The question of why animals, humans and robots should or do engage in social learning or social matching behaviour has at least two major answers: learning and communicative interaction (Užgiris, 1981). The link between the motivations for imitative behaviour and development are the common theme of the two chapters in this section of the book. The former, acquisition of new behaviours via observational learning (Bandura, 1977), has been better studied, the latter motivation for behaviour matching less so, but it clearly plays a communicative role when turn-taking, role-taking, being imitated and topic-sharing occur in communicative social interactions of pre-verbal young children (Nadel et al., 2002), compare Part V, Synchrony and turn-taking as communicative mechanisms, in this volume.

Psychologists Mark Nielsen and Virginia Slaughter discuss results on the development in human children of different types of imitative capacities including immediate, deferred and synchronic imitation, and the capacity to imitate after having observed incomplete or failed behaviours. Following Užgiris and Nadel, they discuss the development of imitation for interactive and communicative functions, where imitation is ‘conceived fundamentally as a social act’, as opposed to its role in skill learning. They assess evidence from their own experiments and the studies of others on imitation as a communicative mechanism. Here imitation serves to initiate and maintain social engagement, for example, in turn-taking games. The importance of various factors such as attention to actions or attention to the model, as well as vocal imitation are also discussed.