Contagious by Jonah Berger, published by Simon & Schuster in 2013, is a book about word of mouth: why people talk about some products, ideas and stories and ignore others. Berger is a marketing professor at the Wharton School, and he builds the book on his own research into sharing, online and offline. His conclusion is that virality comes less from luck or a big ad budget and more from features you can design into a product or message.
What is Contagious about?
Berger starts by pointing out that most word of mouth happens face to face, and that a recommendation from a friend persuades far more than any advert. If that is true, the question for a marketer is what makes people bring something up in conversation. His answer is a framework of six principles, which he groups under the acronym STEPPS.
Social currency covers the things that make the sharer look smart, cool or in the know. Triggers are cues in daily life that remind people of a product, such as a day of the week or a common object. Emotion is about feelings that fire people up, since content that excites or angers travels further than content that makes people calm or sad. Public covers visibility: if people can see others using something, they copy it. Practical value is the urge to help others with useful tips and deals. Stories are the vessel: people pass on narratives, and a brand woven into a good story travels with it.
Each principle gets its own chapter, built around a memorable case and the research behind it. The examples range from a restaurant with a hidden entrance to a blender company that blends odd objects on video, and from campaigns that went wrong to ones that spread with almost no spending. The final chapter shows how the six principles combine.
What are the main lessons for founders?
- Give people a reason to brag. Insider access, a secret menu or a hard-to-earn badge turns customers into storytellers because sharing makes them look good.
- Tie your product to a frequent cue. A brand linked to something people see every day gets mentioned more than one linked to a rare event.
- Aim for the right emotion. Content that sparks awe, amusement or righteous anger gets shared. Content that leaves people content and relaxed stays put.
- Make usage visible. Branded packaging, public sign-ups or a visible feature help others notice and imitate your users.
- Wrap your message in a story. A useful how-to video or a customer story with your product at its centre carries the brand along with it.
Who should read Contagious?
The book suits early founders and small marketing teams who cannot outspend competitors and need customers to spread the word. It fits consumer brands, community products, events and content businesses especially well. Product managers designing sharing features will also find ideas to test.
Founders selling complex B2B products with long sales cycles will get less from it, since many examples involve consumer goods and online content. Experienced marketers will know the principles already from campaigns they have run.
How do you put Contagious to work this week?
- Score your product or latest campaign against each of the six principles on a 1 to 5 scale. Pick the weakest two.
- Design one small feature or perk that gives customers status, such as early access or a referral reward with a visible badge.
- Write one genuinely useful piece of content for your audience, with your product woven into the story, and share it with 20 customers.
The free Social Media 101 module in the Fe/male Switch Startup School helps you turn those shareable ideas into posts that reach your audience.
Where does Contagious fall short?
The six principles explain why things spread, but the book gives less help with how to measure sharing or connect it to sales. Many examples date from the early 2010s, before short video apps and algorithmic feeds changed how content travels online. The research is strongest for consumer products and media, and B2B founders need to translate it. For the product side of habit and repeat use, read Hooked, and for a structured testing process around growth, read Hacking Growth.