Wired for Corruption: Inter-Brain Synchrony Encodes Bribery-Related Value Information and Predicts Bribery Agreement

Bribery typically arises in power-asymmetric interpersonal interactions requiring immoral collaboration between a briber and a power-holder. While previous research has predominantly adopted a single-person aspect, the neurocognitive foundation of its collaborative nature remains largely unexplored. In this study (N = 112), we combined a novel dyadic behavioral paradigm, computational modeling, and functional near-infrared spectroscopy hyperscanning to investigate the cognitive mechanisms and inter-brain synchrony (INS) involved in bribery decision-making. Anonymous pairs participated in a multiround coin-guessing game involving two roles. Players could propose offers to earn rewards immorally (Bribery) or morally (Control), and judges decided whether to accept them. INS in the bilateral prefrontal cortex (PFC) and right temporoparietal junction (rTPJ) were measured during decision-making. Behaviorally, fewer deals were reached in the Bribery condition, as computational modeling showed that the moral costs of bribery devalued both self-interest and the counterparts' gains. Neurally, distributed INS patterns in the PFC and rTPJ specifically represented bribery-related value information. Additionally, bribery-specific INS features-particularly those associated with moral cost, later decision phases, and rTPJ-accurately forecasted the overall bribery agreement rate across dyads. These findings highlight frontoparietal INS as a key neural marker of coordinated bribery-related information processing, advancing understanding of the neurobiological underpinnings of interpersonal corruption.