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Persuasive Web Design, Part 21: Using Contrast (and Decoys) to Influence Decisions

We don't like to evaluate products in a vacuum. We prefer — even need — to contrast and compare products to other, similar products.

This principle applies to all product attributes: taste, smell, attractiveness, etc. Just to keep it simple, let's stick to an easily quantified attribute: price.

Logical Online Persuasion

Say you're looking for an outboard motor. You find a 20 HP Motor for $1,900. Is this a good price?

It's hard to tell, isn't it? Your first response is, "What do other makes and models sell for?"

Now assume you're shown a list of prices:

  • 10 HP Motor, $1,600
  • 20 HP Motor, $1,900
  • 25 HP Motor, $2,700

Does the 20HP Motor for $1,900 seem like a good deal now?

You bet it does: It's only slightly pricier than 10 HP motor, but has twice the power. And the 25 HP engine, which is only slightly more powerful, costs almost 50% more. Easy decision, isn't it?

The above seems simple enough. And logical. But let's take it a bit further... and see how logic breaks down.

Crazily Irrational Persuasion

If you were flirting with the idea of subscribing to The Economist, which offer would you prefer:

  • Web Only $59
  • Print and Web $125

Dan Ariely conducted just such an experiment.* Given the above choice, only a minority — 32% — opted for Print and Web (which is what The Economist really wants to sell).

Then Dr Ariely put in a decoy. (To be precise, he put it back in. The clever folks at The Economist had actually used this technique in a web advertisement.)

  • Web Only $59
  • Print Only $125
  • Print and Web $125

The decoy (Print Only for $125) looks so bad, you might think it was a mistake. Why would anyone choose Print Only when they can get Print and Web for the same price?

They wouldn't. But it's no mistake. It's there for the sole purpose of making Print and Web look like a bargain.

And it works. With the decoy in place, 84% opted for Print and Web.

Think about it. The percentage who chose Print and Web rose from 32% to 84%... yet nothing had changed! The offerings and prices were exactly the same. The only difference was the decoy, which of course nobody took.

It's not rational, but it works. Products look much better when placed next to similar but less desirable products. Better not only in comparison to the less desirable product, but better overall. It's a kind of "halo effect".

Using These Principles to Make Your Website More Persuasive

On your website, you control the comparisons. For best effect:

  • Don't price items in a vacuum. Let customers compare prices and features to other, similar items.
  • If you only sell one product (or one product in a given category), add one or more additional products — even if only as decoys. Customers need comparisons.
  • If there's an item you really want to sell, place it next to a similar but less desirable option.

Finally, remember the "halo effect". By adding an intentionally bad option as a decoy, you can make a product appear not only better than the decoy, but better overall. Used properly, this is one of the most diabolically effective online persuasion techniques available.

* See Chapter 1 of Predictably Irrational.

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Comments (Comment Moderation is enabled. Your comment will not appear until approved.)
This is a good example of what is known as the "context choice".
The best paper on this in this book by Tversky,


Depending on the margins, you can also make the lowest price option more selected.

Generally, you need two apparently incompatible dimensions of value, and you force the choice you want or the dimension you want by introducing a third option which is clearly on one of the relevant dimensions.

A difficult choice problem is made easy.
# Posted By Michael Webster | 7/22/10 9:59 AM

Excellent article. Thanks for sharing.

(Incidentally, there's a missing word in your post. You clearly meant, "you force the choice you want or the dimension you want by introducing a third option which is clearly INFERIOR on one of the relevant dimensions.")

One example from the article...

Given a choice between:

* $6 in cash, or
* An elegant Cross pen

Only 36% chose the Cross pen. But when an inferior choice (what I'd call a decoy) was added:

* $6 in cash
* A cheap pen, or
* An elegant Cross pen

The percentage who chose the Cross pen rose to 46%.

It's wonderfully irrational!
# Posted By Michael Straker | 7/22/10 11:47 AM
Yes, you are right about the missing word. Thanks for reading the post in a charitable fashion!

I have had discussions with Dan about his "irrational" vision - because to the extent that something is predictable, then there is some sort of maximization going on. He appears to agree with that claim.

My own sense is that if someone is coming to your website with the intent to buy, and is confused by having to make hard trade-offs, then inserting a decoy not only works but is appreciated by the buyer.

Otherwise, I am less sure that inserting the third alternative is a good strategy.
# Posted By Michael Webster | 7/22/10 6:23 PM

(We really need a non-Michael in this discussion. I'm getting confused.)

I'm not sure that any strategy is universally applicable. That's what makes this field so challenging... and fun.

Adding more choices can certainly be counterproductive. See Part 5:


Of course, it's pretty easy to reconcile the two principles: adding additional GOOD options may lead to decision paralysis; adding a BAD option (or decoy) makes the decision easier.

As always, the rule is: "Test it and find out."

# Posted By Michael Straker | 7/22/10 8:11 PM