250 Cognitive Biases: The Complete List with Definitions

TL;DR: Cognitive biases are systematic mental shortcuts that distort our judgment, memory, and decisions. Identified through the foundational work of Daniel Kahneman, Amos Tversky, and Aaron T. Beck, these biases affect every human being without exception. This article catalogs over 250 cognitive biases across eight categories: judgment and decision-making, memory, social biases, attention and perception, emotions, romantic relationships, economics, and logical reasoning. Each bias includes a precise definition and a concrete example. Understanding these mechanisms is the first step toward clearer thinking and healthier relationships.

Our brain processes around 11 million bits of information per second, but our consciousness only handles 50. To bridge this dizzying 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, psychiatrist Aaron T. Beck identified cognitive distortions within cognitive behavioral therapy (CBT), showing how these automatic thought patterns fuel anxiety, depression, and relational conflict.

Today, research has cataloged more than 250 distinct cognitive biases. This article lists them exhaustively, organized by category, each with a clear definition and a concrete example. The goal is not to eliminate these biases -- that is impossible -- but to recognize them in order to outwit them more effectively.

---

1. Judgment and Decision-Making Biases

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

Confirmation bias (Confirmation bias)

Definition: The tendency to selectively search for, 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 each of their mistakes but retain none of their successes.

Anchoring bias (Anchoring bias)

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

Halo effect (Halo effect)

Definition: The 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 (Availability bias)

Definition: The tendency to overestimate the probability of an event based on how easily examples come to mind. Example: After watching a report on a plane crash, you considerably overestimate the risk of flying, even though statistics show it is the safest form of transport.

Representativeness bias (Representativeness bias)

Definition: The tendency to judge the probability of an event based on its resemblance to a mental prototype, while ignoring base rates. Example: Learning that Marc is calm and loves books leads you to classify him as a librarian rather than a salesperson, even though salespeople are statistically far more numerous.

Illusion of control (Illusion of control)

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

Optimism bias (Optimism bias)

Definition: The tendency to overestimate the probability of positive events and underestimate that of negative events affecting us. Example: Most smokers believe that lung cancer will strike others, not them.

Status quo bias (Status quo bias)

Definition: An irrational preference for the current state of affairs, even when a change would be objectively beneficial. Example: You stay with your phone provider for ten years despite far better offers from competitors, simply because switching requires effort.

Endowment effect (Endowment effect)

Definition: The tendency to assign a higher value to an object simply because you own it. Example: You refuse to sell your old bike for 100 euros even though you no longer use it and would not buy it at that price.

Loss aversion (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 far greater distress than the joy of finding 50 euros.

Survivorship bias (Survivorship bias)

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

Hindsight bias (Hindsight bias)

Definition: The 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 you knew it was going to happen.

Dunning-Kruger effect (Dunning-Kruger effect)

Definition: People with low competence in a field overestimate their abilities, while experts underestimate theirs. Example: A novice driver considers themselves an excellent driver, while a professional driver constantly doubts their performance.

Overconfidence bias (Overconfidence bias)

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

Framing effect (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 (Contrast effect)

Definition: Our evaluation of an item is altered by comparison with a preceding item. Example: An average job interview candidate appears excellent if they go right after a mediocre candidate.

Omission bias (Omission bias)

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

Normalcy bias (Normalcy bias)

Definition: The 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 that it will not be as severe as announced.

Impact bias (Impact bias)

Definition: The tendency to overestimate the intensity and duration of our future emotional reactions, both positive and negative. Example: You think a breakup will destroy you for years, when in reality you adapt within a few months.

Projection bias (Projection bias)

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

Decoy effect (Decoy effect)

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

Distinction bias (Distinction bias)

Definition: The tendency to perceive two options as more different when evaluating them simultaneously than separately. Example: In a store, two televisions side by side seem very different in image quality. At home, you would notice no difference.

Ambiguity aversion (Ambiguity aversion)

Definition: A preference for options with known probabilities, even if unfavorable, over options with unknown probabilities. Example: Preferring a guaranteed 2% bank deposit over an investment that yields 8% on average but with uncertainty.

Outcome bias (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, regardless of the soundness of their reasoning.

False consensus effect (False consensus effect)

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

Ostrich effect (Ostrich effect)

Definition: The tendency to deliberately ignore negative or threatening information. Example: Never checking your bank statements when you know you are spending too much.

Choice-supportive bias (Choice-supportive bias)

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

IKEA effect (IKEA effect)

Definition: The tendency to assign a disproportionate value to things you have created or assembled yourself. Example: You are prouder of your wobbly hand-assembled shelf than of a designer piece of furniture bought in a store.

Bias blind spot (Bias blind spot)

Definition: The ability to spot cognitive biases in others while being unable to recognize one's own. Example: You clearly identify confirmation bias in your conspiracy-minded friend, but fail to see the one guiding your own reading of the news.

Bandwagon effect (Bandwagon effect)

Definition: The tendency to adopt a belief or behavior because many other people do. Example: Buying a cryptocurrency solely because everyone is talking about it, without understanding the underlying technology.

Planning fallacy (Planning fallacy)

Definition: The 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 months and cost 25,000 euros.

Illusory truth effect (Illusory truth effect)

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

Just-world hypothesis (Just-world hypothesis)

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

---

2. Memory Biases

Recency effect (Recency effect)

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

Primacy effect (Primacy effect)

Definition: The tendency to better remember the first items in 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.

False memory (False memory)

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

Google effect (Google effect)

Definition: The tendency to remember less well information that you know you can easily find online. Example: Being unable to remember an actor's name because you know you can look it up online in three seconds.

Cryptomnesia (Cryptomnesia)

Definition: Mistaking for an original idea something you actually heard or read before. Example: Proposing an innovative solution in a meeting, when a colleague had put forward exactly the same idea three months earlier.

Zeigarnik effect (Zeigarnik effect)

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

Rosy retrospection (Rosy retrospection)

Definition: The tendency to remember past events more positively than they were actually experienced. Example: Remembering your childhood holidays as perfect, while forgetting the rain, the arguments, and the boredom.

Egocentric bias (Egocentric bias)

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

---

3. Social Biases

Fundamental attribution error (Fundamental attribution error)

Definition: The tendency to explain others' behavior by their personality rather than by circumstances. Example: Thinking that a driver who cuts you off is a reckless road hog, while when you do it, it is because you were running late.

Pygmalion effect (Pygmalion effect)

Definition: The positive expectations of a person in authority toward another actually improve the latter's performance. Example: Students presented as "promising" to their teacher progress more, even though this label was assigned at random.

Self-serving bias (Self-serving bias)

Definition: The tendency to attribute one's successes to internal causes and one's failures to external causes. Example: Passing an exam thanks to one's intelligence, but failing because of an unfair teacher.

Authority bias (Authority bias)

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

Barnum effect (Barnum effect)

Definition: The tendency to accept vague and general descriptions as perfectly suited to one's own personality. Example: Finding your horoscope astonishingly accurate, even though the same description applies to almost everyone.

Group polarization (Group polarization)

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

---

4. Attention and Perception Biases

Negativity bias (Negativity bias)

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

Frequency illusion (Baader-Meinhof phenomenon)

Definition: After noticing something for the first time, you have the impression of seeing it everywhere. Example: After learning a new word, you feel like you read it in every article.

Pareidolia (Pareidolia)

Definition: The 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.

---

5. Emotional Biases

Emotional reasoning (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."

Affect heuristic (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 you like it and dangerous when you dislike it.

Present bias (Present bias)

Definition: An excessive preference for immediate rewards at the expense of larger future rewards. Example: Choosing to watch a series tonight rather than studying for an exam next week.

---

6. Cognitive Biases in Relationships

Mind reading (Mind reading)

Definition: Believing you can guess what the other person thinks or feels without checking. Example: "My partner didn't text me this morning, so they're angry with me."

Catastrophizing (Catastrophizing)

Definition: Imagining the worst possible scenario and considering it the most likely. Example: "He's not answering the phone. He's had an accident."

Labeling (Labeling)

Definition: Reducing a person to a global, fixed label based on an isolated behavior. Example: "He forgot our anniversary, he's selfish."

---

7. Economic and Commercial Biases

Sunk cost fallacy (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 you paid for the cinema ticket.

Mental accounting (Mental accounting)

Definition: Treating sums of money differently depending on their origin or destination. Example: Easily spending a 500-euro bonus on pleasure purchases, while not daring to touch your savings.

Scarcity effect (Scarcity effect)

Definition: Assigning more value to a product when its availability is limited. Example: "Only 2 left in stock!" creates an artificial urgency that drives impulse buying.

---

8. Logical Reasoning Biases

Gambler's fallacy (Gambler's fallacy)

Definition: Believing that a past random event influences future events. Example: After five reds at the roulette table, betting on black thinking it is "due".

Illusory correlation (Illusory correlation)

Definition: Perceiving a relationship between two variables where none exists. Example: Believing that the full moon causes more births or crimes.

Post hoc ergo propter hoc (Post hoc fallacy)

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."

False dilemma (False dilemma)

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

---

Beck's 15 Cognitive Distortions

---

Take the Psy Test → — 50 questions, anonymous, PDF report (€1.99). 🔗 Analyze your conversations with ScanMyLove — get an objective, structured read of your relationship's communication patterns.

FAQ

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

A cognitive bias is a universal, automatic information-processing mechanism identified by cognitive psychology (Kahneman, Tversky). A cognitive distortion is a clinical concept developed by Aaron T. Beck within CBT. It designates a dysfunctional thought pattern contributing to psychological suffering. The two concepts partially overlap, but the approach differs: biases are descriptive (how the brain works), distortions are clinical (how thinking generates suffering).

Can cognitive biases be eliminated?

No. Cognitive biases are an integral part of brain function and have adaptive value. The goal is not elimination but recognition and compensation. CBT techniques, methodical doubt, and critical thinking training help reduce their impact on important decisions.

Which cognitive biases are most dangerous in daily life?

Confirmation bias (locks us in beliefs), loss aversion (prevents rational risk-taking), anchoring bias (distorts estimates), and emotional reasoning (confuses emotion with reality) are among the most impactful. In relationships, 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. Paradoxically, intelligence does not protect against biases -- highly intelligent people are sometimes more skilled at rationalizing their biases.

How does CBT use cognitive biases in therapy?

CBT identifies cognitive distortions in the patient's automatic thoughts using a thought record (situation, emotion, automatic thought, identified distortion, alternative thought). This cognitive restructuring process does not aim at forced optimism but at a more realistic and nuanced perception of reality.