Analysis of color categorization for color vision deficient subjects at different luminance levels
This study aimed to compare color categorization characteristics of color vision deficient (CVD) observers with those of normal trichromat (NT) observers. In order to investigate the effects of color luminace and the use of perceptual judgements on color categorization properties, the experiment carried out at three luminance levels by using two experimental tasks, a color-naming task (CNT) and a color-sorting task (CST). We used 68 color stimuli at three luminance levels. In the CNT, four CVD and four NT subjects selected one color category among 12 categories including 11 basic color terms and an unknown category. In the CST, which is a color categorization performed using perceptual judgements, they sorted colors which were simultaneously presented according to 12 categories. As the results, we found that the number of responding the CVD subjects for the green category in both tasks was higher than that of the NT subjects at all luminance levels. For both NT and CVD subjects, each color categorization space derived by the multidimensional scaling method was described in two dimensions. We also explored the relationships between each dimension axis and a chromatic system. Moreover, consensus analysis revealed that the consensus among CVD subjects was low at lowest and highest luminance levels. We demonstrated that luminance affects color categorization properties, as evidenced by the differences between CVD and NT observers at lowest and highest luminance level.