Social and goal-related foundations of interpersonal adaptation during joint action

Collaborative motor interactions ( joint actions) require relating to another person (social dimension) whose contribution is needed to achieve a shared goal (goal-related dimension).We explored if and how these dimensions modulate interactive behavior by exploring posterror interpersonal adaptations. In two experiments carried out in 2022 (N1= 23; N1= 24, preregistered), participants played sequences of notes in turn-taking with a coactor either described as another participant or the computer (human vs. nonhuman coactor, social manipulation) while pursuing shared or individual goals (goal-related manipulation). The coactor was programmed to make a mistake in 50% of the trials. We found that, only in the shared goal condition, participants were slower when interacting with a human than a nonhuman coactor depending on how strongly they believed the human coactor was a real participant. Moreover, the general slowdown following a partner’s error was absent when the action required from the participant corresponded to what the coactor should have done (correction tendency effect). This effect was found only in the shared goal condition without differences between coactors, suggesting it was driven by goal-related representations. The social and goal-related dimensions thus independently but significantly shape interpersonal adaptations during joint action.