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Conversational engagement predicts interpersonal neural synchrony

Poster Session D - Monday, March 9, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Peter C.H. Lam¹ (), Marcos E. Domínguez-Arriola¹, Alejandro Pérez², Marc D. Pell¹; ¹McGill University, ²Universidad de La Laguna

How is interpersonal connectedness reflected at the neural level? Previous joint-action studies have linked Inter-Brain Coupling (IBC) in the alpha band to synchronized attention/behaviors, whereas theta band IBC could reflect aligned cognitive strategies and shared intentions. Extending beyond highly controlled paradigms, our study investigated how two brains jointly facilitate naturalistic, spontaneous conversations. Specifically, we were interested in whether conversational engagement predicts IBC in the alpha and theta frequency bands. We recorded the dual-EEG (“hyperscanning”) of 24 dyads while they engaged in conversations on common topics, after which they provided behavioral ratings related to conversational engagement. For each electrode pair, we calculated instantaneous and listener-trailing (time lag ~170ms) IBC using Gaussian Copula Mutual Information. Then, for each type of IBC and frequency band, we fitted a linear mixed effects model to test whether IBC could be predicted by conversational engagement and at which region of interest (ROI). Our results revealed that conversational engagement significantly interacted with ROI in predicting both alpha instantaneous synchrony and theta listener-trailing coupling. Follow-up analyses showed that higher conversational engagement predicted greater instantaneous alpha IBC at ROI pairs involving the frontal areas, possibly reflecting the immediate, bottom-up alignment required for successful attentional and behavioral engagement. In contrast, higher conversational engagement was associated with lower theta listener-trailing IBC at the homologous medial-central ROI. This could indicate a more efficient cognitive alignment, with less effortful predictive processing required. Collectively, our study demonstrates that conversational quality is dynamically reflected in multiple facets of IBC.

Topic Area: EMOTION & SOCIAL: Emotion-cognition interactions