Abstract
The two halves of the human face differ in strength of emotion expression. This has been shown in studies using ‘chimeric’ face pictures, in which one half of the face is replaced by the mirror image of the other. Left-left chimeras are often rated as more emotionally expressive than right-right chimeras, indicating higher expressiveness of the left hemiface. This finding has been interpreted as support for a ‘right-hemisphere model’ of emotion. However, some studies suggest a reduction or reversal of asymmetry for positive emotions, a finding considered as supporting the ‘valence model’. We investigated movement asymmetries and differences in expressiveness between the two sides of the body in emotional full-body movement.
METHOD: Emotional gaits (angry, happy, sad, fearful) of thirteen right-handed lay actors were motion captured. Joint-angle trajectories (flexion angles of shoulder, elbow, hip and knee) were computed. Movement amplitudes and kinetic energies were compared between both body halves. ‘Chimeric walkers’ were created by animation of avatars, replacing the joint movements of one body side by those of the other, with appropriate temporal alignment. Perceived expressiveness of right-right and left-left walkers was assessed in a rating study, controlling for the influence of viewing angle. In addition, animations with the original trajectories and mirror-reversed animations were presented.
RESULTS AND DISCUSSION: For all four tested emotions movement energy and amplitude were larger for the left side of the body, especially for the upper extremities. Left-left chimeric walkers received higher expressiveness ratings than right-right walkers, implying greater expressiveness of the left hemibody (consistent with the ‘right-hemisphere model’). The comparison between normal and mirror-reversed animations ruled out possible confounds by attention differences between right and left visual hemifield.
Supported by HFSP, Volkswagenstiftung and EU project COBOL (FP6-NEST).