Contagious: How to Build Word of Mouth in the Digital Age by Jonah Berger explores the science behind why some ideas, products, and messages go viral while others do not. Berger identifies six key principles that drive contagiousness, providing insights into how businesses and individuals can create content and products that people can't resist sharing. Here are the key ideas from the book:
Social Currency
People like to share things that make them look good or in-the-know. Berger explains that we share information and products that enhance our social status or reputation. To make your content or product contagious, make sure it has an element of social currency that people will want to share to boost their image.
Certain cues or triggers in our environment prompt us to think about and share specific ideas or products. Berger discusses the concept of "top-of-mind" products and how businesses can create triggers that remind people of their offerings.
Emotional content is more likely to be shared. Berger explains that content that evokes strong emotions—whether positive or negative—tends to be shared more frequently than content that elicits no emotional response. Businesses should aim to connect with their audience on an emotional level.
People are more likely to imitate behavior they can observe. Berger discusses the importance of making products or behaviors more public, as this increases the likelihood of them being copied by others. Public visibility makes something more contagious.
Practical Value
Content that offers practical value or usefulness is more likely to be shared. Berger explains how useful information or tips are often shared because they can improve someone's life or solve a problem.
Stories have a unique power to make ideas sticky and memorable. Berger discusses the importance of crafting narratives around your content or product, as people are more likely to remember and share stories rather than statistics or facts.
The STEPPS Framework
Berger introduces the STEPPS framework, which summarizes the six principles of contagiousness (Social Currency, Triggers, Emotion, Public, Practical Value, and Stories). This framework provides a structured approach to creating contagious content or products.
The Power of Word of Mouth
The book emphasizes the importance of word of mouth in marketing and how businesses can harness it to increase their reach and influence. Word of mouth is often more effective than traditional advertising.
Case Studies and Examples
Throughout the book, Berger provides numerous real-world case studies and examples to illustrate how the principles of contagiousness work in various contexts, from marketing campaigns to viral videos.

"Contagious" by Jonah Berger offers valuable insights into why certain ideas, products, and messages gain traction and become contagious in the digital age. By understanding the science behind contagiousness and applying the principles discussed in the book, businesses and individuals can increase their chances of creating content and products that people are eager to share with others.