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Dhanraj Vishwanath, Paul Hibbard; Quality in depth perception: the plastic effect. Journal of Vision 2010;10(7):42. doi: 10.1167/10.7.42.
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© ARVO (1962-2015); The Authors (2016-present)
The qualitative superiority of depth perception under binocular viewing–the plastic effect (Ames, 1925; Schlosberg, 1941)–is generally regarded as an epiphenomenon (a quale) linked to binocular visual processing. This view finds some support in perceptual reports of depth quality when binocular vision is recovered in late adulthood (Barry, 2009). However, such qualitative vividness is also experienced under monocular and synoptic viewing of pictures (Ames, 1925; Schlosberg, 1941; Koenderink, 1998), suggesting that the story may be more complicated. We had naïve observers make qualitative judgments of depth and other perceptual attributes for real objects and pictorial images under a range of viewing conditions. Under monocular-aperture viewing, observers report the same effects as in binocular viewing of real scenes, saying that things “stick out”, appear “more real and 3-dimensional”, and that “the space between objects can be perceived”. Observers also reported a heightened perception of material qualities (e.g. glossiness, color saturation) as well as a sharpening of the image. Curiously, such related effects have also been reported by individuals who have recovered stereopsis (Barry, 2009). More importantly, observers reported changes in perceived distance or scale consistent with an accommodation-based distance effect or micropsia in pictorial space. Surprisingly, observers did not report changes in perceived shape in these conditions. Parallel effects were observed for binocular viewing of pictorial images with simulated blur gradients; observers also report a heightened plastic effect accompanying changes in perceived distance. These observations neither support the idea that the plastic effect is a byproduct of binocular processing nor that it is determined by relative conflict among depth cues. Rather, they appear more consistent with the theory that the plastic effect is the perceptual presentation of the reliability of the brain's estimates of egocentrically scaled depth, which depend on the availability and reliability of distance information.
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