Abstract
The brightness perception of a face is influenced by skin color. It has been reported that reddish skin appeared brighter than yellowish skin when both had the same lightness for Japanese observers (Yoshikawa et al., 2012). Other reports have shown that observer diversity affects the brightness perception of facial skin (He et al., 2020). There are several possibilities, such as an influence of ethnicity, environment, and difference in the judgment criteria. Here, we investigate the influence of the judgment criteria on the brightness perception of the face. The six original faces were used to generate a test stimulus image with constant lightness and different hue angles. There are two types of scale stimuli: uniform color patches and face images. Observers adjusted the scale stimuli's lightness to match the test stimulus's appearance. We used two criteria for the judgment: brightness match, the same as in previous studies (He et al., 2020), and appearance match. In addition, we made an impression evaluation of the face. Observers were Japanese and Thai. The result of all observers for the appearance match showed a trend that yellowish skin appeared brighter, which was contrary to the previous Japanese observer's results. The result of brightness match also showed a similar trend except for those of Japanese in a particular condition. In general, the result of the two scale stimuli showed a similar trend, but the matched brightness by uniform patch tends to be higher than that by face image scale. On the other hand, all observers rated the reddish face stimulus as brighter in the impression evaluation. This implies that the different judgment criteria or cognition processes underlie the matching and impression evaluation tasks.