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 amazing page-turner, 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.