Neuro-cognitive and social components of dyadic motor interactions revealed by the kinematics of a joint-grasping task

This thesis describes a PhD project is based on the notion that we live our whole life dipped into an interactive social environment where we observe and act together with others and where our behavior is influenced by first sight impressions, social categorizations and stereotypes which automatically and unavoidably arise during interactions. Nevertheless, the bidirectional impact of interpersonal coding on dyadic motor interactions has never been directly investigated. Moreover, the neurocognitive bases of social interaction are still poorly understood. In particular, in every-day dyadic encounters we usually interact with others in non-imitative fashions (Sebanz et al. 2006), challenging the hypothesis of a direct matching between action observation and action execution within one system (“common coding approach”, Prinz 1997), which is instead supported by neurophysiological data on the so called “mirror neurons”(Rizzolatti and Sinigaglia 2010) which fire both during action execution and observation of similar actions performed by others. Suggestion is made that what characterizes joint action is the presence of a common goal (i.e. the “shared” goal, Butterfill 2012) which organizes individuals’ behaviour and channel simulative processes. During her PhD, Lucia Sacheli developed a novel interactive scenario able to investigate face-to-face dyadic interactions within a naturalistic and yet controlled experimental environment, with the aim to build a more coherent model of the role of simulative mechanisms during social interaction and on the role of socio-emotional variables in modulating these processes. This scenario required pairs of participants to reciprocally coordinate their reach-to-grasp movements and perform on-line mutual adjustments in time and space in order to fulfill a common (motor) goal. So far, she demonstrated by means of kinematic data analysis that simulation of the partner’s movement is task-dependent (Sacheli et al. 2013) and modulated by the interpersonal relationship linking co-agents (Sacheli et al. 2012) and by social stereotypes as ethnic biases (Sacheli et al. under review). Moreover, she used the same scenario to investigate the different contribution of the parietal and frontal nodes of the fronto-parietal “mirror” network during joint-action by means of Transcranial Magnetic Stimulation combined with analysis of kinematics.