Hostile attribution bias shapes neural synchrony in the left ventromedial prefrontal cortex during ambiguous social narratives

Hostile attribution bias refers to the tendency to interpret social situations as intentionally hostile. While previous research has focused on its developmental origins and behavioral consequences, the underlying neural mechanisms remain underexplored. Here, we employed fNIRS to investigate the neural correlates of hostile attribution bias. While undergoing fNIRS, male and female participants listened to and provided attribution ratings for 21 hypothetical scenarios where a character's actions resulted in a negative outcome for the listener. Ratings of hostile intentions were averaged to obtain a measure of hostile attribution bias. Using intersubject-representational similarity analysis, we found that participants with similar levels of hostile attribution bias exhibited higher levels of neural synchrony during narrative listening, suggesting shared interpretations of the scenarios. This effect was localized to the left ventromedial prefrontal cortex (VMPFC), and was particularly prominent in scenarios where the character's intentions were highly ambiguous. We then grouped participants into high and low bias groups based on a median split of their hostile attribution bias scores. A similarity-based classifier trained on the neural data classified participants as having high or low bias with 75% accuracy, indicating that the neural time courses during narrative listening was systematically different between the two groups. Furthermore, hostile attribution bias correlated negatively with attributional complexity, a measure of one's tendency to consider multifaceted causes when explaining behavior. Our study sheds light on the neural mechanisms underlying hostile attribution bias and highlights the potential of using fNIRS to develop non-intrusive and cost-effective neural markers of this socio-cognitive bias. Significance Statement Inferring the intentions from behavior is crucial for adaptive social functioning. A predisposition towards interpreting intentions as hostile is a significant predictor of interpersonal conflict and aggressive tendencies. Using fNIRS, we found that individual differences in hostile attribution bias shaped neural synchrony in the VMPFC while processing real-world social situations. Additionally, we were able to distinguish between participants with high and low hostile attribution bias from neural activity time courses. These results reveal how subjective interpretations of social situations are influenced by hostile attribution bias and reflected in the temporal dynamics of the VMPFC. Our findings lay the groundwork for future studies aimed at understanding the neurobiological basis of socio-cognitive biases, as well as interventions aimed at mitigating these biases.