I’ve just read a fascinating article by Steve Martin of Influence at Work – the ‘science behind business success’ people. It summarises a research exercise addressing the matter of, when trying to persuade people of the merits of a product or argument, how many reasons you should give.

It’s no surprise the study found you can give too few reasons and make your argument sound weak.

But what’s intriguing is that it also shows you can all too easily give too many reasons.

The research was conducted by the Andersen School of Business and Georgetown University. The participants were divided into six groups and given descriptions of a breakfast cereal, a restaurant, a shampoo, an ice cream shop and a politician.

Depending on their group, they were given either one, two, three, four, five or six positive claims about each object.

The full six claims about the shampoo, for example, were that it makes your hair “cleaner, stronger, healthier, softer, shinier and fuller”. The full six attributes given for the politician were that he had “honesty, integrity, experience, intelligence, interpersonal skills and a desire to serve.”

The researchers then assessed how positive the participants felt about each of the objects and how sceptical they were about the claims.

The striking finding was that those who’d been exposed to three positive claims were far more favourable to the objects – not only than those who’d seen one or two claims, but also than those who’d seen four, five or six.

It seems that those who’d been given more than three reasons had become sceptical: they felt people were ‘trying too hard’ to persuade them.

I also suspect that when many reasons are given, they dilute each other: people lose focus, are less able to take in the information and potentially forget all of them as a result of trying to remember too many.

So, in general, the optimal number of reasons to give to persuade anyone of a case appears to be three.

This simple finding has obvious implications for any marketing, communications or sales campaign aimed at generating favourability or sales or persuading people to take other action.

It’s human nature to throw out as many arguments as possible to try to win people over, but this study suggests this will hurt your cause.

Pick your best three. Then stop.

In the art of persuasion, less appears to be more.


What do you think is the best number of reasons to give to win people over? Does this study’s findings fit with your experience?  You can read the original Influence at Work article here.

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