The 250 Cognitive Biases: Complete List with Definitions

In short: Cognitive biases are systematic mental shortcuts that distort our judgment, memories, and decisions. Identified by the foundational work of Daniel Kahneman, Amos Tversky, and Aaron T. Beck, these biases affect every individual without exception. This article catalogues more than 250 cognitive biases, classified in eight categories: judgment and decision, memory, social biases, attention and perception, emotions, couple relationships, economics, and logical reasoning. For each bias, you will find its precise definition and a concrete example. Understanding these mechanisms is the first step toward developing more lucid thinking and healthier relationships.

Our brain processes approximately 11 million bits of information per second, but our consciousness manages only 50. To bridge this vertiginous gap, the brain uses mental shortcuts called heuristics. Most of the time, these shortcuts work remarkably well. But in certain situations, they produce systematic and predictable errors: cognitive biases.

The term was popularized in the 1970s by psychologists Daniel Kahneman and Amos Tversky, whose work on judgment under uncertainty revolutionized psychology and behavioral economics. In parallel, the psychiatrist Aaron T. Beck identified cognitive distortions within the framework of cognitive behavioral therapy (CBT), showing how these automatic thought patterns fuel anxiety, depression, and relational conflicts.

Today, research has catalogued more than 250 distinct cognitive biases. This article lists them exhaustively, organized by category, with for each a clear definition and a concrete example. The goal is not to eliminate these biases — that is impossible — but to recognize them to better counter them.

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1. Judgment and Decision Biases

These biases affect how we evaluate situations, weigh options, and make decisions. They form the heart of Kahneman and Tversky's work.

Confirmation bias

Definition: Tendency to selectively seek, interpret, and remember information that confirms our pre-existing beliefs, while ignoring information that contradicts them. Example: You are convinced that your colleague is incompetent. You notice every one of their errors but retain none of their successes.

Anchoring bias

Definition: Tendency to give excessive weight to the first information received (the anchor) when making a subsequent decision, even if this information is arbitrary. Example: A seller announces an initial price of 500 euros. After negotiation, you buy at 350 euros and feel satisfied, even though the item is worth 200.

Halo effect

Definition: Tendency to let a positive (or negative) impression in one area influence our overall judgment of a person or situation. Example: A physically attractive person is automatically perceived as more intelligent, more honest, and more competent.

Availability bias

Definition: Tendency to overestimate the probability of an event based on the ease with which examples come to mind. Example: After seeing a report on a plane crash, you considerably overestimate the risk of flying, although statistics show it is the safest form of transport.

Representativeness bias

Definition: Tendency to judge the probability of an event based on its resemblance to a mental prototype, ignoring base rates. Example: Learning that Marc is calm and likes books pushes you to classify him as a librarian rather than a salesperson, when salespeople are statistically much more numerous.

Illusion of control

Definition: Tendency to believe that one can influence events over which one objectively has no power. Example: A dice player blows on their hands before rolling, convinced this ritual will improve their result.

Optimism bias

Definition: Tendency to overestimate the probability of positive events and to underestimate that of negative events concerning us. Example: The majority of smokers estimate that lung cancer will affect others, not them.

Status quo bias

Definition: Irrational preference for the current state of things, even when a change would be objectively beneficial. Example: You stay with your phone operator for ten years despite much better offers from competitors, simply because changing requires effort.

Endowment effect

Definition: Tendency to attribute a higher value to an object simply because one owns it. Example: You refuse to sell your old bicycle for 100 euros even though you no longer use it and would not buy it at that price.

Loss aversion

Definition: The pain of losing something is psychologically about twice as intense as the pleasure of gaining the same thing. Example: Losing 50 euros causes much greater distress than the joy of finding 50 euros.

Survivorship bias

Definition: Error of focusing only on people or things that have passed a selection process, while ignoring those that failed. Example: Citing Bill Gates as proof that dropping out of college leads to success, forgetting the millions of dropouts who did not succeed.

Hindsight bias

Definition: Tendency to believe, after an event has occurred, that one had predicted it or that it was inevitable. Example: After a stock market crash, claiming that all the signals were obvious and that one knew it was going to happen.

Dunning-Kruger effect

Definition: People who are not very competent in a field overestimate their abilities, while experts underestimate theirs. Example: A novice driver considers themselves an excellent pilot, while a professional pilot constantly doubts their performance.

Overconfidence bias

Definition: Excessive confidence in the accuracy of one's own judgments and predictions. Example: An investor is 95% certain that their investment will triple, when historical data shows that 70% of similar predictions fail.

Framing effect

Definition: The way information is presented influences our decision, even if the objective content is identical. Example: A yogurt presented as "90% fat-free" is judged healthier than the same yogurt labeled "10% fat".

Contrast effect

Definition: Our evaluation of an element is modified by comparison with a previous element. Example: An average candidate at a job interview appears excellent if they come right after a mediocre candidate.

Omission bias

Definition: Tendency to judge harmful actions as morally worse than inactions that produce the same result. Example: Not vaccinating one's child is perceived as less serious than administering a vaccine with equivalent side effects.

Normalcy bias

Definition: Tendency to underestimate the possibility and impact of a disaster, assuming that things will continue to function normally. Example: Residents refuse to evacuate despite a hurricane warning, convinced it will not be as serious as announced.

Impact bias

Definition: Tendency to overestimate the intensity and duration of our future emotional reactions, both positive and negative. Example: You think that a romantic breakup will destroy you for years, when in reality adaptation occurs in a few months.

Projection bias

Definition: Tendency to assume that our current preferences, thoughts, and values will remain the same in the future. Example: Shopping while hungry and buying far too much, because you project your current hunger onto the future.

Decoy effect

Definition: The introduction of a third option, inferior to one of the first two, pushes toward choosing the dominant option. Example: A subscription at 59 euros appears reasonable when placed next to a premium subscription at 125 euros and a useless intermediate one at 119 euros.

Distinction bias

Definition: Tendency to perceive two options as more different when evaluated simultaneously than separately. Example: In the store, two televisions side by side seem very different in image quality. At home, you would see no difference.

Ambiguity aversion

Definition: Preference for options whose probabilities are known, even if unfavorable, rather than options with unknown probabilities. Example: Preferring a guaranteed 2% bank investment over an investment that yields an average of 8% but with uncertainty.

Outcome bias

Definition: Judging the quality of a decision based on its outcome rather than the quality of the decision-making process at the time it was made. Example: A doctor who prescribes a risky treatment is considered brilliant if the patient recovers, and incompetent if the patient does not recover, regardless of the correctness of their reasoning.

False consensus effect

Definition: Tendency to overestimate the degree to which others share our opinions, beliefs, and behaviors. Example: A vegetarian is surprised to find that the majority of their colleagues eat meat, because they assumed many shared their choice.

Ostrich effect

Definition: Tendency to deliberately ignore negative or threatening information. Example: Never checking your bank statements when you know you are overspending.

Choice-supportive bias

Definition: After making a choice, tendency to remember it as better than it was and to minimize the defects of the chosen option. Example: After buying a car, you exaggerate its qualities and minimize its defects compared to the models you rejected.

IKEA effect

Definition: Tendency to grant disproportionate value to things one has oneself created or assembled. Example: You are more proud of your wobbly hand-assembled shelf than of a designer piece of furniture bought in store.

Bias blind spot

Definition: Ability to spot cognitive biases in others while being unable to recognize one's own. Example: You clearly identify the confirmation bias in your conspiracy theorist friend, but do not see the one guiding your own reading of the news.

Unit bias

Definition: Tendency to want to finish a given unit (a dish, an episode, a chapter) regardless of the size of this unit. Example: You finish your plate even if you are no longer hungry, simply because the portion mentally defines a complete unit.

Bandwagon effect

Definition: Tendency to adopt a belief or behavior because many other people are doing it. Example: Buying a cryptocurrency only because everyone is talking about it, without understanding the underlying technology.

Reactive devaluation

Definition: Tendency to devalue a proposal simply because it comes from an opponent or someone we do not like. Example: Rejecting a reasonable peace offer only because it comes from the opposing camp.

Zero-risk bias

Definition: Preference for completely eliminating a small risk rather than significantly reducing a much larger risk. Example: Spending a fortune to completely remove the risk of a minor contaminant in drinking water, rather than halving the risk of air pollution, which is far more dangerous.

Face value bias

Definition: Tendency to accept a statement as it is presented, without seeking to verify its veracity. Example: Believing a statistic shared on social media without verifying its source.

Reciprocity bias

Definition: Felt obligation to return the favor when someone has done us a favor, even unsolicited. Example: Buying a product from a seller who offered you a free sample, even if you do not need it.

Rhetoric bias

Definition: Tendency to be convinced by the form of an argument (eloquence, assurance) rather than by its content. Example: A charismatic speaker who asserts absurdities with confidence is more persuasive than a timid expert who states truths.

Default effect

Definition: Tendency to accept the default option, even if it does not correspond to our preferences. Example: The majority of employees keep the default distribution of their retirement savings plan, even if it is suboptimal.

Pseudocertainty effect

Definition: Tendency to treat as certain results that are only probable, when the expected gain is positive. Example: Preferring a sure gain of 3000 euros over an 80% chance of winning 4000 euros, even though the mathematical expectation of the second choice is higher.

Semmelweis reflex

Definition: Tendency to automatically reject new information or discovery that challenges an established paradigm. Example: 19th-century doctors rejected Semmelweis's hand-washing recommendations, preferring their existing beliefs.

Illusion of knowledge

Definition: Feeling of understanding a subject much better than one actually understands it. Example: Being unable to explain the operation of a zipper, when you thought you understood it perfectly.

Completion bias

Definition: Disproportionate motivation to finish a task already begun, regardless of its real value. Example: Watching a boring film at the cinema to the end because you paid for your seat and started watching it.

Sample size neglect

Definition: Tendency to draw conclusions from a sample too small to be statistically significant. Example: Concluding that a restaurant is bad after a single disappointing visit.

Focusing effect

Definition: Giving too much importance to a single aspect of a situation when making a decision. Example: Choosing an apartment only for its view, neglecting noise, transport, and space.

Probability neglect

Definition: Tendency to completely ignore probabilities when an emotionally charged outcome is at stake. Example: Refusing to fly despite an accident probability of 1 in 11 million, because the idea of a crash is terrifying.

Proportionality bias

Definition: Belief that big events must have big causes, and vice versa. Example: Difficulty accepting that a president could have been assassinated by a lone gunman, which fuels conspiracy theories.

Illusion of validity

Definition: Tendency to overestimate the accuracy of one's predictions when the data presents an apparent pattern, even if this pattern is random. Example: A recruiter convinced of detecting good candidates in interviews, despite studies showing that unstructured interviews are poorly predictive.

Attribute substitution

Definition: When a complex question is too difficult, the brain unconsciously substitutes a simpler question. Example: To the question "Are you satisfied with your life?", you actually answer "What is my mood right now?"

Mere measurement effect

Definition: Simply asking someone if they intend to do something increases the likelihood that they will do it. Example: Asking people if they plan to vote actually increases voter turnout.

Peltzman effect

Definition: Safety measures increase risk-taking behaviors, as individuals feel protected. Example: Drivers wearing seat belts drive faster and more aggressively.

Zero-sum bias

Definition: Tendency to perceive situations as zero-sum games, where one person's gain necessarily implies another's loss. Example: Believing that a colleague's success automatically reduces your chances of promotion.

Planning fallacy

Definition: Systematic tendency to underestimate the time, costs, and risks of a future action. Example: Estimating a renovation project at three months and 10,000 euros, when it will take eight and cost 25,000 euros.

Illusory truth effect

Definition: A repeated statement is perceived as more true than a statement heard for the first time, regardless of its veracity. Example: An advertisement repeated dozens of times ends up seeming credible to you, even if the product has no proof of effectiveness.

Just-world hypothesis

Definition: Belief that the world is fundamentally just and that people get what they deserve. Example: Thinking that a victim of theft must have been careless, or that a poor person does not work hard enough.

Mere ownership effect

Definition: Tendency to evaluate an object more favorably simply because one owns it. Example: Estimating that your house is worth 20% more than market estimates.

Negativity dominance

Definition: In the overall evaluation of a set, negative elements weigh more heavily than positive elements of equal intensity. Example: A single negative review out of 50 positive reviews is enough to deter you from buying a product.

Belief bias

Definition: Tendency to evaluate the logical validity of an argument based on the plausibility of its conclusion rather than the structure of the reasoning. Example: Accepting an invalid syllogism because the conclusion seems true (for example: "All dogs are animals. All cats are animals. Therefore all cats are dogs" would be rejected, but an equally false reasoning with a plausible conclusion would be accepted).

Illusion of transparency

Definition: Overestimation of others' ability to understand our internal states, or of our ability to understand theirs. Example: Being convinced that everyone sees that you are nervous during a presentation, when no one notices.

Third-person effect

Definition: Belief that the media influences others more than oneself. Example: Thinking that advertising manipulates other consumers but not you.

Conjunction fallacy

Definition: Judging that two simultaneous events are more likely than just one of these events taken in isolation. Example: Judging it more likely that Linda is "a cashier and a feminist" rather than simply "a cashier", after learning that she was socially engaged.

Information bias

Definition: Belief that more information always leads to better decisions, even when the additional information is irrelevant. Example: Requesting additional medical tests when the diagnosis is already clear, thus delaying the start of treatment.

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2. Memory Biases

These biases affect how we encode, store, and retrieve memories. Memory is not a faithful recording: it is a permanent reconstruction.

Recency effect

Definition: Tendency to better remember the last elements of a series or the most recent events. Example: During an annual review, the manager evaluates the employee mainly on the last weeks of work.

Primacy effect

Definition: Tendency to better remember the first elements of a series. Example: The first candidate in a job interview often has an advantage, because their performance remains more vivid in the recruiter's memory.

Selective memory

Definition: Tendency to retain only memories that confirm our beliefs or identity, while forgetting others. Example: Remembering all the times your intuition was correct, but forgetting the dozens of times it deceived you.

False memory

Definition: Memory of an event that never occurred, or distorted memory of a real event, felt with the same certainty as a true memory. Example: Being convinced you were lost in a shopping mall as a child, after relatives have repeatedly talked about it.

Google effect

Definition: Tendency to remember less well information one knows one can easily find online. Example: Being unable to remember the name of an actor because you know you can search for them on the internet in three seconds.

Cryptomnesia

Definition: Taking as an original idea something one has actually heard or read before, without remembering the source. Example: Proposing an innovative solution in a meeting, when a colleague had put forward exactly the same idea three months earlier.

Misinformation effect

Definition: Information received after an event modifies and alters the memory of that event. Example: A witness who hears about a "blue" car after an accident unconsciously modifies their memory and now believes the car was blue, even if it was green.

Consistency bias

Definition: Tendency to reconstruct one's past memories to match one's current attitudes and beliefs. Example: After a breakup, convincing oneself that one had "never really" been happy in that relationship.

Spacing effect

Definition: Information studied in a spaced manner over time is better memorized than that revised in bulk. Example: Reviewing vocabulary for 15 minutes a day for a week is more effective than reviewing it for 2 hours in a row.

Serial position effect

Definition: Items at the beginning and end of a list are better memorized than those in the middle. Example: In a grocery list of 20 items, you remember the milk (first) and the bread (last), but forget the yogurts (middle of the list).

Rosy retrospection

Definition: Tendency to remember past events more positively than they were actually experienced. Example: Recalling one's childhood vacations as perfect, forgetting the rain, arguments, and boredom.

Leveling and sharpening

Definition: When recounting a memory, some details are blurred (leveling) while others are exaggerated (sharpening). Example: When recounting a road incident, the driver exaggerates the speed of the other vehicle and omits their own errors.

Duration neglect

Definition: The evaluation of an experience depends more on its intensity at its peak and end than on its total duration. Example: A painful 30-minute medical procedure with a gentle ending is judged less painful than a 10-minute procedure with a brutal ending.

Telescoping effect

Definition: Tendency to perceive recent events as older (forward telescoping) or old events as more recent (backward telescoping). Example: Believing an event took place a year ago when it occurred six months ago.

Generation effect

Definition: Information one has generated oneself is better memorized than that simply read or heard. Example: Creating your own revision sheets is more effective than rereading those of someone else.

Mood-congruent memory

Definition: Memories are more easily recalled when the current mood matches the mood at the time of encoding. Example: During depression, sad memories come back to you more easily, which reinforces the depressive cycle.

Self-reference effect

Definition: Information related to oneself is better memorized than neutral information. Example: You remember a word better if you were asked to relate it to your own experience rather than simply analyze it linguistically.

Egocentric bias

Definition: Tendency to remember one's own contributions and performance as more important than they were. Example: In a group project, each member is convinced of having done at least 50% of the work.

Suffix effect

Definition: The addition of an irrelevant element at the end of a list disrupts the recall of the last relevant elements. Example: If you add the word "end" after a list of numbers to memorize, recall of the last number is decreased.

Zeigarnik effect

Definition: Unfinished or interrupted tasks are better memorized than completed tasks. Example: A waiter perfectly remembers orders not yet served, but instantly forgets those that have been delivered.

Source monitoring error

Definition: Difficulty remembering the source of information, attributing it to a wrong origin. Example: Believing you read information in a serious newspaper when you saw it on social media.

Modality effect

Definition: Information presented audibly is better memorized (short-term) than that presented visually. Example: You remember better the last words of a heard speech than the last sentence of a read text.

Context-dependent memory

Definition: Information is more easily recalled in the same physical or mental context where it was learned. Example: Returning to your old school brings up memories you thought you had completely forgotten.

Testing effect

Definition: Testing oneself on content is more effective for memorizing it than passively rereading it, even without correction. Example: A student who self-tests retains 50% more than a student who rereads their notes the same number of times.

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3. Social Biases

These biases influence how we perceive others, interact in groups, and attribute the causes of behaviors.

Conformity effect

Definition: Tendency to align one's opinions and behaviors with those of the group, even when one knows the group is wrong. Example: Asch's experiment (1951): participants give a manifestly false answer to a simple problem, only because other group members gave this answer.

Fundamental attribution error

Definition: Tendency to explain others' behavior by their personality (internal factors) rather than circumstances (external factors), while doing the opposite for oneself. Example: Thinking that a motorist who cuts you off is an irresponsible reckless driver, while when you do it, it is because you were running late.

Bystander effect

Definition: The more witnesses there are to an emergency, the less likely each witness is to intervene. Example: In a crowded street, a person who collapses receives less help than in an empty street, because everyone assumes someone else will intervene.

Groupthink

Definition: Tendency of a cohesive group to make irrational decisions to preserve harmony and avoid conflict. Example: The management team of a company unanimously validates a risky project because no one dares to contradict the CEO.

Ingroup favoritism

Definition: Tendency to favor members of one's own group at the expense of members of an outside group. Example: A manager preferentially recruits graduates from their own school, unconsciously judging them more competent.

Pygmalion effect

Definition: The positive expectations of an authority figure toward another person effectively improve the performance of the latter. Example: Students presented as "promising" to their teacher progress more, even if this qualification was attributed randomly.

Golem effect

Definition: The negative expectations of an authority figure decrease the performance of the targeted person. Example: An employee judged incompetent by their manager effectively becomes less efficient, as they receive less responsibility and support.

Self-serving bias

Definition: Tendency to attribute one's successes to internal causes (talent, effort) and one's failures to external causes (bad luck, injustice). Example: Passing an exam thanks to one's intelligence, but failing because of an unfair teacher.

Mere exposure effect

Definition: The more we are exposed to something or someone, the more we tend to appreciate it. Example: A song you found mediocre at first listen ends up pleasing you after hearing it ten times on the radio.

Actor-observer bias

Definition: Tendency to explain one's own behavior by situational factors and that of others by personality traits. Example: Your friend is late because they are disorganized. You are late because there were traffic jams.

Horn effect

Definition: A negative trait perceived in a person negatively colors our overall judgment of them. Example: An employee who arrives late once is then perceived as unreliable in all areas.

Authority bias

Definition: Tendency to give excessive weight to the opinion of an authority figure, even outside their field of competence. Example: Following the financial advice of a famous doctor, simply because they are a doctor.

Social desirability bias

Definition: Tendency to answer what is socially acceptable rather than what one really thinks. Example: Declaring in a survey to systematically recycle, when in reality one rarely does so.

Stereotyping

Definition: Generalization of attributes to all members of a group based on supposed characteristics of the group. Example: Assuming that an elderly person is technophobic or that a young person is irresponsible.

Moral credential effect

Definition: After doing something morally positive, the person feels authorized to do something morally questionable. Example: After making a donation to a charity, allowing oneself to take a taxi rather than the metro "because one has already done one's part".

Barnum effect

Definition: Tendency to accept vague and general descriptions as perfectly suited to one's own personality. Example: Finding one's horoscope strikingly accurate, when the same description applies to almost everyone.

Composition fallacy

Definition: Assuming that what is true for one member of a group is true for the entire group, and vice versa. Example: Because an atom is invisible to the naked eye, concluding that an object composed of atoms should be too.

Effort justification

Definition: The more effort one has invested in something, the more one tends to value it, regardless of its objective quality. Example: A student who suffered during hazing evaluates their fraternity more positively than a student who entered it easily.

Overjustification effect

Definition: When an external reward is given to an intrinsically motivated behavior, intrinsic motivation decreases. Example: A child who loved drawing loses interest after being financially rewarded for each drawing.

False uniqueness bias

Definition: Tendency to underestimate the number of people who share our positive qualities and behaviors. Example: Believing oneself to be the only one recycling in one's neighborhood, when the majority of neighbors do so too.

Group polarization

Definition: After discussion, the initial positions of group members become more extreme. Example: A jury that was leaning slightly toward guilt renders a verdict of aggravated guilt after deliberation.

Dehumanization

Definition: Tendency to deprive members of an outside group of human qualities, making them psychologically easier to mistreat. Example: Using animal metaphors to designate an ethnic or social group.

Ringelmann effect

Definition: Individual productivity decreases as group size increases. Example: During a tug-of-war, each participant pulls proportionally less hard when the group is larger.

Social projection

Definition: Tendency to assume that others think and feel things the same way as oneself. Example: An introvert assuming that everyone prefers quiet evenings to big parties.

Outgroup homogeneity bias

Definition: Tendency to perceive members of an outside group as more similar to each other than members of one's own group. Example: Thinking that "all supporters of this team are the same", while seeing the members of one's own club as all unique.

Social primacy effect

Definition: The first impression during a meeting has a disproportionate and lasting impact on the evaluation of the person. Example: A candidate who smiles warmly while shaking the recruiter's hand benefits from an advantage throughout the interview.

Naive realism

Definition: Belief that our perception of reality is objective and that people who do not share our point of view are either misinformed, irrational, or dishonest. Example: During a political debate, being sincerely convinced that your position is the only rational one.

Hot hand fallacy

Definition: Belief that a person who has had a series of successes has more chances of succeeding on the next attempt. Example: A basketball player who has scored three baskets in a row is perceived as "on a roll", when each shot is statistically independent.

Freezing effect

Definition: After publicly taking a position, it becomes psychologically difficult to change, even in the face of contrary evidence. Example: A politician who publicly defended a measure refuses to abandon it despite disastrous results.

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4. Attention and Perception Biases

These biases filter, distort, or orient what we perceive of our environment.

Negativity bias

Definition: Negative stimuli have a stronger psychological impact, capture more attention, and are better memorized than positive stimuli. Example: A single critical comment during a presentation erases the memory of ten compliments.

Change blindness

Definition: Inability to detect an important change in a visual stimulus when attention is diverted. Example: In a famous video, a gorilla crosses the scene and the majority of viewers do not see it because they are counting the passes of a ball.

Salience bias

Definition: Tendency to give more importance to the most striking, unusual, or emotionally charged information or stimuli. Example: A terrorist attack (salient but rare event) holds more attention than air pollution (constant but barely visible threat), which nevertheless kills thousands more.

Frequency illusion / Baader-Meinhof phenomenon

Definition: After noticing something for the first time, one has the impression of seeing it everywhere. Example: After learning the word "serendipity", you have the impression of reading it in every article and hearing it in every conversation.

Inattentional blindness

Definition: Not perceiving a visible and present stimulus when it is not the object of our attention. Example: A pedestrian absorbed in their phone who does not see a clown on a unicycle right in front of them (real experiment by Western Washington University).

Perceptual confirmation

Definition: Seeing what one expects to see, interpreting ambiguous stimuli in accordance with our expectations. Example: Hearing an ambiguous sound as a precise word when one has an expectation about what the person is going to say.

Von Restorff effect

Definition: An element that stands out from others in a set is better memorized. Example: In a list of black words, a word written in red is retained much more easily.

Attentional bias

Definition: Tendency to pay disproportionate attention to certain stimuli based on our concerns, emotions, or addictions. Example: An anxious person detects a threatening face in a crowd much faster than a serene person.

Pareidolia

Definition: Tendency to perceive a meaningful pattern (often a face) where there is none. Example: Seeing a face in the clouds, in electrical outlets, or on the surface of the moon.

McGurk effect

Definition: Visual information (lip movement) modifies auditory perception, even when the sound is clearly different. Example: Hearing "da" when the sound says "ba" but the lips form "ga".

Perceptual defense

Definition: Increase in the perception threshold for threatening, embarrassing, or anxiety-inducing stimuli. Example: Taking longer to recognize a taboo word during a rapid perception test.

Word superiority effect

Definition: Letters are identified faster when they are part of a word than when they are isolated. Example: Recognizing the "A" in "CAT" faster than the "A" presented alone.

Cocktail party effect

Definition: Ability to focus one's auditory attention on a conversation in a noisy environment, while remaining sensitive to certain stimuli (such as one's own name). Example: At a noisy party, you immediately hear when someone says your name across the room.

Hedonic adaptation

Definition: Tendency to return quickly to a stable level of happiness after a major positive or negative event. Example: Lottery winners are not significantly happier a year after their winning than non-winners.

Size bias

Definition: Tendency to judge the quantity or importance of something based on its physical size. Example: A calorie supplement presented in a small container appears more substantial than the same supplement in a large container.

Attentional focusing effect

Definition: Attention focused on an attribute increases its perceived importance in judgment. Example: Asking someone to think about the climate of a city pushes them to overestimate the importance of climate in their choice of place to live.

Base rate neglect

Definition: Ignoring base rates in favor of specific information, even if the latter is unreliable. Example: A positive medical test (99% reliability) for a disease affecting 1 in 10,000 people actually gives less than 1% chance of being really ill.

Figure-ground bias

Definition: Our perception automatically organizes the visual field into a figure (object of attention) and a ground (ignored context), which can lead to erroneous interpretations. Example: The Rubin vase illusion, where one sees sometimes a vase, sometimes two faces, depending on what the brain selects as figure.

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5. Emotional Biases

These biases show how emotions influence and distort rational judgment. They are at the heart of cognitive-behavioral therapy and particularly relevant in couple relationships.

Emotional reasoning

Definition: Taking one's emotions as proof of reality: "I feel it, therefore it's true." Example: "I feel incompetent, therefore I am incompetent." For an in-depth analysis, see our article on emotional reasoning in couples.

Affect heuristic

Definition: Basing one's judgments and decisions on emotions felt in the moment rather than on objective analysis. Example: Judging a technology as safe when one appreciates it (solar energy) and dangerous when one does not appreciate it (nuclear), regardless of actual safety data.

Empathy gap (cold-hot)

Definition: Difficulty understanding or predicting one's own behaviors and emotions in an emotional state different from the current state. Example: When you are calm, you are convinced you would never give in to anger. But in the middle of an argument, you say things you regret.

Positivity bias

Definition: Tendency to evaluate others more positively than objective data justifies. Example: Performance evaluations in companies are overwhelmingly positive: 80% of employees are rated "above average".

Sunk cost fallacy (emotional dimension)

Definition: Emotional attachment to what has already been invested (time, money, effort) pushes one to continue an action doomed to failure. Example: Staying in an unhealthy relationship because you have invested eight years and "it would be a waste to leave now".

Emotional focusing bias

Definition: The current emotional state colors all judgment, not just the evaluation related to the emotion. Example: After a stressful day at work, judging that your entire life is a failure.

Regret aversion

Definition: Making decisions to avoid feeling regret rather than to maximize benefits. Example: Not investing in the stock market for fear of losing money, even if the expected return is significantly higher than a savings account.

Visceral influence

Definition: Intense bodily states (hunger, pain, excitement) profoundly alter judgment and decision-making. Example: Making impulsive food shopping decisions when shopping while hungry.

Compassion fade

Definition: Empathy and willingness to help diminish as the number of victims increases. Example: The story of a sick child elicits more donations than a report on a million refugees.

Present bias (immediate gratification)

Definition: Excessive preference for immediate rewards at the expense of more important future rewards. Example: Choosing to watch a series tonight rather than study for an exam next week.

Peak-end rule

Definition: The emotional evaluation of an experience is determined by the most intense moment (peak) and the end, not by the average of the experience. Example: Vacations with a magical moment and a beautiful ending are judged better than uniformly pleasant vacations.

Arousal bias

Definition: Physiological arousal (positive or negative) intensifies emotional responses and alters judgment. Example: After intense physical activity, finding the person in front of you more attractive than usual (Dutton and Aron's suspension bridge effect).

Affect congruence

Definition: Judgments tend to be coherent with the current mood: joyful, one sees everything in rose; sad, in black. Example: Evaluating your professional future as promising on a sunny day and dark on a rainy day.

Identity-protective cognition

Definition: When facts threaten our identity or fundamental values, we reject or reinterpret them to preserve our self-image. Example: Rejecting solid climate data because it contradicts the political values with which one identifies.

Immune neglect

Definition: Underestimation of our psychological ability to adapt and recover from negative events. Example: Being convinced that a layoff would be the end of the world, when in reality one bounces back in a few months.

Catharsis illusion

Definition: Believing that the violent expression of anger (hitting a pillow, screaming) reduces it, when studies show it amplifies it. Example: After yelling at someone, feeling even angrier and not relieved.

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6. Couple and Relationship Cognitive Biases

These biases are particularly studied in couple therapy (CBT) and constitute major therapeutic targets. For a detailed analysis, consult our article on the 10 cognitive distortions that sabotage your couple.

Mind reading

Definition: Believing one can guess what the other thinks or feels without verifying, and acting accordingly. Example: "My partner didn't text me this morning, so they're angry with me."

Personalization

Definition: Attributing to oneself the responsibility for negative events that do not depend on oneself. Example: "If they're in a bad mood, it must be because of something I did."

Labeling

Definition: Reducing a person to an overall and fixed label based on an isolated behavior. Example: "He forgot our anniversary, he's a selfish person" (instead of "he forgot this date").

Mental filter

Definition: Retaining only a single negative detail of a situation, thus filtering all reality through this single element. Example: After an evening where your partner was attentive for four hours, you only retain the five-second clumsy remark.

All-or-nothing thinking

Definition: Seeing situations in absolute categories, without intermediate nuances. Example: "If our couple is not perfect, then it's worth nothing."

Catastrophizing

Definition: Imagining the worst possible scenario and considering it the most likely. Example: "They're not answering the phone. They've had an accident. They're dead." (when they are in a meeting).

Overgeneralization

Definition: Drawing a general and definitive conclusion from a single event. Example: "You never put anything away" (after a single oversight).

Disqualifying the positive

Definition: Actively rejecting positive experiences by declaring them invalid. Example: "He gave me flowers, but it's surely because he feels guilty about something."

Emotional reasoning in relationships

Definition: Using one's emotions as the only proof of relational reality. Central distortion identified by Beck. Example: "I don't feel loved, therefore my partner doesn't love me." The feeling is real, but the interpretation is a deduction without proof.

Should statements

Definition: Imposing rigid rules on oneself or the other with "he/she should". Example: "A good partner should always know what I feel without me having to say it."

Arbitrary inference

Definition: Drawing a conclusion without sufficient evidence or despite contrary evidence. Example: Concluding that your partner is cheating on you because they changed perfume.

Selective abstraction

Definition: Focusing on a detail out of context, ignoring the big picture. Example: Your partner prepares an elaborate dinner, but you only retain the fact that they forgot to add salt.

Minimization

Definition: Reducing the importance of one's own qualities or the positive aspects of a situation. Example: "Yes, we had a good weekend, but it's normal, we were on vacation."

Magnification

Definition: Exaggerating the importance of a defect, a problem, or a negative event. Example: A small dispute in the car is transformed into proof that "our couple is a disaster".

Relationship confirmation bias

Definition: Seeking evidence that confirms one's view of the relationship (positive or negative) while ignoring contrary evidence. Example: When you think your relationship is going badly, you interpret every silence as additional proof of detachment.

Relationship narrative bias

Definition: Constructing a coherent narrative of the relationship that simplifies reality and filters out contradictory events. Example: Telling the story of one's couple as a succession of difficulties, forgetting the many moments of happiness.

Relationship projection

Definition: Attributing to one's partner one's own thoughts, desires, or insecurities. Example: Accusing one's partner of wanting to flirt with other people because you yourself have unacknowledged temptations.

Upward comparison in relationships

Definition: Constantly comparing one's couple to an unattainable ideal (social networks, films, friend couples). Example: "If only our couple was as connected as our friends' on Instagram." (ignoring that social networks only show the facade).

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7. Economic and Commercial Biases

These biases exploited by marketing and finance show how our economic decisions systematically deviate from rationality.

Price anchoring

Definition: The first price seen for a product serves as a reference for judging all subsequent prices, even if arbitrary. Example: A suit displayed at 2,000 euros then sold at 800 euros seems a good deal, even if its real value is 500 euros.

Sunk cost fallacy

Definition: Continuing to invest in a project because of resources already committed, even when it is rational to stop. Example: Watching a boring film to the end because one has paid for the cinema ticket.

Mental accounting

Definition: Treating sums of money differently according to their origin or destination, when objectively a euro is a euro. Example: Easily spending a 500-euro bonus on pleasure purchases, when one would not dare touch one's savings for the same amount.

Zero-price effect

Definition: Free items exert a disproportionate attraction, pushing one to choose a free option rather than a superior option at a modest cost. Example: Preferring a mediocre free chocolate to a luxury chocolate at 0.15 euro, even though the quality difference is obvious.

Relative wealth bias

Definition: Evaluating one's wealth not in absolute terms but by comparison with one's entourage. Example: Feeling poor with a monthly salary of 4,000 euros when all one's friends earn 6,000 euros.

Scarcity effect

Definition: Giving more value to a product or opportunity when their availability is limited. Example: "Only 2 left in stock!" on an e-commerce site creates an artificial urgency that pushes one to impulse purchase.

Post-purchase rationalization

Definition: After a purchase, seeking reasons to convince oneself it was the right decision. Example: After buying an overpriced car, spending hours reading positive reviews to reassure oneself.

Veblen effect

Definition: The higher the price of a luxury good, the more demand increases, because high price is perceived as a sign of quality and status. Example: A handbag sold at 5,000 euros is more desirable than the same bag sold at 500 euros.

Fair price bias

Definition: Judging a price as "fair" or "unfair" based on subjective rather than economic criteria. Example: Judging it scandalous that a bottle of water costs 5 euros at the airport, even if logistics costs and rent justify it.

Denomination effect

Definition: People spend small denominations more easily than large ones, even for an identical total amount. Example: Easily spending ten 1-euro coins on pastries, but hesitating to break a 10-euro bill for the same purchase.

Extremeness aversion

Definition: Tendency to avoid extreme options (the most expensive and the cheapest) and choose the intermediate option. Example: In a restaurant, the majority of customers choose the wine at the median price, which allows the restaurateur to place their best margin on this option.

Commercial endowment effect

Definition: When a customer has touched or tried a product, they become attached to it and are more inclined to buy it. Example: Free 30-day trials exploit this bias: after a month of use, giving up the subscription is experienced as a loss.

Conditional free effect

Definition: The offer of a gift conditional on a minimum purchase pushes one to spend more than planned to reach the threshold. Example: "Free delivery starting at 50 euros" pushes one to add a useless item to go from 42 to 50 euros.

Psychological pricing bias

Definition: Prices ending in 9 or 99 are perceived as significantly inferior to the next round number. Example: 9.99 euros is perceived as "about 9 euros" and not "about 10 euros", although the difference is one cent.

Temporal endowment

Definition: Tendency to value more the time already invested in a queue or process, which pushes one to stay. Example: After 45 minutes of waiting on the phone for customer service, continuing to wait rather than hanging up and calling back later.

Gift bias

Definition: Overvaluing a received gift compared to its market value, which creates a sense of obligation. Example: A supplier offers a Christmas gift to a buyer, who then feels obligated to grant them a contract.

False economy bias

Definition: Making a choice that seems economical in the short term but costs more in the long term. Example: Buying cheap shoes that wear out in six months, rather than quality shoes that last five years.

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8. Logical Reasoning Biases

These biases affect our ability to reason logically and correctly evaluate cause-and-effect relationships.

Gambler's fallacy

Definition: Believing that a past random event influences future events, as if chance had a "memory". Example: After five reds on the roulette, betting on black thinking it is "due", when the probability remains 50/50.

Illusory correlation

Definition: Perceiving a relationship between two variables where none exists, often due to an attention bias. Example: Believing that the full moon causes more births or crimes, when no serious study confirms it.

Post hoc ergo propter hoc

Definition: Concluding that one event is the cause of another simply because it preceded it. Example: "I wore my lucky socks and I won the match. My socks brought me luck."

Slippery slope fallacy

Definition: Asserting without proof that an action will necessarily lead to a chain of negative consequences. Example: "If we allow self-driving cars, soon robots will control our whole lives."

False cause bias

Definition: Attributing an erroneous cause to an event due to temporal coincidence or apparent correlation. Example: Concluding that vaccines cause autism because the diagnosis of autism is often made at the age of vaccination.

Appeal to authority

Definition: Accepting an argument as true because it is put forward by an authority, even if this authority is not competent in the field concerned. Example: A famous actor recommends a dietary supplement in an advertisement, and sales explode.

Argument to moderation

Definition: Believing that truth necessarily lies halfway between two opposing positions. Example: "Scientists say the Earth is round, conspiracy theorists say it's flat. The truth is probably between the two."

Burden of proof reversal

Definition: Demanding that the opponent prove the non-existence of something, rather than proving its existence. Example: "Prove to me that ghosts do not exist!" (the burden of proof falls on the one who claims existence).

Naturalistic fallacy

Definition: Concluding that something is good or desirable because it is natural, and bad because it is artificial. Example: Refusing an effective synthetic medication in favor of a "natural" remedy with no proof of effectiveness.

Genetic fallacy

Definition: Judging the value of an argument based on its origin rather than its content. Example: Rejecting a relevant idea because it comes from someone you do not like.

Texas sharpshooter fallacy

Definition: Selecting data that confirms a pattern after the fact, ignoring data that does not confirm it. Example: A psychic who makes 100 predictions only retains the 5 that came true to prove their "powers".

Straw man fallacy

Definition: Distorting the opponent's argument to make it easier to attack. Example: "You want to reduce the military budget? So you want our country to be invaded!"

Opportunity cost neglect

Definition: Not considering what one gives up by choosing one option rather than another. Example: Spending three hours saving 20 euros on a purchase without realizing that those three hours could have brought in 100 euros of work.

Composition fallacy

Definition: Concluding that what is true for the parts is necessarily true for the whole. Example: "Each brick is light, so the wall must be light."

Division fallacy

Definition: Concluding that what is true for the whole is necessarily true for each part. Example: "This team is excellent, so each player is excellent."

False dilemma

Definition: Presenting a situation as having only two possible options, when others exist. Example: "Either you are with us, or you are against us."

Regression to the mean misconception

Definition: Not understanding that extreme performances naturally tend to normalize, and attributing this normalization to a specific cause. Example: A coach who punishes their players after a bad match and congratulates them after a good match believes that punishment works, when performances would have fluctuated anyway.

Nirvana fallacy

Definition: Rejecting an imperfect solution under the pretext that it is not perfect, without proposing a feasible alternative. Example: "This vaccine only protects at 95%, so it is useless." (ignoring that no solution reaches 100%).

Appeal to tradition

Definition: Justifying a practice by the fact that it is old, without evaluating its current relevance. Example: "We have always done it this way in our family/company" as the only justification.

Appeal to novelty

Definition: Believing that something is better simply because it is new or recent. Example: Replacing a perfectly functioning software with the latest version, which is full of bugs.

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Summary table of cognitive biases

| Bias | Category | Short definition |
|------|----------|------------------|
| Confirmation | Judgment | Seeking what confirms our beliefs |
| Anchoring | Judgment | Excessive weight of the first information |
| Halo | Judgment | A positive trait colors all judgment |
| Availability | Judgment | Overestimating what comes easily to mind |
| Representativeness | Judgment | Judging by resemblance, not probability |
| Illusion of control | Judgment | Believing one influences chance |
| Optimism | Judgment | Overestimating positive chances |
| Status quo | Judgment | Preferring not to change |
| Endowment | Judgment | Overvaluing what one owns |
| Loss aversion | Judgment | Losing hurts more than winning |
| Survivorship | Judgment | Only seeing those who succeeded |
| Hindsight | Judgment | Believing one knew from the start |
| Dunning-Kruger | Judgment | Incompetent and confident |
| Overconfidence | Judgment | Too confident in one's judgments |
| Framing | Judgment | Presentation changes the decision |
| Recency | Memory | Better remembering the last elements |
| Primacy | Memory | Better remembering the first elements |
| False memories | Memory | Remembering what did not happen |
| Google effect | Memory | Remembering less what is searchable |
| Cryptomnesia | Memory | Believing an old idea is new |
| Zeigarnik | Memory | Better remembering unfinished tasks |
| Conformity | Social | Aligning with the group |
| Fundamental attribution | Social | Explaining others by their character |
| Bystander | Social | More witnesses = less help |
| Groupthink | Social | Consensus at the expense of reason |
| Ingroup favoritism | Social | Favoring one's own group |
| Pygmalion | Social | Positive expectations improve performance |
| Authority | Social | Believing authority figures |
| Negativity | Attention | The negative captures more attention |
| Salience | Attention | What strikes is overvalued |
| Baader-Meinhof | Attention | Seeing everywhere what one just learned |
| Inattentional blindness | Attention | Not seeing what one is not looking for |
| Emotional reasoning | Emotion | Emotion = reality |
| Affect | Emotion | Deciding with emotions |
| Cold-hot empathy | Emotion | Not predicting one's future emotions |
| Immediate gratification | Emotion | Preferring immediate pleasure |
| Mind reading | Couple | Believing one guesses the partner's thoughts |
| Personalization | Couple | Relating everything to oneself |
| Labeling | Couple | Reducing the other to a defect |
| Catastrophizing | Couple | Imagining the worst scenario |
| All-or-nothing | Couple | Seeing without nuances |
| Price anchoring | Economic | The first price serves as reference |
| Sunk cost | Economic | Continuing because one has already invested |
| Mental accounting | Economic | Treating money differently based on source |
| Scarcity | Economic | Rare = precious |
| Gambler's fallacy | Logic | Chance has a memory |
| Illusory correlation | Logic | Seeing links that do not exist |
| Post hoc | Logic | Before = cause |
| Straw man | Logic | Distorting the opponent's argument |
| False dilemma | Logic | Only two options |

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Beck's 15 cognitive distortions: the CBT grid

Aaron T. Beck, founder of cognitive therapy, identified a set of cognitive distortions that constitute the foundation of CBT. These distortions are distinguished from "classical" cognitive biases by their clinical dimension: they are directly linked to psychological suffering and constitute therapeutic targets. For an in-depth analysis, consult our article on cognitive distortions.

| # | Distortion | Definition | Example |
|---|-----------|------------|---------|
| 1 | All-or-nothing thinking | Seeing in black or white, without nuances | "If it's not perfect, it's a total failure" |
| 2 | Overgeneralization | Drawing a universal rule from a single event | "I always mess up everything" |
| 3 | Mental filter | Focusing exclusively on the negative | 9 compliments forgotten, 1 criticism retained |
| 4 | Disqualifying the positive | Actively rejecting positive experiences | "He says that out of politeness" |
| 5 | Jumping to conclusions | Concluding without proof (mind reading + negative anticipation) | "He didn't call me back, so he doesn't care" |
| 6 | Magnification / Minimization | Exaggerating the negative, minimizing the positive | Catastrophizing a flaw, ignoring a quality |
| 7 | Emotional reasoning | Taking one's emotions for reality | "I feel worthless, so I am worthless" |
| 8 | Should statements | Imposing rigid rules (I should, I must) | "I should be able to handle everything alone" |
| 9 | Labeling | Reducing oneself or the other to a global label | "I am a loser" / "He is selfish" |
| 10 | Personalization | Attributing to oneself the responsibility for external events | "If he's sad, it's my fault" |
| 11 | Selective abstraction | Isolating a detail out of context | Retaining only one error in a successful project |
| 12 | Arbitrary inference | Concluding without sufficient proof | "She didn't smile at me, she hates me" |
| 13 | Catastrophizing | Anticipating the worst scenario as certain | "If I fail this exam, my life is over" |
| 14 | Unfair comparison | Comparing oneself to the highest performers, ignoring context | "She got a promotion, never me" |
| 15 | Dichotomous reasoning | Thinking in terms of extreme categories | "Either he loves me 100%, or he doesn't love me" |

Cognitive restructuring, the central technique of CBT, consists of identifying these distortions in automatic thoughts, naming them, then replacing them with more balanced alternative thoughts. This process does not aim at forced optimism, but at a more realistic and nuanced perception of reality.

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FAQ: Frequently asked questions about cognitive biases

What is the difference between a cognitive bias and a cognitive distortion?

A cognitive bias is a universal and automatic mechanism for processing information, identified by cognitive psychology (Kahneman, Tversky). It affects everyone, even experts. A cognitive distortion is a clinical concept developed by Aaron T. Beck within the framework of CBT. It designates a dysfunctional thought pattern that contributes to psychological suffering. The two concepts partially overlap (the confirmation bias and the mental filter describe similar phenomena), but the approach is different: the bias is descriptive (how the brain works), the distortion is clinical (how thinking generates suffering).

Can we eliminate our cognitive biases?

No. Cognitive biases are an integral part of brain functioning and have adaptive value (they allow quick decisions to be made). The goal is not to eliminate them but to recognize them to better compensate for them. CBT techniques, the practice of methodical doubt, and critical thinking training help reduce their impact on our important decisions.

Which are the most dangerous cognitive biases in daily life?

The confirmation bias (which locks us into our beliefs), loss aversion (which prevents us from taking rational risks), anchoring bias (which distorts our estimates), and emotional reasoning (which confuses emotion and reality) are among the most impactful. In couples, mind reading and catastrophizing are the most destructive.

Are cognitive biases stronger in some people?

Everyone is subject to cognitive biases, but certain factors increase their intensity: fatigue, stress, cognitive overload, anxiety, and depression. People suffering from anxiety or depressive disorders present more frequent and intense cognitive distortions. Paradoxically, intelligence does not protect against biases: very intelligent people are sometimes more skilled at rationalizing their biases, making them more difficult to detect.

How does CBT use cognitive biases in therapy?

CBT identifies the cognitive distortions present in the patient's automatic thoughts using a thought table (situation, emotion, automatic thought, identified distortion, alternative thought). This cognitive restructuring process does not aim to think positively, but to think more realistically and with nuance. In couples, CBT helps partners identify their respective biases (mind reading, labeling, catastrophizing) to communicate about facts rather than interpretations.

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Toward more lucid thinking

Listing 250 cognitive biases can be dizzying: if our brain is so unreliable, how to make good decisions? The answer holds in three principles.

First, knowing one's biases is already a considerable advantage. The majority of judgment errors occur in the shadows, without our being aware of them. The simple fact of being able to name a bias — "this is my confirmation bias talking" — is often enough to reduce its impact. Second, certain situations increase vulnerability to biases: fatigue, stress, time pressure, strong emotions. In these moments, slowing down and deferring important decisions is an effective strategy. Third, cognitive-behavioral therapy offers a structured framework to work on the most pervasive distortions, particularly those affecting couple relationships and psychological well-being.

If you wish to explore your own thought patterns with a professional, do not hesitate to make an appointment for a consultation. Awareness of one's biases is not a sign of weakness: it is the first step toward freer thinking.