br Conclusions br Acknowledgements br

Conclusions
Acknowledgements
Introduction Our daily life contains a multitude of social interactions in which we coordinate our actions with others. The involvement of the mirror system in action perception, monitoring, and prediction (e.g., Bekkering et al., 2009; Kilner et al., 2007; Southgate et al., 2009; Stapel et al., 2010) is thought to help us prepare and execute our own actions in coordination with others (Kourtis et al., 2013; Sebanz et al., 2006). Converging neuroimaging evidence has shown that our motor system becomes activated both when performing an action, and when observing an action (Marshall and Meltzoff, 2011; Rizzolatti and Craighero, 2004; Rizzolatti and Fogassi, 2014). This neural overlap between action production and perception has been called neural mirroring (e.g., Hari and Kujala, 2009). It has been suggested that neural mirroring provides the neurocognitive basis for processing others’ actions and therefore plays a crucial role in successful interpersonal coordination during social interaction (Bekkering et al., 2009; Hari and Kujala, 2009). Previous findings support this Nutlin3a of a close relation between neural mirroring and interpersonal coordination. For instance, adults who showed more motor system involvement when observing a partner’s movements in a finger tapping task also coordinated their movements better with the partner (Naeem et al., 2012). While imitative actions occur during social interaction, especially complementary actions are relevant in which individuals perform different actions (Bekkering et al., 2009), for example when passing and catching a ball. Complementary actions were also related to motor involvement of the neural motor areas during action observation (Ménoret et al., 2014). Comparable findings are present for children, as young children who mirrored an adult action partner more than another adult in a turn-taking game made fewer errors in interpersonal coordination during that game (Meyer et al., 2011). Similarly, recently, Filippi et al. (2016) found that elevated levels of mirroring in 7-month-old infants predicted their imitation of others’ toy choices. These findings support a link between neural mirroring and interpersonal coordination within the same laboratory task. However, the degree to which interindividual differences in neural mirroring support the success in various instances of social interaction is unknown. While the role of interindividual differences in neural mirroring for interpersonal coordination is unclear, studies of social cognition (e.g., empathy, perspective taking) highlight a role of mirroring for social skills that are not task-specific. In adults, neural mirroring is related to higher levels of perspective taking (Woodruff et al., 2011), empathy (Gazzola et al., 2006; Hooker et al., 2010; Kaplan and Iacoboni, 2006), and social competence as assessed with questionnaires (Pfeifer et al., 2008). In this study, we investigated whether interindividual differences in neural mirroring also might play a role in interpersonal coordination during social interactions outside the specific task. In social interaction, two types of interpersonal coordination occur often: cooperation and entrainment. While in cooperation, coordination is planned and typically involves a goal-directed task, in entrainment, coordination emerges spontaneously without a joint goal (Knoblich et al., 2011). For instance, soccer players cooperate by keeping track of each other and adjusting their positions accordingly to obtain the ball and shoot it at the goal. During applause, on the other hand, people entrain by coordinating their clapping behavior spontaneously. In cooperation, it is important to monitor others’ actions with respect to the achievement of the common goal. In entrainment the focus rather is on the monitoring of the others’ movements. Importantly, both the observation of movements and goal-directed actions were found to activate the human mirror system (Rizzolatti and Craighero, 2004; Rizzolatti and Fogassi, 2014). Therefore, we expected that higher levels of mirroring would be related to both higher levels of cooperation and entrainment situations outside the specific mirroring task.