Abstract: . . .  profile, suggesting that spatial interactions across the edge are important. The evidence is that the effect is abolished by a thin black ring round the edge of the patch (Whittle, 1992). However, a black ring makes no difference at all to the chromatic version of the effect (Ovenston, 1998). This suggests, though not conclusively, that spatial neural interactions may be more important for brightness than colour. It should be noted that even if contrast colours are produced predominantly by temporal . . .
. . .  experimental psychology Page 1 Version of 2.5.99. CONTRAST COLOURS Paul Whittle Department of Experimental Psychology , Cambridge University pw109@cam.ac.uk ‘So the judgements that we hold about the colours of objects seem not to depend uniquely on the absolute nature of the rays of light that . . .
. . .  same, so that the relative stimulation of the three cone classes is unchanged. Therefore the three cone contrasts are all the same, and equal to the luminance contrast. So according to the cone contrast rule it should match a patch of the same luminance contrast  . . .
. . .  adaptation or whatever, encodes the proximal stimulus, not the distal, and will therefore be indifferent to whether the neighbouring colour is a surface or an illumination colour. Further complications: colour is not single-valued The phenomenon of contrast colours has surprising implications. It is easy to say ‘situations under which colour is determined by contrast’, but if such situations are common in everyday life they radically upset common beliefs about colour. Take a large bright red field. Make . . .
. . .  experimental psychology Page 1 Version of 2.5.99. CONTRAST COLOURS Paul Whittle Department of Experimental Psychology , Cambridge University pw109@cam.ac.uk ‘So the judgements that we hold about the colours of objects seem not to depend uniquely on the absolute nature of the rays of light that paint the picture of objects . . .
. . .  For constrast brightnesses this effect is markedly dependent on the exact edge profile, suggesting that spatial interactions across the edge are important. The evidence is that the effect is abolished by a thin black ring round the edge of the patch (Whittle, 1992). However, a black ring makes no difference at all to the chromatic version of the effect (Ovenston, 1998). This suggests, though not conclusively, that spatial neural interactions may be more important for brightness than colour. It should . . .
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