Facial expressions are more easily produced on the upper-lower compared to the right-left hemiface

Clinical research has concentrated on differences in intensity of expression between the right and left hemiface as a means to assess hemispheric differences in motor control. However, observations by social psychologists suggest that control of facial expression may be organized predominantly across the upper-lower hemiface because during social interactions individuals may produce brief facial blends of emotions, in which the upper and lower face display a different emotion. Full facial versus upper/lower and right/left facial blends of emotion were posed by 20 subjects, 10 men and 10 women ranging in age from 20 to 37 years. The subjects rated the difficulty of each pose on a 5-point Likert scale. Digital photographs of the poses were taken and the full and half-facial poses were shown in random order to four judges who indicated what pose was being performed. The results were very robust and confirmed that facial blends of emotion are more easily and accurately posed on the upper-lower than on the right-left hemiface. Our results are consistent with recent anatomical studies showing separate cortical areas for motor control of the upper versus lower face in primates. Based on recent research exploring hemispheric differences in perceiving facial blends of emotion, the left hemisphere may be more involved with modulating lower facial expressions and the right hemisphere more involved with modulating upper facial expressions.