Tajfel's Minimal Group Experiments

Henri Tajfel and colleagues sorted participants into two groups on a deliberately trivial basis, such as a stated preference between two painters' work, then had each participant privately allocate points or money between anonymous members of the two groups identified only by a code number and their group label. Even though the groups meant nothing beyond the assignment itself and members never met or worked with anyone, participants reliably gave more to their own group's members than to the other group's, sometimes even when that meant a smaller total for their own side. The result showed that the mere act of being categorized into a group is enough to trigger in-group favoritism.