In the process of individual moral judgment, group identity significantly influences decision-making, leading to two distinct phenomena: in-group favoritism and the "Black Sheep Effect." While children often show favoritism toward in-group members, they sometimes treat them more harshly. The precise conditions under which children shift from in-group favoritism to the stricter "Black Sheep Effect" remain unclear, particularly regarding how specific features of moral violations—such as the repetition of violations and the representativeness of violators—moderate this shift. Guided by Social Identity Theory and Subjective Group Dynamics Theory, this study systematically investigated the moral judgments and punishment behaviors of 5- to 8-year-old children under different violation contexts—specifically, repetitive violations and violations by representative group members—and examined the underlying motivations.

Three experiments were conducted. In all experiments, children watched animated video scenarios depicting moral violations. Experiment 1 employed a 2 (Group Identity: In-group vs. Out-group) × 2 (Violation Type: Single vs. Repeated) × 2 (Age: 5-6 vs. 7-8 years) mixed design. A total of 128 children watched videos depicting in-group or out-group members committing either a single or repeated moral violation (taking pencils from a donation box). Punishment intensity was measured by the number of reward stickers deducted. Experiment 2 adopted a 2 (Group Identity: In-group vs. Out-group) × 2 (Representativeness: Representative vs. Non-representative) × 2 (Age: 5-6 vs. 7-8 years) mixed design with 124 participants. The representativeness of a puppet character (e.g., a class monitor and role model vs. an ordinary member) was manipulated via verbal descriptions prior to the violation. This experiment compared how children reacted to violations committed by highly representative group members (e.g., class monitors) versus ordinary group members. Experiment 3 used a within-subjects design with 61 children aged 7-8 years to investigate whether punishment motivations (consequentialist vs. retributive) differ between in-group and out-group violators. After making their punishment decisions, children rated their agreement with statements reflecting consequentialist (e.g., hoping for improvement) and retributive (e.g., believing they deserved it) motives. Data were analyzed using paired-samples t-tests, chi-square tests, and ANOVA.

The results revealed that: First, the interaction between violation context and group identity significantly influenced punishment. In single-violation contexts, 5- to 6-year-olds displayed in-group favoritism, punishing out-group members more severely. In repeated-violation contexts, children aged 5-8 consistently demonstrated the "Black Sheep Effect," punishing in-group violators more harshly, with the difference increasing with age. Notably, 7- to 8-year-olds showed no in-group bias in single-violation contexts, punishing both groups equally. Second, the representativeness of the violator amplified this effect. Children imposed the strongest punishment on representative in-group violators, with over 80% such violations as more severe. Third, punishment of in-group members was primarily driven by consequentialist motives (hoping for improvement), with significantly higher scores for in-group than out-group targets, while retributive motivations did not differ significantly between groups.

In conclusion, moral judgment and punishment in 5- to 8-year-olds are context dependent and develop with age. Repeated violations and the representativeness of the violator are key triggers of the "Black Sheep Effect." The stricter punishment of in-group violators is essentially driven by a consequentialist desire to "improve the group," reflecting a mindset of "strict with one's own, lenient with others." Younger children (5-6 years) are more influenced by in-group favoritism in single-violation contexts, whereas older children (7-8 years) pay greater attention to the nature of the act itself, overcoming group bias. This developmental pattern suggests a transition from a simpler "in-group preference" strategy to a more nuanced, norm-upholding approach to group membership. These findings demonstrate a developmental shift in children's moral reasoning, from a simple "in-group preference" to a more sophisticated enforcement of group norms, offering new theoretical insights and empirical evidence for moral education and the fostering of group responsibility.