Book excerpt: US AND THEM: Understanding your tribal mind reveals how and why we convince ourselves that we belong to differing human kinds - tribe-type categories like races, religions, classes, street gangs and high school cliques. Why do we see these divisions? Why do we care about them so much? Why do we kill and die for them? We see it every day on the news. Why have high schools in the US become killing zones? Why does strife continue in Northern Ireland? How do terrorists learn to torture and kill anyone who isn't one of them? Members Only answers these questions by looking at their common root in human nature. Politics and culture are invoked, of course, but the heart of the book is the individual mind. David Berreby describes how each person creates their own mind map, identifies others with similar mind maps and ostracises all those who are different. Based in solid scientific research, David Berreby exposes new discoveries about the mind and brain that will eventually overturn many of our familiar notions about human kinds and how we perceive them. This is a crucial subject that touches all of our lives in ways both large and small, obvious and subtle. Human kind thinking is part of human nature.