Are people predisposed to favor their own groups at the expense of others, even when the group distinction is completely arbitrary? This activity replicates, more or less, the exact experiment used by Henri Tajfel to demonstrate the "minimal group paradigm" used in Social Identity Theory. Students receive a handout with matrices listing different values that their side of the auditorium (the in-group) would receive and that the other side (the out-group) would receive. They work in groups to consider which column maximizes the in-group profit, which maximizes the joint profit, and which maximizes the difference between groups. Afterward, they discuss as a class. See "Resources" for the corresponding lecture and handouts.