When Mere Categorization Hurts: Aggressive Responding Under the Minimal Group Paradigm

In the context of intergroup aggression, it is becoming understood that the minimal group paradigm (MGP; Tajfel et al., 1971) does not lead to increased aggression towards out-group members compared to in-group members. This issue is partly due to the difficulty in distinguishing between aggression and non-cooperation based on payoff structures. This study focuses on intentional aggressive behavior, defining it not only through payoff structures, which involve reducing the opponent's gains at one's own cost, but also through aggression labels ("Attack" or "Keep"). We investigated the MGP effect on aggression through three experiments (N = 1495; two pre-registered). The results from Experiments 1 and 2 indicated that MGP manipulation showed that MGP manipulation increased aggression toward out-group members Experiment 3, which included a computational model, showed decreased threats from the opponent’s attack and spite motivation towards ingroup members. Finally, these findings highlight the importance of using frames and labels to interpret behavior in aggression research.