Muzafer Sherif is a famous social psychologist important to the psychological understanding of groups and its members.
His main contribution is known as Realistic Conflict Theory, and accounts for group conflict, negative prejudices, and stereotypes as being the result of competition between groups for desired resources. Sherif validated his theory in one his most famous experiments, "The Robber's Cave"
Sherif argued that intergroup conflict (i.e. conflict between groups) occurs when two groups are in competition for limited resources. This theory is supported by evidence from a famous study investigating group conflict: The Robbers Cave (Sherif, 1954, 1958, 1961).
The field experiment involved two groups of twelve-year-old boys at Robber’s Cave State Park, Oklahoma, America.
The twenty-two boys in the study were unknown to each other and all from white middle-class backgrounds. They all shared a Protestant, two-parent background. None of the boys knew each other prior to the study. The boys were randomly assigned to one of two groups, although neither was aware of the other’s existence. They were then, as individual groups, picked up by bus on successive days in the summer of 1954 and transported to a 200 acre Boy Scouts of America camp in the Robbers Cave State Park in Oklahoma.
At the camp the groups were kept separate from each other and were encouraged to bond as two individual groups through the pursuit of common goals that required co-operative discussion, planning and execution. During this first phase, the groups did not know of the other group's existence. The boys developed an attachment to their groups throughout the first week of the camp, quickly establishing their own cultures and group norms, by doing various activities together like hiking, swimming, etc. The boys chose names for their groups, The Eagles and The Rattlers, and stenciled them onto shirts and flags.
Sherif now arranged the Competition Stage where friction between the groups was to occur over the next 4-6 days. In this phase it was intended to bring the two groups into competition with each other in conditions that would create frustration between them. A series of competitive activities (e.g. baseball, tug-of-war etc.) were arranged with a trophy being awarded on the basis of accumulated team score. There were also individual prizes for the winning group such as a medal and a multi-bladed pocket knife with no consolation prizes being given to the "losers."
The Rattlers' reaction to the informal announcement of a series of contests was absolute confidence in their victory! They spent the day talking about the contests and making improvements on the ball field, which they took over as their own to such an extent that they spoke of putting a "Keep Off" sign there! They ended up putting their Rattler flag on the pitch. At this time, several Rattlers made threatening remarks about what they would do if anybody from The Eagles bothered their flag.
Situations were also devised whereby one group gained at the expense of the other. For example, one group was delayed getting to a picnic and when they arrived the other group had eaten their food.
At first, this prejudice was only verbally expressed, such as taunting or name-calling. As the competition wore on, this expression took a more direct route. The Eagles burned the Rattler's flag. Then the next day, the Rattler's ransacked The Eagle's cabin, overturned beds, and stole private property. The groups became so aggressive with each other that the researchers had to physically separate them.
During the subsequent two-day cooling off period, the boys listed features of the two groups. The boys tended to characterize their own in-group in very favorable terms, and the other out-group in very unfavorable terms.
Keep in mind that the participants in this study were well-adjusted boys, not street gang members. This study clearly shows that conflict between groups can trigger prejudice attitudes and discriminatory behavior. This experiment confirmed Sherif's realistic conflict theory.
This might be a tad too large to read but if you want more information, find it here at https://www.simplypsychology.org/robbers-cave.html