Effect of Social Skills on the Asymmetry in Facial Expressions

This study investigated the effect of social skills on the facial movement asymmetry in facial expressions. Threedimensional facial landmark data of facial expressions (neutral, happy, and angry) were obtained from Japanese participants (n = 62). After the facial expression task, each participant completed KiSS-18 (Kikuchi’s Scale of Social Skills; Kikuchi, 2007). Through a generalized Procrustes method, facial landmark coordinates and their mirror-reversed versions were represented as points on a hyperplane. The asymmetry of each face was defined as Euclidian distance on the plane. Subtraction of the asymmetry level of a neutral face of each individual from the asymmetry level of a target emotion face was defined as the index of “movement asymmetry” of each emotion. Correlation coefficients of Kiss-18 scores and movement asymmetry scores were computed for both happy and angry expressions. Significant negative correlations between Kiss-18 scores and movement asymmetries were found for both expressions. The results indicate that symmetric facial expressions are higher with higher level of social skills.