Observing facial expressions automatically prompts imitation, as can be seen with facial electromyography. To investigate whether this reaction is driven by automatic mimicry or by recognition of the emotion displayed we recorded electromyograph responses to presentations of facial expressions, face-voice combinations and bodily expressions, which resulted from happy and fearful stimuli. We observed emotion-specific facial muscle activity (zygomaticus for happiness, corrugator for fear) for all three stimulus categories. This indicates that spontaneous facial expression is more akin to an emotional reaction than to facial mimicry and imitation of the seen face stimulus. We suggest that seeing a facial expression, an emotional body expression or hearing an emotional tone of voice all activate the affect program corresponding to the emotion displayed.
Magnee, M. J., Stekelenburg, J. J., Kemner, C., & van Gelder, B. (2007). Similar facial electromyographic responses to faces, voices, and body expressions. Neuroreport, 18(4), 369-72. https://doi.org/10.1097/WNR.0b013e32801776e6