Abstract
Humans are skilled at inferring emotions and intentions from the observation of others’ actions. One influential explanation for this perceptual capability is action simulation theory, which proposes that we understand body language by internally simulating, or recreating, others’ movements with our own sensorimotor systems. Supporting this idea, studies using electroencephalography (EEG) have reported that both executing movements oneself and observing the actions of others are associated with reductions in the power of the mu rhythm, a neural oscillation (8-14 Hz) over sensorimotor cortex. However, reports of “mu suppression” for action observation have been inconsistent, perhaps because most previous studies have measured mu suppression over a limited number of sensors in small samples of participants. Here we collected data in a sample of 46 participants using high-density 128-channel EEG, which we combined with previously collected data for a total sample of 98 individuals. We compared mu suppression while participants performed a motor execution task (finger tapping) and viewed point-light displays (PLDs) of whole-body movements. Consistent with previous studies, we found a significant correlation between motor execution and suppression of the mu rhythm over central sensors. However, results for observing PLDs of others’ movements were inconsistent: whereas 51% of participants displayed typical mu suppression, others showed enhancement (23%) or no differences in power (26%). These results were not explained by differences in performance on an attentional monitoring task. Thus, action simulation does not appear to be a necessary component of body movement perception. Future research should explore potential factors underlying individual differences in action simulation, such as measures of cognitive ability and explicit knowledge of nonverbal cues.