LAUSR

The evolution of parochial altruism goes hand in hand with intergroup conflict. Helping other group members is evolutionary stable in the presence of an outside threat (Bowles et al., 2003; Guzmán et al., 2007), and hostility toward other groups can evolve together with parochial altruism (Choi and Bowles, 2007; Bowles, 2008). Furthermore, group reputation fosters cooperation with fellow group members in times of conflict—even in an environment that does not foster cooperation in times of peace (Hugh-Jones and Zultan, 2013). Social scientists have long documented that intergroup conflict increases intragroup cooperation (Sumner, 1906; Williams, 1947; Simmel, 1955; Coser, 1956). Over a century ago, Sumner (1906) wrote that “the exigencies of war with outsiders are what makes peace inside.” Indeed, prosocial behaviors, such as volunteering and blood donations, increase during times of war or exposure to terror attacks (Schmiedeberg, 1942; Janis, 1951; Glynn et al., 2003; Penner et al., 2005; Steinberg and Rooney, 2005; Gneezy and Fessler, 2012; Berrebi and Yonah, 2016). This phenomenon can be reproduced in experimental settings, either under experimentally induced external threat to the group (Wright, 1943; Feshbach and Singer, 1957; Sherif, 1961, 1966; Burnstein and McRae, 1962; Hargreaves-Heap and Varoufakis, 2002), or in times of interstate conflict (Gneezy and Fessler, 2012). Democratic leaders are also apparently aware of this phenomenon, often dubbed the common enemy effect, as they are more likely to initiate interstate conflict at times of internal unrest or threatened leadership (Sirin, 2011). In this paper, we argue that outside threat has the capacity to both increase and decrease intragroup cooperation. We propose that the crucial psychological variable that determines the response to outside threat is the level at which threat is perceived and construed. Outside threat increases cooperation only if it menaces the group as a whole (Williams, 1947). As intergroup conflict poses a threat both to the group as a whole and to individual group members, the same threat can trigger different—and even opposing—responses, depending on how it is perceived. These perceptions are sensitive to the duration and intensity of the conflict, media coverage, and the salience of various aspects of intergroup conflict. This Perceived Target of Threat principle can be summed thus: individuals who perceive the group to be under threat help the group, whereas an individual who perceives himself to be under threat helps himself (Weisel and Zultan, 2016). In the following, we review empirical support for this principle and discuss its psychological antecedents.