Discrimination of binocular color mixtures in dichromacy: evaluation of the Maxwell-Cornsweet conjecture.

We tested the Maxwell-Cornsweet conjecture that differential spectral filtering of the two eyes can increase the dimensionality of a dichromat's color vision. Sex-linked dichromats wore filters that differentially passed long- and middle-wavelength regions of the spectrum to each eye. Monocularly, temporal modulation thresholds (1.5 Hz) for color mixtures from the Rayleigh region of the spectrum were accounted for by a single, univariant mechanism. Binocularly, univariance was rejected because, as in monocular viewing by trichromats, in no color direction could silent substitution of the color mixtures be obtained. Despite the filter-aided increase in dimension, estimated wavelength discrimination was quite poor in this spectral region, suggesting a limit to the effectiveness of this technique.