Do gender and personality predict aggregated measures better than single-act measures of smiling

Eighty-four students (27 men, 57 women) were assessed on sex differences in smiling using aggregated multi-act measures of smiling (based on multiple photographs) versus single-act measures of smiling (based on single photographs of participants). Smiling was assessed from photographs from three age ranges (8--10, 13--15, 8--23) and from photographs taken in a lab session. Participants completed measures of Big Five personality traits and personality traits related to aspects of Masculinity and Femininity. Personality data were used to explore if sex differences in personality mediated sex differences in smiling. Results showed no sex difference in smiling in childhood photos and large sex differences in smiling in adolescent and adult photos. Sex differences in smiling tended to be larger for aggregated than for single-act measures of smiling. Finally, personality traits correlated only weakly with smiling, and sex differences in personality did not account for sex differences in smiling. These results suggest that sex differences in smiling may be underestimated in studies that use just single-act measures of smiling.