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Eric Altschuler, Abigail Huang, Alice Hon, Jessica Goris-Rosales, Chris Tyler; Simultaneous color contrast, afterimages and metameric intransitivity: Novel effects and explanation of previously enigmatic results. Journal of Vision 2008;8(6):562. doi: 10.1167/8.6.562.
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© ARVO (1962-2015); The Authors (2016-present)
While many features of simultaneous color (and brightness) contrast (SCC) and negative and positive afterimages (NAI, PAI) have been known for half a millennium, even simply stated questions remain unexplained (e.g., Anstis, Rogers & Henry 1978). We discuss novel and underappreciated properties and effects of SCC, PAI and NAI, and implications for understanding neural mechanisms underlying these phenomena. In particular, we develop displays of test patches which look the same but have grossly different afterimages, and, conversely, which look very different but have identical afterimages (metameric intransitivity). These effects are based on the findings that SCC has a time course, that the PAI and NAI can be visible simultaneously and that these afterimages can obscure results of vision experiments. When at least one background is white or near-white it is not possible to match the test patch colors merely by adjusting their brightness, possibly due to slightly unequal number of color receptors or associated higher order neurons. We emphasize the underappreciated effect that SCC does not cause the test patch to take on the surround's complementary color, rather the common color is “pulled out” from the surround and test patch. We derive semi-quantitative curves for the strengths of SCC, NAI and PAI and use these to explain previously enigmatic results (ARH, 1978) and produce the dissociations between image and afterimage metamers. Furthermore, we show that the Munker color effect can be obtained solely from grouping effects—and does not depend on geometry—of a group of colored discs on a different color background inducing a change in the color of a group of test discs. We use this grouping version to clarify the effect of the inducing stimuli in the Munker, White and inverse White effects, leading to the explanation of a novel inverse Benary effect.
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