Age-invariance in the asymmetry of stimulus-evoked emotional facial muscleactivity

This study examined possible effects of aging on the lateralization of stim ulus-evoked emotional facial muscle activity. Older participants (mean age 68.4 years) and younger participants (mean age 26.4 years) viewed slides of positive, neutral, or negative emotional content. While participants viewe d the slides, bilateral electromyographic (EMG) recordings were obtained fr om the skin surface over zygomatic and corrugator facial muscles. The parti cipants also made ratings of experienced emotional valence and arousal. Exp ected patterns of subjective experience and asymmetrical EMG activity were found in response to target stimuli. Greater corrugator muscle activity occ urred during presentation of negative stimuli, whereas greater zygomatic mu scle activity occurred during presentation of positive stimuli. Consistent with right-hemisphere specialization theories of emotion, left-sided facial EMG activity was consistently greater than that of the right side during p resentation of emotional stimuli. However, neither subjective ratings nor E MG patterns showed a significant effect of age group. Such similar patterns of emotional response for the two groups suggest, that the aging process d oes not produce marked changes in stimulus-evoked emotional experience or i n the pattern, magnitude, or lateralization of facial muscle activity assoc iated with emotional states.