Contagious is about spreading information from person to person via word of mouth and social influence. To be talked about, shared, or imitated by consumers, coworkers, and constituents. In Contagious, Berger reveals the secret science behind word-of-mouth and social transmission. Discover how six basic principles drive all sorts of things to become contagious, from consumer products and policy initiatives to services and ideas within organizations.

Six key principles that cause things to be talked about, shared, and imitated.

Social Currency

Social Currency is about information senders and how sharing makes them look. Just as people use money to buy things they use social currency to achieve desired positive impressions among friends, families, and colleagues. People share things that will make them look good to others. when we share the social currency, we generates new devotees. The more remarkable something is, the more likely it will be discussed. In Social Currency the most interesting things are entertaining and reflect positively on the person who shares them. Its also emphasis the fact that virality isn’t born, that it’s made.

The Three Important Things That Complements Social Currency:

a. Find inner remarkability: – generate something unique, quirky, surprising, or novel. Think about ways to make your product or idea stand out by breaking from tradition and what people expect from an experience

b. Leverage game mechanics: use elements of a game to make something fun, interesting, and hook the consumer. “Good game mechanics keep people engaged, motivated, and always wanting more.

c. “Make people feel like insiders” – scarcity and exclusivity drives desirability… people love when they feel like “insider.


While social currency gets people to talk about things, “triggers” keep ideas and products fresh in the minds of consumers, ensuring that they keep talking about your idea. Cues in the environment not only boost word of mouth but also remind people about things they already wanted to buy or do. You may have meant to eat healthier or visit that new website your friend mentioned, but without a visible trigger to jog your memory, you’re more likely to forget.

Thus, “Triggers” are stimuli that connect thoughts and ideas together. By designing products and ideas that are linked to our surroundings, it helps to set off frequent “lightbulbs” or “triggers” in people’s mind. When people think about your product, they will likely talk about it, share their experience with it, and become repeat customers over time. In fact, more frequently trigger-associated products can increase word-of-mouth by 15 percent, and because it is top of mind, it generally means someone will be more likely to act on what they are thinking about.


Emotional content evokes feelings, both positive and negative, that drive people to share and act on those emotions. Tax hikes, price increases, new iPhone releases, elections and policy stances – all evoke positive and negative outbursts that drive people to talk about it with those around them. In many cases, it can drive activism in politics, switching from one product to another, or writing a Yelp review online to encourage people to eat or not eat at a certain cafe.

Awe on the other hand, is a complex emotion and frequently involves a sense of surprise, unexpectedness, or mystery. Indeed, as Albert Einstein himself noted, “The most beautiful emotion we can experience is the mysterious. It is the power of all true art and science. He to whom this emotion is a stranger, who can no longer pause to wonder and stand rapt in awe, is as good as dead.”

Berger explains that certain emotions evoke action while causing others to stifle:




Amusement (Humor)






Awe, excitement, humor evoke as much arousal as anger and anxiety, while contentment and sadness leave people to do nothing at all. Understanding arousal can help you drive viral content and products for yourself, by focusing less on information (features and benefits) around your product or idea, and focus on how people think, feel, and react to certain messages. In addition, Emotions drive people to action. They make us laugh, shout, and cry, and they make us talk, share, and buy. So rather than quoting statistics or providing information, we need to focus on feelings.

In summary, Some emotions kindle the fire more than others. As we discussed, activating emotion is the key to transmission. Physiological arousal or activation drives people to talk and share. We need to get people excited or make them laugh. We need to make them angry rather than sad. Even situations where people are active can make them more likely to pass things on to others.

Public: The Impact of Social Influence.

People often imitate those around them. They dress in the same styles as their friends, pick entrées preferred by other diners. People are more likely to vote if their spouse votes, more likely to quit smoking if their friends quit, and more likely to get fat if their friends become obese. If people can’t see what others are choosing and doing, they can’t imitate them. Thus, people tend to conform to what others are doing wheic is driven by social influence.

Social influence has a big effect on behavior, but to understand how to use it to help products and ideas catch on, we need to understand when its effects are strongest. For a more familiar example given by Berger, think about the last time you sat through a bewildering PowerPoint presentation. Something about equity diversification or supply chain reorganization. At the end of the talk, the speaker probably asked the audience if anyone had any questions. The response?


But not because everyone else understood the presentation. The others were probably just as bewildered as you were. But while they would have liked to raise their hands, they didn’t because each one is worried that he or she is the only person who didn’t understand. Why? Because no one else was asking questions. No one saw any public signal that others were confused so everyone keeps his doubts to him- or herself. Because according him, behavior is public and thoughts are private. Social influence was stronger when behavior was more observable. Thus, observability has a huge impact on whether products and ideas catch on.

Observability: The Need to Converting Private to Public

The more public a product or service is, the more it triggers people to take action. Observable things are also more likely to be discussed. Designing products that advertise themselves is a particularly powerful strategy to publicized any business. This can be done through large logos, giveaway something that be used publicly and social proof that sugget a good product which can make potential adopters feel comfortable about. like Hotmail and Apple we should design roducts that advertise themselves.

Practical Value

People like to pass along practical, useful information. News others can use. Further, like the stories of Ken’s corn and the vacuum-discussing hikers illustrate by the write, people don’t just value practical information, they share it. Offering practical value helps make things contagious. People share practically valuable information to help others. Whether by saving a friend time or ensuring a colleague saves a couple of money next time he goes to the supermarket, useful information helps. Yes, saving money is one of the benefits of Practical Value —getting something for less than its original price or getting more of something than you usually would for the same price. If we see an amazing deal we can’t help but talk about it or pass it on to someone we think would find it useful.

In this way, sharing practically valuable content is like a modern-day barn raising. Many people move away from their families for work or school, reducing face-to-face contact with our strongest social ties. Hired labor has taken the place of community barn raising. But sharing something useful with others is a quick and easy way to help them out. Even if we’re not in the same place.

The Major Difference Between Social Currency and Practical Value

Like we have ponted out earlier that Social Currency is about information senders and how sharing makes them look, Practical Value on the other hand, is mostly about the information receiver. It’s about saving people time or money, or helping them have good experiences. Sure, sharing useful things benefits the sharer as well. Helping others feels good. It even reflects positively on the sharer, providing a bit of Social Currency. But at its core, sharing practical value is about helping others. Also, The Emotions chapter noted that when we care, we share. But reverse is also the case in the practical value. Hence, sharing is caring.

It is also important to note that, of the six principles of contagiousness that was discussed in the book, Practical Value may be the easiest to apply. Why?

Some products and ideas already have lots of Social Currency, but to build it into a video for a blender takes some energy and creativity. Figuring out how to create Triggers also requires some effort, as does evoking emotion. But finding Practical Value isn’t hard. Almost every product or idea imaginable has something useful about it. Whether it saves people money, makes them happier, improves health, or saves them time, all of these things are news you can use. In Practical Value people share the story of how their neighbor’s dogs got sick after eating a certain type of chew toy because they want your dog to avoid the same fate.

Haven said that, the harder part is to remove all the things or information that is trivial. So we need to make our product or idea stand out, package our knowledge and expertise so that people learn about us while they pass it along. We also need to make it clear why our product or idea is so useful that people just have to spread the word.


Stories are an important source of cultural learning that help us make sense of the world. From The Iliad and The Odyssey writen by Homer, to Richard H. Wilkinson book The Complete Gods and Goddesses of Ancient Egypt, stories were the original form of entertainment. Then, there was no Internet, No SportsCenter or TV news. No radio or newspapers. So if you wanted entertainment, stories were the way to get it. The Trojan Horse, The Odyssey, and other famous tales were the entertainment of the day.

Narratives are inherently more engrossing than basic facts. They have a beginning, middle, and end. If people get involved, they’ll stay for the conclusion. When you hear people tell a good story you hang on every word. You want to know how it ends. Until it does, they’ve captured your attention. Today there are thousands of entertainment options, but our tendency to tell stories remains, because people tell stories for the same reasons they share word of mouth. People are so used to telling stories that they create narratives even when they don’t actually need to. Hence, stories carry things. A lesson or moral, Information or a take-home message.

Some Important Fact About Story Telling

Stories contain helpful information: a good route to take if the highway is blocked; a great dry cleaner if you need to get out tough stains, How should a good employee behave? What does it mean to be a moral person? Or on a more basic level, who’s a good mechanic who won’t overcharge? Stories, then, can act as vessels, carriers that help transmit information to others.

They provide a quick and easy way for people to acquire lots of knowledge in a vivid and engaging fashion.

Stories save time and hassle and give people the information they need in a way that’s easy to remember.

You can think of stories as providing proof by analogy. Stories thus give people an easy way to talk about products and ideas.

And good stories provide that reason. They provide a sort of psychological cover that allows people to talk about a product or idea without seeming like an advertisement.

Making Virality Valuable

Virality is the condition or fact of being rapidly spread or popularized by means of people communicating with each other, especially through the Internet. When trying to generate word of mouth, many people forget one important detail. They focus so much on getting people to talk that they ignore the part that really matters: what people are talking about. That’s the problem with creating content that is unrelated to the product or idea it is meant to promote. There’s a big difference between people talking about content and people talking about the company, organization, or person that created that content. For example, The Evian’s Roller Babies Campaign is considered the highest shared ads of all time with 55 million views, however they made little impact on sales.

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.