Predictably Irrational, by Dan Ariely

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Why does sex sell? Do nice napkins make coffee taste better? And why do we love freebies? Predictably Irrational explains the mysteries of human behaviour.

One chapter of Predictably Irrational sees Ariely round-up 25 college guys to take an intimate survey on sexual preferences and limits. They do this twice, both in non-aroused and aroused states.

Being aroused, it turns out, changes the way people answer even familiar questions. It can cause them to take more risks, or even to ignore personal morals or the law.

If this sounds fairly invasive, there’s a reason. Ariely’s research is all about the subtle ways our peer groups, advertisers and even environment affects our choices – all the things which make people ‘predictably irrational’.

Why do we overvalue the things we sell, but undervalue how much we’re prepared to pay someone else? Does decor make food seem tastier and, therefore, worth paying more more for? Why are ‘free’ offers so potent?

This is a book for marketers, clearly, but also statisticians, students, and anyone even vaguely interested in the forces of influence. It’s also a reasonable primer in learning to read statistics and think beyond news headlines critically.

While not quite as immersive as Freakonomics (and arguably a bit drier), it is more applicable to everyday consumers – and that means most of us.

“But there’s also another kind of herding, one that we call self-herding. This happens when we believe something is good (or bad) on the basis of our own previous behaviour. Essentially, once we become the first person in line at the restaurant, we begin to line up behind ourself in subsequent experiences. Does that make sense? Let me explain.”


Dan Ariely, Predictably Irrational: The Hidden Forces That Shape Our Decisions. Thorsons, 2009

Other books like Predictably Irrational
  • Freakonomics, by Stephen D. Levitt and Stephen J. Dubner (statistics, everyday economics, consumerism)
  • Factfulness (critical thinking, understanding influences)

Picture credit: Patrick Fore