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Cialdini’s ‘power of influence’ proven yet again

01 Jun, 2020 Persuasion, influence, motivation

This article was originally published in 2015 and has been completely updated in 2020.

When I saw some research findings mentioned in a recent email newsletter from the Harvard Business Review, I was instantly reminded of Robert Cialdini’s principle of social proof. Messaging based on the principle of social proof is powerful – it gets results every time. You can harness it too.

What is the principle of social proof? We determine what is correct by finding out what other people think is correct. The most common application is the way we decide what comprises correct behavior. We view a behavior as correct in a given situation to the extent to which we see others performing it.

Professor Robert Cialdini, photo opposite.

It’s simple. In a sense, it’s pop psychology, but this principle is one of the world’s best motivators. I’m a huge fan. What’s more, it is scientifically based on research in social psychology. Robert Cialdini is former professor of Psychology at Arizona University. His book Influence, has sold over 2 million copies. There is a popular version and a textbook version called Influence: science and practice, which I have had on my bookshelf for a while.

How do we see the principle of social proof in action? We see it all the time in marketing and advertising. Basically we are saying “Do what other people are doing.”

Do what other people are doing

You can recognize it in messages that talk about a product being the ‘fastest growing’ or ‘largest selling’. Have you heard “This is our most popular product”? In this way, you don’t need to say how good your product is; you can just say that many others think so, which implies the same thing.

You see the principle of social proof in action in all sorts of ways. If you watch a charity telethon in action you will see on-screen the endless list of people’s names who have already donated. It implies: “Look at all the people who realize this is a good thing to do. You can join them in doing the right thing if you donate as well”.

And look at the cult-like status of Apple products. This is the power of social proof in full swing. People are known to buy Apple products on the sole basis that it is trendy to do so.

This principle applies to testimonials and celebrity endorsements. If you admire and respect the person who is endorsing a product or service, you are likely to be persuaded to think favorably towards it as well. (However, that person needs to be relevant and genuine in their support. Otherwise, their support looks fake.)

There are endless examples of this principle in action. Advertisements proclaim “x million people can’t be wrong…” [if they have bought a popular product]. And they say things like “Research shows that 8 out of 10 purchasers are repeat buyers”.

Stay ethical

Is this type of messaging manipulative or unethical? It is like all communication – it depends on the intent. How do you ensure it is ethical? Tell the truth! If it is your most popular product, then you are totally justified in stating it is your most popular product. If you are quoting satisfied customers, make their quotes genuine and facts about them truthful.

The principle of social proof applies most powerfully when we are observing the behavior of people just like us. We can relate to them and are more inclined to follow their lead. That explains why these days there are more testimonials on television showing the average person-on-the-street or in-the-home – showing what other ordinary people like and use.

A Harvard Business Review “Daily Stat” e-newsletter mentioned an example of this. When homeowners were told how their electricity use compared with their neighbors’ use, they cut their electricity consumption by 2% on average, which is the same amount of cut when electricity rates go up by 11-20%. This research conducted by the Massachusetts Institute of Technology showed that interventions not based on electricity prices can substantially and cheaply change consumer behavior.

If you are seeking to persuade, using the principle of social proof in your communication will achieve great results.

Top photo by Nathan Dumlao on Unsplash.

About Kim Harrison – author, editor and content curator

Kim Harrison, Founder and Principal of Cutting Edge PR, loves sharing actionable ideas and information about professional communication and business management. He has wide experience as a corporate affairs manager, consultant, author, lecturer, and CEO of a non-profit organization. Kim is a Fellow and former national board member of the Public Relations Institute of Australia, and he ran his State’s professional development program for 7 years, helping many practitioners to strengthen their communication skills. People from 115 countries benefit from the practical knowledge shared in his monthly newsletter and in his books available from

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