Keiji UCHIKAWA

Department of Information Processing, Tokyo Institute of Technology, Yokohama 226-8502, Japan

(Received July 14, 2014; Revised September 6, 2014; Accepted September 6, 2014)

Color changes as a continuous variable. We can discriminate millions of colors, but at the same time we categorize colors into discrete color names. Dichromat (color deficient) observers also categorize colors in manners very similar to that of color normal (trichromat) observers despite the fact that color deficient observers confuse many colors. In this study, we investigated characteristics of categorical color perception of trichromat and dichromat under various chromatic illuminations. Observers named 424 OSA uniform color samples using only the Berlin and Kay's eleven basic color terms. Categorical color perception of normal trichromat was found to be robuster under strong chromatic illuminants than dichromats. Dichromats could utilize a lightness cue to name indistinguishable colors. It is unlikely that dichromats have the same categorical color mechanism as normal trichromat has. The present results support that there is the physiological substrate for categorical color perception specific to trichromat or dichromats.

Key words: color names, categorical color naming, basic color terms, color deficiency, color constancy