Facial asymmetry in posed and spontaneous expressions of emotion.

Patterns of facial asymmetry (i.e., extent of movement) as a function of elicitation condition, emotional valence, and sex of subjects are examined. Thirty-seven right-handed adult males and females were videotaped making positive and negative expressions of emotion under posed (verbal, visual) and spontaneous conditions. There were no differences in facial asymmetry as a function of condition. Overall, expressions were significantly left-sided, a finding implicating the right hemisphere. When sex and valence were considered, negative expressions were left-sided for all subjects, while positive expressions were left-sided for males only. Further, positive expressions were significantly less lateralized than negative ones for females. Measures of hemiface mobility and ocular dominance did not mediate these patterns of facial lateralization.