‘‘In-Group Love’’ and ‘‘Out-Group Hate’’ in Repeated Interaction Between Groups

Costly individual participation in intergroup conflict can be motivated by ‘‘in-group love’’—a cooperative motivation to help the in-group, by ‘‘out-group hate’’—an aggressive or competitive motivation to hurt the out-group, or both. This study employed a recently developed game paradigm (Halevy, Bornstein, & Sagiv, 2008) designed specifically to distinguish between these two motives. The game was played repeatedly between two groups with three players in each group. In addition, we manipulated the payoff structure of the interaction that preceded the game such that half of the groups experienced peaceful coexistence and the other half experienced heightened conflict prior to the game. Enabling group members to express in-group love independently of out-group hate significantly reduced intergroup conflict. Groupmembers strongly preferred to cooperate within their group, rather than to compete against the out-group for relative standing, even in the condition in which the repeated game was preceded by conflict. Although both ‘‘in-group love’’ and ‘‘out-group hate’’ somewhat diminished as the game continued (as players becamemore selfish), choices indicative of the formermotivation were significantly more frequent than choices indicative of the latter throughout the interaction. We discuss the implications of these findings for conflict resolution. Copyright # 2011 John Wiley & Sons, Ltd. key words intergroup conflict; in-group love; out-group hate; absolute and relative gains; repeated games From the individual’s perspective, participation in largescale intergroup conflicts (e.g., war) is plainly irrational. The cost of participation (e.g., risk of injury or death) is high, the effect it can possibly have on the conflict’s outcome is negligible, and, if one’s group does win the conflict, the benefits (e.g., territory) are public goods shared by all group members regardless of whether they have paid the cost of participation (Bornstein, 1992, 2003; Dawes, 1980; Gould, 1999). Nevertheless, individual participation in intergroup conflicts is rational, indeed essential, from the group’s point of view. Since ‘‘the probability that a group wins a conflict depends on the difference in the number of fighters in the two groups’’ (Choi & Bowles, 2007, p. 637), a group that fails to mobilize sufficient individual participation will most likely lose the competition, and its members, participants and nonparticipants alike, will bear the costs of defeat. To overcome this fundamental gap between the collective interest of the group and the interests of its individual members, groups employ powerful ‘‘solidarity mechanisms’’ (e.g., Campbell, 1965, 1972; Levine & Campbell, 1972), designed, or evolved through cultural group selection (e.g., Bernhard, Fischbacher, & Fehr, 2006; Boyd, Gintis, Bowles, & Richerson, 2003), to uphold individual willingness to ‘‘fight and die’’ for the in-group. Regrettably, the more effective groups are in mobilizing individual participation, the more destructive is the conflict between them. As noted by Baron (2001), war is ‘‘zero sum except for the effort expended in competition itself’’ (p. 85), and all individuals on both sides would be better off if they all refused to take any part in it. From the collective point of view universal defection (and the ensuing peace) is clearly the best state of affairs. To model these relations between individual, group, and collective interests, Bornstein (1992, 2003) introduced the Intergroup Prisoner’s Dilemma (IPD) game (see also Baron, 2001; Bornstein & Ben-Yossef, 1994; Probst, Carnevale, & Triandis, 1999). The IPD game is exemplified here as a competition between two groups, with three members in each group. Each player receives an endowment of two money units (MUs) and can either keep the endowment or contribute it to a common pool. For each contribution, each in-group member, including the contributor, gains 1MU and each out-group member loses 1MU. This simple game captures the key strategic properties of large-scale intergroup conflicts as described above. Because the individual’s return from contributing a 2MU endowment is only 1MU, the unconditionally best (i.e., dominant) individual strategy is to withhold contribution (i.e., defect). However, because contribution generates a total of 3MUs for the in-group while costing it only 2MUs, the dominant group strategy is for all group members to contribute. Finally, since the in-group’s gain from contribution is exactly offset by the out-group’s loss, contribution is a net waste of 2MUs from the collective point of view. The collectively optimal strategy, the one that maximizes the payoff of both groups and all players, is for all players to defect. What motivates individual behavior in intergroup conflict as modeled by the IPD game, where ‘‘action in favor of one’s group is beneficial for the group but costly to both the individual and the world’’ (Baron, 2001, p. 285)? Individual contribution (i.e., participation) can be motivated Journal of Behavioral Decision Making, J. Behav. Dec. Making (2011) Published online in Wiley Online Library (wileyonlinelibrary.com) DOI: 10.1002/bdm.726 The first and second properties of the IPD game define the gamewithin each group as an N-person (three-person in our example) PD game. The second and third properties define the game between the two groups as a two-person PD game. *Correspondence to: Nir Halevy, Graduate School of Business, Stanford University, 518 Memorial Way, Stanford, CA 94305-5015, USA. E-mail: [email protected] Copyright # 2011 John Wiley & Sons, Ltd. by in-group love—a cooperative desire to help the in-group. But it can also result from out-group hate—an aggressive motivation to hurt the out-group, or a competitive motivation to increase the in-group’s advantage over the out-group (Brewer, 1999; cf. Arrow, 2007; Bernhard et al., 2006). In the IPD game where one must hurt the out-group to help the ingroup (and vice versa), in-group love and out-group hate are indistinguishable. The motivation underlying individual defection is similarly ambiguous. Defection can be motivated by narrow self-interest, but it can also reflect a true concern for the collective welfare of all players in both groups. In the IPD game, as in the social reality that it models, free riding and pacifism (or universalism) are impossible to tell apart. To remove these ambiguities, Halevy et al. (2008) devised a variation of the IPD game, called the Intergroup Prisoner’s Dilemma—Maximizing Difference (IPD-MD) game. In the IPD-MD game, group members can direct their contributions to either of two pools: A ‘‘between-group’’ pool, which, as in the IPD game, increases the payoffs to each in-group member by 1MU and decreases the payoff to each out-group member by 1MU; and a ‘‘within-group’’ pool which increases the payoffs to each in-group member by 1MU but has no effect on the out-group (see also: De Dreu et al., 2010; Halevy, Chou, Cohen, & Bornstein, 2010). Providing group members with the option of helping the in-group without hurting the out-group reveals the social preferences underlying their potential choices. Defection is now plainly selfish and can no longer be confused with a concern for the collective welfare. Contribution to the within-group pool (pool W) is a clear indication of in-group love—the cooperative motivation to increase the in-group’s payoff. Contribution to the between-group pool (pool B) can only be motivated by out-group hate—the aggressive motivation to hurt the out-group (or the competitive motivation to increase the in-group’s relative payoff). Strictly speaking, if players care only about their in-group’s welfare and completely disregard that of the out-group, they should be indifferent between the two pools. We make the reasonable assumption, however, that players will choose to hurt the out-group (by contributing to pool B) if and only if they derive some positive utility from doing so. Players who gain nothing from the out-group’s losses will intentionally refrain from contributing to the competitive pool. The dynamics of intergroup interaction Studying the one-shot IPD-MD game, Halevy et al. (2008) found substantial evidence for in-group love but little indication of out-group hate. On average, players in their experiment contributed about 50% of their endowment to pool W, and only 6% to pool B. Moreover, when in-group members were allowed pre-play communication, contribution to poolW increased to almost 70%, while contribution to pool B remained at a low 4%. Clearly, group members, both alone and as a group, chose to maximize the group’s absolute outcome rather than its outcome relative to that of the out-group. They chose to do so even though in the oneshot setting they could disadvantage the out-group at no additional cost or risk of retaliation. The present experiment extends Halevy et al.’s study by studying repeated interaction in the IPD-MD game. In reality, intergroup relations are rarely static and typically involve numerous interactions between the same parties over a (possibly long) period of time. This is the case, for example, with rivalry between fans of different sport teams, members of rival political parties, or the citizens of neighboring countries engaged in hostilities (e.g., the Israeli–Palestinian conflict). Repeated play is profoundly different from one-shot play as it enables the players to employ contingent or reciprocal strategies—strategies that depend on earlier choices of the other players (e.g., tit-for-tat, Axelrod, 1984; Heide & Meiner, 1992; Murnighan & Roth, 1983). As a result, behavior that is irrational in the one-shot game may be rational when the game is repeated and the set of mutually rational (i.e., equilibrium) outcomes becomes larger. Since in the two-level (Putnam, 1988) IPD-MD game reciprocation can take place both within and between the groups, three distinct outcomes of this dynamic process are theoretically possible. One potential outcome—intragroup cooperation—is characterized by a high level of cooperation within the groups and little or no competition between the groups. This outcome is the best from the collective point of view of both groups and all individuals. When all players contribute to pool W and no one contributes to pool B, each earns 3MUs. Another possible outcome— intergroup competition— involves a high level of competition between the groups. This is the worst possible result from the collective point of view. When all the players contribute to pool B they each earn nothing. The escalation of intergroup conflict to a full scale ‘‘war’’ can result, as it often does in reality, from group members treating even small contributions to pool Bmade by the out-group (contributions that might very well be errors due to a ‘‘trembling hand’’) as provocative acts of aggression, and retaliating in kind (Gould, 1999). Finally, a third outcome that has to be considered is universal defection. A consistent finding in public-good experiments is that cooperation declines with time. This decay of cooperation is often attributed to a breakdown of trust, where ‘‘strong reciprocators’’ (Gintis, 2000)—group members who are willing to cooperate with cooperative others—are dragged by a minority of free-riders to the equilibrium of zero cooperation. A decline in cooperation can also be a result of individual learning—another process made possible by the dynamic nature of the repeated game. The learning hypothesis assumes that not all players immediately grasp the strategic properties of the stage game and some only learn to play the dominant, free-riding, strategy as they gain more experience. Since different players Individual participation in intergroup conflict modeled by the IPD game was found to be higher than that in a single-group PD gamewith an identical payoff structure (Baron, 2001; Bornstein & Ben-Yossef, 1994; Probst et al., 1999). This increased willingness to contribute in the intergroup game as compared with the single-group game reflects ‘‘parochial altruism’’—selfsacrificial behavior that benefits in-group members while hurting out-group members (De Dreu et al., 2010). Copyright # 2011 John Wiley & Sons, Ltd. J. Behav. Dec. Making (2011) DOI: 10.1002/bdm Journal of Behavioral Decision Making