Us Vs. Them In 'Moral Tribes'

Joshua Greene spends his days studying how humans make moral decisions. With a deep knowledge of philosophy and brain scan science, the Harvard psychologist probes some big questions, such as, why is it we're often willing to put the welfare of our communities above our own personal welfare? And why do communities of people — sports fans, religious believers, political groups — have so much trouble getting along?

The question is hugely important in this modern world when conflicts among political parties, religious faiths and nations have dramatic consequences. This is at the core of Greene's new book, Moral Tribes:Emotion, Reason, and the Gap Between Us and Them.

Joshua Greene, professor of social sciences and director of the Moral Cognition Lab at Harvard University.