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Perception of three-dimensional shape influences colour perception through mutual illumination


Objects in the natural world possess different visual attributes, including shape, colour, surface texture and motion. Previous perceptual studies have assumed that the brain analyses the colour of a surface independently of its three-dimensional shape and viewing geometry1,2, although there are neural connections between colour and two-dimensional form processing early in the visual pathway3,4. Here we show that colour perception is strongly influenced by three-dimensional shape perception in a novel, chromatic version of the Mach Card—a concave folded card with one side made of magenta paper and the other of white paper. The light reflected from the magenta paper casts a pinkish glow on the white side. The perceived colour of the white side changes from pale pink to deep magenta when the perceived shape of the card flips from concave to convex. The effect demonstrates that the human visual system incorporates knowledge of mutual illumination—the physics of light reflection between surfaces—at an early stage in colour perception.

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Figure 1: The experimental stimulus.
Figure 2: Average (u′,v′) coordinates of the matches selected for the white side of the card.
Figure 3: Observed matches and model predictions.


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We thank J. Artigas Verde for use of the spectroradiometer, the late P. Callaghan for construction of the pseudoscope, and A. D. Logvinenko for technical information. The research was supported by the Wellcome Trust (A.C.H. and M.G.B.) and by the National Science Foundation (D.K.). M.G.B. was supported by British Federation of Women Graduates, Ian Karten Charitable Trust, an Overseas Research Student Award and the University of Newcastle. Thanks to A. Rees, M. Ridley and P. Schrater for helpful comments on earlier drafts of the manuscript.

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Correspondence to A. C. Hurlbert.

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Bloj, M., Kersten, D. & Hurlbert, A. Perception of three-dimensional shape influences colour perception through mutual illumination. Nature 402, 877–879 (1999).

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