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Book Review: Influence: Science and Practice

Now in its fourth edition, this 262 page book shows readers six main ways people are influenced to say yes. Through the study of human psychology and dramatic examples, Robert Cialdini shows how humans sometimes use mental shortcuts to make decisions. "Influence practitioners" skilled at the art of persuasion can use these techniques to engage these shortcuts to influence our decisions. The book not only illustrates the six persuaders, but shows us ways to defend against these practices when the influencer may not have our best interests at heart.

influence book cover

The Psychology of Persuasion

An experimental social psychologist, Cialdini studied the psychology of compliance. At first he used experiments with students on campus. But Cialdini realized that to truly understand how persuasion works he needed to study how "compliance professionals" work in the wild. For nearly three years he immersed himself in the world of compliance, taking jobs with sales people, fund raisers, advertisers, waiters and the like to see persuasion in action. His goal was to find the main tactics used by these persuaders. Although there are thousands of different tactics that compliance practictioners used to get us to yes, Cialdini found six core influence principles. They are as follows:

What follows is a summary of the book with examples of the use of each persuasion technique. We also show how each technique can be used on the Web to persuade visitors to say yes.


Humans feel obligated to repay a gift from others. A basic norm of human culture, reciprocation requires that people try to repay, in kind, what another person has provided. This social lubricant ensures continuing relationships, which sociologists say is beneficial to society. In fact all human societies subscribe to this rule of future obligation. Reciprocation is a powerful force. It can overpower other rules such as liking.

Some Reciprocation Examples

The author gives a number of examples to illustrate reciprocation. People sent Christmas cards from strangers automatically send one back. Twice as many raffle tickets are sold after a small initial favor. The Hare Krishna Society gives flowers in exchange for donations. Waitresses find that giving candy with the bill increases tips. A $5 gift check with an insurance survey was twice as effective as a $50 reward for filling it out. LBJ was a master politician at moving bills through congress compared to Jimmy Carter, a relative outsider unaccustomed to favors.

Reciprocal Concessions

The author goes on to show the "contrast principle" where an intial higher offering is given. If rejected the persuader gives a concession for a smaller offering. The second offering appears smaller than it really is after hearing the higher offering. Cialdini even ties in the Watergate break-in as an example of a reciprocal concession. G. Gordon Liddy used the technique on Mitchell, Magruder, and Dean with an initial $1 million dollar plan, complete with call girls on a yacht, for CREEP to break into the Watergate offices of the Democratic National Committee. The plan was rejected as too costly. Next Liddy eliminated some features and dropped to a $500,000 plan. This too was rejected. Liddy then presented a $250,000 bare-bones plan (the amount he estimated it would take) which was accepted. Magruder said "We were reluctant to send him away with nothing." (Cialdini 2001)

Reciprocation and the Web

You can use reciprocation on the Web by giving away things. A free white paper is often exchanged for an email address. A limited time software sample is often given away so customers can try products out for 30 days. Free tools are a popular way to generate good will on the Web. WSO is no exception with our free web page analyzer service. We've received business as a result of offering this free service, with conversations starting out "I used your free tool so much I thought I'd call for some more information about your services." You can give out a tidbit of free advice on the phone with a prospect. Some companies offer free evaluations in the hopes of future business. The reject and retreat method of reciprocal concessions can be used by salespeople who start with their more costly offerings and retreat to lower offerings if rejected.

Commitment and Consistency

People want to be and look consistent with their words, beliefs, and attitudes. Once we commit to something we want to appear consistent after making the decision. These societal pressures cause us to behave in ways that justify our earlier decision. The key to getting people to comply is commitment. Getting that initial commitment (taking a stand on an issue for example) makes us more likely to agree to requests that are in line with that prior commitment. Personal consistency is highly valued in society. Inconsistent people are viewed as confused and erratic. Being automatically consistent saves us from thinking and spending time dealing with the complexities of everyday life. But there is risk in blind consistency.

Examples of Commitment and Consistency

The author gives a few examples of commitment and consistency at work. After placing bets at the racetrack, bettors were found to be more confident in their horses, even though the horses were the same as they were before the bets were placed. The simple addition of "watch my things" caused beach subjects to go from 4 of 20 to intervene with a thief to 19 of 20 who intervened. Toy manufacturers boost post-Christmas sales with hot item PR and artificially limited supply to bait and switch committed parents. They end up buying two toys, the replacement for the holidays, and the item they promised their kids in January or February (Furby, Cabbage Patch Kids, Nintendo, etc.). A call by social psychologist Steven Sherman asking Indiana residents as part of survey he was taking to predict what they would say if asked to spend three hours collecting money for the American Cancer Society. Not wanting to seem uncharitable, many people said they'd volunteer. A few days later, when the ACS called, they experienced a 700% increase in volunteers after this subtle initial committment. The Chinese used incremental committments to persuade Korean war POWs to denounce the USA and praise communism.

Start Small, Go Big

A general strategy with charitable organizations and the like is to start with small orders or donations, and gradually escalate towards larger orders. This "foot in the door" technique works off that initial commitment to compel people to be consistent in buying larger orders.

Put it in Writing, Ideally in Public

Getting people to commit to something in writing is a powerful technique. Especially if they pledge publicly to do something, they feel obligated to follow through and be consistent in their previous stand. That is why some organizations ask for signatures in door-to-door campaigns. Once committed to your stand on the environment, a subsequent visit asking for donations is bound to be more successful.

Committment and Consistency on the Web

You can use these techniques in your website and with your sales force. You can get prospects to commit in a small way by giving their contact information in exchange for a whitepaper or a free consultation (ties in with reciprocation). In your web copy you can ask easy to agree questions like "You want an easy to use website, right?" Subsequent requests for usability services or a paid PDF how-to will be looked on more favorably. Once you get the prospect on the phone salemen can use the technique of "little yesses" to move the commitment process along.

Social Proof

One method humans use to determine what is correct is by figuring out what other people think is corrrect. So we look at what other people are doing or believing and follow along. Social proof can simulate compliance with a request by telling the person that many other people have been complying. The author himself uses the principle of social proof on the cover of his book, "Over One Million Copies Sold!" After all, one million people can't be wrong. Social proof is another kind of mental shortcut to save effort. We "make fewer mistakes by acting in accord with social evidence than by acting contrary to it."

Two Conditions for Improved Social Proof

The principle of social proof works best under two conditions, uncertainty and similarity. When people are unsure, when things are ambiguous, they tend to follow the actions of others and accept them as correct. People are also more likely to follow the crowd if the people are similar to themselves.

Examples of Social Proof

The author gives a number of examples of social proof in action. Bartenders salt tip jars with dollar bills to make it look like others have already tipped. Church ushers salt collection baskets for the same reason. Advertisers trumpet best selling status, fastest growing, or "millions sold." Television producers use "canned laughter" to kick-start the audience. Nightclub owners deliberately create long lines outside when there is plenty of room inside. Psychologists use "densensitization" films where kids play with dogs or other kids to reduce anxiety for children that are afraid of dogs or interacting with other kids. Theater owners use "claquing," first used in 1820, where people were paid to applaud, yell "oncore," and exhibit wild enthusiasm (for a "special sum to be arranged"). The author says that the practice survives to this day.

Crowds and Cults

When there is uncertainty, you are better off asking one person directly for help, not a large crowd. That person will feel responsible for your safety. The crowd tends to follow along with what everybody else is doing. A highly publicized, front-page suicide produces a dramatic increase in the number of suicides, airplane, and motor vehicle fatalities immediately following the story. A bank run in Singapore was caused by a long line at a bus stop that happened to be in front of the bank. The most spectacular example of mass compliance was the mass suicide at Jonestown, Guyana. Jim Jones utilized a number of compliance techniques to get followers to drink the poison koolaid. The author gives an example of race track shenanigans where bettors would place early bets on a long-shot to shift the tode board odds, and place bets on the true favorite with better odds.

Social Proof and the Web

You can use social proof to your advantage to raise perceived credibility on the Web. Showing long lists of impressive clients is one technique of social proof. Badges of approval from the Better Business Bureau, Hacker Safe, and the like boost perceived credibility. Showing a large number of people who visit your site, or buy your products or services works to influence by following the crowd. Amazon's "Customers Who Bought This Item Also Bought" is a form of social proof. A large number of testimonials can have the same effect.


Most people prefer to say yes to people that they know and like. We are more likely to comply when a product or service is associated with physically attractive people, positive circumstances or attributes, and people that are similar to us. Recommendations from a friend or someone we know has much more weight than a cold call from a stranger.

Factors that Influence Liking

The five factors that influence liking are physical attractiveness, similarity, repeated contact, positive circumstances, and association. Advertisers connect their products with positive things or famous people that may not have anything to do with their product. People assume that physically attractive people have other positive characteristics, such as talent, honesty, and intelligence. In Canada attractive candidates received more than two and half times as many votes as unattractive candidates. Attractive individuals get hired more and make and average of 12 to 14% more than their unattractive coworkers. Attractive people are more likely to receive favorable treatment in the legal system. Good looking people are perceived to be more likable, more persuasive, and more intelligent. Advertisers use this "halo effect" with pretty models selling cars and other items.

We also like people who are similar to us. That is why salespeople are quick to point out any similar backgrounds or interests to ours. The evidence shows that these techniques work. Customers are more likely to buy insurance when the salesman was like them. Mailed surveys were more likely to be completed when the name of the survey-taker was modified to be similar to the recipient's name.

Examples of Liking in Action

Tupperware parties are the classic example of the power of liking. Tupperware parties use a number of compliance techniques including reciprocity (everyone receives a gift), commitment (public descriptions of uses and benefits of Tupperware), social proof (group buying), and liking (requests to purchase come from a friend, not a stranger). The hostess gets a percentage of the take as well. The strength of the social bond is twice as likely to influence a purchase decision than preference for the product itself. Just mentioning a friend's name is enough to invoke the liking rule. So and so "suggested that I call you" makes you more likely to comply. Joe Girard, a car salesman in Detroit, made over $200,000 a year and averaged more than five cars and trucks sold every day by using referrals and a list of 13,000 previous customers who received seasonal cards with the words "I like you." The simple act of saying "I like you" or paying a compliment will increase the likelihood of compliance with a request.

Conditioning and Association

You've no doubt heard the phrase "Don't shoot the messenger." People associate the messenger with bad or good news. Weather people have been physically abused after a poor weather forecast. Imperial messengers in old Persia hoped for battlefield success. With news of victory, they were treated as a hero with food, drink, and women of their choice. Upon receipt of a military defeat, they were summarily slain. Advertisers often use celebrities to pitch their products or services. Michael Jordan may not wear Hanes underwear, but his endorsement associates his positive attributes with the product. After seeing a new car ad with a seductive female, men rated the car as faster, more appealing, more expensive-looking, and better designed than men who viewed the same as without the model. A study of credit card use showed that students were much more likely to spend and donate when they examined items with MasterCard insignias in the room (87 percent versus 33 percent). Advertisers are willing to spend many millions to associate their products with the Olympics, the Super Bowl, and other cultural phenomena.

Liking and the Web

The wording you use on your web site can significantly affect your conversion rates. Sophisticated developers create "personas," or paths that are crafted for different types of potential customers. Each path has copy tailored for their level of education and different personality characteristics. By writing your wording in a friendly, benefit-oriented style you can kick-start the liking process. Using endorsements, pictures of attractive people pitching your product, or even how you answer your phone can lubricate the liking process. Stories or testimonials from satisfied clients can act as recommendations. You can institute a referral program where clients refer colleagues to you for a fee or discount on future services. Amazon is a master at using the referral process to sell books. The design of your site is a form of attractiveness that can work to your advantage. B. J. Fogg found that we based 46% of perceived credibility on a "clean, professional look" for websites.


There are strong societal pressures to comply with the requests from an authority. Systematic societal pressures have instilled in us that deference to authority is correct conduct. Obeying genuine authories, who possess wisdom, knowledge, and power is a decision-making mental shortcut.

Factors that Influence Authority

Some symbols of authority are effective in automatic compliance with requests. Impressive titles, clothing, and automobiles have been shown to create more deference or obedience to those that possess one or more of these symbols. Size and status are related. Titled people are seen as taller, rival animals puff themselves up to appear larger. Con men and women wear lifts to appear taller. Pedestrians asked to give a stranger a dime were twice as likely to comply when the requester wore a uniform. Business-suited jaywalkers are three and one-half times more likely to be followed than jaywalkers who wore street clothes. Nearly all drivers waiting behind an economy car honked their horns and some rammed their bumpers but 50 percent of motorists waited patiently behind a luxury model. One technique used to enhance the effectiveness of authority is to mention a small shortcoming in their position or product that is easily overcome by advantages.

Examples of Authority in Action

In an experiment by Milgram, a "Teacher" was asked to deliver electric shocks to "Learners" that incorrectly answered questions. Even after the voltage increased from 75 volts to 450 volts, and despite the screaming protests of the Learners, Teachers continued to administer the electric shocks due to the lab-coated authority figure. The shocks and effects were simulated by actors, but the Teachers were not aware of this. A protester of arms shipments to Nicaragua laid across the railroad tracks delivering the goods, had both legs severed below the knee when the train did not stop, even with plenty of warning. The civilian crew was given orders to never stop of slow down. Deference to doctors in hospitals contributes to a 12 percent daily error rate for patient medication alone. Robert Young, aka Marcus Welby, M.D., was hired to pitch the health benefits of caffeine-free Sanka coffee. Sanka sales soared.

A top waiter used the shortcoming technique to boost orders and consequently tips for larger groups of diners. Taking the initial order, usually from a woman, the waiter would pause, look over his shoulder for his boss, and mention that the dish "wasn't as good tonight as it usually is," and suggest two other menu items that were slightly less expensive. Diners felt grateful that the waiter had done them a favor. The waiter received higher tips, as diners were more inclined to order wine or dessert from this authority figure.

Authority and the Web

You can trumpet the titles and education of your staff on your web site. If your staff has written books, articles, conducted studies, or received impressive press be sure to mention this. Including testimonials from high-ranking staff of top companies can help. Including images of uniformed people in your site can add symbols of authority to web sites. A pretty lab-coated doctor would be a good addition to a Canadian pharmacy selling drugs to the US.


People want to possess what they cannot have. People assign higher value to an opportunity when it is less available. If it is becoming rare it is therefore more valuable. The mental shortcut is if things are more difficult to possess, they are typically better than things that are easier to possess. So we use an item's availability as a quick proxy for its quality. One other aspect of the scarcity principle is that we hate to lose the freedoms we already have. This desire to maintain our options is called psychological reactance. "According to the theory, whenever free choice is limited or threatened, the need to retain our freedoms makes us desire them (as well as the goods and services associated with them) significantly more than previously." (Cialdini 2007). So we react against any restrictions on the prior access of an item, desiring it more than before.

Factors that Influence the Scarcity Principle

We are more likely to desire an opportunity when it is newly scarce. When an item just goes on sale for example. We are most attracted to scarce items when we have to compete with others for them. The author gives an example of a used car sale where multiple people show up at once competing for the same car.

Examples of the Scarcity Principle

Two-year-olds (and teenagers) express their growing autonomy by invariably doing the opposite that their parents wish. In one study, two-year-old boys were placed in a room with their mothers with two attractive toys. They tested two different size plexiglass barriers placed in front of one of the toys. When the barrier was one foot tall the boys showed no preference for either toy. But when the barrier was two feet tall, they touched the less accessible toy three times faster than the attainable toy. Shakespeare's Romeo and Juliet illustrates how parental interference can backfire. The young couple rebelled against the restrictions, and expressed the ultimate assertion of free will by committing suicide together. A study of 140 Colorado couples found that parental interference made the pairs feel greater love and desire for marraige. When the interference weakened, so did their feelings for each other.

Salesmen use the scarcity principle when selling products. Car salesmen say this is the only model of this car in the tri-state area. "This is an exclusive, limited time offer!" Appliance salesmen see a couple interested in a washer, and say I see you are interested in this model. Unfortunately they say another couple just bought the item, but miraculously come up with an identical washer when the couple says they want to buy at the quoted price if they have another. Scarce information is perceived to be more valuable than freely available information. In a test of the scarce information principle, beef buyers were called asking for a purchase in one of three ways. One set of customers got the standard pitch. Another got the same pitch with the information that beef would be scarce in the coming months. The third set of customers were told what the second set were told, and that the information was hard to come by, from exclusive contacts the company had. The second group bought twice as much beef. The third bought six times as much beef as the first group.

Coin collectors covet the 1955 double die penny for this rare mistake. Stamp collectors look for that inverted Jenny biplane. Basedball card collectors cherish the Honus Wagner card, which was distributed in cigarette packs, which Honus objected to, limiting the run. Deadlines, artificial or not (one time only, 24 hours, one visit only) cause us to make snap decisions to avoid having our freedoms restricted and possess the difficult to attain.

Scarcity and the Web

You can use the scarcity principle to sell more products and services on the Web. When travelers go to Orbitz.com to buy airline tickets, they are often told that there are only X available seats left at that price. Amazon shows the number of books left before a new order must be placed (with attendant delays if you don't act now). Amazon also calculates the time before you have to order to receive it by a certain date. You can put limits on the amount of products or services you sell to enable the scarcity principle. Photographers create limited run prints. Service companies will only take on a few more clients due to demand (social proof in action as well). You can use perceived scarcity of information to build a following on the Web. Matt Cutts' blog about working inside Google is seen as scarce information, therefore valuable.


Influence shows us how six core techniques are used to persuade people to comply with requests. Cialdini shows how we take mental shortcuts to quickly arrive at decisions to save time and effort. By tapping into these "click, whirr" behaviors, people can use these techniques to persuade people to say yes. There are two books out titled "Influence" by Cialdini, "Influence: The Psychology of Persuasion" and "Influence: Science and Practice." Even though the first is newer than the second, I recommend the second book as it has more meat in it, including summaries, questions for students, letters from readers, and more. The first book is more of a layman's version of the second. Both books have the much of the same information and stories. Highly recommended.

Further Reading

Influence at Work
Cialdini's web site for more information on the psychology of persuasion.
Cialdini, R. B., "Influence: The Psychology of Persuasion," revised edition
(New York: Collins Business Essentials, 2007), 245. They layman's version of his persuasion book.
Cialdini, R. B., "Influence: Science and Practice," 4th ed.,
(Needham Heights, MA: Allyn and Bacon, 2001). A more scholarly version of the book with cites, chapter summaries, and questions and answers for students.

About the Author

Andy King is the founder of five developer-related sites, and the author of Speed Up Your Site: Web Site Optimization (http://www.speedupyoursite.com) from New Riders Publishing. He publishes the monthly Bandwidth Report, the semi-weekly Optimization Week, and Speed Tweak of the Week.