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How Many Types of Social Proof Are There?

December 1, 2020 | Social Proof on Websites
  • There Are Only Two Types of Social Proof
  • Who Coined the Term ‘Social Proof’?
  • Social Science Experiments Describing Social Proof
  • What is Modern Social Proof
  • Types of Social Proof According to Conversion Rate Optimization (CRO) professionals
  • What is a ‘Category’ of Social Proof?
  • There are only 2 Types of Social Proof – According to Social Scientists
  • What You Need to Know About Modern Social Proof
  • Free Offer and Privacy Policy

There Are Only 2 Types of Social Proof

Much ink and many pixels have been spilled attempting to describe social proof.

Here are 8 of the top Conversion Rate Optimization (CRO) blogs in the world right now.  If anybody is knowledgeable about social proof on websites it is these experts:

  1. CXL blog writer Shanelle Mullin describes 6 types of social proof (but, really, gives us 9)
  2. Buffer blogger Alfred Lua describes 6 MORE types of social proof
  3. The CrazyEgg.com blog says 8 types of social proof is the correct number of types.
  4. Jarrod Morris of Evidence.io stops at 3 types of social proof:  expert, celebrity and user.
  5. BigCommerce.com blogger Megan DeGruttola says there are 11 types of social proof.
  6. Hubspot blogger Sophia Bernazzani cites 20 examples but declares that there are only 5 types of social proof.
  7. Sumo.com blogger Sarah Peterson says definitively there are 12 types of social proof.
  8. SproutSocial blogger Dominique Jackson describes 7 tactics to achieve social proof but qualifies this by saying they all use just one strategy that“…revolves around showing that other people like what you are offering.”

I’ll stop here – it seems like the more people we ask, the more answers we get. 

Here is an example of how we gathered data from the 8 bloggers listed above.  This is simply a list of the the categories of social proof each blogger described in their blog.  The example image shown is SproutSocial:

Gathering data from the SproutSocial blog on their Categories of Social Proof
Gathering data from the SproutSocial blog on their Categories of Social Proof

We’ll explain the color-coding in just a moment.

So, who is right?  Perhaps they are all partially right but it appears that there are only 2 distinct categories of social proof – we’ll get to those in just a moment.

But, to fully answer the question “How many different categories of social proof actually exist?” we first need to understand where this increasingly prevalent term ‘social proof’ came from.


Who Coined the Term ‘Social Proof’?

Dr. Daniel Cialdini coined the term ‘social proof’ in his 1984 book Influence: The Psychology of Persuasion.  He lists social proof as one of the ‘weapons of influence’ that trigger automatic, subconscious behaviors in all people.  

Perhaps Dr. Cialdini’s greatest contribution was that he made accessible to the general public the academic studies on social proof.  Cialdini made ‘social proof’ part of the public consciousness in general and a part of marketers’ toolkits, in particular.

However, Dr. Cialdini’s method of studying these ‘weapons of influence’ was not in university laboratories – he went straight to the wielders of the weapons – people he called ‘compliance professionals’ – salesmen, fund-raisers, recruiters, advertisers and others.

After years of covertly infiltrating sales meeting and training courses put on by multi-level marketers, Dr. Cialdini codified his observations in his book into the following 6 principles of persuasion:

  1. Consistency/commitment – once we make a choice among competing alternatives, we need to affirm to ourselves that we made the initial, correct choice.  We affirm our initial choice by choosing that same alternative again and again and again…
  2. Reciprocation – The Reciprocity Rule states that we repay, in kind and measure, what another person has given us.  All human societies have unwritten rules that mandate repayment of social debts – ‘favors’.  All societies also punish ‘free riders’ and selfish people.
  3. Social Proof – usually, when a lot of people are doing the same thing, it is the right thing to do.  There are only two types of social proof (described below): Normative Social Proof and Informational Social Proof.
  4. Liking – most of us, given the chance, would prefer to do business with our friends.  Several of the bloggers listed above cite ‘The Wisdom of Your Friends’ as a type of social proof.
  5. Authority – according to Cialdini, “…we are trained from birth that obedience to proper authority is right and disobedience is wrong”. (Influence, p.216)  We will discuss the Milgram experiment that shows the horrible lengths people will go to when blindly following authority.  Interestingly, 6 of 8 of the CRO bloggers above cite Expert Testimonials, based on Authority, as a type of social proof.
  6. Scarcity – opportunities seem more valuable to us when the availability is limited.  ‘Squeeze pages’ and ‘sales funnels’ are famous across the internet for using scarcity to motivate people to click that button.  ‘Fear of Missing Out’ or FOMO is a new category of social proof that several CRO experts cite that has become MORE relevant in the internet age due to the ‘always-on’ nature of our mobile devices.

Read an in-depth analysis of Influence in our blogpost on The 6 Forces of Persuasion of Dr. Robert Cialdini.


Social Science Experiments Describing Social Proof

Dr. Solomon Asch first distinguished informational social proof from normative social proof in 1951 by asking groups of university students to judge the lengths of 3 bright lines projected on a wall.  All of the group members were actors, except one – the study subject.  All of the actors were instructed to give the wrong answer as to which line was equal to a ‘target line’.  The study subject, who answered last and had heard all of the wrong answers, ALSO gave the wrong answer about 75% of the time.  The study subject’s explanation, when asked, why they agreed with the wrong answer was that they did not want to go against the group and appear to be disagreeable or weird.  

SproutSocial.com blogger Dominique Jackson has a nice visual you can use to understand what Dr. Asch’s ‘bright lines’ looked like yourself.

Dr. Stanley Milgram, in one of the most infamous experiments in the social sciences, in 1961 asked volunteer ‘Teachers’ to administer electric shocks to Learners (paid actors) to ‘understand how punishment affects learning’.  

The Teacher asks questions from a list while the Learner answers the questions.  Wrong answers are given an electric shock by the Teacher. This was a ruse.  There were no electric shocks.  However, the volunteer Teachers did not know that.  Instead, the Teachers are given access to a phony control board with dials marked in volts.  The dial begins at 15 volts but, ominously, goes all the way to 450 volts.  As the Teacher begins to ask questions, the Learner is given ‘electric shocks’ in response to wrong answers.  

Through an intercom system, the Teacher can hear the Learner begin to yell uncomfortably once the dial reaches 120 volts.  At 150 volts, the Learner begs for the experiment to stop.  One hundred percent of the Teachers in Milgram’s experiment continued to deliver shocks.  At 165 volts, the Learner began to shriek and kick the wall.  At 300 volts, the Teachers heard the Learner “shout in desperation” yet most (65%) of the Teachers continued to deliver electric shocks.  Why? 

In Dr. Stanley Milgram’s own words:  “It is the extreme willingness of adults to go to almost any lengths on the command of an authority that constitutes the chief finding of the study”.

Dr. Albert Bandera famously demonstrated negative social proof with the Bobo Doll experiment in 1963 when first grade children observed an adult behaving aggressively; hitting, punching and kicking an inflatable plastic mannequin named Bobo.  The children were then left alone in a room full of toys, including Bobo.  Dr. Bandura then observed new behavior in the kids, you guessed it – hitting, kicking and punching Bobo.  Dr. Bandura’s experiment showed that children observe and model the behavior of other people, specifically adults they perceive to be most like them.  

Dr. Bandura developed Social Learning Theory that shows how children and people internalize and model another persons’ behavior.  According to Social Learning Theory, most children model behavior of people they believe are similar to them; thus, boys often model their fathers while girls may model their mothers.  

The modeled behavior can be reinforced.  Positive, internal reinforcement might occur from a good feeling we experience after using a behavior for the first time.  A successful purchase from a website could create positive, internal reinforcement.  

Vicarious reinforcement also occurs – this is when we see someone else receive positive, internal reinforcement from a behavior they perform.  Vicarious reinforcement is the basis for customer testimonials.  When we see someone else buy through a website and then hear or see their customer testimonial, we are motivated to model and imitate their behavior.


Modern Social Proof

It is one thing to study college students and 1st graders but quite another to study social proof on websites that sell things such as the bloggers listed above.

CRO professionals study social proof where the rubber meets the road – where customers click-to-call or give their credit card number to a person they’ve never met.  Customers who buy something they’ve never held, felt or seen through a website need to trust that website.  

So, what types of social proof on websites do these professionals observe?  What forms of modern social proof works and what does not work?  Let’s ask the CRO pros on the CXL.com blog for this quote by Angie Schottmuller:

Angie Schottmuller, CRO Expert
Angie Schottmuller, CRO Expert

“The social proof psychology principle says that when people are uncertain, they’ll most likely look to others for behavioral guidance. 

In order to harness this concept for persuasion, marketers must first identify the uncertainties of their customers and then buffer accordingly with appropriate social proof.

Customer words, numbers, and visuals can boost credibility, convey relevance, answer questions, and counter objections. 

The conversion impact of inspiring confidence is roughly proportionate to the social proof quality and the percent of ‘uncertainty’ friction preventing call-to-action (CTA) completion.

In other words, if there’s little uncertainty, social proof will have negligible impact. 

If there’s notable uncertainty and weak social proof, negative conversion impact is possible. 

If quality social proof buffers notable uncertainty, get ready for some remarkable conversion impact – in some cases up to 400% improvement.”


Types of Social Proof According to Conversion Rate Optimization (CRO) professionals

We looked at the 8 blogs listed above and listed each of the categories they had created.  There were a total of 64 categories created, an average of 8 categories per blog with a range from 3 to 12 social proof categories.  Several of the categories were duplicated. 

For example, ‘Celebrity endorsements’ were cited by 7 of the 8 bloggers as a unique category.  ‘Expert social proof’ was cited by 6 of the 8 bloggers as its own category.  ‘User/customer testimonial’ or ‘Customer review’ was cited by 8 of 8 of the bloggers as a unique category. (data set below)

Some categories had different names but the same general description:  ‘The Wisdom of Crowds’, ‘Subscriber counts’, ‘Number of users’ and ‘Data/numbers’ all had about the same descriptions as each other.

To simplify the categories created by the CRO experts, we grouped them into the following 4 groups:

  • The influence of testimonials from ONE person:  this includes expert, influencer, celebrity or user testimonials.  We also grouped Case Studies into this group since most case studies describe 1 case.  This was the largest group with 34 of the 64 categories.
  •  The influence of a large number of people: this includes rating & review sites such as Google Reviews and Yelp. The ‘Wisdom of Crowds’ was a frequently cited category and was included in this group. This group contained 17 of the 64 categories.
  •  The influence of brands, trust icons & badges.  This group had 5 of the 64 categories. 
  •  The influence of credentials including licenses, certifications & terminal academic degrees.  This group had 3 of the 63 categories.
Categories of Social Proof on Websites
Categories of Social Proof on Websites

Overall, 59 of the 64 categories were able to be grouped.  Five categories were ungrouped.  

The 5 ungrouped categories include: 

  • Gazing – an image on a webpage with clear indicators (arrows) showing the direction of gaze – usually to a call-to-action.
  • Storytelling – another person telling a memorable narrative that will stick.
  • Rankings– getting ranked by a 3rd party website, like Yelp.

Several of the categories were very creative:  User Generated Content (UGC), described by BigCommerce.com blogger Megan DeGruttola was a unique category that seemed to exclusively define a new form of social proof for the internet age: 

“While product rating and reviews fall into this (UGC) category, the most popular form of UGC today is visual content — aka the billions of photos, videos, Boomerangs, etc. that people post on social networks everyday. 

Visual UGC has proven to be the most authentic, trusted and influential content to consumers.”

Hubspot blogger Sophia Bernazzani describes backlinks to your website in much the same vein when she described a category called ‘Earned Media’:  

“If the press has published any positive reporting about your brand, this earned media is a great way to build brand awareness, backlinks to your website, and social proof that your business is worth paying attention to.” 

We questioned a few of the categories that were created:  ‘Facebook sponsored stories’ as its own category?   To be clear, CrazyEgg.com blogger Demian Farnworth calls them ‘examples’ and not categories. 

What is a ‘Category’ of Social Proof?

To qualify as a ‘category’ of social proof, we suggest the category fulfill these 3 core principles of social proof:

  • Uncertainty – the examples within the category should satisfy some knowledge gap identified by the consumer. 
  • Similarity – the examples within the category should be similar to the consumer in terms of age, gender and values.
  • Expertise – consumers assume that other people within the category are acting on superior knowledge.

Ideally, the categories would be exclusive and exhaustive.  

That is, all examples of social proof in any one category are NOT FOUND in any other category.  And, ALL the categories describe ALL examples of legitimate social proof that can be described.  There should be NO examples of social proof that do not belong to one of the categories described.

Clearly, more work is needed to further define both the categories identified by the CRO experts and by our grouping of those categories.

Here is an image of the data we used.

Data for Social Proof of Websites from the 8 CRO experts listed above
Data for Social Proof of Websites from the 8 CRO experts listed above

There are only 2 Types of Social Proof According to Social Scientists

The first type of Social Proof is called Normative Social Proof and is described by this Wikipedia post:   

“Normative social influence, aka ‘Social Validation’ is a type of social influence that leads to conformity. It is defined in social psychology as “…the influence of other people that leads us to conform in order to be liked and accepted by them.”  

The power of normative social influence stems from the human identity as a social being; with a need for companionship and association.  

Normative social influence involves a change in behavior that is deemed necessary in order to fit in a particular group.  The need for a positive relationship with the people around leads us to conformity.  This fact often leads to people exhibiting public compliance—but not necessarily private acceptance—of the group’s social norms in order to be accepted by the group.”

Normative social proof probably does not apply to website conversion optimization (CRO) since my click decisions are largely invisible to other people in my peer group and social network.  

Examples of normative social influence relevant to social media include clothing choices, womens’ hairstyles and mens’ facial hair.

The second type of social proof is called Informational Social Proof and is described in this Wikipedia post:

“Informational social influence describes a psychological and social phenomenon wherein people copy the actions of others in an attempt to undertake behavior in a given situation.  Informational social influence is considered prominent in ambiguous social situations where people are unable to determine the appropriate mode of behavior, and is driven by the assumption that the surrounding people possess more knowledge about the current situation

When ‘we conform because we believe that others’ interpretation of an ambiguous situation is more accurate than ours and will help us choose an appropriate course of action’, it is informational social influence. This is contrasted with normative social influence wherein a person conforms to be liked or accepted by others.  

Social proof often leads not only to public compliance (conforming to the behavior of others publicly without necessarily believing it is correct) but also private acceptance (conforming out of a genuine belief that others are correct).  

Social proof is more powerful when being accurate is more important and when others are perceived as especially knowledgeable.” 

In other words, normative social proof is probably what most of us think of when we remember the ‘peer pressure’ from high school. 

Informational social proof is the type of social proof Conversion Rate Optimization (CRO) specialists are most concerned with when trying to improve click-through rates on their calls-to-action on their websites.


What You Need to Know About Modern Social Proof

Informational social influence is what most people are thinking of when we use the term ‘Social Proof’.  

Small business owners interested in Conversion Rate Optimization (CRO) to gain new customers should adopt practices and techniques using informational social proof on their website.


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