Our society is organized in many different groups, such as classroom groups, sports teams or circles of friends. We have a very strong tendency to form groups with others and take these groups very seriously. Even when we have never met our group members before, we tend to like them more than members of other groups. For example, already at the beginning of a new school year, children often prefer their classmates to the children who go to other classrooms or schools.
In this study, we investigate the origins of this phenomenon. One possibility is that this tendency helps us to get ready to work together with our group members. To test this hypothesis, children are allocated into one of two color groups and are told that they will now play with their group members. In the experimental condition, due to "technical problems", the child cannot play with the in-group members, but has to collaborate with children from the other group instead. We then measure whether children's preference for their own group persists, or whether their preference shifted to their outgroup members to prepare them for the upcoming collaboration.