Influence: The Psychology of Persuasion

Robert Cialdini

Compliance professionals like advertisers, con artists and salespeople take advantage of preprogrammed human reactions to elicit the response that’s in their best interests, not ours. Specifically, they leverage the principles of reciprocation, scarcity, consistency, social proof, liking and authority.

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Our brain loves shortcuts, and they can be used to manipulate us.

The world is a complex place where it’s impossible for us to reflect upon the details of every decision we make.

One example of such a shortcut is that we’re much more willing to do people a favor if they provide us with a reason – any reason. In an experiment to study this phenomenon, a researcher asked people queueing up to use a copy machine whether she could skip the line. She found that if she gave a reason – “May I skip the line because I’m in a rush?” – 94 percent of people complied with her request.

People usually assume expensive items are of higher quality than cheap ones.

Six basic psychological principles that we use as shortcuts, and which can be exploited for persuasion:

  1. Reciprocation
  2. Scarcity
  3. Consistency
  4. Social proof
  5. Liking
  6. Authority


Humans have an overpowering need to return favors.

People are so keen to rid themselves of the burden of reciprocity that they will often perform much larger favors in return for small ones.

The first psychological principle of persuasion is the rule of reciprocation: we feel obliged to return favors.

Getting into the habit of asking yourself if the favors you receive are really genuine, or if they could be attempts to manipulate you.

In negotiations, starting with an outrageous request and retreating from there can win concessions.

Just as we desire to pay back favors, when we’re negotiating with someone and they make a concession, we’ll feel obliged to reciprocate it. This is known as the rejection-then-retreat strategy.

The contrast principle: when two items are presented to us one after the other, the difference of the second to the first is magnified.


When opportunities become scarce, we desire them more.

A 1982 study by one of Cialdini’s students showed that when shoppers were told of a limited-time sale on meat, they bought three times more than if there was no time limit. Interestingly, this effect was compounded when people were told that only a select few knew about the sale. The scarcity of both the offer and the information itself made shoppers buy six times more meat than customers unaware of either limit!

We tend to want something more if its availability has decreased recently than if it has remained steady over time. This is why revolutions tend to happen when living conditions deteriorate sharply rather than when they are consistently low; the sudden drop increases people’s desire for something better, so they take to the streets.

Competition always sets our hearts racing. Whether in auctions, romances or real-estate deals, the thought of losing something to a rival often turns us from reluctant to overzealous. This is why, for example, real estate agents often mention to buyers that several other bidders are also interested in a given house, whether true or not.

To counter the eagerness that arises from scarcity, we should always consider whether we want the item in question because of its use to us (for example, its taste or function), or merely because of an irrational wish to possess it.

Banning something makes it very desirable.

When juries know that an insurance company will pay the bill, they tend to award larger damages to plaintiffs. Interestingly though, they award even higher damages if they are expressly told by the judge to ignore the fact that the defendant has insurance. The “forbidden” information seems more relevant to them and makes them overreact, just like a forbidden toy seems immensely desirable to any child.

One study of Colorado couples found that when the parents tried to interfere with their relationship, feelings of love and desire for marriage only intensified! And when the interference was lessened, romantic feelings tended to cool off too.


We want to stay true to our word.

When people on a beach witnessed a staged theft of a radio from a neighboring towel, only 20 percent reacted. But if the owner of the towel had first asked people to “please watch my things,” 95 percent of their neighbors became near-vigilantes, even chasing down the thief and forcefully grabbing back the radio. Why? Quite simply, we humans have a strong desire for consistency: we wish our actions to be consistent with what we’ve said. As the study showed, this drive is so strong that it even seems to trump concerns for our own personal safety.

The widely known foot-in-the-door sales technique takes advantage of how even small commitments affect our self-image. The first goal of salespeople is to get prospects to make a small purchase that is not even intended to make a profit. Rather, it constitutes a small commitment that changes the prospect’s own perception into one of a customer, making them much more amenable to the larger deal down the line.

When uncertain, we look for social proof. We often decide what the correct course of action is by looking to others’ behavior. Social proof becomes a particularly powerful influence when we face uncertainty.

Bystander inaction - people are less likely to help a victim in an emergency if other people are present. How can you get help effectively? The safest bet is to single out an individual from the group and direct a clear help request at them: “You, in the green shirt, call an ambulance.” This way, the person can’t shy away from the responsibility and won’t need to look for guidance from the others. As a result, they will almost certainly help.

People who are similar to us can greatly influence our choices. People tend to look to others for guidance as to how to behave. And this tendency is strongest when the person observed is similar to ourselves.


We comply with people we like, and it is easy for some people to make us like them.

Have you ever been to a Tupperware party? If you go, be sure to appreciate the skill with which the business model leverages the power of compliance tricks. From reciprocity, where every attendant gets some kind of gift before the buying begins, to social proof, where each purchase made strengthens the view that similar people are also buying the product, the concept is masterfully crafted. But perhaps the greatest trick is that the invitation for the party has not come from the Tupperware presenter, but rather someone whom every invitee likes: a friend. Why is this such a powerful trick? Well, as a rule, we’re more compliant toward people we like.

Attractiveness produces a so-called halo effect, meaning that we tend to see attractive people as smart, kind and honest.

To protect ourselves against likability manipulation, a good step is to ask ourselves whether we have come to like someone or something unusually strongly in a short time.


We obey authorities without question, and mere symbols of authority can already win our compliance.

Clothes and props are also powerful authority symbols. In Milgram’s experiment, it was the authority figure’s white lab coat and clipboard that convinced participants they should obey them and “torture” their fellow test subjects. And con artists exploit the power of these symbols to their full extent by donning uniforms, suits and even priest’s robes if need be.

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