EMG activity in response to static and dynamic facial expressions.

The EMG activity associated with static and dynamic facial expressions (morphs with happy or angry emotions) were compared. We hypothesized that dynamic faces would (a) enhance facial muscular reactions and (b) evoke higher intensity ratings. Our analysis showed that dynamic expressions were rated as more intense than static ones. Subjects reacted spontaneously and rapidly to happy faces with increased zygomaticus major EMG activity and decrease corrugator supercilii EMG activity - showing greater changes in response to dynamic than to static stimuli in both muscles. In contrast, angry faces evoked no alteration of EMG activity in zygomaticus muscles and only small changes in the corrugator muscle EMG, and there was no difference between the responses to static and dynamic stimuli. It may be concluded that the dynamic property facilitates processing of facial expressions of emotions.