Reading out bodily cues to predict interactions

Successful motor coordination in social interactions requires the rapid interpretation of others’ intentions from their actions. Previous research suggests that individuals use early bodily cues, such as movement kinematics and gaze, to predict others’ behaviour. However, the motor features critical for signaling or decoding potential motor interactions remain unclear. In this study, we measured the kinematics of a basic motor act — grasping an object — executed with either individualistic (to place) or social (to pass) intentions. Subsequently, we conducted two action prediction tasks to identify bodily markers of (social) intentions. Hand positioning on the object emerged as a key kinematic indicator of the intention to interact with a partner, as shown by kinematic analyses and classification of participants’ responses. Eye-tracking analysis revealed the face as the most attended feature during action observation. Notably, these cues were more consistently attended to when observing actions from a frontal — second-person — perspective rather than a lateral — third-person — perspective. Our findings identify distinct markers of social intentions in motor acts, including goal-oriented hand-object interactions and facial signals. They also highlight the saliency of these features in decoding potential engagement in motor interactions, possibly linked to social affordance processing.