The scientific study of the process of social influencehas been under way for well over half a century,beginning in earnest with the propaganda, publicinformation and persuasion programs of World

War II. Since that time, numerous social scientists have inves-tigated the ways in which one individual can influence anoth-er’s attitudes and actions. For the past 30 years, I have partic-ipated in that endeavor, concentrating primarily on the majorfactors that bring about a specific form of behavior change—compliance with a request. Six basic tendencies of human be-havior come into play in generating a positive response: re-ciprocation, consistency, social validation, liking, authorityand scarcity. As these six tendencies help to govern our busi-ness dealings, our societal involvements and our personal re-lationships, knowledge of the rules of persuasion can truly bethought of as empowerment.

Reciprocation

When the Disabled American Veterans organizationmails out requests for contributions, the appeal suc-

ceeds only about 18 percent of the time. But when the mailingincludes a set of free personalized address labels, the successrate almost doubles, to 35 percent. To understand the effect ofthe unsolicited gift, we must recognize the reach and power ofan essential rule of human conduct: the code of reciprocity.

All societies subscribe to a norm that obligates individu-als to repay in kind what they have received. Evolutionary se-lection pressure has probably entrenched the behavior in so-cial animals such as ourselves. The demands of reciprocitybegin to explain the boost in donations to the veterans group.Receiving a gift—unsolicited and perhaps even unwanted—

76 Scientific American February 2001 The Science of Persuasion

The Science of

Salespeople, politicians, friends and family all have a stake in

getting you to agree to their requests. Social psychology has

determined the basic principles that govern getting to “yes”

by Robert B. Cialdini

Hello there.

I hope you’ve enjoyed the magazine so far.Now I’d like to let you in on something ofgreat importance to you personally. Haveyou ever been tricked into saying yes? Everfelt trapped into buying something you did-n’t really want or contributing to some sus-picious-sounding cause? And have you everwished you understood why you acted inthis way so that you could withstand theseclever ploys in the future?

Yes? Then clearly this article is just right foryou. It contains valuable information on themost powerful psychological pressures thatget you to say yes to requests. And it’schock-full of new, improved research show-ing exactly how and why these techniqueswork. So don’t delay, just settle in and getthe information that, after all, you’ve al-ready agreed you want.

Copyright 2001 Scientific American, Inc.

convinced significant numbers of potential donors to returnthe favor.

Charitable organizations are far from alone in taking thisapproach: food stores offer free samples, exterminators offerfree in-home inspections, health clubs offer free workouts.Customers are thus exposed to the product or service, butthey are also indebted. Consumers are not the only ones whofall under the sway of reciprocity. Pharmaceutical companiesspend millions of dollars every year to support medical re-searchers and to provide gifts to individual physicians—activ-ities that may subtly influence researchers’ findings and phy-sicians’ recommendations. A 1998 study in the New EnglandJournal of Medicine found that only 37 percent of research-ers who published conclusions critical of the safety of calci-um channel blockers had received prior drug company sup-port. Among researchers whose conclusions supported thedrugs’ safety, however, the number of those who had receivedfree trips, research funding or employment skyrocketed—to100 percent.

Reciprocity includes more than gifts and favors; it alsoapplies to concessions that people make to one another. Forexample, assume that you reject my large request, and I thenmake a concession to you by retreating to a smaller request.You may very well then reciprocate with a concession of yourown: agreement with my lesser request. In the mid-1970s mycolleagues and I conducted an experiment that clearly illus-trates the dynamics of reciprocal concessions. We stopped arandom sample of passersby on public walkways and askedif they would volunteer to chaperone juvenile detention cen-ter inmates on a day trip to the zoo. As expected, very fewcomplied, only 17 percent.

For another random sample of passersby, however, we

began with an even larger request: to serve as an unpaidcounselor at the center for two hours per week for the nexttwo years. Everyone in this second sampling rejected the ex-treme appeal. At that point we offered them a concession. “Ifyou can’t do that,” we asked, “would you chaperone a groupof juvenile detention center inmates on a day trip to thezoo?” Our concession powerfully stimulated return conces-sions. The compliance rate nearly tripled, to 50 percent, com-pared with the straightforward zoo-trip request.

Consistency

In 1998 Gordon Sinclair, the owner of a well-known Chica-go restaurant, was struggling with a problem that afflicts

all restaurateurs. Patrons frequently reserve a table but, with-out notice, fail to appear. Sinclair solved the problem by ask-ing his receptionist to change two words of what she said tocallers requesting reservations. The change dropped his no-call, no-show rate from 30 to 10 percent immediately.

The two words were effective because they commissionedthe force of another potent human motivation: the desire tobe, and to appear, consistent. The receptionist merely modi-fied her request from “Please call if you have to change yourplans” to “Will you please call if you have to change yourplans?” At that point, she politely paused and waited for a

www.sciam.com Scientific American February 2001 77

STEV

EN A

DA

MS

AP

Phot

o

FREE SAMPLES carry a subtle price tag; they psychologically in-debt the consumer to reciprocate. Here shoppers get complimen-tary tastes of a new product, green ketchup. The samples primethe consumer to return the favor with a purchase. The novel col-or may also make the product seem scarce, an attractive attribute.

Copyright 2001 Scientific American, Inc.

response. The wait was pivotal becauseit induced customers to fill the pausewith a public commitment. And publiccommitments, even seemingly minorones, direct future action.

In another example, Joseph Schwarz-wald of Bar-Ilan University in Israel andhis co-workers nearly doubled mone-tary contributions for the handicappedin certain neighborhoods. The key fac-tor: two weeks before asking for contri-butions, they got residents to sign a pe-tition supporting the handicapped, thusmaking a public commitment to thatsame cause.

Social Validation

On a wintry morning in the late1960s, a man stopped on a busy

New York City sidewalk and gazedskyward for 60 seconds, at nothing inparticular. He did so as part of an ex-periment by City University of NewYork social psychologists Stanley Mil-gram, Leonard Bickman and LawrenceBerkowitz that was designed to find outwhat effect this action would have onpassersby. Most simply detoured orbrushed by; 4 percent joined the man inlooking up. The experiment was thenrepeated with a slight change. With themodification, large numbers of pedes-trians were induced to come to a halt,crowd together and peer upward.

The single alteration in the experi-ment incorporated the phenomenon ofsocial validation. One fundamentalway that we decide what to do in a sit-uation is to look to what others are do-ing or have done there. If many individ-

uals have decided in favor of aparticular idea, we are more likelyto follow, because we perceive theidea to be more correct, morevalid.

Milgram, Bickman and Berkowitzintroduced the influence of socialvalidation into their street experi-ment simply by having five menrather than one look up at nothing.With the larger initial set of upwardgazers, the percentage of New Yorkerswho followed suit more than quadru-pled, to 18 percent. Bigger initial sets ofplanted up-lookers generated an evengreater response: a starter group of 15led 40 percent of passersby to join in,nearly stopping traffic within oneminute.

Taking advantage of social valida-tion, requesters can stimulate our com-pliance by demonstrating (or merelyimplying) that others just like us havealready complied. For example, a studyfound that a fund-raiser who showedhomeowners a list of neighbors who haddonated to a local charity significantlyincreased the frequency of contributions;the longer the list, the greater the effect.Marketers, therefore, go out of theirway to inform us when their product isthe largest-selling or fastest-growing ofits kind, and television commercials reg-ularly depict crowds rushing to storesto acquire the advertised item.

Less obvious, however, are the cir-cumstances under which social valida-tion can backfire to produce the oppositeof what a requester intends. An exam-ple is the understandable but poten-tially misguided tendency of health edu-cators to call attention to a problem bydepicting it as regrettably frequent. In-formation campaigns stress that alco-hol and drug use is intolerably high,that adolescent suicide rates are alarm-

ing and that polluters are spoiling theenvironment. Although the claims areboth true and well intentioned, the cre-ators of these campaigns have missedsomething basic about the complianceprocess. Within the statement “Look atall the people who are doing this unde-sirable thing” lurks the powerful andundercutting message “Look at all thepeople who are doing this undesirablething.” Research shows that, as a con-sequence, many such programs boom-erang, generating even more of the un-desirable behavior.

For instance, a suicide interventionprogram administered to New Jerseyteenagers informed them of the highnumber of teenage suicides. Health re-searcher David Shaffer and his col-leagues at Columbia University foundthat participants became significantlymore likely to see suicide as a potentialsolution to their problems. Of greatereffectiveness are campaigns that hon-estly depict the unwanted activity asdamaging despite the fact that relativelyfew individuals engage in it.

Liking

“Affinity,” “rapport” and “affection”all describe a feeling of connection

between people. But the simple word“liking” most faithfully captures theconcept and has become the standarddesignation in the social science litera-ture. People prefer to say yes to those LU

ISM

.ALV

ARE

Z A

P Ph

oto

PUBLIC COMMITMENT of signing apetition influences the signer to behave con-sistently with that position in the future.

SOCIAL VALIDATIONtakes advantage of peerpressure to drive humanbehavior. Poorly applied,however, it can also under-mine attempts to curtaildeleterious activities, bypointing out their ubiq-uity: If everyone’s doingit, why shouldn’t I?

FORE

ST S

ERV

ICE–

USD

A

The Science of PersuasionCopyright 2001 Scientific American, Inc.

they like. Consider the worldwide suc-cess of the Tupperware Corporation andits “home party” program. Through thein-home demonstration get-together, thecompany arranges for its customers tobuy from a liked friend, the host, ratherthan from an unknown salesperson. Sofavorable has been the effect on pro-ceeds that, according to company liter-ature, a Tupperware party begins some-where in the world every 2.7 seconds.In fact, 75 percent of all Tupperwareparties today occur outside the individ-ualistic U.S., in countries where groupsocial bonding is even more importantthan it is here.

Of course, most commercial transac-tions take place beyond the homes offriends. Under these much more typicalcircumstances, those who wish to com-mission the power of liking employ tac-tics clustered around certain factorsthat research has shown to work.

Physical attractiveness can be such atool. In a 1993 study conducted by Pe-ter H. Reingen of Arizona State Univer-sity and Jerome B. Kernan of the Uni-versity of Cincinnati, good-lookingfund-raisers for the American HeartAssociation generated nearly twice asmany donations (42 versus 23 percent)as did other requesters. In the 1970sresearchers Michael G. Efran and E.W.J.Patterson of the University of Torontofound that voters in Canadian federalelections gave physically attractive can-didates several times as many votes asunattractive ones. Yet such voters in-sisted that their choices would never beinfluenced by something as superficialas appearance.

Similarity also can expedite a rap-port. Salespeople often search for, or out-right fabricate, a connection betweenthemselves and their customers: “Well,no kidding, you’re from Minneapolis? Iwent to school in Minnesota!” Fund-raisers do the same, with good results.

In 1994 psychologists R. Kelly Aune ofthe University of Hawaii at Manoa andMichael D. Basil of the University ofDenver reported research in which so-licitors canvassed a college campus ask-ing for contributions to a charity. Whenthe phrase “I’m a student, too” wasadded to the requests, donations morethan doubled.

Compliments also stimulate liking,and direct salespeople are trained in theuse of praise. Indeed, even inaccuratepraise may be effective. Research at theUniversity of North Carolina at ChapelHill found that compliments producedjust as much liking for the flattererwhen they were untrue as when theywere genuine.

Cooperation is another factor thathas been shown to enhance positivefeelings and behavior. Salespeople, for

example, often strive to be perceived bytheir prospects as cooperating partners.Automobile sales managers frequentlycast themselves as “villains” so the sales-person can “do battle” on the custom-er’s behalf. The gambit naturally leadsto a desirable form of liking by the cus-tomer for the salesperson, which pro-motes sales.

Authority

Recall the man who used social vali-dation to get large numbers of

passersby to stop and stare at the sky.He might achieve the opposite effectand spur stationary strangers into mo-tion by assuming the mantle of authori-ty. In 1955 University of Texas at Aus-tin researchers Monroe Lefkowitz,Robert R. Blake and Jane S. Mouton

www.sciam.com

RIC

FIE

LD A

P Ph

oto

FAMILIAR FACES sell products. Friends(who are already liked) are powerful sales-people, as Tupperware Corporation dis-covered. Strangers can co-opt the trappingsof friendship to encourage compliance.

BEHOLD THE POWER of authority.Certainly not lost on the National RifleAssociation is that the authority inherentin such heroic figures as Moses, El Cidand Ben-Hur is linked to the actor whoportrayed them, Charlton Heston.

TUPP

ERW

ARE

(195

8) A

P Ph

oto

Copyright 2001 Scientific American, Inc.

discovered that a man could increase by350 percent the number of pedestrianswho would follow him across the streetagainst the light by changing one simplething. Instead of casual dress, he donnedmarkers of authority: a suit and tie.

Those touting their experience, ex-pertise or scientific credentials may betrying to harness the power of authori-ty: “Babies are our business, our onlybusiness,” “Four out of five doctors rec-ommend,” and so on. (The author’s bi-ography at the end of this article in partserves such a purpose.) There is nothingwrong with such claims when they arereal, because we usually want the opin-ions of true authorities. Their insightshelp us choose quickly and well.

The problem comes when we are sub-jected to phony claims. If we fail to think,as is often the case when confronted byauthority symbols, we can easily besteered in the wrong direction by ersatzexperts—those who merely present theaura of legitimacy. That Texas jaywalk-er in a suit and tie was no more an au-thority on crossing the street than therest of the pedestrians who nonethelessfollowed him. A highly successful adcampaign in the 1970s featured actorRobert Young proclaiming the healthbenefits of decaffeinated coffee. Youngseems to have been able to dispense thismedical opinion effectively because herepresented, at the time, the nation’smost famous physician. That MarcusWelby, M.D., was only a character on aTV show was less important than theappearance of authority.

Scarcity

While at Florida State University inthe 1970s, psychologist Stephen

West noted an odd occurrence aftersurveying students about the campuscafeteria cuisine: ratings of the foodrose significantly from the week before,even though there had been no changein the menu, food quality or prepara-tion. Instead the shift resulted from anannouncement that because of a fire,cafeteria meals would not be availablefor several weeks.

This account highlights the effect ofperceived scarcity on human judgment.A great deal of evidence shows that

items and opportunities become moredesirable to us as they become less avail-able. For this reason, marketers trum-pet the unique benefits or the one-of-a-kind character of their offerings. It isalso for this reason that they consistentlyengage in “limited time only” promo-tions or put us into competition withone another using sales campaignsbased on “limited supply.”

Less widely recognized is that scarci-ty affects the value not only of com-modities but of information as well. In-formation that is exclusive is more per-suasive. Take as evidence the dissertationdata of a former student of mine, Am-ram Knishinsky, who owns a companythat imports beef into the U.S. and sellsit to supermarkets. To examine the ef-fects of scarcity and exclusivity on com-pliance, he instructed his telephone sales-people to call a randomly selected sam-ple of customers and to make a standardrequest of them to purchase beef. Healso instructed the salespeople to do thesame with a second random sample ofcustomers but to add that a shortage ofAustralian beef was anticipated, whichwas true, because of certain weatherconditions there. The added informa-tion that Australian beef was soon tobe scarce more than doubled purchases.

Finally, he had his staff call a thirdsample of customers, to tell them (1)about the impending shortage of Aus-tralian beef and (2) that this informa-tion came from his company’s exclusivesources in the Australian NationalWeather Service. These customers in-creased their orders by more than 600percent. They were influenced by a

scarcity double whammy: not only wasthe beef scarce, but the information thatthe beef was scarce was itself scarce.

Knowledge Is Power

Ithink it noteworthy that many of thedata presented in this article have

come from studies of the practices ofpersuasion professionals—the market-ers, advertisers, salespeople, fund-rais-ers and their comrades whose financialwell-being depends on their ability toget others to say yes. A kind of naturalselection operates on these people, asthose who use unsuccessful tactics soongo out of business. In contrast, thoseusing procedures that work well willsurvive, flourish and pass on these suc-cessful strategies [see “The Power ofMemes,” by Susan Blackmore; Scien-tific American, October 2000]. Thus,over time, the most effective principlesof social influence will appear in therepertoires of long-standing persuasionprofessions. My own work indicatesthat those principles embody the sixfundamental human tendencies exam-ined in this article: reciprocation, con-sistency, social validation, liking, au-thority and scarcity.

From an evolutionary point of view,each of the behaviors presented wouldappear to have been selected for in ani-mals, such as ourselves, that must findthe best ways to survive while living insocial groups. And in the vast majorityof cases, these principles counsel us cor-rectly. It usually makes great sense torepay favors, behave consistently, fol-low the lead of similar others, favor the

80 Scientific American February 2001

PETE

R B

ARR

ERA

S A

P Ph

oto

LIMITED OFFER of toys available for ashort time often creates a figurative feedingfrenzy at local fast-food establishments.Scarcity can be manufactured to make acommodity appear more desirable.

The Science of PersuasionCopyright 2001 Scientific American, Inc.

requests of those we like, heed legiti-mate authorities and value scarce re-sources. Consequently, influence agentswho use these principles honestly do usa favor. If an advertising agency, for in-stance, focused an ad campaign on thegenuine weight of authoritative, scien-tific evidence favoring its client’s head-ache product, all the right people wouldprofit—the agency, the manufacturer andthe audience. Not so, however, if theagency, finding no particular scientificmerit in the pain reliever, “smuggles”the authority principle into the situa-tion through ads featuring actors wear-ing lab coats.

Are we then doomed to be helplesslymanipulated by these principles? No.By understanding persuasion techniques,we can begin to recognize strategies andthus truly analyze requests and offer-ings. Our task must be to hold persua-

sion professionals accountable for theuse of the six powerful motivators andto purchase their products and services,support their political proposals or do-nate to their causes only when they haveacted truthfully in the process.

If we make this vital distinction in ourdealings with practitioners of the persua-sive arts, we will rarely allow ourselvesbe tricked into assent. Instead we willgive ourselves a much better option: tobe informed into saying yes. Moreover,as long as we apply the same distinctionto our own attempts to influence others,we can legitimately commission the sixprinciples. In seeking to persuade bypointing to the presence of genuine ex-pertise, growing social validation, perti-nent commitments or real opportunitiesfor cooperation, and so on, we serve theinterests of both parties and enhance thequality of the social fabric in the bargain.

www.sciam.com Scientific American February 2001 81

The Author

ROBERT B. CIALDINI is Regents’ Professor of Psychology at ArizonaState University, where he has also been named Distinguished GraduateResearch Professor. He has been elected president of the Society of Per-sonality and Social Psychology. Cialdini’s book Influence, which wasthe result of a three-year study of the reasons why people comply withrequests in everyday settings, has appeared in numerous editions andbeen published in nine languages. He attributes his long-standing inter-est in the intricacies of influence to the fact that he was raised in an en-tirely Italian family, in a predominantly Polish neighborhood, in a his-torically German city (Milwaukee), in an otherwise rural state.

Further Information

Psychology of Attitude Change and Social Influence.Phillip G. Zimbardo and Michael R. Leippe. Temple UniversityPress, 1991.

Bargaining for Advantage. G. Richard Shell. Viking, 1999.Age of Propaganda: The Everyday Use and Abuse of Persua-sion. Anthony J. Pratkanis. W. H. Freeman and Company, 2000.

Influence: Science and Practice. Fourth edition. Robert B.Cialdini. Allyn & Bacon, 2001.

For regularly updated information about the social influenceprocess, visit www.influenceatwork.com

DU

SAN

PET

RIC

IC

Influence across Cultures

Do the six key factors in the social influ-ence process operate similarly across

national boundaries? Yes,but with a wrinkle.The citizens of the world are human,after all,and susceptible to the fundamental tenden-cies that characterize all members of ourspecies. Cultural norms, traditions and expe-riences can, however, modify the weightbrought to bear by each factor.

Consider the results of a report published this year by StanfordUniversity’s Michael W.Morris, Joel M.Podolny and Sheira Ariel,whostudied employees of Citibank, a multinational financial corpora-tion. The researchers selected four societies for examination: theU.S., China, Spain and Germany. They surveyed Citibank brancheswithin each country and measured employees’willingness to com-ply voluntarily with a request from a co-worker for assistance with atask. Although multiple key factors could come into play, the mainreason employees felt obligated to comply differed in the four na-tions. Each of these reasons incorporated a different fundamentalprinciple of social influence.

Employees in the U.S. took a reciprocation-based approach tothe decision to comply. They asked the question, “What has thisperson done for me recently?” and felt obligated to volunteer if

they owed the requester a favor. Chineseemployees responded primarily to authori-ty, in the form of loyalties to those of highstatus within their small group. They asked,“Is this requester connected to someone inmy unit, especially someone who is high-ranking?” If the answer was yes, they felt re-quired to yield.

Spanish Citibank personnel based the de-cision mostly on liking/friendship.They were

willing to help on the basis of friendship norms that encouragefaithfulness to one’s friends, regardless of position or status. Theyasked, “Is this requester connected to my friends?” If the answerwas yes, they were especially likely to want to comply.

German employees were most compelled by consistency, offer-ing assistance in order to be consistent with the rules of the organ-ization.They decided whether to comply by asking, “According toofficial regulations and categories, am I supposed to assist this re-quester?” If the answer was yes, they felt a strong obligation togrant the request.

In sum, although all human societies seem to play by the sameset of influence rules, the weights assigned to the various rules candiffer across cultures. Persuasive appeals to audiences in distinctcultures need to take such differences into account. —R.B.C.

Surely, someone with your splendidintellect can see the unique benefits ofthis article. And because you look like ahelpful person who would want toshare such useful information, let memake a request. Would you buy this issue of the magazine for 10 of yourfriends? Well, if you can’t do that, wouldyou show it to just one friend? Wait,don’t answer yet. Because I genuinelylike you, I’m going to throw in—at abso-lutely no extra cost—a set of referencesthat you can consult to learn more aboutthis little-known topic.

Now, will you voice your commit-ment to help? ... Please recognize that Iam pausing politely here. But while I’mwaiting, I want you to feel totally as-sured that many others just like youwill certainly consent. And I love thatshirt you’re wearing. SA

Copyright 2001 Scientific American, Inc.