Triandis and colleagues (1988) found that in/out-group relationships were highly correlated with individualistic and collectivistic values of cultures. Members of individualistic cultures belong to multiple in-groups and move easily from in-group to in-group. People from individualistic cultures were not attached to any one single in-group because they belong to many different groups. Additionally, members were more likely to treat out-group persons more equally, with less distinction between in-groups and out-group. Individuals from collectivistic cultures tended to belong to fewer in-groups than individualistic cultures but had much greater commitment to the groups they belong to.
Consider, if a group leader (e.g., politician, chief, religious figure) has to decide between providing financial support for one program or another. She may be more likely to give resources to the group that more closely represents her own in-group. This psychological process, of being more comfortable with people like yourself, can have important and lasting consequences for the out-group members. In-group favoritism (preferences for the in-group) is found for many different types of social groups, in many different settings, on many different dimensions, and in many different cultures (Bennett et al., 2004; Pinter & Greenwald, 2011). In-group favoritism also occurs on trait ratings, such that in-group members are rated as having more positive characteristics than are out-group members (Hewstone, 1990).
Van de Vliert (2011) examined in-group favoritism using three major components that shape culture: ecology, resources and people (Chapter 2). Using data from almost 180 countries, in-group favoritism was highest in cultures with the lowest income and harshest most demanding climates (e.g., extreme heat or cold) and lowest in cultures with high national income and demanding climates. By examining ecology, national wealth and group preferences collectively, rather than individually, a picture begins to emerge that suggests in-group favoritism likely co-evolved with culture, as groups adapted to survive ecological challenges with limited resources.