List of cognitive biases

Every now and then a man's mind is stretched by a new idea or sensation, and never shrinks back to its former dimensions. Cognitive bias describes the inherent thinking errors that humans make in processing information. Some of these have been verified empirically in the field of psychology, while others are considered general categories of bias. These thinking errors prevent one from accurately understanding reality, even when confronted with all the needed data and evidence to form an accurate view. Many conflicts between science and religion are due to cognitive biases preventing people from coming to the same conclusions with the same evidence. Cognitive bias is intrinsic to human thought, and therefore any system of acquiring knowledge that attempts to describe reality must include mechanisms to control for bias or it is inherently invalid.

The best known system for vetting and limiting the consequences of cognitive bias is the scientific method, as it places evidence and methodology behind the idea that is under open scrutiny. By this, many opinions and separate analyses can be used to compensate for the bias of any one individual. It is important to remember, however, that in everyday life, just knowing about these biases doesn't necessarily free one from them.

Decision making and behavioral biases
Many of these biases are studied for how they affect belief formation and business decisions and scientific research.
 *  — the tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink, crowd psychology, herd behaviour, and manias.
 * Bias blind spot — the tendency not to compensate for one's own cognitive biases, or the tendency to believe that one is less affected by cognitive biases than other people.
 * Choice-supportive bias — the tendency to remember one's choices as better than they actually were.
 * Confirmation bias — the tendency to search for or interpret information in a way that confirms one's preconceptions.
 * Congruence bias — the tendency to test hypotheses exclusively through direct testing, in contrast to tests of possible alternative hypotheses.
 * Contrast effect — the enhancement or diminishment of a weight or other measurement when compared with a recently observed contrasting object.
 * Déformation professionnelle — the tendency to look at things according to the conventions of one's own profession, forgetting any broader point of view.
 *  — "the fact that people often demand much more to give up an object than they would be willing to pay to acquire it".
 * Exposure-suspicion bias — a knowledge of a subject's disease in a medical study may influence the search for causes.
 * Extreme aversion — most people will go to great lengths to avoid extremes. People are more likely to choose an option if it is the intermediate choice.
 *  — prediction bias occurring when people place too much importance on one aspect of an event; causes error in accurately predicting the utility of a future outcome.
 * Framing — drawing different conclusions from the same information, depending on how that information is presented.
 * Hyperbolic discounting — the tendency for people to have a stronger preference for more immediate payoffs relative to later payoffs, the closer to the present both payoffs are.
 * Illusion of control — the tendency for human beings to believe they can control or at least influence outcomes that they clearly cannot.
 * Impact bias — the tendency for people to overestimate the length or the intensity of the impact of future feeling states.
 * Information bias — the tendency to seek information even when it cannot affect action.
 *  — the tendency to make irrational decisions based upon rational decisions in the past or to justify actions already taken.
 *  — "the disutility of giving up an object is greater than the utility associated with acquiring it". (see also sunk cost effects and Endowment effect).
 *  — the tendency to completely disregard probability when making a decision under uncertainty.
 *  — the tendency for people to express undue liking for things merely because they are familiar with them.
 * Obsequiousness bias — the tendency to systematically alter responses in the direction they perceive desired by the investigator.
 *  — the tendency to judge harmful actions as worse, or less moral, than equally harmful omissions (inactions).
 * 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.
 * Planning fallacy — the tendency to underestimate task-completion times. Also formulated as Hofstadter's Law: "It always takes longer than you expect, even when you take into account Hofstadter's Law."
 *  — the tendency to persuade oneself through rational argument that a purchase was a good value.
 *  — 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.
 *  — the tendency for expectations to affect perception.
 * Status quo bias — the tendency for people to like things to stay relatively the same (see also Endowment effect and Loss aversion).
 * Survivorship bias — a form of selection bias focusing on what has survived to the present and ignoring what must have been lost.
 * Unacceptability bias — questions that may embarrass or invade privacy are refused or evaded.
 * Unit bias — the tendency to want to finish a given unit of a task or an item with strong effects on the consumption of food in particular
 * Von Restorff effect — the tendency for an item that "stands out like a sore thumb" to be more likely to be remembered than other items.
 * Zero-risk bias — the preference for reducing a small risk to zero over a greater reduction in a larger risk. It is relevant, for example, to the allocation of public health resources and the debate about nuclear power.

Biases in probability and belief
Many of these biases are often studied for how they affect business and economic decisions and how they affect experimental research.
 * Ambiguity effect — the avoidance of options for which missing information makes the probability seem "unknown".
 * Anchoring — the tendency to rely too heavily, or "anchor," on a past reference or on one trait or piece of information when making decisions.
 * Anthropic bias — the tendency for one's evidence to be biased by observation selection effects.
 * Attentional bias — neglect of relevant data when making judgments of a correlation or association.
 *  — a biased prediction, due to the tendency to focus on the most salient and emotionally-charged outcome.
 * Clustering illusion — the tendency to see patterns where actually none exist, including apophenia and pareidolia
 * Conjunction fallacy — the tendency to assume that specific conditions are more probable than general ones.
 * Frequency illusion — the phenomenon in which people who just learn or notice something start seeing it everywhere. Also known as the Baader-Meinhof Phenomenon (from the Baader-Meinhof Gang).
 * Gambler's fallacy — the tendency to assume that independent random events are influenced by previous random events. 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."
 * Hindsight bias — sometimes called the "I-knew-it-all-along" effect: the inclination to see past events as being predictable, based on knowledge of later events.
 * Hostile media effect — the tendency to perceive news coverage as biased against your position on an issue.
 * Illusory correlation — beliefs that inaccurately suppose a relationship between a certain type of action and an effect.
 * Ludic fallacy — the analysis of chance-related problems with the narrow frame of games, ignoring the complexity of reality and the non-Gaussian distribution of many things.
 * Neglect of prior base rates effect — the tendency to fail to incorporate prior known probabilities which are pertinent to the decision at hand.
 *  — 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).
 * Optimism bias — the systematic tendency to be over-optimistic about the outcome of planned actions. Found to be linked to the "left inferior frontal gyrus" section of the brain, and disrupting this section of the brain removes the bias. Article summarising this finding
 * Overconfidence effect — the tendency to overestimate one's own abilities.
 * Positive outcome bias — a tendency in prediction to overestimate the probability of good things happening to them (see also wishful thinking, optimism bias, and valence effect).
 *  — the tendency to weigh initial events more than subsequent events.
 *  — the tendency to weigh recent events more than earlier events (see also 'peak-end rule').
 * Reminiscence bump — the effect that people tend to recall more personal events from adolescence and early adulthood than from other lifetime periods.
 * Rosy retrospection — the tendency to rate past events more positively than they had actually rated them when the event occurred.
 * Subadditivity effect — the tendency to judge probability of the whole to be less than the probabilities of the parts.
 * Telescoping effect — the effect that recent events appear to have occurred more remotely and remote events appear to have occurred more recently.
 * Texas sharpshooter fallacy — the fallacy of selecting or adjusting a hypothesis after the data is collected, making it impossible to test the hypothesis fairly.

Social biases
Most of these biases are labeled as attributional biases.
 * Actor-observer bias — the tendency for explanations for other individual's behaviors to overemphasize the influence of their personality and underemphasize the influence of their situation. This is coupled with the opposite tendency for the self in that one's explanations for their own behaviors overemphasize their situation and underemphasize the influence of their personality. (See also fundamental attribution error.)
 * Dunning-Kruger effect — "…when people are incompetent in the strategies they adopt to achieve success and satisfaction, they suffer a dual burden: Not only do they reach erroneous conclusions and make unfortunate choices, but their incompetence robs them of the ability to realize it. Instead, …they are left with the mistaken impression that they are doing just fine." (See also the Lake Wobegon effect and overconfidence effect.)
 * Egocentric bias — occurs when people claim more responsibility for themselves for the results of a joint action than an outside observer would.
 * Forer effect (a.k.a. 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.
 *  — the tendency for people to overestimate the degree to which others agree with them.
 *  — 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).
 * Halo effect — the tendency for a person's positive or negative traits to "spill over" from one area of their personality to another in others' perceptions of them (see also physical attractiveness stereotype).
 * Herd instinct (or herd mentality) — a common tendency to adopt the opinions and follow the behaviors of the majority to feel safer and to avoid conflict.
 * Illusion of asymmetric insight — people perceive their knowledge of their peers to surpass their peers' knowledge of them.
 * Illusion of transparency — people overestimate others' ability to know them, and they also overestimate their ability to know others.
 * Ingroup bias — the tendency for people to give preferential treatment to others they perceive to be members of their own groups.
 * Just-world phenomenon — the tendency for people to believe that the world is "just" and therefore people "get what they deserve".
 *  — the human tendency to report flattering beliefs about oneself and believe that one is above average (see also worse-than-average effect, overconfidence effect, and illusory superiority).
 * Notational bias — a form of cultural bias in which a notation induces the appearance of a nonexistent natural law.
 * Outgroup homogeneity bias — individuals see members of their own group as being relatively more varied than members of other groups.
 * Projection bias — the tendency to unconsciously assume that others share the same or similar thoughts, beliefs, values, or positions.
 * Self-serving bias — the tendency to attribute successes to internal characteristics while blaming failures on outside forces. 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).
 * Modesty bias — The tendency to blame failures on oneself while attributing successes to situational factors. Opposite of self-serving bias.
 * Self-fulfilling prophecy — the tendency to engage in behaviors that elicit results which will (consciously or subconsciously) confirm our beliefs.
 * System justification — the tendency to defend and bolster the status quo, i.e. existing social, economic, and political arrangements tend to be preferred, and alternatives disparaged sometimes even at the expense of individual and collective self-interest.
 * 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.
 * Ultimate attribution error — A sub-type of the fundamental attribution error above, the ultimate attribution error occurs when negative behavior in one's own group is explained away as circumstantial, but negative behavior among outsiders is believed to be evidence of flaws in character.

Memory errors

 * Beneffectance — perceiving oneself as responsible for desirable outcomes but not responsible for undesirable ones. (Term coined by Greenwald (1980))
 * Consistency bias — incorrectly remembering one's past attitudes and behaviour as resembling present attitudes and behaviour.
 * Cryptomnesia — a form of misattribution where a memory is mistaken for imagination.
 * 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 being bigger than it was
 * Confabulation or false memory — Remembering something that never actually happened.
 * Hindsight bias — filtering memory of past events through present knowledge, so that those events look more predictable than they actually were; also known as the 'I-knew-it-all-along effect'.
 * Selective Memory and selective reporting
 * Suggestibility — a form of misattribution where ideas suggested by a questioner are mistaken for memory. Often a key aspect of hypnotherapy.
 * Serial position effect — Serial position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst.

Common theoretical causes of some cognitive biases

 * Attribution theory, especially:
 * Salience
 * Cognitive dissonance, and related:
 * Impression management
 * Self-perception theory
 * Heuristics, including:
 * Availability heuristic
 * Representativeness heuristic
 * Adaptive bias