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Cognitive biases are systematic patterns of deviation from rational judgment that occur as the human brain processes and interprets information.  These biases often stem from heuristics, or mental shortcuts, which allow the brain to make decisions quickly and efficiently but can lead to flawed conclusions and inaccurate perceptions of reality. These biases usually operate beneath the surface of conscious awareness, influencing memory recall, perception, and reasoning without the individual realizing it. They are perceptual errors that occur on a subconscious level, but can be hijacked by external actors in order to influence behavior.

Cognitive biases often fuel logical fallacies, allowing them to persist undetected, but belong to the internal world of the human mind.  A cognitive bias is an internal, psychological predisposition that affects how humans process and interpret information. A logical fallacy, on the other hand, is an external error in the structure of an argument that occurs during reasoning or communication.

Below is a comprehensive list of 239 cognitive biases and their definitions.

List of Cognitive Biases

• Action Bias – Preference for taking action over inaction, even when waiting would be better.
• Actor-Observer Bias – Attributing one’s own actions to external factors while attributing others’ actions to their personality.
• Additive Bias – Tendency to solve problems by adding elements rather than removing or simplifying them.
• Aesthetic–Usability Effect – Perceiving aesthetically pleasing designs as more functional or usable than they actually are.
• Affinity Bias – The unconscious tendency to favor, trust, and feel more comfortable around people who share similar backgrounds, interests, and experiences as ourselves.
• Agent Detection Bias – Inclination to interpret ambiguous stimuli or events as caused by intentional agents.
• Ambiguity Effect – Avoiding options with unknown probabilities even when they might be superior.
• Anchoring Bias – Over-relying on the first piece of information encountered when making decisions.
• Anthropomorphism – Attributing human characteristics or intentions to non-human entities or events.
• Association Bias – Linking unrelated concepts based on superficial similarities.
• Assumed Similarity Bias – Overestimating how similar other people’s attitudes and beliefs are to one’s own.
• Attentional Bias – Tendency to focus on certain stimuli (often emotionally salient) while ignoring others.
• Attention Bias – Selective attention toward specific types of information, often threat-related in anxiety.
• Authority Bias – The tendency to unquestioningly attribute greater accuracy, credibility, or truth to the opinions and instructions of perceived authority figures.
• Automation Bias – Over-trusting automated systems or decisions, even when evidence suggests error.
• Availability Cascade – A self-reinforcing process where a collective misperception gains plausibility through repetition in public discourse.
• Availability Heuristic – Judging probability based on how easily examples come to mind.
• Backfire Effect – Strengthening of a belief when presented with contradictory evidence.
• Bandwagon Effect – Adopting beliefs or behaviors because many others are doing so.
• Barnum Effect (Forer Effect) – Tendency to accept vague or general statements as personally accurate.
• Base Rate Fallacy – Ignoring general statistical information in favor of specific case details.
• Belief Bias – Evaluating the strength of an argument based on the believability of its conclusion rather than logical validity.
• Ben Franklin Effect – Liking someone more after doing them a favor, as the mind rationalizes the effort.
• Berkson’s Paradox – Spurious correlation arising from studying a restricted subset of a population.
• Bias Blind Spot – Recognizing biases in others while failing to see them in oneself.
• Bikeshedding (Parkinson’s Law of Triviality) – Focusing excessive attention on trivial issues while neglecting important ones.
• Bizarreness Effect – Better memory for unusual or bizarre material compared to common information.
• Boundary Bias – Misjudging probabilities near category boundaries.
• Boiling The Frog – The tendency of people to fail to notice or respond to gradual, incremental negative changes or deteriorating conditions until it becomes too late to escape or reverse them effectively.
• Cheerleader Effect – Perceiving individuals as more attractive when seen in a group.
• Childhood Amnesia – Inability to recall events from early childhood, typically before age 3-4.
• Choice-Supportive Bias – Remembering chosen options as better than they were and rejected options as worse.
• Clustering Illusion – Seeing patterns or streaks in random sequences.
• Cognitive Dissonance – Discomfort from holding conflicting beliefs or values, leading to rationalization.
• Common Source Bias – Over-reliance on information from a single source or similar sources.
• Compassion Fade – Reduced empathy or willingness to help as the number of victims increases.
• Confirmation Bias – Seeking or interpreting evidence in ways that confirm preexisting beliefs.
• Congruence Bias – Testing hypotheses by direct confirmation rather than attempting falsification.
• Conjunction Fallacy – Judging a specific conjunction of events as more probable than a single event.
• Conservatism Bias – Slow to update beliefs in light of new evidence.
• Consistency Bias – Misremembering past attitudes or behaviors to align with current ones.
• Continued Influence Effect – Persisting belief in misinformation even after it has been corrected.
• Contrast Effect – Perception of something influenced by comparison to something else.
• Correspondence Bias – Overemphasizing someone’s personality or character traits while ignoring the situational circumstances that might have actually caused their behavior. See: Fundemental Attribution Error (synonym).
• Courtesy Bias – Giving positive or socially acceptable responses rather than honest ones.
• Cross-Race Effect – Difficulty recognizing or distinguishing faces from racial groups different from one’s own.
• Cryptomnesia – Mistaking imagined or previously encountered ideas as original.
• Cue-Dependent Forgetting – Failure to recall information without relevant retrieval cues.
• Curse Of Knowledge – Difficulty imagining what it is like not to know something once you know it.
• Dehumanization – Denying full humanity to others, facilitating harm or indifference.
• Declinism – Belief that society or institutions are in irreversible decline.
• Decoy Effect – Preferences changing when a third, asymmetrically dominated option is introduced.
• Default Effect – Sticking with pre-set options due to inertia.
• Defamation Bias – Overemphasizing negative information about others.
• Denomination Effect – Spending smaller denominations more readily than larger ones.
• Digital Amnesia – Forgetting information that is easily accessible online.
• Disposition Effect – Holding losing investments too long and selling winning ones too soon.
• Distinction Bias – Overvaluing differences when options are compared side-by-side versus separately.
• Distinctiveness-Based Illusory Correlations – Perceiving relationships between rare or distinctive events/people.
• Domain Neglect Bias – Ignoring the broader context or domain when estimating probabilities.
• Double Standard – Applying different rules, principles, or evaluations to similar situations based on who is involved.
• Doubling-Back Aversion – Reluctance to reverse a decision or path once committed.
• Dread Aversion – Greater emotional weight given to dreaded outcomes compared to positive ones.
• Dunning-Kruger Effect – Low-ability individuals overestimating their competence.
• Duration Neglect – Judging experiences based on peak and end moments rather than total duration.
• Effort Justification – Valuing outcomes more when significant effort was invested.
• Empathy Gap – Underestimating how emotions will influence future decisions.
• Endowment Effect – Valuing something more highly simply because you own it.
• Essentialism – Assuming things have inherent, fixed essences or traits.
• Euphoric Recall – Over-idealizing past positive experiences while minimizing negatives.
• Exaggerated Expectation – Overestimating the likelihood or magnitude of future outcomes.
• Experimenter’s Bias – Researcher expectations unconsciously influencing results.
• Extraneous Factors In Judicial Decisions – Irrelevant external factors (e.g., hunger) affecting judges’ rulings.
• Extrinsic Incentives Bias – Over-relying on external rewards at the expense of intrinsic motivation.
• Fading Affect Bias – Negative emotions associated with memories fading faster than positive ones.
• False Consensus Effect – Overestimating how widely one’s opinions or behaviors are shared.
• False Memory – Recalling events that did not actually occur.
• False Priors – Starting with flawed assumptions that skew subsequent reasoning.
• Form Function Attribution Bias – Assuming an object’s function based solely on its appearance.
• Fluency Heuristic – Judging ideas as better or truer when they are easier to process.
• Framing Effect – Drawing different conclusions from the same information depending on how it is presented.
• Frequency Illusion (Baader-Meinhof Phenomenon) – Noticing something more after first encountering it.
• Functional Fixedness – Seeing objects only in their traditional roles, limiting creative problem-solving.
• Fundemental Attribution Error – Blaming a person’s character while ignoring their circumstances.
• Gambler’s Fallacy – Believing past random events affect future ones in independent trials.
• Gender Bias – Systematic preference or prejudice based on perceived gender.
• Generation Effect – Better memory for information one generates oneself than information provided.
• Group Attribution Error – Overgeneralizing individual behavior to the entire group.
• Groupthink – Desire for harmony in a group leading to irrational or dysfunctional decisions.
• Grouping Bias – Perceiving unrelated items as related due to arbitrary grouping.
• Groupshift – Group decisions becoming more extreme than individual members’ initial positions.
• Halo Effect – One positive trait influencing overall perception of a person.
• Hard-Easy Effect – Overconfidence in easy tasks and underconfidence in hard ones.
• Hedonic Recall Bias – Misremembering past satisfaction levels based on current mood.
• Hindsight Bias – Seeing past events as more predictable than they actually were.
• Hot-Hand Fallacy – Believing a person on a streak will continue performing well in random events.
• Hostile Attribution Bias – Interpreting ambiguous actions as intentionally hostile.
• Horn Effect – Perception of a person is unduly influenced by a single negative trait or characteristic, leading to an unfairly negative judgment of their other qualities or abilities.
• Hyperbolic Discounting – Preferring smaller-sooner rewards over larger-later ones.
• Identifiable Victim Effect – Greater empathy and help for a single identified victim than for many anonymous ones.
• Ikea Effect – Valuing self-assembled or self-created items more highly.
• Illusion Of Asymmetric Insight – Believing one understands others better than they understand you.
• Illusion Of Control – Overestimating personal influence over random or external events.
• Illusion Of Explanatory Depth – Overestimating how well one understands complex systems.
• Illusion Of External Agency – Attributing personal choices to external forces.
• Illusion Of Learning – Mistaking familiarity or comprehension for true mastery.
• Illusion Of Transparency – Overestimating how well others can discern one’s internal state.
• Illusion Of Validity – Overconfidence in predictions based on subjective confidence.
• Illusory Correlation – Perceiving a relationship between variables where none exists.
• Illusory Superiority – When individuals overestimate their own positive qualities relative to average.
• Illusory Truth Effect – Repeated statements perceived as more true regardless of validity.
• Impact Bias – Overestimating the intensity and duration of future emotional reactions.
• Imposter Syndrome – Persistent doubt in one’s abilities despite evidence of success.
• Inconsistency Bias – Applying different rules, principles, or evaluations to similar situations based on who is involved. See: Double Standard (synonym).
• In-Group Bias – Favoring members of one’s own group over out-group members.
• Information Bias – Seeking information even when it cannot affect action.
• Information Loss Account – Memory distortions arising from loss of specific details over time.
• Insensitivity To Sample Size – Failing to account for sample size when assessing reliability.
• Intellectual Bias – Preferring complex intellectual explanations over simpler ones.
• Interoceptive Bias – Misinterpreting internal bodily signals.
• Irrational Escalation (Sunk Cost Fallacy) – Continuing a behavior due to prior investment despite negative outcomes.
• Just-World Hypothesis – Belief that people get what they deserve, leading to victim-blaming.
• Lag Effect – Improved long-term retention when study sessions are spaced out.
• Law Of The Instrument (Maslow’s Hammer) – Over-relying on a familiar tool regardless of suitability.
• Less-Is-Better Effect – Preferring smaller quantities when evaluated separately rather than together.
• Levels-Of-Processing Effect – Deeper semantic processing leading to better memory retention.
• Leveling and Sharpening – Memory distortion where some details are flattened and others exaggerated over time.
• Like-Me Bias – The unconscious tendency to favor, trust, and feel more comfortable around people who share similar backgrounds, interests, and experiences as ourselves. See: Affinity Bias (synonym).
• Loss Aversion – Preferring to avoid losses over acquiring equivalent gains.
• Ludic Fallacy – Misapplying game-like models to real-world messy situations.
• Masculine Bias In The Attribution Of Personhood – Viewing masculine traits as more prototypically human.
• Memory Inhibition – Actively suppressing irrelevant or unwanted memories.
• Mere Exposure Effect – Developing preference for things through repeated exposure.
• Misinformation Effect – Post-event information distorting original memory.
• Modality Effect – Better recall of the last items in a list when presented auditorily.
• Money Illusion – Focusing on nominal rather than real monetary value.
• Moral Credential Effect – Past moral behavior licensing later immoral actions.
• Moral Luck – Judging actions based on outcomes rather than intent.
• Naive Cynicism – Expecting more self-interested behavior from others than is actually present.
• Naive Realism – Belief that one’s own view of the world is objective and others are biased.
• Negativity Bias – Giving greater weight to negative information or experiences.
• Negative Valence Effect – Negative emotional tone influencing memory or judgment.
• Neuropareidolia – Neural tendency to see meaningful patterns (especially faces) in random stimuli.
• Next-In-Line Effect – Poor recall of information presented immediately before one’s turn to speak.
• Normalcy Bias – Underestimating the likelihood or impact of disasters.
• Not Invented Here – Rejecting ideas or solutions originating outside one’s group.
• Objectivity Illusion – Overestimating one’s own objectivity relative to others.
• Observer Bias – Expectations influencing what is perceived or recorded.
• Observer-Expectancy Effect – Researcher expectations subtly influencing participant behavior.
• Omission Bias – Judging harmful omissions as less severe than harmful actions.
• Optimism Bias – Believing oneself less likely to experience negative events.
• Ostrich Effect – Avoiding negative information by ignoring it.
• Outcome Bias – Judging a decision based on its result rather than the quality of the decision process.
• Out-Group Homogeneity Bias – Perceiving out-group members as more similar to each other than in-group members.
• Outgroup Favoritism – Occasionally favoring out-groups over one’s in-group in certain contexts.
• Overconfidence Effect – Excessive confidence in one’s own judgments or abilities.
• Pareidolia – Seeing meaningful patterns (e.g., faces) in random stimuli.
• Part-List Cueing Effect – Providing partial cues impairing recall of the full list.
• Peak-End Rule – Judging experiences based on their most intense point and ending rather than overall.
• Pessimism Bias – Expecting negative outcomes more than warranted.
• Phantom Effect – Perceiving stimuli that are not present.
• Picture Superiority Effect – Better memory for images than words.
• Plan Continuation Bias – Continuing with a plan despite evidence it should be abandoned.
• Planning Fallacy – Underestimating time, costs, or risks of future actions.
• Plant Blindness – Difficulty noticing or valuing plants in the environment.
• Positivity Effect – Older adults preferentially attending to and remembering positive information.
• Positive Valence Effect – Positive emotional tone influencing memory or judgment.
• Post-Purchase Rationalization – Convincing oneself that a purchase was wise.
• Present Bias – Overvaluing immediate rewards at the expense of long-term goals.
• Prevention Bias – Over-prioritizing prevention of losses over pursuit of gains.
• Primacy Effect – Better recall of the first items in a sequence.
• Probability Matching – Allocating choices proportionally to probabilities rather than optimizing.
• Processing Difficulty Effect – Information harder to process perceived as less credible or valuable.
• Pro-Innovation Bias – Overvaluing new innovations without sufficient evidence.
• Projection Bias – Assuming others share one’s current feelings or preferences.
• Proportionality Bias – Expecting causes to be proportional to effects.
• Pseudocertainty Effect – Treating uncertain outcomes as certain in multi-stage decisions.
• Pygmalion Effect – Higher expectations leading to improved performance.
• Psychophysical Principle – The observation that the smallest change in a physical stimulus detectable by a person (the just noticeable difference) is a constant proportion of the original stimulus intensity, rather than a fixed absolute amount.
• Quantification Bias – Over-relying on measurable data while ignoring unquantifiable factors.
• Reactance – Motivational response to perceived threats to freedom, leading to opposite behavior.
• Reactive Devaluation – Devaluing proposals simply because they come from an opponent.
• Recency Effect – Better recall of the most recently presented items.
• Recency Illusion – Believing a recently noticed phenomenon is new or increasing.
• Reference Dependence – Evaluating outcomes relative to a reference point rather than absolute value.
• Regressive Bias – Predicting extreme scores will move toward the mean.
• Reminiscence Bump – Enhanced recall of autobiographical events from adolescence and early adulthood.
• Repetition Blindness – Failing to detect repetitions in rapid visual sequences.
• Restraint Bias – Overestimating one’s ability to resist temptations.
• Rhyme As Reason Effect – Finding rhyming statements more truthful or persuasive.
• Risk Compensation (Peltzman Effect) – Taking greater risks when protected.
• Rosy Retrospection – Remembering past events more positively than experienced.
• Salience Bias – Overweighting vivid or prominent information.
• Scope Neglect – Insensitivity to the magnitude or scale of a problem.
• Selective Perception – Filtering information to match expectations or desires.
• Self-Enhancement Bias – Inflating one’s positive qualities relative to others.
• Self-Relevance Effect – Better memory for information related to oneself.
• Self-Serving Bias – Attributing successes internally and failures externally.
• Semmelweis Reflex – Automatically rejecting new evidence that contradicts established norms.
• Serial Position Effect – Better recall of items at the beginning (primacy) and end (recency) of a list.
• Sexual Overperception Bias – Men overestimating women’s sexual interest.
• Shared Information Bias – Groups focusing on already-shared information rather than unique knowledge.
• Social Comparison Bias – The tendency for individuals to devalue, dislike, or actively undermine others who outperform them in domains relevant to their self-image, in order to protect their own self-esteem and relative standing.
• Social Cryptomnesia – Forgetting the social or external origin of ideas.
• Social Desirability Bias – Responding in ways perceived as socially acceptable.
• Social Desirability Response Bias – Answering surveys to appear favorable.
• Source Confusion – Misattributing the source of a memory.
• Spacing Effect – Better long-term retention when learning is spaced over time.
• Spotlight Effect – Overestimating how much others notice or judge one’s appearance or behavior.
• Status Quo Bias – Preferring things to remain as they are.
• Stereotype Bias – Applying generalized group beliefs to individuals.
• Stereotyping – Expecting individuals to possess characteristics based on group membership.
• Subadditivity Effect – Judging the probability of the whole less than the sum of its parts.
• Subjective Validation – Accepting statements as true if they feel personally relevant.
• Suffix Effect – Interference with recency effect from irrelevant trailing items.
• Suggestibility – Incorporating suggested information into one’s memory.
• Sunk Cost Fallacy – Continuing investment due to irrecoverable past costs.
• Surrogation – Using a measurable proxy as if it were the actual goal.
• Survivorship Bias – Focusing on survivors while overlooking failures.
• System Justification – Defending or rationalizing the status quo, even when disadvantaged.
• Systematic Bias – Consistent directional error in judgment or measurement.
• Teleological Bias – Assuming events or objects have inherent purpose or design.
• Telescoping Effect – Misplacing events in time, pulling distant events closer or pushing recent ones further.
• Testing Effect – Enhanced long-term memory from actively retrieving information.
• Texas Sharpshooter Fallacy – Cherry-picking data to fit a preconceived pattern.
• Third-Person Effect – Believing media influences others more than oneself.
• Time-Saving Bias – Underestimating time saved by increasing speed.
• Tip Of The Tongue – Temporary inability to retrieve known information.
• Trait Ascription Bias – Over-attributing behavior to personality rather than situation.
• Truth Bias – Tendency to assume statements are true rather than false.
• Ultimate Attribution Error – In-group positive behavior attributed to disposition, out-group to situation (and vice versa for negative).
• Unconscious Bias – Automatic prejudices operating outside conscious awareness.
• Unit Bias – Perceiving one unit (e.g., one serving) as the appropriate amount regardless of size.
• Unrealistic Optimism – Overestimating positive outcomes for oneself.
• Utility Cascade – Overestimating utility propagation in chains of events.
• Von Restorff Effect (Isolation Effect) – Better recall of distinctive or isolated items.
• Weber–Fechner Law – Perceived change in stimuli is proportional to the logarithm of the stimulus intensity.
• Well-Traveled Road Effect – Underestimating travel time on familiar routes.
• Worse-Than-Average Effect – Underestimating one’s abilities relative to others on difficult tasks.
• Zero-Risk Bias – Preference for completely eliminating small risks over larger overall reductions.
• Zero-Sum Bias – Viewing situations as zero-sum when they may be win-win.
• Zeigarnik Effect – Better memory for incomplete or interrupted tasks.