Make three claims when trying to persuade

Suzanne B. Shu and Kurt A. Carlson have a paper (pdf) on this claim:

How many positive claims should be used to produce the most positive impression of a product or service? This article posits that in settings where consumers know that the message source has a persuasion motive, the optimal number of positive claims is three. More claims are better until the fourth claim, at which time consumers’ persuasion knowledge causes them to see all the claims with skepticism. The studies in this paper establish and explore this pattern, which is referred to as the charm of three. An initial experiment finds that impressions peak at three claims for sources with persuasion motives but not for sources without a persuasion motive. Experiment 2 finds that this occurs for attitudes and impressions, and that increases in skepticism after three claims explain the effect. Two final experiments examine the process by investigating how cognitive load and sequential claims impact the effect.

Here is a NYT summary of those results.


The description says they ran 4 experiments. But for some reason, their summary bundles the results into 3 findings...

Cicero would be pleased to learn that his triplicate had something going for it.

Hippodamus too.

And every debate coach and speech coach I ever had.

Along with those English teachers pounding the 5 paragraph essay into me (opening, 3 arguments, closing)

"The professors acknowledge their study’s limits. For one thing, their paper uses four experiments to make their case, not three."

That's why I'm skeptical.

I've always wondered why the business world is all about 3's. Three reasons why you want to work here, three things you would change about your job, three bullet points summarizing your ideas, etc...

"30 Rock" had a running joke that 3 examples were funnier than 2 or 4.

Was this an inside behind-the-camera joke or did they talk about it on the show? I'd love to find a video clip with an example of this. Happen to remember any particular scenes?

If they continued on, they may have found new optima at the 40th, 50th or 60th claim.

But then the interlocutor may have left by claim number 10, convinced enough of the argument, but no longer interested in the conversation :)

A professor in undergrad once remarked that people seem to have a hard time keeping track of lists longer than three. So if you have 10 pieces of information,always try to organize into three categories, then you can remember. She recommended never exceeding lists of five, because almost no one can keep track of five or more reasonably complex ideas or pieces of information at the same time.

The climax of Dashiell Hammett's "The Maltese Falcon" comes with Sam Spade's speech explaining to the femme fatale why he's decided to do what he's going to do with her and lists 11 or 12 reasons, then Spade says: They may not be be good reasons, but look how many of them there are.

John Huston's screenplay cuts that down to 7 reasons and keeps the summary line.

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