Forewarned Is Forearmed: The single- and dual-brain mechanisms in Detectors from Dyads of Varying Social Distance During Deceptive Outcomes Evaluation

Preventing deception requires understanding how lie detectors process social information across social distance. Although the outcomes of such information are crucial, how detectors evaluate gains or losses from close versus distant others remains unclear. This study uses a sender-receiver task and functional Near-Infrared Spectroscopy hyperscanning to investigate receivers (e.g. detector) how perceived social distance modulates intra- and inter-brain neural basis during deceptive gain-loss evaluations. The result showed that detectors were more prone to deception with friend in gain contexts, with these differences mediated by connectivity in risk-assessment (Dorsolateral Prefrontal Cortex, DLPFC), reward-processing (Orbitofrontal Cortex, OFC), and intention understanding regions (Frontal Pole Area, FPA). Further hyperscanning analyses revealed that friend dyads exhibited higher interpersonal neural synchrony (INS) in these regions compared with stranger dyads. In gain contexts, friend dyads showed enhanced INS in the OFC, whereas in loss contexts, enhanced INS in the DLPFC. Multiple regression and Support Vector Regression (SVR) revealed that INS provides superior predictive power over single-brain measures. The INS-based SVR model achieved 86.66% accuracy in predicting deception. This indicates that increased trust at closer social distances reduces vigilance and fosters relationship-oriented social information processing. As the first to identify INS as a neural marker for deception from the detector’s perspective, this work advances Interpersonal Deception Theory and offers a neuroscientific basis for credit risk management.