“Our irrational behaviors are neither random nor senseless — they are systematic and predictable.”
We assume we know what is best for us, and we assume we make the right decisions for ourselves.
Unfortunately, we fall victim to our own internal processes that cannot be readily controlled; we act irrationally (as the entire book suggests). And the scary part? We do it CONSTANTLY, in the same ways, over and over again. Our monkey-brains follow patterns so reliable you could set a clock to them.
Dan Ariely is a behavioral economist at Duke, and what makes this book stand out is that Ariely actually RUNS the experiments. He’s not theorizing from an armchair — he’s testing real people and showing you the data.
I’ll briefly cover my relative interpretation from each chapter.
Chapter-by-Chapter Takeaways
1. Truth About Relativity: Everything is relative to your knowledge, experience, wants, needs, right down to the environment and moment. Being objective is difficult, no matter who you are.
2. Fallacy of Supply and Demand: If there is less of something, then the price changes, right? Well, retailers would want you to believe this when they decrease or increase the price on something. We buy more when we think there is a discount, yet in reality, we are being “guided” to buy things when the retailer wants to sell. Prices are all made up.
3. The Cost of Zero Cost: FREE! is a huge motivator, and will get us to give up quality and time. FREE is due to “loss aversion.” We feel like we are losing if we pay money, so FREE sounds better — even if that something free is garbage.
4. The Cost of Social Norms: We are happy to do things for others, but when we are paid to do them, it becomes a “market transaction.” Doing a favour for someone is more meaningful, but if they pay you, they are putting a price on your time, and this can be offensive.
5. The Power of a Free Cookie: If you give something away for free, then its value is relatively low. But what if you made people PAY for that same item instead? They end up valuing it more.
6. The Influence of Arousal: Under normal conditions, men will reject many scenarios. But when sexually aroused, men become different people, and that same scenario now makes more sense. Sexual arousal will make men do stupid things.
7. The Problem of Procrastination: Willing yourself to do something you don’t want to do is very difficult. When a task is ordered by a superior, that person completes the task on time. But chronic procrastinators will wait until the last minute AND perform worse. Motivating yourself is difficult.
8. The High Price of Ownership: We overvalue what we have. 90-day warranties will trick you into wanting to keep an item. Having a feeling of ownership will get you emotionally attached to the item, event, or whatever. Hoarding can result.
9. Keeping Doors Open: We habitually have a hard time closing doors (opportunities, whether good or bad). This is an “aversion to loss” again — even when this is not economical, based on time, money, or energy. Close doors that no longer benefit you.
10. The Effect of Expectations: Stereotyping, and “self-fulfilling prophecy.” Have a professional violinist play in a subway, and he is ignored. Take an average violinist and put him in a concert hall, and his music sounds better, and you appreciate it more. We bias ourselves into loving or hating something.
11. The Power of Price: A 1-cent aspirin vs. a 50-cent aspirin. Both are chemically the same, yet the 50-cent one “feels” like it works better. Higher prices give us a placebo effect of working better, or being better overall. We value higher prices more, even if they are the same (brand names).
12. The Cycle of Distrust: Give away free money, and people instinctively believe there are conditions. This is because marketers and salespeople are prone to lying and scamming (cable companies, banks, and whoever else).
13. The Context of Our Character, Part 1: Humans are a dishonest bunch. When given the opportunity and safety to cheat, they will. Cheating is rampant in professional firms, governments, and agencies. Cheating can be circumvented by signing a “declaration of honesty,” or even recalling religious scriptures and laws (i.e., the 10 commandments) before engaging in an activity.
14. The Context of Our Character, Part 2: Why dealing with cash makes us more honest. When we directly think about cash, most people will not steal. But office employees in the US commit about $600 billion in crime every year. This includes theft, under-the-table deals, and other white-collar crimes, filing false claims, and so on.
15. Beer and Free Lunches: This last one is about social conditioning. Let 4 people publicly choose free beer, and they will choose different brands each. But let them choose privately, and they will choose their actual choice. Social conditioning in the US makes us individualistic. But in Hong Kong, people wish to conform. Cultural differences in conformity.
Why This Book Matters for Real Life
Here’s where it gets personal. After reading this book, I started catching myself in the act. Every time I saw the word FREE on a website, I noticed the pull. Every time I compared prices, I realized I was evaluating it RELATIVE to whatever anchor the seller placed in front of me — not on its own merits.
If you work in marketing — which I do — this is essential reading. Ariely gives you a map of how humans actually make decisions, and once you see it, you can’t unsee it.
The chapter on social norms vs. market norms stuck with me the most. You do someone a favor, the relationship is warm. The moment you attach a dollar amount to that same favor, it becomes transactional. Once you cross that line, it’s almost impossible to go back.
How It Connects to Other Books
If you’ve read Influence by Cialdini — which I also reviewed — you’ll find overlap. Cialdini covers persuasion principles; Ariely covers the mechanics of bad decision-making. Together, they explain why people can so easily nudge us in directions we didn’t intend to go.
I’d also pair this with The Art of Thinking Clearly by Rolf Dobelli. Ariely goes deeper on fewer topics, but the experimental approach makes his arguments harder to dismiss.
Final Thoughts
These are just a few of the ways we are irrational. Go figure. Think before you act.
Ariely’s writing is accessible and entertaining, backed by real research — not anecdotes. Each chapter reads like a standalone essay, easy to pick up and put down.
If you’re interested in psychology, behavioral economics, or simply understanding why you keep making the same questionable decisions, this is a foundational read.
One of the best behavioural economics, sociological, and psychology books of all time. A+++
Thanks for reading.
— Leonidas
