(Behavioural Science) 50 principles for behavior nudge
50 behavioral and cognitive science nudge principles — filterable and searchable reference
The six categories:
Cognitive biases (9 principles) — systematic errors in thinking that affect judgment: anchoring, availability heuristic, confirmation bias, and others that subtly warp how we evaluate information.
Social influence (9 principles) — how other people shape our choices: social proof, authority, reciprocity, liking, and norm activation all tap into our deeply social nature.
Framing (10 principles) — how the same information, presented differently, changes decisions: from the framing effect itself to salience, priming, scarcity, and the peak-end rule.
Loss/Risk (7 principles) — our asymmetric relationship with potential losses: loss aversion, sunk cost, regret aversion, omission bias, and related phenomena that make losses sting more than gains feel good.
Choice architecture (7 principles) — how the structure of choices drives outcomes: defaults, decoy effects, paradox of choice, friction reduction, and pre-commitment all operate at the decision environment level rather than persuasion.
Habit formation (8 principles) — the mechanics of building durable behavior: implementation intentions, temptation bundling, identity-based habits, habit stacking, and fresh starts.
Social proof
People look to others' behavior to guide their own, especially in uncertain situations.
Example: '9 out of 10 customers also bought this' or hotel towel reuse signs showing neighbor behavior.
Anchoring effect
The first number or piece of information encountered disproportionately influences subsequent judgments.
Example: A $999 item next to a $4,999 item feels like a bargain, even if $999 is expensive on its own.
Loss aversion
Losses feel roughly twice as painful as equivalent gains feel pleasurable.
Example: 'Don't miss out on your savings' outperforms 'Earn more savings' in motivating action.
Default effect
People tend to stick with pre-selected options, making defaults enormously powerful.
Example: Opt-out organ donation systems dramatically increase donor rates vs. opt-in systems.
Status quo bias
People prefer the current state of affairs and resist change, even when alternatives are better.
Example: Employees rarely change their 401k allocation once set at enrollment.
Framing effect
The same information presented differently leads to different decisions.
Example: '95% survival rate' vs. '5% mortality rate' produce different surgery acceptance rates.
Reciprocity
People feel obligated to return favors or gifts, creating a powerful social pressure.
Example: Free samples at grocery stores reliably increase purchases of that product.
Availability heuristic
People overweight information that comes to mind easily, often due to recency or vividness.
Example: Lottery ticket sales spike after publicized jackpot winners, despite unchanged odds.
Implementation intentions
Forming 'if-then' plans dramatically increases follow-through on intentions.
Example: 'I will exercise at 7am Monday in the gym' leads to far higher adherence than 'I'll exercise more.'
Choice overload
Too many options causes decision paralysis and reduced satisfaction with choices made.
Confirmation bias
People seek, interpret, and remember information that confirms their existing beliefs.
Authority bias
People give extra weight to the opinions and instructions of perceived authority figures.
Priming
Exposure to one stimulus influences the response to a later stimulus, often unconsciously.
Example: Showing images of money before a task makes people more self-reliant and less cooperative.
Commitment devices
Voluntarily restricting future choices to lock in better behavior in advance.
Example: Putting savings into a separate account you can't easily touch removes temptation at the moment.
Sunk cost fallacy
People continue investments (money, time, effort) because of past costs, not future value.
Example: Finishing a bad movie because you already paid $15 for the ticket.
Optimism bias
People systematically overestimate positive outcomes and underestimate risks for themselves.
Example: Most people rate themselves as better-than-average drivers, which is statistically impossible.
Norm activation
Making social norms visible and specific to a reference group powerfully shapes behavior.
Example: 'Most of your neighbors have already paid their taxes on time' increases on-time filing.
Salience
Information that stands out or is made vivid is weighted more heavily in decisions.
Example: Traffic light nutrition labels draw attention to unhealthy items, reducing their purchase.
Temptation bundling
Pairing a desired activity with an obligation makes both more appealing.
Example: Only listening to a favorite podcast while exercising makes gym visits feel rewarding.
Decoy effect
Adding an inferior third option makes one of the original two options seem clearly superior.
Example: A medium soda at $2 vs. small at $1 vs. large at $2.10 makes the large seem like a great deal.
Planning fallacy
People underestimate how long tasks will take, even when they have past evidence of delays.
Example: Construction projects, software launches, and personal projects almost always run over schedule.
Mental accounting
People treat money differently depending on its source or intended use, not just its objective value.
Example: People spend 'windfall' money like a tax refund more freely than the same amount of earned income.
Bandwagon effect
People adopt beliefs or behaviors because they perceive others doing the same.
Example: Crowded restaurants are assumed to be good; popularity itself becomes a quality signal.
Regret aversion
People make decisions to minimize anticipated regret, often avoiding action to dodge blame.
Example: Investors hold losing stocks too long to avoid 'locking in' a loss they'd have to acknowledge.
Habit stacking
Attaching a new behavior to an existing habit makes adoption far more likely.
Example: 'After I pour my morning coffee, I will write one journal entry' leverages an established routine.
Paradox of choice
More freedom of choice can lead to worse outcomes: less satisfaction, more anxiety.
Example: Workers with fewer investment fund options in retirement plans tend to save more and feel better.
Halo effect
A positive impression in one area spills over to unrelated areas of judgment.
Example: Attractive job candidates are rated as more competent, even by trained evaluators.
Contrast effect
Perception of something is influenced by comparison to a recently encountered alternative.
Example: A salary increase feels larger or smaller depending on what comparison salary is shown first.
Social comparison
People assess their own worth and choices relative to peers, driving motivation and envy.
Example: Showing energy usage next to neighbors' usage motivates conservation in high-usage households.
Fresh start effect
People are more likely to pursue goals after temporal landmarks like new years, birthdays, or Mondays.
Example: Gym sign-ups spike sharply on January 1st and after personal milestones.
Risk compensation
People adjust behavior in response to perceived risk, sometimes offsetting safety improvements.
Example: Wearing a helmet may lead some cyclists to ride faster, partly canceling out the protection.
Hyperbolic discounting
People steeply discount future rewards in favor of immediate ones, beyond rational time preference.
Example: People prefer $10 now over $15 next week but prefer $15 in 5 weeks over $10 in 4 weeks.
Scarcity principle
Things perceived as rare or becoming unavailable are valued more highly.
Example: 'Only 3 left in stock' or 'Offer ends tonight' dramatically increases conversion rates.
Descriptive vs. injunctive norms
Injunctive norms (what others approve of) and descriptive norms (what others do) both shape behavior but through different mechanisms.
Example: Combining both — 'Most guests reuse towels and we encourage it' — is more effective than either alone.
Variable reward schedules
Unpredictable rewards create stronger and more persistent behavior than fixed schedules.
Example: Slot machines and social media feeds both use variable rewards to maximize engagement.
Simplification & friction reduction
Reducing the number of steps or cognitive effort required to complete a task dramatically increases uptake.
Example: Auto-enrollment in savings programs raises participation from ~50% to over 90%.
Dunning-Kruger effect
People with limited knowledge overestimate their competence; experts tend to underestimate theirs.
Example: Novice investors often trade more actively and with more confidence than experienced ones.
Peak-end rule
People judge experiences based primarily on how they felt at the peak and at the end, not the average.
Example: A painful medical procedure remembered as less bad if it ends gradually rather than abruptly.
Zero risk bias
People prefer eliminating a small risk entirely over a larger reduction in a bigger risk.
Example: Consumers prefer food with '0g trans fat' over a food with 10% less saturated fat, which is objectively better.
Conformity pressure
People change their expressed opinions or behavior to match the majority, even against their own judgment.
Example: In Asch's line experiments, people agree with obviously wrong answers when a group unanimously gives them.
Identity-based habits
Framing behavior change as an expression of identity ('I am a runner') is more durable than outcome goals.
Example: People who define themselves as non-smokers rather than people 'trying to quit' have higher long-term success.
Feedback loops
Immediate, clear feedback on behavior drives faster learning and adjustment.
Example: Real-time energy monitors showing cost-per-hour cause households to reduce consumption on the spot.
Attribution bias
People attribute their successes to internal factors and their failures to external ones.
Example: Managers rate their team's success as reflecting their leadership but blame external factors for failures.
Endowment effect
People assign more value to things simply because they own them.
Example: People demand more to sell a mug they were given than they'd pay to buy the same mug.
Liking principle
People are more easily influenced by people they like — due to similarity, familiarity, or attractiveness.
Example: Referral programs work because recommendations from a friend carry far more weight than ads.
Omission bias
People judge harmful actions as worse than equally harmful inactions, preferring inaction even when action is better.
Example: Parents hesitate to vaccinate partly because a vaccine-caused harm feels more blameworthy than disease-caused harm.
Reward substitution
Replacing a future reward with an immediate one to bridge the motivational gap.
Example: Using a 'don't break the chain' calendar to make daily habit progress immediately satisfying.
Pre-commitment
Making a decision in advance, before temptation arises, dramatically improves follow-through.
Example: Odysseus ordering himself tied to the mast — or pre-ordering a salad before arriving at a restaurant.
Illusion of control
People believe they have more influence over outcomes than they actually do.
Example: Lottery players prefer to choose their own numbers, believing it improves their chances.
Message format & timing
When and how a message is delivered — not just its content — determines whether it changes behavior.
Example: A text reminder sent the day before a flu shot appointment doubles attendance vs. no reminder.
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