Autonomic response patterns during voluntary facial action.

The effects of six voluntarily adopted emotional facial expressions on heart rate, respiration, emotional report, and effort ratings were examined. The results indicate that the facial expressions that were most difficult to produce (anger, fear, and sadness) showed larger cardiac accelerations than those that were easy to produce (disgust and surprise); the happiness expression fell somewhere in between. Emotional self-report revealed that in the majority of the facial configuration trials subjects experienced only moderate or no emotion at all. In addition to the emotional configurations, a nonemotional expression was examined. Post hoc comparisons showed that the heart rate data of the nonemotional face were not significantly different from any of the other emotional expressions. With respect to respiration, the production of facial expressions induced an increase in functional residual capacity, and decrease in tidal volume, shortened inspiratory and expiratory phase duration, and an increase in inspiratory pause duration. These effects were most pronounced during the facial expressions that were difficult to produce. We conclude that changes in heart rate are not the consequence of the capacity of facial activity to recruit emotion-specific autonomic activity but instead are modulated by effort-related changes in respiration.