Loss contexts enhance dorsolateral prefrontal interpersonal neural synchrony during successful human deceptive recommendations.

Deception is an important social behavior because it can shape another person's choices while concealing the sender's true interests. Although people often respond differently when trying to gain rewards or avoid losses, it remains unclear how these contexts influence the shared brain processes that support deception during real interaction. Here we show that loss contexts make deception more frequent and more successful in human face-to-face communication. We study same-gender stranger dyads (18 female dyads) while sender gives recommendations that can either help or mislead the other under gain and loss contexts. Using functional near-infrared spectroscopy to record brain activity from both people at the same time, we find that misleading recommendations in gain contexts are associated with stronger activity in the dorsolateral prefrontal cortex, a frontal brain region involved in control and planning. In contrast, successful deception in loss contexts is associated with higher interpersonal brain synchrony in this region, defined as a greater increase in similarity between the two people's brain activity during interaction compared with rest. This synchrony predicts deception success, suggesting that deception depends on context-sensitive alignment between interacting brains.