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Delwin Lindsey, Angela Brown; Desaturated color scaling does not depend on color context: an MLDS experiment. Journal of Vision 2010;10(7):404. doi: 10.1167/10.7.404.
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© ARVO (1962-2015); The Authors (2016-present)
Previous work showed that visual search for desaturated targets among heterogeneous arrays of white and saturated distractors, of the same hue as their target, is governed by low-level color-opponent responses (Kuzmova, VSS, 2008). Is this a local effect, involving mechanisms that directly process the color signals arising from the targets themselves? Or is it more complex, perhaps involving relatively global perceptual processes that are governed by their low-level inputs? To investigate this question, we asked whether the distractors in the original search experiment influenced the color appearance of the targets. We presented reddish test stimuli of varying saturation and lightness (including the target that was found fastest in the search experiment) and a similar range of tritan-purplish stimuli (including the slowest target), in three color-context conditions: (1) a mixed “distractor” set of 60 red and white squares, (2) a similar set of purple and white squares, and (3) no squares (just the dark surrounding field). We assessed the color appearance of test stimuli, as a function of saturation, using Maximum Likelihood Difference Scaling. Test stimuli fell at equal δE intervals, along two lines in CIELAB, passing through red (10 cd/m2) and white (50 cd/m2), and white and purple (9 cd/m2), respectively. Three subjects (two naïve) viewed randomly-selected quadruples of 1-deg. colored squares displayed in the center of a color CRT. On each trial, subjects judged whether the top or the bottom pair of test stimuli had the larger color difference. We found no systematic difference in scaled hue across the three color-context conditions. Thus, the distractors in the original search experiment apparently did not influence the color appearance of the target stimuli. This result reinforces our previous conclusion that visual search engages local, low-level color opponent channels when desaturated targets are embedded in heterogeneous distractor arrays.
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