Mirrors : BiasesActor–observer biasAttentional biasChoice-supportive biasConfirmation biasCongruence biasRegressive biasEgocentric biasImpact biasInformation biasModesty biasMood-congruent biasOmission biasSelf-serving biasStatus quo biasSuperiority biasSurvivorship biasTrait ascription biasUnit biasExposure-suspicion biasStereotypical biasZero-risk biasAuthority biasCorrespondence biasObsequiousness biasUnacceptability biasProjection biasConsistency biasHindsight biasOptimism biasOutcome biasPositive biasPositive outcome biasGroupthink biasGroupthinkConformity biasIngroup biasHomogeneity biasShared information biasBandwagon fallacyEffectsAmbiguity effectBizarreness effectBystander effectContext effectContrast effectCross-race effectDunning-kruger effectFalse consensus effectForer effectMotivated cognitionGeneration effectGoogle effectHalo effectHostile media effectHumor effectLake wobegon effectList-length effectMere exposure effectMisinformation effectModality effectOverconfidence effectPart-list cueing effectPicture superiority effectPositivity effectPrimacy effectProcessing effectPseudocertainty effectRecency effectSelf-relevance effectSpacing effectSpotlight effectSubadditivity effectSuffix effectTelescoping effectTesting effectUnderconfidence effectVerbatim effectVon restorff effectZeigarnik effectFocusing effectEndowment effectNext-in-line effectFallaciesConjunction fallacyDetached lever fallacyGambler's fallacyMind projection fallacyTypical mind fallacyFallacy of grayPlanning fallacySunk cost fallacyGiant cheesecake fallacyNarrative fallacyScales of justice fallacyTop 1% fallacyFallacy of relative privationIllusionsAsymmetric insightControlExternal agencyTruth effectClusteringFrequencyTransparencyHeuristicsAbsurdityAffectAvailabilityRepresentativeness

The list was compiled from LessWrong as well as personal notes, collected from the Philosopher's Toolkit and other sources. Rationality is characteristic of thinking and acting optimally.


Actor–observer bias

Tendency to overemphasize the influence of their personality and underemphasize the influence of their situation.

Attentional bias

Tendency to neglect relevant data when making judgments of a correlation or association.

Choice-supportive bias

Tendency to retroactively ascribing to one's choices to be more informed than they were when they were made.

Confirmation bias

Tendency to interpret information in a way that confirms one's preconceptions.

Congruence bias

Tendency to test hypotheses exclusively through direct testing, in contrast to tests of possible alternative hypotheses.

Regressive bias

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

Egocentric bias

Tendency to claim more responsibility for themselves for the results of a joint action than an outside observer would. Recalling the past in a self-serving manner. Like remembering one's exam grades as being better than they were.

Impact bias

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

Information bias

Tendency to seek information even when it cannot affect action.

Modesty bias

Tendency to blame failures on oneself while attributing successes to situational factors; opposite of self-serving bias.

Mood-congruent bias

Tendency to recall information congruent with one's current mood.

Omission bias

Tendency to judge harmful actions as worse, or less moral, than equally harmful omissions.

Self-serving bias

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.

Status quo bias

Tendency to like things to stay relatively the same.

Superiority bias

Tendency to overestimating one's desirable qualities, and underestimating undesirable qualities, relative to other people. Also known as the Lake Wobegon effect.

Survivorship bias

Tendency of focusing on what has survived to the present and ignoring what must have been lost.

Trait ascription bias

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

Unit bias

Tendency to want to finish a given unit of a task or an item with strong effects on the consumption of food in particular.

Exposure-suspicion bias

Tendency to steer the search for causes based on the knowledge of a subject's disease in a medical study.

Stereotypical bias

Tendency to distort memories towards stereotypes. "Black-sounding" names being misremembered as names of criminals.

Zero-risk bias

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

Authority bias

Tendency to attribute greater accuracy to the opinion of an authority figure and be more influenced by that opinion.

Correspondence bias

Tendency to overestimate the contribution of lasting traits and dispositions, as opposed to situational effects, in determining people's behavior.

Obsequiousness bias

Tendency to alter responses in the direction they perceive desired by the investigator.

Unacceptability bias

Tendency of evading questions that may embarrass or invade privacy.

Projection bias

Tendency to assume that others share the same or similar thoughts, beliefs, values, or positions.

Consistency bias

Tendency to incorrectly remember one's past attitudes and behaviour as resembling present attitudes and behaviour.

Hindsight bias

Tendency to see past events as predictable, based on knowledge of later events. Also known as the "I-knew-it-all-along" effect.

Optimism bias

Tendency to be over-optimistic about the outcome of planned actions.

Outcome bias

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

Positive bias

Tendency to test hypotheses with positive rather than negative examples, thus risking to miss obvious disconfirming tests.

Positive outcome bias

Tendency to overestimate the probability of good things happening to them.

Groupthink bias


Tendency of humans to tend to agree with each other, and hold back objections or dissent even when the group is wrong.

Conformity bias

Tendency to behave similarly to others in a group, even if doing so goes against your own judgment.

Ingroup bias

Tendency to give preferential treatment to others they perceive to be members of their own groups.

Homogeneity bias

Tendency of people to see members of their own group as being relatively more varied than members of other groups.

Shared information bias

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.

Bandwagon fallacy

Assuming that an idea has merit simply because many people believe it or practice it.


Ambiguity effect

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

Bizarreness effect

Tendency to remember bizarre material better than common material.

Bystander effect

Tendency for individuals to less likely offer help in an emergency situation when other people are present.

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.

Example: Recall time and accuracy for a work-related memory will be lower at home, and vice versa.

Contrast effect

Enhancement or diminishment of a weight or other measurement when compared with recently observed contrasting object.

Cross-race effect

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

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.

False consensus effect

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

Forer effect

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. Also known as the Barnum Effect. Like Horoscopes.

Motivated cognition

Tendency to process information toward conclusions that suit some end or goal.

Generation effect

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

Google effect

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

Halo effect

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.

Hostile media effect

Tendency to perceive news coverage as biased against your position on an issue.

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.

Lake wobegon effect

Tendency to report flattering beliefs about oneself and believe that one is above average.

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.

Mere exposure effect

Tendency to express undue liking for things merely because they are familiar with them.

Misinformation effect

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

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.

Overconfidence effect

Tendency of being more certain than is justified, given your priors and the evidence available.

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.

Picture superiority effect

The notion 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.

Positivity effect

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

Primacy effect

Tendency to weigh initial events more than subsequent events.

Processing effect

That information that takes longer to read, and is processed with more difficulty, is more easily remembered.

Pseudocertainty effect

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

Recency effect

Tendency to weigh recent events more than earlier events.

Self-relevance effect

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

Spacing effect

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

Spotlight effect

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

Subadditivity effect

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

Suffix effect

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

Telescoping effect

Tendency to perceive recent events to have occurred more remotely and remote events appear to have occurred more recently.

Testing effect

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

Underconfidence effect

State of being more uncertain than is justified, given your priors and the evidence you are aware of.

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.

Von restorff effect

Tendency to remember an item that "stands out like a sore thumb", more than other items.

Zeigarnik effect

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

Focusing effect

Tendency of placing too much importance on one aspect of an event; causes error in accurately predicting the utility of a future outcome.

Endowment effect

Tendency to demand much more to give up an object than they would be willing to pay to acquire it.

Next-in-line effect

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


Conjunction fallacy

Assumption that specific conditions are more probable than general ones.

Detached lever fallacy

Assumption that something simple for one system will be simple for others.

Gambler's fallacy

Assumption that individual random events are influenced by previous random events. Ex: 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.

Mind projection fallacy

Assumption that the way you see the world reflects the way the world really is.

Typical mind fallacy

Assumption that other people are more like you than they actually are.

Fallacy of gray

Assumption that because nothing is certain, everything is equally uncertain. It does not take into account that some things are more certain than others.

The Sophisticate: "The world isn't black and white. No one does pure good or pure bad. Therefore, no one is better than anyone else." The Zetet: "Knowing only gray, you conclude that all grays are the same shade. You mock the simplicity of the two-color view, yet you replace it with a one-color view."

Planning fallacy

Underestimating task-completion times.

Sunk cost fallacy

Letting past investments interfere with decision-making in the present.

Giant cheesecake fallacy

Occurs when an argument leaps directly from capability to actuality, without considering the necessary intermediate of motive.

Narrative fallacy

A vulnerability to over-interpretation and our predilection for compact stories over raw truths.

Scales of justice fallacy

Error of using a simple polarized scheme for deciding a complex issue/ each piece of evidence about the question is individually categorized as supporting exactly one of the two opposing positions.

Top 1% fallacy

Related to not taking into account the idea that a small sample size is not always reflective of a whole population and that sample populations with certain characteristics, e.g. made up of repeat job seekers, are not reflective of the whole population.

Fallacy of relative privation

Error of thinking that if something is worse than the problem currently being discussed, then the problem currently being discussed isn't that important at all. In other words: nothing matters if it's not literally the worst thing happening


Asymmetric insight

Tendency to perceive the knowledge of their peers to surpass their peers' knowledge of them.


Tendency to believe they can control or at least influence outcomes that they clearly cannot.

External agency

Tendency to perceive self-generated preferences as instead being caused by insightful, effective and benevolent agents.

Truth effect

Tendency to identify as true statements familiar statements over unfamiliar ones.


Tendency to perceive patterns where actually none exist.


Tendency to notice something everywhere after having learnt about it. Also known as the Baader-Meinhof Phenomenon.


Tendency to overestimate others' ability to know them, and they also overestimate their ability to know others. Misleading impression that your words convey more to others than they really do.



Mental shortcut where highly untypical situations are classified as absurd or impossible.


Mental shortcut basing a decision on an emotional reaction rather than a calculation.


Mental shortcut that treats easily recalled information as important or more important than alternative solutions which are not as readily recalled.


Mental shortcut where people judge the probability or frequency of a hypothesis by considering how much the hypothesis resembles available data as opposed to using a Bayesian calculation.

Oscean In DevelopmentDotgrid 2016—2017Rotonde In DevelopmentRonin 2016—2017Markl In DevelopmentMarabu 2017Left 2017Nataniev In DevelopmentLietal 2007—2017Horaire In DevelopmentVerreciel 2013—2017Getapan 728k 2017Paradise 2011—2017Oquonie 2013—2017Known magye 2013—2017Collected works 2008—2017Children of bramble 2012—2017Dei dain 2013—2017Thousand rooms 2017Supervisitor 2014—2017Superworker 2017Extended sleep 2015—2017Donsol 2015—2017Portalion 2016Vocavularist 2013—2016Verreciel soundtrack 2016Domestic Moire 2016Bifurcan 2013—2016Mute In DevelopmentNoirca 2014—2015Keyboard 468 2014—2015Alphavetist 2013—2015The opal inquisitors 2015Looking glace 2015Dew 2014—2015Hiversaires 2013—2015Rafinograde 2014—2015Entaloneralie 2013—2015Eschatolor 2015Ledoliel 2014—2015Malice 2008—2015Ramiel 2015Miniscopie 2015Damoiseau canalx 2014Purgateus 2014Vast 2014Telekinetic 2013Milavrega In DevelopmentEhrivevnv Studies 2012—2013Nor let the fools 2013To The Aeons Hell 2010—2012Vetetrandes lettres 2012Pico battle 2012Es gulf sunflowers 2011—2012Volkenessen 2012From Saharaphorest 2011The Sixth Season 2011Blam 2011Vermillionth 2011Pico 2010Merure 2009—2010Idyllic miners 2010Ann yozora saint 2009—2010Shikanokoa vs 1h1d 2010Pedestrian paradise 2009Nether esper inserts 2008—2009Otoroutes Miniatures 2009Downtemperature 2007—2008Vert kirlian theatre 2008Regionsteam snowdays 2006
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