Social proof describes how people think it is appropriate for them to believe, feel, or do something to the extent that other people are believing, feeling, or doing it too. Social proof provides both the validity that something is good as well as proof of possibility. It also works in reverse for example with the Bystander Effect.

The effect of social proof increases with:

  1. A higher number of people involved
  2. The degree of similarity these people have to you
  3. Your level of uncertainty about how to behave in a situation
  4. The degree of collectivism in your culture

Social proof is a concept from psychology and social science coined originally by Robert Cialdini in his book Influence. Each person has an inherent desire to conform because if he got kicked out of the tribe it would mean almost certain death a few thousand years ago. There’s also a mathematical logic to it. If many people believe something or act in a certain way, it can’t be too bad because they all survived with this behavior. Hence, it’s more likely that the behavior is advantageous than not.

However, you can use the concept to deliberately influence and persuade people. You’ll encounter it a lot in marketing and sales for instance. Understanding it will protect you from manipulation and bias (see Groupthink), while in turn, it allows you to convey your arguments more persuasively. Finally, it helps you understand a central piece of how people make decisions.


Social proof in marketing

Testimonials, reviews, and influencers are all ways to show social proof to prospective buyers. They say “look, all those people who are like you (or who you want to be like) trust us and bought this product”, so why shouldn’t you?

If it’s used ethically, meaning the testimonials, reviews, and influencers act authentically and truthfully, it can help bring your product to others where it likely brings value. However, it’s often used as an unethical tactic to convince you to buy shit you don’t need.

Adoption of innovations

There’s a classic innovation adoption lifecycle that goes from early adopters, to early majority, then late majority, to laggards. To move an innovation from left to right, Everett Rogers suggests five causal elements: the usefulness of the innovation itself, the adopters, communication channels, time, and a social system. Social proof plays a key role in this.

The innovation must be widely adopted to self-sustain. Within the rate of adoption, there is a point at which an innovation reaches critical mass. In 1989, management consultants working at the consulting firm Regis Mckenna Inc. theorized that this point lies at the boundary between the early adopters and the early majority. This tipping point between niche appeal and mass (self-sustained) adoption was originally labeled “the marketing chasm” – (Wikipedia)

Tribalism: Cult stories

Cialdini describes a North American doomsday cult in his book Influence:

The cult leader predicted a terrible flood at a specific date where only the cult followers would be rescued by a spaceship. A journalist managed to infiltrate the cult and found some interesting points:

  1. The level of commitment to the cult’s belief system was very high
  2. The members were surprisingly inactive when it came to spreading their beliefs.

This changed when the predicted date of the flood came… and passed, without any flood taking place or spaceship appearing. The members didn’t start to doubt the belief system as one might expect. They didn’t face the Cognitive Dissonance. Instead, they started to become very vocal and public in spreading their belief. Cialdini writes:

it was not their prior certainty that drove the members to propagate the faith; it was an encroaching sense of uncertainty. It was the dawning realization that if the spaceship and flood predictions were wrong, so might be the entire belief system on which they rested.

The only way to compensate for the lack of proof in the real world cult members started to establish social proof to gain validity for their erroneous beliefs. This might seem ludicrous to you, but most members have given up everything for the cult (family, friends, money), and facing reality would have been too painful.

Another famous one is the Jonestown Massacre.

The 1978 Jonestown Massacre is one of the most shocking, terrifying examples of the dark side of social proof. Under the leadership of religious fanatic Jim Jones, 918 people died in a commune in Georgetown. Although the event was technically a mass suicide, the degree of duress and force under which the deaths happened and the fact that 1 in 3 were minors mean that massacre is more accurate. Nearly a thousand members of the cult drank poison, including infants. Within a matter of minutes, all were dead. (Farnam Street)

While most analyzes of the Jonestown Massacre focus on Jim Jones’s charisma as a leader to explain the events Cialdini highlights the strategic steps Jones employed to leverage social proof to persuade his followers:

First, Jones led his followers to the African country of Guyana. This had the effect of isolating the members since only cult members had any similarities to each other.

And second, he strategically persuaded a sizable proportion of the group members and then let the social proof do the legwork for him with the rest and new members.

His real genius as a leader was his realization of the limitations of individual leadership. No leader can hope to persuade, regularly and single-handedly, all the members of the group. A forceful leader can reasonably expect, however, to persuade some sizable proportion of group members. Then the raw information that a substantial number of group members has been convinced, can by itself convince the rest. (…) the most influential leaders are those who know how to arrange group conditions to allow the principle of social proof to work maximally in their favor.

– Robert Cialdini, Influence


Protect yourself against social proof manipulation

As always, the first step is to be aware of social proof. Whenever the 4 factors stated in the introduction are present, it’s best to be careful.

The most practical way to lessen the effect of social proof is to do your own research. Don’t trust the opinion of the majority instead challenge the assumptions and do your own experiments. With this, you reduce the uncertainty that increases your reliance on the group. It takes work however and isn’t practical in every case. You have to prioritize which beliefs are beneficial to challenge and which aren’t worth the effort.

The second thing you can do is tactically uncover differences between you and the group. The less similar the people seem the less impactful the social proof. It really is just about attention. If you focus your attention on the differences instead of the commonalities it happens automatically. The trade-off is the us-against-them dynamic that is created that way.

Use social proof to persuade

Whenever you’re making an argument use others to support it. These tactics leverage the effect of social proof:

  1. Show data of lots of people acting in a certain way, for example trend reports.
  2. Use testimonials of other people. Make sure the testimonials are specific and from a high-credibility person. For example, Warren Buffett saying how awesome you are at investing.


No limitations. Social proof is deeply ingrained in us and influences us whenever there are multiple people involved.


👥👥👥 The crowd/mob. It’s the ultimate expression of social proof, bringing people to irrational and sometimes crazy behavior.


“Since 95 percent of the people are imitators and only 5 percent initiators, people are persuaded more by the actions of others than by any proof we can offer.” – Cavett Robert (taken from Influence)

“The five most dangerous words in business are: ‘Everybody else is doing it.'” — Warren Buffett

“We use social proof to decide how to dispose of an empty popcorn box in a movie theater, how fast to drive on a highway, or whether to tackle that fried chicken or corn on the cob with our hands at a dinner party. At the more consequential end of the spectrum, we rely on social proof to inform moral choices- whether to assist an inebriated football enthusiast who falls on the sidewalk or step forward as a whistleblower.” – The Power of Positive Deviance, Richard Pascale