Motor resonance evoked by observation of subtle nonverbal behavior.

This study was designed to combine two, otherwise separated, fields of research regarding motor resonance and mimicry by adopting a naturalistic mimicry paradigm while probing motor resonance with transcranial magnetic stimulation (TMS). At stake was whether the motor system resonates instantaneously with unobtrusive nonverbal behavior of another person. We measured excitability in the left and right hand while participants viewed sequences of video clips and static images. In the video clips an actor performed several clerical tasks, while either inconspicuously touching his face (face-touching (FT) condition) or not (no face-touching (NFT) condition). We found that excitability was higher in the FT condition than in the NFT and baseline conditions. Furthermore, our data showed a general heightened excitability in the left motor cortex relative to the right. Taken together, the results suggest that observed hand-face gestures--even though outside the primary focus of attention and occurring inconspicuously throughout an ongoing action setting--can cause instantaneous resonant activity in the observer's motor system. It thus supports the idea of motor resonance involvement in mimicry and demonstrates that this can be studied using a naturalistic mimicry paradigm.