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Patrick Spröte, Roland Fleming; Bites & bends: Interpreting the visual meaning of concavities. Journal of Vision 2013;13(9):69. doi: https://doi.org/10.1167/13.9.69.
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© ARVO (1962-2015); The Authors (2016-present)
When we observe objects, we not only infer local 3D-surface properties like depths or curvatures, but we can also make judgments about the generative processes that formed the shape. In many cases, we can decompose the perceived shape into two distinct contributors – the original shape and a transformation subsequently applied to it. For example, a croissant’s concavity is perceived to be the result of a ‘bending transformation’ applied to a piece of dough, whereas the concavity in a bitten cookie is interpreted as due to an excision process in which a portion of the cookie has been removed. Although similar in shape, the visual system assigns different causal origins to the concavities of the cookie and the croissant. This in turn can have substantial effects on the perceived symmetry axis of the object. How the visual system interprets concavities therefore plays an important role in the perceptual organization of shape. We investigated factors that influence the ‘visual meaning’ of concavities in shapes and thereby the perceived causality. First, we used an asymmetric matching task to test whether subjects could identify bending transformations applied to arbitrary shapes. Subjects indicated how strongly they perceived a test shape to have been bent by applying the same perceived amount of bend to a different match shape. In a second experiment, we specifically determined which geometric factors distinguish perceived bites from bends. Subjects saw shapes that were either bent or bitten, along with a dot indicating some location in the shape. Subjects indicated the corresponding ‘symmetric point’ across the perceived axis of symmetry. Their judgments were used to evaluate perceived symmetries and causal processes that generated the concave shapes. By changing the regularities of shapes and the relationships between shapes and their concavities, we map out key geometrical factors affecting the visual meaning of concavities.
Meeting abstract presented at VSS 2013
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