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The cover of Predictably Irrational

Predictably Irrational

Dan Ariely, 2008

Our mistakes are not random; they repeat in predictable ways. Experiments on decoys, free offers, price and honesty reveal the hidden forces steering everyday choices.

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16 parts, about 28 minutes to read.

Why read it

  • Shows through experiments how a useless decoy option and an arbitrary first price steer what we choose and pay
  • Explains why a free offer can pull us off a better deal and why money turns favors into market exchanges
  • Tests how arousal, procrastination and ownership distort judgment, and how a moral reminder before temptation reduces cheating

Who it is for

  • Shoppers who want to spot pricing tricks
  • Managers and marketers who design offers and incentives
  • Readers curious why smart people repeat the same mistakes

What the summary covers

  1. Introduction: How an Injury Led Me to Irrationality2 min
  2. The Truth about Relativity2 min
  3. The Fallacy of Supply and Demand2 min
  4. The Cost of Zero Cost2 min
  5. The Cost of Social Norms2 min
  6. The Power of a Free Cookie1 min
  7. The Influence of Arousal2 min
  8. The Problem of Procrastination and Self Control2 min
  9. The High Price of Ownership2 min
  10. Keeping Doors Open1 min
  11. The Effect of Expectations2 min
  12. The Power of Price2 min
  13. The Cycle of Distrust1 min
  14. The Context of Our Character, Part I2 min
  15. The Context of Our Character, Part II1 min
  16. Beer and Free Lunches2 min

Recommended by

  • Jerome GroopmanPhysician and staff writer at The New Yorker
    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.
  • James SurowieckiAuthor of The Wisdom of Crowds, former New Yorker business columnist
    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.
  • George AkerlofNobel laureate in economics
    Ariely not only gives us a great read; he also makes us much wiser.

About the author

  • Dan ArielyProfessor of business administration at Duke University, behavioral economics author
    • He was injured in an explosion, and his long hospital treatment became his introduction to the study of irrationality.
    • He began by researching how to deliver painful but unavoidable medical treatments to patients better.
    • Earned a PhD from the University of North Carolina at Chapel Hill in 1996.
    • Completed a second PhD, in business administration at Duke University, in 1998.
    • Taught at MIT from 1998 to 2008 as the Alfred P. Sloan professor of behavioral economics.
    • At Duke University he is James B. Duke Professor of Psychology and Behavioral Economics and a founding member of the Center for Advanced Hindsight.
    • A 2012 paper he coauthored was found in 2021 to rest on falsified data and was retracted.
    • His 2002 paper with Klaus Wertenbroch on procrastination and deadlines was retracted in September 2026.

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