Where does the "Us" or "Them" mentality originate? Naturally there's an evolutionary predisposition to put the needs, ideas and rules or your group first so that you band together, feed and protect each other.
But where does this protection mechanism take us over and become prejudice? Could any of us discriminate against anyone different in any way given the right (or wrong) circumstances? How about based on eye color or whether or not you can curl your tongue!
The us or them mentality is large part of criminal behavior. Criminals "Other" people in order to make it easier to hurt or kill them without remorse. Scary to think we can fall on either side depending on social factors like group mentality and expectations. Also important to understand how to guard against this peer pressure buy learning to spot yourself and others conforming to group attitudes without question.
Here's an amazing video on a groundbreaking study of third graders done not by a psychologist but a now famous teacher named Jane Elliott.
She began with an experiment with a third grade class that might be frowned on today but was very revealing in that it showed just how easily people and kids form prejudices and adopt an us vs them attitude. It also shows how groups make individuals feel less responsible and therefore more willing to give up their own ideas of right and wrong.
Shockingly this experiment has been repeated multiple times and in spite of being told ahead of time that it is an experiment, the outcome is always similar. Disturbing how easily we are influenced by group expectation.
Around the 10 minute mark Elliot shows how expectations influence us. How we perceive ourselves also has a lot to do with how we do in life and the kinds of people we are. And the way others perceive us plays a large role whether we like it or not.
If you look Jane Elliott up on YouTube you will find many other fascinating videos, notably one in which the same kids look back more than 20 years later and one study with adults based on whether or not they can curl their tongues!