Others' facial and bodily expressions of emotion modulate willingness to engage in joint action - but actions and objects matter too.

Emotions are fundamental to social cognition, yet their role in joint action remains underexplored. This study examined how emotional expressions (angry, sad, happy, and neutral) influence behavioural readiness (willingness to engage) in an object-handover task. Across two experiments, participants rated their willingness to "give" or "take" an object (spoon or knife) while viewing dynamic point-light displays (PLDs) of facial (Experiment 1) or bodily (Experiment 2) expressions. Results showed that, although both modalities influenced willingness, guided social decision-making relied on distinct functional heuristics. For facial expressions, a strong emotion-action congruency effect emerged: positive expressions facilitated prosocial "giving", whereas anger, a direct threat cue, inhibited willingness to engage, particularly when paired with a dangerous object. In contrast, bodily expressions were interpreted through a lens of physical vulnerability and predictability. For example, sad and neutral bodies elicited high willingness, suggesting they were perceived as low-threat or stable. Notably, across both experiments, self-directed "take" actions overrode emotional cues, indicating that personal goals may diminish sensitivity to others' expressions. These findings suggest that facial and bodily cues are not functionally equivalent. Rather, they provide complementary social information (intent vs. readiness) that uniquely shapes coordination in joint action contexts.