In joint action, multiple people coordinate their actions to perform a task together. This often requires precise temporal and spatial coordination. How do co-actors achieve this? How do they coordinate their actions toward a shared task goal? Here, we provide an overview of the mental representations involved in joint action, discuss how co-actors share sensorimotor information and what general mechanisms support coordination with others. By deliberately extending the review to aspects such as the cultural context in which a joint action takes place, we pay tribute to the complex and variable nature of this social phenomenon.

When performing joint actions, people modulate instrumental actions to provide additional information for a coactor (Pezzulo, Donnarumma, & Dindo, 2013). Similarly, demonstrators adjust instrumental actions to make them more informative for novice learners (Brand, Baldwin, & Ashburn, 2002). It is unknown whether the kinematic modulations performed to facilitate prediction in joint action coordination and the modulations performed to transmit information about the structure of novel actions are unique, or whether a general type of modulation can take on multiple functions. The present study therefore investigated whether there are unique kinematic markers for demonstration and for different types of joint action. In three experiments participants performed a virtual xylophone task, where they played simple xylophone melodies either alone, for a learner watching them, or together with another participant, while their movements were recorded. Participants increased movement amplitude during joint action and during demonstration. However, during joint action, participants modulated specific velocity parameters depending on whether their joint action partner knew or did not know the action sequence to be performed. The results demonstrate that there are specific kinematic cues to communicate the time and location of upcoming actions to a joint action partner but that there are no unique kinematic cues expressing the "pedagogical" intentions of a demonstrator. (PsycINFO Database Record

In joint performances spanning from jazz improvisation to soccer, expert performers synchronize their movements in ways that novices cannot. Particularly, experts can align the velocity profiles of their movements in order to achieve synchrony on a fine-grained time scale, compared to novices who can only synchronize the duration of their movement intervals. This study investigated how experts’ ability to engage in velocity-based synchrony affects observers’ perception of coordination and their aesthetic experience of joint performances. Participants observed two moving dots on a screen and were told that these reflect the hand movements of two performers engaging in joint improvisation. The dots were animated to reflect the velocity-based synchrony characteristic of expert performance (in terms of jitter of the velocity profile: Experiment 1, or through aligning sharpness of the velocity profile: Experiment 2) or contained only interval-based synchrony. Performances containing velocity-based synchrony were judged as more coordinated with performers rated as liking each other more, and were rated as more beautiful, providing observers with a stronger aesthetic experience. These findings demonstrate that subtle timing cues fundamentally shape the experience of watching joint actions, directly influencing how beautiful and enjoyable we find these interactions, as well as our perception of the relationship between co-actors.

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Joint actions often require agents to track others’ actions while planning and executing physically incongruent actions of their own. Previous research has indicated that this can lead to visuomotor interference effects when it occurs outside of joint action. How is this avoided or overcome in joint actions? We hypothesized that when joint action partners represent their actions as interrelated components of a plan to bring about a joint action goal, each partner’s movements need not be represented in relation to distinct, incongruent proximal goals. Instead they can be represented in relation to a single proximal goal – especially if the movements are, or appear to be, mechanically linked to a more distal joint action goal. To test this, we implemented a paradigm in which participants produced finger movements that were either congruent or incongruent with those of a virtual partner, and either with or without a joint action goal (the joint flipping of a switch, which turned on two light bulbs). Our findings provide partial support for the hypothesis that visuomotor interference effects can be reduced when two physically incongruent actions are represented as mechanically interdependent contributions to a joint action goal.

Countless everyday activities require us to coordinate our actions and decisions with others. Coordination not only enables us to achieve instrumental goals, but has also been shown to boost commitment, leading people to persevere with an interaction even when their motivation wavers. So far, little is known about the mechanism by which coordination generates commitment. To investigate this, we conducted two experiments which represented very different coordination problems: coordination of movement timing on a joint drumming task (Experiment 1) and coordination of decision-making on a joint object matching task (Experiment 2). In both experiments, the similarity of the participant and partner was manipulated by varying whether or not they had perceptual access to the participant’s workspace, and the participants’ attribution of (un)willingness to invest effort into the joint action by adapting was manipulated by varying whether or not the participant believed their partner had perceptual access. As a measure of commitment, we registered how much participants’ persisted on a boring and effortful task to earn points for their partners. Participants were significantly less committed to earning points for unadaptive partners than for adaptive partners, but only when they believed that their partner was unwilling to adapt rather than unable to adapt. This demonstrates that coordination can generate commitment insofar as it provides a cue that one’s partner is willing to invest effort to adapt for the good of the interaction. Moreover, we demonstrate that this effect generalises across different kinds of coordination.

Depersonalisation is a common dissociative experience characterised by distressing feelings of being detached or ‘estranged’ from one’s self and body and/or the world. The COVID-19 pandemic forcing millions of people to socially distance themselves from others and to change their lifestyle habits. We have conducted an online study of 622 participants worldwide to investigate the relationship between digital media-based activities, distal social interactions and peoples’ sense of self during the lockdown as contrasted with before the pandemic. We found that increased use of digital media-based activities and online social e-meetings correlated with higher feelings of depersonalisation. We also found that the participants reporting higher experiences of depersonalisation, also reported enhanced vividness of negative emotions (as opposed to positive emotions). Finally, participants who reported that lockdown influenced their life to a greater extent had higher occurrences of depersonalisation experiences. Our findings may help to address key questions regarding well-being during a lockdown, in the general population. Our study points to potential risks related to overly sedentary, and hyper-digitalised lifestyle habits that may induce feelings of living in one’s ‘head’ (mind), disconnected from one’s body, self and the world.