Abstract

Early psychophysical methods as codified by Fechner motivate the development of quantitative theories of subjective experience. The basic insight is that just noticeable differences between experiences can serve as units for measuring a sensory domain. However, the methods described by Fechner tacitly assume that the experiences being investigated can be linearly ordered. This assumption is not true for all sensory domains; for example, there is no trivial linear order over all possible color sensations. This paper discusses key developments in the history of psychophysical methods for measuring color experience. In particular, a clear distinction between topological and metrical structure allowed Helmholtz to use opponent colors as a standard for measuring the gross structure of color space. Once this gross structure had been determined, lines through color space could be defined and Fechner-style methods employed for determining local structure. Extensions of these methods due to Wright, MacAdam, and others provide detailed evidence for the degree of agreement in the qualities of color experience across individuals. This allows a precise statement of the evidential support for the claim that your experience of color and mine are the same.