Contagious: Why things catch on

Jonah Berger


Rick Carabba
Actionable guide to the psychology of why brands stick, grow, & "catch on".
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Book Note


Chp 1 Social Currency

Optimize what people share to make them look smart, rich, cool.

Give people a visible symbol of status

Ask “Have they been let into a special secret?

Only 7% of WOM happens online (the face to face book by Keller, Ed, & Brad Fay (2012))

If something is supposed to be secret, people are more likely to share. Gives them social currency & makes them look good.

We have a neurological desire to share our thoughts, feelings, experiences, & creations.

Sharing personal opinions activates the same brain sensors that respond to rewards like food & money. ( “disclosing information about the self is intrinsically rewarding” Jason Mitchell & Diana Tamir (2012))

3 ways to make people feel good for sharing your stuff:

  1. Find inner remarkability


Ch 2 Triggers

When the music was changed to French music in a grocery store, the sales of French wine went up. Same for German. (“In store music effects product choice” David Hargreaves and Adrian North(1997))

In a case study students were shown different slogans for eating healthy then their eating habits were observed. Students who were shown the more generic slogan didn’t change their eating habits, but students who were shown the “tray” slogan used trays in their cafeteria and ate 25% more fruits & vegetables.

Will the message/content be triggered by something that comes up regularly in the environment of the target audience. Strong triggers are more effective than catchy slogans.

Rebecca Black’s song “Friday” was triggered every Friday. Kitkats were triggered by coffee. Budwieser used the greeting “wassup” to trigger their beer.

“Earworms” are melodies that are stuck in your head.

The poison parasite strategy: Make a rivals message in advertising a trigger for your own. Example. Antismoking campaign used the same ad setup as Marlboro.

How frequently does the intended stimulus (trigger) occur with your target audience?

More unusual links are better, if other strong associations come with the desired trigger it won’t work. Example, using peanut butter as a stimulus for milk. Jelly is already the dominant thought from peanut butter.

Pick triggers that happen close to where the desired behavior takes place.

Ch 3 Emotions

When we care we share.

Education articles were more likely to be shared than sports articles. Health more than political.

More interesting articles were 25% more likely to make the most emailed list. More useful, 30%.

Articles that evoke the emotion of “awe” are 30% more likely to be shared. Awe involves a sense of mystery, unexpectedness, & surprise.

Articles that evoke sadness are 16% less likely to be shared

Positive articles are more likely to be shared than negative ones

However, high arousal emotions like anger and anxiety were more likely to be shared as well.

The more physiological arousal your content provokes, the more likely it is to be shared.

Evokes awe, amusement, excitement, anger, anxiety

Excite or inspire people by showing them how they can make a difference.

Can physiological arousal not generated by the content also promote sharing? Yes.

Students who were instructed to jog shared an article twice as much as students in the relaxed group. Arousal due to the situation itself can promote people to share things more. (Jonah Berger, pg 122, contagious.)

When is my target audience the most physically aroused? What triggers are in places following physical arousal?

One way to generate WOM is to find ppl when they’re already aroused.

When we are aroused we share more than we planned, work groups who workout together may benefit bc it promotes sharing of ideas and opinions.

Ch 4 Public

Seeing other people do something makes them more likely to do it themselves.

Scientists call this “social proof”.

It’s why bartenders seed the tip jar early,

People can imitate only when they “see” what others are doing. How can the desired action be observable?

Observable things are more likely to be discussed.

Public visibility boosts word of mouth.

How can the private be made public?

Movember case study, everyone who supported the mens health prostate cancer movement rocked a mustache for the month of November.

Is there a way to generate social proof even when the product or idea isn’t top of mind or being talked about? Yes, behavioral residue.

Case study: Livestrong wristbands. They were worn and created triggers of their own.

Preventing a behavior requires the opposite, make the public private, less observable.

Ch 5 Practical Value

What makes things practically valuable enough to share?

Getting a deal.

The psychology of deals.

Daniel Kahneman won the Nobel prize for his work on prospect theory. It says that people make decisions in relative terms and not absolute terms.

Use higher reference points (retail price) to make people feel like they got a better deal. People are more likely to buy a $100 sweater marked down to $40 than a $45 sweater marked down to $35.

Another tenet of prospect theory is diminishing sensitivity. The idea that the same change has a smaller impact the farther it is from the reference point. Promotional offers that seem surprising or surpass expectations are more likely to be shared.

The rule of 100

Another factor that makes a deal seem valuable is it’s availability.

Restricting availability through scarcity & exclusivity makes a deal seem more valuable.

Quantity purchase limits increase sales by 50%. (“Framing the deal” Jeffrey Inman (1997))

Narrower content is more likely to be shared bc it reminds them of a specific friend or family member. It’s a deeper connection.

Ch 6 Stories

People don’t think in terms of information they think in terms of narratives. How can we use stories to get ppl talking? Need to build a Trojan horse—a carrier narrative that people will share while talking about our product or idea along the way.

The best part of the story and the brand name should be intertwined.

Make sure the info you want shared is crucial to the narrative.


The 6 principles broken down into STEPPS:

Social Currency: We share things that make us look good

Triggers: Top of mind, tip of tongue

Emotion: when we care we share

Public: built to show, built to grow

Practical Value: news you can use

Stories: Info travels under the guise of idle character.

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Rick Carabba is a writer looking for uncommon ideas that improve people's lives.