Behavioral Biases

*Courtesy of Wikipedia.

Ambiguity effect
The tendency to avoid options for which the probability of a favorable outcome is unknown.

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 acquired on that subject).

Anthropocentric thinking
The tendency to use human analogies as a basis for reasoning about other, less familiar, biological phenomena.

Anthropomorphism or personification
The tendency to characterize animals, objects, and abstract concepts as possessing human-like traits, emotions, and intentions.

Attentional bias
The tendency of perception to be affected by recurring thoughts.

Automation bias
The tendency to depend excessively on automated systems which can lead to erroneous automated information overriding correct decisions.

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.

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”).

Backfire effect
The reaction to disconfirming evidence by strengthening one’s previous beliefs.

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

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).

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

Ben Franklin effect
A person who has performed a favor for someone is more likely to do another favor for that person than they would be if they had received a favor from that person.

Berkson’s paradox
The tendency to misinterpret statistical experiments involving conditional probabilities.

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.

Choice-supportive bias
The tendency to remember one’s choices as better than they actually were.

Clustering illusion
The tendency to overestimate the importance of small runs, streaks, or clusters in large samples of random data (that is, seeing phantom patterns).

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

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

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

Conservatism (belief revision)
The tendency to revise one’s belief insufficiently when presented with new evidence.

Continued influence effect
The tendency to believe previously learned misinformation even after it has been corrected. Misinformation can still influence inferences one generates after a correction has occurred.

Contrast effect
The enhancement or reduction of a certain stimulus’ perception when compared with a recently observed, contrasting object.

Courtesy bias
The tendency to give an opinion that is more socially correct than one’s true opinion, so as to avoid offending anyone.

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

Declinism
The predisposition to view the past favorably (rosy retrospection) and future negatively.

Decoy effect
Preferences for either option A or B change in favor of option B when option C is presented, which is completely dominated by option B (inferior in all respects) and partially dominated by option A.

Default effect
When given a choice between several options, the tendency to favor the default one.

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).

Disposition effect
The tendency to sell an asset that has accumulated in value and resist selling an asset that has declined in value.

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

Dread aversion
Just as losses yield double the emotional impact of gains, dread yields double the emotional impact of savouring.

Dunning–Kruger effect
The tendency for unskilled individuals to overestimate their own ability and the tendency for experts to underestimate their own ability.

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

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

Endowment effect
The tendency for people to demand much more to give up an object than they would be willing to pay to acquire it.

Exaggerated expectation
The tendency to expect or predict more extreme outcomes than those outcomes that actually happen.

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.

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

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.

Form function attribution bias
In human–robot interaction, the tendency of people to make systematic errors when interacting with a robot. People may base their expectations and perceptions of a robot on its appearance (form) and attribute functions which do not necessarily mirror the true functions of the robot.

Framing effect          
Drawing different conclusions from the same information, depending on how that information is presented.

Frequency illusion or Baader–Meinhof effect
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).[49] This illusion is sometimes referred to as the Baader–Meinhof phenomenon.

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

Gambler’s fallacy
The tendency to think that future probabilities are altered by past events, when in reality they are unchanged. The fallacy arises 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.”

Groupthink
The 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.

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

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.

Hostile attribution bias
The “hostile attribution bias” is the tendency to interpret others’ behaviors as having hostile intent, even when the behavior is ambiguous or benign.

Hot-hand fallacy
The “hot-hand fallacy” (also known as the “hot hand phenomenon” or “hot hand”) is the belief that a person who has experienced success with a random event has a greater chance of further success in additional attempts.

Hyperbolic discounting
Discounting is the tendency for people to have a stronger preference for more immediate payoffs relative to later payoffs. Hyperbolic discounting leads to choices that are inconsistent over time – people make choices today that their future selves would prefer not to have made, despite using the same reasoning.[58] Also known as current moment bias, present-bias, and related to Dynamic inconsistency. A good example of this: a study showed that when making food choices for the coming week, 74% of participants chose fruit, whereas when the food choice was for the current day, 70% chose chocolate.

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.

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.

Illicit transference
Occurs when a term in the distributive (referring to every member of a class) and collective (referring to the class itself as a whole) sense are treated as equivalent. The two variants of this fallacy are the fallacy of composition and the fallacy of division.

Illusion of control
The tendency to overestimate one’s degree of influence over other external events.

Illusion of validity
Belief that our judgments are accurate, especially when available information is consistent or inter-correlated.

Illusory correlation
Inaccurately perceiving a relationship between two unrelated events.

Illusory truth effect
A tendency to believe that a statement is true if it is easier to process, or if it has been stated multiple times, regardless of its actual veracity. These are specific cases of truthiness.

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

Implicit association
The speed with which people can match words depends on how closely they are associated. This has generated some controversy when some people are able to match pairings like “White” and “pleasant” faster than “Black” and “pleasant”, with debate over whether this indicates a form of unconscious prejudice that could result in discrimination.

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

Insensitivity to sample size
The tendency to under-expect variation in small samples.

Interoceptive bias
The tendency for sensory input from the body to be taken as evidence of external reality. (As for example, in parole judges who are more lenient when fed and rested.)

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.

Law of the instrument
An over-reliance on a familiar tool or methods, ignoring or under-valuing alternative approaches. “If all you have is a hammer, everything looks like a nail.”

Less-is-better effect
The tendency to prefer a smaller set to a larger set judged separately, but not jointly.

Look-elsewhere effect          
An apparently statistically significant observation may have actually arisen by chance because of the size of the parameter space to be searched.

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).

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

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

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

Negativity bias or Negativity effect
Psychological phenomenon by which humans have a greater recall of unpleasant memories compared with positive memories. (see also actor-observer bias, group attribution error, positivity effect, and negativity effect).

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

Normalcy bias
The refusal to plan for, or react to, a disaster which has never happened before.

Not invented here
Aversion to contact with or use of products, research, standards, or knowledge developed outside a group. Related to IKEA effect.

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).

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

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

Ostrich effect
Ignoring an obvious (negative) situation.

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.

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.

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.

Pygmalion effect
The phenomenon whereby others’ expectations of a target person affect the target person’s performance.

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

Planning fallacy
The tendency to underestimate task-completion times.

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

Present bias
The tendency of people to give stronger weight to payoffs that are closer to the present time when considering trade-offs between two future moments.

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.

Projection bias          
The tendency to overestimate how much our future selves share one’s current preferences, thoughts and values, thus leading to sub-optimal choices.

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

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).

Reactive devaluation
Devaluing proposals only because they purportedly originated with an adversary.

Recency illusion
The illusion that a phenomenon one has noticed only recently is itself recent. Often used to refer to linguistic phenomena; the illusion that a word or language usage that one has noticed only recently is an innovation when it is in fact long-established (see also frequency illusion).

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

Restraint bias
The tendency to overestimate one’s ability to show restraint in the face of temptation.

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.”

Risk compensation / Peltzman effect
The tendency to take greater risks when perceived safety increases.

Salience bias
The tendency to focus on items that are more prominent or emotionally striking and ignore those that are unremarkable, even though this difference is often irrelevant by objective standards.

Selection bias
The tendency to notice something more when something causes us to be more aware of it, such as when we buy a car, we tend to notice similar cars more often than we did before. They are not suddenly more common – we just are noticing them more. Also called the Observational Selection Bias.

Selective perception
The tendency for expectations to affect perception.

Semmelweis reflex
The tendency to reject new evidence that contradicts a paradigm.

Sexual overperception bias / sexual underperception bias
The tendency to over-/underestimate sexual interest of another person in oneself.

Simple metric bias
Tendency to reduce a complex problem to a single variable, that is relatively easy to influence. (eg. attractiveness to body weight)

Social comparison bias
The tendency, when making decisions, to favour potential candidates who don’t compete with one’s own particular strengths.

Social desirability bias
The tendency to over-report socially desirable characteristics or behaviours in oneself and under-report socially undesirable characteristics or behaviours.

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

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

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

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

Surrogation
Losing sight of the strategic construct that a measure is intended to represent, and subsequently acting as though the measure is the construct of interest.

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.

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.

Third-person effect
Belief that mass communicated media messages have a greater effect on others than on themselves.

Parkinson’s law of triviality
The tendency to give disproportionate weight to trivial issues. Also known as bikeshedding, this bias explains why an organization may avoid specialized or complex subjects, such as the design of a nuclear reactor, and instead focus on something easy to grasp or rewarding to the average participant, such as the design of an adjacent bike shed.

Unit bias
The standard suggested amount of consumption (e.g., food serving size) is perceived to be appropriate, and a person would consume it all even if it is too much for this particular person.

Weber–Fechner law
Difficulty in comparing small differences in large quantities.

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.

Women are wonderful effect
A tendency to associate more positive attributes with women than with men.

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

Zero-sum bias
A bias whereby a situation is incorrectly perceived to be like a zero-sum game (i.e., one person gains at the expense of another).

The art of living a virtuous life.

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