Cognitive biases

Action bias is the tendency to do something when waiting or leaving things alone would be the better choice. The important comparison is what could reasonably be expected at the time. A bad result does not automatically make the decision to act a bad one.

Actor–observer bias is the idea that we explain our own actions through circumstances but explain other people’s actions through their personalities. It is a familiar psychology lesson. The broad rule, however, has a weak research record.

Adverse selection occurs when information differences affect who participates in a transaction, or which products are offered, in a way that leaves the less-informed party with poorer options. The problem is how the information gap changes the mix of buyers, sellers, or goods.

The affect heuristic is the use of a positive or negative feeling about something as a shortcut in judgment. A favorable impression can influence how its risks and benefits are evaluated; an unfavorable impression can influence them in the opposite direction.

Affinity bias means favoring people because they seem similar or familiar. Similarity may concern shared interests, experiences, attitudes, or background. Feeling at ease with someone can enter a judgment that was supposed to concern their work or qualifications.

The Allais paradox is a pattern of choices between risky prospects that violates the independence principle of expected utility theory. The issue is consistency between two choices, rather than simply choosing a smaller expected monetary payoff.

Ambiguity aversion, also called uncertainty aversion in this context, is a preference for options with better-known probabilities over otherwise comparable options with less-known probabilities. It differs from risk aversion, which concerns preferences over outcomes when probabilities are specified.

The ambiguity effect is a label for choices influenced by uncertainty about probabilities, often a preference for better-known chances. It is closely related to ambiguity aversion. The uncertainty concerns the odds themselves, rather than just whether a known gamble will pay off.

Anchoring is a cognitive bias in which an initial piece of information — the anchor — disproportionately influences subsequent judgments and estimates. A buyer shown a high comparison price might judge a lower asking price more favorably. The initial number gives the later judgment a starting point.

Anthropomorphism is attributing humanlike characteristics, intentions or emotions to nonhuman entities, such as an object, animal or imagined agent.

Apophenia is perceiving meaningful patterns or connections where the evidence does not support them, including in unrelated events or random information.

An association fallacy occurs when a judgment about a person or claim rests on an irrelevant or insufficient association. In guilt by association, an argument is dismissed because of the people or group associated with its speaker, rather than because of a defect in the argument.

Assumed similarity bias occurs when people perceive others as more like themselves than they actually are. The broader term assumed similarity describes judgments of another person that reflect one’s own characteristics; those judgments are not necessarily inaccurate. It is related to, but broader than, the false-consensus effect concerning how widely one’s views or behavior are shared.

Attentional bias is a tendency to give some information more attention than other information. What you notice can depend on your goals, emotions, beliefs, and experience.

Attribute substitution means answering a difficult question by judging something easier. The substitute may be related to the question, but it is not quite what you were asked.

Attribution bias is a systematic distortion in how people explain behavior or events. It is an umbrella term for several patterns, rather than one rule everyone follows.

Authority bias is giving a claim or recommendation more weight than its evidence warrants because it comes from a perceived authority.

Automation bias is inappropriate reliance on an automated aid in making a judgment or decision.

The availability heuristic is a mental shortcut in which people estimate the frequency or likelihood of an event based on how easily examples come to mind. Repeated reports of shark attacks, for example, could make those events easier to recall when someone judges the danger of going swimming. Ease of recall can be informative, but it can also diverge from actual frequency or probability.

The Baader-Meinhof phenomenon, also called the Baader-Meinhof effect or frequency illusion, is the experience of suddenly noticing a word, idea, or object everywhere after you first become aware of it. Learn about a new type of bird, then spot it all over the neighborhood: that is the familiar experience the term describes.

A backfire effect occurs when a correction increases belief in the misinformation it is intended to correct. This is stronger than merely refusing to change one’s mind, and it should not be assumed whenever a person disagrees with evidence.

The bandwagon effect is a shift toward a belief, choice, or behavior because it appears popular. Visible support becomes a reason for further support.

The Barnum effect, also known as the Forer effect, is the tendency to accept a vague, general description as specifically true of you. “You are hardworking and determined, but sometimes have trouble making decisions” can feel personal. It also fits a great many people. A vague description of this kind is often called a Barnum statement.

The base rate fallacy, also called base rate neglect, occurs when a probability judgment gives too little weight to how common an outcome is in the relevant population.

Behavioral finance studies how psychological factors and limits on market correction can help explain financial decisions and market outcomes. Its questions include investor judgment, trading, asset prices, and corporate decisions.

Behavioral game theory uses evidence from psychology and experiments to study strategic decisions: choices whose results depend on what other people do. It examines limited strategic reasoning, learning, and social preferences.

Belief bias occurs when the believability of a conclusion influences a judgment about whether an argument is logically valid. A valid argument is one whose conclusion follows from its premises. That is a different question from whether the conclusion sounds true.

The Ben Franklin effect, also called the Benjamin Franklin effect, describes the possibility that doing someone a favor can increase the helper’s liking for that person. It is not a rule that every favor improves a relationship.

Bias, in judgment and decision research, is a systematic tendency for judgments or choices to depart from a specified comparison standard. The standard must be stated: a statistical probability, a logical rule, or a consistency requirement, for example. A preference is not a bias merely because someone else disagrees with it.

The bias blind spot, also called blind spot bias, is the tendency to see yourself as less susceptible to bias than other people. You can recognize a pattern in someone else while believing your own judgment is objective.

The bizarreness effect is better recall for bizarre than ordinary material under some learning conditions. It is related to distinctiveness and the von Restorff effect, but is not an exact synonym for isolation effects.

The bottom dollar effect is reduced satisfaction with a purchase when paying for it exhausts a budget, compared with a purchase that leaves money in that budget. Also described as a “last dollar” effect, it concerns spending to zero within an available budget. That need not mean losing all your money.

Bounded rationality is an approach to decision-making that takes limits on information, time, and computation seriously. A decision procedure can be sensible for the person and situation without finding the best option from every conceivable alternative.

Bundling bias describes a postpurchase consumption effect: paying one combined price for several benefits can weaken the perceived connection between the payment and each benefit. A person may then be less likely to use a prepaid service than if its price had been separate.

“Bye-now effect” is a popular label for a phonological priming finding involving the English homophones “bye” and “buy.”

Category size bias is a probability-judgment error in which an outcome seems more likely because it belongs to a larger category, even though its own objective probability is unchanged.

The certainty effect concerns the special weight given to a sure outcome relative to a probable one. The possibility effect describes the impact of making an outcome possible when it was previously impossible.

The certainty effect is a disproportionate response to the difference between a certain outcome and a merely probable one. The crucial difference is between “will happen” and “might happen,” not simply between better and worse odds. It is one of the findings discussed in prospect theory.

The cheerleader effect, also called the group attractiveness effect, is a reported tendency for an individual face to be rated as more attractive in a group than when shown alone.

“Chivas Regal effect” is a popular label for using a higher price as a cue to higher quality. Think of two price tags on the same product: does the higher one make it seem better? That is a question about perceived quality, not a change in the product itself.

Choice overload, also called overchoice, refers to adverse effects that can occur as a choice set grows, such as more deferral or lower satisfaction.

Choice-supportive bias is misremembering information in a way that favors a chosen option or disfavors a rejected option. After choosing between two products, for example, a person might later assign a good feature to the one they bought even though it belonged to the alternative.

A cognitive bias is a systematic pattern in judgment that departs from a specified standard, such as a probability rule. Identifying a bias requires a clear task and comparison standard. Its size and prevalence can vary across people and contexts.

Cognitive dissonance is the psychological discomfort that arises when a person holds two or more contradictory beliefs, values, or attitudes, or when their behavior conflicts with their self-concept. First described by Leon Festinger in 1957, the theory predicts that people are motivated to reduce this discomfort — typically by changing one of the conflicting cognitions, adding new consonant cognitions, or reducing the perceived importance of the conflict. A smoker who believes smoking is harmful may feel this conflict and respond by quitting, downplaying the risks, or emphasizing a perceived benefit such as stress relief. The theory proposes conditions under which people may change an attitude or reinterpret an action; inconsistency does not guarantee a particular response.

A cold state is a condition in which a particular intense visceral influence, such as hunger, craving, or anger, is weak or absent. The term is relative to the influence being considered; it does not mean that the person has no emotions.

Collider bias occurs when a statistical analysis conditions on a shared consequence of other variables, potentially creating or distorting an association. The relevant causes need not be the treatment and outcome themselves; they may also be causes of those variables.

Confirmation bias is the tendency to search for, interpret, favor, and recall information in ways that confirm pre-existing beliefs or hypotheses. It can affect the questions people ask and the evidence they seek or interpret. A hiring manager who believes a candidate is strong may unconsciously focus on interview answers that support that impression while discounting signs of weakness. Confirmation bias can overlap with motivated reasoning, but it does not require a conscious wish to defend a preferred answer.

The conjunction fallacy occurs when someone judges two events occurring together as more probable than one of those events occurring on its own. For the same information and possible outcomes, P(A and B) cannot exceed P(A) or P(B). This rule does not require the events to be independent.

A contrast effect occurs when a judgment shifts away from a comparison context. An item can seem smaller, worse or less attractive alongside high-valued examples, or larger, better or more attractive alongside low-valued ones.

Courtesy bias is giving an overly favorable response to avoid offending or disappointing an interviewer, provider, or other person. It overlaps with social desirability bias but is not a synonym for every form of socially acceptable responding.

Cryptomnesia is remembering an idea without recognizing its source, then experiencing it as a new thought. The memory remains, but its origin is lost.

Cultural bias is systematic distortion in judgment or measurement arising when culturally specific meanings, assumptions, or procedures are treated as equally appropriate across groups.

The curse of knowledge is difficulty setting aside what one knows when judging the perspective of someone who lacks that information. In experiments by Camerer, Loewenstein, and Weber, informed participants’ predictions of less-informed people were pulled toward their own extra knowledge.

Decision fatigue describes a proposed change in decision-making after many choices or a long period of demanding decision work. Someone may avoid another choice, compare fewer options, or rely more on shortcuts. The term does not establish that the mind has a fixed daily supply of decision energy.

Decision paralysis, also called choice paralysis in everyday use, is an informal description of difficulty choosing or moving to action. Too many options may contribute, but a person may also have unclear goals, missing information, or a good reason to wait. The label is not a diagnosis or an explanation by itself.

Decision utility is the weight an outcome receives in a person's choices. It is inferred from preferences and decisions, rather than simply being a forecast of how happy the person expects to feel.

The decoy effect, or attraction effect, is a change in choice caused by adding an option that is clearly inferior to one existing option but not inferior to the other in the same way. That relationship is called asymmetric dominance.

The defensive attribution hypothesis proposes that self-protective motives influence judgments of responsibility for harmful events. Observers may consider, implicitly or explicitly, whether a similar event could happen to them or whether they could be blamed in a similar situation.

The denomination effect is a difference in spending when the same amount of money is held in different denominations. Raghubir and Srivastava found that people were less likely to spend an amount held as one large bill than the equivalent amount held as smaller bills.

Diminishing sensitivity describes a smaller subjective difference between equal-sized changes farther from a reference point. In prospect theory, this helps characterize the shape of the value function for gains and losses.

Thinking takes time and effort. Directed cognition is a behavioral economics model of how people decide which information is worth looking for next.

Discounted utility is a way to compare outcomes that arrive at different times. The model assigns a time weight to each outcome’s utility, or subjective value, then adds the weighted values together.

The disposition effect is investors’ tendency to sell winners more readily than losers, usually judged against the price they paid. Shefrin and Statman named the pattern in 1985; Odean (1998) later examined it in 10,000 brokerage accounts.

Diversification bias is the tendency to choose more variety when selecting several items together for future use than when choosing them one at a time. Pick snacks for the whole week and you may choose more different kinds than you would pick separately on each day.

Dual-process theories distinguish relatively automatic responses from reasoning that requires deliberate mental effort. They are a family of models, rather than one theory of two separate brain systems.

The Dunning–Kruger effect is a pattern in which lower performers overestimate their performance or relative standing on a task. One proposed explanation is that the skills needed to answer correctly also help people recognize when they are wrong.

An economic bubble, also known as an asset-price bubble, occurs when an asset’s price rises above a reasonable estimate of its underlying value, often because buyers expect to sell it to someone else for even more. Identifying one in a real market is difficult: people can disagree about what an asset is worth.

The efficient market hypothesis (EMH) proposes that asset prices incorporate a specified set of available information. The central issue is whether that information can still be used to earn returns beyond the appropriate risk-adjusted benchmark.

Effort justification is the tendency to value something more because we worked or sacrificed for it. A difficult hobby, for example, may feel especially worthwhile after we have poured time and money into it.

Egocentric bias is undue reliance on one’s own perspective when judging a shared situation. One studied form concerns responsibility: people may recall their own contributions more readily and assign themselves more credit or responsibility than others assign them.

Elimination by aspects is Amos Tversky’s model of choosing by successively removing options. Select a feature, discard the options that lack it, then repeat until one remains.

An empathy gap is difficulty judging how a different emotional or bodily state will affect preferences and behavior. The hot–cold empathy gap can concern your future self or another person.

The endowment effect is the tendency to value something more once it is yours. The same mug can look like a $2 purchase to a buyer and a $5 possession to its owner.

Escalation of commitment means continuing or increasing an investment after unfavorable feedback. The problem is not persistence itself. It is letting your involvement in a past decision drive what you do next, even when the prospects no longer justify it.

Ethnocentrism is the tendency to use one’s own ethnic or cultural group as the reference point for understanding and evaluating other groups.

Expectancy theory explains motivation in terms of the outcomes people expect and how much they value them. Associated with Victor Vroom, it asks why a person might put effort into one task and little into another.

Expectation bias describes ways prior beliefs can shape attention, interpretation or measurement. You expect a result, and ambiguous evidence starts to look like confirmation.

Experimenter bias occurs when a researcher’s expectations influence how a study is conducted, observed, or interpreted. One important form is the experimenter expectancy effect: expectations influence interactions with participants or animals and may affect the measured response.

Explicit bias is a consciously accessible evaluative attitude or belief that a person can report. In social-group research, it can include openly endorsed prejudiced beliefs. Being explicit does not mean that every action influenced by the attitude was carefully planned.

Extension neglect occurs when an evaluation gives too little weight to a relevant quantity, such as the size of a group, the scope of a benefit, or the duration of an experience. It does not simply mean underestimating how many objects are present.

Extrinsic intrinsic bias, usually called extrinsic incentives bias, concerns how we explain other people's motivation. We may give external rewards, such as money or recognition, more weight in their decisions than in our own, while giving interest and personal satisfaction less weight.

The fading affect bias (FAB) is the tendency for unpleasant feelings associated with autobiographical memories to diminish faster than pleasant feelings associated with those memories.

The fallacy of composition is assuming, without adequate justification, that a property of parts also belongs to the whole they form. The Internet Encyclopedia of Philosophy distinguishes this from division, which incorrectly moves from the whole to its parts.

The false consensus effect is the tendency to judge your own choices or opinions as more common than people with different choices or opinions judge them to be. It is often described as overestimating how widely your views are shared.

False uniqueness bias, also called the false uniqueness effect, means underestimating how many other people share your abilities, qualities or behavior. Something you regard as rare in yourself may be more common than you think.

Familiarity bias is a broad label for giving extra weight to options because they are known or recognizable. Familiarity can be useful when it reflects reliable experience; it becomes a source of error when it substitutes for evidence about an option's merits.

Fast-and-frugal heuristics are decision rules that use limited information and computation. They specify where to look for information, when to stop looking and how to decide.

A framing effect occurs when different presentations of equivalent information change judgments or choices. This differs from providing new substantive information that reasonably changes a decision.

The fundamental attribution error gives too much weight to personal dispositions and too little to situations. Correspondence bias is a closely overlapping term.

The gambler’s fallacy is the belief that a run of one outcome makes the opposite outcome due. It is a mistake when the events are independent and their probabilities have not changed.

Group attribution error is the tendency to infer group members' attitudes from a collective decision without giving enough weight to how the decision was made. A majority vote, a veto, or unequal influence can produce a decision that some members oppose.

The halo effect occurs when an overall impression shapes judgments of a person's or thing's particular qualities. Someone makes a good impression, and suddenly their unrelated qualities look better too. An attractive person may seem more intelligent or capable, even when you have learned nothing about their intelligence or ability.

The hard-easy effect is a pattern in confidence judgments: people tend to be overconfident on harder question sets and underconfident on easier ones. Their confidence exceeds their accuracy on the hard questions and falls below it on the easy questions.

Hedonic adaptation is a decline in the emotional or well-being impact of a change as we get used to it. A new purchase can be exciting at first and ordinary a few months later. That does not mean everyone returns quickly to a fixed level of happiness after every major life event.

A heuristic is a shortcut for making a judgment or decision without examining every relevant detail. A traveler might judge the risk of flying by how easily plane-crash stories come to mind. Someone choosing a restaurant might stop searching as soon as one meets their requirements. Both simplify a decision. Whether the shortcut works depends on the task and the information it uses.

Hindsight bias is the tendency for a known outcome to seem more predictable than it did beforehand. It is the “knew-it-all-along” effect. Once you know how the story ends, the clues can look obvious.

The horn effect, also called the horns effect, is a negative halo effect: an unfavorable overall impression carries over into judgments of a person's other qualities. You dislike one aspect of someone, and unrelated aspects start looking worse too.

Hostile attribution bias, also called hostile attributional bias, is the tendency to read harmful or aggressive intent into another person's actions when the intent is ambiguous. Someone bumps into you on a crowded street, and you assume they did it deliberately. The bias lies in inferring hostility beyond what the evidence supports, not in recognizing a clear threat.

The hostile media effect is the tendency for committed partisans to see the same news coverage as unfairly hostile to their own side.

The hot-hand fallacy is an unjustified belief that a recent run of success makes further success more likely. The important word is “unjustified.” Some processes have genuinely changing probabilities; others do not.

The house money effect is a greater willingness to take risks after a gain. Earlier winnings feel more expendable than money already counted as your own. The name comes from gambling: a player treats chips won from the casino as “house money.”

Hyperbolic discounting is a pattern in how delayed rewards lose value: the discount rate declines as the delay grows. A week's wait can matter much more when the reward is available now than when both options are months away.

The IKEA effect is the tendency for people to place disproportionately high value on products they partially created. A box you assembled yourself can feel worth more than the same box assembled by someone else. The work becomes part of how you value the result.

The illusion of control is the tendency to overestimate how much your actions influence an outcome. Choosing a lottery ticket yourself can feel different from receiving one at random, even though the choice does not improve its chance of winning.

The illusion of explanatory depth is the tendency to believe that you understand how something works more fully than you can actually explain. Attempting a detailed causal explanation can reveal gaps that were not apparent when you simply judged your understanding.

The illusion of transparency is the tendency to overestimate how clearly other people can read your thoughts, feelings, or intentions.

The illusion of validity is unwarranted confidence in a prediction because the available information forms a convincing match with the predicted outcome, even when that information has limited predictive value.

An illusory correlation is a perceived relationship that is absent or weaker than a person believes. Salient examples can make two events seem linked even when the full pattern of observations does not justify that conclusion.

Illusory superiority, or the better-than-average effect, is the tendency to rate oneself more favorably than other people on a trait or ability.

The illusory truth effect is the tendency to rate repeated statements as more true than comparable new statements. Familiarity can influence a truth judgment even when repetition supplies no new evidence.

Impact bias is the tendency to overestimate the intensity or duration of an emotional response to a future event. It is an error in predicting feelings, not evidence that the event itself is unimportant.

Implicit bias concerns evaluative associations or stereotypes assessed without relying only on a person’s direct report of their beliefs. It is part of the research tradition of implicit social cognition (Greenwald and Banaji, 1995). Indirect measurement does not automatically establish that a person is completely unaware of an association or that it causes a particular action.

In behavioral economics, inertia is the persistence of an existing action or choice. It can reflect habit, limited attention, switching costs, or a preference for the status quo.

Information aversion is reluctance to learn information that is expected to be unpleasant or otherwise unwanted. It overlaps with information avoidance; the ostrich effect describes a related pattern of avoiding potentially unfavorable information, rather than every possible reason to reject information.

Information avoidance is behavior intended to prevent or delay learning available information that may be unwanted. Sweeny and colleagues (2010) distinguish this from simply lacking access to information.

In judgment and decision-making, information bias is seeking or valuing information even when its possible answers would not change the decision. In Baron, Beattie and Hershey’s experiments (1988), participants valued diagnostic questions even when no answer would change the hypothesis used as a basis for action.

Ingroup bias is preferential evaluation or treatment of people identified as members of one's own group. It can appear in judgments, trust, or allocation of resources.

Intentionality bias is a tendency to interpret ambiguous human actions as deliberate. An observer may infer purpose before considering an accident or another explanation. It does not mean that people always see every action as intentional.

Intertemporal choice involves outcomes at different times. Examples include allocating a budget between present and later use, or choosing when to complete a task with both immediate and future consequences.

The introspection illusion is the tendency to give too much weight to one’s own thoughts and intentions, relative to observable behavior, when explaining oneself—while relying more on behavior when judging other people. Access to a conscious thought does not necessarily reveal the process that caused a judgment.

The just world fallacy is the belief that the world is just and that people generally get what they deserve. This belief can lead people to blame victims for their own suffering, and to believe that they would not experience the same hardships if they were in the same situation.

The law of the instrument is the tendency to reach for a familiar tool or method even when it does not fit the problem. It is also known as Maslow’s hammer or the golden hammer.

The less-is-better effect occurs when an option with less of a desirable attribute receives a higher evaluation than an option with more, especially when the options are judged separately. It is not a general preference for simplicity or fewer choices.

Limited attention means we cannot attend to everything available to us. A person focused on one task can miss information that matters to another.

Linguistic intergroup bias is the tendency to describe favorable ingroup behavior and unfavorable outgroup behavior in more abstract terms.

Loss aversion is the hypothesis that a loss relative to a reference point can receive more subjective weight than an equivalent gain. It is part of Kahneman and Tversky’s prospect theory (1979) and the reference-dependent model of Tversky and Kahneman (1991). The reference point matters: the same outcome can be described as a gain or a loss relative to different starting points.

A lottery allocates a prize by chance. In a behavior-change program, eligibility for a draw can depend on completing a specified action. This arrangement should be distinguished from a commercial lottery in which people buy tickets.

Mental accounting describes how people organize and evaluate financial activity. Thaler (1999) includes how outcomes are perceived, how money and spending are assigned to categories, and how broadly or frequently accounts are reviewed.

Mental budgeting is the allocation of resources to categories and the tracking of expenses against those categories. It is one part of the broader concept of mental accounting.

A mental set is a readiness to approach a problem using a familiar representation or strategy. It can make a familiar task efficient. The Einstellung effect refers to the obstructive case, when an initially available solution prevents a better one from being found.

The mere exposure effect is the tendency for repeated exposure to a stimulus to increase liking for it, under some conditions. Zajonc’s original research (1968) included unfamiliar words and symbols.

The misinformation effect occurs when misleading information received after an event affects later reports or memory of that event.

Mood-congruent memory bias is a tendency for memory to favor content whose emotional tone matches a past or current mood. A sad mood may favor sad recollections; a happy mood may favor pleasant ones.

Moral hazard is an incentive problem that can arise when one party’s actions affect another party’s outcomes and those actions are difficult to observe or contract on. It includes choices about effort and prevention, not only deliberate risk-taking.

Myopic loss aversion combines sensitivity to losses with frequent evaluation of outcomes. Even someone with a long planning horizon may evaluate gains and losses over short intervals.

Myopic procrastination means putting off a task because the discomfort of starting now feels more important than the consequences of waiting. Tomorrow looks like a better time to begin. Then tomorrow arrives, and starting still feels unpleasant.

Myside bias is the tendency to evaluate evidence, generate arguments, or test hypotheses in ways that favor one’s existing opinions. It overlaps with confirmation bias but specifically emphasizes the person’s own position. It need not involve personal financial gain or conscious dishonesty.

Naïve allocation, or naïve diversification, means using a simple rule such as splitting resources equally across the options offered. An equal split across n options is often written as the 1/n rule: each option receives one nth of the total. The allocation can then depend on how the menu is divided, rather than only on the underlying assets or the person’s aims.

The narrative fallacy is treating a coherent story as sufficient evidence for an explanation. A story can connect events neatly while leaving out facts that do not fit, or adding causal links the evidence never established.

Negativity bias refers to patterns in which negative information has greater influence than comparable positive information. The relevant comparison must be defined for the task, such as attention, evaluation or memory.

Normalcy bias is a disputed label for underestimating a warning because conditions are expected to remain normal. A failure to prepare or evacuate does not, by itself, establish the bias.

Observer bias occurs when an assessor's expectations or knowledge affect how observations are measured, classified or interpreted. For example, knowledge of treatment assignment could influence a subjective outcome rating.

Omission bias is a tendency to judge harm caused by an action more harshly than comparable harm caused by inaction, even when relevant consequences and intentions are held constant.

Opportunity cost neglect occurs when a decision gives too little attention to what must be given up: other uses of the same money, time or resources.

Optimism bias, also called optimistic bias, is an expectation that is more favorable than an appropriate comparison warrants. It can concern one's absolute chances of an event or one's chances compared with other people.

The ostrich effect is selective avoidance of information when someone expects unpleasant news. The name comes from the mistaken belief that ostriches bury their heads in the sand to avoid danger. In financial research, it describes reduced attention to account information after indications that markets are doing poorly. Avoidance need not involve believing that ignoring a problem makes it disappear; people may wish to avoid the distress of learning more.

Outcome bias is judging the quality of a decision too heavily by how it turned out, while overlooking the information and circumstances at the time of the choice.

Outgroup homogeneity bias is the tendency to perceive members of another group as more alike than members of one’s own group. Demonstrating a relative perception does not by itself establish how much diversity either group actually has.

The overconfidence effect, often called overconfidence bias, is a mismatch between a person’s confidence and an appropriate measure of accuracy or performance. Moore and Healy (2008) distinguish three forms: overestimation of one’s performance, overplacement relative to other people, and overprecision in one’s beliefs.

The pain of paying is the unpleasant feeling associated with spending money. It can affect purchase decisions and enjoyment of what is bought.

The paradox of choice is the idea, popularized by Barry Schwartz's 2004 book The Paradox of Choice: Why More Is Less, that a larger set of options can sometimes make choosing harder or reduce satisfaction. The related research question is called choice overload.

The paradox of value, also called the diamond-water paradox or value paradox, asks why something essential, such as water, can have a lower exchange price than something less necessary, such as a diamond.

Pareidolia is perceiving a recognizable form in an ambiguous pattern, such as a face in a cloud or wood grain. The resemblance is experienced even though the pattern is not the object it appears to depict.

Partisan bias is the tendency for political loyalties to shape how people seek, judge, remember, or explain information.

Partitioning divides a resource, set of options, or information into separate units. In behavioral research, the effect depends on what is divided and what decisions the divisions create.

The peak-end rule describes a pattern in retrospective evaluation: the most intense part and the ending of an episode can receive disproportionate weight compared with its duration and other moments.

The Peltzman effect, also called the offset hypothesis, is the hypothesis that people may change their behavior when safety improves, potentially offsetting part of the expected benefit. It is named for Peltzman’s 1975 analysis of automobile safety regulation.

A perceptual set is a readiness to interpret sensory information in a particular way, influenced by expectations or prior learning.

Pessimism bias means expecting outcomes to be worse than the available evidence warrants, such as overestimating an adverse event’s probability or underestimating a favorable one. A negative forecast is not necessarily biased: it can be accurate. Demonstrating bias requires a suitable comparison, such as observed frequencies or a well-supported probability estimate.

The picture superiority effect is better memory for pictures than corresponding words under many experimental conditions. It is a comparative memory finding, not inherently an error or cognitive bias. The effect is commonly tested using pictures of objects and their matching verbal labels.

Placement bias is a broad label for changes in attention, evaluation, or choice associated with where options appear. Different position effects can have different causes. There is no single position that reliably produces the same preference in every display.

The planning fallacy describes overly optimistic predictions about how long one’s task will take, particularly when those predictions give too little weight to relevant past experience. The term is also used more broadly for underestimated project demands.

Plant blindness is a term for giving plants less attention, recognition or interest than animals. It refers to a disparity in awareness, not a literal inability to see plants. Related issues include limited knowledge of plants’ ecological roles and treating plants as background scenery.

A preference is a relative ranking of options. Preferences can reflect what a person wants and the tradeoffs they face, but the way a question is asked can also affect the ranking.

Preference reversal occurs when two procedures or situations produce opposite rankings of the same options. The term is especially associated with a difference between choosing an option and assigning it a monetary value.

Present bias is extra weight placed on immediate costs or rewards relative to future ones. It can help explain why a planned choice changes when a temptation becomes immediate or it is time to make an effort. It is more specific than simply preferring an earlier reward.

In research on information-security spending, prevention bias is a preference for measures that prevent an incident over measures that detect and respond to it, even when the options offer the same expected return. The bias concerns how a protective budget is divided, not simply preferring to avoid losses rather than obtain gains.

The primacy effect is an advantage for information presented early in a sequence. In free-recall memory tasks, it means better recall of the first items than of many middle items. The term is also used for greater influence of early information on judgments, which is a separate outcome from recall.

A principal-agent problem can arise when a person or organization delegates an action to another party whose interests differ, especially when relevant information or actions are difficult to observe. The delegating party is the principal; the acting party is the agent.

Pro-innovation bias is the assumption that an innovation ought to spread widely and quickly, with too little consideration of whether people should reject, change, or stop using it. In diffusion research, Rogers used the term to criticize treating adoption as desirable in itself.

Probability matching is a decision-making strategy often seen in situations where individuals are tasked with predicting outcomes over a series of trials. Rather than favoring the outcome with the highest probability, an individual employing probability matching will choose outcomes in proportion to the likelihood of those outcomes occurring.

Probability weighting describes how probabilities contribute to the value assigned to uncertain options in a decision model. A decision weight is not necessarily a belief about how likely an event is.

Projection bias is a forecasting error in which people expect their future preferences to resemble their current preferences too closely. They may anticipate the direction of a change while underestimating its size.

Proportionality bias is the tendency to expect a major event to have a correspondingly major cause. The scale of an outcome can make an elaborate explanation feel more plausible even when the evidence for that explanation has not improved.

Prospect theory is a descriptive model of decisions under risk, introduced by Daniel Kahneman and Amos Tversky in 1979. It evaluates outcomes as gains or losses relative to a reference point and provides an alternative to expected utility theory for explaining certain observed choices.

Publication bias is the selective availability of studies according to their results. Missing studies can make an intervention look more effective or dependable than the full evidence supports.

Puritanical bias is a critical label for moral disapproval of pleasure or praise of self-denial simply because an activity is difficult or unpleasant. It is not a standardized psychological diagnosis or a single established experimental effect.

Quasi-hyperbolic discounting is a model of time preference that gives an additional weight advantage to the present. Laibson (1997) used it to analyze dynamically inconsistent preferences and commitment.

Ratio bias is a tendency to let the number of favorable outcomes influence a probability judgment or choice without adequately considering the total number of possible outcomes. The numerator can become more compelling than the proportion.

Reactive devaluation is judging a proposal less favorably because it is attributed to an adversary. It is studied by comparing evaluations while holding the proposal itself constant.

Recall bias is systematic error in reports of past events caused by how those events are remembered or reconstructed.

The recency effect is an advantage in recall for recently presented information. If someone hears a list of ten words and immediately recalls them in any order, the last few words are often easier to remember than words in the middle. Giving disproportionate weight to recent information in a judgment is often called recency bias. Remembering an item and giving it more weight are different outcomes.

The recognition heuristic uses recognition to infer which of two alternatives has a higher value on a specified criterion. When one alternative is recognized and the other is not, the rule favors the recognized alternative.

Reference dependence means that the value assigned to an outcome depends on a comparison level, such as the current situation or an expectation. Outcomes are evaluated as changes relative to that level.

A reference point is a comparison level used to evaluate an outcome. In prospect theory, it separates outcomes treated as gains from those treated as losses. It may reflect the current situation, an expectation, or how the decision is presented.

In judgment and memory research, regressive bias describes estimates pulled toward less extreme values: low quantities may be overestimated and high quantities underestimated.

Regret aversion is a tendency to choose in ways that avoid anticipated regret: the feeling that another choice would have produced a better outcome.

The representativeness heuristic uses similarity to judge likelihood: an outcome seems more probable when it resembles a category or generating process.

In questionnaire research, response bias is a systematic influence on answers that is separate from the specific characteristic an item is intended to measure. It can distort survey scores and relationships between measures without requiring deliberate dishonesty.

Restraint bias is overestimating your ability to resist temptation. You think the snacks on your desk will be easy to ignore. A few hours later, the bag is empty.

Risk-as-feelings theory explains how present emotions can affect responses to risk. A person may judge an activity safe but feel too afraid to do it.

Risk aversion means preferring a certain amount to a gamble with the same expected monetary value. Risk tolerance describes how willing someone is to accept risk.

Risk compensation is the idea that feeling safer can lead people to take more risks. A driver might take more chances after a safety improvement because they feel better protected.

Rosy retrospection is remembering an experience more positively than you rated it while it was happening. The holiday looks better in the rearview mirror.

Salience bias is giving extra weight to information because it stands out. The brightest or loudest thing in front of you is not necessarily the most useful thing to consider.

Sampling bias happens when the people or cases in a study differ in relevant ways from the population its findings are meant to describe.

Satisficing means choosing an option that meets your requirements instead of searching for the best possible option. Herbert Simon used it in his account of bounded rationality: people have limited time, information, and capacity to compare choices.

The scarcity heuristic is using limited availability as a clue to value. An item can seem more desirable when there are only a few left.

Selection bias happens when the way observations enter or stay in an analysis distorts the result. Who gets studied matters, but so does who drops out or gets left out later.

Self-report bias is systematic error in reports of one’s own behavior, characteristics, beliefs, or experiences.

Self-serving attribution bias is the tendency to explain positive outcomes more favorably for yourself than negative ones. A good test result shows how smart you are. A bad one shows how unfair the test was.

The Semmelweis reflex is an informal label for dismissing new evidence because it conflicts with an established belief.

The serial position effect describes how an item's position in a list affects the chance of remembering it. People often recall items at the beginning and end better than those in the middle.

Shared information bias, also called common information bias, is the tendency for groups to discuss information several members already know more than information held by only one or a few members.

The similar-to-me bias is a tendency to judge someone more favorably because they seem similar to you. Related research on similarity and attraction examines who we like.

The simulation heuristic is a mental shortcut in which people judge an outcome partly by how easily they can construct a sequence of events that produces it. It can shape judgments about what might happen and what could have happened differently.

Social desirability bias is a form of response bias in which reports shift toward what seems socially acceptable or favorable. It can affect surveys and other measures that ask people to describe themselves.

The spacing effect is better later retention when learning opportunities are spread apart rather than packed together. The comparison concerns the schedule, not simply spending more time studying.

The spotlight effect is overestimating how much other people notice your appearance or actions. You may feel as though you are under a spotlight while others are paying less attention than you think.

Status quo bias is a disproportionate preference for an option because it is the current or previous choice. Samuelson and Zeckhauser found that labeling an option as the status quo increased its selection while the alternatives stayed the same.

The subadditivity effect occurs when the judged probability of a category is lower than the sum of the judged probabilities of its separate parts.

The sunk cost fallacy is letting an unrecoverable past investment determine whether to continue, instead of comparing what the available choices will cost or provide from now on.

Survivorship bias occurs when conclusions depend on the cases that remain visible while relevant cases that disappeared are left out. It is a form of selection bias.

System One, often written System 1, is a common label for relatively automatic mental processing. It supplies responses without the same working-memory demands as deliberate reasoning.

The take the best heuristic compares two alternatives by checking cues in order of predictive validity. It stops at the first cue that distinguishes them and uses that cue to make the inference.

The telescoping effect, also called time telescoping, is misremembering when an event occurred. Forward telescoping places it more recently than it happened. Backward telescoping places it farther in the past.

Time discounting, also called temporal discounting, describes how an outcome's timing affects its value in a present choice. It is often studied by comparing a smaller reward sooner with a larger reward later.

The tip of the tongue phenomenon is the frustrating feeling that you know a word or name but cannot retrieve it. The answer seems almost available—just not available enough to say.

Truth bias is a tendency to judge communication as honest, often unless something prompts suspicion. It helps ordinary communication proceed, while also leaving room for deception.

Unit bias is the proposed tendency to treat one presented unit as an appropriate amount to take or consume. Packaging, segmentation, or a serving utensil can help define the unit. One unit can feel like the right amount even when units differ in size.

Utility represents the value of outcomes in an economic model. In choice-based accounts, it represents preferences. It is not automatically a direct measure of pleasure or well-being.

The Utility Expectation Model (UEM) is Timothy Gohmann's label for a proposed account of the mental processes behind choices. His 2015 essay in the Behavioral Economics Guide combines decision processes, individual characteristics, situational influences, and feedback from experienced outcomes.

The winner's curse is a risk in common-value auctions, where bidders estimate an uncertain value that is substantially shared. The highest estimate is more likely to be too optimistic. Winning therefore tells the bidder something about their estimate.

The worse-than-average effect, also called the below-average effect, is a tendency to judge one's ability or performance as worse than a comparison group's, particularly on difficult tasks.

The zero price effect is an increase in an offer's appeal when its price becomes free, beyond the response expected from a comparable small reduction above zero. It is also called the free effect or freebie effect.

Zero-risk bias is a preference for eliminating one risk completely over an alternative that would reduce more overall harm, when the relevant costs and consequences are otherwise comparable. The distinctive attraction is reaching zero, rather than achieving the larger total reduction.