Nicolas Cognaux - Tech entrepreneur & engineer

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Contagious by Jonah Berger

2020-03-08 Nicolas Cognaux 8 min readBook Review

Contagious: Why Things Catch On”, the title says it all on the content of that book. Contagious is a marketing guide. If you’re planning to start marketing or selling goods, have a project to advertise, want your ideas to be remembered,… this book is for you!

Cover: Contagious: Why Things Catch On

I discovered Contagious during my second entrepreneurial experience, at Myk Applications. I was, at that time, in charge of the technical aspects of the app and had no background in marketing or sales.

Lionel, the CEO of the company proposed a small exercise: From a small pile of books he selected, he offered one to each person. He selected them to challenge each member with a book that was radically different from his background. I ended up with Contagious, which was at the opposite of my technical preoccupations. And that worked on me: building a product is nice, but I had no idea how to sell it! Here is what I took away from the book.

Who is the public of the book?

As explained in the book, the public of Contagious is pretty broad: You don’t need a product or an idea to spread. There are numerous examples in the book such as a hidden bar in NYC, an awareness campaign about cancer awareness, how a company used Youtube to promote “usually boring” products,…

Contagious helps to understand marketing strategies and how those are created to be viral.


The whole book is articulated around 6 main chapters. Each one is a key aspect to master to optimize the virality of your idea, product or service. The acronym is STEPPS: Social Currency, Trigger, Emotion, Public, Practical Value, Stories.

Each chapter takes at least an example to illustrate its importance and how companies adapted their communication or product. Let’s dive into them!

Social Currency: We share things that can make us look good or smart

When we tell a story, explain something, or present a discovery we made, we always (consciously or not) do it to look good. We “trade” the story in exchange for reconnaissance from the others. That’s the social currency.

What we talk about, inevitably determines what others perceive of us, which leads us to share things that make us seem more entertaining, clever, smart, and/or funny.

To take advantage of that, companies can shape their stories with three things:

  • Find inner remarkability: Make it unique or surprising. Make your idea different from the market. Something completely different and standing out is something that’ll be shared easily.

  • Gamify it: Airbnb uses that technic with the rewards programs and coupons: If you invite a friend, he receives a reward. Sharing the coupon with him instantly grant you values.

  • Make people feel like insiders: Exclusivity drives desirability. People love to be the privileged ones that have access to a product. Membership clubs and invite-only services use that a lot. The Centurion® Card from American Express is a great example of that.

You don’t have to master the three points above but the more you cover, the more your story will be shared.

If something is truly successful, people will want to talk about or buy your product or service if it means they will gain value from the product or experience, as well as look good to others. The social currency highly depends on the product or service offered.

Trigger: The more you think about it, the more you share it

While social currency gets people to talk about things, “triggers” keep ideas and products top of mind. A trigger is a stimulus to your brain. It connects your actions to a specific moment or specific behavior.

A good trigger is a frequent and strong one. For example, KitKat used the coffee break as a trigger. They created a huge communication campaign linking Kitkat with the coffee break. That was the famous “Have a break, have a Kitkat” sentence. This is a really powerful trigger as a lot of people consume coffee and will link the coffee to Kitkat.

A trigger can also be more subtle: Our brain is good at making links, and colors can be exploited as triggers. For example, if you think about the red color, you’ll certainly think Coca Cola. They used the color as a trigger.

When you think about your product or service, it’s important to think about the environment and habits of your consumers. There are habits that you can link or even specific moments. The more frequent, the better.

Emotion: When we are touched, we share

Every story comes with emotions. Something that makes you happy will likely be more shared. It’s the same when something makes you angry or annoyed. The book highlights the link between the emotions and the likelihood of a story to be shared.

The author classifies every story with two aspects:

  • Is it highly arousal or not?
  • Is it a positive or negative emotion?

A high arousal story is more likely to create a reaction. Your story doesn’t always have to be positive or negative. It just has to create arousal.

For example, excitement, amusement or anger are efficient to provoke a reaction. Understanding arousal can help you drive viral content for yourself, by focusing less on the features and informative aspects. That’s exactly the strategy used by Nike in their commercials). They don’t even present their products, everything is related to the emotion.

Public: Make it visible

Something that’s not known or visible is less likely to become popular. People have to see the product or the service, to be triggered. Making a product visible is a way to self-promote it.

Berger calls the concept of looking at what others are doing to resolve our uncertainty, “social proof”. Individuals imitate actions because other’s choices provide information that helps them decide how to do something. Berger provides an example, of looking for a restaurant in an unfamiliar city: we look for restaurants that are full of people (because it must be delicious or hip), and we walk by the empty restaurants (food too expensive or bland).

If your product or idea isn’t supposed to be public, the book explains the concept of “Making the private public”. That concept was used by the Movember movement, which is a prevention movement of the prostate and testicular cancer. Not sexy.., but to make it public, the participants grow a beard in November. That distinctive look intrigues others and leads to discussions about the movement.

Hotmail is also a good example of using the self-advertising to become viral. In the early days of Hotmail, the founders had to make it known and viral. Someone using a specific email client wasn’t obvious, so the team had to figure a way to make it known: They simply signed every email with “Get your free email at Hotmail”. That simple move leads to millions of new subscribers.

Practical Value: It has to be useful

A story also has to be useful for the audience. Otherwise, it’ll not be shared. Practical value is all about sharing useful information that will help others save time, energy and resources.

The key to being successful for companies is to position this useful information in a way that stands out to consumers.

In this chapter, two theories are exposed. The prospect theory states that people don’t evaluate things in absolute terms. They evaluate them relative to a comparison standard, or “reference point.” That’s why Amazon always shows the real price and the discounted price. Buyers are more likely to buy because they directly see the practical value.

The second theory is about the perception of a discount. Researchers find that whether a discount seems larger as money or percentage off depends on the original price. For things like laptops or other expensive items, framing price reductions in dollar terms (rather than percentage terms) makes them seem like a better offer. If the product’s price is less than $100, the Rule of 100 says that percentage discounts will seem larger.

Stories: A story is easier to share

Virality is most valuable when the brand or product benefit is integral to the story. If people have to describe your product when explaining their stories, you won. If you find a great bargain, you will probably describe your entire experience when you recommend the deal to your friends.

Most people miss details, so to get customers to think about your idea, craft the story with key factors critical to your brand and add other “sticky” factors: humor, creativity, quirky.


Contagious is a Must Read for marketeers and people that want to understand customer behaviors and advertisements. The book is really easy to read and, thanks to the examples it contains, is even enjoyable!

One downside: After reading it, you’ll constantly think S.T.E.P.P.S. when seeing ads and product presentations!

About Jonah Berger

Jonah Berger is a professor at the Wharton School of the University of Pennsylvania. He published multiple articles, papers and online courses about virality and social influence.

“Jonah Berger knows more about what makes information ‘go viral’ than anyone in the world.” —Daniel Gilbert, author of the bestseller Stumbling on Happiness

He also published Invisible Influence, a book on how we are driven in our choices and behaviors by marketing and our environment.

I personally bought Contagious on Amazon and have it on my Kindle to get back to it regularly.

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Nicolas Cognaux (Gp2mv3) - Tech entrepreneur & engineer

About Nicolas Cognaux

Entrepreneur and CTO. I’m an electrical engineer and passionate about software development. I post about technologies, entrepreneurship, projects, and geeky stuff. Follow me on social media to stay updated.

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