Men appear more lateralized when noticing emotion in male faces.

Empirical tests of the "right hemisphere dominance" versus "valence" theories of emotion processing are confounded by known sex differences in lateralization. Moreover, information about the sex of the person posing an emotion might be processed differently by men and women because of an adaptive male bias to notice expressions of threat and vigilance in other male faces. The purpose of this study was to investigate whether sex of poser and emotion displayed influenced lateralization in men and women by analyzing "laterality quotient" scores on a test which depicts vertically split chimeric faces, formed with one half showing a neutral expression and the other half showing an emotional expression. We found that men (N = 50) were significantly more lateralized for emotions indicative of vigilance and threat (happy, sad, angry, and surprised) in male faces relative to female faces and compared to women (N = 44). These data indicate that sex differences in functional cerebral lateralization for facial emotion may be specific to the emotion presented and the sex of face presenting it.