Is there a golden formula for designing the most persuasive message?

Persuasive communication can be very important - as recently demonstrated by the need to convince people to wash their hands often, to keep your distance and to stay at home in case of symptoms. Scientists have been wondering whether there is a golden formula for achieving the most convincing message for over 2,000 years. Researchers from Northwestern University (Prof Daniel O'Keefe) and Utrecht University (Prof Hans Hoeken) wanted to know the answer to this question. Based on their analysis of 1,149 studies with 280,591 subjects, they found that it makes little difference which choices are made in the message, and that the effect is often unpredictable. The article was published in 'Frontiers of Psychology'.

Choices in delivering the message

There is enough research on thirty choices for the content of a message that it is possible to calculate an average effect on the power of persuasion and to see how stable these effects are.

"When you want to convince people, the content of the message is often more or less fixed, but many choices remain: should you draw the conclusion explicitly or leave it implicit, should you name the advantages of doing it or the disadvantages of not doing it? Do you use pictures or no pictures, do you use humour or not? Is it wise to use metaphors, as Minister of Health, Welfare and Sport Hugo de Jonge often does, or rather not?" explains Hoeken. "There is enough research on thirty of these choices that it is possible to calculate an average effect on the power of persuasion and to see how stable these effects are."

1,149 studies

"On the basis of 1,149 studies, we calculated the average effect and prediction intervals. Prediction intervals indicate the limits within which you can expect an effect if you were to apply a certain message characteristic to a new message. Our analysis shows that, on average, one of the choice alternatives usually leads to a more convincing message, but that the effect is rather small and also very variable. An example is that the use of the story form is on average a little more convincing than a non-story form, but there are circumstances in which the story form is considerably less convincing."

Communication advice

The researchers emphasise that communication always remains important, even if we cannot say with certainty whether a message achieves the right effect. Hoeken: "Communication can have great effects, as we can see in times of corona, but it is not so predictable. It's not a question of turning a few knobs to get the best result." Experts who advise on message design should be aware that the empirical basis is shaky and the effect cannot always be predicted. "When you look at corona communication everyone thinks it is very important, but at the same time you have to be suspicious of anyone who shouts 'I know how it is done'" states Hoeken.

When you look at corona communication everyone thinks it is very important, but at the same time you have to be suspicious of anyone who shouts 'I know how it is done'

Realistic expectations

The analysis, published in the journal 'Frontiers of Psychology', has all kinds of consequences: For persuaders (who must have realistic expectations about the consequences of their choices), for those who advise on message design (who must be cautious and modest), and for researchers (who must design future studies so that they are able to find those small effects and possibly identify circumstances under which those variations have a larger or more consistent effect).