Color, consciousness, and the isomorphism constraint

The relations among consciousness, brain, behavior, and scientific explanat ion are explored in the domain of color perception. Current scientific know ledge about color similarity;, color composition, dimensional structure, un ique colors, and color categories is used to assess Locke's "inverted spect rum argument" about the undetectability of color transformations. A symmetr y analysis of color space shows that the literal interpretation of this arg ument - reversing the experience of a rainbow - would not work. Three other color-to-color transformations might work, however, depending on the relev ance of certain color categories. The approach is then generalized to exami ne behavioral detection of arbitrary differences in color experiences, lead ing to the formulation of a principled distinction, called the "isomorphism constraint," between what can and cannot be determined about the nature of color experience by objective behavioral means. Finally, the prospects for achieving a biologically based explanation of color experience below the l evel of isomorphism are considered in light of the limitations of behaviora l methods. Within-subject designs using biological interventions hold the g reatest promise for scientific progress on consciousness, but objective kno wledge of another person's experience appears impossible. The implications of these arguments for functionalism are discussed.