1997 volume 26(11) pages 1423 – 1430
doi:10.1068/p261423

Cite as:
Wachtler T, Wehrhahn C, 1997, "The Craik - O'Brien - Cornsweet illusion in colour: Quantitative characterisation and comparison with luminance" Perception 26(11) 1423 – 1430
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The Craik - O'Brien - Cornsweet illusion in colour: Quantitative characterisation and comparison with luminance

Thomas Wachtler, Christian Wehrhahn

Received 29 May 1996, final revision 20 August 1997

Abstract. The strength of the Craik - O'Brien - Cornsweet illusion was measured for different values of spatial and temporal stimulus parameters, in the traditional achromatic version, and in an isoluminant colour version. It was found that the illusion is much weaker with isoluminantcolour stimuli than with achromatic luminance stimuli. The illusion depends on the spatial parameters of the stimulus in a way that yields an approximate scale invariance: The strength of the illusion is similar for different stimulus sizes, as long as the ratio of the width of the transition region around the edge, where luminance or colour change, to the total stimulus widthis preserved. In both the achromatic and the chromatic case, the strength of the illusion decreases with increasing presentation time. The similarity of the differences between brightness andcolour effects on one hand and the differences in sensitivity for colour and luminance changes in humans on the other suggests that a lack of gradient detection underlies the Craik - O'Brien - Cornsweet illusion.

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