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Hisashi Komine, Keizo Shinomori, Shigeki Nakauchi; Representation of color naming category boundaries on dichromats along their confusion loci using a chromatic-opponent channel model. Journal of Vision 2009;9(8):321. doi: https://doi.org/10.1167/9.8.321.
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© ARVO (1962-2015); The Authors (2016-present)
Protanopia and deuteranopia are color vision types that cause difficulties of discrimination between red and green hue combinations along the specific directions, that are called confusion loci. Nevertheless, Jameson and Hurvich (1978) found that some dichromats used reddish or greenish color terms despite their impoverished red-green hue discrimination ability. Montag and Boynton (1987) investigated dichromats' color naming categories and dichromatic subjects showed color naming categories that are fairly in agreement with trichromats. They predicted the contribution of rods to dichromats' naming ability. In his following study, Montag (1994) suspected the contribution of an anomalous third cone pigment. Bonnardel (2006) used multidimensional scaling (MDS) techniques to analyze dichromatic color naming categories and concluded that categorizations of dichromats depend on learning factors. However, it is still unclear how dichromats perform the trichromatic color naming.
In this study, we tested dichromats' color naming categories along their confusion loci that go through the equal energy white point. Subjects named 203 kinds of test stimuli with 11 basic color terms (Berlin and Kay, 1969). Test stimuli were presented as a circular aperture (2 degrees in diameter) on the illuminated background (x,y,L: 0.31, 0.32, 20.82cd/m2). In addition, we represented dichromats' naming category boundaries along outputs of Boynton's color vision model (1979). In the case of protanope, the boundaries were fairly represented by constant M-cone output lines. On the other hand, in the case of deuteranope, it could not be represented by constant L-cone output lines. When we assumed the r-g chromatic-opponent mechanism includes signals from L and Hybrid-cone (Merbs and Nathans, 1992), the constant outputs of the model could represent naming category boundaries of deuteranope. This suggests that the color naming categories of dichromats are reorganized by acquiring color terms and some dichromats rely on the presence of Hybrid-cone pigment to show trichromatic color naming categories.
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