Neural Representations of Unfolding Dyadic Actions Reflect Preceding Action-Course Information

During interpersonal interaction, understanding others’ actions requires the brain to continuously integrate information as behavior unfolds. Yet an action may deviate from its expected course and subsequently be corrected, raising the question of whether neural representations reflect only its eventual outcome or also retain information about how it developed. Here, we recorded electroencephalography from 20 expert table tennis players and 21 novices observing dyadic actions involving uninterrupted success, successfully corrected deviations, or goal-disrupting deviations. These conditions allowed us to distinguish information about an action’s preceding course from its eventual outcome. We combined time-resolved neural decoding, temporal generalization, and representational similarity analysis to characterize the differentiation and organization of unfolding actions. Neural activity differentiated the three action courses, with motor expertise selectively modulating their neural separability and temporal generalization. Critically, in experts, neural representational geometry corresponded to the shared preceding deviation of corrected and goal-disrupting actions despite their different outcomes. This correspondence remained significant after controlling for competing theoretical models and low-level visual and motion similarity. These findings suggest that neural representations of others’ actions incorporate information about their preceding course beyond their immediate observable state, highlighting how the brain preserves action history during unfolding dyadic actions.