Behavioral economics & viral marketing case studies
Commitment & Consistency 
Details
Commitment & Consistency Bias means once we commit to something, even in a small way, we feel the need to stay consistent with that choice. Changing course feels uncomfortable.
Think of agreeing to go to a Thursday 6 PM training session with a friend. After showing up once, you feel pushed to keep going every Thursday, not because the workout changed, but because you already committed to that specific slot and want to stay consistent with it.
In marketing this bias powers small onboarding steps, micro-commitments, quizzes, and simple one-click starts. Once people take the first step, they naturally follow through.
Commitment & Consistency
Guide
Commitment & Consistency
Research
In the study from 1966, the researchers asked women to do a small favor - answer a few questions about the cleaning products they used. It was an easy, non-invasive request.
Three days later, the same women received a much bigger request - they were asked to let researchers into their homes for about 2 hours to check all their household products.
The result:
This well-known example, often mentioned by Robert Cialdini, tested how a tiny change in wording could reduce restaurant no-shows.
That small shift, from giving an instruction to getting a simple verbal promise, cut no-shows from 30% to 10%. It showed how even a tiny commitment makes people much more likely to follow through.
Commitment & Consistency
Examples
1. Audible
Audible forces you to pick your first audiobook the moment you join. Once you choose a book, you psychologically commit to listening. This simple step massively boosts first-month retention.
When you click “Save for later,” Amazon treats this as a micro-commitment. You feel like you’ve chosen the item mentally, so buying it later feels consistent with your previous decision. This is why Amazon keeps those items visible forever - you already committed once.
Sunk Cost Effect Details
Sunk Cost Effect means we keep investing time, money, or energy into something just because we’ve already put a lot into it, even when quitting would be smarter. The past effort traps us.
Think of staying in a bad project just because you spent months on it, even though it doesn't earn any money. Or you're stuck in a bad relationship even though you don't love the other person anymore. The time you already invested pulls you in, not the actual value.
In marketing this effect keeps customers subscribed, committed, or loyal to things they’ve already paid for or spent effort on. The more they’ve put in, the harder it feels to walk away.
Sunk Cost Effect Guide
Sunk Cost Effect Research
In a 1985 study by Arkes and Blumer, people got theatre tickets at different prices:
54 people who paid more for a theater season pass ended up going to more shows over 6 months, just to use their pricey ticket. The cheaper the ticket, the less likely people were to use it.
Sunk Cost Effect Examples
1. Starbucks rewards
Starbucks gives you points that expire. When you have something like 70/100, you don’t want that effort to go to waste. So you buy another coffee or two just to “finish the set.” The more points you’ve collected, the stronger the pull.
People spend thousands on the Peloton bike. After that, they feel they must keep the monthly subscription active, or else that big investment feels wasted. The high upfront cost keeps them inside the system much longer.
Cognitive Dissonance Details
Cognitive Dissonance means we feel uncomfortable when we hold two conflicting beliefs or our actions and beliefs don’t match. The mind hates this tension and tries to reduce it fast.
Think of someone who buys an expensive product they don’t really need. To ease the discomfort, they start convincing themselves it was a smart decision, even if it wasn’t. The story changes to fit the action.
In marketing this effect shows why people justify purchases, ignore flaws, or defend brands they’ve already chosen. Once they commit, they shape their beliefs to feel consistent.
Cognitive Dissonance Guide
Cognitive Dissonance Research
Classic studies showed that after making a choice, people often increase their positive feelings for the chosen option and diminish their liking for the option they rejected.
In one study, shoppers were asked to rank household items and then choose one to keep. Later, they ranked the items again - and lo and behold, the item they chose climbed higher in attractiveness while the one they passed up fell in their ratings.
Lipponen looked at many older studies to see what people do when they feel unsure after buying something. The research he reviewed showed the same pattern: after a purchase, people try to remove the uncomfortable feeling by:
The final result is that customers use predictable, repeated behaviours to calm down their “did I choose right?” feeling.
Cognitive Dissonance Examples
1. Amazon reviews
After buying something online, people often feel a small worry that they may have picked the wrong product. Amazon reduces this discomfort by showing tons of reviews, star ratings, customer photos, Q&A sections, and the Amazon’s Choice badge.
Seeing that many other people bought and liked the item calms the brain and removes that uneasy feeling after purchasing.
Confirmation Bias Details
Confirmation Bias means we pay more attention to information that supports what we already believe and ignore anything that challenges it. Our brain prefers comfort over correction.
Think of someone who loves a brand and only notices positive reviews while brushing off the negative ones. They’re not seeing the whole picture, just the parts that fit their belief.
In marketing this bias shapes how people read ads, reviews, and claims. If your message aligns with what they already think or want, they accept it quickly. If it clashes, they tune it out.
In other words, we look for proof that we’re already right.
Confirmation Bias Guide
Confirmation BiasResearch
In a classic confirmation bias experiment, people who strongly supported or opposed the death penalty were shown two studies:
Instead of becoming more open-minded, each group became even more convinced they were right. Supporters praised the study that backed their view and tore apart the one that didn’t. Opponents did the exact same in reverse. Everyone rated the study that matched their belief as “strong” and the other as “weak.”
In the end, both sides became more polarized, proving we naturally look for info that confirms what we already believe and attack anything that challenges it.
Confirmation Bias Examples
1. New Coke
Coke tried to replace its classic formula in 1985 after blind tests said people liked the sweeter New Coke more. But loyal Coke fans already knew the original was the best. Confirmation bias kicked in hard. They rejected the new flavor, hunted for reasons it was bad, and organized protests. Taste didn’t matter, their belief did. Within months, Coke was forced to bring back the original.
Shopify fills its homepage with success stories of brands that scaled using Shopify.
If you come in already thinking “Shopify is good for growth,” these stories confirm it.
Your brain sees only evidence that matches your belief.
Doubts go down, trust goes up, conversion goes up.
Endowment Effect Details
Endowment Effect means we value things more simply because we own them. Once something feels like ours, its worth rises in our mind.
Think of trying to sell an old item you barely use and being shocked that others won’t pay the price you think it deserves. You see more value in it because it’s yours.
In marketing this effect makes trials, personalization, and early ownership work.
Endowment Effect Guide
Endowment Effect Research
Researchers gave one group of people a coffee mug and asked how much they’d sell it for, and asked another group how much they’d pay for the same mug.
Sellers asked for $7.12, while buyers were only willing to pay $2.87. Sellers were willing to pay almost 2.5X more for the mug! Same mug, same quality, but owning it made people value it more.
Endowment Effect Examples
1. Amazon Prime
That's how Amazon’s 30-day free Prime trial works. Once you’ve experienced free shipping on every order and started relying on it, you feel like Prime membership is something you have, and letting it lapse feels like losing a benefit you own
IQOS used the endowment effect with free 30-day trials.
You don’t just hear about the product – you own it for a month. You get used to less smell, the “healthier” feeling, the new routine. After 30 days, giving it back feels like a loss, so you’re more likely to keep (and buy) it.
They even swapped tests for your pack of cigarettes or lighter, nudging you to “trade in” the old habit for the new one.
Peak-End Rule Details
Peak-End Rule means we judge an experience mostly by its best or worst moment and how it ended, not by the whole thing. The highlights shape the memory.
Think of a long trip with some boring parts, but one amazing moment and a smooth trip home. You remember it as great because the peak and the ending were strong.
In marketing this rule shapes how people recall brands. A single standout moment and a clean, positive finish can outweigh a dozen average interactions.
Peak-End Rule Guide
Peak-End Rule Research
In this study, participants did two uncomfortable tasks.
Objectively, Trial B was longer and caused more total pain.
But after doing both, participants were asked which trial they would choose to repeat.
65% chose the longer and objectively worse trial B.
Since Trial B ended with slightly less pain, the whole experience felt better in memory.
Peak-End Rule Examples
1. Eleven Madison Park
Eleven Madison Park is the restaurant behind Unreasonable Hospitality book, and often called the best in the world. A lot of scenes you see in The Bear series are also inspired by this place.
They always create at least one big “wow moment” for each guest, usually a small surprise or a personal touch. They focus on ending strong too, like giving a final glass of wine or whisky and saying a warm goodbye.
The Magic Castle is the second-best hotel in Los Angeles by TripAdvisor. It focuses on one or two outstanding moments - the popsicle helpline.
Any time, day or night, you can pick up the old-fashioned red phone by the pool and dial the helpline. A man, complete with white gloves, promptly appears bearing a silver platter with a selection of free ice-lollies.
Loss Aversion Details
Loss Aversion means losing something feels much worse than gaining the same thing. Our brains treat losses as threats, so we react stronger to the idea of losing than to the idea of winning.
Think of finding $100 on the street versus losing $100 from your wallet. The pain of the loss hits much harder than the joy of the gain, even though the amount is the same.
People protect what they already have, so messages about losing access, missing benefits, or giving up results work better than promises of new perks.
Loss Aversion Guide
Loss Aversion Research
Researchers tested 4 short messages on a real e-commerce site to see how they change what people do. Each message used a different bias: countdown, social proof, loss aversion, or gain frame. They measured pageviews, time on page, and conversions.
Countdown (“Order in X minutes for fast delivery”)
Bandwagon (“100+ people ordered this”)
Loss Aversion (“This meal is almost gone, don’t miss it”)
Gain Frame (“Order faster, get it faster”)
All messages made people browse more, but only the loss-aversion message increased buying (+23% vs control).
Winning $100 feels good, but losing $100 hurts roughly 2X more, confirmed in many studies.
Loss Aversion Examples
1. Email marketing & cart abandonment
Use subject lines that focus on what people might lose, “don’t lose your 20% off” or “your cart is about to expire.”
Sellers usually push these by highlighting what you could lose. Instead of “get peace of mind with a warranty,” they say “without it, one repair could cost you $2k.” This taps into our fear of losing money or a working product, and it’s often more convincing.
Many programs give you something first and then warn you that you might lose it. A credit card might give you Gold status for 3 months and say “keep spending to keep it”, so you spend more. Hotels give bonus points that expire soon, so you book a stay to not lose them. Starbucks drops bonus stars in your account and says they’ll vanish, which pushes you to visit.