Social Proof Effect

By Ben Ambridge


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Many of you watching this will have heard of Robert Cialdini – a Psychologist from Arizona State University – who decided to investigate what different persuasion strategies are used by professional salespeople. And what he found was that one of the most successful techniques was something called “social proof”.

Social proof is looking to others when deciding what to do or how to behave. Over the years lots of different experiments have found evidence for the importance of social proof, but my favourite was a real-world experiment done in hotels.

You would have seen the signs in hotel rooms saying something like, “Please help us conserve the planet’s resources. If you are happy to reuse your towel, please leave it on the hanger. If you would like a new towel, please leave it on the floor”.

One particular hotel called in the psychologists because customers were almost always leaving the towels on the floor. The psychologists decided to use social proof. They added at the bottom a line that said “85% of guests reuse their towel at least once” (which wasn’t actually true at the time, at least for that particular hotel).

But it quickly became true as social proof started to work. People started to think “well, if reusing the towels is what people do, then I’d better re-use the towels”. This is social proof – it’s also sometimes called the bandwagon effect. Once a couple of people start doing something, everybody else jumps on the bandwagon.

There are lots of different ways that social proof can be used on websites. The simplest way is to just say how many of a particular product have been sold. Or – as many airline and hotel sites do – you could say how many people are looking at this package right now, which also adds potential scarcity value (Cialdini found that scarcity is another top tactic used by salespeople).

But on its own, this isn’t actually that great, as people don’t really have any way of knowing whether this is a high or a low number. Also, social proof works best when you’re comparing yourself not just to people in general, but to people like you. What works better is to make it more specific. So, you will see sites like Amazon have “After viewing this page, people typically bought….”. This is more specific – customers think – well I’m viewing this page, other people who viewed this page are obviously interested in the same sort of purchases as me, and they ended up going for this one, so maybe I should too.

Another way to make it more specific is to narrow it down to things like the customer’s location. This is actually perhaps more common offline than online – you’ll see posters advertising the lottery telling you how many millionaires there have been in your postcode area – but potentially could be used online as well; particularly if you’ve been able to gather a little bit more data about who your customers actually are.

Another way of course is customer feedback. If you’re as old as me, you’ll remember when eBay launched in the UK. At the time there were loads of newspaper articles with the reporters trying this new way of shopping, and saying how uneasy it made them feel to send money off to an anonymous person with the hope that a guitar pedal or whatever would find its way back to them.

But what quelled all that unease was seller feedback. Once a few people had shopped with a particular seller, social proof kicked in, and people were confident enough to buy from them. In fact, a book that came out earlier this year, and that was also a Radio 4 series– Tim Harford talks about seller feedback as one of 50 Things That Made the Modern Economy.

Nowadays, of course, this has spread from auction sites to things like AirBnB and Uber – all rely on social proof that the seller is decent.

So, whether it’s via customer ratings, or simpler techniques such as showing the number of products sold, a great way to increase your conversions is to make use of one of the oldest and most reliable weapons in the salesperson’s arsenal – social proof.

Ben Ambridge
Hi, I’m Ben. I’m a Reader in Psychology at the University of Liverpool and I lead consumer psychology at Endless Gain. I’m interested in how research findings from academic psychology can be applied in our everyday lives as consumers. And, importantly how psychology plays an influential role in ecommerce. I write a weekly psychology column for The Observer, and my book Psy-Q: You Know Your IQ - Now Test Your Psychological Intelligence has been translated into 15 languages. Check out my TED talk, "Ten Myths about Psychology, Debunked".

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