Facial asymmetry while posing positive and negative emotions: support for the right hemisphere hypothesis.

The purpose of this report was to examine facial asymmetry during the expression of positive and negative emotions. In addition, methodological factors in the study of facial asymmetry were considered. Subjects were 16 neurologically-healthy right-handed adult males, videotaped while posing eight facial expressions (positive and negative) under two conditions (verbal command and visual imitation). Separate asymmetry ratings of the two sides of the face were made by judges viewing normal or mirror-reversed versions of the videotape. There were no effects of valence, condition, or videotape orientation on the asymmetry ratings, and, in general, expressions were produced significantly more intensely on the left than the right side of the face. This finding is consistent with the hypothesis that the right cerebral hemisphere is dominant for the expression of facial emotion of both valences.