Color vision is a sensory capability that is extremely valuable for discriminating objects. The retina of the eye detects colors using the cone cells, containing special pigments that are the expression of certain genes. New discoveries in genetics have led to some proposed generalizations about the distribution and evolution of color vision in primates, which are considered to be the only mammals with exceptional color vision. But very few primate species have been rigorously studied for this attribute, to either confirm or refute the generalized picture. Earlier work revealed a large variability both among individual squirrel monkeys in making color matching tests, and in the pigments found in the cone cells of the retina of individual animals. The variation was discovered to be related to expression of color pigments based on a single gene on the X-chromosome, so there is a fundamentally different variability between male and female color perception. Preliminary studies have extended this finding to a few other "new-world monkey" species, emphasizing the difference from humans and "old-world monkeys" so far studied, which have a second cone pigment gene on the X-chromosome. This project will use behavioral measurements of color vision, and external recording of retinal potentials that convey information about the cone pigments, from a variety of monkey and prosimian species. The data will be used to test how valid the generalization may be about color vision in new-world and old-world monkeys, and how early in the evolutionary branching of primates the genetic split may have occurred. This novel work, using psychology, physiology, genetics, and zoology, will have impact on visual neuroscience and behavioral ecology, and may even provide some insight into human origins.
