Hemispheric differences in recognizing upper and lower facial displays of emotion

Objective: To determine if there are hemispheric differences in processing upper versus lower facial displays of emotion. Background: Recent evidence suggests that there are two broad classes of emotions with differential hem ispheric lateralization. Primary emotions (e.g. anger. fear) and associated displays are innate, are recognized across all cultures, and are thought t o be modulated by the right hemisphere. Social emotions (e.g., guilt. jealo usy) and associated "display rules" are learned during early child developm ent, vary across cultures, and are thought to be modulated by the left hemi sphere. Display rules are used by persons to alter, suppress or enhance pri mary emotional displays for social purposes. During deceitful behaviors, a subject's true emotional state is often leaked through upper rather than lo wer facial displays, giving rise to facial blends of emotion. We hypothesiz ed that upper facial displays are processed preferentially by the right hem isphere, as part of the primary emotional system, while lower facial displa ys are processed preferentially by the left hemisphere, as part of the soci al emotional system. Method: 30 strongly right-handed adult volunteers were tested tachistoscopically by randomly flashing facial displays of emotion to the right and left visual fields. The stimuli were line drawings of faci al blends with different emotions displayed on the upper versus lower face. The subjects were tested under two conditions: 1) without instructions and 2) with instructions to attend to the upper face. Results: Without instruc tions, the subjects robustly identified the emotion displayed on the lower face. regardless of visual field presentation. With instructions to attend to the upper face, for the left visual field they robustly identified the e motion displayed on the upper face. For the right visual field, they contin ued to identify the emotion displayed on the lower face. but to a lesser de gree. Conclusions: Our results support the hypothesis that hemispheric diff erences exist in the ability to process upper versus lower facial displays of emotion. Attention appears to enhance the ability to explore these hemis pheric differences under experimental conditions. Our data also support the recent observation that the right hemisphere has a greater ability to reco gnize deceitful behaviors compared with the left hemisphere. This may be at tributable to the different roles the hemispheres play in modulating social versus primary emotions and related behaviors.