Here are 10 insightful studies that give a flavour of what has been discovered about the dynamics of group psychology.
1. Groups can arise from almost nothing The desire to form and join social groups is extremely powerful and built into our nature. Amongst other things groups give us a most valuable gift, our social identity, which contribute to our sense of who we are.
2. Initiation rites improve group evaluations Existing groups don't let others join for free: the cost is sometimes monetary, sometimes intellectual, sometimes physical—but usually there is an initiation rite, even if it's well disguised.
3. Groups breed conformity After joining a group and being initiated, we have to get a feel for the group norms, the rules of behaviour in that group. Group norms can be extremely powerful, bending our behaviours in ways we would never expect.
For the remaining 7 traits (including a statistic on how accurate the "Grapevine" is...) Go here for the full article:
http://www.spring.org.uk/2009/07/10-rules-that-govern-groups.php