Color criteria of facial skin tone judgment

Facial skin tone recognition provides significant social and ecological information to humans. This study utilized a five-alternative forced-choice test design wherein participants were asked to judge which color (red, yellow, green, blue, or white) they perceived as too strong in stimulus skin tone images. The results showed that the participants' reference point of facial skin tone judgement was closer to the centroid facial skin tone observed on a daily basis than the chromaticity of measured or remembered facial skin tones of the observer. This result was similar for observers from Japan and the United Kingdom. The distance between the reference point of facial skin tone judgment and the average skin chromaticity of each local group was smaller when the stimulus image was recognized as a face compared to when a uniform facial skin tone patch was used. Therefore, humans unconsciously memorize the facial skin tones they encounter in daily life and judge facial skin tones based on the centroid. Furthermore, it is critical to recognize an image as a face for the evaluation of facial skin tone.