The Role of Illumination Level in the Strength of Subjective Contours
Although they are not physically present in the field of view, subjective or illusory contours are nonetheless psychologically meaningful, and they also share many of the same functional properties of real contours. Geometric illusions and reversible figures can be produced with subjective contours (Bradley & Dumais, 1975; Bradley & Petry, 1977; Gregory, 1972; Meyer & Garges, 1979); these contours can be placed in apparent motion (von Grünau, 1979); they can be enhanced by kinetic depth information (Bradley & Lee, 1982); they can serve as targets or masks in visual masking experiments (Reynolds, 1981; Weisstein, Matthews, & Berbaum, 1974), and they are susceptible to motion, tilt, and color—contingent aftereffects (Meyer & Phillips, 1980; Smith & Over, 1975, 1979). In addition, like real contours, subjective contours can serve as landmarks aiding in the localization of elements in visual space (Pomerantz, Goldberg, Golder, & Tetewsky, 1981).
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