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Action bias is the tendency to favor doing something over doing nothing, even when there is no evidence that acting produces better outcomes — and sometimes when the evidence favors waiting. Action feels like competence and control; inaction feels like negligence, even when it is the optimal strategy.
The affect heuristic is the tendency to let an immediate feeling of 'good' or 'bad' stand in for a deliberate evaluation of risks and benefits. Things we like are judged to be low-risk and high-benefit; things we dislike are judged high-risk and low-benefit — even though in reality risk and benefit are often positively correlated.
Ambiguity bias is preferring a known risk over an unknown one, even when the unknown option may have equal or better expected value. Uncertainty about the probabilities themselves feels like extra danger beyond the outcomes at stake.
Anchoring is the pull of an initial number, price, or estimate on later judgment — even when the starting point is arbitrary. We adjust away from the anchor, but usually not far enough.
The anecdotal fallacy is treating one vivid story as evidence of a general rule while ignoring how representative the story is. An anecdote can make a possibility emotionally real; it cannot by itself establish frequency, cause, or typical outcome.
The appeal to novelty is treating newness as evidence of superiority. A product, idea, or method feels like progress because it is new, even when its outcomes, fit, and reliability have not yet earned that conclusion.
The appeal-to-probability fallacy is treating a possible outcome as though it were inevitable simply because nothing rules it out.
Attentional bias is repeatedly noticing information that fits a current concern, goal, fear, or desire while giving less attention to other relevant signals.
Authority bias is giving a claim extra weight because it comes from a prestigious, powerful, or credentialed person, beyond what their relevant evidence and expertise justify. Authority becomes a substitute for checking the claim itself.
Automation bias is giving an automated recommendation more trust than its reliability and the surrounding evidence justify.
An availability cascade is a self-reinforcing cycle in which a claim or risk becomes more believed simply because it is more discussed: media coverage makes it mentally available, availability makes it feel true and important, which generates more coverage and social pressure to agree. Public perception can thereby detach almost completely from underlying facts.
The availability heuristic is judging frequency, danger, or importance by how easily examples come to mind. What is vivid, recent, emotional, or repeatedly covered by media feels common — even when the base rate says otherwise.
The bandwagon effect is adopting a belief, product, or action because many other people appear to have adopted it. Popularity becomes a shortcut for truth, quality, or safety — and each new adopter makes the signal look stronger.
The base-rate fallacy is judging a specific case from a vivid clue while neglecting how common the outcome was before the clue appeared. A compelling story can feel more diagnostic than the numbers that should set the starting odds.
The bias blind spot is readily detecting bias in other people while treating our own judgment as unusually objective. Because our reasoning feels sincere from the inside, the absence of a felt motive is mistaken for the absence of bias.
The certainty effect is the tendency to overweight outcomes that are certain relative to outcomes that are merely probable. Reducing risk from 5% to 0% feels far more valuable than reducing it from 10% to 5%, though both remove the same five points of probability — certainty carries a premium that distorts otherwise consistent preferences.
Choice overload is the phenomenon whereby having too many options can make deciding harder, reduce satisfaction with the chosen option, and sometimes prevent choosing at all. More choice is not monotonically better: beyond a point, each added option adds comparison cost, anticipated regret, and doubt.
Choice-supportive bias is revising memory so the option we chose looks better and the options we rejected look worse than they did at the time. The decision becomes evidence of its own quality.
The clustering illusion is seeing meaningful runs, clusters, or hot spots in data that random variation can produce on its own. Randomness is lumpy; we expect it to look more evenly mixed than it does.
Confirmation bias is the tendency to treat evidence as a lawyer for what we already believe rather than a test of whether we are right. It shapes what we search for, notice, remember, and count as convincing — often without feeling like bias at all.
Congruence bias is testing a hypothesis only in ways that could confirm it, rather than seeking observations that might rule it out.
The conjunction fallacy is judging a detailed story as more likely than a broader category that includes it. A description can feel highly representative, but 'A and B' can never be more probable than 'A' alone.
Conservatism cognitive bias refers to the tendency of individuals to insufficiently revise their beliefs when presented with new evidence. This bias falls under the broader category of information overload, as people tend to give disproportionate weight to their prior knowledge or beliefs and do not adequately adjust them with fresh information. The phenomenon is closely associated with the psychological difficulty of abandoning previously held concepts and the innate preference for consistency.
The continued influence effect is using misinformation in reasoning after learning that it was false. A correction can update a stated belief while the original claim continues to supply the causal story that explains what happened.
Declinism is the tendency to see a society, institution, or culture as broadly worsening while idealizing a selectively remembered past.
The decoy effect is a shift in preference caused by adding a third option that nobody should choose. The decoy makes one target option look clearly superior by comparison, even though it does not improve that option itself.
The default effect is the tendency to end up with whatever option requires no action. Pre-selected choices are adopted at far higher rates than identical options requiring an active step — one of the largest and most reliable effects in behavioral science, and the workhorse of choice architecture.
The Delmore effect is the tendency to set clear, detailed, and articulate goals for the lower-priority areas of our lives, while our most important ambitions remain vague and unarticulated. Named after the poet Delmore Schwartz, it describes why people often have precise plans for minor tasks but only hazy intentions for the goals that matter most to them.
The denomination effect is spending the same amount of money more freely when it is divided into smaller, easier-to-part-with units.
A gain feels ready to celebrate; a loss feels easier to postpone. The disposition effect is investors’ tendency to sell winning positions relatively quickly while holding losing positions too long, even when the next decision should depend on future prospects rather than the purchase price.
Distinction bias is exaggerating the importance of small differences when options are compared side by side, even though the difference would barely matter in use.
The Dunning–Kruger effect is the debated finding that low performers can overestimate their ability, partly because the knowledge needed to perform a task also helps a person judge performance. The popular caricature — ignorant people are always supremely confident and experts always humble — goes far beyond the evidence.
Duration neglect is underweighting how long an experience lasted when remembering or choosing it. Retrospective evaluation often follows the peak and the ending more than the total amount of pleasure, pain, effort, or time.
Effort justification is valuing something more because getting it was costly, painful, or difficult.
Egocentric bias is overweighting your own perspective, effort, and role because it is more available to you than everyone else's.
The end-of-history illusion is the tendency to believe that who we are right now is who we will remain — that our present values, preferences, and personality are the finished product, even while readily acknowledging how much we've changed in the past. At every age, people report substantial past change and predict minimal future change.
The endowment effect is valuing an item more once it is ours than we valued the identical item before owning it. Ownership changes the reference point: giving it up feels like a loss, while acquiring it had felt like a possible gain.
A bad bet can become harder to leave precisely because so much has already gone into it. Escalation of commitment is the tendency to add time, money, or reputation to a failing course in order to justify an earlier decision, rather than deciding from the remaining costs and expected benefits.
Extrinsic incentive error is overestimating how much other people are driven by visible rewards while underestimating interest, meaning, identity, and other internal motives.
The false-consensus effect is overestimating how many other people share your view, preference, or behavior.
The focusing illusion is the tendency to exaggerate the importance of whatever we are currently thinking about. As Kahneman put it: nothing in life is as important as you think it is, while you are thinking about it. Attention inflates the weight of the attended factor in judgments of happiness, value, and choice.
The framing effect is changing a choice by changing its presentation while leaving the underlying facts the same. A 90% survival rate and a 10% mortality rate describe the same outcome, yet they invite different feelings, attention, and decisions.
The frequency illusion, often called the Baader–Meinhof phenomenon, is the sense that something suddenly appears everywhere after we first notice it. Attention changes what enters awareness, and the new sightings are mistaken for evidence that the world changed.
The fundamental attribution error is the tendency to explain other people's behavior by character while underweighting the situation they were in. We see the person clearly and the pressures, incentives, and missing information around them only dimly.
The gambler's fallacy is expecting an independent random process to correct itself in the next draw. After a streak, a reversal feels due — but a fair coin, roulette wheel, or lottery machine has no memory of the sequence.
The halo effect is letting one positive trait — attractiveness, prestige, polish, friendliness, a famous brand — spill into judgments about unrelated traits. A good first impression quietly becomes evidence of competence, honesty, or quality.
The hard-easy effect is a calibration pattern: confidence is often too high on difficult tasks and too low on easy ones.
Hindsight bias is seeing an outcome as obvious after it happens and remembering our earlier uncertainty as smaller than it was. Once we know the answer, it becomes hard to reconstruct a world in which the answer was still unknown.
The hot-hand fallacy is seeing a run of successes and inferring that the next success is more likely, when the process has no memory. The classic sports example is now contested: some apparent streaks are real, so the question is not whether a run exists but whether evidence shows a mechanism behind it.
Hyperbolic discounting is the pattern in which a delay feels much more costly near the present than the same delay feels in the distant future.
The identifiable-victim effect is giving more help when need is represented by one known person than by an equally serious statistical description of many people.
We tend to value things more when we helped make them. The IKEA effect is the extra attachment or willingness to pay that can follow successful assembly, customization, or creation—even when an equivalent finished version would serve just as well.
Having a choice can feel like having influence, even when chance or outside conditions determine the result. The illusion of control is the tendency to overestimate how much one’s actions affect an outcome that is largely random or externally constrained.
The illusion of validity is feeling confident in a judgment because the evidence forms a coherent story, even when it predicts poorly.
Illusory correlation is seeing a meaningful relationship between two things because their co-occurrences are vivid, even when the full data do not support one.
Illusory superiority is rating your own ability or character as better than most people's on a trait where that cannot be true for everyone.
Impact bias is overestimating how intensely and how long a future event will affect our feelings. We imagine the promotion, breakup, purchase, or rejection in a spotlight, then underestimate adaptation and the rest of life that will quickly compete for attention.
Implicit associations are automatic links between social categories and concepts that can be measured in rapid-response tasks, whether or not a person endorses those links explicitly.
In-group bias is favoring people we see as 'us' over people we see as 'them,' even when group membership is arbitrary and the evidence about individuals is equivalent. Belonging can quietly become a proxy for trust, competence, and deservingness.
Information bias is seeking more information even when it will not change the decision. More data feels like progress and protection from regret, but it can add delay, noise, and a false sense of rigor without adding decision value.
Insensitivity to sample size is treating a striking result from a small sample as though it were as stable as the same result from a large sample.
The Lake Wobegon effect is the impossible pattern in which most people rate themselves above average on a valued trait.
The Law of Triviality, also known as Parkinson's Law of Triviality, describes a phenomenon where people give disproportionate weight and time to trivial issues while neglecting more complex and critical matters. This cognitive bias leads to decision-makers focusing on simple tasks that are easy to understand and discuss, rather than tackling the more significant issues that require deeper analysis.
A smaller option can look better when it is judged on its own, then lose as soon as it is placed beside a clearly superior alternative. The less-is-better effect is this preference reversal: people overweight an easy-to-evaluate cue and underweight total value in separate evaluation.
Leveling and sharpening are complementary memory changes: retellings lose qualifying detail while a few salient details become more central or exaggerated.
Loss aversion is the tendency for a loss to hurt more than an equivalent gain feels good. It makes keeping what we have psychologically compelling, even when a neutral comparison of future outcomes would favor a change.
Mental accounting is treating identical money differently depending on its label, source, or imagined purpose.
The mere exposure effect is a psychological phenomenon where people tend to develop a preference for things they are repeatedly exposed to. This cognitive bias suggests that familiarity with something can lead to affection, even if it was initially neutral or disinterested.
The mere ownership effect is the tendency to evaluate an object more favorably simply because you own it — independent of any transaction. Where the endowment effect concerns what you'd charge to give something up, mere ownership shows that possession alone, even momentary and unchosen, makes things seem better.
Money illusion is reacting to the number on a price tag or paycheck as though it were purchasing power, without adjusting for changing prices.
The moral credential effect is the temptation to treat a past good deed as proof that a questionable choice now cannot reflect badly on you.
Moral luck is judging identical choices more harshly or more favorably because chance made their outcomes different.
Motivated reasoning is the tendency to process information in ways that arrive at the conclusions we want to reach, while experiencing the process as objective. Desired conclusions get asked 'Can I believe this?'; undesired ones get asked 'Must I believe this?' — two very different evidentiary bars.
Murphy's Law is a useful engineering maxim, not a cognitive bias: if a failure mode is possible and left unguarded across enough opportunities, it may eventually occur.
We may grant our own motives their full complexity while treating other people’s motives as mostly self-serving. Naïve cynicism is the tendency to assume that others are more biased, strategic, or driven by private interest than we are.
Naïve realism is experiencing our own view as a direct reading of reality and explaining disagreement as ignorance, irrationality, or bias in the other person. We forget that our own attention, values, incentives, and prior beliefs also shape what looks obvious.
Negativity bias is giving bad news, criticism, threats, and losses more attention and weight than equally strong good news. One sharp negative signal can dominate a much larger body of positive or neutral evidence.
Neglect of probability is reacting to the size or vividness of a possible outcome while giving too little weight to how likely it is.
Normalcy bias is treating an unfolding threat as if ordinary conditions will continue, especially when the alternative is disruptive or frightening. Because a disaster has not happened here before, warnings are discounted until the evidence becomes impossible to ignore.
Not Invented Here is discounting a useful external idea, tool, or solution because it came from outside the team or organization. Internal ownership feels like evidence of quality; external origin feels like a reason for suspicion.
Occam's razor is a reasoning principle, not a bias: when explanations fit the evidence equally well, prefer the one that adds fewer unsupported assumptions.
Omission bias is judging harm caused by action as worse than equal harm caused by inaction. Doing nothing feels morally cleaner because the causal role is less visible, even when the decision to refrain was itself a choice.
Optimism bias is expecting better outcomes for ourselves than for similar other people. We accept the general risk — layoffs, illness, delays, losses — while quietly treating our own case as the exception.
The ostrich effect is avoiding threatening information because looking at it feels worse, even when the information could improve the next decision.
Outcome bias is treating a decision as good because it worked out, or bad because it did not, even when the result depended heavily on luck.
Overconfidence is believing a judgment is more accurate, a skill stronger, or an outcome more controllable than the evidence warrants. Its most useful form is overprecision: confidence intervals that are far too narrow for how uncertain the world really is.
The peak-end rule is a cognitive bias that impacts how people retrospectively evaluate experiences. According to this rule, individuals tend to judge experiences based largely on how they felt at the most intense point (the peak) and at the end, rather than on the total sum or average of every moment of the experience.
Pessimism bias is forecasting negative outcomes as more likely, more severe, or less manageable than the available evidence supports.
The planning fallacy is predicting a project from its best-case internal story while neglecting how similar projects actually went. We see the steps we intend to take and miss delays, rework, coordination costs, and the base rate of overruns.
Post-purchase rationalization is defending a purchase after the fact so it feels more valuable and less regrettable. It is the consumer version of choice-supportive bias: the receipt turns a debatable option into 'the right choice.'
Prejudice is a negative or hostile evaluation of people because of their group membership. Unlike a stereotype, which is a generalized belief, prejudice includes an evaluative attitude that can shape attention, trust, and treatment before individual evidence is considered.
Present bias is the tendency to give disproportionate weight to immediate costs and rewards relative to future ones — beyond what any consistent discounting of the future would justify. We plan patiently for our future selves, then reliably overrule the plan when the moment arrives.
The primacy effect is remembering or overweighting what came first in a sequence. Early items receive more attention and rehearsal, and early impressions can become the frame through which later information is interpreted.
Pro-innovation bias is treating a new technology or idea as inherently beneficial while discounting its trade-offs, failure modes, and distribution of costs.
Projection bias is assuming that future preferences will resemble the preferences we feel right now. Hunger, excitement, loneliness, motivation, and fear masquerade as stable information about what our future selves will want.
The pseudocertainty effect is treating a conditional or partial reduction in risk as though it creates certainty in the overall situation.
Reactance is the urge to reassert freedom when a message, rule, or person feels controlling. A threatened option can become more attractive precisely because someone appears to be taking it away.
Reactive devaluation is discounting a proposal because it came from an opponent, rival, or distrusted source rather than because its terms are worse.
The recency effect is remembering or overweighting what came last because it is still active in short-term memory. The newest information can feel most representative even when it is only the latest item in a longer record.
Regression to the mean is the statistical fact that extreme measurements tend to be followed by less extreme ones, simply because extremes are partly luck. The bias is our systematic failure to expect this: we attach causal stories — credit, blame, interventions that 'worked' — to changes that are just statistics doing what statistics does.
The representativeness heuristic is the tendency to judge the probability that something belongs to a category by how closely it resembles the typical member of that category, rather than by how likely it actually is. Because similarity is easier to assess than probability, we substitute one for the other — and ignore base rates, sample sizes, and chance in the process.
Restraint bias is overestimating how well your future self will resist a temptation, then placing that future self in its path.
Risk compensation is increasing risky behavior after a safety measure makes danger feel lower, reducing some of the measure's benefit.
Rosy retrospection is remembering a past experience as better than it felt while you were living it.
Salience bias is the tendency to focus on information that is vivid, emotionally striking, or perceptually prominent while neglecting information that is duller but often more important. What grabs attention gets weighted; what doesn't, effectively doesn't exist for the decision.
Scope neglect is the tendency for our valuation of a problem to be nearly insensitive to its size. People will pay about the same to save 2,000, 20,000, or 200,000 birds; the emotional image driving the judgment — one oil-soaked bird — doesn't scale, so the numbers barely register.
Selective perception is noticing, interpreting, and remembering information through a filter shaped by what you already expect or believe.
Self-serving bias is claiming personal credit for success while assigning failure to circumstances, luck, or other people. The same evidence gets two attribution rules, both of which protect a flattering view of the self.
The Semmelweis reflex is a cognitive bias wherein people tend to reject new evidence or knowledge if it contradicts established norms or beliefs. Named after Ignaz Semmelweis, a 19th-century Hungarian physician who discovered that hand-washing could drastically reduce childbed fever incidence, the term describes the tendency to dismiss or undervalue findings that conflict with accepted paradigms.
Social comparison bias is devaluing or avoiding people who threaten our relative status, especially when we control an opportunity they could receive. A stronger candidate can feel like a risk to the self rather than an asset to the group.
Social desirability bias is giving the answer that looks respectable, safe, or acceptable rather than the most accurate answer.
Status quo bias is preferring the current arrangement because it is current, even when a fresh comparison would favor change. The costs of changing are vivid and immediate; the costs of staying put are familiar, dispersed, and easy to leave uncounted.
Stereotyping is using a broad belief about a group to infer traits, ability, motives, or behavior in a particular person. A category replaces individual evidence, often with more confidence than the evidence can support.
The streetlight effect is the tendency to search for answers where searching is easiest rather than where the answer is most likely to be — like the drunkard looking for his keys under the streetlight because 'that's where the light is.' In research and analytics, we measure what is measurable and quietly redefine the question to match.
The subadditivity effect is assigning a lower probability to a whole event than the probabilities assigned to its mutually exclusive parts add up to.
Subjective validation is finding a statement convincing because it feels personally meaningful, even when the statement is too vague to distinguish you from many others.
The sunk-cost fallacy is continuing a course of action because of time, money, or effort already spent, even though that investment cannot be recovered. The past feels like a reason to continue; economically, only the value and cost from this moment forward should decide.
Survivorship bias is drawing conclusions from the winners we can see while missing the failures that vanished from view. The visible sample feels like the whole population, so success looks more common — and more easily copied — than it really is.
Time-saving bias is misjudging how much time a change in speed actually saves, especially when comparing rates rather than durations.
Unit bias is the tendency to treat one presented unit—a plate, packet, episode, or task—as the natural amount to finish.
A change is judged against its background, not in isolation. Adding one candle is obvious in a dark room but barely registers in a brightly lit one. The Weber–Fechner tradition describes this diminishing sensitivity: as a stimulus grows, a larger absolute change is often needed for people to notice a difference.
Zero-sum bias is assuming that another person's or group's gain must come at your expense, even when the situation can create value for more than one side.
Zero-risk bias is choosing to eliminate a small risk completely instead of reducing a much larger risk by more. Zero feels categorically safer than a small residual risk, even when the alternative leaves people safer overall.