The contribution of facial color to facial expression adaptation

Previous studies have demonstrated the significant contributions of a reddish facial color to the perception and social evaluation of facial expressions, highlighting the close relationship between facial color and perceived facial expressions. However, it remains unclear whether a reddish facial color influences the adaptation process of facial expression. In this study, we used an adaptation paradigm to investigate the contribution of facial color to this process. Two experiments were conducted in which faces with natural or reddish facial colors were used and remained unchanged throughout the process. The adaptation stimuli were either emotional faces (i.e., angry or happy) or fixation crosses (control conditions), followed by neutral faces as the target for friendliness ratings. In Experiment 1, unfiltered faces with clear emotional expressions were used as adaptation stimuli (i.e., clear facial expression information condition). In Experiment 2, hybrid faces with hidden emotional expressions presented at low spatial frequencies were used as adaptation stimuli (i.e., reduced facial expression information condition). Both experiments revealed that the reddish facial color significantly enhanced the friendliness ratings of the target faces, with this effect being comparable across adaptation conditions and becoming more pronounced when facial expression information was reduced in hybrid faces. Meanwhile, emotional aftereffect scores, quantified as the gap in friendliness scores between the control and emotional face conditions, showed no effect of facial color. Our findings suggest that facial color may influence facial impressions during facial expression adaptation, with its contribution being additive yet relatively independent within this process.