Early computation of part structure: Evidence from visual search

Abstract

The visual system represents object shapes in terms of intermediate-level parts. The minima rule proposes that the visual system uses negative minima of curvature to define boundaries between parts. We used visual search to test whether part structures consistent with the minima rule are computed preattentively-or at least, rapidly and early in visual processing. The results of Experiments 1 and 2 showed that whereas the search for a non-minima-segmentedshape is fast and efficient among minimasegmented shapes, the reverse search is slow and inefficient. This asymmetry is expected if parsing at negative minima occurs obligatorily. The results of Experiments 3 and 4 showed that although both minima-and non-minima-segmentedshapes pop out among unsegmented shapes, the search for minimasegmented shapes is significantly slower. Together, these results demonstrate that the visual system segments shapes into parts, using negative minima of curvature, and that it does so rapidly in early stages of visual processing.

Visual Endurance and Auditory Perdurance

“…Nevertheless, when visually perceiving a red square we do not experience it as having these various potential parts unless some additional borders are added, which allow us to distinguish them. This intuition is in accordance with the main psychological models of visual parts perception which claim that fragments of objects are recognized as parts if they are separated by edges or if the outline of a figure creates points of convexity (like in a case of an hour-glass shape, Hoffman and Richards 1984;Xu and Singh 2002). In other words, relying on the minimal notion of VO, proper spatial parts of VO are those of their spatial fragments that themselves are VO.…”

“…Investigations concerning part-structure of VO should formulate the notion of perceptual parts relaying on how human vision divides objects into parts and not on how we can conceptualize the structure of objects using some postperceptual abilities. From this perspective, the liberal notion of perceptual parts is not consistent with the major psychological models of part perception which, relying on behavioural data, claim that part-structure is determined by the represented edges (e.g., Hoffman and Richards 1984;Xu and Singh 2002). In addition, such a broader notion does not fit well with models of visual attention.…”

Processing convexity and concavity along a 2-D contour: figure–ground, structural shape, and attention

“…Although both singularities involve regions of high curvature changes, they differ in that concave (m−) deletions create gaps that concur with spontaneous segmentation. Xu and Singh (2002) have made a very similar argument to explain their visual search results. When a silhouette is segmented by introducing a cut, this segmentation changes the perception of that object drastically, making it more salient when placed among silhouettes without a cut, but only if this cut does not correspond to concave cusps.…”

Part-Based Representations of Visual Shape and Implications for Visual Cognition

“…We show how the minima rule and part salience allow us to refine and extend figural conditions for the perception of transparency proposed by the Gestalt psychologists Metelli and Kanizsa (Singh & Hoffman, 1998). We review results of visual-search experiments that demonstrate that part structures consistent with the minima rule are computed rapidly and early in visual processing (Xu & Singh, 2001). And, we review results of attentional-cueing experiments that reveal that part structure and part salience modulate the allocation of visual attention to multi-part objects (Singh & Scholl, 2000).…”

“…From an empirical perspective, recent evidence suggests that parts are computed quickly, automatically, and in parallel over the visual field (Baylis & Driver, 1994;95a;95b;Hulleman, te Winkel, & Boselie, 2000;Wolfe & Bennett, 1997, Xu & Singh, 2001. With ambiguous shapes flashed for just 50 ms and followed by a mask, parts affect the perception of figure and ground representational formats may take place later in visual processing, these are likely to be influenced by the early formatting of shapes into parts.…”