Abstract
This chapter discusses color blindness and how it can be considered a guide and test for theories of normal vision. There are a multitude of stories to be told about the physiology of the receptor pigments of the eye and the genes that code for them, about the various kinds of cells in the retina and elsewhere in the visual system, and about color processing in the brain. It is a topic on which psychologists, physicists, biologists, and neurophysiologists have reason to be proud and glad of the convergence of interests and views. Color blindness might, at first, seem just a peripheral abnormality, but it has often been both a guide to the nature of normal color vision and a test application for theories of it. It has the potential to provide cases where the various components of a complex process that are either hard or impossible to separate artificially are found already separated in nature.
