All 188 biases and effects

Everything on the map, grouped by the problem it helps your brain solve and the shortcut behind it. Pick one for examples and what you can do about it.

Most entries are cognitive biases. Labels mark the memory effects, the logical fallacies, other names for the same thing, and the few that aren't biases at all.

Explore them on the interactive map 8 habits that catch most of them

Too Much Information

Far more reaches your senses than you could ever process. Your brain filters hard. It keeps what is repeated, surprising, changed, or already believed, and drops the rest.

Primed & repeated · 12 biasesWe notice things already primed in memory or repeated often

We take in far more than we can handle, so the brain uses what is already active in memory as a filter. Things we met recently, often, or with strong feeling are likely to matter again, so pushing them forward saves time and effort.

Availability heuristicA mental shortcut where we judge how common or likely something is by how easily examples come to mind. Recent, vivid, or emotional events feel more frequent than they really are.
Attentional biasThe tendency for our attention to be pulled toward things tied to our current worries, desires, or habits, while other information goes unnoticed. What we attend to then shapes what we believe and decide.
Illusory truth effectThe tendency to believe a statement is true after hearing it several times. Repetition makes a claim feel familiar and easy to process, and that ease gets mistaken for accuracy.
Mere exposure effectThe tendency to like things more simply because we have encountered them before. Repeated contact makes something feel safe and pleasant, even without any new information about it.
Context effectmemoryOur surroundings shape how we perceive and remember things. The same item can look, taste, or feel different in a different setting, and memories formed in one place can be harder to recall in another.
Cue-dependent forgettingmemoryA type of forgetting where a memory is still stored but can't be reached because the cues present when it was formed are missing. The right hint, smell, place, or word can bring it back suddenly. It is a feature of memory more than a bias, but it makes us think we have lost things we still know.
Mood-congruent memory biasThe tendency to recall memories that match how we feel right now. When we feel happy we more easily remember happy events, and when we feel low we more easily remember sad or painful ones.
Frequency illusionAfter noticing something for the first time, we start seeing it everywhere and assume it has become more common. Usually our attention has simply become tuned to it. It is also called the Baader-Meinhof phenomenon.
Baader-Meinhof Phenomenonother nameAnother name for the frequency illusion: the experience of running into something again and again right after you first learn about it. The odd name comes from a newspaper reader who heard of the Baader-Meinhof Group, a West German militant group, twice in one day.
Empathy gapThe tendency to underestimate how much strong states like hunger, tiredness, anger, pain, or desire affect behavior. When we are calm we misjudge how we, or others, will act when those feelings run high, and the same happens in reverse.
Omission biasThe tendency to judge harmful actions as worse than equally harmful failures to act. Harm that follows from doing nothing feels less like our fault, even when the outcome is the same or worse.
Base rate fallacyThe error of ignoring how common something is in general and focusing on specific details about a single case. It is a reasoning fallacy that leads us to overrate vivid details and underrate plain statistics.

Stands out · 6 biasesBizarre, funny, visually-striking, or anthropomorphic things stick out more than non-bizarre/unfunny things

Unusual, funny, emotional, or personal things often signal something that matters, such as a threat, an opportunity, or information about ourselves. Giving them extra attention and a stronger place in memory helps us learn fast from rare or important events.

Bizarreness effectmemoryThe tendency to remember strange or absurd material better than ordinary material. The effect shows up mainly when odd items are mixed in among normal ones.
Humor effectmemoryThe tendency to remember funny material better than material that isn't funny. Humor grabs attention and makes us process the information more, so it sticks.
Von Restorff effectmemoryThe tendency to remember the one item that stands out from a group of similar items. Something that differs in color, size, shape, or type is noticed and recalled better than the rest.
Picture superiority effectmemoryThe tendency to remember pictures better than words. One explanation is that an image gets stored both as a picture and as a label, which gives memory two ways to find it.
Self-relevance effectmemoryThe tendency to remember information better when it relates to ourselves. Linking a fact to our own life gives it more meaning and more hooks in memory.
Negativity biasThe tendency for bad things, such as criticism, losses, or danger, to affect us more than good things of equal size. Unpleasant events grab more attention and linger longer in memory.

Change · 8 biasesWe notice when something has changed

Our senses and judgment work by comparison. Noticing differences from a starting point, or from what came just before, is faster and cheaper than measuring things in absolute terms, and changes are often what signal danger or opportunity.

AnchoringThe tendency to rely too heavily on the first number or piece of information we see when making a judgment. Later estimates stay too close to that starting point, even when it is arbitrary.
ConservatismThe tendency to revise our beliefs too little when we get new evidence. We favor our earlier view and adjust it only slightly, even when the new information should change it a lot. The term has nothing to do with politics.
Contrast effectThe tendency to judge something as better or worse than it is because we just compared it to something very different. The comparison shifts our sense of size, price, quality, or appeal.
Distinction biasThe tendency to see two options as more different when we look at them side by side than when we experience them one at a time. Small differences that seem huge in comparison often don't matter in daily life.
Focusing effectThe tendency to give too much weight to one feature of an event or choice when predicting how it will turn out or how happy it will make us. Everything else that matters fades from view.
Framing effectThe tendency to make different choices based on how the same information is presented, for example as a gain or as a loss. The facts stay the same, only the wording changes.
Money illusionThe tendency to think about money in terms of the number on it while forgetting what it can actually buy. We overlook inflation and feel richer when we get more dollars, even if prices have risen faster.
Weber-Fechner lawnot a biasA law of perception stating that we notice changes in proportion to the starting amount. A small change stands out against a small amount but disappears against a large one, and this shapes how we judge money and numbers too.

Confirms beliefs · 13 biasesWe are drawn to details that confirm our own existing beliefs

Holding steady beliefs lets us act without rethinking everything each time. Favoring information that fits what we already know is fast, protects our sense of being right, and keeps our picture of the world stable and coherent.

Confirmation biasThe tendency to search for, interpret, and remember information in a way that supports what we already believe. Evidence against our view gets ignored, explained away, or forgotten.
Congruence biasThe tendency to test an idea only by checking whether its predicted result happens, without testing other explanations that could produce the same result. It is a close cousin of confirmation bias that shows up in how we test things.
Post-purchase rationalizationThe tendency to convince ourselves that something we bought was worth the money, especially when it was expensive or flawed. We play up its good points and brush off its faults to avoid feeling we made a mistake.
Choice-supportive biasThe tendency to remember our past choices as better than they were. We recall more good things about the option we picked and more bad things about the ones we turned down.
Selective perceptionThe tendency for our expectations and beliefs to shape what we actually see and hear. We notice what fits our view and filter out what doesn't, often without realizing it.
Observer-expectancy effectWhen a researcher or observer expects a certain result, they can unknowingly give off cues, like tone, pauses, or facial expressions, that push the people or animals being studied toward that result. The study then seems to show what the observer hoped for.
Experimenter's biasThe tendency for researchers to let their expectations shape how they design a study, collect data, and interpret or report results. It overlaps with the observer-expectancy effect, and it also covers the researcher's own private decisions, such as which data to keep and when to stop.
Observer effectnot a biasThe fact that observing something can change it. In everyday life, people often act differently when they know they are being watched, so what we observe may not reflect normal behavior. It is a measurement problem more than a bias, and it misleads us when we forget to account for it; a closely related idea is the Hawthorne effect.
Expectation biasThe tendency to see, hear, or measure what we expect and to doubt information that doesn't match. It is closely related to experimenter's bias, and it affects anyone who goes into a situation expecting a certain outcome.
Ostrich effectThe tendency to avoid information we fear will be bad. It is named after the myth that ostriches bury their heads in the sand, and avoiding the news feels better in the moment while letting problems grow.
Subjective validationThe tendency to accept a statement as true or accurate because it feels personally meaningful to us. It is closely linked to the Barnum effect, where vague descriptions seem tailor-made for us.
Continued influence effectThe tendency for false information to keep shaping our thinking even after it has been corrected. We may remember the correction, yet the original story still guides our judgments.
Semmelweis reflexThe reflex-like rejection of new evidence because it contradicts established beliefs or practices. It is named after Ignaz Semmelweis, a doctor in the 1800s whose finding that handwashing saved the lives of new mothers was dismissed by his colleagues.

Others' flaws · 3 biasesWe notice flaws in others more easily than we notice flaws in ourselves

We see our own intentions, reasons, and circumstances from the inside, while we only see other people's actions from the outside. Trusting our own view helps us act with confidence and stay alert to people who might take advantage of us.

Bias blind spotThe tendency to see the effect of biases on other people's judgment while seeing ourselves as less biased than average. Learning about biases does not reliably remove it.
Naive cynicismThe tendency to expect other people to be more selfish and biased than they really are, while seeing ourselves as fair. We read self-interest into others' actions even when there are other explanations.
Naive realismThe belief that we see the world objectively, as it really is, so people who disagree with us must be uninformed, irrational, or biased. We forget that our own view is also shaped by our experience and values.

Not Enough Meaning

The world is only partly visible, and you still have to make sense of it. Your brain fills the gaps with patterns, stereotypes, familiar cases, and guesses about what others think.

Stories & patterns · 13 biasesWe tend to find stories and patterns even when looking at sparse data

Our ancestors survived by spotting patterns fast: rustling grass might mean a predator, and dark clouds meant rain. Filling gaps with a plausible story lets us act on thin information instead of freezing. A brain that sometimes sees a pattern that isn't there loses less than one that misses a real threat.

ConfabulationConfabulation is when the mind fills a gap in memory or knowledge with an invented story, and the person honestly believes it. It is an honest error of memory, made without any intent to lie.
Clustering illusionThe clustering illusion is the tendency to see meaningful clumps or streaks in data that are actually random. True randomness often contains runs and bunches, so we mistake them for signs of a hidden cause.
Insensitivity to sample sizeInsensitivity to sample size is judging a result without considering how many cases it is based on. Small groups swing to extremes far more often than large ones, yet we treat their results as equally reliable.
Neglect of probabilityNeglect of probability is ignoring how likely something is when making a decision under uncertainty. We react to how bad or good an outcome would feel and treat tiny and moderate chances as if they were the same.
Anecdotal fallacyfallacyThe anecdotal fallacy is using a personal story or a few examples as proof of a general claim while ignoring broader evidence. A single vivid case can feel more convincing than statistics, especially on emotional topics like health, even when it is unusual.
Illusion of validityThe illusion of validity is overconfidence in a judgment when the available information tells a neat, consistent story, even if that information predicts poorly. The feeling of certainty comes from how well the story hangs together and says little about accuracy.
Masked man fallacyfallacyThe masked man fallacy is a reasoning error where two things are judged to be different only because you believe different things about them. It is named after the argument: I know who my father is, I don't know who the masked man is, so the masked man is not my father.
Recency illusionThe recency illusion is believing that a word, habit or trend is new when it has been around a long time, simply because you only recently started noticing it. It is closely related to the frequency illusion, where something seems to show up everywhere once you notice it.
Gambler's fallacyThe gambler's fallacy is believing a random event is less likely because it has happened a lot recently, or more likely because it hasn't happened in a while. Independent events like coin flips have no memory, so past results don't change the next one.
Hot-hand fallacyThe hot-hand fallacy is believing that someone on a winning streak is more likely to keep succeeding, even when each attempt is largely independent. It is the mirror image of the gambler's fallacy, and while some real streakiness does seem to exist in sports, a short lucky run is easily mistaken for the real thing.
Illusory correlationIllusory correlation is perceiving a link between two things that are not actually related, or seeing a stronger link than really exists. It often happens because the times the two things occur together stick in memory while the other times are forgotten.
PareidoliaPareidolia is seeing meaningful images or hearing meaningful sounds, especially faces and voices, in random or vague input. It comes from a brain tuned to detect faces quickly, even at the cost of false alarms.
AnthropomorphismAnthropomorphism is giving human traits, feelings or intentions to animals, objects or forces of nature. It helps us relate to and predict things, but it can mislead us about how they really work.

Stereotypes · 12 biasesWe fill in characteristics from stereotypes, generalities, and prior histories

We rarely have full information about a person or situation, so the brain fills gaps with what usually holds true for similar cases. Relying on categories, rules of thumb and trusted sources saves a huge amount of time and effort. For most of history, following the group and trusting experienced elders was a safe bet.

Group attribution errorThe group attribution error is assuming that one member's traits reflect the whole group, or that a group's decision reflects what every member wants. It treats a group as if it thinks with one mind.
Ultimate attribution errorThe ultimate attribution error is explaining an outside group's bad acts by their character while writing off their good acts as luck or special circumstances. For our own group, we tend to do the reverse.
StereotypingStereotyping is expecting a person to have certain traits because they belong to a group, without knowing anything else about them. Stereotypes can be positive or negative, and they often stick even when a person clearly doesn't fit.
EssentialismEssentialism is the belief that categories of people or things have a hidden, unchanging core that makes them what they are. It leads us to treat group differences as fixed and natural and to overlook how much circumstances shape them.
Functional fixednessFunctional fixedness is only being able to see an object as useful for its usual purpose. It blocks creative solutions that use familiar things in new ways.
Moral credential effectThe moral credential effect, also called moral licensing, is feeling freer to behave badly after doing something good or proving you are a good person. Past good deeds become a kind of credit that seems to excuse a later lapse.
Just-world hypothesisThe just-world hypothesis is the belief that the world is fair, so people generally get what they deserve. It leads us to blame victims for their misfortune and to assume successful people earned everything they have.
Argument from fallacyfallacyThe argument from fallacy is concluding that a claim must be false because the argument for it was flawed. A bad argument can still lead to a true conclusion.
Authority biasAuthority bias is giving more weight to the opinion of an authority figure than the evidence justifies, and being more easily swayed or directed by them. It can extend to topics far outside the person's real expertise.
Automation biasAutomation bias is trusting suggestions from automated systems, such as GPS, spell checkers or software alerts, too much, even when they are wrong. People may ignore contrary information or stop checking the machine's work.
Bandwagon effectThe bandwagon effect is adopting a belief or behavior because many other people are doing it. Popularity starts to feel like proof that something is right or good.
Placebo effectnot a biasThe placebo effect is a real improvement in how someone feels after an inactive treatment, because they expect it to help. It is an expectation effect more than a bias, and it shows that beliefs can shape how we experience symptoms such as pain or nausea.

Familiar is better · 9 biasesWe imagine things and people we're familiar with or fond of as better

Trusting people and things we know is usually safe, because familiarity means we have dealt with them before without harm. Favoring our own group helped our ancestors cooperate with the people they depended on. Liking what is close and known also saves the effort of judging everything from scratch.

Out-group homogeneity biasOut-group homogeneity bias is seeing members of other groups as all alike while seeing members of your own group as varied individuals.
Cross-race effectThe cross-race effect is the tendency to recognize faces of your own race more easily than faces of other races. It depends partly on how much experience a person has had with different kinds of faces, especially in childhood, and practice at telling such faces apart can shrink it.
In-group biasIn-group bias is favoring members of your own group over outsiders in trust, help, rewards and judgment. Even groups formed on a trivial basis, such as a random assignment, can trigger it.
Halo effectThe halo effect is letting one positive trait, such as good looks or charm, shape your opinion of a person's other, unrelated traits. The reverse, where one bad trait colors everything, is sometimes called the horn effect.
Cheerleader effectThe cheerleader effect is the tendency for people to look more attractive in a group than when seen alone. One explanation is that the brain averages the faces in a group, and averaged faces tend to look more appealing.
Positivity effectThe positivity effect is the tendency, which grows stronger with age, to pay more attention to positive information than negative information and to remember it better. It can support well-being, but it can also lead us to overlook warnings.
Not invented hereNot invented here is rejecting or undervaluing ideas, products or knowledge because they came from outside your own team, company or group. It is common in organizations that take pride in their own work.
Reactive devaluationReactive devaluation is valuing a proposal less because it came from an opponent or someone you see as on the other side. The same offer seems more appealing when it comes from a neutral or friendly source.
Well-traveled road effectThe well-traveled road effect is underestimating how long familiar routes take and overestimating how long unfamiliar ones take. One idea is that familiar trips feel shorter because they take less attention.

Simpler numbers · 9 biasesWe simplify probabilities and numbers to make them easier to think about

Our brains handle small, concrete quantities well but struggle with large numbers, fractions and odds. Rounding, grouping and labeling let us make fast decisions without doing the math. For most daily choices, a rough answer is good enough.

Mental accountingMental accounting is treating money differently depending on where it came from or which mental 'budget' it belongs to, even though every dollar is worth the same. It can help with budgeting, but it also leads to poor overall choices.
Appeal to probability fallacyfallacyThe appeal to probability is a logical fallacy that treats something as certain just because it is possible or likely. It jumps from 'this could happen' to 'this will happen'.
Normalcy biasNormalcy bias is assuming that because a disaster has never happened to you, it won't happen, and underestimating how bad it could be if it does. It can make people slow to respond to clear warnings.
Murphy's Lawnot a biasMurphy's Law is the saying 'anything that can go wrong will go wrong'. It is a humorous adage more than a bias, and it reflects how failures stick in memory while the many times things go fine are overlooked.
Zero sum biasZero sum bias is assuming that one person's gain must be another person's loss, even when both could benefit. Many situations, such as trade, friendship and learning, can create value for everyone involved.
Survivorship biasSurvivorship bias is drawing conclusions only from the people or things that made it through some filter, while ignoring those that did not. The missing failures often hold the most important information.
Subadditivity effectThe subadditivity effect is judging the chance of a whole event to be less than the sum of the chances of its parts. Breaking an event into detailed pieces makes each piece feel more likely, so the pieces add up to more than the whole.
Denomination effectThe denomination effect is being less likely to spend money when it is held in large bills than when the same amount is in small bills or coins. Breaking a large bill makes the money feel easier to spend.
Magic number 7+-2memoryThe 'magical number seven, plus or minus two' is a classic idea from psychologist George Miller that people can hold about seven items in short-term memory at once. Later research suggests the real limit is closer to four chunks, and it describes a limit of memory more than a bias.

Mind reading · 6 biasesWe think we know what other people are thinking

Social life depends on guessing what others think and feel. Using our own mind as a model for other minds is fast and often roughly right, because people share a lot. It let our ancestors predict friends and rivals without needing to ask.

Illusion of transparencyThe illusion of transparency is overestimating how clearly others can read your thoughts and feelings. Your inner state feels obvious to you, so you assume it shows on the outside.
Curse of knowledgeThe curse of knowledge is finding it hard to imagine not knowing something once you know it. Experts often explain things poorly because they forget what beginners don't yet know.
Spotlight effectThe spotlight effect is overestimating how much other people notice your appearance, mistakes and behavior. Because you are at the center of your own world, you assume you are at the center of everyone else's.
Extrinsic incentive errorThe extrinsic incentive error is assuming other people are driven mainly by outside rewards like money and perks, while seeing yourself as driven by inner rewards like learning and meaning.
Illusion of external agencyThe illusion of external agency is believing that a preference or good feeling you created yourself was caused by some wise outside force, such as fate, an expert or a guide. People underestimate how much their own minds adjust to make the best of a situation.
Illusion of asymmetric insightThe illusion of asymmetric insight is believing you understand other people better than they understand you. It also applies to groups, where each side thinks it sees through the other while being misunderstood itself.

Projecting ourselves · 14 biasesWe project our current mindset and assumptions onto the past and future

Imagining the past and the future is hard, so the brain uses the present as a template. Assuming things will stay roughly as they are now is a quick and usually workable guide. Making sense of events after the fact also helps us learn lessons and feel in control.

Self-consistency biasSelf-consistency bias is remembering your past attitudes and behavior as more similar to your current ones than they really were. We quietly rewrite our own history so that we seem to have always been the same.
Restraint biasRestraint bias is overestimating how well you can resist temptation. People who believe they have strong self-control put themselves in tempting situations more often and then give in.
Projection biasProjection bias is overestimating how much your future self will share the tastes, feelings and needs of your present self. It can also mean assuming other people share your current mindset.
Pro-innovation biasPro-innovation bias is the belief that a new technology or idea should be adopted widely, without its limits or downsides being examined. Supporters overvalue its usefulness and undervalue its problems.
Time-saving biasTime-saving bias is misjudging how much time you save by going faster. People overestimate the time saved when speeding up from an already high speed and underestimate it when speeding up from a low speed.
Planning fallacyThe planning fallacy is underestimating how long a task will take, and often how much it will cost, even when similar past tasks ran over. We picture the smooth, best-case path and forget the delays.
Pessimism biasPessimism bias is overestimating the chance that bad things will happen to you. It is the opposite of optimism bias and is more common in people who are depressed or anxious.
Impact biasImpact bias is overestimating how strongly and how long future events will affect your feelings. People adapt to both good and bad news faster than they expect.
DeclinismDeclinism is the belief that a society or institution is steadily getting worse. It often comes from comparing a fond memory of the past with the problems of the present.
Moral lucknot a biasMoral luck is judging people as more or less blameworthy based on outcomes they did not control. Two people can make the same choice, yet we blame the one whose choice happened to turn out badly far more harshly.
Outcome biasOutcome bias is judging a decision by how it turned out instead of by how sound it was when it was made. A bad decision can get lucky, and a good decision can fail.
Hindsight biasHindsight bias is the feeling, after something happens, that you knew it would happen all along. Once we know the result, it seems far more predictable than it really was.
Rosy retrospectionRosy retrospection is remembering past events as more pleasant than they felt while you were living through them. Small annoyances fade from memory while the good moments remain.
Telescoping effectThe telescoping effect is misplacing events in time, so that distant events seem more recent than they were and recent events seem further back. It is a memory error that can distort surveys and personal timelines.

Need To Act Fast

You rarely have the time or information to be certain, and waiting has costs too. Your brain boosts your confidence, favours what is near and simple, and sticks with what you already started.

Confidence to act · 21 biasesTo act, we must be confident we can make an impact and feel what we do is important

To act at all, we need some belief that our choices matter and that we can pull them off. A bit of extra confidence gets us moving, keeps us going after setbacks, and protects our sense of self-worth and our standing in a group.

Overconfidence effectOur confidence in our own judgments is often higher than our actual accuracy. We feel more certain than our track record justifies.
Social desirability biasThe tendency to present ourselves in a flattering light, over-reporting good behavior and under-reporting bad behavior. It shows up strongly in surveys, interviews and other self-reports.
Third-person effectThe belief that media messages, ads and propaganda influence other people more than they influence us.
False consensus effectThe tendency to overestimate how many people share our opinions, habits and values. We assume our own view is the normal one.
Hard-easy effectThe tendency to be overconfident on hard tasks and underconfident on easy ones. Our sense of how well we did does not adjust enough to how difficult the task really was.
Lake Wobegon effectother nameThe tendency for most members of a group to rate themselves as above the group's average, which cannot be true for everyone. It is named after a fictional town where 'all the children are above average,' and is another name for illusory superiority.
Dunning-Kruger effectPeople with little skill in an area tend to overrate their ability, while top performers often underrate how they compare with others. Dunning and Kruger argued that beginners miss their own errors because spotting mistakes takes the same know-how as avoiding them.
Egocentric biasThe tendency to rely too much on our own point of view, including remembering our own part in shared events as bigger or better than it was.
Optimism biasThe tendency to believe we are less likely than other people to face bad events, like illness, accidents or divorce, and more likely to enjoy good ones.
Forer effectother nameThe tendency to rate vague, general personality descriptions as highly accurate for us personally. It is named after psychologist Bertram Forer, who showed it using a personality test, and is another name for the Barnum effect.
Barnum effectWe accept vague statements that could apply to almost anyone as a precise description of ourselves. Also called the Forer effect, it is named after showman P.T. Barnum and the idea of offering 'something for everyone.'
Self-serving biasThe habit of taking credit for our successes while blaming outside factors for our failures. It protects our self-esteem.
Actor-observer biasThe tendency to explain our own actions by the situation but other people's actions by their character. It is closely related to the fundamental attribution error.
Illusion of controlThe tendency to believe we can influence outcomes that are really out of our hands, such as chance events.
Illusory superiorityThe tendency to overestimate our own qualities and abilities compared with other people. The Lake Wobegon effect is another name for it.
Fundamental attribution errorThe tendency to explain other people's behavior by their personality while underrating the situation they are in.
Defensive attribution hypothesisThe tendency to assign blame in ways that protect us from feeling we could suffer, or cause, the same harm. We blame the person responsible more as the outcome gets more severe, and we blame a victim less when they seem similar to us.
Trait ascription biasThe tendency to see ourselves as flexible and changeable in personality, mood and behavior, while seeing other people as fixed and predictable.
Effort justificationThe tendency to value an outcome more because we worked hard or suffered to get it. It eases the discomfort of thinking the effort might have been wasted.
Risk compensationnot a biasThe tendency to take more risks when we feel safer and to act more carefully when we feel more at risk. Safety measures can lose part of their benefit this way.
Peltzman effectother nameAnother name for risk compensation, often used for safety rules and regulations: when a law makes an activity safer, people may act less carefully and cancel out some of the gain. It is named after economist Sam Peltzman.

The here & now · 3 biasesTo stay focused, we favor the immediate, relatable thing in front of us

Attention and energy are limited, so the brain gives priority to what is here, now and personal. Things we can see clearly or picture in detail feel more real and urgent than distant or abstract ones. Reacting quickly to the reward or threat in front of us often mattered more than planning for a far-off future.

Hyperbolic discountingThe tendency to strongly prefer smaller rewards now over larger rewards later, with the pull of 'now' growing sharply as a reward gets close. It explains why we make sensible plans for the future and then abandon them when the moment arrives.
Appeal to noveltyfallacyA reasoning error where we assume an idea, product or method is better simply because it is new. It is the mirror image of assuming the old way is best because it is traditional.
Identifiable victim effectThe tendency to feel more for, and give more to, one specific person with a name and a face than a large group of unnamed people with the same need.

Finishing what we started · 13 biasesTo get things done, we tend to complete things we've invested time and energy in

Finishing what we start is usually a good strategy, since a brain that quit at every bump would never complete anything. Valuing what we already have, what we built and what we worked for keeps us committed and protects our resources. Losing what we have can hurt more than an equal gain helps, so caution around losses often makes sense.

Sunk cost fallacyThe tendency to keep going with something because of the time, money or effort already spent, even when continuing costs more than it returns. Past costs cannot be recovered, so they shouldn't drive future choices.
Irrational escalationother nameThe tendency to keep raising our investment in a losing decision to justify what we've already put in, often in a competitive setting. It is another name for escalation of commitment, and closely related to the sunk cost fallacy.
Escalation of commitmentA pattern where people or organizations keep backing a failing course of action because they've already committed to it, often to avoid admitting a mistake. It is also called irrational escalation, and it is closely related to the sunk cost fallacy.
Generation effectmemoryA memory effect: we remember information better when we produce it ourselves than when we simply read or hear it. It helps learning, and it is one reason we remember our own ideas better than other people's.
Loss aversionThe tendency to feel the pain of losing something more strongly than the pleasure of gaining something of equal value. Losing $50 usually feels worse than finding $50 feels good.
IKEA effectThe tendency to value things more highly when we have helped build or create them, even when the result is imperfect. It is named after the furniture store whose products buyers assemble themselves.
Unit biasThe tendency to treat one serving, portion or item as the right amount to finish, whatever its size. We tend to complete whatever single package is in front of us.
Zero-risk biasThe tendency to prefer completely removing a small risk over making a larger cut to a bigger risk. Eliminating a danger feels better than shrinking one, even when shrinking helps more.
Disposition effectThe tendency to sell things that have risen in value too early and to hold on to things that have fallen in value too long, hoping to get back to even.
Pseudocertainty effectThe tendency to treat an outcome as certain when it is only certain within one stage of a multi-stage situation. We overvalue options that remove risk at one step, even when the overall result is still uncertain.
Processing difficulty effectmemoryA memory effect: information that takes more effort to understand tends to be remembered better, because we think about it more deeply. It helps learning, though it can also make hard-won details stick even when they aren't the most important.
Endowment effectThe tendency to value something more just because we own it. People often ask much more to give up an item than they would pay to buy it.
Backfire effectThe tendency for some people, when shown evidence against a belief they hold dearly, to hold that belief even more strongly. Later, larger studies found this is rare: corrections usually move people at least a little toward the facts, even on charged topics.

Autonomy & status · 6 biasesTo avoid mistakes, we aim to preserve autonomy and group status, and avoid irreversible decisions

Keeping our freedom to choose and our standing in a group protects us from being exploited or pushed out. Sticking with what already works, and avoiding choices we can't undo, limits the damage of a bad call. These habits likely helped people get by in small groups, where losing status or making a costly mistake could be serious.

System justificationThe tendency to defend and justify the existing social, economic or political order, even when it works against our own interests. It makes the current system feel fair and natural.
Reverse psychologynot a biasA persuasion tactic where someone argues for the opposite of what they want, counting on the other person to push back and do the desired thing. It works by triggering reactance, and it steers us most when we don't notice it.
Reactancenot a biasThe urge to do the opposite of what someone wants when we feel our freedom to choose is being threatened. The harder the push, the stronger the pushback.
Decoy effectThe tendency for our choice between two options to change when a third, clearly inferior option is added. The added option makes one of the original two look better by comparison.
Social comparison biasThe tendency to feel dislike or competitiveness toward people who seem better than us in some way, which can lead us to hold them back. It often shows up in hiring and promotion decisions.
Status quo biasThe preference for keeping things as they are, even when a change would be better. The current state becomes the reference point, and any change feels like a risk.

Simple & complete · 10 biasesWe favor simple-looking options and complete information over complex, ambiguous options

Simple, clear options are faster to understand and easier to act on, and when time is short that speed matters. Known odds and complete information feel safer because they let us predict what will happen. Preferring the clear option often saves effort that would be wasted on puzzles we can't solve.

Ambiguity biasThe tendency to avoid options where the odds of a good outcome are unknown and to pick options with known odds instead, even when the unknown option might be better.
Information biasThe tendency to seek more information even when it cannot change what we will do. Extra data can feel like progress while only delaying the decision.
Belief biasThe tendency to judge an argument by whether we agree with its conclusion instead of by whether its reasoning holds up. A weak argument seems strong if its conclusion sounds believable to us.
Rhyme as reason effectThe tendency to judge a statement as more accurate or true when it rhymes. The sound makes it easier to process, and that ease feels like truth.
Bike-shedding effectother nameThe tendency for groups to spend lots of time on small, easy-to-grasp details while rushing through complex, important ones. It is another name for the law of triviality, from an example of a committee that argues about a bike shed and quickly approves a nuclear plant.
Law of Trivialitynot a biasAn observation by C. Northcote Parkinson that groups give too much time to trivial issues and too little to big, complex ones, so the time spent on an item can shrink as its cost grows. It is also called the bike-shedding effect.
Delmore effectThe tendency to set clear, detailed goals for less important tasks while leaving our most important goals vague. Big goals are hard and uncomfortable to define, so we busy ourselves with the easy ones.
Conjunction fallacyThe mistake of judging a specific combination of events as more likely than one of those events alone. Adding details makes a story feel more believable while making it less likely.
Occam's razornot a biasA problem-solving principle that says, among competing explanations, the one with the fewest assumptions should usually be preferred. It is a useful rule of thumb, but leaning on it too hard leads us to favor a simple explanation even when the evidence points to a more complex one.
Less-is-better effectA preference reversal where a smaller or cheaper option is preferred when judged on its own, while the larger or better option wins when the two are compared side by side. Without a comparison, we judge by easy cues like how full or complete something looks.

What Should We Remember?

You can't store everything, so memory keeps what seems useful later. Your brain saves generalities, peaks, and endings, and quietly edits details after the fact.

Edited memories · 6 biasesWe edit and reinforce some memories after the fact

Memory is rebuilt each time we recall it, which lets us update what we know with new information. Revisiting a memory also strengthens it, so the things we return to often become the easiest to reach. This keeps our knowledge current without storing every version of every event.

Misattribution of memoryRemembering a piece of information or a face correctly but linking it to the wrong source, time or place. It is an umbrella term that covers source confusion, cryptomnesia and some false memories.
Source confusionMixing up where a memory came from, such as mistaking something you were told, read or imagined for something you experienced yourself. It is a specific kind of misattribution of memory.
CryptomnesiaA forgotten memory comes back to mind without feeling like a memory, so you mistake it for a new idea of your own. It is a form of misattribution of memory and can lead to accidental copying.
False memoryRemembering an event that never happened, or remembering a real event very differently from how it went. False memories can feel as vivid and certain as true ones.
SuggestibilityThe tendency to take in ideas suggested by others, such as the hints hidden in leading questions, and then remember them as part of what really happened. Young children are especially prone to it.
Spacing effectmemoryWe remember information better and longer when we study it in several short sessions spread out over time than when we cram the same amount of study into one session. This is a helpful memory effect.

Generalities · 6 biasesWe discard specifics to form generalities

We could never store the details of every person and event we meet, so the brain boils experience down into categories and rough summaries. These let us make fast guesses about new people and situations with little effort. Holding on to bad experiences, while letting old pain soften, also helped us learn from danger without being crushed by it.

Implicit associationsAutomatic links in memory between two ideas, such as a brand and a feeling or a group and a trait, that shape our quick reactions without our awareness. They can differ from the views we hold on purpose, and researchers often measure them by how fast people pair words or images.
Implicit stereotypesUnconscious beliefs that tie a social group to certain traits and steer how we judge individuals from that group. They are a kind of implicit association and can clash with the fair-minded views we openly hold.
Stereotypical biasMemory that drifts toward stereotypes, so we recall details that fit what we expect of a group and forget or change details that do not.
PrejudiceA preformed judgment or feeling, usually negative, about a person based only on their membership in a group, such as race, religion, gender, age or nationality. It colors what we notice and remember about members of that group and how we treat them.
Negativity biasBad experiences and information weigh more heavily on us than good ones of the same size. In memory, unpleasant events tend to be recalled more strongly and in more detail than pleasant ones.
Fading affect biasOver time, the feelings attached to unpleasant memories fade faster than the feelings attached to pleasant ones. This helps us cope and move on, but it can make past hardships seem milder than they really were.

Key elements · 13 biasesWe reduce events and lists to their key elements

We cannot hold every moment of an experience or every item in a list in mind. The brain keeps a few standout pieces, such as the most intense moment, the ending, or the first and last items, and lets them stand for the whole. This makes memories compact and quick to use.

Peak-end ruleWe judge a past experience mostly by how it felt at its most intense moment and at its end. The average of all the other moments counts for much less.
Leveling and sharpeningTwo ways a memory changes as it is recalled and retold: leveling drops or smooths over details, while sharpening picks out a few details and makes them stand out more. Over time, stories become simpler and more dramatic.
Misinformation effectOur memory of an event becomes less accurate after we take in misleading information about it later, such as news reports, other people's accounts or the wording of a question. The new details quietly blend into the original memory.
Duration neglectWhen we judge how good or bad an experience was, we give little weight to how long it lasted. It is closely linked to the peak-end rule.
Serial recall effectmemoryThe patterns we show when trying to recall a sequence in its original order: the early items come back most reliably, and most mistakes are swaps of items that sat close together. It is closely related to the serial position effect.
List-length effectmemoryThe longer a list is, the smaller the share of its items we remember, even though we may recall a few more items in total.
Modality effectmemoryThe last few items of a list are remembered better when we hear them spoken than when we read them. Hearing gives the end of a list an extra boost in short-term memory.
Memory inhibitionmemoryThe mind's ability to hold back irrelevant or competing memories so we can focus on the one we need. A side effect is that recalling some items can make related items harder to reach later.
Part-list cueing effectmemoryBeing reminded of some items from a set can make it harder to recall the rest. The cues seem to pull memory toward the items you were given and away from the missing ones.
Primacy effectmemoryThe first items in a list or sequence are remembered better than those in the middle, partly because they get more attention and mental rehearsal. Early information can also shape how we judge what follows.
Recency effectmemoryThe last items in a list or sequence are remembered better than those in the middle, usually because they are still fresh in short-term memory. Recent events can also weigh too heavily in our judgments.
Serial position effectmemoryThe overall pattern in which we remember the first and last items of a list best and the middle items worst. It combines the primacy effect and the recency effect.
Suffix effectmemoryWhen an extra, irrelevant spoken word comes right after a spoken list, we recall the last items of the list less well. The add-on crowds out the final items in our short-term memory for speech sounds, while a beep or buzz has little effect.

How it was stored · 6 biasesWe store memories differently based on how they were experienced

Attention and memory are limited, so the brain stores more of what we think about deeply, use actively or expect to need, and less of what we barely noticed or know we can look up. This puts our limited memory where it pays off most.

Levels of processing effectmemoryInformation we think about in a deep, meaningful way is remembered better than information we only process on the surface, such as how a word looks or sounds. This is a helpful memory effect.
Testing effectmemoryPulling information out of memory, as in a quiz, makes it stick better than spending the same time rereading it. This is a helpful effect that learners can use on purpose.
Absent-mindednessmemoryMemory lapses that happen because we were not paying attention when something occurred, so it was never stored well in the first place. It often shows up when we act on autopilot or split attention between tasks.
Next-in-line effectmemoryWhen people take turns speaking in a set order, we tend to forget what the person right before us said, because we are busy preparing our own words.
Tip of the tongue phenomenonmemoryThe frustrating feeling of being sure you know a word or name while being unable to pull it up. You can often recall its first letter, its length or a similar-sounding word.
Google effectmemoryWe tend to forget information we know we can easily find online, and remember where to find it instead. It is also called digital amnesia.