24Influence

Robert B. Cialdini, Influence: The Psychology of Persuasion, William Morrow, 1984; new and expanded edition, HarperBusiness, 2021

Linked to 21 chapters: supports 7 · contradicts 5 · mechanism 15 · same claim 3 · pairing 7

Cialdini opens by calling himself a lifelong patsy, an easy mark for peddlers and fundraisers who kept finding himself in possession of magazine subscriptions he did not want. He turned that into a research question — what makes one person say yes to another — and then decided the laboratory could not answer it alone. For three years he answered advertisements under a disguised identity and took jobs as a sales trainee, a fundraiser and a busboy, on the reasoning that people whose livelihood depends on producing compliance have been selected for knowing what works. What he brought back was a claim about structure. The thousands of tactics in use fall into seven categories, each governed by one psychological principle, and each principle exists because the cue it responds to is normally a good guide. The mechanism underneath is borrowed from ethology: a fixed-action pattern in which one feature of a situation, not the situation as a whole, sets off a complete sequence of behaviour. Cialdini calls it click, run. A turkey mothers anything that goes cheep-cheep; a shopper who knows nothing about turquoise judges it by price; a hospital ward defers to a lab coat. The shortcut is efficient and it would be irrational to abandon it, since nobody has time to appraise every person and event afresh. But a shortcut that answers to one feature can be set off by anyone who can counterfeit that feature, and the book is a catalogue of the people who do. Its closing argument is that the pace and clutter of modern life push us toward single-feature responding even on matters we care about, so that the shortcuts are becoming more necessary at the same time as they become more profitable to fake.

Levers of influence

The book's first example is a friend who ran a jewellery shop in Arizona and could not sell a case of turquoise. Leaving on a buying trip, she scrawled an instruction to halve the prices; the saleswoman read the ½ as a 2, and the entire allotment sold at twice the asking price. Cialdini explains it with a mother turkey. Almost all of a turkey's maternal behaviour is triggered by the cheep-cheep of chicks, and by nothing else: a stuffed polecat, the natural predator a turkey would ordinarily attack, is gathered under her wing if it carries a recorder playing the sound, and attacked again the moment the recorder is switched off. Ethologists call these sequences fixed-action patterns, and what starts them is not the rival or the chick as a whole but a trigger feature — a clump of redbreast feathers will draw a male robin's full territorial attack while a perfect stuffed robin without them is ignored.

The human parallel Cialdini uses is Ellen Langer's photocopier study. Asking to jump a library queue with five pages succeeded 60 per cent of the time; adding a reason, because I'm in a rush, raised it to 94 per cent. A third version supplied the word without the reason — because I have to make some copies — and still got 93 per cent. The word did the work, not the justification. The turquoise buyers were running a similar program on the rule that expensive equals good, which normally holds and which they had no other way to apply, since they knew nothing about turquoise. The same rule makes an identical painkiller feel more effective against electric shocks when it is said to cost $2.50 a unit rather than ten cents. Cialdini's reading is not that the tourists were foolish. They were betting shortcut odds, and over a lifetime that bet pays.

Alongside the trigger features sits a second, quieter lever: perceptual contrast. Two things presented in sequence seem further apart than they are. Students who put one hand in cold water and one in hot, then both into water at room temperature, feel the same bucket as hot in one hand and cold in the other. Clothing stores instruct staff to sell the suit before the sweater; an estate agent Cialdini rode with kept two overpriced wrecks on the books as "setup" properties, to be shown before the house he meant to sell; car dealers price the options after the car. What makes contrast valuable to the people who use it is that it leaves no trace of having been used, which Cialdini generalises into the image that organises the book. The practitioner works like a jujitsu fighter, supplying almost no force and engaging instead a principle already present, so that even the victim reads the outcome as natural rather than arranged.

Aviation investigators found a recurring pattern of crews failing to correct an obvious captain's error, which the industry named Captainitis; the book reproduces the black-box exchange from the airliner that went into the Potomac with ice on its wings, in which the copilot says three times that the reading does not look right and then defers. Controlled thinking is available: students told that a proposed graduation examination would affect them attended to the quality of a speaker's arguments, while students told it would arrive after they left attended only to his credentials. Cialdini says that does not comfort him. Desire is not enough, the ability has to be there too, and time pressure, distraction, arousal and fatigue take it away.

Relationship, uncertainty, action

The 2021 edition sequences the seven levers according to a model of Gregory Neidert's, which sorts a persuader's aims into three. Where the goal is to cultivate a relationship, reciprocation, liking and unity apply; where it is to reduce uncertainty, social proof and authority; where it is to move someone from a decision to an act, commitment and scarcity. Each chapter ends with a defence, and none of the defences is refusal. Cialdini's position throughout is that the levers are usually right and the enemy is the forgery, so what he asks the reader to develop is a way of noticing when the cue has been manufactured.

Reciprocation underwrites trade and the division of labour, because a shared obligation to repay lets people give things away without losing them; it is enforced hard, and that is what makes it exploitable. Two properties do the damage: the gift need not be asked for, so the giver chooses who is indebted, and the return need not match the gift. The rule also runs on concessions rather than favours, which is Cialdini's reading of the Watergate break-in, approved as the third and smallest of three shrinking proposals. Liking runs on attractiveness, similarity, compliments, contact and bare association; Cialdini's most careful section is on contact, which builds liking under cooperation and destroys it under competition, so that the boys of Muzafer and Carolyn Sherif's camp study, split into Eagles and Rattlers, stopped raiding each other only when a stuck food truck and a broken water pipe gave them a shared goal.

Scarcity runs on two engines: the shortcut that hard-to-get things are usually better, and Jack Brehm's psychological reactance, in which a curtailed freedom makes both the thing and the freedom more wanted. Newly scarce beats always scarce, and scarcity created by rivals beats scarcity created by accident, so the dangerous configuration is a supply that has just contracted with other people visibly competing for it. Commitment and consistency has the longest chapter and the most exact recipe: a commitment reshapes self-image to the degree that it is active, public, effortful and freely chosen, and the last of those matters more than the other three together, because a large reward or a strong threat supplies an excuse and leaves the self-image untouched. Unity, added in 2021, is the one Cialdini separates carefully from liking: not that someone is like us but that they are one of us, an identity in which another member's conduct moves one's own self-esteem. Its pull is modulated rather than constant, and its characteristic crime is affinity fraud.

Truths are us

Social proof says that we work out what is correct by finding out what other people think is correct, and that we judge an action to be right in proportion to the number of people we see performing it. Cialdini's opening examples cost almost nothing: Beijing restaurants that labelled certain dishes their most popular sold 13 to 20 per cent more of them; a London brewery's pub put a truthful sign on the bar and doubled sales of its porter; McDonald's outlets that told customers the McFlurry was the favourite sold 55 per cent more. Nursery children terrified of dogs watched another child play with one for twenty minutes a day; after four days, 67 per cent would sit alone in a playpen with the dog. Film worked as well as a live demonstration, and best of all when it showed several children.

The book's set piece on the principle is the Chicago doomsday group studied from the inside by Leon Festinger, Henry Riecken and Stanley Schachter. Before the predicted flood the members were secretive, refused interviews and made no attempt to recruit; they had quit jobs, given away possessions and cut the metal eyelets out of their shoes. When midnight passed and no spacecraft came they sat in silence, and by half past four the group was close to dissolution. Then a message arrived explaining that their small circle had spread so much light that the world had been spared, and a second instructing them to publicise it, and within minutes the same people were telephoning newspapers and admitting every visitor. Cialdini's reading is that physical proof had been destroyed, so the only kind left was social. The more people hold an idea, the truer it seems to any one of them; conviction had failed, so conversion had to serve.

Three conditions decide how hard the principle bites. The first is uncertainty. Unfamiliar customers were the ones most swayed by the popularity label; Sylvan Goldman's shopping cart, invented in 1934, sat unused until he hired shoppers to wheel the carts around the store. The corrosive version of uncertainty is pluralistic ignorance, in which every onlooker is checking the others for a cue and every onlooker therefore sees a room of people who appear unconcerned. Cialdini uses the Kitty Genovese case as the story that launched the research and is careful, in this edition, to say that the details of the neighbours' inaction have since been discredited by researchers who found the journalism shoddy. What survives is the mechanism, and he illustrates it with a Chicago woman killed beside the Art Institute in daylight, where one man heard a scream and did not investigate because nobody else seemed to be paying attention. When there is no ambiguity the picture reverses: in staged accidents in Florida where the injury was obvious, help came 100 per cent of the time, and 90 per cent even where it meant handling live wires. The bystanders, Cialdini insists, are unsure rather than unkind, so the victim's task is to destroy the uncertainty — not to moan, and not merely to shout, but to pick one person and assign the act: you, in the blue jacket, call an ambulance.

The second condition is number. A lone person staring at an empty patch of sky is ignored; a group of starers turns 80 per cent of a street's heads, and the effect grows with the group up to about twenty. Paid applause, organised in Paris in 1820 and sold by the head, is Cialdini's historical case; the laugh track is its descendant. Numbers work for three separate reasons. They suggest validity, which is why raising the share of customers said to prefer a brand raises preference for it. They suggest feasibility, which explains a result Cialdini did not expect: of four messages delivered weekly to households, the three appealing to the environment, to responsibility and to the power bill were beaten more than threefold by a truthful statement that most of their neighbours were trying to conserve. And they suggest social acceptance; participants in a brain-scanner study conformed more to four people than to four computers they rated equally reliable, and the region associated with negative emotion lit up when they held out, which the researchers called the pain of independence.

The third condition is similarity, and here the evidence turns grim. David Phillips traced the Werther effect — named for the wave of imitative suicides that followed Goethe's 1774 novel — through twenty years of American statistics, and found that in the two months after a front-page suicide story an average of fifty-eight more people than usual killed themselves, only in the regions where the story ran and in proportion to the publicity. Fatal car and air crashes rise at the same time, and the pattern rules out both a common-cause and a bereavement account: stories of a lone suicide are followed by single-fatality wrecks and stories of murder-suicide by multiple-fatality wrecks. Phillips predicted and found that the crashes are also deadlier, with average deaths in an airliner crash more than three times higher in the week after a story than the week before. The clincher for Cialdini is the matching of ages: when the story concerned a young person, young drivers died in single-car crashes; when it concerned an older person, older drivers did.

Uncertainty and similarity together produce the case Cialdini treats as the most spectacular act of compliance of his lifetime. The People's Temple moved from San Francisco to the Guyanese jungle in 1977, and on 18 November 1978, after a congressman and four others were murdered, 910 people took poison in turn and in orderly rows. Louis Jolyon West, who had watched the group for eight years, said afterwards that it would not have happened in California, and Cialdini builds his account on that sentence. The relocation put the members somewhere they knew nothing about, which maximised uncertainty, and left them no similar others outside the settlement, which maximised peer influence; the first few who drank without hesitation supplied one piece of social evidence, and the silent composure of everyone else — each of them also waiting to see what was correct — supplied the second. Jim Jones's genius, on this reading, was not charisma but an understanding that no leader can persuade a thousand people singly, and that a leader who persuades a sizeable fraction can let the rest be persuaded by them.

The chapter ends with what Cialdini calls the big mistake, made by nearly every public-service campaign. Inside the lament look at all the people doing this undesirable thing sits the message look at all the people doing it. The sign at the Petrified Forest National Park, announcing that fourteen tons of petrified wood are stolen every year, once moved a scrupulously honest visitor to whisper that they had better get theirs too. Cialdini and colleagues tested it. Against a base rate of 2.95 per cent of visitors taking fossils, a sign depicting three thieves nearly tripled theft to 7.92 per cent, while a sign depicting a lone thief cut it to 1.67. The same reversal has been found for eating-disorder education, teenage suicide prevention and alcohol-resistance role-play, each of which taught participants that the behaviour was commoner than they had thought. Where there is no majority to point to, his revised advice is to look for a truthful trend, since people project a change in the direction it is already moving: students told that only a minority of their peers conserved water used the most of all, and students told that the conserving minority was growing used the least.

His defence is framed as an autopilot worth keeping, since the information it flies on is usually sound, so the task is to notice when the data have been corrupted. Two things corrupt them. Social evidence can be falsified — staged queues outside half-empty nightclubs, salted tip jars, planted reviews, actors hired to praise a film, paid queues outside twenty Polish shops on the day the iPhone launched — and Cialdini's response is unusually aggressive: boycott, complain, name the agency. Or the evidence can be innocently wrong and then snowball, as in the Singapore bank that had to close its doors because a bus strike put a crowd outside it. The remedy for that is to look up periodically and compare the crowd with the instruments — aviation researchers found that pilots who crashed on landing had attended less to the worsening weather than to the fact that a line of aircraft before them had got down safely.

Directed deference

The authority chapter opens with an experiment run by the British government's behavioural unit on investment bankers asked to donate a day's salary. A plain letter produced 5 per cent compliance; a celebrity's endorsement, 7; a packet of sweets handed over on arrival, 11; a personalised letter from the chief executive, 12; the sweets and the letter together, 17. The letter drew on both senses of the word. The chief executive was in authority, a boss who could affect their careers and would know whether they complied, and he was also an authority, who had demonstrated knowledge of the charities and of the campaign's worth.

Then comes Milgram, narrated from the learner's chair: the grey lab coat and the clipboard, the electrodes, the assurance that the shocks will cause no permanent tissue damage, the increase of fifteen volts per error, the demand to be let out at 150 volts, the silence that follows it. About two thirds of the forty participants went to the last of thirty switches, 450 volts, and stopped only when the researcher ended the session; almost none quit when the victim first asked to be released. Milgram had asked colleagues, graduate students and psychology majors to predict the figure and been told one or two per cent, and thirty-nine psychiatrists had said one in a thousand. He dismissed the alternative explanations from his own variations. Women obeyed at the same rate; personality scales found no group pathology; and when the victim announced a heart condition and said it was being affected, 65 per cent still went to the end. The participants plainly hated it, as the observer's description of a poised businessman records — within twenty minutes a twitching wreck who pushed a fist into his forehead, muttered a plea to stop, and obeyed to the end. What settles it for Cialdini is the reversals. When the researcher told the Teacher to stop and the victim demanded he continue, not one person gave another shock; when the researcher was strapped in the chair and a fellow volunteer gave the orders, again not one; and when two researchers issued contradictory instructions, every participant, unable to identify the bigger boss, stopped. Milgram's own summary named it "the extreme willingness of adults to go to almost any lengths on the command" of an authority.

Obedience of this kind is mostly sensible, which is why it has become automatic. Parents and teachers did know more; employers, judges and physicians usually do. Medicine is where Cialdini shows the automation and its cost together. Hierarchies there are steep and deference to doctors' orders is long established, so an error at the top is unlikely to be caught below. He reports a physician who abbreviated a prescription for ear drops as "place in R ear" and a duty nurse who put the drops in the patient's anus; neither the nurse nor the patient questioned a rectal treatment for an earache. The formal version is a study in which a researcher telephoned twenty-two nurses' stations, identified himself as a hospital physician the nurse had never met, and ordered twenty milligrams of an unauthorised drug whose containers named ten milligrams as the maximum daily dose, in violation of the policy against telephone prescriptions. After 95 per cent of the calls the nurse collected the dose and set off for the patient's room, and was stopped by an observer. The researchers concluded that of the two professional intelligences meant to protect the patient, "one of these intelligences is, for all practical purposes, nonfunctioning."

What the nurses responded to was not authority but its most easily forged token, a bare title. Cialdini takes the three tokens in turn. Titles are hard to earn and simple to claim, and they distort perception: a visitor introduced to five Australian classes as student, demonstrator, lecturer, senior lecturer and professor gained half an inch of estimated height at each rank, two and a half inches in all. Clothes work as well. Leonard Bickman's requester, asking passers-by to pick up a bag or give a stranger a dime for a parking meter, was obeyed by 42 per cent in street clothes and 92 per cent in a security guard's uniform — and students asked to predict the uniformed figure guessed 63 per cent. A man crossing against the light in Texas drew three and a half times as many pedestrians into traffic when he wore a pressed business suit. Trappings do the same work: a designer label on a shirt produced 79 per cent more compliance with an unpaid survey and four times the donations at the door, and half the drivers behind a luxury car stopped at a green light waited fifteen seconds without touching the horn, where almost all honked at an old economy model and two rammed it. In every one of these studies the participants underestimated the effect on themselves, which is the property Cialdini thinks accounts for how well the lever works.

The second half of the chapter is about being an authority rather than in one, which Cialdini prefers on the practical ground that orders generate resentment while expertise generates willingness. A credible authority has two components. Expertise is the first, and it spreads: a wall of diplomas raises ratings of a therapist's kindness and interest as well as of their competence, and a single expert opinion piece lifted agreement among general readers by twenty percentage points regardless of their age, sex or politics. The second is trustworthiness, and the chapter's most exportable finding is that it can be established quickly rather than slowly, by naming a weakness before naming the strengths. Trial lawyers who concede a weak point before the opposing counsel raises it are judged more credible and win more often; candidates who begin with something good about an opponent gain in preference; Domino's advertised in 2009 that its pizza had been bad, and sales and the share price followed. Warren Buffett opens his annual reports with a mistake, and in a year with no misstep to report he reached back to the 1993 purchase of Dexter Shoe for $434 million, whose value promptly went to zero, and to the promise it extracted from him never again to pay in Berkshire stock.

The defence is two questions. The first, is this authority truly an expert, sends attention from the symbol to the credential and separates the relevant expert from the irrelevant one: the suited jaywalker knew no more about crossing the road than the people who followed him. The second, how truthful can this expert be expected to be, asks what they gain. On the second question he warns that the weakness-first move is itself a tactic, and gives it a face: Vincent, the most profitable waiter in the restaurant where Cialdini worked as a busboy, who greeted the first order at a large table by glancing over his shoulder, leaning in and confiding that the dish was not at its best tonight, recommending two slightly cheaper ones — and who, having established himself as knowledgeable and disinterested in a single move, then chose the table's wine and sold them dessert.

Primitive consent for an automatic age

The last chapter argues that the mechanism is not a defect but a condition of being a finite creature in an environment of our own making. A mother turkey relies on one stimulus because her brain cannot register more; we have the better apparatus and have used it to build a world that outruns it. Cialdini dates the change by noting that John Stuart Mill, who died in 1873, is supposed to have been the last person who knew everything there was to know, and observes that the era named for information has never been called the age of knowledge, since information has to be processed before it becomes knowledge. Rushed, stressed, distracted or tired, we attend to less, and one reliable cue becomes the whole basis of the decision. Two consequences follow: the frequency of shortcut responding will rise, and so will the profit available from faking the cues.

The book's final position is therefore not detachment but partisanship. A practitioner who plays by the rules of shortcut responding is an ally — the advertiser who truthfully reports that a toothpaste sells best has supplied real evidence cheaply and left the reader's attention free for other things. The adversary is the one who manufactures the signal, and against that Cialdini recommends confrontation rather than evasion, on the grounds that what is damaged is the rule itself rather than the individual sale. He closes with one of his own purchases, a television he had not come in to buy, sold to him by a salesman who said it was the last one and that a woman had telephoned about it. Cialdini knew which lever was being pulled and bought it anyway, then went back the next morning to see whether the shelf was empty. It was, so he wrote a favourable review; had another set appeared, the review would have been a condemnation. The test he proposes is not whether a principle was used on you but whether the condition it reported was real.

Since 1984

The book has sold in the millions across more than forty languages, and its vocabulary — social proof, the foot in the door, reciprocity — has passed into the working language of marketing, fundraising and public health. Its evidence has had a harder four decades than its reputation. The field experiments have generally held. Descriptive-norm messaging of the kind Cialdini pioneered was deployed commercially through Opower, and Hunt Allcott's 2011 evaluation of those trials found savings of 1.4 to 3.3 per cent of household electricity, less than the threefold advantage over other messages suggests. The Petrified Forest result and the "most popular" labelling effects have been reproduced, and the Werther effect has survived best of all: a 2020 systematic review in the BMJ found that reports of a celebrity's suicide are followed by an eight to eighteen per cent rise in suicides over the next two months, larger when the method is described. The newest example in the 2021 edition is the weakest. The reported 28.9 per cent rise in adolescent suicides after 13 Reasons Why was reanalysed in 2020 and disappeared once the underlying upward trend was allowed for, with part of the rise beginning the month before release; the original authors dispute the reanalysis.

The two laboratory pillars of the authority chapter have fared differently. Milgram's basic result stands: Jerry Burger repeated the procedure in 2006 under modern ethical constraints, stopping at 150 volts, and found 70 per cent of participants continuing past the point where the victim first demands release, against Milgram's 82.5 per cent in the matching condition. What has been contested is the tidiness of the telling. Gina Perry's work in the Milgram archives documented that the experimenter departed from the four scripted prods, that many participants doubted the shocks were real, and that the twenty-four variations produced obedience from near zero to over ninety per cent, so that the familiar sixty-five is one condition rather than a constant. The nurse study has fared worse. In 1977 Rank and Jacobson reran it with a drug the nurses knew, at three times the recommended dose, ordered by a physician they could identify, and with colleagues available to consult; only two of eighteen complied. The obedience in the original depended on an unknown voice, an unknown drug and isolation, which is a more interesting result than the one the book reports and one the book does not mention.

The bystander literature has been corrected twice. The thirty-eight witnesses of the Genovese case were a newspaper's construction, as Manning, Levine and Collins established in 2007, and Cialdini says so in this edition, keeping the mechanism and dropping the parable. A 2019 study by Richard Philpot and colleagues then coded real closed-circuit footage of public conflicts in Amsterdam, Cape Town and Lancaster and found that someone intervened in about ninety-one per cent of them, and that more bystanders made intervention more likely rather than less. That does not overturn pluralistic ignorance, which is a claim about ambiguous situations, but it inverts the popular lesson drawn from it, and the advice to name one person and one act now rests on the narrower finding.

The 2021 edition answers some of this. It adds unity as a seventh principle, reorders the chapters by the three persuasive motives, expands the reader's reports in which correspondents describe a principle working on them, adds boxes on the migration of the tactics to e-commerce and social media, and moves the citations into narrative endnotes. What it does not do is revisit the studies whose replication record has changed. The parts that have aged best are the ones Cialdini took from watching practitioners rather than from any single experiment: that compliance tactics cluster into a small number of families, that each family works because the cue it exploits is normally informative, that its users understand the psychology better than their targets do, and that a shortcut can only be defended by noticing when its input has been forged.