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We are irresistibly drawn to FREE offers. To an extent, this makes sense: if you get something FREE, there’s no risk. So why not accept it?

But as Dan Ariely points out in his fascinating book, Predictably Irrational, our obsession with FREE goes beyond the logical. We’ll take FREE options over better, non-free options.

Dan Ariely gives many examples of the power of FREE. I’ll outline just three in this post.

FREE vs 1 cent

Dr Ariely and his collaborators* set up chocolate stands offering passersby a choice between:

  • Lindt Truffle (wonderful stuff) for 15 cents, or
  • Hershey’s Kiss (cheap, waxy crud) for 1 cent

Predictably, most people (73%) opted for the Lindt Truffle.

So they knocked one cent off the price of each, offering:

  • Lindt Truffle for 14 cents, or
  • Hershey’s Kiss for FREE

This tiny change totally reversed the outcome: 69% opted for the free Hershey’s Kiss.

My first thought was, “Oh, people probably just didn’t want to fuss the pocket change.” But Dr Ariely’s team repeated the experiment taking change out of the equation. The results were the same.

FREE exchanges

On Halloween, Dr Ariely gave trick-or-treaters 3 Hershey’s Kisses. Then, he gave them a chance to make a trade:

  • Trade 2 Hershey’s Kisses for a large (2 oz) Snickers bar, or
  • Trade 1 Hershey’s Kiss for a small (1 oz) Snickers bar

All but one subject made the logical choice: trading 2 Kisses for the large Snickers bar gives you much more chocolate overall.

Then Dr Ariely changed the offer:

  • Trade 1 Hershey’s Kiss for a large (2 oz) Snickers bar, or
  • Take a small (1 oz) Snickers bar for FREE. (No need to give up a Kiss.)

Logically, you’re much better off taking the first option: give up one Kiss and get the large Snickers. In terms of sheer tonnage, you get much more chocolate that way. But as you probably guessed, test subjects were irresistibly drawn to the FREE offer. 70% made the wrong choice.

“But they were just kids! They don’t know better!” you object? Dan Ariely repeated the experiment with MIT students. Same result.

Real-World Example: FREE SHIPPING at

Years ago, Amazon started offering FREE shipping (with a minimum order, of course). Predictably, sales took off… except in France.

The French division of Amazon, it turned out, had implemented the offer a bit differently. Rather than FREE shipping, they offered “1 Franc” shipping. One Franc was about 20 cents — pretty close to free and a real bargain. But close isn’t good enough, it seems.

When the French changed the offer to FREE, sales exploded just like everywhere else.


There are countless other examples of how people are irrationally attracted to FREE offers. So take a look at your website’s offerings, and see if there isn’t some way you can incorporate “Free” into the mix.

* Kristina Shampanier (then a PhD student at MIT) and Nina Mazar (professor at University of Toronto).

Dan Ariely is the James B Duke Professor of Psychology & Behavioral Economics at Duke University. Besides “Predictably Irrational: The Hidden Forces That Shape Our Decisions”, Dan is also the author of The Upside of Irrationality: The Unexpected Ways We Defy Logic at Work and at Home and a Burner.