Face perception is fundamentally important for judging the characteristics of individuals, such as identification of their gender, age, ethnicity or expression. We asked how the perception of these characteristics is influenced by the set of faces that observers are exposed to. Previous studies have shown that the appearance of a face can be biased strongly after viewing an altered image of the face, and have suggested that these after-effects reflect response changes in the neural mechanisms underlying object or face perception. Here we show that these adaptation effects are pronounced for natural variations in faces and for natural categorical judgements about faces. This suggests that adaptation may routinely influence face perception in normal viewing, and could have an important role in calibrating properties of face perception according to the subset of faces populating an individual's environment.

We examined how the distribution of colors in natural images varies as the seasons change. Images of natural outdoor scenes were acquired at locations in the Western Ghats, India, during monsoon and winter seasons and in the Sierra Nevada, USA, from spring to fall. The images were recorded with an RGB digital camera calibrated to yield estimates of the L, M, and S cone excitations and chromatic and luminance contrasts at each pixel. These were compared across time and location and were analyzed separately for regions of earth and sky. Seasonal climate changes alter both the average color in scenes and how the colors are distributed around the average. Arid periods are marked by a mean shift toward the +L pole of the L vs. M chromatic axis and a rotation in the color distributions away from the S vs. LM chromatic axis and toward an axis of bluish-yellowish variation, both primarily due to changes in vegetation. The form of the change was similar at the two locations suggesting that the color statistics of natural images undergo a characteristic pattern of temporal variation. We consider the implications of these changes for models of both visual sensitivity and color appearance.

Most wavelengths change hue when mixed with white light. These changes, known as the Abney effect, have been extensively studied to characterize nonlinearities in the neural coding of color, but their potential function remains obscure. We measured the Abney effect in a new way--by varying the bandwidth of the spectrum rather than mixing with white--and this leads to a new interpretation of the role of nonlinear responses in color appearance. Because of the eye's limited spectral sensitivity, increasing the bandwidth of a spectrum changes the relative responses in the three classes of cone receptor and thus would change hue if the percept were tied to a fixed cone ratio. However, we found that hue is largely independent of bandwidth and thus constant for a constant peak wavelength for stimuli with Gaussian spectra. This suggests that color appearance is compensated for the eye's spectral filtering, and that this compensation embodies specific perceptual inferences about how natural spectra vary. When a wavelength is instead diluted with white light--which does not bias the cone ratios--then the same compensation predicts changes in hue because the "right" response is made to the "wrong" stimulus. This model generates constant hue loci that are qualitatively consistent with measures of the Abney effect and provides a novel functional account of such effects in color appearance, in which postreceptoral responses are adjusted so that constant hue percepts are tied to consistent physical properties of the environment rather than consistent physiological properties such as the cone ratios.

Although the color measurement of facial skin becomes more common in dermatology and cosmetics, little is known about the relationship between subjective color perception and colorimetric values in facial skin. In this study, the possible relationships among perceived whiteness and the metric lightness, chroma and hue angle of Japanese females' facial skin color were investigated. First, the perceived brightness of the facial skin of Japanese females was evaluated visually and compared with metric lightness, chroma and hue angle, and the effect of hue and chroma on the perceived brightness was discussed. Second, a psychophysical experiment on the whiteness of the facial images and synthesized skin color plate images was conducted for examining the effect of hue and chroma on the perceived whiteness more precisely and independently. The results of two experiments showed that in regard to the facial skin color of the Japanese female, metric lightness disagrees with perceived whiteness or brightness in a narrow lightness range. The reddish facial skin color appeared brighter or whiter than that of a yellowish one in high lightness regions, and the low‐chroma facial skin color appeared brighter or whiter than a high‐chroma one. However, in the color plate images, a change in perceived whiteness by hue could not be confirmed, and the change in perceived whiteness by chroma was weaker than that from facial images. These results indicated that a higher‐level process of face recognition affected whiteness perception, and the criterion of facial skin whiteness was determined by facial skin color distribution. © 2011 Wiley Periodicals, Inc. Col Res Appl, 2011;

We developed a new quantitative evaluation method for individual pigmented spots in facial skin. This method facilitates the analysis of the characteristics of various pigmented facial spots and is directly applicable to the fields of dermatology, pharmacology, and esthetic cosmetology.