Contagious

Overview

Contagious: Why Things Catch On is a New York Times bestseller by Wharton marketing professor Jonah Berger that explains the science behind why products and ideas become popular through word of mouth.

About the Author

Jonah Berger is a Marketing Professor at the Wharton School at the University of Pennsylvania and a world-renowned expert on word of mouth, viral marketing, social influence, and how products catch on. He was a student of Chip Heath at Stanford.

The STEPPS Framework

Berger identifies six principles that drive products to go viral:

1. Social Currency

• People share things that make them look good
• Create insider knowledge
• Leverage game mechanics
• Make people feel like insiders

2. Triggers

• Top of mind means tip of tongue
• Create mental associations
• Design environmental reminders
• Frequent triggers beat novel ones

3. Emotion

• When we care, we share
• High-arousal emotions drive sharing
• Awe, excitement, humor, anger work
• Sadness doesn't drive sharing

4. Public

• Built to show, built to grow
• Make the private public
• Behavioral residue
• Observable products spread faster

5. Practical Value

• News you can use
• Help people help others
• Highlight incredible value
• Frame deals effectively

6. Stories

• Information travels under the guise of idle chatter
• Build a Trojan Horse
• Make your message integral to the narrative
• Valuable virality

Key Insights

• Word of mouth is more effective than advertising
• Only 7% of word of mouth happens online
• The messenger matters as much as the message
• Virality isn't luck—it can be engineered
• Remarkable isn't enough; you need the right triggers

Applications for Startups

• Design products that are naturally sharable
• Create triggers that remind people of your product
• Build social currency into your offering
• Craft stories that carry your message
• Make usage public and visible
• Provide practical value worth sharing

Why It Matters for Founders

Most startups rely on word of mouth for growth but don't understand how to generate it systematically. Contagious provides a science-backed framework for making products and ideas spread.

Pricing

Available in hardcover, paperback, ebook, and audiobook formats at standard retail prices.