ABSTRACT
Social identity, understood as an individual’s sense of identification with and emotional attachment to a group, is widely regarded as a potent instrument to boost cooperation with others. However, groups are normally constructed in terms of what social psychologists call ‘ingroups’ and ‘outgroups’ (Brewer 1999), or what anthropologists call an ‘ethnic psychology’ (Henrich and Henrich 2007), that is, the tendency to treat favorably members of one’s own group but to treat unfavorably outsiders. Such ‘we’ vs. ‘them’ mentality may be at the same time a strong trigger of cooperation within the ingroup but detrimental for cooperation across outgroups (Choi and Bowles 2007). This would be particularly worrisome for global cooperation, which calls for joint action on a planetary scale and thus involves widely dispersed and culturally different outgroups to come together for the common good.
