Psychology & Behavior

Availability Heuristic

Kahneman & Tversky

We judge the likelihood of events based on how easily examples come to mind, not on actual frequency. Dramatic, recent, or emotionally vivid events get massively overweighted.

Anchoring

Kahneman & Tversky

First information encountered disproportionately shapes all subsequent judgements.

Bandwagon Effect

People adopt trends because others have — popularity self-reinforces.

Bystander Effect

John Darley / Bibb Latané

More witnesses means less action — responsibility diffuses across groups.

Cognitive Dissonance

Leon Festinger

Contradictions between beliefs and actions drive rationalisation over change.

Confirmation Bias

We seek evidence that confirms what we already believe and filter out what contradicts it.

Curse of Knowledge

Colin Camerer / George Loewenstein / Martin Weber

Knowing something makes it impossible to imagine not knowing it.

Decision Fatigue

Shai Danziger / Roy Baumeister

Decision quality deteriorates after sustained choices — willpower is finite.

Dunning-Kruger Effect

David Dunning & Justin Kruger

Low competence breeds overconfidence; expertise breeds doubt.

Endowment Effect

Thaler / Kahneman / Knetsch

Ownership inflates perceived worth beyond objective value.

Framing Effect

Tversky & Kahneman

How you frame the question determines the answer you get.

Fundamental Attribution Error

Lee Ross

We blame character when circumstances are the real cause.

Groupthink

Irving Janis

Cohesive groups suppress dissent and converge on flawed decisions.

Halo Effect

Edward Thorndike

One positive trait colours evaluation of everything else.

Hindsight Bias

Baruch Fischhoff

After the fact, people believe they knew it all along.

IKEA Effect

Michael Norton / Daniel Mochon / Dan Ariely

Labour invested inflates perceived worth regardless of quality.

Incentive-Caused Bias

Charlie Munger

Show me the incentive and I will show you the outcome.

Lollapalooza

Charlie Munger

Multiple biases combining in the same direction produce extreme outcomes.

Loss Aversion

Kahneman & Tversky

Losses hurt roughly twice as much as equivalent gains feel good.

Narrative Fallacy

Nassim Nicholas Taleb

We compress complex reality into clean stories, mistaking explanation for prediction.

Peak-End Rule

Kahneman / Redelmeier / Katz

Experiences are judged by their peak moment and their ending.

Planning Fallacy

Kahneman / Tversky

People systematically underestimate time, cost, and risk of projects.

Self-Fulfilling Prophecies

Robert K. Merton

Beliefs alter behaviour in ways that make the belief come true.

Social Proof

Robert Cialdini

When uncertain, people copy what others are doing.

Status Quo Bias

William Samuelson / Richard Zeckhauser

Loss aversion applied to change makes inaction the default choice.

Sunk Cost Fallacy

Alfred Marshall

Past investments should not drive future decisions.

Survivorship Bias

Abraham Wald

Studying only survivors produces systematically wrong conclusions.

Attention Residue

Sophie Leroy / Cal Newport

In 2009, Sophie Leroy at the University of Minnesota published a paper that should have restructured every calendar in every knowledge-work organisation on the planet. The...

Availability Cascade

Timur Kuran / Cass Sunstein

In 1999, Timur Kuran and Cass Sunstein published a paper that explains half of what goes wrong in public discourse: "Availability Cascades and Risk Regulation." The concept is a...

Backfire Effect

Brendan Nyhan / Jason Reifler

In 2010, Brendan Nyhan and Jason Reifler published a study that broke a fundamental assumption about how persuasion works. They showed groups of participants fake news articles...

Big Five Personality Traits

Paul Costa / Robert McCrae

In 1992, Paul Costa and Robert McCrae published the NEO Personality Inventory — Revised, and personality psychology finally had a framework that survived replication. After...

Bounded Rationality

Herbert Simon

Herbert Simon introduced bounded rationality in 1955 and won the Nobel Prize in Economics for it in 1978. The core claim dismantled a century of economic orthodoxy: humans do not...

Chesterton's Fence

G.K. Chesterton

G.K. Chesterton: "Don't ever take a fence down until you know the reason it was put up." Before removing a rule, process, or structure, understand why it exists. The principle is...

Classical Conditioning

Pavlov

Pavlov (1890s): a neutral stimulus paired with an unconditioned stimulus becomes a conditioned stimulus. The bell → salivation. The mechanism is deceptively simple: pair a neutral...

Commitment & Consistency

Robert Cialdini

Cialdini's principle: people want to be consistent with their past commitments. Foot-in-the-door — a small yes leads to a bigger yes. Public commitments are stickier than private...

Conformity

Solomon Asch / Gregory Berns

In 1951, Solomon Asch put seven people in a room and showed them a line on a card. He then showed them three comparison lines — A, B, and C — and asked which one matched the...

DISC Model

William Marston / Walter Clarke / John Geier

In 1928, William Marston published Emotions of Normal People, proposing four behavioural styles: Dominance (direct, results-driven), Influence (outgoing, relationship-focused),...

Delayed Gratification

Walter Mischel

In 1970, Walter Mischel sat four-year-olds down at a table at Stanford's Bing Nursery School and placed a single marshmallow in front of each one. The deal was simple: eat the...

Denial

Elizabeth Kübler-Ross

In 1975, a 24-year-old Kodak engineer named Steven Sasson built the first digital camera. It was ugly — a toaster-sized device that captured a 0.01-megapixel black-and-white image...

Ego Depletion

Roy Baumeister / Shai Danziger

In 1998, Roy Baumeister ran an experiment that reshaped how psychologists think about self-control. Subjects were placed in a room with freshly baked chocolate chip cookies and a...

Embodied Cognition

Lakoff & Johnson

Lakoff and Johnson's framework: thought is shaped by the body. We "grasp" ideas, "warm" to people, give "cold" shoulders. The language is not decorative. It reveals the...

Essentialism

Greg McKeown / Dieter Rams

In 2014, Greg McKeown published Essentialism: The Disciplined Pursuit of Less — a book whose subtitle contains its entire thesis. Not "the lazy pursuit of less." Not "the...

Gambler's Fallacy

On August 18, 1913, at the Monte Carlo Casino, the roulette wheel landed on black. Then black again. And again. Twenty-six consecutive times. Gamblers watched the first ten spins...

Golem Effect

Robert Rosenthal / Lenore Jacobson

In 1968, Robert Rosenthal and Lenore Jacobson ran an experiment at a San Francisco elementary school that would reshape how psychologists thought about expectation and...

Hippo Problem

Avinash Kaushik

Highest Paid Person's Opinion: the tendency to defer to the most senior person in the room, regardless of data. Avinash Kaushik named it in 2006 while watching web analytics teams...

Hyperbolic Discounting

Richard Herrnstein / George Ainslie

We discount future rewards more than exponential discounting predicts. $100 today vs $110 tomorrow — we take $100. $100 in a year vs $110 in a year and a day — we take $110. The...

Illusion of Control

Ellen Langer

In 1975, Ellen Langer ran a deceptively simple experiment at Yale. She sold lottery tickets to office workers. Half chose their own ticket. Half were assigned one at random....

Illusory Truth Effect

Lynn Hasher / David Goldstein / Thomas Toppino

In 1977, Lynn Hasher, David Goldstein, and Thomas Toppino ran an experiment that should have rewritten every communications playbook. They presented subjects with plausible...

Intrinsic vs Extrinsic Motivation

Edward Deci / Richard Ryan

Edward Deci and Richard Ryan's Self-Determination Theory identifies three innate psychological needs that drive human motivation: autonomy (the need to direct your own life and...

Intuition

Kahneman / Klein / Jobs

Daniel Kahneman's System 1 is fast, automatic, pattern-based. It does not deliberate. It recognises. Intuition is compressed experience — the brain's way of delivering answers...

Irrational Escalation

Barry Staw

Sunk cost fallacy in action: doubling down on failing projects to justify past investment. Barry Staw's 1976 study gave MBA students the role of a financial VP allocating R&D...

Learned Helplessness

Martin Seligman / Steven Maier

In 1967, Martin Seligman and Steven Maier ran an experiment at the University of Pennsylvania that would rewrite the psychology of motivation. They placed dogs in a shuttle box —...

Maslow's Hierarchy

Abraham Maslow

Abraham Maslow published "A Theory of Human Motivation" in 1943 and proposed five levels of need: physiological, safety, love/belonging, esteem, self-actualization. Lower needs...

Mental Accounting

Richard Thaler

Richard Thaler (1985): people treat money differently based on where it came from or what it's for. Lottery winnings are "house money" — spent more freely. Tax refunds feel like...

Motivation

Victor Vroom

Motivation is the force that drives behaviour. Victor Vroom's Expectancy Theory (1964) distils it into three multiplicative factors: expectancy × instrumentality × valence. Can I...

Neglect of Probability

Kahneman & Tversky / Gerd Gigerenzer

Humans don't evaluate risk by computing probabilities. They evaluate risk by imagining outcomes. The more vivid the outcome — the more easily they can picture the plane crash, the...

Nudging

Thaler & Sunstein

Thaler and Sunstein (2008): small changes in choice architecture that alter behaviour without restricting options. Organ donation opt-out vs opt-in — participation swings from...

Overthinking

Barry Schwartz / Sheena Iyengar / Jeff Bezos / Reed Hastings

Analysis paralysis is excessive rumination that impairs decision-making. The brain keeps cycling through options, scenarios, and objections long after the marginal value of...

Pattern Matching

Humans are pattern-seeking machines. We see faces in clouds, conspiracies in randomness. The brain compresses overwhelming input into actionable understanding by matching new...

Placebo Effect

Expectation creates physiological change. Sugar pills reduce pain when patients believe they're medicine — not because the pain is imagined, but because the brain releases...

Priming

John Bargh

Exposure to a stimulus influences response to a subsequent stimulus. Bargh's elderly-walking study (1997): subjects primed with "elderly" words — Florida, bingo, wrinkle, grey —...

Reactive Devaluation

Lee Ross

Lee Ross (1995): proposals are devalued because of who proposed them. The same deal from an adversary is worth less than from a neutral party. In mergers, the target's proposal is...

Risk Compensation

Sam Peltzman

In 1975, University of Chicago economist Sam Peltzman published a study that infuriated the safety establishment. He looked at the effect of mandatory seatbelt laws on traffic...

Scout Mindset

Julia Galef

Julia Galef spent a decade studying why some people update their beliefs when confronted with evidence and others dig in. Her framework, published in The Scout Mindset (2021),...

Selective Perception

Christopher Chabris / Daniel Simons

We perceive what we expect or want to see. The same data supports opposing conclusions. Confirmation bias is selective perception in action — the downstream effect of a filter...

Sensemaking

Karl Weick / Wagner Dodge

Karl Weick: how people make sense of ambiguous situations. Sensemaking is retrospective — we understand what we did after we've done it. It's social — we construct meaning through...

Seven Deadly Sins

Pope Gregory the Great

Pride, greed, wrath, envy, sloth, gluttony, lust — Pope Gregory the Great codified these seven failure modes in 590 AD. Strip the theology and what remains is a taxonomy of...

Stereotyping

Kahneman / Bertrand / Mullainathan

Applying generalized beliefs about a group to individuals. The brain's compression algorithm — efficient but often wrong. In hiring: "Stanford grads are smart" functions as a...

Suggestibility

Loftus

The tendency to accept and act on suggestions from others. Children are highly suggestible; adults less so, but not immune. Leading questions shape memory — Loftus showed that a...

Tribalism

Tajfel

In-group favouritism and out-group hostility. We evolved in tribes; us vs them is default. The brain doesn't need a reason to form a tribe. It needs a label. Tajfel proved this...

Variable Reinforcement

B.F. Skinner / Wolfram Schultz

B.F. Skinner put pigeons in boxes and gave them food pellets for pressing a lever. When the pellet came every time — fixed reinforcement — the pigeons pressed at a steady rate....

Zeigarnik Effect

Bluma Zeigarnik

In 1927, Bluma Zeigarnik was sitting in a Viennese café with her doctoral adviser, Kurt Lewin, when Lewin noticed something about the waiter. The waiter could remember every...

Abstract Blindness

Abstract blindness is the tendency to overlook or undervalue abstract factors — probabilities, systemic causes, long-term effects — because concrete, vivid, or immediate...

Ambiguity Bias

Ambiguity bias is the tendency to prefer options where the probability of a favorable outcome is known over options where the probability is unknown — even when the unknown option...

Anecdotal Fallacy

The anecdotal fallacy is using a personal experience or single example as proof of a general claim — substituting a vivid story for statistical evidence. "My uncle smoked his...

Appeal to Novelty

Appeal to novelty is the assumption that newer is better — that the latest idea, tool, or method is superior because it is recent. Recency is mistaken for progress. The core idea:...

Association Bias

Association bias is judging something by what it's linked to — people, brands, contexts — rather than by its own attributes. We transfer feelings and beliefs from one thing to an...

Aumann's Agreement Theorem

Robert Aumann

Aumann's agreement theorem says that two rational agents who share a common prior and whose posteriors are common knowledge cannot agree to disagree — they must converge to the...

Authority Bias

Authority bias is the tendency to overweight the views or orders of people we see as authorities — titles, credentials, status — and to underweight the content of what they say....

Automation Bias

Automation bias is the tendency to over-trust automated systems — algorithms, dashboards, tools — and to under-check or override our own judgment when the system suggests an...

Belief Bias

Belief bias is the tendency to judge an argument by whether we agree with the conclusion rather than by the quality of the reasoning. We accept valid-looking arguments that...

Blind Spot

Blind spot (in psychology) is the failure to see one's own biases and errors while readily seeing them in others. We have a literal blind spot for our own judgment flaws. The core...

Blindspot Bias

Blindspot bias is the belief that we are less biased than other people — that we see the world more objectively while others are swayed by bias. We spot bias in others easily and...

Bright Spots

Chip Heath / Dan Heath

Bright spots are the positive outliers — people, teams, or cases that succeed where others fail under similar conditions. Instead of only studying failure or the average, study...

Bucket Error

A bucket error occurs when you misclassify something by putting it in the wrong mental category — and then reason about it based on the category rather than the thing itself. The...

Burnout

Burnout is the state of chronic physical and emotional exhaustion caused by prolonged stress without adequate recovery — characterized by three dimensions: exhaustion, cynicism,...

Catharsis

Aristotle

Catharsis is the release of strong emotions through expression, producing a sense of relief or renewal. Aristotle introduced it to explain why audiences leave tragedies feeling...

Caveman Syndrome

Caveman Syndrome is the recognition that our brains evolved for a world radically different from the one we now inhabit. The mental hardware running your decisions was optimised...

Change Bias

Change Bias is the systematic tendency to either overestimate or underestimate the impact of a change, depending on your relationship to it. Those proposing a change tend to...

Cheerleader Effect

The Cheerleader Effect is the cognitive bias where individuals appear more attractive, competent, or impressive when presented as part of a group than when evaluated alone. The...

Cherry-Picking

Cherry-picking is the practice of selecting only the evidence that supports your pre-existing conclusion while ignoring evidence that contradicts it. Unlike confirmation bias —...

Cognitive Scope Limitation

Cognitive Scope Limitation is the recognition that the human mind has a finite capacity for the range and complexity of problems it can hold simultaneously. We struggle to think...

Compassion Face

Compassion Face is the phenomenon where people unconsciously mirror empathetic facial expressions and body language to signal understanding and care — regardless of whether they...

Conflict

Conflict is the inevitable tension that arises when individuals, teams, or organisations have incompatible goals, values, or interpretations. Most people treat conflict as a...

Congruence Bias

Congruence Bias is the tendency to test a hypothesis exclusively by searching for evidence that confirms it, rather than by attempting to falsify it or testing alternative...

Conservatism Bias

Conservatism Bias is the tendency to insufficiently update beliefs when presented with new evidence. Even when confronted with data that should significantly change your view, you...

Context Effect

The Context Effect is the principle that the environment, setting, and surrounding information fundamentally alter how people perceive, evaluate, and decide. The same product...

Continued Influence Effect

The Continued Influence Effect describes how information that has been clearly corrected or retracted continues to shape thinking and decision-making. Even after you learn that an...

Courtesy Bias

Courtesy Bias is the tendency to give opinions that are more socially acceptable or agreeable than one's true assessment, particularly in face-to-face settings. People tell you...

Cryptomnesia

Cryptomnesia is the phenomenon where a forgotten memory returns without being recognised as such — you experience a recalled idea as if it were an original thought. You read...

Cult Indoctrination

Cult Indoctrination describes the systematic process by which individuals are drawn into extreme group loyalty through a predictable sequence of psychological techniques:...

Declinism

Declinism is the belief that society, an institution, or a situation is getting worse — and that the past was better than it actually was. It combines rosy retrospection...

Distinction Bias

Distinction bias is the tendency to overvalue differences between options when evaluating them side by side, compared to how we'd experience them separately. In joint evaluation...

Duration Neglect

Duration neglect is the psychological finding that people judge an experience primarily by its most intense moment and its ending, largely ignoring how long it lasted. A...

Echo Chamber Effect

The echo chamber effect is the amplification of beliefs that occurs when people are surrounded only by others who share their views. Dissenting information is absent, agreement is...

Effort Justification

Effort justification is the tendency to value outcomes more highly when we've worked hard to achieve them — regardless of the outcome's actual quality. If it was painful to get,...

Egocentric Bias

Egocentric bias is the tendency to overestimate our own contribution, perspective, or importance relative to others. We remember our inputs more vividly, weigh our opinions more...

Eloquence

Eloquence bias is the tendency to judge the quality of an idea by how well it is expressed rather than by its actual merit. A beautifully articulated argument feels more true; a...

Emotional Contagion

Emotional contagion is the automatic, often unconscious transfer of emotions between people. Moods spread — anxiety, enthusiasm, frustration, calm — through facial expressions,...

Exaggerated Expectation

Exaggerated expectation is the tendency to expect outcomes — whether positive or negative — to be more extreme than they actually turn out to be. We overshoot in both directions:...

Excessive Fairness Bias

Excessive fairness bias is the tendency to prioritise equal treatment over optimal outcomes — distributing resources, credit, or attention evenly when the situation demands...

Extremeness Aversion

Extremeness aversion is the tendency to avoid the most extreme option in a set, regardless of its actual merit. When choosing between three options, people disproportionately...

False Consensus

False consensus is the tendency to overestimate how many other people share our beliefs, values, and behaviours. We assume our views are more common and representative than they...

False Memory

False memory is the phenomenon where we recall events that didn't happen or recall real events differently from how they occurred. Memory is not a recording — it's a...

False Precision

False precision is presenting a number or estimate with more specificity than the underlying data supports. Saying "the market is $4.27 billion" when the real answer is "roughly...

First-conclusion Bias

First-conclusion bias is the tendency to accept the first explanation or solution that comes to mind and stop searching for better ones. Our brains are wired to resolve...

Focalism

Kahneman

Focalism — also called the focusing illusion — is the tendency to overweight a single aspect of an event when making predictions or evaluations. When estimating how a new hire,...

Forecast Bias

Forecast Bias is the systematic tendency for predictions to skew in a consistent direction — typically toward overconfidence, optimism, or the continuation of current trends. It...

Gateway Drug Theory

Gateway Drug Theory proposes that exposure to a mild experience lowers the threshold for progressively more intense versions of that experience. In its original context, the...

Group Attribution Error

Group Attribution Error is the tendency to assume that the characteristics or decisions of a group reflect the preferences of every individual within it — or that a single...

Humor Effect

The Humor Effect is the cognitive phenomenon where humorous information is remembered better than non-humorous information. Jokes, wit, and playful framing create stronger memory...

Hypernovelty

Hypernovelty describes the modern condition of being surrounded by an endless stream of new stimuli — news, notifications, content, products, trends — that hijacks the brain's...

Ideological Bias

Ideological Bias is the tendency to interpret information, evaluate evidence, and make decisions through the lens of a pre-existing belief system rather than on the merits. When...

Illusion of Skill

The Illusion of Skill is the mistaken belief that consistent patterns in outcomes reflect genuine expertise rather than luck, randomness, or environmental factors. Professionals...

Illusion of Transparency

The Illusion of Transparency is the belief that your internal states — intentions, emotions, knowledge — are more apparent to others than they actually are. You think your...

Illusion of Validity

Kahneman / Tversky

The Illusion of Validity is the cognitive bias where high confidence in a judgment persists even when the evidence underlying that judgment is known to be unreliable. When...

Impact Bias

Impact Bias is the tendency to overestimate the intensity and duration of emotional reactions to future events — both positive and negative. We predict that a major win will make...

Inattentional Bias

Inattentional Bias — sometimes called inattentional blindness — is the failure to notice fully visible and relevant information because your attention is directed elsewhere. The...

Inconsistency-Avoidance

Charlie Munger

Inconsistency-Avoidance is the brain's deep resistance to holding or acting on contradictory beliefs, ideas, or behaviours. To conserve energy and maintain a stable self-concept,...

Information Bias

Information Bias is the tendency to seek more information even when it will not change the decision. It manifests as the belief that more data always leads to better outcomes —...

Ingroup Bias

Ingroup Bias is the automatic tendency to favour members of your own group — giving them more trust, more benefit of the doubt, more resources, and more favourable interpretations...

Interpretation & Reinterpretation

Interpretation & Reinterpretation describes the mind's constant process of assigning meaning to events — and then revising that meaning when new information, new context, or new...

Jealousy/Envy Tendency

Charlie Munger

Jealousy/Envy Tendency is the deep-seated human impulse to feel pain at the success or advantages of others — particularly those we perceive as similar to ourselves. Envy targets...

Least Effort Principle

The Least Effort Principle states that when faced with multiple paths to a goal, humans (and most organisms) will reliably choose the one requiring the least total work —...

Leveling & Sharpening

Leveling & Sharpening describes the systematic distortion that occurs when information passes through memory or communication. Leveling is the loss of detail — nuance, context,...

Liking/Loving Bias

Liking/Loving Bias is the tendency to distort your judgement in favour of people, products, or ideas you like or love. When you like someone, you overvalue their virtues,...

Ludic Fallacy

Nassim Nicholas Taleb

The Ludic Fallacy — from the Latin ludus, meaning game — is the mistake of applying the clean, well-defined rules of games and models to the messy, open-ended reality of the real...

Masked Man Fallacy

The Masked Man Fallacy — also called the intensional fallacy — occurs when someone assumes that because they know something under one description, they must know it under all...

Mental Simulation

Mental Simulation is the cognitive process of imagining how events will unfold — running scenarios in your mind before they happen. It's how founders envision product launches,...

Mere Exposure Effect

Robert Zajonc

The Mere Exposure Effect is the phenomenon where repeated exposure to a stimulus — a face, a brand, a song, an idea — increases your preference for it, independent of any new...

Momentum Bias

Momentum Bias is the tendency to continue a course of action primarily because it's already in motion — not because ongoing evidence supports it. Once energy, resources, and...

Multiple Tendencies

Charlie Munger

Multiple Tendencies refers to the reality that human behaviour is rarely driven by a single psychological force. At any given moment, several cognitive biases, emotional drives,...

Negativity Bias

Negativity Bias is the tendency for negative experiences, information, and emotions to have a disproportionately larger effect on psychological states and decisions than neutral...

Normalcy Bias

Normalcy Bias is the tendency to assume that because something has never happened before, it won't happen — or that because things have always been a certain way, they'll continue...

Omission Bias

Omission Bias is the tendency to judge harmful actions as worse than equally harmful inactions — to feel that doing something that causes damage is morally and psychologically...

Optimism Bias

Optimism Bias is the tendency to overestimate the likelihood of positive outcomes and underestimate the likelihood of negative ones — particularly for events involving yourself....

Optimistic Probability Bias

Optimistic Probability Bias is the specific tendency to overestimate the probability of favourable events and underestimate the probability of unfavourable ones. While Optimism...

Outcome Bias

Outcome Bias is the tendency to judge the quality of a decision based on its outcome rather than the quality of the decision-making process at the time it was made. A risky bet...

Paradox of Knowledge

The Paradox of Knowledge is the observation that the more you learn about a subject, the more you realise how much you don't know — and conversely, the less you know, the more...

Paranoia

Andy Grove

Paranoia, in the business context, is a heightened state of vigilance toward threats — real and imagined — that can be either debilitating or productive depending on how it's...

Pareidolia

Pareidolia is the tendency to perceive meaningful patterns — particularly faces, shapes, or signals — in random or ambiguous stimuli. You see a face in the clouds, a trend in...

Peltzman Effect

Sam Peltzman

The Peltzman Effect, named after economist Sam Peltzman, is the observation that safety measures often fail to reduce total harm because people compensate for increased safety by...

Pessimism Bias

Pessimism Bias is the tendency to overestimate the likelihood and severity of negative outcomes. While optimism bias skews projections upward, pessimism bias skews them downward —...

Physical/Psychological Pain Bias

Physical/Psychological Pain Bias describes the tendency for the anticipation and experience of pain — whether physical or emotional — to dominate decision-making beyond what...

Placement Bias

Placement Bias is the tendency for the position of information — where it appears in a sequence, on a page, in a list, or in a physical space — to disproportionately influence...

Positivity Effect

The Positivity Effect is the tendency — especially pronounced with age and experience — to attend to, remember, and favour positive information over negative information. Seasoned...

Precision Bias

Precision Bias is the tendency to treat precise-sounding numbers as more credible and reliable than round ones, even when the underlying data doesn't support that level of...

Prejudice

Prejudice is a pre-formed judgment about a person, group, or situation based on category membership rather than individual evidence. It operates as a cognitive shortcut: instead...

Present Bias

Present Bias is the tendency to overweight immediate rewards relative to future ones, beyond what rational discounting would justify. Given a choice between $100 today and $120 in...

Primacy Effect

The Primacy Effect is the tendency for the first information received to disproportionately shape opinions, memory, and judgment. In a list of traits, the first ones mentioned...

Pro-innovation Bias

Pro-innovation Bias is the tendency to overvalue new innovations, assuming they should be widely adopted while underestimating their limitations, costs, and the adequacy of...

Procrastination

Procrastination is the act of delaying important tasks in favour of less important but more immediately comfortable ones — despite knowing the delay will cost you. It's not...

Projection Bias

Projection Bias is the tendency to assume that others share your current preferences, beliefs, emotions, or mental state — and that your own future self will feel the same way you...

Pseudocertainty Effect

Kahneman / Tversky

The Pseudocertainty Effect occurs when people treat an outcome as certain even though it's merely probable, because the decision has been mentally separated into stages. In a...

Publication Bias

Publication Bias is the systematic tendency for studies with positive, significant, or novel results to get published while studies with null, negative, or replicative results...

Rashomon Effect

Akira Kurosawa

The Rashomon Effect — named after Akira Kurosawa's film — describes how the same event produces multiple contradictory but individually plausible accounts, each shaped by the...

Reason-Respecting Tendency

Ellen Langer

The Reason-Respecting Tendency is the human inclination to comply more readily with a request when a reason is provided — even if the reason is trivial or circular. Ellen Langer's...

Recency Illusion

The Recency Illusion is the belief that something you've only recently noticed must itself be recent. You learn a new word and suddenly hear it everywhere; you discover a business...

Reciprocation Bias

Reciprocation Bias is the deep-seated compulsion to return favours, gifts, and concessions — even when the original gesture was uninvited, unwanted, or strategically calculated....

Reductive Bias

Reductive Bias is the tendency to oversimplify complex, multi-causal phenomena by attributing them to a single cause or a simple explanation. When a product fails, it must have...

Restraint Bias

Restraint Bias is the tendency to overestimate your ability to control impulsive behaviour. People who believe they have strong willpower expose themselves to more temptation —...

Reward & Punishment

Reward and Punishment is the foundational behavioural principle that organisms repeat behaviours that are rewarded and avoid behaviours that are punished. It sounds elementary,...

Ringelmann Effect

Max Ringelmann

The Ringelmann Effect is the finding that individual effort decreases as group size increases. In a tug-of-war experiment, each person pulls less hard when more people are on the...

Sapir-Whorf Hypothesis

Edward Sapir / Benjamin Lee Whorf

The Sapir-Whorf Hypothesis proposes that the language you use shapes how you think — not just how you communicate, but what you're capable of perceiving and reasoning about. In...

Scarcity Bias

Scarcity Bias is the tendency to assign greater value to things that are scarce, limited, or dwindling in availability — regardless of their objective worth. When something...

Self-Enhancement Bias

Self-Enhancement Bias is the tendency to perceive yourself as above average on desirable traits — intelligence, skill, ethics, driving ability — even when statistical reality...

Self-Handicapping

Self-Handicapping is the strategy of creating obstacles to your own performance so that failure can be attributed to those obstacles rather than to lack of ability. A student who...

Self-Serving Bias

Self-Serving Bias is the tendency to attribute your successes to internal factors — talent, effort, intelligence — while blaming your failures on external circumstances — bad...

Self-consistency Bias

Self-consistency Bias is the tendency to perceive your past beliefs, attitudes, and behaviours as more consistent with your current ones than they actually were. People...

Self-relevance Effect

The self-relevance effect is the tendency for people to process and remember information more deeply when it relates to them personally. Messages framed around "you" and "your...

Semmelweis Reflex

Ignaz Semmelweis

The Semmelweis Reflex is the automatic tendency to reject new evidence or knowledge because it contradicts established norms, beliefs, or paradigms. Named after Ignaz Semmelweis —...

Serial Recall Effect

The serial recall effect describes how the position of information in a sequence determines how well it's remembered. Items at the beginning (primacy) and end (recency) of a list...

Simplicity Bias

Simplicity bias is the tendency to prefer simple explanations and solutions even when the situation is genuinely complex. Unlike Occam's Razor — which recommends parsimony as a...

Sleeper Effect

The sleeper effect is the phenomenon where a message becomes more persuasive over time as the recipient forgets the source but retains the content. Initially, a low-credibility...

Social Comparison Bias

Social comparison bias is the tendency to favour or disfavour people based on how they compare to us — particularly resisting those who are perceived as superior in areas where we...

Social Desirability Bias

Social desirability bias is the tendency for people to answer questions and present themselves in ways they believe will be viewed favourably by others — rather than answering...

Stress-Influence Bias

Stress-influence bias is the tendency for acute stress to distort decision-making — narrowing attention, amplifying loss aversion, and collapsing complex trade-offs into binary...

Subjective Validation

Subjective validation is the tendency to perceive a statement or piece of information as true if it holds personal meaning or significance — regardless of whether it's objectively...

Testing Effect

The testing effect is the finding that actively retrieving information from memory strengthens long-term retention far more than passively reviewing the same material. Testing...

The Onion Brain

The Onion Brain is the model that human cognition operates in layers — from fast, instinctive reactions at the core to slow, deliberate reasoning at the surface. Each layer...

Threat Lockdown

Threat lockdown is the cognitive state where a perceived threat causes the brain to narrow focus, suppress peripheral information, and lock onto the danger source. While useful...

Three Men Make A Tiger

Three Men Make A Tiger is the ancient Chinese proverb that illustrates how repetition from multiple sources creates belief — even in absurdities. If one person tells you there's a...

Time-Saving Bias

Time-saving bias is the tendency to overestimate the time saved when increasing speed from a slow pace and underestimate the time saved when increasing from an already fast pace....

Trait Ascription Bias

Trait ascription bias is the tendency to view oneself as relatively variable in personality and behaviour while viewing others as more predictable and fixed. You see your own...

Turkey Illusion

Nassim Taleb

The turkey illusion — derived from Nassim Taleb's parable — describes the danger of inferring safety from a long history of stability. A turkey is fed every day for 1,000 days,...

Ultimate Attribution Error

The ultimate attribution error extends the fundamental attribution error to groups. When members of our ingroup succeed, we attribute it to character and ability. When they fail,...

Uncertainty Avoidance

Uncertainty avoidance is the degree to which people feel threatened by ambiguous or unknown situations and create structures — rules, rituals, processes — to reduce that...

Victim-blaming

Victim-blaming is the tendency to attribute fault to the person who suffered harm rather than to the circumstances or the perpetrator. It stems from the psychological need to...

Vividness Illusion

The vividness illusion is the tendency to give disproportionate weight to vivid, emotionally charged, or easily imagined information — while underweighting pallid but...

Zero-sum Heuristic

The zero-sum heuristic is the default cognitive shortcut that treats most interactions as zero-sum — where one party's gain must come at another's expense — even when the...

Stockdale Paradox

Named after Admiral James Stockdale, the highest-ranking U.S. military officer held as a prisoner of war in Vietnam. The paradox: you must maintain unwavering faith that you will prevail in the end, while simultaneously confronting the most brutal facts of your current reality. The leaders who survived were not the optimists — they were the realists who never lost faith.