Why do our headaches persist after we take a one-cent aspirin but disappear when we take a fifty-cent aspirin?

Why do we splurge on a lavish meal but cut coupons to save twenty-five cents on a can of soup?

When it comes to making decisions in our lives, we think we're making smart, rational choices. But are we?

In this newly revised and expanded edition of the groundbreaking New York Times bestseller, Dan Ariely refutes the common assumption that we behave in fundamentally rational ways. From drinking coffee to losing weight, from buying a car to choosing a romantic partner, we consistently overpay, underestimate, and procrastinate. Yet these misguided behaviors are neither random nor senseless. They're systematic and predictable?making us predictably irrational.

Dan Ariely is the bestselling author of Predictably Irrational, The Upside of Irrationality, and The (Honest) Truth About Dishonesty. He is the James B. Duke Professor of Psychology and Behavioral Economics at Duke University and is the founder of the Center for Advanced Hindsight. His work has been featured in the New York Times, the Wall Street Journal, the Washington Post, the Boston Globe, and elsewhere. He lives in North Carolina with his family.