关键词: 规范执行, 心理理论, 群体偏好, 公平, 错误信念

Abstract: Third-party intervention is a key mechanism for upholding social norms, yet its application often varies across group contexts. While children develop fairness concerns and group identities early in life, the cognitive mechanisms underlying the determination of norm-enforcement boundaries remain unclear. This study investigates how the development of False Belief Theory of Mind (FB ToM) allows preschoolers to transition from undifferentiated fairness enforcement to boundary-sensitive intervention. We tested two competing hypotheses: whether the development of FB ToM leads to a universal application of fairness norms (Universal Sensitivity Hypothesis), or whether it fosters a nuanced understanding of social jurisdiction (Norm-Boundary Sensitivity Hypothesis), where children selectively uphold norms within their own group boundaries. The study involved 212 Chinese preschoolers (107 boys, Mage = 5.57 ± 0.54 years) across two experiments. Social-cognitive development was assessed using a standardized first-order False Belief Theory of Mind (FB ToM) task. Group identity was established via the minimal group paradigm based on children’s color preference. The primary measure was an online gamified third-party intervention task where children, as observers, watched two gender-matched characters, Feifei (the allocator) and Tongtong (the receiver), distribute game coins. Children deCIded whether to “accept” the distribution (where game coins were awarded as proposed) or “reject” it as a third party by sending all coins to a “trash can” at no personal cost. In Study 1, 106 children (56 boys, Mage = 5.59 ± 0.56 years) observed unfair allocations between two characters of the same group, either both ingroup or both outgroup to examine internal group fairness norms. In Study 2, another 106 children were assigned to two mixed-group subconditions to disentangle the independent effects of allocator and recipient group identity: 53 children (25 boys, Mage = 5.66 ± 0.53 years) viewed unfair distributions perpetrated by an outgroup allocator against an ingroup recipient, while the remaining 53 children (26 boys, Mage = 5.43 ± 0.51 years) observed unfair allocations committed by an ingroup allocator targeting an outgroup recipient. Meanwhile, children’s decision-making motivations were measured using a forced-choice task after the intervention trials. Motivations were categorized into fairness execution, apathy, and norm differentiation to explore the psychological mechanisms behind children’s intervention. Results demonstrated that FB ToM development did not lead to a universal enforcement of fairness. Instead, children who passed the FB ToM task demonstrated group-sensitive intervention patterns: they consistently intervened in any unfairness involving ingroup members, regardless of whether the ingroup member was the transgressor or the victim, but exhibited significantly lower intervention rates in scenarios involving only outgroup members. In contrast, children who did not pass the FB ToM task showed no significant differentiation in their intervention behavior across group contexts. Motivation analysis further suggested that the decreased intervention in outgroup scenarios among FB ToM-passers reflected a recognition of the limits of norm applicability rather than social apathy. In conclusion, these findings suggest that FB ToM is important for relational moral reasoning. Rather than merely balancing conflicting drives, FB ToM enables children to integrate fairness principles with social structures, allowing them to identify the normative boundaries of their community. This research reframes selective intervention not as a moral bias, but as a cognitive achievement in recognizing the limits of social intervention and the specialized nature of ingroup shared norms. These insights are vital for understanding how children learn to navigate the complex balance between universal values and the practical boundaries of social cooperation.

Key words: norm enforcement, theory of mind, group preference, fairness, false belief