Rule of Three: When Three Charms but Four Alarms

Marketing managers are in the business of persuading consumers to buy their brand. To do so, they must create messages that successfully illustrate the brands’ unique benefits and compel consumers to act. When it comes to structuring and delivering such messages, we know many things. For example, we know that using credible sources and eliciting a connection with the audience increase effectiveness. We also know that message framing and sequencing matter as much as content. And we know that messages should be coherent and easy to process.

However, until now we have known very little about how much to say in a message that is designed to persuade. For instance, how many positive claims should marketers make to be optimally persuasive? On one hand, more claims should be more powerful because a message with more claims provides more information. On the other hand, part of a message’s ability to persuade depends on the consumer believing it is truthful, and too many claims might cause consumers to become skeptical of a message.

To address this issue, Professor Kurt Carlson (Georgetown) and his colleague Suzanne Shu (UCLA) developed the following research questions:

(1) Are more claims always better?

(2) If not, what is the ideal number of claims?

To answer these questions, Carlson and Shu showed consumers messages containing varying numbers of positive claims about products and people. They then asked consumers to react to the persuasiveness of the messages. What they found was shocking: Positive impressions of the product peaked at three claims. That is, more claims led to a more positive impression, but only up to three claims. As the number of claims in a message increased beyond three, consumers’ impressions of the product actually declined. Carlson and Shu found this pattern in several experiments.


In their first experiment, Carlson and Shu attributed the source of claims to either the brand promoting its product or Consumer Reports magazine. When claims were attributed to neutral sources, impressions were positively correlated with the number of claims. In contrast, when the claims were attributed to those with self-interest, impressions peaked at three claims.

In a second experiment, Carlson and Shu expanded the number of categories for which claims were made (cereal, restaurant, shampoo, ice cream store, politicians) and asked participants about their level of  skepticism toward the product (in addition to their impression of the product). Across all categories, they found that product impressions increased and skepticism remained flat as the number of claims increased from one to three. But after three claims, skepticism began rising and impressions of the product began decreasing (see Figure 1).




In a follow-up experiment, they found that while some individuals became skeptical beyond three claims (and subsequently had decreased perceptions of the product) others did not become skeptical (and their impressions continued to increase with the number of claims) (see Figure 2). They also found that as the number of positive claims about a product increased from three to four, skeptical consumers exhibited increases in counter-arguing. Interestingly, consumers who were under significant cognitive load as they encountered messages did not differ in their impression of products that were promoted by three compared to four claims. This result suggests that when consumers do not have the ‘spare’ cognitive resources to be
skeptical, increases in the number of claims may not be deleterious.

For those seeking an optimal message design, the critical question is: Where is the tipping point at which additional claims undermine the effectiveness of all the claims? Carlson and Shu’s research reveals that in settings where consumers know the source has a persuasion motive this tipping point will be the fourth claim. Accordingly, making three claims optimizes persuasion without triggering the skepticism and coping processes that undermine messages.

Kurt Carlson

Director of the Georgetown Institute for Consumer Research and Professor of Marketing, McDonough School of Business

Professor Carlson teaches courses on marketing research, consumer behavior, and marketing management. He is also the director of the Georgetown McDonough Behavioral Research Lab. He received his bachelor’s and master’s degrees from the University of Wisconsin and his Ph.D. in marketing from Cornell University. Prior to joining Georgetown, Carlson was on the faculty of the Fuqua School of Business at Duke University from 2001 to 2009.

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