USA $25.95 CANADA $27.95 • Why do our headaches persist after taking a one-cent aspirin but disappear when we take a 50-cent aspirin? • Why does recalling the Ten Commandments reduce our tendency to lie, even when we couldn't possibly be caught? • Why do we splurge on a lavish meal but cut coupons to save 25 cents on a can of soup? • Why do we go back for second helpings at the unlimited buffet, even when our stomachs are already full? • And how did we ever start spending $4.15 on a cup of coffee when, just a few years ago, we used to pay less than a dollar? hen it comes to making decisions in our lives, we think we're in control. We think we're making smart, rational choices. But are we? In a series of illuminating, often surprising experi­ ments, MIT behavioral economist Dan Ariely refutes the common assumption that we behave in fundamentally rational ways. Blending everyday experience with ground­ breaking research, Ariely explains how expectations, emotions, social norms, and other invisible, seemingly illogical forces skew our reasoning abilities. Not only do we make astonishingly simple mistakes every day, but we make the same types of mistakes, Ariely discovers. We consistently overpay, underestimate, and procrastinate. We fail to understand the profound effects of our emotions on what we want, and we overvalue what we already own. Yet these misguided behaviors are neither random nor senseless. They're systematic and predict­ able—making us predictably irrational. From drinking coffee to losing weight, from buying a car to choosing a romantic partner, Ariely explains how to break through these systematic patterns of thought to make better decisions. Predictably Irrational will change the way we interact with the world—one small decision at a time. 0208 DAN ARIELY is the Alfred P. Sloan Professor of Behavioral Economics at MIT, where he holds a joint appointment between MIT's Media Laboratory and the Sloan School of Management. He is also a researcher at the Federal Reserve Bank of Boston and a visiting professor at Duke University. Ariely wrote this book while he was a fellow at the Institute for Advance Study at Princeton. His work has been featured in leading scholarly journals and a variety of popular media outlets, including the New York Times, the Wall Street Journal, the Washington Post, the Boston Globe, Scientific American, and Science. Ariely has appeared on CNN and National Public Radio. He divides his time between Durham, North Carolina, Cambridge, Massachusetts, and the rest of the world. www.predictablyirrational.com AUTHOR PHOTOGRAPH COURTESY OF THE AUTHOR JACKET DESIGN BY CHRISTINE VAN BREE Visit www.AuthorTracker.com for exclusive information on your favorite HarperCollins authors. HARPER An Imprint ofWzr^erQoWxnsPublishers www.harpercollins.com Predictably Irrational—it's not what you think. "A marvelous book that is both thought-provoking and highly entertaining, ranging from the power of placebos to the pleasures of Pepsi. Ariely unmasks the subtle but powerful tricks that our minds play on us, and shows us how we can prevent being fooled." —Jerome Groopman, Recanati Chair of Medicine, Harvard Medical School, and New York Times bestselling author of How Doctors Think "Dan Ariely is a genius at understanding human behavior: no economist does a better job of uncovering and explaining the hidden reasons for the weird ways we act, in the marketplace and out. Predictably Irrational will reshape the way you see the world, and yourself, for good." —James Surowiecki, author of The Wisdom of Crowds "Filled with clever experiments, engaging ideas, and delightful anecdotes. Dan Ariely is a wise and amusing guide to the foibles, errors, and bloopers of everyday decision making." —Daniel Gilbert, Professor of Psychology, Harvard University, and New York Times bestselling author of Stumbling on Happiness "This is going to be the most influential, talked-about book in years. It is so full of daz­ zling insights—and so engaging—that once I started reading, I couldn't put it down." —Daniel McFadden, 2000 Nobel Laureate in Economics, Morris Cox Professor of Economics, University of California at Berkeley "Predictably Irrational is wildly original. It shows why—much more often than we usu­ ally care to admit—humans make foolish, and sometimes disastrous, mistakes. Ariely not only gives us a great read; he also makes us much wiser." —George Akerlof, 2001 Nobel Laureate in Economics, Koshland Professor of Economics, University of California at Berkeley "The most difficult part of investing is managing your emotions. Dan explains why that is so challenging for all of us, and how recognizing your built-in biases can help you avoid common mistakes." —Charles Schwab, Chairman and CEO, The Charles Schwab Corporation predictably irrational predictably irrational The Hidden Forces That Shape Our Decisions Dan Ariely HARPER An Imprint ofHarperCoMinsPublishers www.harpercollins.com PREDICTABLY IRRATIONAL. Copyright © 2008 by Dan Ariely. All rights reserved. Printed in the United States of America. No part of this book may be used or reproduced in any manner whatsoever without written permission except in the case of brief quotations embodied in critical articles and reviews. For information, address HarperCollins Publishers, 10 East 53rd Street, New York, NY 10022. HarperCollins books may be purchased for educational, business, or sales promotional use. For information, please write: Special Markets Department, HarperCollins Publishers, 10 East 53rd Street, New York, NY 10022. Designed by Renato Stanisic Library of Congress Cataloging-in-Publication Data is available upon request. ISBN: 978-0-06-135323-9 08 09 10 11 12 WBC/RRD 10 9 8 7 6 To my mentors, colleagues, and students— who make research exciting