The colour of words: how dichromats construct a colour space

Abstract

ABSTRACTPeople with strong protanopia and deuteranopia – colloquially termed “red-green colour blindness” – are dichromatic and are unable to visually discriminate between colours corresponding to the long-wavelength end of the visible light spectrum. We used nonmetric multidimensional scaling to create colour spaces for a sample of protanopes and deuteranopes, and compared them to spaces derived from trichromats with normal colour vision. Colour spaces based on dissimilarity judgements between actual colours (hue-only condition) revealed the anticipated collapse of a dimension distinguishing long-wavelength colours. Judgements based on basic or descriptive colour terms (term-only conditions) produced two-dimensional configurations resembling those of trichromats. When hues and terms were presented together (hue + term condition), the dichromatic colour space was intermediate between the spaces derived from the hue-only and term-only conditions. The findings reveal that language can effectively substitute for an impoverished colour experience, and indicate a surprising element of “visual capture” in dichromatic observers.