations for orientation in visual search.

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