The Asymmetry of Facial Actions is Inconsistent with Models of Hemispheric Specialization

Several models of hemispheric specialization have been used to explain asymmetries in facial actions. This study measured the asymmetry of several different muscular actions individually, alone and in combination, and under different eliciting conditions. The findings did not fit any of the theoretical models. In the deliberate actions, some of the asymmetries were lateralized with greater intensity on the left side; others, on the right side. Spontaneous actions were more symmetrical than the deliberate, requested actions. We rejected specialization for emotion as a cause of the facial asymmetry observed, and discussed the weaknesses of other models.