Human interactions are often improvised rather than scripted, which suggests that efficient coordination can emerge even when collective plans are largely underspecified. One possibility is that such forms of coordination primarily rely on mutual influences between interactive partners, and on perception–action couplings such as entrainment or mimicry. Yet some forms of improvised joint actions appear difficult to explain solely by appealing to these emergent mechanisms. Here, we focus on collective free improvisation, a form of highly unplanned creative practice where both (...) agents' subjective reports and the complexity of their interactions suggest that shared intentions may sometimes emerge to support coordination during the course of the improvisation, even in the absence of verbal communication. In four experiments, we show that shared intentions spontaneously emerge during collective musical improvisations, and that they foster coordination on multiple levels, over and beyond the mere influence of shared information. We also show that musicians deploy communicative strategies to manifest and propagate their intentions within the group, and that this predicts better coordination. Overall, our results suggest that improvised and scripted joint actions are more continuous with one another than it first seems, and that they differ merely in the extent to which they rely on emergent or planned coordination mechanisms. (shrink)

Joint actions typically involve a sense of togetherness that has a distinctive phenomenological component. While it has been hypothesized that group size, hierarchical structure, division of labour, and expertise impact agents’ phenomenology during joint actions, the studies conducted so far have mostly involved dyads performing simple actions. We explore in this study the complex case of collectively improvised musical performances, focusing particularly on the way group size and interactional patterns modulate the phenomenology of joint action. We recorded two expert improvisation (...) ensembles of contrasting sizes and collected data about their musical behaviour, as well as reports about five aspects of their phenomenology and about their musical intentions. Our overall data enabled us to assess how those five phenomenological dimensions related to one another during jointly improvised performances. They also show how such phenomenology varied with the way improvisers dynamically related to one another throughout the performance. Finally, we observe that group size strongly altered the phenomenology of improvisers who otherwise shared many characteristics. Our study thus sheds light on the interactional and structural parameters that shape and modulate our felt experience when acting together, and thereby highlights the importance of pluralism for studying the phenomenology of joint action. (shrink)