Influence: The Psychology of Persuasion by Robert Cialdini
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Influence: The Psychology of Persuasion by Robert Cialdini

Book notes on the reference for understanding human behavioural patterns.
Influence: The Psychology of Persuasion by Robert Cialdini

Robert Cialdini's Influence brings together the key elements of persuasion in a concise way, teaching us how they work, why they work and how to use them.


Most of us know very little about automatic behavior patterns. They make us terribly vulnerable to anyone who does know how they work. There is a group of people who know very well where the weapons of automatic influence lie.

There is a principle in human perception, the contrast principle, that affects the way we see the difference between two things that are presented one after another.

So if we lift a light object first and then lift a heavy object, we will estimate the second object to be heavier than if we had lifted it without first trying the light one.

A nice demonstration of perceptual contrast is sometimes employed in psychophysics laboratories to introduce students to the principle firsthand:

Each student takes a turn sitting in front of three pails of water—one cold, one at room temperature, and one hot. After placing one hand in the cold water and one in the hot water, the student is told to place both in the lukewarm water simultaneously. The look of amused bewilderment that immediately registers tells the story: Even though both hands are in the same bucket, the hand that has been in the cold water feels as if it is now in hot water, while the one that was in the hot water feels as if it is now in cold water. The point is that the same thing—in this instance, room-temperature water—can be made to seem very different, depending on the nature of the event that precedes it.

A man might balk at the idea of spending $95 for a sweater, but if he has just bought a $495 suit, a $95 sweater does not seem excessive.


A well-known principle of human behavior says that when we ask someone to do us a favor we will be more successful if we provide a reason.

Example: "Excuse me, I have five pages. May I use the Xerox machine because I’m in a rush? "

The effectiveness of this request-plus-reason was nearly total: Ninety-four percent of those asked let her skip ahead of them in line. Compare this success rate to the results when she made the request only: "Excuse me, I have five pages. May I use the Xerox machine?". Under those circumstances, only 60 percent of those asked complied.

It seems that it was not the whole series of words, but the first one, “because,” that made the difference.

"Excuse me, I have five pages. May I use the Xerox machine because I have to make some copies?". The result was that once again nearly all (93 percent) agreed.

The rule says that we should try to repay, in kind, what another person has provided us.

The rule possesses awesome strength, often producing a “yes” response to a request that, except for an existing feeling of indebtedness, would have surely been refused.

As a marketing technique, the free sample has a long and effective history. For instance, the Disabled American Veterans organization reports that its simple mail appeal for donations produces a response rate of about 18 percent. But when the mailing also includes an unsolicited gift (gummed, individualized address labels), the success rate nearly doubles to 35 percent.

Marcel Mauss, in describing the social pressures surrounding the gift-giving process in human culture, can state, “There is an obligation to give, an obligation to receive, and an obligation to repay.”

Most of us find it highly disagreeable to be in a state of obligation. It weighs heavily on us and demands to be removed.

Example: Suppose you want me to agree to a certain request. One way to increase your chances would be first to make a larger request of me, one that I will most likely turn down. Then, after I have refused, you would make the smaller request that you were really interested in all along. Provided that you have structured your requests skillfully, I should view your second request as a concession to me and should feel inclined to respond with a concession of my own, the only one I would have immediately open to me—compliance with your second request.

Commitment and Consistency

A Canadian study discovered something fascinating about people at the racetrack: Just after placing a bet, they are much more confident of their horse’s chances of winning than they are immediately before laying down that bet.

It is, quite simply, our nearly obsessive desire to be (and to appear) consistent with what we have already done. Once we have made a choice or taken a stand, we will encounter personal and interpersonal pressures to behave consistently with that commitment. Those pressures will cause us to respond in ways that justify our earlier decision.

If I can get you to make a commitment (that is, to take a stand, to go on record), I will have set the stage for your automatic and ill-considered consistency with that earlier commitment.

Once a stand is taken, there is a natural tendency to behave in ways that are stubbornly consistent with the stand.

Example: Residents as part of a survey he was taking and asked them to predict what they would say if asked to spend three hours collecting money for the American Cancer Society. Of course, not wanting to seem uncharitable to the survey taker or to themselves, many of these people said that they would volunteer. The consequence of this sly commitment procedure was a 700 percent increase in volunteers when, a few days later, a representative of the American Cancer Society did call and ask for neighborhood canvassers.

Be very careful about agreeing to trivial requests. Our best evidence of what people truly feel and believe comes less from their words than from their deeds.

As a commitment device, a written declaration has some great advantages. Once we write something down, we do our best to stick to it. Unless there is strong evidence to the contrary, observers automatically assume that someone who makes such a statement means it. And as we know, what those around us think is true of us is enormously important in determining what we ourselves think is true.

There is something magical about writing things down. So set a goal and write it down. When you reach that goal, set another and write that down. You’ll be off and running.

Companies have since learned a beautifully simple trick that cuts the number of such cancellations drastically. They merely have the customer, rather than the salesman, fill out the sales agreement.

The reluctance to change our positions also goes for a public pronouncement: In one study, when six- or twelve-person experimental juries were deciding a close case, hung juries were significantly more frequent if the jurors had to express their opinions with a visible show of hands rather than by secret ballot. Once jurors had stated their initial views publicly, they were reluctant to allow themselves to change publicly.

Social proof

The principle states that one means we use to determine what is correct is to find out what other people think is correct. The principle applies especially to the way we decide what constitutes correct behavior.

The principle of social proof also says: The greater the number of people who find any idea correct, the more the idea will be correct.

Why, is canned laughter so popular with television executives?

The answer is at once simple and intriguing: Experiments have found that the use of canned merriment causes an audience to laugh longer and more often when humorous material is presented and to rate the material as funnier. In addition, some evidence indicates that canned laughter is most effective for poor jokes.

In the case of canned laughter, the problem comes when we begin responding to social proof in such a mindless and reflexive fashion that we can be fooled by partial or fake evidence. The folly is that we do so in response to patently fraudulent laughter. Somehow, one disembodied feature of humor—a sound—works like the essence of humor.

The television executives are exploiting our preference for shortcuts, our tendency to react automatically on the basis of partial evidence. They know that their tapes will cue our tapes.

Advertisers love to inform us when a product is the “fastest-growing” or “largest-selling” because they don’t have to convince us directly that the product is good, they need only say that many others think so, which seems proof enough.

David Phillips, and he points a convincing finger at something called the “Werther effect.”

The story of the Werther effect is both chilling and intriguing. More than two centuries ago, the great man of German literature, Johann von Goethe, published a novel entitled Die Leiden des jungen Wertheras (The Sorrows of Young Werther). The book, in which the hero, named Werther, commits suicide, had a remarkable impact. Not only did it provide Goethe with immediate fame, but it also sparked a wave of emulative suicides across Europe. So powerful was this effect that authorities in several countries banned the novel.*\

It is Phillips’s argument that certain troubled people who read of another’s self-inflicted death kill themselves in imitation. In a morbid illustration of the principle of social proof, these people decide how they should act on the basis of how some other troubled person has acted.

This can also be traced back to grand opera in the 1820s with 'claquing' to get audiences to applaud.


Used in hundreds of ways by strangers to have us comply with their requests. Tupperware parties were a great example, where a company managed to sell $2.5 million dollars' worth of plastic containers, per day!

The  power of the Tupperware party came from a particular arrangement that trades on the liking rule. Despite the entertaining and persuasive salesmanship of the Tupperware demonstrator, the true request to purchase the product does not come from this stranger; it comes from a friend to every woman in the room who invited them into her home.

The strength of that social bond is twice as likely to determine product purchase as is preference for the product itself.

Other key elements at play with this principle:

Physical Attractiveness

The response itself falls into a category that social scientists call “halo effects.” A halo effect occurs when one positive characteristic of a person dominates the way that person is viewed by others. And the evidence is now clear that physical attractiveness is often such a characteristic.

Research has shown that we automatically assign to good-looking individuals such favorable traits as talent, kindness, honesty, and intelligence.

Attractive defendants were twice as likely to avoid jail as the unattractive ones.


We like people who are similar to us. Requesters can manipulate similarity to increase liking and compliance is to claim that they have backgrounds and interests similar to ours.


We are phenomenal suckers for flattery. That is all.

Conditioning and Association

“I had one guy call and tell me that if it snowed over Christmas, I wouldn’t live to see New Year’s,” said Bob Gregory, who has been the forecaster at WTHR-TV in Indianapolis for nine years.

A lot of strange behavior can be explained by the fact that people understand the association principle well enough to strive to link themselves to positive events and separate themselves from negative events—even when they have not caused the events.

"The nature of bad news infects the teller," Antony and Cleopatra.

Researchers found that students conveyed the information very differently, depending on its quality. When the news was positive, the tellers were sure to mention that feature: “You just got a phone call with great news. Better see the experimenter for the details.” But when the news was unfavorable, they kept themselves apart from it: “You just got a phone call. Better see the experimenter for the details.” Obviously, the students had previously learned that, to be liked, they should connect themselves to good news but not bad news.

As distinguished author Isaac Asimov put it in describing our reactions to the contests we view, “All things being equal, you root for your own sex, your own culture, your own locality…and what you want to prove is that you are better than the other person. Whomever you root for represents you; and when he wins, you win.”

Note also that nothing similar occurs in the case of failure. No television viewer will ever hear the chant, “We’re in last place! We’re in last place!”


Is this authority truly an expert?” question can be so valuable: It brings our attention to the obvious. It channels us effortlessly away from a focus on possibly meaningless symbols to a consideration of genuine authority credentials.

Studies investigating the way in which authority status affects perceptions of size have found that prestigious titles lead to height distortions.

A man was introduced to different groups telling, giving him a different job description in each. After he left the room, each class was asked to estimate his height. It was found that with each increase in status, the same man grew in perceived height by an average of a half inch, so that as the “professor” he was seen as two and a half inches taller than as the “student.”

That 95 percent of regular staff nurses complied unhesitatingly with a patently improper instruction of this sort must give us all great reason for concern as potential hospital patients… recent U.S. Health Care Financing Administration estimate of a 12 percent daily-medication error rate in American hospitals, stays of longer than a week make it likely that we will be recipients of such an error.


Opportunities seem more valuable to us when their availability is limited.

The idea of potential loss plays a large role in human decision making. In fact, people seem to be more motivated by the thought of losing something than by the thought of gaining something of equal value.

The intriguing thing about the effects of censoring information is not that audience members want to have the information more than they did before; that seems natural. Rather, it is that they come to believe in the information more, even though they haven’t received it. For example, when University of North Carolina students learned that a speech opposing coed dorms on campus would be banned, they became more opposed to the idea of coed dorms. Thus, without ever hearing the speech, they became more sympathetic to its argument.

This raises the worrisome possibility that especially clever individuals holding a weak or unpopular position can get us to agree with that position by arranging to have their message restricted.

Optimal conditions

In a study by Stephen Worchel, participants in a consumer-preference study were given a chocolate-chip cookie from a jar and asked to taste and rate its quality. For half of the raters, the jar contained ten cookies; for the other half, it contained just two. As we might expect from the scarcity principle, when the cookie was one of the only two available, it was rated more favorably than when it was one of ten. The cookie in short supply was rated as more desirable to eat in the future, more attractive as a consumer item, and more costly than the identical cookie in abundant supply.

The real worth of the cookie study comes from two additional findings.

With this procedure, the researchers were seeking to answer a question about types of scarcity: Do we value more those things that have recently become less available to us, or those things that have always been scarce? In the cookie experiment, the answer was plain. The drop from abundance to scarcity produced a decidedly more positive reaction to the cookies than did constant scarcity.

James C. Davies, who states that we are most likely to find revolutions where a period of improving economic and social conditions is followed by a short, sharp reversal in those conditions. Revolutionaries are more likely to be those who have been given at least some taste of a better life.


Very often in making a decision about someone or something, we don’t use all the relevant available information; we use, instead, only a single, highly representative piece of the total.

Joe Pyne: "So I guess your long hair makes you a woman."
Frank Zappa: "So, I guess your wooden leg makes you a table!"

After eons of slow accumulation, human knowledge has snowballed into an era of momentum-fed, multiplicative, monstrous expansion.

And the scientific information explosion is not limited to such arcane arenas as molecular chemistry or quantum physics but extends to everyday areas of knowledge where we strive to keep ourselves current—health, child development, nutrition, and the like. What’s more, this rapid growth is likely to continue, since 90 percent of all scientists who have ever lived are working today.

Because technology can evolve much faster than we can, our natural capacity to process information is likely to be increasingly inadequate to handle the surfeit of change, choice, and challenge that is characteristic of modern life.

Compliance professionals who play fairly by the rules of shortcut response are not to be considered the enemy; on the contrary, they are our allies in an efficient and adaptive process of exchange. The proper targets for counteraggression are only those individuals who falsify, counterfeit, or misrepresent the evidence that naturally cues our shortcut responses.

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