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Predictably Irrational

The Hidden Forces That Shape Our Decisions

By Dan Ariely
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Predictably Irrational by Dan Ariely

Predictably Irrational (2010) explains the fundamentally irrational ways we behave every day. Why do we decide to diet and then give it up as soon as we see a tasty dessert? Why would your mother be offended if you tried to pay her for a Sunday meal she lovingly prepared? Why is pain medication more effective when the patient thinks it is more expensive? The reasons and remedies for these and other irrationalities are explored and explained with studies and anecdotes.

Key idea 1 of 10

To appraise things, we compare them to others.

Are you single? Here’s a surprising tip on how to attract potential dating partners at a club: bring along a friend who looks similar to you, only is slightly less attractive. This will greatly increase your chances of success.


Our minds are fundamentally wired to look for comparisons. What’s more, we tend to do this in the laziest way possible: by using the easiest comparisons around.

By showing up at a bar with a slightly less attractive version of yourself, you’re giving your potential dating partners an easy comparison. Instead of going to the trouble of comparing lots of different-looking people, they can clearly see that you are preferable to your friend. Since you won this easy contest and other comparisons are harder to make, you will probably be seen as the cutest person at the club. Congratulations! Just don’t tell your friend why you’ve invited them out.

The same tendency to compare applies to prices of products, and many marketers take advantage of this by introducing expensive “decoy products” that make other things seem cheaper by comparison. For example, some savvy restaurants will deliberately overprice the most expensive item on their menu, so customers will then feel the second most expensive item is relatively cheaper and wind up ordering it.

Though comparing helps us make decisions, it can also make us miserable. Constantly comparing your salary, clothes or car to others’ will leave you envious and in a state of perpetual displeasure with what you have. After selling his Porsche Boxster, James Hong, cofounder of, said:

“I don’t want to live the life of a Boxster, because when you get a Boxster you wish you had a 911, and you know what people who have 911s wish they had? They wish they had a Ferrari.”

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