A Short List of Cognitive Biases With Short Descriptions

The Ambiguity Effect is a cognitive bias where decision making is affected by a lack of information, or "ambiguity". The effect implies that people tend to select options for which the probability of a favorable outcome is known, over an option for which the probability of a favorable outcome is unknown.
One possible explanation of the effect is that people have a rule of thumb (heuristic) to avoid options where information is missing. This will often lead them to seek out the missing information. In many cases, though, the information cannot be obtained. The effect is often the result of calling some particular missing piece of information to the person's attention.

Anchoring is a cognitive bias where an individual depends too heavily on an initial piece of information offered when making decisions. Anchoring occurs when, during decision making, an individual depends on an initial piece of information to make subsequent judgments.

The Focusing Effect is a cognitive bias that occurs when a person places too much importance or emphasis on a selected detail rather than considering the "larger picture" - this can lead to errors in predicting a future outcome. By emphasizing the importance of a very obvious detail sometimes the small factors (which can be just as important) are ignored making the actual result different from a predicted result.

Attentional Bias is the tendency for people's perception to be affected by their recurring thoughts at the time. Attentional biases may explain an individual's failure to consider alternative possibilities, as specific thoughts guide the train of thought in a certain manner. Attentional bias has also been associated with clinically relevant symptoms such as anxiety and depression.

The Availability Heuristic is a mental shortcut that relies on immediate examples that come to a given person's mind when evaluating a specific topic, concept, method or decision. The availability heuristic operates on the notion that if something can be recalled, it must be important, or at least more important than alternative solutions which are not as readily recalled. Subsequently, under the availability heuristic, people tend to heavily weigh their judgments toward more recent information, making new opinions biased toward that latest news. The availability of consequences associated with an action is positively related to perceptions of the magnitude of the consequences of that action. In other words, the easier it is to recall the consequences of something the greater those consequences are often perceived to be. Most notably, people often rely on the content of their recall if its implications are not called into question by the difficulty that they experience in bringing the relevant material to mind.

Confirmation Bias is the tendency to search for, interpret, favor, and recall information in a way that affirms one's prior beliefs or hypotheses. It is a type of cognitive bias and a systematic error of inductive reasoning. People display this bias when they gather or remember information selectively, or when they interpret it in a biased way. The effect is stronger for desired outcomes, emotionally charged issues, and for deeply entrenched-beliefs.

The Bandwagon Effect is a phenomenon whereby the rate of uptake of beliefs, ideas, fads and trends increases the more that they have already been adopted by others. In other words, the bandwagon effect is characterized by the probability of individual adoption increasing with respect to the proportion who have already done so. As more people come to believe in something, others also "hop on the bandwagon" regardless of the underlying evidence.

Belief Bias is the tendency to judge the strength of arguments based on the plausibility of their conclusion rather than how strongly they support that conclusion. A person is more likely to accept an argument that supports a conclusion that aligns with his values, beliefs and prior knowledge, while rejecting counter arguments to the conclusion. Belief bias is an extremely common and therefore significant form of error; we can easily be blinded by our beliefs and reach the wrong conclusion. Belief bias has been found to influence various reasoning tasks, including conditional reasoning, relation reasoning and transitive reasoning.

The Ben Franklin Effect is a proposed psychological phenomenon: a person who has already performed a favor for another is more likely to do another favor for the other than if they had received a favor from that person. An explanation for this is cognitive dissonance. People reason that they help others because they like them, even if they do not, because their minds struggle to maintain logical consistency between their actions and perceptions. The Benjamin Franklin effect, in other words, is the result of one's concept of self coming under attack. Every person develops a persona, and that persona persists because inconsistencies in one's personal narrative get rewritten, redacted, and misinterpreted.

The Bias Blind Spot is the cognitive bias of recognizing the impact of biases on the judgment of others, while failing to see the impact of biases on one's own judgment. The bias blind spot is named after the visual blind spot. The bias blind spot appears to be a true blind spot in that it is unrelated to actual decision making ability. Performance on indices of decision making competence are not related to individual differences in bias blind spot. In other words, everyone seems to think they are less biased than other people, regardless of their actual decision making ability.

Choice-Supportive Bias or is the tendency to retroactively ascribe positive attributes to an option one has selected and/or to demote the forgone options. It is part of Cognitive science, and is a distinct cognitive bias that occurs once a decision is made. For example, if a person chooses option A instead of option B, they are likely to ignore or downplay the faults of option A while amplifying or subscribing new negative faults to option B. Conversely, they are also likely to notice and amplify the advantages of option A and not notice or de-emphasize those of option B. What is remembered about a decision can be as important as the decision itself, especially in determining how much regret or satisfaction one experiences. Research indicates that the process of making and remembering choices yields memories that tend to be distorted in predictable ways.

The Clustering Illusion is the tendency to erroneously consider the inevitable "streaks" or "clusters" arising in small samples from random distributions to be non-random. The illusion is caused by a human tendency to underpredict the amount of variability likely to appear in a small sample of random or semi-random data. Using this cognitive bias in causal reasoning may result in the Texas sharpshooter fallacy. More general forms of erroneous pattern recognition are pareidolia and apophenia. Related biases are the illusion of control which the clustering illusion could contribute to, and insensitivity to sample size in which people don't expect greater variation in smaller samples. A different cognitive bias involving misunderstanding of chance streams is the gambler's fallacy.

Compassion Fade is a cognitive bias that predisposes people to behave more compassionately towards a small number of identifiable victims than to a large number of anonymous ones.

Conservatism bias is a bias in human information processing, which refers to the tendency to revise one's belief insufficiently when presented with new evidence. This bias describes human belief revision in which persons over-weigh the prior distribution (base rate) and under-weigh new sample evidence when compared to Bayesian belief-revision.

The Curse of Knowledge is a cognitive bias that occurs when an individual, communicating with other individuals, unknowingly assumes that the others have the background to understand. For example, in a classroom setting, teachers have difficulty teaching novices because they cannot put themselves in the position of the student. A brilliant professor might no longer remember the difficulties that a young student encounters when learning a new subject. This curse of knowledge also explains the danger behind thinking about student learning based on what appears best to faculty members, as opposed to what has been verified with students.

Distinction Bias, a concept of decision theory, is the tendency to view two options as more distinctive when evaluating them simultaneously than when evaluating them separately. The concept of the distinction bias was advanced by Christopher K. Hsee and Jiao Zhang of the University of Chicago as an explanation for differences in evaluations of options between joint evaluation mode and separate evaluation mode. Evaluation mode is a contextual feature in decision making. Joint evaluation mode is when options are evaluated simultaneously, and separate evaluation mode is when each option is evaluated in isolation. Research shows that evaluation mode affects the evaluation of options, such that options presented simultaneously are evaluated differently from the same options presented separately.

Duration Neglect is the psychological observation that people's judgments of the unpleasantness of painful experiences depend very little on the duration of those experiences. Multiple experiments have found that these judgments tend to be affected by two factors: the peak (when the experience was the most painful) and how quickly the pain diminishes. If it diminishes more slowly, the experience is judged to be more painful. Hence, the term "peak–end rule" describes this process of evaluation. Duration neglect is a specific form of the more general extension neglect.

The End-of-History Illusion is a psychological illusion in which individuals of all ages believe that they have experienced significant personal growth and changes in tastes up to the present moment, but will not substantially grow or mature in the future. Despite recognizing that their perceptions have evolved, individuals predict that their perceptions will remain roughly the same in the future. The illusion is based on the fact that at any given developmental stage, an individual can observe a relatively low level of maturity in previous stages. The phenomenon affects teenagers, middle-aged individuals, and seniors. In general, people tend to see significant changes in hindsight, but fail to predict that these changes will continue. For example, a 20-year-old's prediction of how great a change they will undergo in the next ten years will not be as extreme as a 30-year-old's recollection of the changes they underwent between the ages of 20 and 30. The same phenomenon is true for people of any age.

The Baader–Meinhof Effect, also known as frequency illusion, is the illusion in which a word, a name, or other thing that has recently come to one's attention suddenly seems to appear with improbable frequency shortly afterwards (not to be confused with the recency illusion or selection bias. The Baader–Meinhof phenomenon occurs because the human brain has a prejudice towards patterns. When the brain detects that an element of information appears more than once, the brain uses the repetitions to form a possible sequence, meanwhile dismissing everything that is not repeating as irrelevant information.

Functional Fixedness is a cognitive bias that limits a person to use an object only in the way it is traditionally used. The concept of functional fixedness originated in Gestalt psychology, a movement in psychology that emphasizes holistic processing. Karl Duncker defined functional fixedness as being a "mental block against using an object in a new way that is required to solve a problem". This "block" limits the ability of an individual to use components given to them to complete a task, as they cannot move past the original purpose of those components.

Groupthink is a psychological phenomenon that occurs within a group of people in which the desire for harmony or conformity in the group results in an irrational or dysfunctional decision-making outcome. Group members try to minimize conflict and reach a consensus decision without critical evaluation of alternative viewpoints by actively suppressing dissenting viewpoints, and by isolating themselves from outside influences. Groupthink requires individuals to avoid raising controversial issues or alternative solutions, and there is loss of individual creativity, uniqueness and independent thinking. The dysfunctional group dynamics of the "ingroup" produces an "illusion of invulnerability" (an inflated certainty that the right decision has been made). Thus the "ingroup" significantly overrates its own abilities in decision-making and significantly underrates the abilities of its opponents (the "outgroup"). Furthermore, groupthink can produce dehumanizing actions against the "outgroup".

The Hard–Easy Effect is a cognitive bias that manifests itself as a tendency to overestimate the probability of one's success at a task perceived as hard, and to underestimate the likelihood of one's success at a task perceived as easy. The hard-easy effect takes place, for example, when individuals exhibit a degree of underconfidence in answering relatively easy questions and a degree of overconfidence in answering relatively difficult questions. "Hard tasks tend to produce overconfidence but worse-than-average perceptions, whereas easy tasks tend to produce underconfidence and better-than-average effects."

Hindsight Bias, also known as the knew-it-all-along phenomenon or creeping determinism, refers to the common tendency for people to perceive events that have already occurred as having been more predictable than they actually were before the events took place. As a result, people often believe, after an event has occurred, that they would have predicted, or perhaps even would have known with a high degree of certainty, what the outcome of the event would have been, before the event occurred. Hindsight bias may cause distortions of our memories of what we knew and/or believed before an event occurred, and is a significant source of overconfidence regarding our ability to predict the outcomes of future events.

The Illusion of Control is the tendency for people to overestimate their ability to control events; for example, it occurs when someone feels a sense of control over outcomes that they demonstrably do not influence. The illusion might arise because people lack direct introspective insight into whether they are in control of events. This has been called the introspection illusion. Instead they may judge their degree of control by a process that is often unreliable. As a result, they see themselves as responsible for events when there is little or no causal link.

Illusion of Validity is a cognitive bias in which a person overestimates their ability to interpret and predict accurately the outcome when analyzing a set of data, in particular when the data analyzed show a very consistent pattern—that is, when the data "tell" a coherent story. This effect persists even when the person is aware of all the factors that limit the accuracy of his or her predictions, that is when the data and/or methods used to judge them lead to highly fallible predictions.

In psychology, illusory correlation is the phenomenon of perceiving a relationship between variables (typically people, events, or behaviors) even when no such relationship exists. A false association may be formed because rare or novel occurrences are more salient and therefore tend to capture one's attention. This phenomenon is one way stereotypes form and endure. A parallel effect occurs when people judge whether two events, such as pain and bad weather, are correlated. They rely heavily on the relatively small number of cases where the two events occur together. People pay relatively little attention to the other kinds of observation (of no pain or good weather).

The Illusory Truth Effect is the tendency to believe information to be correct after repeated exposure. When truth is assessed, people rely on whether the information is in line with their understanding or if it feels familiar. The first condition is logical as people compare new information with what they already know to be true. Repetition makes statements easier to process relative to new, unrepeated statements, leading people to believe that the repeated conclusion is more truthful. The illusory truth effect has also been linked to "hindsight bias", in which the recollection of confidence is skewed after the truth has been received.

In cognitive psychology and decision theory, loss aversion refers to people's tendency to prefer avoiding losses to acquiring equivalent gains: it is better to not lose $5 than to find $5. The principle is very prominent in the domain of economics. What distinguishes loss aversion from risk aversion is that the utility of a monetary payoff depends on what was previously experienced or was expected to happen. Some studies have suggested that losses are twice as powerful, psychologically, as gains.

The Mere-Exposure Effect is a psychological phenomenon by which people tend to develop a preference for things merely because they are familiar with them. In social psychology, this effect is sometimes called the familiarity principle. In studies of interpersonal attraction, the more often someone sees a person, the more pleasing and likeable they find that person.

Money illusion, or price illusion, is the tendency of people to think of currency in nominal, rather than real, terms. In other words, the face value (nominal value) of money is mistaken for its purchasing power (real value) at a previous point in time. Viewing purchasing power as measured by the nominal value is false, as modern fiat currencies have no intrinsic value and their real value depends purely on the price level.

Self-licensing (aka noble cause corruption, moral self-licensing, moral licensing, licensing effect, moral credential effect) is a term used in social psychology and marketing to describe the subconscious phenomenon whereby increased confidence and security in one's self-image or self-concept tends to make that individual worry less about the consequences of subsequent immoral behavior and, therefore, more likely to make immoral choices and act immorally. In simple terms, self-licensing occurs when people allow themselves to indulge after doing something positive first;

The Negativity Bias, also known as the negativity effect, is the notion that, even when of equal intensity, things of a more negative nature (e.g. unpleasant thoughts, emotions, or social interactions; harmful/traumatic events) have a greater effect on one's psychological state and processes than neutral or positive things. In other words, something very positive will generally have less of an impact on a person's behavior and cognition than something equally emotional but negative. The negativity bias has been investigated within many different domains, including the formation of impressions and general evaluations; attention, learning, and memory; and decision-making and risk considerations.

The Neglect of Probability, a type of cognitive bias, is the tendency to disregard probability when making a decision under uncertainty and is one simple way in which people regularly violate the normative rules for decision making. Small risks are typically either neglected entirely or hugely overrated. The continuum between the extremes is ignored. There are many related ways in which people violate the normative rules of decision making with regard to probability including the hindsight bias, the neglect of prior base rates effect, and the gambler's fallacy. However, this bias is different, in that, rather than incorrectly using probability, the actor disregards it.

Omission Bias is the tendency to favor an act of omission over one of commission. It can occur due to a number of processes, including psychological inertia, the perception of transaction costs, and a tendency to judge harmful actions as worse, or less moral, than equally harmful omissions (inactions). It is controversial as to whether omission bias is a cognitive bias or is often rational. The bias is often showcased through the trolley problem and has also been described as an explanation for the endowment effect and status quo bias.

Optimism Bias is a cognitive bias that causes someone to believe that they themselves are less likely to experience a negative event. It is also known as unrealistic optimism or comparative optimism.

The Outcome Bias is an error made in evaluating the quality of a decision when the outcome of that decision is already known. Specifically, the outcome effect occurs when the same "behavior produce[s] more ethical condemnation when it happen[s] to produce bad rather than good outcome, even if the outcome is determined by chance." While similar to the hindsight bias, the two phenomena are markedly different. The hindsight bias focuses on memory distortion to favor the actor, while the outcome bias focuses exclusively on weighting the past outcome heavier than other pieces of information in deciding if a past decision was correct.

The Overconfidence Effect is a well-established bias in which a person's subjective confidence their judgements is reliably greater than the objective accuracy of those judgements, especially when confidence is relatively high. Overconfidence is one example of a miscalibration of subjective probabilities. Throughout the research literature, overconfidence has been defined in three distinct ways: (overestimation of one's actual performance; overplacement of one's performance relative to others; and overprecision in expressing unwarranted certainty in the accuracy of one's beliefs.

Pareidolia is the tendency to interpret a vague stimulus as something known to the observer, such as seeing shapes in clouds, seeing faces in inanimate objects or abstract patterns, or hearing hidden messages in music.

The Pygmalion Effect, or Rosenthal effect, is the phenomenon whereby others' expectations of a target person affect the target person's performance. The effect is named after the Greek myth of Pygmalion, a sculptor who fell in love with a statue he had carved, or alternately, after the Rosenthal–Jacobson study. A corollary of the Pygmalion effect is the golem effect, in which low expectations lead to a decrease in performance; both effects are forms of self-fulfilling prophecy. By the Pygmalion effect, people internalize their positive labels, and those with positive labels succeed accordingly. The idea behind the Pygmalion effect is that increasing the leader's expectation of the follower's performance will result in better follower performance. Within sociology, the effect is often cited with regard to education and social class. The concept of stereotype threat could be considered to be the inverse of the Pygmalion effect, as it denotes a negative form of self-fulfilling prophecy.

The opposite of optimism bias is pessimism bias (or pessimistic bias), because the principles of the optimistic bias continue to be in effect in situations where individuals regard themselves as worse off than others. Optimism may occur from either a distortion of personal estimates, representing personal optimism, or a distortion for others, representing personal pessimism. Pessimism bias is an effect in which people exaggerate the likelihood that negative things will happen to them. It contrasts with optimism bias. The difference is that we are in an improbable way worried about our society's future.

The Planning Fallacy is a phenomenon in which predictions about how much time will be needed to complete a future task display an optimism bias and underestimate the time needed. This phenomenon sometimes occurs regardless of the individual's knowledge that past tasks of a similar nature have taken longer to complete than generally planned. The bias only affects predictions about one's own tasks; when outside observers predict task completion times, they show a pessimistic bias, overestimating the time needed. The planning fallacy requires that predictions of current tasks' completion times are more optimistic than the beliefs about past completion times for similar projects and that predictions of the current tasks' completion times are more optimistic than the actual time needed to complete the tasks.

Present Bias is the tendency to rather settle for a smaller present reward than to wait for a larger future reward, in a trade-off situation. It describes the trend of overvaluing immediate rewards, while putting less worth in long-term consequences. The present bias can be used as a measure for self-control, which is a trait related to the prediction of secure life outcomes.

Projection Bias is the tendency to falsely project current preferences onto a future event. When people are trying to estimate their emotional state in the future they attempt to give an unbiased estimate. However, people's assessments are contaminated by their current emotional state and thus it may be difficult for them to predict their emotional state in the future an occurrence known as mental contamination.

Reactive Devaluation is a cognitive bias that occurs when a proposal is devalued if it appears to originate from an antagonist. In a discussion, one’s opinion about a certain proposal is influenced by his opinion of the person suggested it. If we consider the person making the offer as an antagonist, we tend to value the proposal as being less interesting than if it was made by someone else. This cognitive bias is known as reactive devaluation and can affect your decisions as well as block your influence in conversations. It is frequently observed in all kinds of negotiations and can lead to sub-optimal outcomes for both parties since good ideas might be rejected just because of the people giving the ideas. Researchers have shown that the bias is a result of loss aversion, perceptions, preferences and attitude polarisation. To avoid this bias in negotiations, working with a third (neutral) party can be an effective solution.

Restraint Bias is the tendency for people to overestimate their ability to control impulsive behavior. An inflated self-control belief may lead to greater exposure to temptation, and increased impulsiveness. Therefore, the restraint bias has bearing on addiction.

Risk Compensation is a theory which suggests that people typically adjust their behavior in response to the perceived level of risk, becoming more careful where they sense greater risk and less careful if they feel more protected. Although usually small in comparison to the fundamental benefits of safety interventions, it may result in a lower net benefit than expected.

Selective Perception is the tendency not to notice and more quickly forget stimuli that cause emotional discomfort and contradict our prior beliefs. Selective perception is the process by which individuals perceive what they want to in media messages while ignoring opposing viewpoints. It is a broad term to identify the behavior all people exhibit to tend to "see things" based on their particular frame of reference. It also describes how we categorize and interpret sensory information in a way that favors one category or interpretation over another. In other words, selective perception is a form of bias because we interpret information in a way that is congruent with our existing values and beliefs. Psychologists believe this process occurs automatically.

The Semmelweis Reflex or "Semmelweis effect" is a metaphor for the reflex-like tendency to reject new evidence or new knowledge because it contradicts established norms, beliefs or paradigms.

Status Quo Bias is an emotional bias; a preference for the current state of affairs. The current baseline (or status quo) is taken as a reference point, and any change from that baseline is perceived as a loss. Status quo bias should be distinguished from a rational preference for the status quo ante, as when the current state of affairs is objectively superior to the available alternatives, or when imperfect information is a significant problem. A large body of evidence, however, shows that status quo bias frequently affects human decision-making.

A stereotype is an over-generalized belief about a particular category of people. Stereotypes are generalized because one assumes that the stereotype is true for each individual person in the category. While such generalizations may be useful when making quick decisions, they may be erroneous when applied to particular individuals.

Subjective Validation, sometimes called personal validation effect, is a cognitive bias by which a person will consider a statement or another piece of information to be correct if it has any personal meaning or significance to them. In other words, a person whose opinion is affected by subjective validation will perceive two unrelated events (i.e., a coincidence) to be related because their personal belief demands that they be related.

Surrogation is a psychological phenomenon in which the measure(s) of a construct of interest evolve to replace the construct itself. Research on performance measurement in management accounting has identified surrogation as "the tendency for managers to lose sight of the strategic construct(s) the performance measures are intended to represent, and subsequently act as though the measures are the constructs of interest" (emphasis in original).

The Time-Saving Bias describes people's tendency to misestimate the time that could be saved (or lost) when increasing (or decreasing) speed. In general, people underestimate the time that could be saved when increasing from a relatively low speed and overestimate the time that could be saved when increasing from a relatively high speed. People also underestimate the time that could be lost when decreasing from a low speed and overestimate the time that could be lost when decreasing from a high speed.

Zero-Sum Thinking, also known as zero-sum bias, is a cognitive bias that describes when an individual thinks that one situation is like a zero-sum game, where one person's gain would be another's loss. The term is derived from game theory. However, unlike the game theory concept, zero-sum thinking refers to a psychological construct—a person's subjective interpretation of a situation. Zero-sum thinking is captured by the saying "your gain is my loss" (or conversely, "your loss is my gain"). Rozycka-Tran et al. (2015) defined zero-sum thinking as: "A general belief system about the antagonistic nature of social relations, shared by people in a society or culture and based on the implicit assumption that a finite amount of goods exists in the world, in which one person’s winning makes others the losers, and vice versa...a relatively permanent and general conviction that social relations are like a zero-sum game. People who share this conviction believe that success, especially economic success, is possible only at the expense of other people’s failures."