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.

Many people find it hard to change their dietary choices. Food choice often occurs impulsively, without deliberation, and it has been unclear whether impulsive food choice can be experimentally created. Across 3 exploratory and 2 confirmatory preregistered experiments we examined whether impulsive food choice can be trained. Participants were cued to make motor responses upon the presentation of, among others, healthy and sustainable food items. They subsequently selected these food items more often for actual consumption when they needed to make their choices impulsively as a result of time pressure. This effect disappeared when participants were asked to think about their choices, merely received more time to make their choices, or when choosing required attention to alternatives. Participants preferred high to low valued food items under time pressure and without time pressure, suggesting that the impulsive choices reflect valid preferences. These findings demonstrate that it is possible to train impulsive choices for food items while leaving deliberative choices for these items unaffected, and connect research on attention training to dual-process theories of decision making. The present research suggests that attention training may lead to behavioral change only when people behave impulsively. (PsycINFO Database Record

HighlightsIn joint action tasks, co-actors have a choice between different coordination mechanisms.How joint actions are coordinated depends on shared perceptual information.In the absence of shared visual information, co-actors rely on a general heuristic strategy.When shared visual information is available, co-actors switch to a communicative strategy.

In many joint actions, knowledge about the precise task to be performed is distributed asymmetrically such that one person has information that another person lacks. In such situations, interpersonal coordination can be achieved if the knowledgeable person modulates basic parameters of her goal-directed actions in a way that provides relevant information to the co-actor with incomplete task knowledge. Whereas such sensorimotor communication has frequently been shown for spatial parameters like movement amplitude, little is known about how co-actors use temporal parameters of their actions to establish communication. The current study investigated whether systematic modulations of action duration provide a sufficient basis for communication. The results of 3 experiments demonstrate that knowledgeable actors spontaneously and systematically adjusted the duration of their actions to communicate task-relevant information if the naïve co-actor could not access this information in other ways. The clearer the communicative signal was the higher was the benefit for the co-actor's performance. Moreover, we provide evidence that knowledgeable actors have a preference to separate instrumental from communicative aspects of their action. Together, our findings suggest that generating and perceiving systematic deviations from the predicted duration of a goal-directed action can establish nonconventionalized forms of communication during joint action. (PsycINFO Database Record

Previous research has demonstrated that humans tend to represent each other's tasks even if no interpersonal coordination is required. The present study asked whether coactors in a joint action rely on task co-representation to achieve temporal coordination even if this implies increased movement effort for an unconstrained actor. Pairs of participants performed reaching movements back and forth between two targets, with the aim of synchronizing their landing times. One of the participants needed to move over an obstacle while the other had no obstacle. The results of four experiments showed that the participant without obstacle moved as if an obstacle was obstructing her way. Further amplifying the demands on interpersonal coordination led to a significant increase of this effect, indicating that unconstrained actors represented their coactor's task constraint and adjusted their own actions accordingly, particularly under high coordination demands. The findings also showed that unconstrained actors represented the object property constraining their coactor's movement rather than parameters of this movement. We conclude that joint action partners rely on task co-representation to achieve temporal coordination in a task with asymmetric task constraints. (PsycINFO Database Record