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Contagious by Jonah Berger.
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In Contagious, marketing expert Jonah Berger argues that the driving force behind products and ideas catching on—or, in his words, becoming “contagious”—is word of mouth. For something to be popular, he says, it (or its marketing) has to be interesting enough to get people talking. He then explains how to harness word of mouth to make something popular—whether it’s a product, a work of art, an article, or even just an idea.

(Shortform note: In Contagious, Berger describes the book (and the way it defines word of mouth) as a rebuttal to Malcolm Gladwell’s The Tipping Point. In The Tipping Point, Gladwell argues that a few socially influential people are responsible for most word of mouth—and are therefore responsible for things catching on. He then explains that catering specifically to those influential people will make your product or idea popular. On the other hand, Berger suggests that word of mouth consists of thousands of small-scale conversations between everyday people. As you read through the guide, consider how Berger’s principles focus on these individual conversations—and how they refute Gladwell’s theory of a few particularly influential individuals.)

In Part One of our guide, we’ll explore Berger’s arguments for why word of mouth is the primary source of popularity. In Part Two, we’ll explore his principles for generating word of mouth, which we’ve organized into three steps:

  1. Attract your audience
  2. Engage your audience
  3. Benefit your audience

Through our commentary, we’ll bring in psychological research and alternative perspectives that add nuance and contrast to Berger’s strategies. In addition, we’ll provide real-world examples of Berger’s principles and practical advice on how to adapt them to your product or idea.

Part 1: The Source of Popularity

Berger begins by discussing what causes massive, viral popularity—of ideas, articles, internet videos, products, and everything else. His argument has two main points:

  1. Conventional wisdom suggests three main causes of popularity—factors that don’t fully explain what makes things popular.
  2. Popularity comes from word of mouth.

Conventional Wisdom

To start off, Berger discusses conventional wisdom on what makes a product popular. He suggests that people usually point to three main factors: low price, high quality, and lots of advertising. However, Berger argues that while these factors can contribute to popularity, they aren’t the defining factor of popularity—in other words, they don’t make a product popular by themselves.

(Shortform note: The conventional marketing wisdom Berger discusses typically takes the form of “mass-marketing strategies”: marketing that tries to reach as many people as possible. To sell to as many people as possible, mass-marketed products have low prices. Then, mass marketing uses lots of ads touting the quality of a product to try and reach large audiences. However, companies have shifted away from mass-marketing strategies in the past few decades—supporting Berger’s claim that conventional wisdom doesn’t explain the true cause of popularity.)

Word of Mouth and Popularity

The true source of popularity is word of mouth, according to Berger. Word of mouth consists of conversations, recommendations, and gossip between people. This personal communication is uniquely effective at creating popularity because it’s frequent, trustworthy, and targeted. Let’s look at how these three qualities contribute to popularity:

1) Frequency: People chat with each other all the time, Berger notes. This means that if a person wants or thinks about a product, they’ll mention it frequently to many different people—and if those people are also interested, they’ll do the same. This allows ideas to spread exponentially.

2) Trustworthiness: According to Berger, people are more likely to trust those they know than they are to believe any kind of advertising. Advertising, by definition, presents an ideal version of a product—people know this, so they don’t trust what they see in ads. On the other hand, friends, family, and coworkers are much more likely to give honest opinions. This means that people will value word of mouth more than advertising when they consider buying a product.

3) Targeted: Berger argues that word of mouth automatically targets an interested audience. Interested people are more likely to buy and talk about a product, contributing to its popularity. Additionally, people tend to recommend or mention products to people they think would like them. Then, if those people do like it, they’ll be more likely to pass it along to other interested people. This also contributes to a product’s exponential growth in popularity.

Influencer Marketing, Word of Mouth, and Popularity

While Berger discusses word of mouth in the context of many one-on-one conversations, some advertisers try to create frequent, trustworthy, and targeted ads through influencers—people who promote products to their large (usually online) followings. Here are their arguments for how influencers replicate the benefits of word of mouth:

1) Frequent: To gain and maintain a large online following, influencers create online content frequently, often posting once a day or more. This means an influencer partnered with your product will mention it frequently.

2) Trustworthy: Influencers typically position themselves as authority figures on a particular topic, so audiences are more likely to believe their opinions on products. For example: An influencer that creates makeup tutorials...

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Contagious Summary Introduction

Every day, people introduce countless new ideas to the world—for example, new products, new political policies, and new businesses. Many of these ideas get lost in the crowd and never really “catch on.” Businesses fail, new behavioral ideas fail to take root, and new content is ignored.

However, some ideas sweep across society and become the next “big thing.” They become contagious. Suddenly, everyone wants to buy the latest new product, visit the trendy new gym in their area, or read the latest viral article. This process of ideas catching on is called a “social epidemic.”

Why is it that some new products and ideas gain widespread popularity while others fail to “catch on”? Research has provided three simplistic explanations at to why certain things become so popular:

  1. They’re of a higher quality than competing products or ideas and are therefore more attractive to consumers. For example, a website that’s much more user-friendly than its competitors is going to be more popular.
  2. They’re cheap or on sale. People love to save money.
  3. They’ve been advertised a lot. The more a product or idea is promoted, the more people will hear about it, and the more popular it...

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Contagious Summary Chapter 1: Give People Social Currency

The first attribute of contagious ideas and products is that they give people social currency. The theory of social currency is based on the idea that everything you talk about affects how people see you and impacts your level of social influence. For example, if you only talk about boring things, people will think you’re boring. They won’t want to talk to you anymore, meaning your social influence will decrease. However, if you talk about interesting, witty, or unusual things, people will think you’re fun to be around. They’ll want to spend time with you, and your social influence will increase.

Because what people say has such a big impact on their public image, they’re inclined to choose their topics of conversation carefully. They’re only willing to talk about things that they think will add to their social currency, not deplete it. For this reason, if you want information about your product or idea to disseminate through word of mouth, make sure that discussing it gives people social currency rather than taking it away.

You can make your product or idea a source of social currency by implementing three principles:

  1. Make it remarkable.
  2. Apply game...

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Shortform Exercise: Generate Social Currency

Learn how to make a product a source of social currency.

Think of a time you tried to tell someone about a product—either a product you’re marketing yourself, or a product you’ve used—but they seemed uninterested in what you were saying. What was the product? Why do you think your discussion of it fell flat?

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Contagious Summary Chapter 2: Create Effective Triggers

The second attribute of contagious products and ideas is that their marketing strategy contains triggers. A trigger is a stimulus that reminds you of something else. For example, smelling food as you walk down the street might remind you that you need to grab some lunch. Seeing a book that a loved one likes will remind you of that person.

If you can link your product or idea to a trigger, you can ensure that people think about it whenever they encounter that trigger. For instance, say you‘re launching a new type of ice cream. In the marketing for your product, you decide to strongly associate eating the ice cream with sunny weather. From now on, whenever it’s sunny, people will be triggered to think about your product.

Triggering people to think about your product helps to generate word of mouth because people tend to talk about whatever’s on their mind in a given moment. Therefore, if your product or idea is the thing on someone’s mind, it’ll become the thing they choose to talk about.

This is especially true when people are making small talk—for instance, when parents are talking on the sideline of their kids’ soccer game, or when colleagues chat on their lunch...

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Shortform Exercise: Create an Effective Trigger

Learn how to create an effective trigger for your product or idea.

Think of a product you’ve created (or one that you enjoy using). Brainstorm five to ten possible triggers for this product. (Try to make sure that these triggers haven’t been used by other companies before. Likewise, try to make them relevant to your target audience’s local environment.)

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Contagious Summary Chapter 3: Generate an Emotional Response

The third attribute of contagious products and ideas is that they generate an emotional response. When people experience strong emotions, they often like to talk to others about how they’re feeling. For instance, someone who’s had a bad day at work will want to go home and vent their anger to their family. Someone who’s just gotten promoted will want to share their excitement with their loved ones.

When people do this, they inevitably share all the details about what made them so emotional in the first place. So, if you can make your product or idea generate an emotional response in people, it may get them talking not only about their feelings but also about your product or idea itself.

Which Emotions Should You Generate?

An important caveat to this principle is that not all emotions are equally effective at getting people to discuss your product or idea. Berger’s research found that only emotions that generate high amounts of physiological arousal push people to talk about how they’re feeling.

Physiological arousal is, in simple terms, your body being “activated”—being readied for action. Signs of physiological arousal include a racing heart, tensed muscles,...

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Shortform Exercise: Generate an Emotional Response

Learn how to get people talking about a product or idea by making them feel a high-arousal emotion.

Think of a product or idea that you’ve created or that you support. Describe this product or idea.

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Contagious Summary Chapter 4: Create Public Visibility

The fourth attribute of viral products or ideas is that they’re publicly visible. Ultimately, people are never going to talk about your product or idea if they never see it in the first place. So, to generate as much word of mouth about your product or idea as possible, make it very easy to observe. People need to see it often—or, if that’s not possible, it needs to be striking enough that once they’ve observed it once, they remember it for a long time.

If people see your product or idea a lot, they’re likely to start thinking about it a lot, too. For instance, they might start to contemplate why it’s so popular. This drives word of mouth because, as you learned in Chapter 2, people tend to talk about the things they’re thinking about.

How to Make Things Visible

There are two possible ways to increase the visibility of your product or idea. These are making the private public and making your product advertise itself.

Making the Private Public

Making the private public means finding a way to make it publicly clear that people use your product or support your idea, even when this information would usually be private.

Some purchasing decisions are...

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Shortform Exercise: Make Your Product Visible

Learn how to add visibility to your product or service.

Think of a product or service you’re selling (or would like to sell). How publicly visible do you consider this product or service to be? (For instance, is it easy for people to observe your customers using the product or service? Do people only tend to buy or use it in private?)

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Contagious Summary Chapter 5: Provide Practical Value

The fifth attribute of contagious products or ideas is that they provide practical value—they’re useful in some way. People love gathering practical information that will make their lives easier. Most commonly, they like to collect information that will help them to complete tasks more quickly and easily, or information that will help them to save money.

Crucially, people also love sharing this information with other people. They do so because they want to help the people they care about. Therefore, if you make your product or service a source of practical value, people will talk about it because they’ll want to share its value with others. In short, you’ll generate word of mouth.

There are two ways to add practical value to your product or idea:

  1. Create an amazing discount and apply it to your product. This will capitalize on people’s love of sharing money-saving tips.
  2. Provide useful information to your customers once they’ve bought your product. For example, give them practical advice on a topic relevant to your product or service. Do so in an easy-to-share format like an email or a magazine so your customers can pass this information on to their loved...

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Shortform Exercise: Create an Amazing Discount

One of the ways to give your product or service practical value is to create and apply an amazing discount. In this exercise, learn how to ensure that your discount is amazing.

Think of a product that you’ve created (or want to create). What price would you usually sell this product for? If you were asked to devise a discount for this product, what saving would you consider applying?

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Contagious Summary Chapter 6: Tell People a Story

The final attribute of contagious products or ideas is that their marketing materials tell people a story. Information about the product or idea is subtly woven into a gripping narrative that grabs people’s attention. For example, you could embed factual information about your product into a heartwarming story about how using it changed someone’s life. If your story is interesting or exciting enough, people will retell it to their friends and family—and they’ll pass on information about your product or idea in the process.

People pass on interesting stories about products or ideas for two reasons. First, they know that telling someone an interesting story will give them social currency—that telling it will make them seem interesting, too.

Second, sharing a story about a product or idea is much more socially acceptable than simply spouting facts about it. If you approached someone and, totally out of context, started listing the specifications and functions of a product that you really liked, the other person would find you boring at best and strange at worst. Whatever the case, you’re going to lose social currency. Meanwhile, embedding these specifications and...

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Shortform Exercise: Tell a Shareable Story

Learn how to market a product by telling a shareable story.

Think of a product that you’ve created (or want to create). How and why did you first decide to create this product? Outline its “origin story” below.

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