THE VIRTUES OF ILLUSION

The moral is plain enough. For purposes of distinguishing an object from surroundings of similar lightness, one needs to have a receptive system that is sensitive to small wavelength differences. For signalreception and identification purposes, one needs to have a receptive system engendering a few basic categories that can ignore minor variations and lump stimuli together into a small number of salient, memorable equivalence classes. With elegant economy, our visual systems does both by drawing on the same neural resources. The system of qualitative classification that this involves need not match any analogous set of structures outside the organism in order to provide real advantages to the animal that uses it. The hues that we human beings see express our system of coding wavelength information rather than some set of properties of reflecting surfaces. But the form of the coding is not just a bit of non-functional adornment freeloading on the serious business of visual information processing. We must see it, rather, as supplying the means by which a rich amount of sensory information can be rapidly and efficiently represented by cognitive machinery of limited capacity [Miller, 1957]. With color, the medium is the message. © 1992 Kluwer Academic Publishers.