Social Proof

Where all think alike, no one thinks very much – Walter Lippmann

The principle of social proof says that we look to other people to decide what constitutes correct behavior. ‘We view a behavior as more correct in a given situation to the degree that we see others performing it’.

This is the fourth post in a series on Robert B. Chialdini’s classic work on the study of persuasion, compliance and change, Influence: The Psychology of Persuasion, Revised Edition.

‘Usually, when a lot of people are doing something, it is the right thing to do. This feature of the principle of social proof is simultaneously its greatest strength and its major weakness. Like the other weapons of influence, it provides a convenient shortcut for determining how to behave but, at the same time, makes one who uses the shortcut vulnerable to the attacks of profiteers who lie in wait along its path.’


  • Bar tenders that salt their tip jars at the beginning of the evening.
  • Church ushers that salt collection baskets before passing around.
  • Charity telethon announcers that go into great detail listing viewers who have already pledged contributions.
  • Television producers who add canned laughter to mediocre sitcoms.
  • Club owners who create long waiting lines outside even when there is plenty of room inside.

Each of these examples illustrates the time-tested principle of social proof. In psychology researchers have shown how people suffering from phobias can be rid of these extreme fears by repeatedly watching a video of someone else doing what they are afraid of.

Social proof is the driver behind a fascinating phenomenon called ‘pluralistic ignorance‘, that is, ‘in an ambiguous situation, the tendency is for everyone to be looking to see what everyone else is doing’. The classic example of such bystander inaction is the case in Queens in New York City in March 1964, when Kitty Genovese was killed in a late-night attack on her home street as she returned from work. In a long, loud, tortured, public event, the attack unfolded over 35 minutes, watched by 35 of her neighbors from their apartment windows. In the aftermath officials and press tried to make sense of this seeing apathy attributing it variously to repressed aggressiveness and the effects of TV violence, the depersonalization of urban life and the alienation of the individual from the group.

But a pair of New York-based psychology professors, Bibb Latane and John Darley, offered a different explanation. They suggested that no one had helped precisely because there were so many observers. The first reason offered is ‘with several potential helpers around, the personal responsibility of each individual is reduced’. The second more intriguing reason is based on the principle of social proof where everyone is looking around to see how everyone else is reacting, and ‘in which each person decides that since nobody is concerned, nothing is wrong’. Years of subsequent research confirmed this behavior but encouragingly also affirmed ‘that once witnesses are convinced that an emergency situation exists, aid is very likely’. This is taught in psychology as the bystander effect.

The practical take-away is that if you find yourself in an emergency situation, be very explicit about your need for help. Don’t just groan, cry ‘help’. Better still, give an explicit instruction to an individual bystander like, ‘you in the blue sweater, call 911’. ‘Do not allow bystanders to come to their own conclusions because, especially in a crowd, the principle of social proof and the consequent pluralistic ignorance effect might well cause them to view your situation as a non-emergency.’

A more mind bending consequence of the principle of social proof is found in the Werther effect. Consider the statistical fact that immediately following ‘highly publicized suicide stories, the number of people who die in commercial airline crashes increase by 1,000 percent. The number of automobile fatalities shoots up as well’. What can explain this?  Research by a sociologist at the University of California at San Diego, David Phillips, concludes that ‘certain troubled people who read of another’s self-inflicted death kill themselves in imitation’. Phillips’ research concluded that ‘all the excess deaths following a front-page suicide can be explained as the same thing: copycat suicides. He showed that the tendency and therefore risk is higher for the copycat to be similar to the original suicide victim, e.g. a teenager or a white 50-something. And even more disturbingly he showed a link between highly publicized acts of aggression, e.g. a heavyweight title fight on TV, and measurable increases in the US homicide rate. All of this has sobering implications for ethics in journalism and television programming.

How to say no

Social proof operates on auto-pilot, what Daniel Kahneman refers to as system 1. The key to avoid error or exploitation is to recognize when the data are inaccurate. ‘If we can become sensitive to situations where the social-proof automatic pilot is working with inaccurate information, we can disengage the mechanism and grasp the controls when we need to’. Sometimes this is simple to do. Would be exploiters are often transparent with their attempts at fakery, think canned laughter during sitcoms or regular person testimonials during advertisements.

Sometimes it is more difficult. If two cars on the freeway change lanes at the same time, the likelihood is that drivers behind will follow suit, assuming they know something we don’t. But this is not necessarily true, ‘quite frequently the crowd is mistaken because they are not acting on the basis of any superior information but are reacting, themselves, to the principle of social proof’. The best defense is to develop the habit to question our social-proof auto-pilot . ‘In the same way, we need to look up and around periodically whenever we are locked onto the evidence of the crowd. Without this simple safeguard against misguided social proof, our prospects might well run parallel to those of the freeway lane switchers and the North American buffalo: Crash’.


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