Demographic differences are associated with temporal variation in cardiac and electrodermal interpersonal synchrony.

Interpersonal physiological synchrony is known to foster group cohesion and collaboration. In this study, weexamined how demographic diff erences among group members (gender, religiosity, and nationality) relate tophysiological synchrony during the earliest phases of group interaction. Four hundred and thirty-eight participants,organized into 146 triads across three experimental paradigms (drumming, decision-making, and word assembly),engaged in an initial baseline non-interactive phase followed by an interactive joint task. Synchrony was quantifi edin two physiological measures - Interbeat intervals (IBI) and electrodermal activity (EDA). Our fi ndings revealincreased EDA levels among triads with greater demographic diff erences during a baseline phase, even before overtsocial interaction commences. Moreover, a dual eff ect of demographic diff erences emerged: Greater diff erenceswere associated with diminished EDA synchrony during the baseline (but not during the interactive phase), and withdiminished IBI synchrony during the interaction phase (but not during the baseline). These results suggest thatdemographic diff erences relate to distinct physiological systems in complex specifi c ways, refl ecting both an initialshared arousal and subsequent challenges in coordinated engagement. Our study advances understanding of howearly demographic diff erences shape biobehavioral foundations of group dynamics, with implications for improvingcohesion and performance in heterogeneous settings.