Psychology
Social proof
When we are unsure what to do, we copy what other people are doing, especially people like us, so crowds, queues and best-sellers persuade.
2020s
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2022Flipvertising
Filled searchers' feeds with reviews and unboxings Samsung had not paid for, so the phone reached sceptical young buyers through other people's verdicts.
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2022Runner 321
Once Boston held bib 321, all six of the biggest marathons followed, even those sponsored by rivals, and each new race made signing up feel like the done thing.
2010s
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2018Nothing Beats a Londoner
Released the film in pieces through the young athletes' own Instagram posts, each linking to the next, so followers saw people like them spreading it first.
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#NuggsForCarterWendy's2017
#NuggsForCarter
Each jump in the retweet count was public, and seeing millions already behind Carter made joining in feel like the obvious thing to do.
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2017Trash Isles
With Al Gore as first citizen and a population that grew to about 220,000, every new citizen showed the next person that plenty of others were joining.
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2016Like My Addiction ("Louise Delage")
Louise's feed piled up tens of thousands of likes and admiring comments, and each one made her constant drinking look normal to the next follower.
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2016Spotify Wrapped
Fills feeds with friends' recaps every December, so joining in feels like what everyone is doing and each post pulls in more.
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2015Shot on iPhone ("World Gallery")
Every billboard shows a photo by an ordinary iPhone user, not a professional, telling passers-by that people just like them take pictures this good.
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2014Puppy Love
Posted online four days before the game, it passed 23 million views and over a million shares by kickoff, and each share told others it was the ad to watch.
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2011The Museum of Me
Each visitor's shared museum, 790,000 in the first two weeks, nudged their friends to connect and tour a gallery of their own.
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Share a Coke with...Coca-Cola2011
Share a Coke
Every shared photo of a named bottle sent more people hunting for their own, until the hunt fed itself.
2000s
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2009Walk-In Fridge
Seeded to fans online a week before broadcast, it passed two million views in two weeks, and students building their own fridges drew still more people in.
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Fiesta MovementFord2009
Fiesta Movement
Let 100 social-media agents post unscripted about a car not yet unveiled in America, and people trust what others like them say far more than a carmaker's claims.
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2009The Fun Theory ("Piano Stairs")
Films commuters one after another leaving the escalator to play the piano stairs, and the sight of others joining in drew still more to try.
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Whopper SacrificeBurger King2009
Whopper Sacrifice
Told every dropped friend they had been sacrificed for a Whopper, so each private click became a public notice that drew more people in to try it.
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2009Dance (Life's for Sharing)
One commuter starts to dance and some 350 more join in, and watching a crowd fall into step makes viewers want to be part of it.
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2009Singles' Day (11.11)
Publishing ever-larger totals, up to 268.4 billion yuan in 24 hours by 2019, told shoppers that everyone else was buying, which pulled more in each year.
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2007Pinkie ("Speeding. No One Thinks Big of You.")
Shows everyone a young driver hopes to impress, from young women to an elderly woman to his own mates, giving the same verdict, and the gesture spread to real life.
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UniqlockUniqlo2007
Uniqlock
A world map on the site showed the clock spreading from blog to blog, and seeing so many others carry it made one more blogger want to.
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2007Earth Hour
Lets people watch the Opera House and Harbour Bridge go dark alongside 2.2 million others, and each year's bigger crowd drew in the next.
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2005Crossbar ("Ronaldinho: Touch of Gold")
Looks like the homemade clips people swapped by email, so it travelled from inbox to inbox as something worth passing on, becoming YouTube's first million-view video.
1980s
1970s
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1975The Pepsi Challenge
Shows Coke drinkers themselves choosing Pepsi on camera, and seeing people just like you switch makes switching feel safe.
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Kurisumasu ni wa Kentakkii (Kentucky for Christmas)KFC Japan1974
Kentucky for Christmas
With an estimated 3.6 million families eating KFC at Christmas, many ordering weeks ahead, the crowd itself told everyone else this was how the holiday is done.
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1972Three Brothers ("Mikey Likes It")
Lets a little brother who hates everything be the taster, and kids trusted a sibling's verdict on a healthy cereal far more than any adult claim.
1960s
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Legoland BillundLEGO1968
Legoland Billund
Grew from crowds of 20,000 a year already turning up at the factory, and a park drawing 625,000 in its first season showed families this was the place to go.
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You don't have to be Jewish to love Levy's.Levy's (Henry S. Levy & Sons)1961
You Don't Have to Be Jewish to Love Levy's
Shows a railroad engineer, a restaurant worker and a boy from Harlem biting into Levy's rye, so New Yorkers of every background saw someone like them enjoying it.
1950s
1930s
1910s
1890s
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1893Divan Japonais
Sells the café by its crowd, seating the dancer Jane Avril and the critic Édouard Dujardin in the audience, so it looks like the place stylish Paris goes.
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The Pickle PinHeinz1893
The Pickle Pin
Crowds big enough to make the floor sag drew still more people upstairs, and every charm worn home showed others that the Heinz booth was the place to go.
Social proof: where it comes from
When a few people stood on a New York pavement staring up at a building, passers-by stopped and looked up too, and the bigger the group, the more people joined in (Milgram, Bickman and Berkowitz, 1969). Robert Cialdini named the tendency social proof.
In ads it shows up as crowds, queues, best-seller claims, sales figures and anything people share for others to see.