The visual system prioritizes locations near corners of surfaces (not just locations near a corner)
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The visual system prioritizes locations near corners of surfaces (not just locations near a corner) Marco Bertamini & Mai Helmy & Daniel Bates
# Psychonomic Society, Inc. 2013
Abstract When a new visual object appears, attention is directed toward it. However, some locations along the outline of the new object may receive more resources, perhaps as a consequence of their relative importance in describing its shape. Evidence suggests that corners receive enhanced processing, relative to the straight edges of an outline (corner enhancement effect). Using a technique similar to that in an original study in which observers had to respond to a probe presented near a contour (Cole et al. in Journal of Experimental Psychology: Human Perception and Performance 27:1356–1368, 2001), we confirmed this effect. When figure–ground relations were manipulated using shaded surfaces (Exps. 1 and 2) and stereograms (Exps. 3 and 4), two novel aspects of the phenomenon emerged: We found no difference between corners perceived as being convex or concave, and we found that the enhancement was stronger when the probe was perceived as being a feature of the surface that the corner belonged to. Therefore, the enhancement is not based on spatial aspects of the regions in the image, but critically depends on figure–ground stratification, supporting the link between the prioritization of corners and the representation of surface layout. Keywords Figure–ground . Convexity . Contour curvature . Corner enhancement effect It is known that the appearance of a new object captures visual attention (Jonides, 1981; Posner, 1980; Watson & M. Bertamini (*) : D. Bates Department of Psychological Sciences, University of Liverpool, Eleanor Rathbone Building, Liverpool L69 7ZA, UK e-mail: [email protected] M. Helmy Department of Psychology, Menoufia University, Shibin El Kom, Egypt
Humphreys, 1997), that onsets are more salient than offsets (Cole, Kentridge, Gellatly, & Heywood, 2003), and that the onset effect is not entirely due to local transients (Cole & Kuhn, 2009, 2010; Enns, Austen, Di Lollo, Rauschenberger, & Yantis, 2001). But also there is evidence that not all locations along the outline of the new object attract attention or resources equally. For the human visual system, edge information provides information about boundaries, which in turn are informative about solid shape (Koenderink, 1984; Mach, 1959). With respect to curvature along the contour, regions with high curvatures may be treated differently because they carry more information than do low-curvature regions (Attneave, 1954). Regions with extrema (minima and maxima) of curvature are also informative about part structure (Hoffman & Richards, 1984). Therefore, testing the relative saliences of different locations along an outline contributes to understanding how object recognition works. The greater salience of corners would support a key role of locations with high curvature in processing shape. Specifically, convex corners may be more salient, in agreement with better perf
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