Cognitive Bias

Shared information bias

Known as the tendency for group members to spend more time and energy discussing information that all members are already familiar with (i.e., shared information), and less time and energy discussing information that only some members are aware of (i.e., unshared information).

Group attribution error

The biased belief that the characteristics of an individual group member are reflective of the group as a whole or the tendency to assume that group decision outcomes reflect the preferences of group members, even when information is available that clearly suggests otherwise.

Observation selection bias

The effect of suddenly noticing things that were not noticed previously - and as a result wrongly assuming that the frequency has increased.

Contrast effect

The enhancement or reduction of a certain perception's stimuli when compared with a recently observed, contrasting object.

Endowment effect

The fact that people often demand much more to give up an object than they would be willing to pay to acquire it.

Testing effect

The fact that you more easily remember information you have read by rewriting it instead of rereading it.

Frequency illusion

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 (see also recency illusion). Colloquially, this illusion is known as the Baader-Meinhof Phenomenon.

Recency illusion

The illusion that a word or language usage is a recent innovation when it is in fact long established (see also frequency illusion).

Mood-congruent memory bias

The improved recall of information congruent with one's current mood.

Hindsight bias

The inclination to see past events as being more predictable than they actually were; also called the "I-knew-it-all-along" effect.

Suggestibility

Forms of misattribution where ideas suggested by a questioner are mistaken for memory.

Ostrich effect

Ignoring an obvious (negative) situation.

Choice-supportive bias

In a self-justifying manner retroactively ascribing one's choices to be more informed than they were when they were made.

Illusory correlation

Inaccurately perceiving a relationship between two unrelated events.

Illusory correlation

Inaccurately remembering a relationship between two events.

Consistency bias

Incorrectly remembering one's past attitudes and behavior as resembling present attitudes and behavior.

Out-group homogeneity bias

Individuals see members of their own group as being relatively more varied than members of other groups.

Zero-sum heuristic

Intuitively judging a situation to be zero-sum (i.e., that gains and losses are correlated). Derives from the zero-sum game in game theory, where wins and losses sum to zero. The frequency with which this bias occurs may be related to the social dominance orientation personality factor.

Negativity effect

The tendency of people, when evaluating the causes of the behaviors of a person they dislike, to attribute their positive behaviors to the environment and their negative behaviors to the person's inherent nature or of young people to be more negative information in the descriptions of others.

Conjunction fallacy

The tendency to assume that specific conditions are more probable than general ones.

Ambiguity effect

The tendency to avoid options for which missing information makes the probability seem "unknown.

Optimism bias

The tendency to be over-optimistic, overestimating favorable and pleasing outcomes (see also wishful thinking, valence effect, positive outcome bias).

Bias blind spot

The tendency to see oneself as less biased than other people, or to be able to identify more cognitive biases in others than in oneself.

Information bias

The tendency to seek information even when it cannot affect action.

Denomination effect

The tendency to spend more money when it is denominated in small amounts (e.g. coins) rather than large amounts (e.g. bills).

Risk compensation / Peltzman effect

The tendency to take greater risks when perceived safety increases.

Congruence bias

The tendency to test hypotheses exclusively through direct testing, instead of testing possible alternative hypotheses.

Duration neglect

The neglect of the duration of an episode in determining its value.

Picture superiority effect

The notions that concepts that are learned by viewing pictures are more easily and frequently recalled than are concepts that are learned by viewing their written word form counterparts.

Gambler's fallacy

The tendency to think that future probabilities are altered by past events, when in reality they are unchanged. Results from an erroneous conceptualization of the law of large numbers. For example, "I've flipped heads with this coin five times consecutively, so the chance of tails coming out on the sixth flip is much greater than heads."

Projection bias

The tendency to unconsciously assume that others (or one's future selves) share one's current emotional states, thoughts and values.

Insensitivity to sample size

The tendency to under-expect variation in small samples.

Planning fallacy

The tendency to underestimate task-completion times.

Empathy gap

The tendency to underestimate the influence or strength of feelings, in either oneself or others.

Distinction bias

The tendency to view two options as more dissimilar when evaluating them simultaneously than when evaluating them separately.

Unit bias

The tendency to want to finish a given unit of a task or an item. Strong effects on the consumption of food in particular.

Social comparison bias

The tendency, when making hiring decisions, to favor potential candidates who don't compete with one's own particular strengths.

Persistence

The unwanted recurrence of memories of a traumatic event.

Reactance

The urge to do the opposite of what someone wants you to do out of a need to resist a perceived attempt to constrain your freedom of choice (see also Reverse psychology).

Extrinsic incentives bias

An exception to the fundamental attribution error, when people view others as having (situational) extrinsic motivations and (dispositional) intrinsic motivations for oneself

Loss aversion

"The disutility of giving up an object is greater than the utility associated with acquiring it". (see also Sunk cost effects and endowment effect).

Hostile media effect

The tendency to see a media report as being biased, owing to one's own strong partisan views.

Dunning-Kruger effect

An effect in which incompetent people fail to realize they are incompetent because they lack the skill to distinguish between competence and incompetence. Actual competence may weaken self-confidence, as competent individuals may falsely assume that others have an equivalent understanding.

Belief bias

An effect where someone's evaluation of the logical strength of an argument is biased by the believability of the conclusion.

Fading affect bias

A bias in which the emotion associated with unpleasant memories fades more quickly than the emotion associated with positive events.

Conservatism or regressive bias

A certain state of mind wherein high values and high likelihoods are overestimated while low values and low likelihoods are underestimated.

Cryptomnesia

A form of misattribution where a memory is mistaken for imagination, because there is no subjective experience of it being a memory.

False memory

A form of misattribution where imagination is mistaken for a memory.

Availability cascade

A self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse (or "repeat something long enough and it will become true").

List-length effect

A smaller percentage of items are remembered in a longer list, but as the length of the list increases, the absolute number of items remembered increases as well.

Worse-than-average effect

A tendency to believe ourselves to be worse than others at tasks, which are difficult.

Pareidolia

A vague and random stimulus (often an image or sound) is perceived as significant, e.g., seeing images of animals or faces in clouds, the man in the moon, and hearing non-existent hidden messages on records played in reverse.

Change bias

After an investment of effort in producing change, remembering one's past performance as more difficult than it actually was.

Defensive attribution hypothesis

Attributing more blame to a harm-doer as the outcome becomes more severe or as personal or situational similarity to the victim increases.

Hard-easy effect

Based on a specific level of task difficulty, the confidence in judgments is too conservative and not extreme enough.

Exaggerated expectation

Based on the estimates, real-world evidence turns out to be less extreme than our expectations (conditionally inverse of the conservatism bias).

Illusion of validity

Belief that furtherly acquired information generates additional relevant data for predictions, even when it evidently does not.

Bizarreness effect

Bizarre material is better remembered than common material.

Essentialism

Categorizing people and things according to their essential nature, in spite of variations.

Survivorship bias

Concentrating on the people or things that "survived" some process and inadvertently overlooking those that didn't because of their lack of visibility.

Source confusion

Confusing episodic memories with other information, creating distorted memories.

Reactive devaluation

Devaluing proposals only because they are purportedly originated with an adversary.

Suffix effect

Diminishment of the recency effect because a sound item is appended to the list that the subject is not required to recall.

Framing effect

Drawing different conclusions from the same information, depending on how or by whom that information is presented.

Overconfidence effect

Excessive confidence in one's own answers to questions. For example, for certain types of questions, answers that people rate as "99% certain" turn out to be wrong 40% of the time.

Stereotyping

Expecting a member of a group to have certain characteristics without having actual information about that individual.

Naive cynicism

Expecting more egocentric bias in others than in oneself.

Functional fixedness

Limits a person to using an object only in the way it is traditionally used.

Misinformation effect

Memory becoming less accurate because of interference from post-event information.

Stereotypical bias

Memory distorted towards stereotypes (e.g., racial or gender), e.g., "black-sounding" names being misremembered as names of criminals.

Leveling and Sharpening

Memory distortions introduced by the loss of details in a recollection over time, often concurrent with sharpening or selective recollection of certain details that take on exaggerated significance in relation to the details or aspects of the experience lost through leveling. Both biases may be reinforced over time, and by repeated recollection or re-telling of a memory.

Egocentric bias

Occurs when people claim more responsibility for themselves for the results of a joint action than an outside observer would credit them.

Illusory superiority

Overestimating one's desirable qualities, and underestimating undesirable qualities, relative to other people. (Also known as "Lake Wobegon effect," "better-than-average effect," or "superiority bias").

Illusion of transparency

People overestimate others' ability to know them, and they also overestimate their ability to know others.

Illusion of asymmetric insight

People perceive their knowledge of their peers to surpass their peers' knowledge of them.

Subjective validation

Perception that something is true if a subject's belief demands it to be true. Also assigns perceived connections between coincidences.

Zero-risk bias

Preference for reducing a small risk to zero over a greater reduction in a larger risk.

Decoy effect

Preferences for either option A or B changes in favor of option B when option C is presented, which is similar to option B but in no way better.

Negativity bias

Psychological phenomenon by which humans have a greater recall of unpleasant memories compared with positive memories.

Egocentric bias

Recalling the past in a self-serving manner, e.g., remembering one's exam grades as being better than they were, or remembering a caught fish as bigger than it really was.

Primacy effect

Recency effect & Serial position effect, That items near the end of a sequence are the easiest to recall, followed by the items at the beginning of a sequence; items in the middle are the least likely to be remembered.

Rhyme as reason effect

Rhyming statements are perceived as more truthful. A famous example being used in the O.J Simpson trial with the defense's use of the phrase "If the gloves don't fit, then you must acquit."

Lag effect

See spacing effect.

Ultimate attribution error

Similar to the fundamental attribution error, in this error a person is likely to make an internal attribution to an entire group instead of the individuals within the group.

Hindsight bias

Sometimes called the "I-knew-it-all-along" effect, the tendency to see past events as being predictable at the time those events happened.

Naïve realism

The belief that we see reality as it really is - objectively and without bias; that the facts are plain for all to see; that rational people will agree with us; and that those who don't are uninformed, lazy, irrational, or biased.

Conservatism or Regressive Bias

Tendency to remember high values and high likelihoods/probabilities/frequencies lower than they actually were and low ones higher than they actually were. Based on the evidence, memories are not extreme enough.

Next-in-line effect

That a person in a group has diminished recall for the words of others who spoke immediately before him, if they take turns speaking.

Von Restorff effect

That an item that sticks out is more likely to be remembered than other items.

Part-list cueing effect

That being shown some items from a list and later retrieving one item causes it to become harder to retrieve the other items.

Context effect

That cognition and memory are dependent on context, such that out-of-context memories are more difficult to retrieve than in-context memories (e.g., recall time and accuracy for a work-related memory will be lower at home, and vice versa).

Levels-of-processing effect

That different methods of encoding information into memory have different levels of effectiveness.

Humor effect

That humorous items are more easily remembered than non-humorous ones, which might be explained by the distinctiveness of humor, the increased cognitive processing time to understand the humor, or the emotional arousal caused by the humor.

Spacing effect

That information is better recalled if exposure to it is repeated over a long span of time rather than a short one.

Processing difficulty effect

That information that takes longer to read and is thought about more (processed with more difficulty) is more easily remembered.

Self-relevance effect

That memories relating to the self are better recalled than similar information relating to others.

Modality effect

That memory recall is higher for the last items of a list when the list items were received via speech than when they were received through writing.

Positivity effect

That older adults favor positive over negative information in their memories.

Illusion of truth effect

That people are more likely to identify as true statements those they have previously heard (even if they cannot consciously remember having heard them), regardless of the actual validity of the statement. In other words, a person is more likely to believe a familiar statement than an unfamiliar one.

Peak-end rule

That people seem to perceive not the sum of an experience but the average of how it was at its peak (e.g. pleasant or unpleasant) and how it ended.

Generation effect (Self-generation effect)

That self-generated information is remembered best. For instance, people are better able to recall memories of statements that they have generated than similar statements generated by others.

Verbatim effect

That the "gist" of what someone has said is better remembered than the verbatim wording. This is because memories are representations, not exact copies.

Zeigarnik effect

That uncompleted or interrupted tasks are remembered better than completed ones.

Hot-hand fallacy

The "hot-hand fallacy" (also known as the "hot hand phenomenon" or "hot hand") is the fallacious belief that a person who has experienced success has a greater chance of further success in additional attempts.

Forer effect or Barnum effect

The observation that individuals will give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them, but are in fact vague and general enough to apply to a wide range of people. This effect can provide a partial explanation for the widespread acceptance of some beliefs and practices, such as astrology, fortune telling, graphology, and some types of personality tests.

Irrational escalation

The phenomenon where people justify increased investment in a decision, based on the cumulative prior investment, despite new evidence suggesting that the decision was probably wrong. Also known as the sunk cost fallacy.

Reminiscence bump

The recalling of more personal events from adolescence and early adulthood than personal events from other lifetime periods.

Normalcy bias

The refusal to plan for, or react to, a disaster that has never happened before.

Rosy retrospection

The remembering of the past as having been better than it really was.

Childhood amnesia

The retention of few memories from before the age of four.

Halo effect

The tendency for a person's positive or negative traits to "spill over" from one personality area to another in others' perceptions of them (see also physical attractiveness stereotype).

Selective perception

The tendency for expectations to affect perception.

Experimenter's or expectation bias

The tendency for experimenters to believe, certify, and publish data that agree with their expectations for the outcome of an experiment, and to disbelieve, discard, or downgrade the corresponding weightings for data that appear to conflict with those expectations.

Actor-observer bias

The tendency for explanations of other individuals' behaviors to overemphasize the influence of their personality and underemphasize the influence of their situation (see also Fundamental attribution error), and for explanations of one's own behaviors to do the opposite (that is, to overemphasize the influence of our situation and underemphasize the influence of our own personality).

Cross-race effect

The tendency for people of one race to have difficulty identifying members of a race other than their own.

Cheerleader effect

The tendency for people to appear more attractive in a group than in isolation.

Moral luck

The tendency for people to ascribe greater or lesser moral standing based on the outcome of an event.

Just-world phenomenon

The tendency for people to believe that the world is just and therefore people "get what they deserve."

In-group bias

The tendency for people to give preferential treatment to others they perceive to be members of their own groups.

Hyperbolic discounting

The tendency for people to have a stronger preference for more immediate payoffs relative to later payoffs, where the tendency increases the closer to the present both payoffs are. Also known as current moment bias, present-bias, and related to Dynamic inconsistency.

Fundamental attribution error

The tendency for people to over-emphasize personality-based explanations for behaviors observed in others while under-emphasizing the role and power of situational influences on the same behavior (see also actor-observer bias, group attribution error, positivity effect, and negativity effect).

False consensus effect

The tendency for people to overestimate the degree to which others agree with them.

IKEA effect

The tendency for people to place a disproportionately high value on objects that they partially assembled themselves, such as furniture from IKEA, regardless of the quality of the end result.

Trait ascription bias

The tendency for people to view themselves as relatively variable in terms of personality, behavior, and mood while viewing others as much more predictable.

Just-world hypothesis

The tendency for people to want to believe that the world is fundamentally just, causing them to rationalize an otherwise inexplicable injustice as deserved by the victim(s).

Pessimism bias

The tendency for some people, especially those suffering from depression, to overestimate the likelihood of negative things happening to them.

Moral credential effect

The tendency of a track record of non-prejudice to increase subsequent prejudice.

Attentional bias

The tendency of our perception to be affected by our recurring thoughts.

Confirmation bias

The tendency to search for, interpret, focus on and remember information in a way that confirms one's preconceptions.

Self-serving bias

The tendency to claim more responsibility for successes than failures. It may also manifest itself as a tendency for people to evaluate ambiguous information in a way beneficial to their interests (see also group-serving bias).

Neglect of probability

The tendency to completely disregard probability when making a decision under uncertainty.

Money illusion

The tendency to concentrate on the nominal (face value) of money rather than its value in terms of purchasing power.

System justification

The tendency to defend and bolster the status quo. Existing social, economic, and political arrangements tend to be preferred, and alternatives disparaged sometimes even at the expense of individual and collective self-interest. (See also status quo bias.)

Telescoping effect

The tendency to displace recent events backward in time and remote events forward in time, so that recent events appear more remote, and remote events, more recent.

Bandwagon effect

The tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink and herd behavior.

Mere exposure effect

The tendency to express undue liking for things merely because of familiarity with them.

Google effect

The tendency to forget information that can be found readily online by using Internet search engines.

Forer effect (aka Barnum effect)

The tendency to give high accuracy ratings to descriptions of their personality that supposedly are tailored specifically for them, but are in fact vague and general enough to apply to a wide range of people. For example, horoscopes.

Pro-innovation bias

The tendency to have an excessive optimism towards an invention or innovation's usefulness throughout society, while often failing to identify its limitations and weaknesses.

Base rate fallacy or base rate neglect

The tendency to ignore base rate information (generic, general information) and focus on specific information (information only pertaining to a certain case).

Outcome bias

The tendency to judge a decision by its eventual outcome instead of based on the quality of the decision at the time it was made.

Omission bias

The tendency to judge harmful actions as worse, or less moral, than equally harmful omissions (inactions).

Subadditivity effect

The tendency to judge probability of the whole to be less than the probabilities of the parts.

Status quo bias

The tendency to like things to stay relatively the same (see also loss aversion, endowment effect, and system justification).

Pseudocertainty effect

The tendency to make risk-averse choices if the expected outcome is positive, but make risk-seeking choices to avoid negative outcomes.

Clustering illusion

The tendency to over-expect small runs, streaks, or clusters in large samples of random data (that is, seeing phantom patterns).

Social desirability bias

The tendency to over-report socially desirable characteristics or behaviors in one self and under-report socially undesirable characteristics or behaviors.

Restraint bias

The tendency to overestimate one's ability to show restraint in the face of temptation.

Illusion of control

The tendency to overestimate one's degree of influence over other external events.

Spotlight effect

The tendency to overestimate the amount that other people notice your appearance or behavior.

Impact bias

The tendency to overestimate the length or the intensity of the impact of future feeling states.

Availability heuristic

The tendency to overestimate the likelihood of events with greater "availability" in memory, which can be influenced by how recent the memories are or how unusual or emotionally charged they may be.

Post-purchase rationalization

The tendency to persuade oneself through rational argument that a purchase was a good value.

Focusing effect

The tendency to place too much importance on one aspect of an event.

Less-is-better effect

The tendency to prefer a smaller set to a larger set judged separately, but not jointly

Semmelweis reflex

The tendency to reject new evidence that contradicts a paradigm.

Anchoring or focalism

The tendency to rely too heavily, or "anchor," on one trait or piece of information when making decisions (usually the first piece of information that we acquire on that subject)

Choice-supportive bias

The tendency to remember one's choices as better than they actually were.

Identifiable victim effect

The tendency to respond more strongly to a single identified person at risk than to a large group of people at risk.

Conservatism (Bayesian)

The tendency to revise one's belief insufficiently when presented with new evidence.

Well travelled road effect

Underestimation of the duration taken to traverse oft-traveled routes and overestimation of the duration taken to traverse less familiar routes.

Time-saving bias

Underestimations of the time that could be saved (or lost) when increasing (or decreasing) from a relatively low speed and overestimations of the time that could be saved (or lost) when increasing (or decreasing) from a relatively high speed.

Observer-expectancy effect

When a researcher expects a given result and therefore unconsciously manipulates an experiment or misinterprets data in order to find it (see also subject-expectancy effect).

Tip of the tongue phenomenon

When a subject is able to recall parts of an item, or related information, but is frustratingly unable to recall the whole item. This is thought an instance of "blocking" where multiple similar memories are being recalled and interfere with each other.

Curse of knowledge

When better-informed people find it extremely difficult to think about problems from the perspective of lesser-informed people.

Backfire effect

When people react to disconfirming evidence by strengthening their beliefs.

Illusion of external agency

When people view self-generated preferences as instead being caused by insightful, effective and benevolent agents.