Dichromatic subjects can name colors accurately, even though they
cannot discriminate among red-green hues (Jameson & Hurvich, 1978). This result is attributed to a normative
language system that dichromatic observers developed by learning subtle
visual cues to compensate for their impoverished color system. The present
study used multidimensional scaling techniques to compare color
categorization spaces of color-vision deficient (CVD) subjects to those of
normal trichromat (NT) subjects, and consensus analysis estimated the
normative effect of language on categorization. Subjects sorted 140
Munsell color samples in three different ways: a free sorting task
(unlimited number of categories), a constrained sorting task (number of
categories limited to eight), and a constrained naming task (limited to
eight basic color terms). CVD color categories were comparable to those of
NT subjects. For both CVD and NT subjects, a common color categorization
space derived from the three tasks was well described by a
three-dimensional model, with the first two dimensions corresponding to
reddish-greenish and yellowish-bluish axes. However, the third axis, which
was associated with an achromatic dimension in NTs, was not identified in
the CVD model. Individual differences multidimensional scaling failed to
reveal group differences in the sorting tasks. In contrast, the personal
color naming spaces of CVD subjects exhibited a relative compression of
the yellowish-bluish dimension that is inconsistent with the typical
deutan-type color spaces derived from more direct measures of perceptual
color judgments. As expected, the highest consensus among CVDs (77%) and
NTs (82%) occurred in the naming task. The categorization behaviors
studied in this experiment seemed to rely more on learning factors, and
may reveal little about CVD perceptual representation of colors.