The Diderot effect

Also called Cross-selling

Offer the thing that completes what they just bought, while it still feels new.

Bring them back
Price and package

The idea

A new purchase can make everything around it look out of place, which nudges people toward the matching next thing. In marketing, it's why a well-chosen follow-on offer feels helpful instead of pushy.

Why it works

It is named after the French writer Denis Diderot, whose 1769 essay described how a beautiful new dressing gown made the rest of his study look shabby, until he had replaced almost everything in it. Anthropologist Grant McCracken named the effect in 1988.

Research: Diderot 1769, McCracken 1988

Where to use it

Checkout pages

Suggest one add-on that makes the main purchase work better, with its price shown and an easy way to skip it. A wall of extras feels like a sales tactic.

This model needs a wall mount. Add the one made for it?

Follow-up emails

Send the next offer once the first result has arrived and the customer is pleased with it. Frame it as finishing the job, not starting a new one.

Your new logo looks great. Want your business cards and email signature to match?

Sales calls

When a customer is happy with the first result, ask what now looks out of place next to it. Let them name the next thing before you suggest it.

Now the website looks like this, how does your Facebook page compare?

Retargeting ads

Show recent buyers the matching next step, not the thing they already bought. Exclude them from ads for the original product.

Just finished your new deck? Here's outdoor lighting made to match it.

Bundles

Bundle the things that belong together so the set is complete from day one, and price the bundle honestly against buying the parts separately.

The full set: shopfront sign, matching van decals and business cards.

Steal these

Fill in the brackets and use them in your next post, ad or email.

Your new [purchase] is [ready]. Want your [related thing] to match?
Now that [first result] is done, does your [related thing] still fit?
Made for your [purchase]: [add-on], $[price]. Skip it if you don't need it.
Finish the set: [item one], [item two] and [item three], together for $[price].
Just finished [first job]? Here's how to [protect or match] it.

Before and after

Before

You might also like these other products

After

Your new boots need a waterproofing spray to stay that way. Here's the one made for leather.

The first is a generic list that could follow any purchase. The second offers the one thing that completes this purchase, so it feels like looking after what they bought, not being sold more.

Where it backfires

Pushing unrelated extras, or stacking add-ons at checkout. If it doesn't genuinely complete the first purchase, it reads as upselling for its own sake, and pre-ticked add-ons feel like a trick.

Pairs well with

The peak-end ruleOffer the next step at the high point, right as the customer is admiring the first result.

Common questions

Is the Diderot effect just upselling?

It's the reason good cross-sells work. The next offer should complete what they already bought, not just add to the bill. If you wouldn't recommend it to a friend in the same spot, don't offer it.

When is the right time to offer the next thing?

Right after they see the result of the first purchase and are pleased with it. Too early, before the first thing arrives, and it feels like pressure. Too late, and the new-purchase feeling has faded.

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