Peter Ubel is professor of medicine and psychology at the University of Michigan, where he directs the Center for Behavioral and Decision Sciences in Medicine. He’s the author of the forthcoming book, Free Market Madness (Harvard Business, 2008), which investigates the irrational tics that lead people to overbid on eBay, eat too much ice cream and take our mortgages they can’t afford. Mind Matters editor Jonah Lehrer chats with Ubel about his research. Overall he finds that a combination of human attributes are linked to making bad choices such as a lack of understanding of mathematics, hard wired optimism, the need to follow the Jones next store, and limited will power.