Hemifacial asymmetries in age perception: the left cheek looks older for females, but not males

The left hemiface expresses emotion more intensely than the right. Because emotional expressions contract the facial muscles and wrinkle the skin, theoretically the left hemiface’s greater expressivity should prompt more pronounced expression lines and wrinkles on the left than right side of the face. As wrinkles are the most salient age cue, we investigated whether the left hemiface consequently appears older than the right. Two hundred and sixty participants (F=148; M=112) viewed booklets containing pairs of left-left and right-right chimeric faces of eight models (M=F). For each trial participants were asked to make a two alternative forced choice response indicating which image looked older. Results confirmed a left cheek bias, with participants more likely to select left-left than right-right chimeras. Whilst participant gender did not influence perceptions, model gender predicted cheek selections: responses to female models drive the overall left cheek bias. The left cheek (56.8%) appeared older than the right cheek (43.2%) for female models, whereas there was little difference in perceived age between male models' left (50.8%) and right (49.2%) cheeks. Given that youth influences perceptions of female beauty, these findings complement previous research and offer a potential explanation for why the left side of females’ faces are judged less attractive: the right cheek appears younger