Behavioral economics & viral marketing case studies
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.
Internal Trigger Details
Internal Trigger means a feeling inside us pushes us to take action. It comes from emotions like boredom, stress, loneliness, or curiosity, not from anything outside.
Think of grabbing your phone without any notification. You acted because you felt bored or restless for a moment. The emotion was the trigger.
In marketing internal triggers shape habits. When a product fits a recurring feeling, people return on their own without reminders or ads.
Internal Trigger Guide
Internal Trigger Research
Behavioral psychology shows that around 90% of the time we get distracted or engage in a habit, it’s due to internal triggers (feelings) rather than external prompt.
Nir Eyal notes that studies found people blame their phone notifications for distraction, but actually most device-checking is self-initiated because of an internal urge.
One research finding is that when people are bored, they reflexively reach for their phones to fill that void. Tech companies are aware of this: we’ve seen product metrics indicating peak engagement at times people are likely bored or lonely, like late evening scrolls, Monday morning commutes,
Internal Trigger Examples
1. Snickers
Snickers’ “You’re not you when you’re hungry” campaign essentially tried to establish hunger (and the irritability it causes) as an internal trigger to buy Snickers. They humorously pointed out that emotional state and linked their product as the solution.
Claude Hopkins told people there’s a thin film on their teeth and made them check it with their tongue. That little feeling became the internal trigger.
Whenever someone noticed that film, they automatically thought about brushing with Pepsodent.
Within a few years, daily brushing exploded across the country - from 7% to 65%.
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.
Pareto Principle Details
Pareto Principle means a small part of your effort creates most of your results. Roughly 20% of actions drive about 80% of the outcome.
Think of cleaning your house and noticing that a few quick tasks instantly make the whole place look better. A small part of the work delivers most of the impact.
In marketing a few top channels, a few key messages, or a few loyal customers usually generate most of the growth.
Pareto Principle Guide
Pareto PrincipleResearch
A 2024 Google analysis showed that Pareto still holds. Most revenue comes from a small group of high-value customers.
One retailer focused on those customers and grew CLV (Customer Lifetime Value) by 310% while cutting acquisition costs by 20%. The exact split varies (70/30, 90/10), but the pattern is the same; results are uneven.
The takeaway is to find the small group driving most of your impact and double down.
Pareto Principle Examples
1. Amazon
Amazon used the 20% bestsellers to bring in most traffic, while still making money from the long tail.
Spotify sees that a tiny group of artists drives most of the streams, so they push those top 1-2% even harder in playlists and recommendations.
Mere Exposure Effect Details
Mere Exposure Effect means the more we see something, the more we start to like it. Familiar things feel safer and easier for the brain to process.
Think of hearing a song you didn’t care about at first but after a week of hearing it everywhere, it suddenly feels good. Repetition made it feel familiar, and familiar feels right.
In marketing, showing up often makes your brand seem more trustworthy, more likable, and more natural to choose. Even small repeated touches shift people toward you.
Mere Exposure Effect Guide
Mere Exposure Effect Research
Psychologist Robert Zajonc found in 1968 that the more people see something, even nonsense words or random symbols the more they like it. People don’t even need to remember seeing it.
Later studies confirmed it. When people saw certain Chinese characters a few times, they were more likely to say those characters meant something “good” compared to characters they saw only once.
College students read an article while banner ads changed every 5 seconds. One group occasionally saw a fake digital-camera ad, the control group didn’t.
Those who saw the repeated ad rated the brand much more positively, even though none of them remembered seeing it. Even after 20 exposures, there was no wear-out. Students didn’t get annoyed or tired of the banner.
Mere Exposure Effect Examples
1. Logo & names everywhere
Big brands blast their logo across billboards, events, and random places, not to hard-sell you, but to feel familiar.
Even if you haven’t had one in months, constant logo sightings make it the “safe” pick when you’re thirsty.
Startups use the same trick with display ads and billboards so later, when a targeted ad shows up, you think, “Oh yeah, I know these guys.”
Hearing jingles & slogans like “I’m lovin’ it” for a thousandth time wires those brands' message into your head. Radio and TV rely on this, repeating a catchy line enough and it becomes a positive, top-of-mind anchor.
Political campaigns rely on the same effect. Yard signs and posters don’t tell you anything about policy, they just make the candidate’s name feel familiar. And in low-information elections, that alone can swing votes. It’s not love, it’s simple comfort with a name you’ve seen a lot.
Nickelback became one of the most universally hated bands in the world because people were forced to hear their music everywhere, especially “How You Remind Me,” which played over 1.2M times on US radio in the 2000s.
To put that into perspective:
"In 2002, there was never a second on American radio that How You Remind Me wasn't being played on any one station in the United States."
Normally, hearing something many times makes you like it more, but when it’s too frequent and not your choice, the effect flips, and people get irritated.
In 2003, comedian Brian Posehn joked “Nickelback makes me want to kill Nickelback,” and Comedy Central ran this line in promos for 6 months.
Kids repeated the joke (mere exposure effect kicked the other way round now), and it spread like a meme. People mocked the band even if they didn’t know their music. Internet culture in the late 2000s/early 2010s amplified it with endless Nickelback memes.
The combo of massive forced exposure + a viral joke turned mild annoyance into worldwide hate.