Abstract
The psychophysical relations under consideration may be described mathematically. The jnd is proportional to the subjective similarity, in small intervals, Δ λ = ø (s) and the similarity scores are given by the matrix equation S = YY', where the elements of Y are ordinates of five normal curves. yi = fi (λ). Hence, in principle Δ λ = ψ (λ), i. e., the differential threshold is a function of wave length. The constants of this somewhat complex function are those of the five normal color curves. These constants represent certain properties of the sensory and nervous mechanisms involved in the perception of color.

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