Social proof – how you and your customers make decisions

Recently, C&A Brazil did an interesting and innovative Mother’s Day campaign: They linked the coat hangers in store with Facebook so that each hanger showed the number of Facebook ‘Likes’ each piece of clothing received. The campaign was a huge success with part of the collection being sold out on the first day.

One reason for this outstanding result lies on the use of social proof, a powerful persuasion technique.

Figure 1 – C&A São Paulo created a section in their shops with clothes that had the greatest number of Facebook

What is social proof?

We all believe ourselves to be independent thinkers and that we make our decisions following well thought out decisions based on rational reasoning.

Well, this is not entirely true as our decisions are highly influenced by what other people do and what we believe to be the accepted social behaviour in a particular situation. This mostly occurs subconsciously, indeed it has been estimated that around 95% of the decisions we make (including purchases) are made without conscious, rational deliberation[1].

All this has been investigated scientifically for decades and we now have a good understanding of how this ‘social proof’ effect (and other persuasion effects – see later posts) works. With this knowledge comes the ability to use this phenomenon to create positive actions by customers.

Power of the crowds

Back in 1951, an experiment to test the power of group consensus asked people in a group setting to do an easy task that was  very difficult to get wrong. The twist was that only 1 person in the group was actually being tested while the rest were actors who together deliberately gave wrong answers. When faced with this group behaviour people often followed the group choice, even when the consensus was blatantly wrong[2].

Figure 2 – One of the groups in the 1951 experiment. The person being tested is the one with the white shirt on the right.

Figure 3 – On the right we can see an example of the line matching exercise. The correct answer is clearly C, despite the obviously straightforward answer, most of the people that were tested went along with the group decisions despite how wrong they looked!

Another ground-breaking study[3] looked at the number of people it takes doing something to influence others to do the same. In this case it was found that, on a busy street in New York as the number of actors looking up increased, more passersby also looked up creating a positive feedback loop of traffic jamming proportions!

These experiments, and others since, show:

  • it is part of human nature to conform to group behaviour, and
  • the larger the group the more irresistible becomes the urge to conform

Applying social proof to persuade customers

When a decision process is complex and people are uncertain about what to do  they tend to look at what others are doing or what they did for cues. This works as a shortcut that can make decisions easier. – when a view or behaviour is popular people tend to see it as the correct option.

Retail has been quick to capitalise on this behaviour and examples of it being used are abundant.

Figure 4 – McDonalds has for quite a long time advertised in front of their stores how many burgers they had served to date. Over 99 billion burgers served have a strong persuasive power as it suggests that McDonald’s burgers are appreciated by a lot of people.

Figure 5 – Best Sellers shelves on bookstore are a perfect example of the use of social proof to persuade customers. Best selling books are nothing more than consensual choices mande by a large number of people. Knowing that a book is a best seller is a strong motivator to make people want to read it.

Figure 6 – Even ‘The King’ used social proof in his favour. If a person who never heard Elvis’ songs (if such one exists) saw this record they would likely be tempted to listen to it.

With the social web, e-commerce has an excellent platform for taking advantage of this human trait to persuade customers. In my next post I will discuss some techniques to take advantage of the persuasive power of social proof to drive online sales.

Figure 7 – Twitter’s ‘trending topics’ show what’s most popular with its users in their particular region. The average person would be curious to know what everyone locally is talking about, and this provides a perfect environment for social persuasion; cue targeted advertising and other ways to monetise its services.


[1] G. Zaltman, How Customers Think: Essential Insights Into the Mind of the Market. Harvard Business Press, 2003.

[2] S. E. Asch, “Effects of group pressure upon the modification and distortion of judgments,” Organizational influence processes, pp. 295–303, 2003.

[3] S. Milgram, L. Bickman, and L. Berkowitz, “Note on the drawing power of crowds of different size.,” Journal of Personality and Social Psychology; Journal of Personality and Social Psychology, vol. 13, no. 2, p. 79, 1969.

Learn more about persuasion

Sign up to our ‘Designing for persuasion’ course and find out how to make sure your design and copy creates action and avoids procrastination.

Leave a comment

Your email address will not be published.

Read enough? Get in touch...

Contact Caroline Bentley to discuss your needs:
0207 608 1670

Or come visit us, we have offices in Oxford, Sheffield and London.