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 founding work of Daniel Kahneman, Amos Tversky, and Aaron T. Beck, these biases affect every individual without exception. This article catalogs over 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 about 11 million bits of information per second, but our consciousness handles only 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 the framework of cognitive behavioral therapy (CBT), showing how these automatic thought patterns fuel anxiety, depression, and relational conflicts.

Today, research has cataloged over 250 distinct cognitive biases. This article catalogs them exhaustively, organized by category, with a clear definition and concrete example for each. The goal is not to eliminate these biases — it's impossible — but to recognize them to better counter them.

---

1. Judgment and decision 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

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

Anchoring bias

Definition: Tendency to place excessive weight on the first piece of 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, while the item is worth 200.

Halo effect

Definition: Tendency to extend the global impression of a person (positive or negative) to specific evaluations of their traits. Example: A physically attractive candidate is judged more competent during a job interview.

Availability heuristic

Definition: Tendency to overestimate the probability of events that easily come to mind, often because they are recent, emotionally striking, or media-prominent. Example: After watching a documentary on plane crashes, you judge air travel more dangerous than driving, despite contrary statistics.

Representativeness bias

Definition: Tendency to judge the probability of an event based on its similarity to a stereotype, rather than on actual statistics. Example: Linda described as a 31-year-old, single, brilliant philosophy graduate, and active in feminist causes is more likely to be judged a "feminist bank teller" than simply a "bank teller" — yet statistically impossible.

Sunk cost fallacy

Definition: Tendency to continue investing in a project or relationship because of already invested resources, even when the rational decision would be to stop. Example: Staying in a toxic relationship for 10 years because "I've invested too much time."

Overconfidence bias

Definition: Systematic overestimation of one's own knowledge, skills, or chances of success. Example: 80% of drivers consider themselves above average — mathematically impossible.

Dunning-Kruger effect

Definition: Incompetent people tend to overestimate their abilities, while competent people tend to underestimate them. Example: A novice in a domain expresses strong opinions with absolute certainty, while a recognized expert nuances their statements.

Optimism bias

Definition: Tendency to overestimate the probability of positive events and underestimate negative ones for oneself. Example: Smokers who underestimate their personal risk of developing cancer, while accurately estimating the average risk.

Pessimism bias

Definition: Opposite tendency, particularly present in depression, to overestimate the probability of negative events. Example: A depressed person convinced that any project they undertake will fail.

Loss aversion

Definition: Psychological pain associated with a loss is approximately twice as strong as the pleasure of an equivalent gain. Example: Losing 100 euros generates more distress than finding 100 euros generates joy.

Framing effect

Definition: The way information is presented influences the decision, even when the objective content is identical. Example: "90% chance of survival" vs. "10% chance of death" generates radically different decisions while being statistically identical.

Hindsight bias

Definition: Tendency, after the fact, to consider an event predictable, while it was not. Example: "I knew the company was going to fail" — said after the bankruptcy, while no signal was identified before.

Status quo bias

Definition: Preference for maintaining the current state, even when change would be objectively beneficial. Example: Keeping a bank with high fees out of inertia, despite cheaper offers.

Decision fatigue

Definition: Decision-making quality degrades with the number of decisions taken in a row. Example: Judges grant more favorable verdicts in the morning than in the late afternoon.

Many other judgment biases include: bandwagon effect, false consensus effect, IKEA effect, endowment effect, illusion of control, gambler's fallacy, base rate neglect, conjunction fallacy, planning fallacy, mere exposure effect, ostrich effect, default effect, choice paradox, attention bias, denomination effect, contrast effect, primacy effect, recency effect, peak-end rule.

---

2. Memory biases

Memory is not a faithful recording: it actively reconstructs the past. These biases distort the way we remember events.

Reconstruction bias

Definition: Each memory recall modifies the original memory, integrating elements of the current context. Example: A relived childhood memory at age 40 is not identical to that same memory recalled at age 20.

False memories

Definition: Memories of events that never occurred, often induced by suggestion or imagination. Example: The Loftus and Pickrell experiment (1995) succeeded in making 25% of adults "remember" being lost in a mall in childhood, a fictional event.

Misattribution effect

Definition: Confusion between the source of a memory and the memory itself. Example: Believing you have a personal memory while in reality it's the story of a film or someone else.

Tip-of-the-tongue phenomenon

Definition: Sensation of having a memory accessible without managing to retrieve it explicitly. Example: Knowing the name of an actor "right on the tip of the tongue" without managing to articulate it.

Mood-congruent memory bias

Definition: Memory facilitated for events whose emotional valence matches the current mood. Example: During a depressive episode, easier access to negative memories of life.

Generation effect

Definition: Information produced oneself is better memorized than information passively read. Example: Trying to find an answer before reading it considerably improves long-term retention.

Other memory biases include: serial position effect, picture superiority effect, Google effect, levels of processing effect, von Restorff effect, repressed memory, Zeigarnik effect, age-related telescoping bias, rosy retrospection, fading affect bias.

---

3. Social biases

These biases affect how we perceive and interact with others.

Fundamental attribution error

Definition: Tendency to attribute others' behaviors to their personality, while attributing our own to the situation. Example: "He didn't say hello to me, he's contemptuous" (whereas if it were us, we would say "I was distracted").

Self-serving bias

Definition: Attributing our successes to our merits and our failures to external factors. Example: "I got the promotion thanks to my competence, but I failed the exam because the questions were unfair."

In-group bias

Definition: Tendency to favorably evaluate members of one's group and unfavorably those of out-groups. Example: Considering one's own political party more reasonable than the others.

Out-group homogeneity bias

Definition: Perception that members of an out-group are more similar to each other than members of one's own group. Example: "They all think alike" (said of an external group), while recognizing diversity within one's own group.

Conformity bias (Asch)

Definition: Tendency to align one's opinions with those of the majority, even against one's own perception. Example: Asch's experiment (1951): 75% of subjects publicly gave an obviously wrong answer to conform to the group.

Stereotype threat

Definition: Performance decline when an individual fears confirming a negative stereotype about their group. Example: Women score lower on math tests when their gender is highlighted before the test.

Other social biases include: false consensus effect, false uniqueness effect, observer effect, defensive attribution bias, ultimate attribution error, bystander effect, social loafing, social facilitation, group polarization, groupthink, naive realism, projection bias, third-person effect.

---

4. Attention and perception biases

How we capture and interpret sensory information is biased from the source.

Attentional blindness

Definition: Inability to perceive a visible stimulus when attention is focused elsewhere. Example: The famous gorilla experiment (Simons and Chabris, 1999): 50% of subjects counting basketball passes do not see a gorilla walking through the scene.

Change blindness

Definition: Inability to detect significant changes in a visual scene. Example: A person in a conversation does not realize their interlocutor has been replaced after a brief visual interruption.

Pareidolia

Definition: Tendency to perceive familiar shapes (faces, objects) in random stimuli. Example: Seeing a face in cloud formations or in a stain on the wall.

Negativity bias

Definition: Negative information captures more attention and has more impact than positive information of equivalent intensity. Example: A single negative criticism takes more space in mind than ten positive compliments.

Other attention biases include: top-down attention bias, attention bias to threat, dichotic listening, selective inattention, attention capture, blind spot, illusion of focus.

---

5. Emotional biases

Emotions influence reasoning in systematic and predictable ways.

Affect heuristic

Definition: Using one's emotional state to make judgments unrelated to the situation. Example: Being in a good mood leads to overestimating the probability of positive events of all kinds.

Halo of love

Definition: Tendency to idealize the love partner in the initial phase of the relationship. Example: Perceiving a partner's anger management problems as "passion" rather than warning signals.

Anger blindness

Definition: Anger reduces the ability to consider alternative perspectives. Example: During a couple's argument, becoming incapable of imagining that the partner has legitimate reasons.

Other emotional biases include: emotional reasoning, hot-cold empathy gap, affective forecasting bias, impact bias, durability bias, emotional contagion, mood maintenance.

---

6. Cognitive biases in couple and relationships

These biases specifically affect intimate dynamics and are at the heart of CBT couple therapy.

Selective attention to partner's flaws

Definition: After the initial phase of love, tendency to disproportionately notice the partner's negative behaviors. Example: Noticing every time the partner forgets to take out the trash, but not the times they prepared meals.

Negative intention attribution

Definition: Tendency to interpret the partner's ambiguous behaviors negatively. Example: "She didn't respond to my message immediately, she's punishing me" (whereas she was simply busy).

Catastrophization in conflict

Definition: Interpreting a couple's argument as an absolute threat to the relationship. Example: "If we argue today, it means our relationship is doomed."

Rosy retrospection of past relationships

Definition: Idealizing past relationships compared to the current one. Example: "With my ex, it was simpler" — selectively forgetting the conflicts that ended the previous relationship.

Familiarity bias in partner choice

Definition: Tendency to unconsciously choose partners reproducing childhood relational patterns, even dysfunctional ones. Example: Repeatedly attracted to emotionally unavailable people, reproducing the absent-parent dynamic.

Other couple biases include: reactance, polarization, projection in couple, demand-withdraw pattern, mind reading in couple, comparative bias of social networks, confirmation bias in relationship.

---

7. Economic and commercial biases

These biases are systematically exploited by marketing and financial industries.

Endowment effect

Definition: Tendency to value an object more once we possess it. Example: Owners ask 50% more for an item than buyers offer for the same item.

Decoy effect

Definition: Adding a deliberately unattractive option that makes another option appear more advantageous. Example: A magazine offers digital subscription at €60, paper at €100, and digital+paper at €100. The intermediate option exists only to make the third more attractive.

Compromise effect

Definition: Tendency to choose the middle option among three. Example: Three menus at €15, €25, and €40 — most customers choose the €25 menu.

Scarcity effect

Definition: A scarce object is valued more highly. Example: "Only 3 in stock!" significantly increases purchase desire.

Default effect

Definition: People keep the default option proposed. Example: Countries with default organ donation see donation rates of 90%, against 15% in countries with active opt-in.

Other economic biases include: money illusion, denomination effect, expense aversion, identifiable victim effect, Veblen effect (snob), bandwagon effect, present bias, hyperbolic discounting, sunk cost fallacy.

---

8. Logical reasoning biases

These biases affect formal reasoning and logical deduction.

Affirmation of the consequent fallacy

Definition: Erroneously deducing the cause from the effect. Example: "If it rains, the streets are wet. The streets are wet, therefore it rained." (The streets may be wet for other reasons.)

Denial of the antecedent fallacy

Definition: Erroneously deducing the absence of the effect from the absence of the cause. Example: "If you study, you'll succeed. You didn't study. Therefore, you'll fail." (Other ways to succeed exist.)

Hasty generalization

Definition: Drawing a general conclusion from too few examples. Example: "I met two rude New Yorkers, so all New Yorkers are rude."

False dichotomy fallacy

Definition: Presenting only two options when other alternatives exist. Example: "You're either with us or against us" — ignoring positions of neutrality or nuance.

Other logical biases include: post hoc fallacy (causation/correlation), straw man fallacy, ad hominem, appeal to authority, appeal to tradition, appeal to nature, appeal to common knowledge, slippery slope argument, circular reasoning, semantic confusion, statistical bias, regression to the mean ignorance.

---

How CBT addresses these biases

Cognitive behavioral therapy does not seek to eliminate biases — they are fundamentally inherent in human cognition. The approach is to:

Identify them in real time, through observing one's automatic thoughts

Question them by examining evidence for and against

Develop alternative thoughts more balanced and realistic

Test them through behavioral experiences

The complete protocol is detailed in our article on cognitive distortions.

Daily exercise: the bias detection journal

For a week, note each evening:

A situation that generated intense emotion

The automatic thought that arose

Which biases were potentially at play

What an objective observer would have thought

This exercise, repeated, gradually develops your bias-detection capacity in real time.

---

Gildas Garrec, CBT psychopractitioner — Book an appointment to develop your cognitive lucidity in therapy.

FAQ

Are cognitive biases the same as logical fallacies?

Not exactly. Cognitive biases are systematic patterns of mental shortcuts that operate unconsciously. Logical fallacies are explicit reasoning errors that can be identified by formal logic. Cognitive biases often produce logical fallacies, but they originate from cognitive processing, not from formal argumentation.

Can we eliminate our cognitive biases?

No, but we can recognize them. Cognitive biases are inherent in how the human brain works — they cannot be eliminated. However, awareness, regular practice (such as bias detection journaling), and CBT can considerably reduce their negative impact on our decisions and relationships.

Which biases are most harmful in couples?

The most damaging are negative intention attribution, selective attention to flaws, catastrophization in conflict, and familiarity bias in partner choice. These four biases sustain destructive cycles and explain why some couples repeat the same disputes for years. CBT couple therapy specifically targets these patterns.