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Archive for 23/06/2010

Why colour?

Mark Changizi wrote a posting in PsychologyToday about colour qualia (here). He has some good thoughts about colour that stem from his research.

How do we know that your ‘red’ looks the same as my ‘red’? For all we know, your ‘red’ looks like my ‘blue’. In fact, for all we know your ‘red’ looks nothing like any of my colors at all! If colors are just internal labels, then as long as everything gets labeled, why should your brain and my brain use the same labels?…

However, I would suggest that most discussions of rearrangements of color qualia severely underestimate how much structure comes along with our color perceptions. Once one more fully appreciates the degree to which color qualia are linked to one another and to non-color qualia, it becomes much less plausible to single color qualia out as especially permutable…other qualia are deeply interconnected with hosts of other aspects of our perceptions. They are part of a complex structured network of qualia, and permuting just one small part of the network destroys the original shape and structure of the network - and when the network’s shape and structure is radically changed, the original meanings of the perceptions (and the qualia) within it are obliterated. But we’re beginning to know more about what colors are for, and as we learn more, color qualia are becoming more and more like other qualia in their non-permutability…

colors are part of a three dimensional space of colors, a space having certain well-known features. The space is spanned by a red-green axis, a yellow-blue axis, and a black-white axis. These three axes have opponent colors at opposite ends, and these extreme ends of the axes are pure or primary (i.e., not being built via a combination of other colors). All the colors we know of are a perceptual combination of these three axes. For example, burnt orange is built from roughly equal parts yellow and red, and is on the darker side of the black-white dimension…

Our primate color vision is peculiar in its cone sensitivities (with the M and L cones having sensitivities that are uncomfortably close), but these peculiar cone sensitivities are just right for sensing the peculiar spectral modulations hemoglobin in the skin undergoes as the blood varies in oxygenation. Also, the naked-faced and naked-rumped primates are the ones with color vision; those primates without color vision have your typical mammalian furry face…In essence, … our color-vision eyes are oximeters like those found in hospital rooms, giving us the power to read off the emotions, moods and health of those around us. On this new view of the origins of color vision, color is far from an arbitrary permutable labeling system. Our three-dimensional color space is steeped with links to emotions, moods, and physiological states, as well as potentially to behaviors. …

Furthermore, these associations are not arbitrary or learned. Rather, these links from color to our broader mental life are part of the very meanings of color - they are what color vision evolved for…The entirety of these links is, I submit, what determines the qualitative feel of the colors we see. If you and I largely share the same “perceptual network,” then we’ll have the same qualia. And if some other animal perceives some three-dimensional color space that differs radically in how it links to the other aspects of its mental life, then it won’t be like our color space. …its perceptions will be an orange of a different color.

The question now is not why colour? or is you red the same as my red? but why are colours so vivid and beautiful in our consciousness?.