Narrator: How does a new, high-end steakhouse in a city famous for its humble cheesesteaks make a name for itself? Howard Wein faced this exact problem when launching Barclay Prime in Philadelphia. Instead of a massive ad campaign, he created a single, outrageous menu item: a one-hundred-dollar cheesesteak. Made with Kobe beef, shaved truffles, and served with a split of champagne, it was an absurdity. Yet, it worked. The story of the hundred-dollar cheesesteak spread like wildfire, generating immense buzz and turning the restaurant into a resounding success. This wasn't a lucky break; it was a masterclass in making an idea spread.

In his book Contagious: Why Things Catch On, marketing professor Jonah Berger dissects the science behind social transmission. He argues that the success of products and ideas, from hundred-dollar cheesesteaks to viral videos, is not random. It is driven by a set of six core principles, a formula that explains why some things become popular while others fade into obscurity.

Narrator: People constantly manage their public image, and the things they talk about are a crucial part of that. Sharing information that makes one seem smart, cool, or in-the-know is like a currency that buys positive impressions from others. Berger calls this Social Currency. To make an idea contagious, it must provide people with a way to look good.

One of the most effective ways to generate Social Currency is by creating a sense of exclusivity and insider knowledge. Consider the story of Please Don't Tell, a bar in New York City. It has no sign and no listed address. To get in, one must first enter an adjacent hot dog restaurant, step into a vintage phone booth, and dial a secret number. If there's space, the back of the phone booth opens to reveal the hidden bar. This secrecy wasn't a flaw; it was the bar's greatest marketing asset. Knowing about Please Don't Tell, and especially getting inside, gave patrons immense Social Currency. It was a secret they were eager to share because it made them feel like insiders. By making people feel special and in-the-know, brands can craft messages that people are not just willing, but eager, to spread.

Narrator: While interesting products get immediate buzz, they don't necessarily get ongoing word of mouth. For an idea to have staying power, it needs to be triggered. Triggers are stimuli in our environment that remind us of a related product or idea. The more frequently something is triggered, the more it stays top of mind, and the more likely it is to be talked about.

In 2007, the Kit Kat candy bar was in decline. Marketer Colleen Chorak was tasked with reviving it on a small budget. Instead of a flashy ad, she focused on triggers. Research showed that people often ate Kit Kats during a break, frequently with a hot beverage. Chorak launched a simple radio campaign that repeatedly linked the two: "A break's a break, but a Kit Kat and coffee is a perfect break." This created a new, powerful trigger. Every time someone thought about having a coffee break, they were subtly reminded of Kit Kat. The result was astounding. Sales surged by a third in just one year. The lesson is that it's often better to be triggered than to be interesting. An exciting but rarely-seen product, like a trip to Disney World, gets talked about far less than a breakfast cereal like Cheerios, which is triggered every single morning.

Narrator: Emotional content is inherently more shareable. When we feel a strong emotion, we are compelled to talk about it. However, not all emotions are created equal. Berger's research reveals that the key factor is physiological arousal. High-arousal emotions—like awe, excitement, anger, and anxiety—drive us to action, including sharing. Low-arousal emotions, such as sadness or contentment, actually suppress it.

The story of Dave Carroll and his song "United Breaks Guitars" is a perfect example. When United Airlines baggage handlers broke his expensive guitar and the company refused to compensate him, Carroll didn't just feel sad. He felt angry and wronged. He channeled this high-arousal emotion into a clever music video that he posted on YouTube. The video tapped into a shared sense of frustration with corporate indifference, went viral, and ultimately cost United Airlines millions in stock value and brand damage. The song spread not because it was a musical masterpiece, but because it ignited a high-arousal emotion—anger—that people felt compelled to share. To make content contagious, it must strike an emotional chord, and ideally, one that gets the heart pumping.

Narrator: Humans are natural imitators. We look to others for cues on what to do, what to wear, and what to buy. This principle of social proof only works, however, if the behavior is observable. If something is hard to see, it's hard to imitate. Therefore, making products and ideas more public is essential for them to catch on.

A brilliant, subtle example of this is Apple's decision to flip the logo on its laptops. In the early days, the Apple logo was oriented to face the user when the laptop was closed. But Steve Jobs and his team realized that when the laptop was open and in use, the logo appeared upside down to everyone else. They made a simple change: they flipped it. Now, every time a user opens their laptop in a coffee shop or library, they present a perfectly oriented Apple logo to the world. This decision turned every user into a walking advertisement, making a private action—using a computer—a public endorsement. Similarly, the Movember Foundation made a private issue—men's health—public by encouraging men to grow moustaches, a highly visible and talkable symbol. If something is built to show, it's built to grow.

Narrator: People have an innate desire to help others. One of the easiest ways to do this is by sharing useful information. Content that offers practical value—saving people time, improving their health, or helping them save money—is incredibly contagious.

This principle explains the viral success of Ken Craig, an 86-year-old man from Oklahoma. His daughter-in-law filmed him demonstrating a remarkably simple trick for shucking corn: microwave the ear for four minutes, cut off the bottom, and the corn slides out perfectly clean, with no silky threads. The video wasn't professionally produced or emotionally charged, but it solved a common, annoying problem. It was pure practical value. Millions of people watched and shared it, not to look cool, but simply because it was "news you can use." Providing helpful advice or useful tips is one of the most reliable ways to get people to pass a message along.

Narrator: Facts and data are often dry and forgettable. Stories, on the other hand, are engaging and memorable. A good story acts as a "Trojan Horse," carrying a lesson or a brand message inside a compelling narrative that people will want to retell. For this to be effective, however, the brand's message must be integral to the plot.

The story of Jared Fogle is a classic example. In the late 1990s, the college student lost 245 pounds by eating Subway sandwiches every day. People didn't share nutritional statistics about Subway's menu; they shared the incredible story of Jared's transformation. The narrative was simple, inspiring, and impossible to tell without mentioning Subway. The brand's core message—that it offered a healthier fast-food alternative—was woven so deeply into the story that it became part of the legend. By wrapping a product's benefits in a personal and compelling narrative, brands can create a message that not only spreads but carries the crucial information along with it.

Narrator: The single most important takeaway from Contagious is that virality is not an accident. It is a result of thoughtful design. By understanding the fundamental psychology of why people talk and share, we can engineer our products, ideas, and behaviors to become more infectious. The six principles of the STEPPS framework—Social Currency, Triggers, Emotion, Public, Practical Value, and Stories—provide a clear and actionable blueprint for doing just that.

The true power of Jonah Berger's work is that it demystifies the process of influence, making it accessible to everyone, not just large corporations with vast marketing budgets. It leaves us with a profound challenge: now that we understand the science of what makes ideas spread, what valuable, positive, and important messages will we choose to make contagious?