Facial mimicry depends on the emotion we recognize in others’ faces

Rapid facial reaction (RFR), also known as facial mimicry, plays an important role in the synchronisation of expressions and associated emotions among individuals. RFR was originally understood as a form of pure motion mimicry (matched motor hypothesis), while there is counterevidence suggesting that RFR does not merely involve an imitation of the motion. We investigated the existence of a top-down effect on RFR by measuring the motion in facial muscles with electromyography while perceiving faces with different emotions in their upper and lower half (Experiment 1). In the conditions of upper anger (anger in the upper half of the face) and lower happiness (happiness in the lower half of the face), the participants frowned more when they recognised the ambiguous face as angry, while they smiled more when recognising the face as happy. This result suggests a top-down effect of emotional recognition on RFR. We also measured RFR when seeing upper-only or lower-only facial images (Experiment 2). While the result supported the top-down effect in the occurrence of RFR, it also suggested that the mouth regions, and not the eye regions, are key to inducing RFR. These findings aid in further understanding social interaction at an unconscious and physical level.