DON'TBEPREDICTABLE. Dan Ariely, PhD, the Alfred P. Sloan professor of behavioral economics at MIT, spends plenty of time studying what makes people tick. If you really want to know why you can't save money or stick to that diet, or why you bought the wrong car (or married the wrong person), check out his new book Predictably Irrational: The Hidden Forces That Shape Our Decisions (HarperCollins, $26). -- Chris Tucker
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What's the most important difference between traditional economics and behavioral economics? Conventional economics assumes that we are all rational. It assumes that every time we face a choice, we consider all the available options, perform a cost-benefit analysis, and follow the best possible path of action. Behavioral economics says that we act irrationally again and again because that's how our brains are wired. So, we make mistakes and work against our own interests.

That seems a bit depressing. Yes, but only by truly understanding our irrationality can we think about how to fix it. That's the great hope of behavioral economics.