Behavioral economics & viral marketing case studies
Underdog Effect 
Details
Underdog Effect means we root for people or brands that seem disadvantaged but still fight hard. It’s about telling a story of a small start, low budget, a big competitor to fight, and steady effort against tough odds. Effort against the odds makes us feel emotionally connected.
Think of a tiny startup showing how they build everything with almost no money while going up against a huge company. Their honesty and effort make you want them to win.
In marketing this bias shapes storytelling, brand positioning, and challenger messaging. When customers see a brand as the scrappy fighter, they support it more actively.
Underdog Effect 
Guide
Underdog Effect 
Research
The researchers found that the Underdog Effect makes people more likely to buy, choose, and stay loyal to a brand.
This effect is even stronger for people who see themselves as underdogs, especially when they are buying something for themselves, not for others. It also works better in countries where underdog stories are an important part of the culture.
Underdog Effect 
Examples
1. Apple's "1984" commercial
In its early days, Apple positioned itself as the underdog against the giant IBM. Their now iconic "1984" commercial, showed a dystopian future dominated by "Big Brother" (IBM), with Apple as the rebellious force breaking the mold. This ad solidified Apple's reputation as the innovative and rebellious alternative to the status quo.
Avis, the car rental company, was always in the shadow of Hertz, who was an industry #1. Avis used this situation to their advantage with their "We Try Harder" campaign. Because they were #2 in the market, they had to put in extra effort to please their customers. This campaign was immensely successful and helped Avis increase its market share.
When a newly-created Instagram account of an egg announced that it wanted to beat Kylie Jenner in terms of the most-liked photo, people responded. A simple egg photo collected over 52M likes within days.
Authenticity Effect Details
Authenticity Effect means we trust and value things that feel real, honest, and unpolished. When something looks too staged or too perfect, our guard goes up.
Think of a founder recording a simple phone video explaining why they started their company. No studio, no script, just a real person talking. It feels more believable than a glossy ad saying the same message.
In marketing this bias shapes brand voice, storytelling, behind-the-scenes content, and honest communication. When people sense genuineness, their trust and loyalty rise fast.
Authenticity Effect Guide
Authenticity Effect Research
The study examined how the value of a sponsored message and the credibility of an influencer shape trust, and how that trust then drives brand awareness and purchase intention.
Researchers surveyed social-media users who follow influencers.
Overall, influencer marketing works best when the content is genuinely helpful and the influencer is seen as credible, because these two factors build trust that leads people toward the brand and toward buying.
Authenticity Effect Examples
1. Liquid Death
Liquid Death sells canned water but uses metal music energy, dark humor, and anti-corporate vibes. Because the tone feels real and not “safe marketing,” people believe the brand more and share it more. Authenticity turned a commodity product (water) into a cult brand worth over $1B.
Nerdy Nuts is a small Peanut Butter, family business that has grown crazy fast due to the quirky product and witty marketing that feels authentic. Customers see the real founders, real kitchen energy, and honest communication, which makes the brand feel trustworthy and human.
This authenticity, combined with weekly product drops and creator partnerships, helped Nerdy Nuts grow from $7k to over $1M in sales within 4 months.
Nostalgia Effect Details
Nostalgia Effect means we respond more strongly to things that remind us of the past. Memories, old styles, and familiar moments create warm feelings that lift our judgment.
Think of hearing a song from your childhood and instantly feeling more positive, even if your day was stressful. The memory colors the moment.
In marketing this bias shapes retro packaging, old-school branding, classic sounds, and “remember when” campaigns. Nostalgia makes products feel safer, warmer, and more meaningful.
Basically, the past makes the present feel better.
Nostalgia Effect Guide
Nostalgia Effect Research
This research ran 6 experiments. In every experiment, nostalgia made people value money less or want money less.
Key findings:
Nostalgia increases social connectedness (people feel closer to others). When this social need is filled, people feel safer and less focused on self-protection or financial security. Because of that, money becomes less important, so they are more willing to spend or give.
When nostalgia is activated (ads, memories, old products, retro style), people spend more easily because they feel emotionally full and less attached to their money.
Nostalgia Effect Examples
1. Pokémon GO
Pokémon GO exploded in 2016 because it brought back childhood memories of collecting creatures. Millions of adults who hadn’t played games in years returned because the app made them feel like kids again. Nostalgia powered record downloads, global crowds, and $500M revenue in the first 60 days.
Stranger Things became a global hit because it recreated the exact look and feel of 1980s movies: neon colors, synth music, walkie-talkies, arcade games, and Spielberg-style adventure.
Adults who grew up in the 80s and 90s felt a strong emotional pull. The show reminded them of childhood summers, old friendships, and classic films. This nostalgia made people binge the series, share it like crazy, and turned a mid-budget show into one of Netflix’s biggest cultural phenomena.
Humor Effect Details
Humor Effect means we remember things better when they make us laugh. A joke, a funny twist, or a light tone sticks in the mind far longer than something serious and flat.
Stories & humor are the ultimate shortcuts to deeper connections and earning trust of your customers. Humor bypasses skepticism.
Think of seeing a billboard with a clever joke. Even if you glance at it for a second, the line stays with you, while dozens of normal ads disappear instantly.
In marketing this bias shapes brand voices, ads, emails, and social posts. Humor boosts attention, recall, and shareability because it gives the brain a little reward for paying attention.
Humor Effect Guide
Humor Effect Research
This meta-research from 1992 reviews dozens of studies on how humor works in advertising.
Humor grabs attention very well but does not always convince people. About 24% of TV ads used humor, and 94% of advertisers said humor is an effective way to get attention, while 55% of research directors said humor works better than non-humor ads for attention.
Humor consistently lifts attention, but its effect on understanding the message is mixed, with:
Humor also does not guarantee stronger persuasion, although one analysis from 1982 found that 31% of humorous ads performed above average in persuasion tests.
The strongest finding in the entire review comes from the role of liking. A large 1991 study with almost 15,000 interviews showed that liking a commercial predicted which ad would win in sales 87% of the time, and a simple like-or-not-like measure predicted success 93% of the time.
People who liked a commercial a lot were also twice as likely to be persuaded. Humor supports this effect because when people felt an ad was funny or clever, it predicted success 53% of the time, while calling an ad boring predicted failure 73% of the time.
Overall, humor is great for getting attention and increasing liking, and since liking is one of the strongest predictors of sales, humor can indirectly make ads more effective, especially when the humor is connected to the product and used for simple, low-involvement decisions.
Humor Effect Examples
Their first ad used deadpan humor, swearing, and absurd scenes to explain a boring product: razor subscriptions. The humor made the message unforgettable, “Our blades are f***ing great.”.
Result: over 12k orders in 48 hours and a company later sold for $1B.
After the 2008 shoe-throwing incident became global meme material, Alex Tew created a funny browser game called Sock and Awe in just 3 hours.
The humor made it instantly shareable. By day 3, it had been played 1.4M times, and by day 6, the site reached 9M visitors.
The game was sold within days, and the team later used the traffic to collect 120k emails, helping them launch their next project (PopJam).
Old Spice used surreal, rapid-fire humor that completely broke deodorant-ad conventions. The absurd style made the brand memorable to both men and women, turning a dying product line into a cultural hit. Sales jumped 125% year-over-year after the campaign.
Curiosity Gap Details
Curiosity Gap means we feel a strong pull to fill in missing information. When we see a hint without the full answer, our brain wants to close the gap.
Think of reading a headline that teases a surprising fact but doesn’t give the full story. You click because the missing piece bothers you just enough to take action.
In marketing this gap drives engagement. Teasers, questions, partial reveals, and open loops make people lean in because they want to know what comes next.
Curiosity Gap Guide
Curiosity Gap Research
In a study from 2007, people chose between a sure thing (cash) and a mystery prize. When the researchers gave them just a little information about the mystery box (not the whole truth), curiosity shot up. People became more than twice as likely to choose the unknown prize instead of the cash. That small tease created a curiosity gap, and the urge to learn the missing info pushed them to take the risk.
A large analysis of 8,977 headline A/B tests found that headlines with an optimal “curiosity gap” achieved the highest CTR.
Upworthy’s data showed that only ~9% of very vague headlines gained clicks by adding info, whereas over 50% of overly detailed headlines actually saw ~5–10% fewer clicks.
This supports Loewenstein’s information-gap theory: headlines that leave readers guessing (not too little, not too much) can boost engagement.
Research on email marketing showed that using curiosity gap can lift open rates. In one study, 33% of recipients opened an email solely due to a compelling, curiosity-inducing subject line. Adding personalization further amplified this effect - personalized, curiosity-gap subject lines saw open rates climb by ~35%.
Curiosity Gap Examples
Ogilvy put a cheap eye-patch on a perfectly normal model wearing Hathaway shirts. This made people instantly curious about the model.
The first ad ran in The New Yorker in 1951. Within a week, every Hathaway shirt in New York was sold out.
In 2004, Heyah flooded cities with a strange red hand logo and a website called “nadchodzi.pl” (“it’s coming”) - but didn’t reveal the brand.
People kept asking “What is this? Who is behind it?” The curiosity gap exploded, driving 1.2M unique visitors before launch.
When the reveal finally came, Heyah got over 300k users within the first month.
Familiarity Bias Details
Familiarity Bias means we trust and prefer things we already know. Familiar options feel safer, easier, and less risky than new ones, even if the new ones might be better.
Think of choosing a brand you’ve bought for years instead of trying a new one with better reviews. The comfort of the known beats the potential of the unknown.
In marketing this bias rewards consistency. Repeated exposure, steady branding, and showing up often make your product feel familiar, and familiarity drives choice.
In other words, we pick what feels known, not always what’s best.
Familiarity Bias Guide
Familiarity Bias Research
The study tested how being familiar with a brand, having previous online-shopping experience, and the amount of product information shown on a website, influence how risky people think online shopping is and whether they intend to buy.
The results:
Familiar brands and previous online shopping experience significantly reduced perceived risk and increased purchase intention. However, surprisingly, the amount of product information provided (lots vs little) did not significantly affect perceived risk or purchase intention.
Familiarity Bias Examples
1. Trello
Trello exploded because it took the Kanban board, a format millions already knew from offices, factories, and whiteboards, and turned it into super simple drag-and-drop software.
GPT-3 was powerful, but almost nobody used it because the interface felt technical and abstract. When OpenAI released ChatGPT with a simple chat-style UI, something everyone already knew from Messenger/WhatsApp, usage exploded within days.
Among Us blew up because its core gameplay was basically the digital version of Mafia/Werewolf/Secret Hitler - games millions already knew from parties.
Spotlight Effect Details
Spotlight Effect means we wildly overestimate how much people notice us. We feel like a spotlight is on us, even when others barely pay attention.
Think of tripping on a sidewalk and instantly assuming everyone saw it and is judging you. In reality, most people didn’t even look up. They’re focused on themselves, not you.
In marketing this bias explains why customers fear making embarrassing choices, posting content, or trying something new. They imagine the whole world is watching when almost no one is.
Spotlight Effect Guide
Spotlight Effect Research
Customers were offered a bottle of water and could pay any amount they wanted. The researchers counted how many people were around each customer and then measured how much each person paid.
When more people were around, customers felt more watched and they paid more.
Average payment was $1.40, and only 15% paid $0.
Feeling watched significantly increased payment and even increased how big the payment was compared to what customers thought the bottle was worth.
People read a scenario about paying what they want in a restaurant. The study tested whether feeling watched changes depending on who is around (family vs coworkers).
People felt most watched when they themselves were paying, and when the people around them were coworkers (not family).
Stronger “spotlight” means higher intended payment. So the effect grows when we’re around people whose opinions matter more to our image.
The last study tested whether giving customers a reference price (“this meal normally costs $120”) changes the spotlight effect.
The spotlight was still there. People who felt watched planned to pay more. But when a normal price was shown, the spotlight became weaker. A fixed price anchors people, so feeling watched has less influence.
A British university coffee lounge hung an image of a pair of eyes on contributions to an honesty box that collected money for drinks.
The image of eyes primed people to pay nearly 3 times more for their drinks than they would have without the image.
Spotlight Effect Examples
Japanese women avoided big burgers because they feared looking rude with a wide-open mouth. Freshness Burger created a wrapper that covered the mouth while eating, so nobody could see the “embarrassing moment.” This small fix removed social anxiety and boosted Classic Burger sales by +213% in one month.
Small 777 slot rooms often cover their windows so no one outside can see who is playing inside. Many people feel embarrassed to be seen gambling and think others will judge them. When players feel hidden, they enter more easily and stay longer because the fear of being watched disappears.
Motivating-Uncertainty Effect Details
Motivating-Uncertainty Effect means not knowing the exact reward can make us work harder than when the reward is guaranteed. The mystery creates excitement and keeps the brain engaged.
Think of doing extra tasks in a game just for a chance at a mystery box. You don’t know what’s inside, but the uncertainty makes the effort feel more fun and energizing than a fixed prize.
In marketing, this means surprise bonuses, mystery gifts, and unpredictable wins keep people coming back because the next reward might be even better.
The key difference from a Variable-Ratio Schedule is that motivating-uncertainty focuses on the mystery of the reward itself, while variable-ratio is about unpredictability in when the reward appears.
Motivating-Uncertainty Effect Guide
Motivating-Uncertainty Effect Research
Research that studied monetary prizes in two situations - when the prize is unknown and can vary from small to very large, and when the prize is a known amount– showed that people were much more likely to be stimulated by the unknown. The summary was that people were more motivated by tasks with an unknown reward:
People had to drink a big amount of water in 2 minutes.
Results:
That’s a 63% boost just because the reward was uncertain.
Mystery discounts beat normal discounts. Brands like GAP and Banana Republic send emails saying “Click to see your secret discount – maybe 15%, 30%, or even 50%.”
Shoppers were more likely to buy when there was a 10% chance the item was free than when everyone got a guaranteed 10% off.
Supermarkets saw the same thing. Customers preferred a “1% chance your whole cart is free” lottery over a normal 1% discount.
Motivating-Uncertainty EffectExamples
1. Loot boxes
Instead of giving players a guaranteed prize for a challenge, games often give a loot box with random items. Players end up playing more and even paying money for these boxes, chasing the excitement of a rare find.
Every time you buy certain items, you peel a sticker, and you don’t know if it’s a free fries, a drink, a rare piece, or a big prize.
Most prizes are tiny, but the uncertainty is what drives the motivation. People buy more meals because each peel feels like a small gamble with suspense, even if the expected reward is low.
Variable-Ratio Schedule Details
Variable-Ratio Schedule means rewards appear after an unpredictable number of actions. The uncertainty keeps the brain hooked because the next win could happen at any moment.
Think of pulling a slot machine lever. You might win on the third pull, the tenth, or the fiftieth. The randomness makes you keep going, chasing the next hit.
Apps, games, and loyalty systems use unpredictable rewards to keep people checking, tapping, and returning more often.
It differs from the Motivating-Uncertainty Effect because this one is about ongoing random rewards, while the other is about one single unknown prize that motivates effort.
Variable-Ratio Schedule Guide
Variable-Ratio ScheduleResearch
This idea comes from B.F. Skinner’s experiments. He learned that pigeons peck a button way faster when the reward comes at random times. In one study, every bird pecked more under a variable-ratio schedule, even though they actually got fewer treats than birds on a predictable schedule. So the pigeons worked harder for random rewards than for regular, more frequent ones.
The study showed how different reward schedules affected exercise in boys. The boys cycled and earned points for their performance, which they could trade for different rewards.
The findings showed that the Variable-Ratio Schedule rewards made boys cycle longer and more often.
Variable-Ratio Schedule Examples
1. Gambling
Casinos are the textbook example. Every element of slot machines, roulette, lotteries is a variable-ratio reward system. A slot machine might on average pay out 1 in 100 pulls, but the player doesn’t know when those 1 will occur - it could be on the 2nd pull, then not again for 180 pulls, etc. This uncertainty leads gamblers to sit for hours feeding the machine.
The act of refreshing your feed is reinforced variably – occasionally you see a post that really interests or rewards you (a friend tagged you, or a hilarious meme), which encourages you to keep scrolling. That’s why you can scroll indefinitely; the next scroll could surface something amazing. This has been explicitly likened to a slot machine by tech designers
Sensory Appeal Details
Sensory Appeal means we pay more attention to things that wake up our senses. When something looks better, sounds clearer, feels smoother, or smells richer, it becomes more memorable and more tempting.
Think of walking past a bakery and catching the smell of fresh bread. You weren’t hungry a minute ago, but that scent pulls you in faster than any ad ever could.
In marketing sensory cues make products feel more real and more desirable.
Sensory Appeal Guide
Sensory AppealResearch
Researchers tested how scent changes buying behavior by putting identical Nike shoes in two rooms. One smelled like flowers, one had no scent.
People were 84% more likely to choose the scented-room shoes. This study helped spark today’s $200M scent-marketing industry.
The 2019 Mood Media study showed that turning on music, screens, and scent in an INTERSPORT store boosted sales by 10%. Shoppers also stayed longer 13.4 minutes vs. 7.9 minutes with everything turned off.
Adding scent in the “Football Zone” raised positive feelings by 28% and increased sales by 26%. Letting people touch products lifted emotional response by 50%, and 56% of shoppers said touch is the biggest reason they buy in-store.
Holding an item makes people up to 48% more likely to choose it or choose another product with the same shape/size.
People were 48% more likely to pick a chocolate when its shape matched the object they were already holding.
People were 39.9% more likely to choose a Fanta when they were holding a can or a bottle shaped like it.
The effect became up to 208% stronger when products were packed tightly together on crowded shelves, because touch helped people process them faster.
BIT (Behavioral Insights Team) wanted to influence meat-eaters to choose vegetarian food instead.
They only added a few words, such as:
Results? Sales of vegetarian options increased by up to 70%!
Sensory Appeal Examples
1. Starbucks
Starbucks is famous for its in-store aroma – they intentionally grind coffee throughout the day because the rich coffee smell entices people inside and makes the experience cozy.
Singapore Airlines even made its own cabin scent “Stefan Floridian Waters” so passengers instantly feel “this is Singapore Airlines.”