Research:
When a class of 14-year-old boys was split into arbitrary groups and assigned random tasks, from simple ones to more competitive with monetary value, even though they could have friends outsidetheir formed groups, the boys formed strong alliances. Eventually, in a situation in which they could make a profit, let all groups make a profit, or make a profit while other groups would suffer a loss, the boys not only wanted to succeed but also other groups to fail.