Egocentric belief attribution enables the modeling of higher level Theory of Mind during group interactions

Modeling the belief hierarchy in group interactions is challenging due to the fact that behavior of a group member is usually driven by more than one belief, which makes the tracking of all others’ beliefs impossible. We propose that in such cases, attributing one’s own beliefs to others (i.e., egocentric belief attribution) may serve as a functional approximation, enabling the modeling of belief hierarchy. In this study, we employed computational modeling to investigate this approach in a novel group resource-sharing task across three experiments. We found that, beyond the well-documented reciprocity, participants exhibited consistent alternating behavior, characterized by the switching between potential recipients. This alternation was not driven by fairness concerns but reflected a strategic balance between maintaining stable partnerships and exploring alternatives. Crucially, a reinforcement learning model incorporating Theory of Mind (ToM) consistently outperformed all alternative models. These findings highlight the critical role of ToM in social decision-making and suggest that mentalizing others’ intentions may be essential for effective resource sharing and social bond formation.