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Steven Buck; “The Snake” equally modulates both brown and brightness. Journal of Vision 2019;19(8):35. doi: https://doi.org/10.1167/19.8.35.
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© ARVO (1962-2015); The Authors (2016-present)
Adelson’s Snake background is famous for producing dramatic brightness-induction effects. To explore the relation of brown induction to brightness induction, we measured both brown boundaries (the luminance at which brown completely replaces yellow) and brightness matches on Snake and Anti-Snake backgrounds. Effects of the backgrounds were quantified by the ratio of luminances (modulation) of brightness matches or brown boundaries on the two bands of each background.
The results show that brightness matches and brown boundaries were equally modulated by the simultaneous luminance contrasts present in the Anti-Snake and shared by the Snake. In addition, both brightness matches and brown boundaries were further modulated in equal measure by the constellation of stimulus features unique to the Snake, over and above the effects of simultaneous contrast. The perceptual processes by which the Snake produces its modulations have long been debated but the present results show that they influence both brightness and brown inductions equally.
It remains a mystery why brown progressively replaces yellow as stimuli darken but the present results are consistent with the hypothesis that the degree of brownness is directly determined by stimulus brightness.
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