Twins and odd-ones-out: A twin study of genetic contributions to variability in personal colour space

Abstract

Background: Individuals differ in the biological substrate of vision, often as a result of genetic differences. There are also subtle variations within the normal population in aspects of colour behaviour (for example, colour naming and unique-hue judgements) but it is surprisingly hard to connect these to the genetic variation. Perceptions of intercolour similarities (and variations in the structure of colour space, reconstructed from them) may show a closer link to the biological basis of vision. Methods: To quantify the spectrum of variation, each subject used caps from the D-15 panel test to make 70 odd-one-out triad judgements. Analysis yielded the parameters of individual observers' colour structure: specifically, the weights they placed on the axes of a standard colour space. Similarities between 19 pairs of monozygotic twins and between 16 pairs of dizygotic twins were compared. Results: Monozygotic pairs were significantly more concordant than dizygotic or unrelated pairs. Discussion: The procedure provides sufficiently precise measurements to replicate earlier findings from more complex, time-consuming methods. By extension to other family relationships, the triadic procedure can clarify the genetic contribution. Weighting of colour axes is an important form of variation among normal individuals, with a contribution to these weights from genetic factors.