Sensorimotor communication in professional quartets Leonardo Badino a,1 , Alessandro D'Ausilio a,1 , Donald Glowinski b,d , Antonio Camurri b,1 , Luciano Fadiga a,c,n,1 a RBCS – Robotics, Brain and Cognitive Sciences Department, IIT – Istituto Italiano di Tecnologia, via Morego 30, 16163 Genoa, Italy b DIBRIS Department, University of Genoa, Genoa, Italy c Section of Human Physiology, University of Ferrara, Ferrara, Italy d NEAD-CISA, University of Geneva, Switzerland article info Available online 10 December 2013 Keywords: Music Quartets Joint action Kinematics Granger Sensorimotor Communication Causality Information flow Mirror neurons Motor control Social interaction Social neuroscience Leadership abstract Non-verbal group dynamics are often opaque to a formal quantitative analysis of communication flow. In this context, ensemble musicians can be a reliable model of expert group coordination. In fact, bodily motion is a critical component of inter-musician coordination and thus could be used as a valuable index of sensorimotor communication. Here we measured head movement kinematics of an expert quartet of musicians and, by applying Granger Causality analysis, we numerically described the causality patterns between participants. We found a clear positive relationship between the amount of communication and complexity of the score segment. Furthermore, we also applied temporal and dynamical changes to the musical score, known by the first violin only. The perturbations were devised in order to force unidirectional communication between the leader of the quartet and the other participants. Results show that in these situations, unidirectional influence from the leader decreased, thus implying that effective leadership may require prior sharing of information between participants. In conclusion, we could measure the amount of information flow and sensorimotor group dynamics suggesting that the fabric of leadership is not built upon exclusive information knowledge but rather on sharing it. & 2013 Elsevier Ltd. All rights reserved. 1. Introduction Other's action understanding requires a great deal of cognitive processing and efforts. Contextual information and prior know- ledge are necessary and often enough to build reliable infer- ences about other's intentions (Brass, Schmitt, Spengler, & Gergely, 2007). However, another source of critical information is the other's movement kinematics (Rizzolatti & Sinigaglia, 2010). Actions have sensory effects. We use the sensory effects for motor control purposes and for information signaling to other indivi- duals. Sensory effects of our actions are the only way another individual can “read” our intentions. The sender though, uses its motor system to encode such sensory messages. In this context, the mirror-matching hypothesis suggests that we use our motor knowledge as a template to match others' actions. In this manner, we might use our motor internal models to gain access to low- level control parameters implemented by the people interacting with us. Therefore, action understanding may benefit from the ability to model others' behavior implementation and use it as an additional prior, in a Bayesian perspective (Friston, Mattout, & Kilner, 2011). The importance of this source of information, to the general action understanding, may be subject to data availability (full body vision vs. occluded vision), context richness (known vs. novel context) or expertise in a given task (Rizzolatti & Sinigaglia, 2010). If on one hand it is clear that, in general, partly occluded vision or the presence of a reliable context reduces the impact of low level decoding of others' action kinematics, on the other hand the case of experts may offer a different and interesting perspective. In fact, sport, dance or music experts do not obtain a simple rough inter- pretation of others' intentions as a general gist of their motivations. Rather, expertise in these activities is all about modeling with extreme accuracy low-level features and timing of actions (Aglioti, Cesari, Romani, & Urgesi, 2008). In fact, professional musicians, for instance, undergo important plastic changes induced by extensive motor and sensory training (Elbert, Pantev, Wienbruch, Rockstroh, & Taub, 1995; Schlaug, Jäncke, Huang, & Steinmetz, 1995; Pantev et al., 1998; D'Ausilio, Altenmüller, Olivetti Belardinelli, & Lotze, 2006). These anatomo-functional changes are also paralleled by enhanced ability to discriminate subtle changes in others' performance via predictive action simulation (Knoblich & Flach, 2001; Wilson & Knoblich, 2005; D'Ausilio, Brunetti, Delogu, Santonico, and Belardinelli (2010); Candidi, Sacheli, Mega, & Aglioti, in press). Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/neuropsychologia Neuropsychologia 0028-3932/$ - see front matter & 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.neuropsychologia.2013.11.012 n Corresponding author at: RBCS – Robotics, Brain and Cognitive Sciences Department, IIT – Istituto Italiano di Tecnologia, via Morego 30,16163 Genoa, Italy. Tel.: þ39 010 7178467; fax: þ39 010 7170817. 1 These authors equally contributed to this work. Neuropsychologia 55 (2014) 98–104