Contagious: How to Build Word of Mouth in the Digital Age

by Jonah Berger

It starts when a guy enters “study abroad Paris France” and clicks on one of the top search results to learn more. Later he searches for “cafés near the Louvre,” and scans to find one he thinks he’ll like. You hear a female laugh in the background as his next entry is “translate tu es très mignon,” which he soon learns is French for “you are very cute.” Quickly he then seeks advice on how to “impress a French girl,” reads up on the suggestions, and searches for chocolate shops in Paris.

“The best results don’t show up in a search engine, they show up in people’s lives.”

Take online search. Why is search important? Because people want to find information quickly. Why do they want to do that? So they can get answers to what they are looking for. Why do they want those answers? So they can connect with people, achieve their goals, and fulfill their dreams. Now that’s starting to get more emotional.

Want people to talk about global warming and rally to change it? Don’t just point out how big the problem is or list key statistics. Figure out how to make them care. Talk about polar bears dying or how their children’s health will be affected.

When trying to use emotions to drive sharing, remember to pick ones that kindle the fire: select high-arousal emotions that drive people to action.

And it did. Among students who had been instructed to jog, 75 percent shared the article—more than twice as many as the students who had been in the “relaxed” group.

Ad timing also matters. Although a show may be generally arousing, a specific scene in that show may be more activating than others. In crime shows, for example, the anxiety often peaks somewhere in the middle. When the crime is solved at the end, all tension dissipates. In game shows, excitement—and therefore arousal—is highest when contestants are about to find out how much they’ve won. We may end up talking more about ads that show up close to these exciting moments.

Whether it’s a digital product, like Google, or a physical product, like sneakers, you should make something that will move people. People don’t want to feel like they’re being told something—they want to be entertained, they want to be moved.

Ever notice the slow delay when you first pull the cover off the box of your new iPhone? That’s because Apple has been hard at work designing that experience to provide the perfect feeling of luxury and heft.

Observability. Jobs realized that seeing others do something makes people more likely to do it themselves.

If it’s hard to see what others are doing, it’s hard to imitate it. Making something more observable makes it easier to imitate. Thus a key factor in driving products to catch on is public visibility. If something is built to show, it’s built to grow.

Currently more than 100,000 patients are on the wait list; more than 4,000 new patients are added each month.

97.1 percent of kidney offers are refused.

More than three-quarters of American college students under the legal drinking age report drinking alcohol. But the bigger concern was the quantity that students consume. Forty-four percent of students binge-drink, and more than 1,800 U.S. college students die every year from alcohol-related injuries. Another 600,000 are injured while under the influence of alcohol.

My colleagues Blake McShane, Eric Bradlow, and I tested this idea using data on 1.5 million car sales. Would a neighbor buying a new car be enough to get you to buy a new one? Sure enough, we found a pretty impressive effect. People who lived in, say, Denver, were more likely to buy a new car if other Denverites had bought new cars recently. And the effect was pretty big. Approximately one

Public visibility boosts word of mouth. The easier something is to see, the more people talk about it. Observability also spurs purchase and action.

It all started one Sunday afternoon in 2003. A group of friends from Melbourne, Australia, were sitting around drinking beers. The conversation meandered in various directions and finally ended up on 1970s and 80s fashion. “What ever happened to the moustache?” one guy asked. A few beers more and they came up with a challenge: to see who could grow the best moustache. The word spread to their other friends, and eventually they had a small group of thirty people. All grew moustaches for the thirty days of November.

out how to make the private public. They figured out how to take support for an abstract cause—something not typically observable—and make it something that everyone can see.

Koreen Johannessen was able to reduce Arizona students’ drinking by making the private public. She created ads in the school newspaper that merely stated the true norm. That most students had only one or two drinks, and 69 percent have four or fewer drinks, when they party. She didn’t focus on the health consequences of drinking, she focused on social information. By showing students that the majority of their peers weren’t bingeing, she helped them realize that others felt the same way. That most students didn’t want to binge. This corrected the false inferences students had made about others’ behavior and led them to reduce their own drinking as a result. By making the private public, Johannessen was able to decrease heavy drinking by almost 30 percent.

One way to make things more public is to design ideas that advertise themselves.

Take Apple’s decision to make iPod headphones white. When Apple first introduced the iPod, there was lots of competition in the digital music player space. Diamond Multimedia, Creative, Compaq, and Archos all offered players, and music on one company’s device couldn’t easily be transferred to another. Further, it wasn’t clear which, if any, of these competing standards would stick around, and whether it was worth switching from a portable CD player or Walkman to buy this new, expensive device. But because most devices came with black headphones, Apple’s white headphone cords stood out.

Behavioral residue is the physical traces or remnants that most actions or behaviors leave in their wake.

Clothing retailer Lululemon takes this idea one step further. Rather than make paper bags that are relatively durable, it makes shopping bags that are hard to throw away. Made of sturdy plastic like reusable grocery bags, these bags are clearly meant to be reused.

ABC News found that installing these buttons boosted its Facebook traffic by 250 percent.

But anti-drug ads often say two things simultaneously. They say that drugs are bad, but they also say that other people are doing them.

Our basic hypothesis is that the more kids saw these ads, the more they came to believe that lots of other kids were using marijuana. And the more they came to believe that other kids were using marijuana, the more they became interested in using it themselves.

If you want to get people not to do something, don’t tell them that lots of their peers are doing it.

“many past visitors have removed petrified wood from the Park, changing the natural state of the Petrified Forest.” But by providing social proof that others were stealing, the message had a perverse effect, almost doubling the number of people taking wood!

It’s been said that when people are free to do as they please, they usually imitate one another. We look to others for information about what is right or good to do in a given situation, and this social proof shapes everything from the products we buy to the candidates we vote for.

The way people actually make decisions often violates standard economic assumptions about how they should make decisions. Judgments and decisions are not always rational or optimal.

One of the main tenets of prospect theory is that people don’t evaluate things in absolute terms. They evaluate them relative to a comparison standard, or “reference point.”

Diminishing sensitivity reflects the idea that the same change has a smaller impact the farther it is from the reference point.

The same change—gaining ten more dollars—has a smaller and smaller impact the farther you move from your reference point of zero dollars or not winning anything.

As prospect theory illustrates, one key factor in highlighting incredible value is what people expect. Promotional offers that seem surprising or surpass expectations are more likely to be shared.

Researchers find that whether a discount seems larger as money or percentage off depends on the original price. For low-priced products, like books or groceries, price reductions seem more significant when they are framed in percentage terms. Twenty percent off that $25 shirt seems like a better deal than $5 off.

If the product’s price is less than $100, the Rule of 100 says that percentage discounts will seem larger.

Useful information, then, is another form of practical value. Helping people do things they want to do, or encouraging them to do things they should do.

It sends out a short, one-page note, with a key header article and three or four main links below it. It’s easy to see what the main points are, and if you want to find out more, you can simply click on the links.

The problem with this assumption, though, is that just because people can share with more people doesn’t mean they will. In fact, narrower content may actually be more likely to be shared because it reminds people of a specific friend or family member and makes them feel compelled to pass it along.

because so many people are interested in that type of thing, no one person strongly comes to mind when you come across related content.

People are also less likely to argue against stories than against advertising claims.

First, it’s hard to disagree with a specific thing that happened to a specific person.

Second, we’re so caught up in the drama of what happened to so-and-so that we don’t have the cognitive resources to disagree. We’re so engaged in following the narrative that we don’t have the energy to question what is being said.

Information travels under the guise of what seems like idle chatter.

Only 2 percent of women describe themselves as beautiful. More than two-thirds believe that the media has set an unrealistic standard of beauty that they’ll never be able to achieve.

And “Evolution,” which cost only a little over one hundred thousand dollars to make, got more than 16 million views. It netted the company hundreds of millions of dollars in exposure. The clip won numerous industry awards and more than tripled the website traffic the company received from Dove’s 2006 Super Bowl ad. Dove experienced double-digit sales growth.

There’s a big difference between people talking about content and people talking about the company, organization, or person that created that content.

The key, then, is to not only make something viral, but also make it valuable to the sponsoring company or organization. Not just virality but valuable virality.

Virality is most valuable when the brand or product benefit is integral to the story. When it’s woven so deeply into the narrative that people can’t tell the story without mentioning it.

Social Currency Does talking about your product or idea make people look good? Can you find the inner remarkability? Leverage game mechanics? Make people feel like insiders? Triggers Consider the context. What cues make people think about your product or idea? How can you grow the habitat and make it come to mind more often? Emotion Focus on feelings. Does talking about your product or idea generate emotion? How can you kindle the fire? Public Does your product or idea advertise itself? Can people see when others are using it? If not, how can you make the private public? Can you create behavioral residue that sticks around even after people use it? Practical Value Does talking about your product or idea help people help others? How can you highlight incredible value, packaging your knowledge and expertise into useful information others will want to disseminate? Stories What is your Trojan Horse? Is your product or idea embedded in a broader narrative that people want to share? Is the story not only viral, but also valuable?