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Stacey Aston, Maria Olkkonen, Anya Hurlbert; Memory Bias for Illumination Colour. Journal of Vision 2017;17(10):130. https://doi.org/10.1167/17.10.130.
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© ARVO (1962-2015); The Authors (2016-present)
Perceptual estimates of surface colour are biased in memory toward the mean of recently viewed colours (Olkkonen et al. 2014). Discrimination of global illumination colour is also biased, with discrimination thresholds enlarged for illumination changes opponent to the adaptation illumination; yet overall discrimination is poorest for bluish illumination changes (Aston et al. 2015). Does memory for illumination colour show the same central tendency as surface colour, and are biases for memory and discrimination linked? Participants (n=7) viewed an enclosed grey wall illuminated by tuneable multi-channel LED lamps. Following an initial 2-min adaptation period under D65 illumination, participants viewed on each trial: reference light (500 ms), top-up adaptation light (2000 ms), and test light (500 ms); then (under D65) responded by button press whether the test was "bluer or yellower" than the reference. Each of three trial blocks contained 5 reference illuminations covering a greenish-blue chromaticity range in equal perceptual steps; the three reference sets overlapped but had different means. All illuminations were the smoothest-possible metamers for the requested chromaticity. The point of subjective equality (PSE) for each reference in each block was determined by averaging the final reversals of two interleaved one-up, one-down staircases, one approaching the reference from yellower hues, the other bluer. PSEs were systematically biased towards the mean of each block (the same illumination was remembered as more yellow when all references were biased towards yellow, compared to when biased towards blue). The set of illuminations perceptually equal to each reference chromaticity, defined as all hues between the convergence points of the two staircases, are skewed towards bluer hues. While illumination colour memory shows the same bias towards recent stimuli as surface colour memory, there is an additional bias towards blue which may result from poorer discrimination or prior expectations for illumination colour.
Meeting abstract presented at VSS 2017
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