Robert Cialdini's 7 Principles of Persuasion, Explained

Principle I

1 of 7

Reciprocity

Give first. Receive more.

Reciprocity is the rule that obliges us to repay what another person has given us. It is among the most widely documented norms in human societies, and it works below the level of deliberate choice. The obligation arrives whether or not the gift was asked for, whether or not it was wanted, and whether or not we happen to like the person who gave it. Anthropologists have long treated the rule as a foundation of social life, because it lets one person give something away with reasonable confidence that it is not simply lost. In persuasion, what matters is that the debt reciprocity creates is usually larger than the thing that created it.

The study

The Coca-Cola experiment

Dennis Regan, working at Cornell, invited participants into what they believed was a study of art appreciation. Each was paired with a second participant called Joe, who was in fact working for the experimenter. Partway through, Joe left the room. In one version he came back empty-handed. In the other he came back with two bottles of Coca-Cola and handed one over unprompted, explaining that he had asked whether he could get himself a drink and had brought one along too. Later, Joe mentioned that he was selling raffle tickets and asked whether the participant wanted any. Participants who had been handed the drink bought roughly twice as many tickets as those who had not. The return was also badly lopsided in Joe's favour: the tickets he sold were worth several times the price of the bottle he gave away.

One thing to do with it

Give first, give something genuinely useful, and make it personal and unexpected. Then ask for what you actually want, rather than hoping the goodwill converts on its own.

Read the full guide to Reciprocity

Principle II

2 of 7

Scarcity

Less available. More desired.

Scarcity is the tendency to assign more value to things that are rare, dwindling or hard to obtain. What makes it distinctive among the principles is that the object itself does not change. The same item, the same offer, the same opportunity becomes more desirable purely because there is less of it to go around. Scarcity also has a directional quality that plain rarity does not: something that has recently become harder to get exerts more pull than something that was always in short supply, because a loss in progress is more motivating than a shortage that has always been the background condition.

The study

The cookie jar study

Participants were asked to rate chocolate chip cookies taken from a glass jar. The cookies were identical, and so were the jars. The only difference was how many cookies each jar held: ten in one condition, two in the other. Participants rated the cookies from the nearly empty jar as more desirable, and reported being more inclined to eat another one, than participants who took an identical cookie from the full jar. Roughly 150 people took part. Nothing about the cookies justified the difference in rating. The supply was doing the work.

One thing to do with it

State the real constraint and what is actually lost by waiting. If you have to invent the constraint, the honest conclusion is that you do not have a scarcity argument to make.

Read the full guide to Scarcity

Principle III

3 of 7

Authority

Credible experts are persuasive.

Authority is the tendency to defer to people we take to be knowledgeable or entitled to direct us. It is an efficient rule, because following someone who genuinely knows more saves us the cost of working things out ourselves. The difficulty is that we rarely verify the expertise directly. We read the signals that usually accompany it: the title, the credential, the uniform, the setting, the confident manner. Those signals can be worn by people who have the underlying competence and by people who do not, and the deference attaches to the signal either way.

The study

The uniform experiments

Leonard Bickman had a researcher stop people on the street and give them an instruction. The instruction was identical every time. Only the clothing changed: ordinary civilian dress, a milkman's outfit, or a security guard's uniform. In one of the requests, the researcher pointed at a man standing beside a parked car and told the passer-by to give him a coin for the parking meter. Dressed as a civilian, the researcher was obeyed by about a third of those he stopped. As a milkman, a little over half. In the guard's uniform, close to nine in ten complied. The uniform carried no legal power over anyone on that street, and the person giving the order was the same person throughout.

One thing to do with it

Establish credibility before you make the argument, keep the claim inside the territory your expertise actually covers, and where possible have someone else state it for you.

Read the full guide to Authority

Principle IV

4 of 7

Commitment and Consistency

Small commitments lead to bigger ones.

People want to act in ways consistent with what they have already said and done. Once a position has been taken, especially out loud, in writing or in front of others, the pressure to behave in line with it is considerable, and it comes as much from inside as from anyone else. This is why a small initial agreement so reliably makes a larger one easier to obtain. The first commitment does not simply put a foot in the door. It changes how a person understands themselves, and the later behavior follows the self-image rather than the request.

The study

The beach study

Thomas Moriarty staged a series of thefts on a crowded New York beach. A researcher would lay out a towel near a chosen sunbather, play a portable radio, then leave the towel and radio and walk off toward the water. A second researcher would then arrive, pick up the radio and walk away with it. When the first researcher had said nothing before leaving, four people in twenty did anything at all to stop the theft. In the other condition, the researcher first turned to the neighbor and asked them to keep an eye on his things. Nineteen people in twenty intervened, and many did so physically, stopping the thief and demanding the radio back. The request took a moment and changed almost nothing about the situation except that a promise now existed.

One thing to do with it

Start with something small, active and voluntary, ideally written or said aloud. Then make the larger request consistent with the position they have already taken.

Read the full guide to Commitment and Consistency

Principle V

5 of 7

Liking

People say yes to people they like.

We agree more readily with people we like, and the things that make us like someone are more mundane than most people expect. Similarity, genuine compliments, familiarity and co-operation toward a shared goal all do reliable work. Liking is the most intuitive of the principles and the most commonly misapplied, because it is usually treated as a matter of being pleasant. The research points somewhere more specific: what moves people is not general warmth but the discovery of a particular connection between two individuals, and the more distinctive that connection appears, the more it does.

The study

The coincidence experiments

Jerry Burger and colleagues ran a series of studies in which a requester arranged for participants to discover an incidental similarity between the two of them. In one version they appeared to share a birthday. In another, a first name. In a third, an unusual fingerprint type. The similarities were trivial by design: none of them said anything about shared values, interests or history, and none had any bearing on the request that followed. Across the studies, participants who believed they shared the small coincidence agreed to the request substantially more often than those who did not. Something that could not possibly matter to the merits of the decision reliably changed the decision.

One thing to do with it

Look for the specific thing you genuinely share, and say it plainly. If the only thing you have in common is something everyone has in common, it will not carry the request.

Read the full guide to Liking

Principle VI

6 of 7

Social Proof

People follow the lead of similar others.

Social proof is the tendency to decide what is correct by finding out what other people think is correct. It governs behavior most strongly under two conditions: when we are uncertain what to do, and when the people we are watching resemble us. Both conditions matter. Certainty reduces the need to look around, and dissimilarity reduces the value of what we see when we do. Social proof is not simple herd instinct. It is a reasonable inference, that the accumulated behavior of many people probably encodes information we lack, applied in situations where the inference does not hold.

The study

The street corner study

On a busy New York street, researchers had a group of confederates stop on the pavement and look up at a window on the sixth floor of a nearby building. There was nothing to see. The size of the group was varied across trials, from a single person up to fifteen, and the researchers filmed what passers-by did. More than fourteen hundred pedestrians were recorded. With one person looking up, about four percent of passers-by stopped to look as well. With fifteen, about forty percent stopped, and a much larger share glanced up without breaking stride. The only thing that changed between trials was the number of people already doing it.

One thing to do with it

Show what comparable people actually do, name who they are, and keep the numbers true. A handful of credible peers will outperform a large anonymous figure.

Read the full guide to Social Proof

Principle VII

7 of 7

Unity

Shared identity moves people.

Unity is the most recently identified of the principles, and it is not a stronger form of liking. Liking runs on what we have in common. Unity runs on who we are together: family, nationality, faith, region, profession, the team we support. The distinction matters because a shared identity is not a similarity that has been noticed. It is a category that includes both people, and inside that category the other person's interests are treated, to a degree, as an extension of one's own. That is why unity produces behavior that ordinary rapport does not, including help given at real cost and without calculation.

The study

The football shirt experiment

Mark Levine and colleagues recruited committed Manchester United supporters at a British university, asked them questions designed to bring their identity as United fans to the front of their minds, then sent them across campus to another building. On the way, a man jogging past them slipped on a grass bank, fell, grabbed his ankle and cried out. He was working for the researchers, and he wore one of three shirts: a Manchester United shirt, a Liverpool shirt, or a plain unbranded sports top. Help depended heavily on the shirt. The injured man was far more likely to be helped when he wore the participant's own team colors than when he wore a rival's shirt or no team colors at all. The injury, the setting and the man were identical in every condition.

One thing to do with it

Identify the category you genuinely share, make it salient before the request rather than during it, and draw the boundary as widely as the truth allows.

Read the full guide to Unity

Learn the seven principles of influence.

The seven principles explain how you influence people.

Each principle, one at a time.

Reciprocity

The Coca-Cola experiment

Scarcity

The cookie jar study

Authority

The uniform experiments

Commitment and Consistency

The beach study

Liking

The coincidence experiments

Unity

The football shirt experiment

Go deeper with the seven principles.

Start using the seven principles.