Persuasive Power of Uncertainty – Review Of

Harvard Business Review (HBR) interviewed Zak Tormala of Stanford about their current research.
232 The Persuasive Power of Uncertainty (Podcast)

Part of their study involved a fictitious restaurant where researchers tried to study the power of uncertainty by experts and non-experts using restaurant reviews. The restaurant review was done in the most favorable light and their intent was to be as compelling as possible.

HBR Image from

There were two restaurant review experts, one expressed certainly about the review (we’ll call Expert A) and the other reviewer expressed somewhat less certainty (Expert B). The manipulated variable in their restaurant review was the level of certainly. When Expert A was definitive in their review, the response to that review wasn’t as compelling.

In other words, according to the researchers, when dealing with the experts, the definitive review was being less persuasive. If Expert B reviewed the restaurant with a certain amount of uncertainty, readers were somewhat surprised to hear this and became more interested. When customers’ curiosity was piqued, they were more likely to pay attention and possibly more open to persuasion. 

If the variable being manipulated was the level of expertise, the opposite occurred. If the non-expert was more certain with their review, they were more persuasive. If non-expert was less certain, they were generally not very persuasive. According to this study, with non-experts, the level of persuasiveness depends on how much certainty you project. Because they are non-experts, the key for believability had to be how certain they were.

So experts who have a lot of credibility have some leeway to express doubt and still be persuasive. Obviously, the opposite occurs for those who aren’t experts. If you want to be persuasive and are not an expert, the level of persuasiveness will make all the difference.

If you are a CEO who’s an expert about your company, you can sometimes help your audience focus on your message by expressing a little doubt or certainty. It might help to get people to perk up and pay more attention than usual.

You may express a little uncertainty at the opening to your speech to set the tone to help get your message across. Of course, for this to be successful, your message has to be relevant to your listening audience.

The podcast does not recommend using this approach all the time. It depends on your intent. If your intent is to convey a message your audience is interested to hear, and you want your audience to be comfortable and relaxed, it is better for the CEO to be comfortable and relaxed. If what you’re telling is compelling and you need more focus, this approach of an expert expressing some uncertainly might be a useful tool.

Kevin Schwarm

I have over 25 years of professional experience in business, information technology (IT), and customer service. Industry experience in retail, medical insurance, higher education, non-profit, financial services, and property and casualty insurance. Customer focused professional interested in providing value (save time, money and aggravation) by evaluating and analyzing information, services and products with a unique perspective.

17 Responses

  1. Bill says:

    I’ll have to look it up, but I think this idea is also found in “Made to Stick” by Chip and Dan Heath. I think they framed in more in “mystery”. But, as you’ve noted, it can’t be used all the time. The news today of the demise of Osama bin Laden is full of skepticism since all there is currently to go on is the good word of the people in power. Proof through proper verification processes would eliminate doubt.