Academic journal article Attention, Perception and Psychophysics

Perceiving Surface Properties

Academic journal article Attention, Perception and Psychophysics

Perceiving Surface Properties

Article excerpt

VISUAL PERCEPTION

ANDERSON & KIM (2009). J Vis, 9(11), Art. 10.

Human vision is able to make subtle judgments about natural surfaces. For example, we easily judge whether a rock face is likely to hold our boot without slipping as we hike, or whether a sponge is moist or dry. A lively debate has recently sprung up over the question of how we make such judgments; in general, the problem of determining the properties (e.g., the albedo, reflectance, and depth variations) of a surface from the pattern of light it reflects is very complicated. In 2007, Motoyoshi et al. (Nature 447:206) presented evidence that vision may not extract these properties at all, but instead may use surprising computational "shortcuts" in estimating them. Specifically, the researchers used photographs of bumpy, materially homogeneous surfaces and showed that if one fixes the mean luminance of such an image, the perceived albedo of the surface is sensitively controlled by the skew of the image's gray-level histogram. Positive skew makes the surface look glossy; negative skew makes it look matte. The spatial pattern of light reflected by the surface is irrelevant to this statistic: You can scramble the pixels in the image without altering the skew of the histogram, so if skew really does control our visual judgments of surface albedo, this is a serious shortcut indeed. …

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