How compelling is this ad?
Our new scheduling app does it all! It’s easy, reliable, and effective. It allows you to connect with your team and also get more done on your own. It saves you time and money. And that’s not all—it also features a smooth, functional interface.
All those things sound good, but you may have thought that something’s fishy. Can it really do all those things? Were they really trying to honestly convey the product’s qualities or were they just trying to come up with a bunch of features to manipulate me into downloading the app?
According to some research in consumer psychology, this ad made too many claims. But how many should it have made?
The Power of Three
Marketing researchers Suzanne Shu and Kurt Carlson proposed a simple number: It’s optimal to make three claims.
In one of their studies, they gave people brief messages about all sorts of things, including a new cereal, a type of shampoo, a politician, and an ice cream store. Sometimes the message made just one claim about the topic at hand. For example, “this shampoo makes hair cleaner.” Sometimes the message made six claims: “this shampoo makes hair cleaner, stronger, healthier, softer, shinier and fuller!”
When they asked people to rate the person or product the message was about, they liked it better when they saw two claims, compared to when they saw just one. But they liked it even more when they saw three claims.
But after three claims, more was not necessarily better: The shampoo that did four things seemed worse than the shampoo that only did three. And the one that did five things was worse still. This wasn’t just true for shampoo; the trend extended across all the topics they studied.
What’s Wrong with Four Claims?
I thought more was always better. So why does persuasion top out at three claims? It does seem strange that it would be bad to say your product has lots of good qualities. But that’s not quite right. We do like things that have lots of positive qualities…but only when we believe they do have all those qualities.
Shu and Carlson found that the “more is worse” effect only occurred when people realized that the communicator wanted to persuade them. If the shampoo brand itself is trying to sell us on their new product, we get skeptical when they make too many claims. It seems too good to be true.
But if the information comes from an objective third party, then yes, more good stuff is better. If we can believe that the communicator is being honest, then a shampoo with lots of good qualities is obviously better than a shampoo with only one useful feature.
When the researchers were able to turn off skepticism by distracting a bunch of participants, then there was no special advantage to making three versus four claims. If people aren’t on the lookout for persuasion tactics, then an advertisement that makes many claims no longer raises an alarm.
Are Three Claims Always Optimal?
Speaking of skepticism, I have to say I have trouble believing that “three” is the final and forever solution to persuasive communication. It’s such a specific number. The researchers argue that it fits with other studies showing diminishing returns of more than three pieces of information in general.
But I’m waiting for some more research before I apply the idea too rigidly. The specificity of this evidence is compelling, but it seems premature to suggest that one should always avoid making four or more claims.
One important point is that their studies consider fairly simple messages that just list a set of qualities without justifying them. Perhaps if you make a solid case for the claims, people’s simple skepticisms may go away. In fact, some classic research that I’ve written about before shows that even when people are paying close attention and ready to tear a message apart, making nine compelling arguments is a bit more persuasive than making just three.
More recently, cognitive psychologists studying how to debunk misinformation found no evidence that offering many critical arguments backfires. To the contrary, giving multiple reasons why a claim is false can be more persuasive than giving just a few.
In the end, the evidence suggests that when people are aware of your intent to persuade, making too many claims without evidence can invite people’s skepticism. But that doesn’t definitively mean that providing multiple arguments undermines persuasion. As is so often the case, it’s a delicate balance that an advertiser must walk.
Shu, S. B., & Carlson, K. A. (2014). When three charms but four alarms: Identifying the optimal number of claims in persuasion settings. Journal of Marketing, 78(1), 127-139.
Petty, R. E., & Cacioppo, J. T. (1984). The effects of involvement on responses to argument quantity and quality: Central and peripheral routes to persuasion. Journal of Personality and Social Psychology, 46(1), 69–81.
Ecker, U. K. H., Lewandosky, S., Jayawardana, K., & Mladenovic, A. (2019). Refutations of equivocal claims: No evidence for an ironic effect of counterargument number. Journal of Applied Research in Memory and Cognition, 8(1), 98-107.