Effects of specular highlights on perceived surface convexity

Adams, Wendy J. and Elder, James (2014) Effects of specular highlights on perceived surface convexity PLoS Computational Biology, 10, (5), pp. 1-13. (doi:10.1371/journal.pcbi.1003576). (PMID:24811069).


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Shading is known to produce vivid perceptions of depth. However, the influence of specular highlights on perceived shape is unclear: some studies have shown that highlights improve quantitative shape perception while others have shown no effect. Here we ask how specular highlights combine with Lambertian shading cues to determine perceived surface curvature, and to what degree this is based upon a coherent model of the scene geometry. Observers viewed ambiguous convex/concave shaded surfaces, with or without highlights. We show that the presence/absence of specular highlights has an effect on qualitative shape, their presence biasing perception toward convex interpretations of ambiguous shaded objects. We also find that the alignment of a highlight with the Lambertian shading modulates its effect on perceived shape; misaligned highlights are less likely to be perceived as specularities, and thus have less effect on shape perception. Increasing the depth of the surface or the slant of the illuminant also modulated the effect of the highlight, increasing the bias toward convexity. The effect of highlights on perceived shape can be understood probabilistically in terms of scene geometry: for deeper objects and/or highly slanted illuminants, highlights will occur on convex but not concave surfaces, due to occlusion of the illuminant. Given uncertainty about the exact object depth and illuminant direction, the presence of a highlight increases the probability that the surface is convex

Item Type: Article
Digital Object Identifier (DOI): doi:10.1371/journal.pcbi.1003576
ISSNs: 1553-734X (print)
Subjects: B Philosophy. Psychology. Religion > BF Psychology
R Medicine > RC Internal medicine > RC0321 Neuroscience. Biological psychiatry. Neuropsychiatry
ePrint ID: 364889
Date :
Date Event
4 March 2014Accepted/In Press
8 May 2014Published
Date Deposited: 16 May 2014 07:44
Last Modified: 17 Apr 2017 13:49
Further Information:Google Scholar
URI: http://eprints.soton.ac.uk/id/eprint/364889

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