It is impossible to understand human behavior without understanding the critical role that groups play in people lives. Most of us belong to a range of formal and informal groups, including families, work teams, and friendship cliques. These groups absorb a great deal of our time and energy and are instrumental in satisfying our most fundamental needs. In addition, they connect us to larger social aggregates (e.Br>g., political parties, business organizations, religious denominations) that influence our lives in important ways.