Contagious by Jonah Berger

Contagious book review

I finished reading Contagious, by Jonah Berger. The book is about why things go viral. The author is not very concise; a lot of his examples have extraneous details, and he often repeats himself. Overall, the book had lots of interesting insights, but could have been half as long.

The book starts off by saying that things go viral not because of a small group of influencers, but because it is shared by lots of average people. There are six principles that make things go viral, and most viral ideas have all or a combination of the principles. The principles are:

1. Social Currency
People want to look good, so they share things that make them look good. Also, sharing is pleasurable; sharing personal opinions activates the same brain reward pathways as food and money, so it is a completely natural thing for people to do. Then enabling people to mint social currency, enabling people to make themselves look better, while promoting the business along the way, is a good tool for generating word of mouth. There are three ways to mine social currency:

1. Find inner remarkability to provoke discussion. When someone is talking about something remarkable, they seem more remarkable.

  • Snapple drinks have “Real Facts” under their caps, such as “A ball of glass will bounce higher than a ball of rubber.”
  • Blendtec launched a video series, “Will it Blend?”, that showed their blenders were capable of blending things normal blenders would not be able to, such as iPhones and planks of wood.

2. Leverage game mechanics, like loyalty programs do. Intrapersonally, “winning” or getting to the next level of a frequent flier program feels rewarding. Interpersonally, game mechanics encourage social comparison. For example, people would often use Foursquare and check in to become Mayor of a location. People are also encouraged to boast about their rewards. In turn, they spread awareness about the brand or product.

3. Make people feel like insiders. When a product is scarce or exclusive, it is more desirable.


  • McDonald’s McRib did not sell well when it was available at every store. But once they started rotating the franchises that had it, it started to sell well because it was scarce.
  • Disney sells older movies such as Snow White for a limited amount of time, then puts them back into the “Disney Vault” and stops selling them.
  • Rue La La has online clothing sample sales and is by invitation only, so it grew from word-of-mouth publicity.
  • There are “secret” bars such as Needle in Thread, that do not have any signs out front and give the impression that their existence is not public knowledge. To get to Needle and Thread, you have to walk through another bar, pick up a phone, then go through a door that looks like part of the wall, and you usually have to make a reservation.

People are perfectly happy to share things for free, without monetary incentive. Take fantasy football. For most people, the monetary incentive is not why they spend hours playing. The social incentive is a lot more important, to look good by winning and to have something to talk about.

2. Triggers
“Top of mind, tip of tongue.” Attaching a product to something else will bring the product to mind whenever they see that trigger. It’s not just whether something is interesting or not that it will be shared. People talk about Cheerios more than Disney World. While Disney World is an amazing experience, people are seldom reminded about it. Whereas Cheerios has lots of ongoing word-of-mouth, because breakfast each morning is a potential trigger. Interesting products receive more immediate word-of-mouth, but do not sustain it. That is not a bad thing; for products such as movies, immediate word-of-mouth is more important than ongoing word-of-mouth.

Examples of triggers:

  • When the NASA Pathfinder landed on Mars, sales of Mars bars increased without a marketing campaign.
  • When supermarkets play French music, people are more likely buy French wine. When supermarkets play German music, people are more likely to buy German wine.
  • Having people vote in a schoolhouse makes people more likely to pass the school budget.
  • Rebecca Black’s “Friday” is most searched/watched on Fridays.
  • Kit Kat lifted sales by 8% by having a low-budget radio campaign that called Kit Kats “a break’s best friend”. These ads featured a Kit Kat bar on the counter next to coffee, or someone buying coffee and a Kit Kat together. This associated Kit Kats with coffee, and coffee is a frequent trigger.

Even if a marketing campaign is considered bad (e.g. corny, not very catchy), if the product is attached to a good trigger, it could lead to higher conversions.

Negative press is good when it makes a product top of mind. For example, books by new authors sell better after a review is published, even if that review is negative, because people are aware that that book even exists.

Competitors can be used as triggers by making the rival message a trigger for your own message. In one famous antismoking campaign, there was a Marlboro cowboy saying to another, “Bob, I’ve got emphysema.” In that way, whenever someone saw a Marlboro ad, they would be reminded of the antismoking ad.

Effective triggers are frequent (vs. seasonal or topical). However, there is a tradeoff between frequency and strength of the trigger link. A trigger might already have many things related to it, such as the color red. Red is already related to roses, Coca-Cola, blood, fast cars, etc., so trying to make the color red a trigger is not effective. Also, some triggers already have very strong links, such as peanut butter to jelly, so a more unusual link would be better.
Triggers should consider context, like geography, where people live, where people actually go about buying a product (grocery store? online?), the time of year.

3. Emotion
When people care, they will share. Stories that evoke strong emotions are more likely to be shared. One might think that positive stories would be shared more than negative stories because positive stories make people feel good, but that is not the case. What gets people to share are things that generate high physiological arousal (people are more alert, blood is pumping faster), because in such a state, we are more primed to act. High arousal emotions include positive emotions such as awe, amusement, and excitement, and negative emotions such as anger and anxiety. Low arousal emotions stifle action, so people are less likely to share. Low arousal emotions include contentment and sadness.

Google’s “Parisian Love” campaign told a story and showed the underlying human reasons why people search, while highlighting Google search result features.

On the downside of sharing, gossip, malicious statements, and rumors spread quickly too, so businesses must actively monitor social networks and quickly deal with customers’ negative high-arousal emotions before they spread.

People are more likely to share (or overshare) when they are in an aroused state. Even exercising makes people more likely to share. So ads during emotionally intense TV shows may be more effective, as are ads at the gym. An example application of this is, on crime shows, anxiety peaks in the middle, whereas on game shows, excitement peaks at the end, so ads shown at this time are more likely to be talked about.

4. Public
Something that is built to show is built to grow.

People tend to imitate each other. If other people are doing it, then it must be a good idea, there is social proof. For example, in a new city, given several options of restaurants to eat at, I would be more likely to eat in a restaurant that has a lot of people. In my college, most of my classmates went into finance or consulting because that is what most people did.
Observable (public) things are more likely to be discussed than private things. A good marketing tactic is to take private behavior and make it public. For example, charitable giving tends to be private. No-shave Movember makes this private act public; people grow their beards and raise money for men’s health issues. Even if someone participates in Movember and does not raise money, they are still raising awareness and prompting conversations about men’s health.

Some products advertise themselves, such as clothes with brand logos. Or with iPhones, the default email footer says “Sent from my iPhone”. This spreads brand awareness.
Some products are only consumed at certain times, or privately. Companies can provide behavioral residue, “the physical traces or remnants that most actions or behaviors leave in their wake,” to generate awareness when the products are not being used. For example, Lululemon provides solid reusable bags. When people see these bags, it acts as a trigger to keep the brand at the top of their mind. To encourage people to vote, a private act, polling stations give “I Voted” stickers to voters.

For campaigns that seek to prevent behavior, instead of making the private public, they need to make the public private, they need to make others’ behavior less observable. Ads should highlight what people should do, instead of what they are currently doing. For example, the 1998-2004 “Just Say No” anti-drug campaigns made kids who saw the ad more likely to try marijuana. That is because, though the ads said drugs were bad, it implied that people were doing drugs. And since other people were doing drugs, viewers of the ad were more interested in trying them too. Another example was with Arizona’s Petrified Forest National Park. They had signs to discourage people from stealing petrified wood. One sign said “many past visitors have removed petrified wood from the Park, changing the natural state of the Petrified Forest.” This sign doubled the number of people stealing wood, because the sign was social proof that others were stealing. The other sign, “Please don’t remove the petrified wood from the Park, in order to preserve the natural state of the Petrified Forest,” reduced theft. Instead of focusing on the fact that other people stole wood, it focused on the positive effects of not taking wood.

5. Practical Value
While marketing strategies that employ Social Currency are about making the sharer look better, sharing things with Practical Value is about helping others. People like to give advice and save each other time and money, “sharing is caring”.

People are more likely to share promotions that seem like better deals. What makes a promotion seem like a good deal? People don’t evaluate things in absolute terms, they evaluate based on relative terms. The size of the discount relative to the original price matters. Many infomercials provide a reference price, then say you’re getting a great deal because you are getting the product for way cheaper than that price. Just marking something as on sale increases purchases, even when the sale price is the same as the original price.

Deals are more likely to be shared when they highlight incredible value. Factors in highlighting value:
1. Expectations. If a sale price is surprising, much lower than expectations, it will be shared.
Timing and frequency are important. Since rug stores are always having “going out of business” sales, the sale price becomes the norm, the expected price, so the sales will have little effect on demand.

2. Availability. Restricting availability by making a product scarcer or more exclusive will make the product seem more valuable.

  • Offering a product for a limited time will encourage people to act so that they can get the product.
  • Limiting the quantity of a product that can be purchased encourages people to buy because people think there is high demand for the item.
  • Restricting access to promotional offers is also a useful tactic, because than the offer is more valuable.

Rule of 100
If an item is <$100, use percentages to describe the discount, because the numerical discount will not be impressive.
If an item is >=$100, use the numerical discount.

Broadly relevant content might be shared more because of the large audience, but content with a narrow audience can be more viral because it is obviously relevant.

6. Stories
Stories provide an easily sharable narrative. Even in idle chatter, these stories share valuable information about products. The product should be an essential part of the story. For example, one bad marketing campaign was when a man crashed the Olympic diving event and did a belly flop in a tutu. He also had a website URL on his chest. But the website URL is not what made the story memorable and the stunt had nothing to do with what the website did, so people would omit that detail when they retold the story.

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