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Brittney Hartle, Richard Murray, Laurie Wilcox; Stereoscopic surface interpolation from illusory contours. Journal of Vision 2016;16(12):1330. doi: 10.1167/16.12.1330.
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© ARVO (1962-2015); The Authors (2016-present)
Stereoscopic Kanizsa figures are an example of 3D illusory surface interpolation. In such stimuli, luminance-defined disparity signals exist only along the edges of the inducing elements, but observers reliably perceive a coherent surface in depth that extends across the central blank region. It is widely assumed that the 3D shape of the illusory surface is solely determined by the local disparity at the inducer edges, and then extrapolated to form a surface representation. Here we evaluate another alternative: that the illusory contours themselves also provide a disparity signal that contributes to the perceived 3D shape of the illusory surface. We measured stereoscopic depth magnitude percepts using a collection of Kanizsa figures with a wide range of inducer disparities. For comparison, we assessed similar figures with luminance-defined surfaces and a third condition where both illusory and luminance edges were present. Prior to testing, we measured individual diplopia thresholds for the inducer contours. Also, using a matching paradigm, we equated the perceived strength of the surfaces defined by luminance alone and by illusory contours. During testing, 3D Kanizsa figures were displayed in random order on a mirror stereoscope, and depth magnitude estimates were made using a touch sensitive sensor strip. We found that all 6 participants made depth magnitude estimates consistent with simple interpolation geometry, for all stimuli in the fused range; moreover, in this range of disparities, estimates for the illusory and luminance-defined stimuli were identical. At larger disparities, all observers reported increasing depth percepts with increasing disparity for the illusory figures. However, for half of our observers, depth estimates plateaued for the luminance-defined surfaces only. The correspondence between the suprathreshold depth percepts from luminance-defined and illusory Kanizsa surfaces, and the resilience of depth percepts from illusory figures suggests that in some cases binocular disparity can be extracted from illusory edges.
Meeting abstract presented at VSS 2016
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