How are neural, behavioural and social scales coordinated in real time so as to make possible the emergence of social cognition? Answering this question requires that we study the dynamics of coordination in real human interactions. However, even at the simplest dyadic scale, methodological and theoretical challenges remain. First, we will see how situated social paradigms combined with brain recordings of multiple individuals simultaneously (hyperscanning) allow us to demonstrate how states of interactional synchrony at the behavioural level correlate with the emergence of inter-individual synchronisation at the brain level. Then, we will discuss the Human Dynamic Clamp (HDC), a paradigm integrating equations of human motion at the neurobehavioral level in a virtual partner. Overall, we will discuss how combining human-human and human-machine interactions thus presents new approaches for investigating the neurobiological mechanisms of social interaction, and for testing theoretical/computational models concerning the dynamics at the neural, behavioural, and social scales.