In the target article, Glowacki draws on ethnographic studies to identify potential determinants of peaceful intergroup interactions. Although such studies provide rich descriptions with high external validity, they are less suited to causal inferences about the internal (e.g., dispositions and motives) and external (e.g., structural incentives) determinants of peaceful intergroup relations.

We argue that the use of economic games can effectively address these shortcomings, thereby providing a complementary tool for researchers studying the individual and institutional determinants of peace in humans. Economic games, particularly intergroup or team games (Bornstein, Reference Bornstein2003), can serve as models of real-world contexts by replicating their incentive structures in closely regulated experimental environments (Guala, Reference Guala2005; Thielmann, Böhm, Ott, & Hilbig, Reference Thielmann, Böhm, Ott and Hilbig2021). This affords the opportunity to investigate how participants with diverse characteristics (e.g., in terms of group-based social preferences; Choi & Bowles, Reference Choi and Bowles2007; Columbus, Thielmann, Zettler, & Böhm, Reference Columbus, Thielmann, Zettler and Böhm2023) respond to varying structural conditions (e.g., costs and benefits of war and peace, respectively; target article, sect. 2). By employing economic games, it is possible to capture and disentangle the independent and joint causal effects of these factors in influencing peaceful intergroup conduct.

Previous research studying intergroup relations with economic games has mainly focused on conflict rather than peace, probably due to the higher salience of conflict. The workhorse of experimental studies of intergroup relations has long been the intergroup prisoner's dilemma (Bornstein, Reference Bornstein1992). In this game, participants have a choice between selfishness and cooperation, which benefits their in-group and harms the out-group. Experimental studies using this and similar games indicate that individuals are willing to bear personal costs to benefit their in-group vis-à-vis the out-group when facing intergroup conflict (e.g., Bornstein, Reference Bornstein1992; Bornstein & Ben-Yossef, Reference Bornstein and Ben-Yossef1994), particularly when their in-group is threatened by the out-group (Böhm, Rusch, & Gürerk, Reference Böhm, Rusch and Gürerk2016; De Dreu et al., Reference De Dreu, Gross, Méder, Giffin, Prochazkova, Krikeb and Columbus2016). This has been taken as evidence that humans prefer to benefit in-groups and to harm out-groups (Choi & Bowles, Reference Choi and Bowles2007). However, when group members are given the opportunity to increase the in-group's welfare without harming the out-group (i.e., peaceful ignorance) – as modeled in the intergroup prisoner's dilemma-maximizing difference game – the majority prefers to do so (e.g., Halevy, Bornstein, & Sagiv, Reference Halevy, Bornstein and Sagiv2008; Weisel & Böhm, Reference Weisel and Böhm2015).

The difference in behavior between the standard intergroup prisoner's dilemma and the intergroup prisoner's dilemma-maximizing difference highlights that the choice set available in a game constrains how participants can behave toward the out-group. An overall restrictive choice set can lead to false conclusions – such as inferring that participants are motivated to harm out-groups when they would prefer to peacefully ignore or even cooperate with the out-group. Even in the intergroup prisoner's dilemma-maximizing difference game, peace in Glowacki's sense – sustained positive-sum intergroup relationships – is simply not possible. This may lead researchers to overlook human preferences for peaceful interactions.

To address this limitation, recent research has devised extended variants of the intergroup prisoner's dilemma-maximizing difference game that additionally allow for peaceful cooperation, that is, costly contributions to benefit both the in-group and the out-group. When adding such an option in the intergroup parochial and universal cooperation game, Aaldering and Böhm (Reference Aaldering and Böhm2020) found that roughly half of the contributions that otherwise would have been contributed to peaceful ignorance is contributed to peaceful cooperation instead.

Intergroup games also make it possible to test the role of individual differences in peaceful behavior under varying structural incentives. For example, Aaldering and Böhm (Reference Aaldering and Böhm2020) found that peaceful cooperation was positively related to individual differences in prosocial intent (i.e., higher levels in honesty–humility and social value orientation; Ashton & Lee, Reference Ashton and Lee2009; Murphy, Ackermann, & Handgraaf, Reference Murphy, Ackermann and Handgraaf2011) and negatively related to social dominance orientation (Pratto, Sidanius, Stallworth, & Malle, Reference Pratto, Sidanius, Stallworth and Malle1994), whereas peaceful ignorance was positively related to empathic concern (Batson & Shaw, Reference Batson and Shaw1991). These results suggest that there are specific individual differences related to different types of peaceful behaviors.

We call for further research to develop economic game paradigms that help to examine the very nature of peaceful motivations and behaviors in intergroup interaction. The intergroup parochial and universal cooperation game may be a useful starting point and its parameters can be varied to test predictions of Glowacki's account and from the related multidisciplinary literature on peace and conflict, for example, about the relative costs and benefits of peace and conflict (including punishment, reward, and potential differences in incentives within groups), social norms, signaling, power hierarchies, and leadership (and what characterizes those individuals who advocate for peace). For instance, to investigate how groups establish peace versus conflict, one could model groups whose members face varying incentives for peaceful versus harmful intergroup behaviors. Adding the possibility to punish their in-group members for specific contributions then allows to causally identify the structural conditions under which peace or conflict becomes the dominant social norm. Taken together, economic games can build the bridge between theoretical models and ethnographic studies to understand the formation and stability of peaceful intergroup relations.