Any color you choose can be matched by a mixture of short, medium and long wavelength light (i.e., blue, green and red light). This perceptual observation led to the formulation, early in the 19th century, of a neurophysiological hypothesis: The eye contains three kinds of distinct color-sensitive receptors (cones); just as colors themselves can be composed of lights of different spectral character, so we can see the vast range of visible color thanks to the joint operation of only three distinct kinds of receptors.
This is a beautiful example of the primacy of experience in the study of the brain-basis of consciousness. Before you can even begin to think about how the brain enables us to see or feel or (more generally) experience what we do, you need to pay careful attention to what our experience is actually like.
And, so, it was further attention to the experience that led scientists to realize the shortcomings of what came to be known as the Trichromatic Theory of Color.
Consider: You get purple by mixing blue and red light. Indeed, purple is just a reddish-blue or a bluish-red; you can actually see the red and blue in the purple, and you can imagine a purple becoming more and more blue until it is entirely blue.
The Trichromatic Theory tries to explain these phenomena by suggesting that we see purple when our red and blue sensitive cones (that is, our long wave- and short wave-sensitive cones) are activated at the same time. Different purples correspond to different ratios of activation.
But now, consider the case of yellow. You get yellow by mixing red and green light, just as you get purple by mixing red and blue. But yellow isn’t reddish-green or greenish-red in the way that purple is reddish-blue. In fact, there is no such thing as reddish-green. Moreover, you don’t see red or green in yellow the way you see blue and red in purple. Yellow, like blue and red, but not like purple, is unary, not binary.
The Trichromatic Theory has no resources to explain facts about color vision such as these. In order to explain them, neurophysiologists were led to propose a totally different kind of theory of neural processing beyond the retina (the so-called Opponent Processing Theory).
I speak of the primacy of experience in order to bring out the fact that an investigation of what we see — a careful reflection on rules governing our experience — is a necessary preliminary to the neurophysiological study of how neural states support and enable consciousness.
But how do we study experience? How do we carry out what is sometimes, in philosophical circles, called phenomenology?
There are three kinds of obvious obstacle. First, most of the time, in daily life, we aren’t interested in experience itself. We are interested not so much in the experience of color, for example, as in such things as whether the tomato is ripe, or whether you should paint your living room this shade of off-white rather than one of the half-dozen other shades for sale at the same hardware store. Paying attention to experience requires new skills, or at least new habits.
Second, so often when you do turn your attention to your experience, you change the experience. When was the last time you compared the way your sweater looks in different conditions of illumination? If you were to do that you’d probably notice features that had never been brought to your attention before. Have you better appreciated how your sweater really looks? Or do you now experience it differently?
Finally, our attitudes about experience are usually governed by familiar concepts, and those familiar concepts don’t really do justice to the great variety we actually experience. Take that red car parked out front. You see it. It’s red. You experience its color. But there is so much more to be said about how it looks, even just confining our attention to color, than merely that it looks red.
At one end it is glowing white in the direct glare of the sun. At the other end it is bathed in cool shadow and looks, really, almost gray. Gaining access to the structure and quality of experience requires, it would seem, a better taxonomy of qualities and modes of awareness of those qualities. It isn’t obvious that ordinary language and thought provide us with this superior taxonomy.
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