Abstract
The perception of lightness is context-dependent, which can be revealed in the influence of face-races on the perceived face lightness. Participants perceived Black faces as darker than White faces. However, some findings indicated that the distorted lightness perception remained even when face race information was undetectable. The discrepancy challenges the role of race categories: Is the distorted lightness perception induced by the knowledge about face-race? To address this question, we recruited 123 Asian participants, who saw two rapidly sequentially presented faces (500ms). The two faces within each trial were of the same race: Black or White. While the luminance of the first face was matched across the Black and White face trials, the luminance of the second face was decreased or increased by 4 levels (-20, -12, -8, -4, +4, +8, +12, & +20). Participants were asked to report whether the second face was lighter or darker than the first face. To examine the role of face-race knowledge, as opposed to low-level perceptual cues, we further manipulated the orientation of the two faces across participants: Upright-Upright, Inverted-Inverted, Upright-Inverted, and Inverted-Upright. Overall, Black faces were perceived significantly darker than White faces, even their luminance was matched (p < 0.05). Moreover, this face-race distortion effect was only found when faces were upright, but not when they were inverted. Lastly, the distortion effect was found only when the first face was upright regardless of the orientation of the second face. These findings of orientation-specificity suggest that the effect was not due to low-level perceptual cues but driven by conceptual knowledge of face races. Together, these findings indicated the role of race categories in the perception of lightness and highlighted a special mechanism, where face-race conceptual information modulates the perception of low-level facial information, such as lightness.