96 Cognitive Biases
John Spacey, October 19, 2015 updated on March 22, 2021
Cognitive biases are patterns of thought that lead to suboptimal outcomes such as poor decisions. Most are the result of mental shortcuts, logical errors, social factors and memory shortfalls. The following are common cognitive biases. It should be noted that cognitive biases may be illogical but can occasionally be effective nonetheless due to politics or social factors.
Above Average EffectWhen a high percentage of people rate themselves as "above average." For example, a survey in which 95% of people in a city rank themselves as having an above average family income for the area.
Acquiescence BiasA tendency for a person to agree that something is true when they are unsure.
Ambiguity EffectAvoiding choices that involve some level of uncertainty, even when they are clearly a better choice.
AnchoringRelying too heavily on the first information you receive. For example, a customer who focuses heavily on the sticker price of a used car in price negotiations.
Attitude PolarizationA tendency to harden a belief or opinion after being challenged. For example, a manager who tentatively proposes a strategy but then strongly embraces it after it is challenged by her team.
Attribute SubstitutionAttempting to solve a complex problem with a heuristic attribute that is an incorrect substitution.
Availability CascadeA faulty new idea with apparent insight that spreads quickly by social means such as a rumor or myth.
Availability HeuristicJudging things based on what's available in your memory. Often used to explain the effect of the media on people's thinking. For example, people tend to overestimate the likelihood of "newsworthy" events such as an aircraft safety incident because such events are easy to recall in memory.
Backfire EffectHardening an opinion when presented with evidence that contradicts it.
Bandwagon EffectA tendency to follow peers and other social influences such as celebrities.
Barnum EffectViewing general information as an accurate and insightful depiction of your personality. Explains the ability of fortune tellers and personality tests to impress customers with statements such as "you value friendship but also find your friends challenging from time to time."
Base Rate FallacyValuing specific information over general. For example, people may tend to think that crime is getting worse because of recent news stories when the crime rate is dropping.
Begging The QuestionA type of circular reasoning that assumes the conclusion of an argument. Often takes the form of an attempt to prove a statement with a synonym. For example, Germany is a large country because its land is vast.
Bias Blind SpotSeeing biases in others but failing to see your own biases.
Bizarreness EffectThe tendency for bizarre things to stand out as more memorable.
Cherry PickingChoosing evidence that supports your ideas while ignoring contracting evidence.
Circular ReasoningProving a conclusion with itself.
Clustering IllusionSeeing a statistically insignificant pattern in information as significant. For example, two people driving red cars just cut me off, therefore people who drive red cars are rude.
Cognitive DissonanceA feeling of discomfort that may accompany entertaining two seemingly contradictory ideas at the same time.
Cognitive InertiaA general tendency for beliefs to endure even in the face of mounting evidence that suggests they are wrong.
Complexity BiasBelieving that a complex solution is better than a simple one that achieves the same results. Denotes an irrational preference for things such as highly complex software when goals could be achieved with a far quicker, cheaper and safer approach.
Confirmation BiasA tendency to search, filter and recall information in a way that confirms what you believe.
Congruence BiasDesigning an experiment to confirm your hypothesis instead of an experiment that challenges it.
Contrast EffectThe tendency for evaluations to be influenced by context and comparisons. For example, a luxury car may be judged differently when depicted beside economy cars as opposed to cars in the same price range.
Creeping NormalityA significant problem that doesn't cause alarm because it happens slowly.
CryptomnesiaMistaking a memory for an original idea. Thought to result in unintended plagiarism.
Curse Of KnowledgeAn inability for an expert in a particular topic to understand how laypersons view the topic.
Decoy EffectThe tendency for the presence of a bad choice in a list of options to influence decisions.
Defensive Attribution HypothesisViewing an accused as more guilty when you identify with the victim.
Disposition EffectA tendency to sell an asset that has appreciated in value and hold assets that have declined in value. Often results in investors selling winners too early and holding losers into a painful decline from which they may never recover.
Dunning Kruger EffectThe tendency for beginners and unskilled individuals to overrate themselves and experts and highly capable individuals to underrate themselves.
Duration NeglectIgnoring duration in an evaluation of an experience. For example, a long boring experience may seem interesting in retrospect if it generated a few memorable moments.
Empathy GapUnderestimating emotion. For example, a manager may underestimate an employee's need for bereavement leave by viewing it with cold logic that fails to considering the magnitude of the emotions involved. It is also common for people to underestimate their own emotions when judging future events.
Expectation BiasAllowing expectations to unconsciously influence perception or methods.
False AnalogyFalsely concluding that because two things are similar in one respect that they are similar in other respects.
False Consensus EffectA tendency to think that people agree with you more than they actually do. For example, interpreting a lack of argument as agreement.
False DilemmaUnnecessarily viewing a situation as a choice between two options when in fact many options exist.
Focusing EffectFocusing too heavily on a single aspect of a decision or problem. For example, focusing on technical details to the extent that larger business issues are neglected.
Framing EffectA phenomena whereby people give different answers depending on how a question is framed.
Frequency IllusionThe perception that a newly learned phrase or fact suddenly appears everywhere.
Functional FixednessUsing something in a static, traditional way and failing to see other potential uses. Small children commonly experiment with objects to find ways to use them. As we grow older this process often ends and we see things as having static functions that potentially limit their full potential.
Fundamental Attribution ErrorA tendency to view the errors of others as the result of personal flaws but your own errors as the result of external factors such as chance. For example, a person who trips may blame an uneven surface or new shoes. However, when someone else trips they may think the person is generally uncoordinated or careless.
Gambler's FallacyViewing statistically independent events as related. For example, if a coin toss produces heads three times in a row, it may be tempting to feel that the probability of tails is growing when it's not.
Group Attribution ErrorViewing groups of people as more uniform then they are in reality. For example, falsely assuming that people from a particular country all think alike.
Halo EffectA tendency to think that someone who is good at one thing is good another thing. For example, people may assume that an accomplished programmer would make a good manager despite the fact that the two abilities are mostly unrelated.
Hard Easy EffectA tendency to underestimate difficult tasks and overestimate easy tasks.
Hasty GeneralizationA generalization based on insufficient evidence.
Hindsight BiasViewing past events as more predictable then they really were. Has broad implications in areas such as legal justice. In many cases, a failure or accident wasn't as avoidable as it appears in retrospect.
Humor EffectThe theory that humor makes information and people more memorable.
Identifiable Victim EffectA tendency to feel greater sympathy for a single identifiable victim than numerous anonymous victims.
Illusion Of Asymmetric InsightA belief that you have more insightful knowledge about people then they have about you. Associated with a sense of superior self awareness and viewing others as lacking introspective abilities.
Illusion Of ControlA tendency for a person to think that they can control things that are completely out of their control. A common example is the tendency to think of choosing lottery numbers as an ability that one can improve.
Illusion Of TransparencyOverestimating how easily others can read your thoughts and emotions.
Illusion Of SuperiorityAn individual who overestimates their own performance and abilities. Although this is illogical, in some cases it may be effective in real world scenarios as it may improve confidence and social status.
Illusory CorrelationEasily viewing things as related without much evidence.
Impact BiasOverestimating the impact of future emotional states. For example, people may overestimate how terrible they will feel if they are fired from a job.
Ingroup BiasA tendency for individuals to extend favorable treatment to someone who is viewed as being in the same group. In some cases, seemingly minor group associations such as cheering for the same sports team can trigger in-group bias.
Insensitivity To Sample SizeUnderestimating the number of samples required for a pattern to be meaningful. A common root cause of cognitive biases.
Irrational EscalationAttempting to fix a bad decision by furthering your commitment to it. Associated with a tendency to purchase more and more of an investment after its price falls.
Loss AversionA strong preference for avoiding losses over acquiring gains. For example, avoiding an investment that can result in a small loss no matter how large and probable the potential gains.
Lucky StreakA belief that someone who is lucky once has a greater chance of continued luck. In other words, independent probabilities are viewed as having a pattern defined by periods of bad or good luck.
Technology As MagicA tendency to view technology as magic and infallible. For example, it is common to have overconfidence in a seemingly advanced technology, even when an individual has no idea how it works. This neglects issues such as data quality, bugs and poorly design algorithms that render technology inaccurate.
Mere Exposure EffectA well known tendency to trust things more simply because they are familiar. For example, an individual may strongly prefer a brand that they have heard about over one that is new to them. This can occur when the individual has no positive information about the brand other then a vague sense that it sounds familiar.
Misinformation EffectWhen post-event information influences memory. For example, a witness to an event may be influenced by media coverage of it.
Mood Congruent Memory BiasThe theory that you are more likely to remember what you are in the mood to hear.
Moral LuckWhen blame or praise for a given action depends on the outcome. For example, a stock trader who makes a risky speculative investment may receive praise if it happens to work out and blame if it fails.
Normalcy BiasThe strong assumption that normal conditions will endure indefinitely despite mounting evidence that a change is on the horizon.
Not Invented HereAn organizational or individual preference to create things independently that reaches irrational levels whereby things that are available cheaply externally are recreated at high cost internally.
Omission BiasAssociating more guilt with an action than an equally harmful inaction.
Optimism BiasOverestimating the probabilities of positive things and underestimating the probability of risks.
Ostrich EffectIgnoring an obvious fact because it is unpleasant. An analogy to the untrue legend that ostriches stick their heads in sand.
Outcome BiasJudging a past decision by its outcome as opposed to the quality of the decision. Synonymous with moral luck.
Parkinsons Law Of TrivialityFocusing on trivial aspects of a complex problem because they are easier to understand. For example, an executive of a company who becomes obsessed with the interior design of a data center construction project while neglecting infrastructure issues.
Peak-End RuleA common tendency to judge an experience by its peak and end.
Pessimism BiasOverestimating difficulty and risk. Pessimism can be a personality trait or can be triggered by a particular situation such as unexpected change.
Planning FallacyA common occurrence whereby strategy and planning are affected by optimism bias. In many cases, optimism peaks near the start of a process and declines towards pessimism as things start to go wrong.
Projection BiasProjecting your thoughts and emotions on to others. For example, assuming that other people are happy when you are in a good mood.
Quantitative FallacyMaking decisions based solely on quantitative observations even when a qualitative observation strongly indicates the decision is wrong. Stems from trust in numbers without regard to their accuracy and relevance.
ReactanceReactance is a phenomena whereby people strongly react to a perceived attempt to limit their freedom of choice. For example, if a salesperson indicates that a particular item isn't suitable for a customer, the customer may buy the item out of a sense of defense of their right to choose.
Reactive DevaluationDismissing an idea because of its source. For example, automatically disagreeing with a particular foe even if they are obviously right about something.
Rhyme As Reason EffectThe theory that things that rhyme sound true.
Rosy RetrospectionRecalling past experiences as more pleasant then they actually were.
Scope NeglectIgnoring the size of a problem in an evaluation.
Selective PerceptionFiltering information according to your viewpoint.
Sharpshooter FallacyChanging your goal to match your results. Based on a story about a sharpshooter who draws a target after taking all his shots.
Slothful InductionFailing to draw a conclusion despite ample evidence for it.
Social Comparison BiasTreating someone differently who you see as competing with your strengths. For example, a manager may feel unconformable hiring someone who clearly has strong leadership skills.
Sour GrapesA tendency to criticize something you want but can't obtain. Based on a folktale about a fox who can't reach grapes so he assumes they must be sour.
Spotlight EffectThe assumption that people focus on you more than they really do. For example, if you give a presentation you may believe that people carefully considered every word when in fact they were mostly daydreaming.
Status Quo BiasA strong preference for things to remain the same that results in resistance to change.
Survivorship BiasEvaluations that only consider the winners in a given situation. For example, considering the historical success of stock investments by looking at the returns for large cap stocks over a 30 year period without considering the companies that went bankrupt or that never grew to become large firms.
System JustificationA tendency to vigorously defend prevailing social, economic, and political norms.
Time Saving BiasThe theory that people underestimate the effect of moving faster when they are moving slowly. The theory also states the opposite, that people overestimate the effect of moving faster when they are moving fast.
Well Travelled Road EffectA tendency to underestimate familiar tasks and overestimate unfamiliar tasks. For example, a programmer who is comfortable with a particular platform may be more likely to underestimate a project than a programmer who is new to it.
Worse Than Average EffectAn observation that people often think of themselves as worse than average at difficult to master abilities such as public speaking.
Zero Risk BiasDevoting excessive resources to reduce a particular risk to zero while neglecting larger risks. Associated with dread risks.
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