Robber's Cave experiment

The Robbers Cave experiment is an experiment devised by Muzafer Sherif is part of realistic conflict theory. The experiment demonstrates how, when people are divided into groups, they will often buy into group conflict. Literally "us versus them" mentality.

Examples
Examples of this is readily apparent in every day life, such as sports, with football teams; politics with dividing sides; ethnic groups; ideals; finances, and any area of which can be divided into different groups.

Problems
Group division and segmentation can provide any number of problems, including the failure of cooperation between departments (such as different regional police departments in solving a case), to inter-group conflict (such as when sports teams fans winning/losing sides break out into fights). This is especially damaging in gender and ethnic divide cases.

Counteraction
Breaking inter-group conflict can be difficult to achieve as groups will often be caught in a perpetual cycle of accusing the other for faults or problems, rather than cooperative efforts to solve those problems.

To counteract, one must break the illusion of the divide by observing common ground, common goals and common approaches, whilst simultaneously refusing to take sides (this can be difficult as refusing to take sides might be met with accusations of 'you're either with us or you're against us' thought-terminating cliches). Identifying common problems is another way, however when the problems are solved, the grounds for group unity will also likely be removed as well.

Identifying the apparentness of the divide to more aware individuals by using box-busting approaches, as well as identifying and exposing the divide as unnecessary or non/counter-constructive should help. However, it may result in that people see it merely as a third party rather than a group effort.

Personal prevention
It's often easy to identify the divisionary problems in other people, however, as Robbers Cave experiment notes, it's natural to human beings, especially in cases of conditioning, which means that although an individual will feel confident (as a result of self-confirmation bias) they aren't part of it, the truth is they are more than likely are divisionary in some way (see ego self-defence mechanisms (psychology) for explanation as to why).

A prime example of alienation is a fear of spiders, although it isn't always taught explicitly, it's behaviour we naturally pick-up by observation from other people's reactions. This is part of generational conditioning, in that psychological conditions are passed down from one generation to the next.

If you feel that you are unfairly opposed to an individual due to their history (for example, if they're a criminal, a particar ethnicity, political supporter, sport team supporter, etc), imagine the individual as an identity-less robot (who is one of many robots in a sea of robots) and listen to their views or ideas or concepts. As this identity-less robot, do their ideas make sense? If they do and you're still prejudiced, you should ask yourself why you still feel prejudiced even if their ideas make sense?

Another way around is to associate the person and/or people you don't like, with other person(s) or people you do like, for example, from TV shows.