Warm/cool judgments as a function of hue, value, and chroma.

Besides conventional perceptual attributes of hue, brightness, and saturation, colors are universally classified along a warm/cool dimension. Previous estimates of how warm/cool values are distributed across color space have relied on subjective ratings. Here we employed simple ordinal judgments between stimulus pairs using maximum likelihood conjoint measurement (MLCM) to assess the influence of Munsell hue, value, and chroma on warm/cool judgments. We also evaluated an identification task for single stimulus presentations. For the MLCM procedure, observers judged on each trial which of the two stimuli appeared warmer. For the identification task, observers classified individually presented color patches as cool or warm. The judgments were analyzed with probit regression to estimate the underlying perceptual scale values. The results confirm that the contributions of different dimensions to warm/cool variations in color space can be estimated using only ordinal judgments. While for most observers, warm/cool judgments depended on hue, there were individual variations in the extent to which value contributed to warm/cool, and little evidence for an effect of chroma.