Influence of interpersonal personality traits on cooperative and competitive behavior in transparent dyadic interactions

Balancing self-interest against mutual benefit is central to social life, yet classical economic games capture only discrete, turn-based decisions missing the reciprocal dynamics of real interaction. Here we used a transparent Dyadic Interaction Platform and Cooperation–Competition Foraging task in which pairs of participants jointly or individually collected variable-payoff targets while continuously observing each other's gaze, ongoing actions, and outcomes. Using a round-robin design (N = 125 participants), we examined how Interpersonal Circumplex traits and prior dyadic history shaped real-time strategic outcomes. Dyads rapidly converged on stable cooperative, mixed or competitive strategies within sessions, and showed increasing cooperation in subsequent sessions as compared to the first session both participants played. Strategies in earlier sessions predicted later ones, indicating experience-dependent adaptation. Higher mean Communion predicted greater cooperation, higher mean Agency predicted greater competition. Critically, dyadic minima for Communion and maxima for Agency outperformed dyadic means, revealing an asymmetry in which competitive tendencies exert disproportionate influence on interaction dynamics. These findings demonstrate that continuous, transparent paradigms uncover how stable personality traits and interaction history jointly shape social strategy, bridging game-theoretic models with ecologically valid accounts of social decision-making.