After Cass Sunstein co-wrote bestseller Nudge on behavioral economics with Richard Thaler, he went on to run the White House Office of Information and Regulatory Affairs from 2009-2012, acting as the President's top regulator.

But some of his more curious — and controversial — research is on conspiracy theories: how they work, and why they're often rational for people to believe. His new book, Conspiracy Theories and Other Dangerous Ideas , details this research. He spoke with Ezra Klein on his theory, and how it helps explain the disagreements between our current political parties.