Previous research has repeatedly established the “power of three” in several contexts. People like the number 3. For example, a 1979 study found that a message is most persuasive when repeated 3 times, rather than 1 or 5 times.

This study finds that 3 is the ideal number of positive claims to include in a message to maximize how persuasive it is (e.g. the phone has an amazing camera, is waterproof, and has a long-lasting battery).

The effect follows a ∩ pattern, with 1 or 2, as well as 4 or 5 (and beyond), being less persuasive than 3.

When 4 or more positive claims are used to persuade, people become skeptical and like the product less.

The effect disappears:
- If the source of a message is neutral (e.g. not a marketer trying to promote their product). In this case, more positive claims beyond 3 continue to increase how positive the message is
- If the recipient is mentally busy because they don’t have the mental capacity to become skeptical

For example, in experiments:
- When people read claims about an improved cereal on the product’s packaging, 3 claims were 10.4% more persuasive than 4 (and the most persuasive). ( see image below )
- However, if they read the claims of the cereal on a neutral consumer report, 4 claims were more effective than 3.

🧠 Why it works

When given up to three positive claims about a product, even by marketers trying to persuade us, we still perceive them as informative.

But once they become four or more, we become skeptical that someone is trying too hard to persuade us and we ‘switch off’.

Why three? Three is the smallest number at which we start to identify patterns. Once we feel we’ve identified a pattern, we think we’re ready to make a decision, for example:
- When buying something we consider having three options to choose from as the right time to choose from one
- In several U.S. states, three criminal convictions are used as an indicator that a person is a “career criminal” and should face life in prison (three-strikes laws)
- The concept was already captured in a Latin proverb used in Medieval times: omne trinum est perfectum (“every set of three is complete”)

The rule of three in persuasion