The purpose of colour

Previously I looked at C. Here is the E in an AtoZ by P. Long in My Brain on My Mind. (here)

Easy Problem. Philosopher’s lingo for the problem in neuroscience of comprehending the neuronal correlates of consciousness. When you see red, what exactly are your neurons doing? When you remember your grandfather’s face, what are your neurons doing? It may be difficult to parse the answer but in principle we can do it. It’s easy. The Hard Problem is the mystery of subjective experience. When long light waves stimulate our neural pathways, why do we experience the color red? And what survival benefit caused our brains to develop, through eons of evolution, an ability to experience a “sense of self,” a self able to see itself as special or heroic or smart or not so smart—as, on occasion, a complete failure?

I am not going to discuss a sense of self here, as it seems self evident that a sense of self is useful.

It is not usually quoted as an example of the hard question. Usually we see colour mentioned. Why does the personal experience of colour seem unexplainable? or at least a different order of mystery from other things?

What is the function of colour? It is definitely not there so that we can know the wavelength of light. We do not need or want to know the wavelength of light and, further more, colour is not a reliable measure of wavelength The colours that we see are ‘corrected’ in so many ways and to such an extent that their mapping to the physical wavelength of light is very approximate. Forget wavelength.

What colour does is to help give us objects. Our experience is of a three-dimensional space that is populated with objects. Objects are created by our perception to have particular locations, sizes and surfaces. We understand the world in terms of its objects and the world at any point in time is just objects in space. We recognize them, remember them, categorize them, name them and so on. Our lives are easier if objects that are not actually shrinking or growing, keep their size no matter how much of our retina they take up. We do not want them to move unless they are mobile even though our eyes are flicking their image around on our retina. We do not want objects to suddenly disappear or appear unless they actually are intermittent. And we do not want the surface of an object to change unless it is actually chemically or physically changing. The light (and sound) that is reflected off (and the feel to touch or smell of) an object is important to recognizing that object – such as noticing the archetypal tiger in the long grass at twilight. What our perception creates is objects and they have surface as important property. Those surfaces have colour as part of their image. So colour is very useful in recognizing and remembering objects.

Why is colour so complex in its nature and so delightful to us? The more complex it is, the more we can differentiate between similar surfaces. As far as delighting us – all the aspects of all our senses delight us or disgust us as appropriate. We build a model of the world; we are aware of parts of that model when we are conscious; we remember that model as we live in it; what is important and memorable in the model at any time is what we attend to and remember.

We do not have an explanation for colour or other aspects of subjective experience, but when put in a biological context, it does not seem any harder than many other questions. When we compare it to other questions in biology, why assume it was somehow different and unsolvable?

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