The Robbers' Cave study was conducted over a period of three weeks. The first week involved creating two distinct groups of boys and allowing them to bond and form group identities. In the second week, the researchers introduced competition between the two groups by setting up a tournament with a prize for the winning group. This competition led to an increase in negative attitudes and behaviors towards the out-group (the other group). In the third week, the researchers attempted to reduce the prejudice by introducing activities that required the two groups to work towards a common goal. This cooperation led to a decrease in prejudice and improved inter-group relations. Overall, the study demonstrated the powerful impact of inter-group competition on prejudice and the potential for cooperation to reduce prejudice.