Automatic facial reactions to facial, body, and vocal expressions: A stimulus-response compatibility study

When perceiving emotional facial expressions there is an automatic tendency to react with a matching facial expression. A classic explanation of this phenomenon, termed the matched motor hypothesis, highlights the importance of topographic matching, that is, the correspondence in body parts, between perceived and produced actions. More recent studies using mimicry paradigms have challenged this classic account, producing ample evidence against the matched motor hypothesis. However, research using stimulus-response compatibility (SRC) paradigms usually assumed the effect relies on topographic matching. While mimicry and SRC share some characteristics, critical differences between the paradigms suggest conclusions cannot be simply transferred from one to another. Thus, our aim in the present study was to directly test the matched motor hypothesis using SRC. Specifically, we investigated whether observing emotional body postures or hearing emotional vocalizations produces a tendency to respond with one's face, despite completely different motor actions being involved. In three SRC experiments, participants were required to either smile or frown in response to a color cue, presented concurrently with stimuli of happy and angry facial (experiment 1), body (experiment 2), or vocal (experiment 3) expressions. Reaction times were measured using facial EMG. Whether presenting facial, body, or vocal expressions, we found faster responses in compatible, compared to incompatible trials. These results demonstrate that the SRC effect of emotional expressions does not require topographic matching. Our findings question interpretations of previous research and suggest further examination of the matched motor hypothesis.