Hue signals from short- and middle-wavelength-sensitive cones.

Hue sensations resulting from the selective stimulation of short-wavelength-sensitive (S) and middle-wavelength-sensitive (M) cones were deduced from measurements of spectral unique green and unique blue under conditions of high or low S-cone sensitivity relative to M- and long-wavelength-sensitive-cone sensitivity. Selective reduction of S-cone stimulation shifted unique blue toward shorter wavelengths and unique green toward longer wavelengths, implying losses of perceived yellowness and short-wavelength redness relative to perceived blueness. The results imply that, under acromatic adaptation conditions, M-cone stimulation yields a sensation of predominantly bluish cyan and S-cone stimulation yields a sensation of predominantly reddish magenta. S-cone stimulation also appears to be indirectly responsible for yellowish sensations at long wavelengths and, by cancellation of the M-cone blueness signal, for greenish sensations at middle wavelengths.