Extensive experiments in Human Movement Science suggest that solo motions are characterized by unique features that define the individuality or motor signature of people. While interacting with others, humans tend to spontaneously coordinate their mo
vement and unconsciously give rise to joint improvisation. However, it has yet to be shed light on the relationship between individuality and joint improvisation. By means of an ad-hoc virtual agent, in this work we uncover the internal mechanisms of the transition from solo to joint improvised motion in the mirror game, a simple yet effective paradigm for studying interpersonal human coordination. According to the analysis of experimental data, normalized segments of velocity in solo motion are regarded as individual motor signature, and the existence of velocity segments possessing a prescribed signature is theoretically guaranteed. In this work, we first develop a systematic approach based on velocity segments to generate emph{in-silico} trajectories of a given human participant playing solo. Then we present an online algorithm for the virtual player to produce joint improvised motion with another agent while exhibiting some desired kinematic characteristics, and to account for movement coordination and mutual adaptation during joint action tasks. Finally, we demonstrate that the proposed approach succeeds in revealing the kinematic features transition from solo to joint improvised motions, thus revealing the existence of a tight relationship between individuality and joint improvisation.
