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Specular highlights improve colour constancy when other cues are weakened.

Wedge-Roberts, Rebecca and Aston, Stacey and Beierholm, Ulrik and Kentridge, Robert and Hurlbert, Anya and Nardini, Marko and Olkkonen, Maria (2020) 'Specular highlights improve colour constancy when other cues are weakened.', Journal of vision., 20 (12). pp. 1-22.


Previous studies suggest that to achieve color constancy, the human visual system makes use of multiple cues, including a priori assumptions about the illumination (“daylight priors”). Specular highlights have been proposed to aid constancy, but the evidence for their usefulness is mixed. Here, we used a novel cue-combination approach to test whether the presence of specular highlights or the validity of a daylight prior improves illumination chromaticity estimates, inferred from achromatic settings, to determine whether and under which conditions either cue contributes to color constancy. Observers made achromatic settings within three-dimensional rendered scenes containing matte or glossy shapes, illuminated by either daylight or nondaylight illuminations. We assessed both the variability of these settings and their accuracy, in terms of the standard color constancy index (CCI). When a spectrally uniform background was present, neither CCIs nor variability improved with specular highlights or daylight illuminants (Experiment 1). When a Mondrian background was introduced, CCIs decreased overall but were higher for scenes containing glossy, as opposed to matte, shapes (Experiments 2 and 3). There was no overall reduction in variability of settings and no benefit for scenes illuminated by daylights. Taken together, these results suggest that the human visual system indeed uses specular highlights to improve color constancy but only when other cues, such as from the local surround, are weakened.

Item Type:Article
Full text:Publisher-imposed embargo
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Publisher statement:Copyright 2020 The Authors. This work is licensed under a Creative Commons Attribution 4.0 International License.
Date accepted:07 September 2020
Date deposited:21 October 2020
Date of first online publication:10 November 2020
Date first made open access:20 November 2020

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