Philip zimbardo devised a simulated prison and randomly assigned college students to serve as prisoners or guards. this experiment best illustrates the impact of:

Role assignment. By assigning certain people more superior roles (in this situation, the guard) they began to treat the "Prisoners" as inferiors. The guards started physically abusing the prisoners. Eventually, the experiment had to be ended, but it provided a lot of insight into how role assignment can affect a person's actions.