Lateralized Facial Muscle Response to Positive and Negative Emotional Stimuli

Facial electromyography (EMG) was recorded from left and right zygomatic and corrugator muscle regions in response to reflective questions and during voluntary facial expressions. Both muscle regions showed consistent responses to five emotions (happiness, excitement, neutral, sadness, and fear) evoked in the involuntary condition (i.e. reflective questions) and four emotional facial expressions (happiness, excitement, sadness, and fear) self‐generated in the voluntary condition. Lateralized responses were found for the zygomatic muscle in the involuntary condition: positive emotion questions elicited relatively greater right muscle activity than left muscle activity, while negative emotion questions elicited relatively greater left muscle activity than right muscle activity. Lateralized responses were found for the corrugator muscle in the voluntary condition, but were not significantly related to type of emotional expression. Sex differences indicating greater lateralization for females were found in some of the measures. The results are consistent with the hypothesized specialization of the left and right cerebral hemispheres for the mediation of positive and negative emotions, respectively.