Why do things catch on and become viral?

I was always curious about the way people make decisions as this could have a huge impact on the products I may be building or the content that I put out. In the past I read all the typical popular books claiming to offer a scientific deconstruction of human behaviour. "Contagious" by Jonah Berger, a Wharton professor of marketing, is my most recent read in this field of behavioral economics. Jonah's book is focusing on virality and promises to offer a theory of virality and to answer the million dollar question: "Why do things catch on?". He starts the book by acknowledging the influence books like "The Tipping Point" had on him, and he promises to advance the subject by providing scientific arguments rather than entertaining stories.

Reducing the individual decisions (which can include psychological, social or cognitive factors) to a few "scientifically" proven laws is an ambitious task to say the least. Unfortunately it is also a task that I fear Jonah has failed at with his book. Filled with fairly known business stories and not that many scientific studies, "Contagious" reads just like any other popular bestseller in the genre. The result is still an entertaining book that can offer a lot of value to the beginner business man.

Contagious proposes 6 laws that contribute to the mixture of an "infectious" idea or product. They are:

Social currency

Does sharing your message make people look good? Social currency refers to our need of being perceived as interesting by our peers. We are doing this by sharing stories that are out of the ordinary, like the $100 Philly cheese steak sandwich or interesting Snapple facts.

Another technique is to build gamification elements into the products themselves, like Foursquare famously did (the irony is that the company was doing much better when the book was published).

Or one can try to make the consumers feel like insiders, by capitalizing on our innate attraction to secrets. Jonah illustrates this concept with Please Don't Tell, an exclusive bar hidden inside a hot dog 


Are you constantly reminding your users of the product? This principle is about piggybacking on existing patterns of usage. One example is that of Kit Kat, which turned around its sales decline by positioning the chocolate bar as the perfect complement to coffee. The hypothesis being that consumers would be infected with the idea to associate the chocolate bar with coffee consumption, which is one of the most popular habits.


Is your message emotional enough? Jonah spend a lot of time trying to understand what emotions make people to want to share something. It's this chapter that contains most of the details on the scientific method behind this book. He found that some emotions are more viral than others. He found out that most positive emotions (especially awe) but also negative emotions like anger or anxiety to be highly contagious. Sadness however is one emotion that unfolds in private and should be avoided.

Public or Social Proof

Can people see your clients using your products or services? Because nothing influences the buying decision more than being exposed to other people using a certain product. Emphasizing this led Steve Jobs to reverse the iconic Apple logo engraved on Macbooks from facing the user to facing the public.

Practical Value

Is it the information you are putting out there any useful? Because if it is people will be most likely to share it with their friends in need. Jonah points to a Vanguard newsletter packed with basic financial advice that he frequently forwards to friends.

Offering discounts is probably the most popular technique to build practicality in the value of the offering. However framing the discount in the right manner can make all the difference and to this extent we are being introduced about the rule of 100: If less than $100, the discount should be communicated the discount as a percentage (%). For products more expensive than $100 the discount gets more viral if presented as an absolute dollar value.


Are your facts wrapped in good stories? Because people don't remember any figures and tend to communicate through stories. Stories thus serve like a Trojan horse, being embraced and shared because of their memorability, but hiding the core message the company is interested in inside its belly. The story of the guy who lost a lot of weight by eating only Subway or the Will it Blend campaign are illustration of this point.

Contagious is a short book, easily digestible in a few hours. I recommend you pick if you want some hints for your next marketing campaign.

Do you have other virality patterns that you discovered in your work? Please share ....