Behavioral economics & viral marketing case studies
Fresh Start Effect 
Details
Fresh Start Effect means people are more likely to take action toward a goal when they hit a time point that feels like a new beginning - a new week, month, birthday, or milestone. New beginnings make change feel easier.
Think of how people suddenly start diets or gym plans on January 1st, even though it’s just another day. The “new year” frame creates a mental reset that boosts motivation.
In marketing this bias powers campaigns tied to new cycles: season resets, calendar dates, onboarding milestones, or “start over” moments. When something feels like a fresh chapter, people lean in.
Fresh Start Effect 
Guide
Fresh Start Effect 
Research
Researchers studied millions of real-life behaviours like gym check-ins from 11,000+ students, Google search data, and activity on a big goal-setting website. They wanted to see how much different “fresh starts” (new week, new month, birthdays, New Year) change people’s motivation.
Here are the exact effects they found:
Fresh Start Effect 
Examples
1. Casinos - "new shoe shuffle"
Blackjack tables use a shoe shuffle every time the deck runs out - dealers announce it loudly: “New shoe!” Even losing players suddenly feel like they’re starting fresh.
Libraries run amnesty months where all late fees are forgiven. People who avoided the library out of shame suddenly return because the slate is wiped clean. Participation skyrockets because Fresh Start removes embarrassment and guilt.
When a guest complains, many hotels offer a room change, even if the new room is almost identical. The change creates a psychological reset “okay, this stay is starting over. Maybe it will be good now.” This Fresh Start removes negative emotions and prevents refunds or bad reviews.
Life Event Effect Details
Life Event Effect means that people are more likely to switch habits and brands when they have undergone a life event. Changes like moving, having a child, starting a new job, or a breakup make old habits break.
Think of someone who just moved to a new city. They suddenly choose new brands, new routines, and new services , not because the products changed, but because their life context did.
In marketing this bias explains why timing matters so much. Brands that show up during life changes get a rare chance to form new habits.
Life Event Effect Guide
Life Event Effect Research
About 34% of US soldiers used heroin while fighting in Vietnam, and around 20% showed signs of addiction. After a major life change (coming back home) this behavior dropped fast.
In the first year after returning to the US, only about 1% became addicted again, even though 10% tried the drug again after returning.
This shows that when life context changes, behavior can change suddenly, even without treatment.
During research, researchers ran a survey among 2,370 people. They asked two things:
Overall, 21% of people who had a recent life event had switched brands, vs 8% of regular consumers (≈2.6X higher). And in 3 categories, life-event consumers were more than 3X more likely to have switched brands.
People whose age ends in “9” (eg, 29, 39, 49) are more likely to question the meaningfulness of their lives than people at other ages.
In their study, researchers examined the ages of first-time marathon runners and found that 9-enders were overrepresented by ~48% among participants aged 25-64.
Nine-enders were also more represented on an extramarital affairs site (men with ages ending in 9 were ~18% overrepresented).
This explains the whole idea of a midlife crisis.
Life Event Effect Examples
1. Starting new job - LinkedIn Premium, Notion, Slack
A new job resets tools, routines, and identity. LinkedIn usage spikes when people start searching for a new job. LinkedIn Premium converts best when users change job titles. Notion and Slack get adopted because teams rebuild workflows from zero.
When people move, they switch internet, furniture, and home services. Comcast and AT&T aggressively target people right after an address change. IKEA wins because moving breaks old habits, and people are open to new brands.
Scarcity Details
Scarcity means we value things more when they feel limited. When supply drops, desire rises, even if nothing else changes.
Think of seeing only a few items left on a shelf. Suddenly the product feels more important, even if you didn’t want it a minute ago. The fear of losing it boosts the urge to act.
In marketing scarcity turns hesitation into action. Limited spots, low stock, and short windows make people move faster because waiting feels risky.
Scarcity Guide
ScarcityResearch
A large meta-analysis of 131 studies and 416 effects found that not all scarcity works the same.
A group of 200 female students rated how attractive cookies were when there were many of them (abundant), when there were few (scarce), and when the amount changed. When cookies became scarce, the students were told it happened either because many people wanted them or because of an accident.
As a result, the cookies were rated more desirable when they were scarce than when they were abundant.
They were also rated more valuable when they changed from abundant to scarce compared to being scarce the whole time.
Scarcity caused by high demand got the highest ratings, while “accidental scarcity” scored lower. And cookies that stayed abundant the whole time were rated higher than cookies that started scarce and later became abundant.
Scarcity Examples
When Snap released Spectacles, you could only buy them from special vending machines called Snapbots. They appeared in random places without warning, so it felt like a surprise game of first come, first served.
This unpredictable availability created strong FOM and as a result, Spectacles became a cult gadget.
MSCHF releases strange products in small, surprise drops. You never know when the next drop comes, and they never restock, so people rush to buy. This makes every product feel rare, special, and worth grabbing fast.
TBH launched only in a few high schools and only in one state at the start, nobody else could download it. This created massive FOMO in nearby schools. Because of that (and many other brilliant aspects), the app was downloaded 5M times within 2 months.
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.
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.
External Trigger Details
External Trigger means something outside of you prompts you to act. It’s a cue you see or hear that pulls your attention and tells your brain what to do next.
Think of hearing your phone ping and instantly checking it. The sound, not your feeling, started the action.
In marketing external triggers guide behavior. Notifications, ads, emails, pop-ups, and clear calls-to-action remind people you exist and show them the next step.
External Trigger Guide
External TriggerResearch
Research in behavioral design shows that the very first “nudge” that leads to a habit often comes from outside us (an external cue) rather than just internal feelings.
Nir Eyal notes that in his “Hook Model” framework, triggers are the first step: an external trigger (push notification, email, banner, icon) signals “do this now”. Over time, what begins as external is internalised (i.e., the user starts acting without the push).
Nir Eyal mentions four kinds of external triggers in his book:
External triggers only work when they’re tightly linked to an internal trigger (an emotional itch, boredom, loneliness, uncertainty) and when the user is ready (has ability + motivation). If the external cue hits without the emotional itch/ready state, it fails or feels “spammy”
Companies track how well triggers work by looking at things like CTR and conversions. Push notifications are one of the strongest triggers. Data shows that apps with push switched on keep about 65% of users active after 30 days, while apps without push keep far fewer.
Push also boosts engagement users who get notifications can be up to 88% more active than users who don’t.
External Trigger Examples
1. Duolingo
Duolingo’s owl sends you a daily push that mixes guilt and encouragement. It’s a simple external trigger, but it works. People open the app and keep their daily streak going.
LinkedIn sends external triggers in emails like “5 people viewed your profile - see who!” which lures you back to the platform via curiosity.