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Different contours used in the experiment: (a) real luminance-contrast contours (solid, 75% coverage, and 50% coverage); (b) illusory contours of a Kanizsa square formed from solid “pacmen,” a Kanizsa square formed from “bull’s-eye pacmen,” and horizontally phase-shifted vertical lines; and (c) control conditions that define the shape of the square using eight dots or only the corner edges of the solid “pacmen.”
