Contagious: Why Things Catch On

Contagious: Why Things Catch On (2013) by Jonah Berger, Professor of Marketing at the University of Pennsylvania’s Wharton School of Business, examines the science behind why certain products, ideas, and behaviors become viral. Drawing from his research into social influence and consumer behavior, Berger challenges conventional wisdom about viral marketing, demonstrating that social transmission follows predictable patterns rather than occurring randomly. Through academic research, case studies, and practical examples, he presents six key principles that drive people to share content. He offers a framework for creating contagious products and ideas that resonate in both online and offline contexts. Contagious explores themes of The Limitations of Traditional Marketing Explanations, The Hidden Mechanics Behind Viral Success, and The Psychology of Sharing.

This study guide refers to the 2013 Simon & Schuster eBook edition.

Summary

In Contagious, Berger examines the scientific principles behind why certain products, ideas, and behaviors achieve viral status while others fail to gain traction. The book challenges conventional wisdom about viral marketing, particularly the notion that social epidemics primarily depend on influential individuals. Instead, he proves that the inherent characteristics of messages and ideas, rather than the status of their initial promoters, drive their transmission. Through extensive research and analysis, Berger shows how seemingly spontaneous viral phenomena follow predictable patterns.

Berger introduces his framework through the case study of Barclay Prime, a Philadelphia steakhouse that gained notoriety and success through its $100 cheesesteak, created by experienced hospitality professional Howard Wein. This example sets up Berger’s argument that viral success follows predictable patterns rather than occurring randomly. The author establishes that word-of-mouth communication influences between 20 and 50 percent of purchasing decisions, proving more effective than traditional advertising due to its perceived objectivity and natural targeting. This insight explains why personal recommendations carry more weight than conventional marketing messages.

The book outlines six key principles that drive social transmission, known as STEPPS: Social Currency, Triggers, Emotion, Public, Practical Value, and Stories. Social Currency refers to how sharing certain information makes people appear knowledgeable or cool to others. Berger illustrates this through examples like Please Don’t Tell, a speakeasy-style bar in New York City that generated buzz through its hidden entrance and exclusive atmosphere, accessed only through a vintage phone booth inside a hot dog restaurant. The principle manifests through three main mechanisms: inner remarkability, game mechanics, and making people feel like insiders.

The Triggers chapter reveals how environmental cues influence behavior and conversation more than inherent interest or excitement. Through research with word-of-mouth marketing company BzzAgent and its founder, Dave Balter, Berger demonstrates that products that maintain consistent visibility through environmental triggers generate more sustained discussion than those relying solely on initial excitement. He cites examples such as Rebecca Black’s song “Friday” receiving predictable weekly attention spikes each Friday, Mars bars experiencing increased sales during NASA’s Mars missions, and Cheerios generating more discussion than Disney World because breakfast is a daily trigger. 

Emotion plays a crucial role in content sharing, Berger argues, but not in the way most marketers assume. Through analysis of thousands of New York Times articles, Berger discovered that the key factor driving sharing is not whether content evokes positive or negative emotions but rather the level of physiological arousal those emotions generate. High-arousal emotions like anger, anxiety, and amusement increase sharing, while low-arousal emotions such as sadness and contentment reduce it. This finding manifests in varied examples, from singer Susan Boyle’s Britain’s Got Talent audition generating over 100 million views due to its awe-inspiring nature to musician Dave Carroll’s “United Breaks Guitars” video achieving viral success through the anger it provoked about poor customer service.

The Public principle emphasizes how visible behaviors spread more readily than private ones. Berger presents examples such as Apple’s strategic logo orientation on laptops (Steve Jobs decided to make the Apple logo face outward for observers rather than inward for users) and the success of awareness campaigns like Movember and LiveStrong, which transformed private support into visible advocacy through mustaches and yellow wristbands, respectively. The chapter also warns about the potential negative effects of visibility. For example, anti-drug campaigns inadvertently normalized undesired behaviors by highlighting the prevalence of drug usage among teens.

Berger argues that Practical Value drives sharing through people’s desire to help others. He explains how consumers evaluate deals and discounts, introducing concepts like the Rule of 100, which suggests using percentage discounts for items under $100 and absolute dollar amounts for items over $100. The chapter emphasizes how restrictions and limits can enhance perceived value, citing research showing that adding quantity purchase limits increased sales by more than 50 percent, and how narrowly targeted content often generates more sharing than broadly applicable information.

The Stories chapter examines how narratives serve as vessels for information transmission. Berger introduces the concept of “valuable virality,” arguing that effective marketing stories must integrate products or messages as essential narrative elements rather than as removable details. He emphasizes that viral content must maintain marketing effectiveness while spreading widely. 

The book concludes with the story of Vietnamese nail salons in America, demonstrating how all six principles can work together in real-world situations. Beginning with actress Tippi Hedren’s interaction with Vietnamese refugees at Hope Village near Sacramento in 1975, the narrative shows how social currency, triggers, emotion, public visibility, practical value, and compelling stories contributed to Vietnamese Americans eventually constituting 80 percent of California’s nail technicians and over 40 percent nationwide. 

Throughout Contagious, Berger maintains that viral success results from specific, identifiable factors rather than chance or inherent characteristics of the messenger. By understanding and implementing the STEPPS framework, he argues organizations can increase their likelihood of achieving widespread social transmission of ideas and products. The book provides both theoretical understanding and practical guidance, demonstrating how these principles apply across various contexts and industries based on the psychology at work in human behavior.