  Joint improvisation is observed to emerge spontaneously among humans
performing joint action tasks, and has been associated with high levels of
movement synchrony and enhanced sense of social bonding. Exploring the
underlying cognitive and neural mechanisms behind the emergence of joint
improvisation is an open research challenge. This paper investigates the
emergence of jointly improvised movements between two participants in the
mirror game, a paradigmatic joint task example. A theoretical model based on
observations and analysis of experimental data is proposed to capture the main
features of their interaction. A set of experiments is carried out to test and
validate the model ability to reproduce the experimental observations. Then,
the model is used to drive a computer avatar able to improvise joint motion
with a human participant in real time. Finally, a convergence analysis of the
proposed model is carried out to confirm its ability to reproduce the emergence
of joint movement between the participants.
