Categorical properties of the color term "GOLD".

Humans are able to categorize an infinite variety of surface colors into a small number of color terms. Previous studies have shown that 11 basic color terms are commonly used in fully developed languages. These studies usually used flat matte color plates as stimuli, but we can also perceive the colors of glossy surfaces by discounting the effect of the gloss. However, color terms such as GOLD and SILVER are specifically associated with glossy surfaces. In this study, we conducted a categorical color-naming task to examine whether the color terms GOLD and SILVER could be located in a stimulus space defined by combining CIE xy chromaticity coordinates and surface reflectance and whether they had categorical properties like ordinary basic color terms. We found that GOLD and SILVER were used for specific ranges of chromaticities with stimuli having large specular reflectances. Moreover, the strengths of the categorical properties, as assessed using measures of consistency, consensus, and reaction time, were comparable to those of the basic color terms, indicating that GOLD and SILVER are categorical color terms specifically associated with glossy surfaces. This also indicates that humans do not always discount surface gloss to identify colors but can utilize this information to categorize colors.