Us and them: Anticipated imitation between groups.

People's propensity to imitate others' actions is well documented. However, research on imitation remains mainly focused on dyadic social interactions, disregarding that we often interact with others as parts of larger groups. Extending sparse research on imitation beyond dyadic interactions, the current study investigated how anticipated imitation effects become modulated in social interactions between groups. Participants performed an anticipated imitation task in a virtual environment depicting four animated hands that were controlled by the participant, a virtual co-actor, and two virtual agents of an opposing dyad, respectively. Participants responded to symbolic stimuli by lifting their index or middle finger and performed the task either with or without their co-actor, while either one or both agent(s) of the opposing dyad imitated their responses. Our findings revealed partial evidence that participants' task performance was affected by congruency relations between groups: Acting together with another co-actor was facilitated when both vs. one agent(s) of the opposing dyad imitated participants' responses, while the opposite trend emerged when participants performed the task without their co-actor. However, this group-level congruency effect was only evident for two out of four analyzed performance measures. Further explorative analysis showed that this effect was moderated by participants' general response speed and was obscured by participants who responded relatively fast on the task. Our findings indicate that anticipated responses of multiple interaction partners can play a causal role in controlling one's own contributions to a social interaction and provide novel evidence that joint task representations encode actions on a group level.