How Do We Perceive Color?

You know, a funny thing about the contemporary neuroscience of consciousness is it's really closet philosophy. It's really, it's very often making fundamental philosophical assumptions. That is to say, it’s taking certain philosophical ideas for granted, and it’s often using empirical information simply to reanimate old debates. For example, one of the basic sort of guiding pictures I think that people thinking about the neuroscience of consciousness have is that the world is in our head. The brain makes the world; that is what we experience is not—I don’t experience you. I don’t see you. I experience something in my brain that is confabulated on the basis of a pattern of stimulation.

Let me come to the nature of color as an example to try to illustrate what I have in mind. And by the way, this is a wonderful area where both science and philosophy have tended to really collaborate, have been in dialogue with each other, and in many cases, the leading philosophers have also been the leading scientists thinking about this. One view is that color is a property of the surfaces of objects, not the property we naively think we see, but maybe something like a disposition to absorb and reflect light of certain wavelengths and to produce a sort of what is known as a spectral reflectance profile, but the color is on the surface.

Another view is that it’s an illusion to think of color as something in the thing, that color is merely an affect that the thing has on us. In that sense, the color happens to us. The leaves in the tree are not green. Greenness is just something that happens. In me, it’s a kind of sensation that is produced thanks to the activation of my nervous system by those leaves.

My own view is that both of those views are wrong. I advocate the view that color is what you might call an ecological property, and by that I mean color is a feature of the way light and surfaces interact. It’s not, in that sense, intrinsic to the surface of the leaf that it is green. Its greenness is the way it behaves in relation to lighting. So we think of the color as stable, but of course the color looks one way under one light and if you take it outside, it looks different, and if you turn it in certain ways, there will be highlights and sort of little specular shining points on the surfaces of things that are all part of the real color of the thing.

For me, colors are like shapes. Just as a three-dimensional shape has a hidden backside, so colors have hidden ways they would look if the conditions of lighting were changed. The problem of skepticism about the external world—how do we know that things are the way they seem to be? How do we know that our perceptual experiences are reliable?—is a chestnut. It’s an old philosophical chestnut that I can’t solve for you right now, and that neuroscience can’t solve. But what I’d like to impress on you is that neuroscience has taken a solution to that, or at least an attitude towards that old philosophical chestnut, for granted. Most neuroscientists working on consciousness suppose experience is something that happens inside of me. It’s subjective. It’s hidden. The world is this we know not what, which is beyond the surfaces of our tent. Beyond the reach of our direct knowledge because all we ever know is the way our nervous system is bombarded by stimulation. That which is causing the stimulation is always beyond.

Directed / Produced by Jonathan Fowler & Elizabeth Rodd.