Motor Expertise Modulates Neural Differentiation of Unfolding Action Courses During Dyadic Interaction

During dyadic interaction, another person’s unfolding action may proceed successfully as expected, succeed after correction, or ultimately fail, with different implications for how the observer should respond. It remains unclear whether the brain differentiates these action courses while the interaction is still unfolding and whether extensive dyadic motor experience sharpens this differentiation. Here, we recorded EEG from expert table tennis players and novices while they observed three-stroke interactions containing uninterrupted success, corrected success, or unsuccessful action. Experts showed a stronger ERP distinction between corrected success and unsuccessful action than novices. Time-frequency and multivariate analyses further revealed temporally evolving and decodable information about action course, particularly in experts, although expertise-related enhancement was not consistent across measures. Experts were more accurate overall in predicting landing location, but this behavioral advantage did not vary across action courses. These findings show that unfolding action courses can be neurally differentiated during dyadic observation and that extensive motor experience selectively sharpens some of these distinctions. More broadly, neural monitoring during dyadic interaction appears sensitive to how another person’s action develops and to its relevance for how the interaction is likely to continue.