Automatic imitation is the finding that movement execution is facilitated by compatible and impeded by incompatible observed movements. In the past 15 years, automatic imitation has been studied to understand the relation between perception and action in social interaction. Although research on this topic started in cognitive science, interest quickly spread to related disciplines such as social psychology, clinical psychology, and neuroscience. However, important theoretical questions have remained unanswered. Therefore, in the present meta-analysis, we evaluated seven key questions on automatic imitation. The results, based on 161 studies containing 226 experiments, revealed an overall effect size of g = 0.95, 95% CI [0.88, 1.02]. Moderator analyses identified automatic imitation as a flexible, largely automatic process that is driven by movement and effector compatibility, but is also influenced by spatial compatibility. Automatic imitation was found to be stronger for forced choice tasks than for simple response tasks, for human agents than for nonhuman agents, and for goalless actions than for goal-directed actions. However, it was not modulated by more subtle factors such as animacy beliefs, motion profiles, or visual perspective. Finally, there was no evidence for a relation between automatic imitation and either empathy or autism. Among other things, these findings point toward actor-imitator similarity as a crucial modulator of automatic imitation and challenge the view that imitative tendencies are an indicator of social functioning. The current meta-analysis has important theoretical implications and sheds light on longstanding controversies in the literature on automatic imitation and related domains. (PsycINFO Database Record

A large body of research has provided evidence for the idea that individuals simulate the actions of others in their motor system. However, this research has focused almost exclusively on dyadic situations, hence ignoring the fact that social situations often require that the actions of multiple persons are simulated simultaneously. In the current study, we addressed this issue by means of a widely used automatic imitation task. In Experiment 1, it is shown that individuals automatically imitate the actions of 2 agents at the same time. More specifically, the results indicate that 2 identical observed movements produce a stronger imitation effect, whereas 2 different observed movements produce 2 opposite imitation effects that cancel each other out. In Experiment 2, it is shown that the effects obtained in Experiment 1 cannot be explained in terms of attentional capture. Instead, the results point toward an explanation in terms of ideomotor theory. The finding that observers simultaneously represent the actions of multiple agents in their motor system allows for a better understanding of social interaction beyond the dyad.

Although social situations regularly involve multiple persons acting together, research on the mirror neuron system has focused on situations in which a single agent is observed. Therefore, the goal of the current study was to explore the role of the mirror mechanism in situations involving multiple agents. Specifically, we used transcranial magnetic stimulation (TMS) to investigate whether mirror activation is modulated by the number of observed agents. Based on group contagion research, we hypothesized that multiple agents would provide a stronger trigger to the motor system and would therefore produce a stronger mirror response than a single agent. Participants observed movements performed by a single hand or by two hands while TMS was applied to the primary motor cortex. The results confirmed that activation in the motor system was stronger for two hands. This suggests that input to the motor system increases as the number of agents grows. Relating back to group contagion, our study suggests that groups may be more contagious simply because their actions resonate louder. Given that the mirror mechanism has been linked to a variety of social skills, our findings additionally have important implications for the understanding of social interaction at the group level.

Social-psychological research has suggested that being imitated changes the way that we experience others: We like someone who imitates us more, and the interaction with this person runs more smoothly. Whether being imitated also affects basic social reactions, such as empathy for pain, is an open question. Empathy for pain refers to the observation that perceiving another person in pain results in pain-related brain activation in the observer. The aim of the present study was to combine the two lines of research, to investigate whether being imitated can influence empathy for pain. To this end, we developed an experimental approach combining an imitation task with a pain perception task. Subjective reports, as well as physiological responses, indicated that being imitated enhances affective responses to seeing someone else in pain. Furthermore, using rubber hand illusion measures, we provided evidence for the role of shared representations in the sensory and motor domains as a core underlying mechanism. In this way, our study integrated social-psychological research on being imitated with cognitive research on empathy for pain. This has broad implications, since imitation plays a crucial role in our daily social interactions, and our study provides insights into a basic cognitive mechanism that might underlie these social situations.

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