1001 – Behavioral Science Dictionary

Plain-language definitions of 1001 behavioral science terms — cognitive biases, heuristics, decision-making, nudging, motivation, and behavioral economics. Each term has its own page with the full entry, worked examples, its origin, and cross-links to related ideas. Free, and open to everyone.

Behavioral Economics

Adverse selection: When the hidden-information party self-selects, the worst risks crowd in.
Altruistic punishment: Paying out of your own pocket to penalize a cheater who never wronged you directly.
Anchoring contrast in assortments: Show the expensive item first and everything after looks cheap.
Anchoring with quantity limits: A 'limit 12 per customer' sign makes shoppers buy more.
Animal spirits: The waves of confidence and fear that drive economic activity beyond cold calculation.
Backward induction: Solve a sequential game by reasoning from the last move back to the first.
Bait-and-switch: Lure buyers with a deal that vanishes, then sell them something pricier.
Bandwagon pricing cue: Labeling an option 'most popular' makes more people pick it.
Battle of the sexes: Both want to be together, but each prefers a different place to meet.
Beauty contest game: Win by guessing not what's true, but what everyone thinks everyone thinks.
Behavioral game theory: Game theory rebuilt around how people actually play.
Bid shading: Bidding less than you think it's worth, on purpose.
Bounded self-interest: Real people care about fairness and others, not just their own payoff.
Bounded willpower: People know what's good for them and still fail to do it, because willpower is finite.
Centipede game: A growing pot that rational theory says you should grab immediately — but people don't.
Charm pricing: Prices ending in 9 feel meaningfully cheaper than the round number above.
Cheap talk: Costless, nonbinding words that may or may not be believed.
Common-value auction: An auction for something worth the same to everyone, if only they knew what.
Conspicuous consumption: Buying expensive things precisely so others see you can.
Coordination game: A game where players win by matching each other, not by outsmarting them.
Costly signaling: A signal is believable precisely because it would be too expensive to fake.
Coupling of consumption and payment: How tightly a payment is mentally tied to the pleasure it buys changes how both feel.
Decoupling (payment): Separating payment from consumption changes how both feel.
Decoy pricing: Add a deliberately bad-value option to push buyers to the target tier.
Dictator game: One player simply decides how much, if any, to give the other.
Dominant strategy: A move that's your best response no matter what anyone else does.
Dominated strategy: A move that's never worth playing because another always does at least as well.
Drip pricing: Reveal the real total in dribs and drabs, after the buyer is hooked.
Equity premium puzzle: Stocks have historically out-earned bonds by far more than rational risk aversion can explain.
Evolution of cooperation: How cooperation among selfish agents can arise and survive without a referee.
Extrapolation bias: Investors expect recent trends to continue, projecting the past straight into the future.
Fairness: People value fair outcomes and processes, and pay to enforce them.
Flat-rate bias: People prefer flat-rate plans even when pay-per-use would cost less.
Focal point: The obvious answer people converge on when they must coordinate without talking.
Folk theorem: In a long-enough relationship, almost any outcome — including cooperation — can be sustained.
Free riding: Enjoying a shared benefit without paying your share.
Fungibility: A dollar is a dollar — in theory, but not in the mind.
Game of chicken: Two players race toward collision; whoever swerves first loses face, but crashing is worst.
Goal dilution: A product that claims to do many things seems worse at each one.
Herding: Investors imitate the crowd instead of acting on their own information.
Home bias: Investors pile into their own country's stocks and skip the diversification benefits abroad.
Homo economicus: The fictional, perfectly rational and self-interested agent of classical theory.
IKEA effect: We overvalue what we built ourselves.
Indirect reciprocity: Be good to others and a watching world will be good to you.
Inequity aversion: People dislike unequal payoffs — resenting getting less, and uneasy getting more.
Iterated dominance: Solve a game by repeatedly deleting moves no rational player would make.
January effect: Small stocks tend to pop in January, defying efficient markets.
Keeping up with the Joneses: We benchmark our spending and satisfaction against our neighbors'.
Kin selection: Helping relatives spreads your genes, so altruism toward kin can evolve.
Labor illusion: Visible effort makes a service feel more valuable, even if it's slower.
Left-digit effect: We judge a price mostly by its first digit, so $3.00 dwarfs $2.99.
Level-k thinking: People reason only a few steps deep about what others will do.
Lexicographic preferences: Ranking options by one all-important attribute first, breaking ties only by the next.
Limits to arbitrage: Smart money can't always correct mispricing, so it persists.
Mixed strategy: Randomizing your moves so opponents can't predict you.
Momentum: Recent winners keep winning and recent losers keep losing, longer than they should.
Money illusion: Judging money by its face value rather than its real purchasing power.
Money pump: If your preferences are inconsistent, someone can cycle you through trades until you're broke.
Moral hazard: Shielded from the downside, people take risks they otherwise wouldn't.
Narrow framing: Judging each gamble in isolation instead of as one part of the whole portfolio.
Nash equilibrium: A stable combination of strategies where no player can gain by changing course alone.
Network effect: A product becomes more valuable to each user as more people use it.
Neuroeconomics: Using neuroscience to understand how the brain makes economic decisions.
Noise trader: An investor who trades on hunches and sentiment rather than fundamental information.
Noise-trader risk: Mispricing can get worse before it gets better, and that danger scares off arbitrageurs.
Nominal versus real: The face-value number versus what it can actually buy after inflation.
Opportunity cost: The value of the best alternative you give up whenever you choose.
Overtrading: The more people trade, the lower their returns — yet they keep trading.
Pareto efficiency: An outcome where no one can be made better off without making someone worse off.
Partitioned pricing: Splitting a price into base plus surcharges makes the total feel smaller.
Pay-what-you-want pricing: Let buyers set the price, and fairness norms keep it above zero.
Payment depreciation: The sting of a payment fades over time, loosening the link between cost and use.
Penny-a-day framing: Quoting a cost as 'just $1 a day' makes it feel trivial.
Positional good: A good whose value comes from how much of it you have relative to others.
Price anchoring: A reference number makes the actual price look like a deal or a rip-off.
Price-quality heuristic: If it costs more, we assume it must be better.
Principal-agent problem: How do you get someone to act in your interest when you can't watch their every move?
Prisoner's dilemma: Two rational players each defect — and both end up worse off than if they had cooperated.
Private-value auction: An auction where the prize is worth a different, personal amount to each bidder.
Protected values: Commitments people refuse to trade against money at any price, on principle.
Public goods game: Everyone gains if all contribute, but each individual is tempted to free-ride on the rest.
Rational choice theory: Agents choose consistently to maximize their own utility given their constraints.
Reciprocal altruism: Helping others now in the expectation that the help will be returned later.
Reference price: The price you expect to pay, which all real prices get judged against.
Scarcity through exclusivity: Restricting who can have something makes it more desirable.
Screening: The uninformed side designs choices that make the informed side reveal its type.
Signaling: Taking a costly, observable action to credibly reveal hidden information about yourself.
Stag hunt: Cooperate for a big shared prize, but only if you trust the other to cooperate too.
Strong reciprocity: A drive to reward kindness and punish unfairness even at a net cost to yourself.
Subgame perfection: An equilibrium that stays rational at every point, ruling out empty threats.
Subjective expected utility: Rational choice under uncertainty using your own probabilities and values.
Tit-for-tat: Start by cooperating, then simply do whatever your partner did last time.
Tragedy of the commons: Shared resources get overused when each person's incentives diverge from the group's interest.
Transaction utility: The pleasure or pain of the deal itself, separate from the value of the thing bought.
Transitivity: If you prefer A to B and B to C, consistency demands you prefer A to C.
Trust game: Send money that grows on the way, trusting the other person to send a fair share back.
Ultimatum game: Split a sum — but if the responder rejects the offer, both walk away with nothing.
Value premium: Cheap, unglamorous stocks have historically beaten expensive, glamorous ones.
Veblen good: A good people want more of precisely because it is expensive.
Winner's curse: Win a common-value auction and you've probably overpaid.

Choice Architecture

Active choosing: Requiring people to make a deliberate choice rather than defaulting them.
Asymmetric paternalism: Policies that help people who make mistakes while imposing little or no cost on those who are fully rational.
Boomerang effect: A norm message that backfires for people already doing well.
Boosting: Building people's own competence to decide well, rather than steering their choice from the outside.
Channel factors: Small situational details that open or block a path to action.
Choice architecture: The design of the environment in which people make decisions.
Choice editing: Removing the worst options from the choice set so people don't have to, narrowing what is on offer.
Dark nudge: A nudge engineered to serve the architect's interest at the expense of the person being nudged.
Dark patterns: Interface tricks that manipulate users against their interests.
Debiasing: Techniques that reduce or correct for cognitive biases in judgment and decisions.
Default effect: Whatever is pre-selected is what most people end up with.
Default rules: The pre-set options that take effect unless people actively choose otherwise — the most powerful lever in choice architecture.
Feedback (behavioral): Showing people the consequences of their actions to guide them.
Forcing function: A design constraint that physically prevents an error or makes the desired action unavoidable.
Friction: The small costs and hassles that quietly throttle behavior.
Friction audit: Cataloguing the small hassles in a process to decide where to remove friction — or deliberately add it.
Gamification: Using game design elements to motivate ordinary, non-game behavior.
Goal framing: Stressing what you'll lose by not acting versus what you'll gain by acting.
Green nudge: A choice-architecture change designed to encourage environmentally friendly behavior without mandates.
Hypernudge: Data-driven, personalized, real-time nudging powered by algorithms and continuous behavioral feedback.
Implementation intentions: Pre-deciding exactly when, where, and how you will act.
Inertia: People tend to stay on the current path simply because changing takes effort and intention.
Libertarian paternalism: Steering people toward better choices while fully preserving their freedom to choose.
Nudge: A small change in how choices are presented that predictably shifts behavior without banning options or changing economic incentives.
Nudge for good: The ethical mandate that choice architecture should serve the chooser, not the architect.
Nudge plus: A nudge deliberately paired with a moment of reflection, so people understand and endorse the steer rather than being moved automatically.
Nudgeability: How susceptible a given person, behavior, or context is to being nudged in the first place.
Opt-in versus opt-out: Whether the default is participation or not quietly determines who takes part.
Personalized defaults: Pre-set options tailored to each individual's likely preferences, rather than one default for everyone.
Portion-size effect: Give people a bigger serving and they eat more, almost without noticing.
Priming: Exposure to a cue subtly shapes how we respond to something related a moment later.
Rebound effect: Efficiency gains get partly eaten up because the cheaper behavior invites more of it.
RECAP: A disclosure tool that gives consumers a clear annual record of what they actually used and were charged, to enable comparison.
Reframing: Recasting how an option or situation is described to change how it is perceived and chosen.
Reminders: Timely prompts that close the gap between what people intend and what they do.
Salience: We act on whatever stands out and captures attention, regardless of its true importance.
Self-nudging: People applying choice-architecture techniques to their own environment to steer their future behavior.
Simplification: Cutting complexity so the desired action is easy to take.
Sludge: Excessive friction that obstructs people from acting in their own best interest.
Sludge audit: A systematic review of a process to find and remove the friction that blocks people from what they want or are owed.
Smart disclosure: Releasing complex information in standardized, machine-readable form so people (and tools) can actually use it to choose well.
Social norms marketing: Campaigns that correct misperceptions of what others do or approve of, to shift behavior toward the true norm.
TIPPME: A standardized classification of ways to change small physical environments — like portion size or product placement — to shift behavior.

Choice, Risk & Value

Allais common-consequence effect: Adding the same outcome to two gambles shouldn't change your ranking — but it does.
Allais paradox: A classic choice pattern that breaks expected utility theory.
Ambiguity aversion: We prefer known risks to unknown ones.
Ambiguity effect: We avoid options whose odds are unknown, even when they may be better.
Attribute framing: Calling something '90% lean' beats '10% fat,' though they're identical.
Break-even effect: Sitting on a loss, people reach for risky bets that offer a shot at getting back to even.
Broad bracketing: Pooling decisions and outcomes so trade-offs and risks are judged as a whole.
Certainty effect: We pay a premium to turn 'very likely' into 'guaranteed.'
Certainty equivalent: The guaranteed amount that feels exactly as good to you as taking a given gamble.
Choice overload: Too many options can paralyze rather than empower.
Compromise effect: The middle option feels safest, so it wins.
Constructed preferences: We often don't have settled preferences waiting to be reported—we build them on the spot.
Cumulative prospect theory: The refined version of prospect theory that weights cumulative probabilities and never breaks dominance.
Decision fatigue: The more decisions you make, the worse they get.
Decision weights: The transformed probabilities people actually act on, not the stated odds.
Decoy effect: Adding a clearly worse third option steers choice between the first two.
Denomination effect: We spend a big bill more reluctantly than the same value in small change.
Description-experience gap: People treat rare risks very differently when they're described versus learned from experience.
Diminishing sensitivity: The first dollar (or degree of pain) registers more than the hundredth.
Disappointment aversion: Outcomes below what you expected sting extra, so you avoid bets that might let you down.
Disappointment theory: We feel choices not just by their outcomes but by how they fall short of, or beat, our expectations.
Disjunction effect: People wait to learn an outcome before acting — even when it wouldn't change the act.
Disposition effect: Selling winners too soon and holding losers too long.
Distinction bias: Comparing options side by side magnifies differences that won't matter later.
Diversification heuristic: Asked to choose several items at once, people spread their picks more than they really want.
Dread risk: Catastrophic, uncontrollable hazards loom far larger in the mind than their odds warrant.
Editing of prospects: The pre-processing stage where a decision is simplified and framed before it is evaluated.
Elimination by aspects: We cut options by ruling out whatever fails one attribute at a time.
Ellsberg paradox: People shun bets with unknown odds, breaking expected utility.
Endowment effect: We value a thing more once it's ours.
Evaluability hypothesis: Hard-to-judge attributes sway us only when we can compare them side by side.
Expected utility theory: The classical model: choose the option with the highest average utility.
Extremeness aversion: Options at the edges feel risky, so the safe-seeming middle gets chosen.
Fourfold pattern of risk attitudes: Risk attitudes flip across four cells defined by gains vs. losses and high vs. low probability.
Framing effect: The same facts, described differently, lead to different choices.
Hedonic editing: We mentally bundle or split gains and losses to feel as good as possible about them.
House money effect: We take bigger risks with money we've just won than with our own.
Independence axiom: A component shared by two gambles should not affect which one you prefer.
Joint–separate evaluation: Whether you see options alone or side by side changes what you prefer.
Less-is-better effect: A smaller, complete gift can be valued above a larger, lesser one.
Loss aversion: Losses hurt roughly twice as much as equivalent gains feel good.
Maximizer vs satisficer: Whether you exhaustively seek the best option or settle for good enough.
Mental accounting: Treating money differently depending on which mental 'pot' it sits in.
Mere ownership effect: Merely owning something makes you like it more, no trading required.
Mere urgency effect: We chase urgent little tasks over important ones, even at a cost.
Myopic loss aversion: Checking risky investments too often makes loss-averse people shun good long-run bets.
Narrow bracketing: Treating each decision in isolation rather than as part of the larger portfolio of choices.
Pain of paying: Parting with money triggers a real, immediate sting that shapes how and how much we spend.
Payment decoupling: Separating payment from consumption in time dulls the pain of paying and changes how we use things.
Peanuts effect: People gamble more freely when the stakes are small enough to feel like 'peanuts.'
Possibility effect: Moving a risk from impossible to merely possible feels disproportionately large.
Preference reversal: Which option you prefer flips when the way you're asked changes.
Probability matching: Guessing each option as often as it actually occurs — when always picking the likeliest wins.
Probability neglect: When an outcome stirs strong feeling, its odds stop mattering to us.
Probability weighting: We overweight rare events and the jump to certainty, and underweight middling probabilities.
Probability weighting function: The inverse-S curve describing exactly how stated odds get distorted into decision weights.
Procedural invariance: The principle — routinely violated — that the way you elicit a preference shouldn't change it.
Prominence effect: The attribute that seems most important dominates choices more than trade-offs.
Prospect theory: How people really decide under risk — gains and losses measured from a reference point, not final wealth.
Pseudocertainty effect: Framing a chancy outcome as 'guaranteed' within one stage makes it feel safe, even when earlier stages are not.
Rank-dependent utility: Probabilities are weighted by an outcome's rank, not one at a time, so dominance is preserved.
Ratio-difference principle: The same gap feels bigger between small numbers than between large ones.
Reason-based choice: We decide by finding good reasons we can articulate, not by computing utilities.
Reference dependence: Value is judged against a reference point, not in absolute terms — so the same outcome can feel like a win or a loss.
Reference point: The baseline against which every outcome is coded as a gain or a loss.
Reference-dependent preferences: A formal model where utility depends on outcomes relative to rationally expected reference points.
Reflection effect: Preferences mirror-flip when a choice between gains is recast as the same choice between losses.
Regret theory: We choose to minimize anticipated regret from comparing what we got with what we passed up.
Risk aversion: Preferring a sure thing to a gamble of equal or even higher expected value.
Risk compensation: Made to feel safer, people take more risks and offset the protection.
Risky-choice framing: A gain frame makes us play it safe; a loss frame makes us gamble.
Salience theory: Attention is drawn to an outcome that stands out, and that outcome gets overweighted in choice.
Scale compatibility: An attribute gets over-weighted when it is already in the units of the answer.
Silver lining principle: A small gain feels better when kept separate from a larger loss it accompanies.
Single-option aversion: A lone option feels risky; add a second and people commit.
Source dependence: We'd rather bet on uncertainty in domains we feel we understand than ones we don't.
St. Petersburg paradox: A bet with infinite expected value that almost no one will pay much to play.
Status quo bias: Sticking with the current option simply because it is the current one.
Subcertainty: Our decision weights for a full set of outcomes add up to less than one.
Subproportionality: Cutting a probability hurts more when it starts out small.
Sunk cost fallacy: Throwing good money after bad because of what has already been spent.
Sure-thing principle: If you'd choose the same thing whether or not an event occurs, knowing it shouldn't change your choice.
Unit bias: We treat one unit — one plate, one serving — as the right amount to consume.
Value function: The S-shaped curve that maps gains and losses onto felt value, kinked at the reference point.
Zero-risk bias: Craving the complete elimination of one risk over a larger reduction in overall risk.

Cognition & Dual-Process

Absolute threshold: The faintest stimulus a person can detect at all.
Abstract versus concrete construal: Seeing the gist and purpose versus the details and mechanics of the same thing.
Agreeableness: The trait of warmth, trust, cooperation, and concern for others.
Analogical reasoning: Solving a new problem by mapping it onto a familiar one with the same structure.
Analytic versus intuitive cognition: Slow, rule-based deliberation set against fast, holistic gut response.
Anterior cingulate cortex: The brain's monitor for conflict, error, and the need for control.
Apophenia: Seeing meaningful patterns or connections in random noise.
Attention: The scarce spotlight that selects what we process.
Attentional bias: Recurring concerns steer what we notice.
Attitude polarization: The same balanced evidence pushes opposing camps further apart, not closer together.
Base rate: The background frequency of a category, before any case-specific evidence.
Bayesian updating: Rationally revising your confidence in a belief as new evidence comes in.
Belief bias: We judge an argument valid if we agree with its conclusion.
Belief perseverance: Beliefs survive even after the evidence that created them is discredited.
Big Five: The five broad dimensions that organize most of human personality.
Bounded rationality: We're rational within the limits of mind, information, and time.
Categorization: Sorting the endless particulars of experience into a manageable set of kinds.
Choice blindness: We'll defend a choice we never actually made.
Chronotype: Whether you're naturally a morning lark or a night owl.
Classical conditioning: A neutral cue, paired with a stimulus, comes to trigger the response.
Cognitive decoupling: Holding a thought 'offline' to reason about hypotheticals without believing them.
Cognitive load: The mind has limited working capacity; overload degrades thinking.
Cognitive miser: The mind conserves effort, defaulting to cheap shortcuts.
Cognitive reflection test: A short test of overriding a wrong gut answer.
Cognitive reserve: The mental buffer that lets some brains withstand more damage before decline.
Cognitive style: A person's characteristic way of perceiving, thinking, and processing information.
Color constancy: A banana looks yellow at noon and at dusk, even though the light hitting it is utterly different.
Complacency: When things feel safe or automated, vigilance quietly erodes and warning signs get missed.
Conceptual metaphor: We think about abstract things by mapping them onto concrete, bodily ones.
Conditional reasoning: Inference from 'if...then' statements, where two moves are valid and two are tempting fallacies.
Confabulation: Spontaneously inventing a coherent reason for behavior we cannot truly explain.
Conjunction reasoning: Inference about 'and' — combining conditions, which can only narrow the possibilities.
Conscientiousness: The trait of being organized, dependable, disciplined, and achievement-driven.
Context effect: The same price, letter, or face reads differently depending on what surrounds it.
Contrast effect: A thing seems better or worse depending on what it's set against.
Convergent thinking: Narrowing many possibilities to the single best or correct answer.
Counterfactual thinking: Imagining 'what might have been' by mentally undoing what actually happened.
Crystallized intelligence: The store of knowledge and skills you've accumulated over a lifetime.
Cue: The trigger that automatically launches a habit, like a starting gun for behavior.
Default mode network: The brain network that lights up when the mind turns inward.
Disconfirmation: Satisfaction comes from how reality compares with what you expected, not from reality alone.
Disjunction reasoning: Inference about 'or' — which people find harder and often under-explore.
Divergent thinking: Generating many varied possibilities from a single starting point.
Dopamine reward prediction error: Dopamine signals the gap between expected and actual reward.
Dual-process theory: The mind runs on two systems: fast intuition and slow reasoning.
Dual-system neuroscience: The brain basis for fast emotional choice versus slow deliberate control.
Ego depletion neuroscience: The contested brain and metabolic story behind willpower running low.
Einstellung effect: A known solution blinds us to a simpler one staring us in the face.
Embodied cognition: Thinking is shaped by the body—our posture, movements, and physical sensations color thought.
Exemplar theory: We categorize by comparing a new case to specific remembered instances.
Experiencing versus remembering self: The self that lives through a moment and the self that later recalls it often disagree.
Extraversion: The trait of sociability, assertiveness, energy, and reward sensitivity.
Fluid intelligence: On-the-spot reasoning power, independent of acquired knowledge.
Framing of logic: Logically identical problems get solved or flubbed depending on how they are dressed.
Functional fixedness: Being unable to use an object in any way but its familiar one.
Functional opacity of cognition: We have no direct access to how our judgments are actually produced.
G.I. Joe fallacy: Thinking that just knowing about a bias is enough to overcome it.
General intelligence: The common factor underlying performance across diverse mental tasks.
Gestalt principles: Rules by which the mind organizes parts into coherent wholes.
Gist versus verbatim representation: We store the fuzzy meaning and the exact detail separately — and lean on the gist.
Graph literacy: The skill of reading and reasoning with data displayed visually.
Heuristic: A mental rule of thumb that makes judgment fast and frugal.
Heuristics and aging: How older adults' reliance on shortcuts shifts as cognition changes with age.
Illusion of explanatory depth: We think we understand how things work far better than we actually do.
Illusory truth effect: A statement feels truer simply because we have heard it before.
Impulsivity: The tendency to act quickly on urges without forethought.
Inattentional blindness: We fail to see a fully visible but unexpected object when attention is elsewhere.
Incubation: Stepping away from a stuck problem lets the solution surface later.
Information avoidance: Deliberately choosing not to learn something, even when the knowledge is free and useful.
Inside view: Judging a case from its own specifics versus judging it from the track record of similar cases.
Insight problem solving: Solutions that arrive suddenly, with an 'aha,' after a stuck impasse.
Intuition: Knowing without knowing how — a fast judgment whose reasons stay hidden.
Just-noticeable difference: The smallest change in a stimulus a person can reliably detect.
Matching bias: We gravitate to the items explicitly named in a rule, ignoring logical relevance.
McGurk effect: What you see a mouth do changes what you hear it say.
Mental model: An internal working scale-model of how some piece of the world behaves.
Mental simulation: Running an imagined scenario forward in the mind to see how it plays out.
Metacognition: Thinking about, monitoring, and regulating your own thinking.
Mindware: The learned rules and concepts that good reasoning depends on having installed.
Motivated reasoning: We reason toward the conclusion we want, not the one the evidence supports.
Müller-Lyer illusion: Two equal lines look unequal because of the arrowheads on their ends.
Multisensory integration: The brain fuses sight, sound, and touch into a single coherent perception.
Naïve realism: The conviction that we see reality objectively, so anyone who disagrees must be biased.
Neuroticism: The trait of proneness to anxiety, moodiness, and negative emotion.
Next-in-line effect: You barely remember what was said just before your own turn to speak.
Norm theory: We judge each event against the alternatives it spontaneously evokes.
Numeracy: The ability to understand and reason with numbers and probabilities.
Openness to experience: The trait of intellectual curiosity, imagination, and appetite for novelty.
Operant conditioning: Behavior is shaped by its consequences — reinforcement strengthens it, punishment weakens it.
Overthinking: Deliberating so much that thought clouds judgment or stalls action entirely.
Perceptual constancy: Objects look stable even as their retinal image changes.
Perceptual fluency: The ease of merely seeing or hearing a stimulus, which feels like familiarity or truth.
Perceptual set: Expectations and context steer what we end up perceiving.
Person-situation debate: The long argument over whether traits or situations drive behavior.
Pragmatic reasoning schemas: We reason with learned rule-packages about permissions and obligations, not bare logic.
Predictive coding: The brain perceives by predicting the world and correcting only its errors.
Prefrontal cortex: The brain's control center for planning, self-control, and deliberate choice.
Processing fluency: Information that is easy to process feels truer, safer, more familiar, and more likable.
Prototype theory: We represent a category by its average, idealized 'best example.'
Psychophysics: The science relating physical stimuli to the sensations they produce.
Reflective versus algorithmic mind: The disposition to engage reasoning, distinct from the raw capacity to do it.
Reinforcement: Any consequence that makes the behavior it follows more likely to happen again.
Retrieval fluency: The felt ease of pulling something from memory, mistaken for its truth or frequency.
Rhyme-as-reason effect: Statements that rhyme seem more truthful and persuasive than ones that do not.
Satisficing: Choosing the first option that is good enough rather than searching for the best.
Scarcity (cognitive): Not having enough captures the mind, taxing attention and self-control.
Script: A schema for an event: the standard sequence of actions a familiar situation follows.
Selective exposure: We seek out information that agrees with us and avoid what challenges us.
Selective perception: We notice, interpret, and remember what fits our expectations and interests, filtering out the rest.
Sensation seeking: The craving for novel, intense, and risky experiences.
Spreading activation: Thinking of one concept automatically primes the ones linked to it.
System 1 / System 2: Shorthand for the fast, automatic mind versus the slow, effortful one.
Temperament: The biologically based emotional and behavioral style present from infancy.
Theory of mind: The capacity to attribute mental states — beliefs, desires, intentions — to others and to oneself.
Tolerance of ambiguity: How comfortably a person handles vague, uncertain, or contradictory situations.
Top-down processing: Perception guided by knowledge and expectation, not just raw input.
Trait activation: Traits show up in behavior only when the situation calls them out.
Trait vs state: The difference between how you usually are and how you feel right now.
Tunneling: Scarcity narrows the mind to the pressing problem, blinding it to everything outside the tunnel.
Type 1 versus type 2 processing: The defining contrast is autonomy versus working-memory-demanding decoupling.
Variable reward: Rewards delivered unpredictably are far more compelling and habit-forming than predictable ones.
Ventral striatum: The brain's reward hub where value and anticipation are computed.
Wason selection task: A four-card logic puzzle most people fail — until it is framed as cheating.
Weber–Fechner law: Bigger baseline stimuli need proportionally bigger changes to be noticed.
Working memory: The small mental workspace that holds and manipulates information in the moment.
Zeigarnik effect: Unfinished tasks nag at memory more than completed ones.

Emotion & Affect

Achievement emotions: The emotions we feel about learning and performance — pride, anxiety, boredom — depend on how much control and value we perceive.
Affect heuristic: We judge risks and benefits by how we feel about them.
Affect labeling: Putting a feeling into words tends to take some of its sting out.
Affect-as-information: We read our momentary feelings as data about the world or the question at hand.
Affective empathy: Catching and feeling what another person feels.
Affective forecasting: Predicting how future events will make us feel — usually badly.
Affective neuroscience: The study of how the brain generates and regulates emotion.
Alexithymia: Difficulty identifying and putting words to one's own emotions.
Ambivalence: Holding strong positive and negative feelings about the same thing at once.
Amygdala: The brain's rapid detector of threat and emotional salience.
Anticipated emotion: A cold-headed prediction of how a future outcome will make you feel.
Anticipated regret: We choose to avoid the regret we expect to feel.
Anticipatory emotion: The feelings you have now about an uncertain future event.
Appraisal tendency framework: Each emotion biases judgment in its own predictable direction.
Appraisal theory of emotion: Emotions arise from how we interpret a situation, not the situation itself.
Arousal: The body's overall level of activation, from drowsy calm to keyed-up alertness.
Awe: The feeling of vastness that makes the self shrink and the mind expand.
Basic emotions: A small set of innate, universal emotions with distinct signatures.
Behavioral immune system: A first line of defense that uses disgust and avoidance to keep pathogens at arm's length.
Behavioral inhibition: The brake system that halts action in the face of threat or conflict.
Botox emotion effect: Paralyzing the frown muscles with Botox dampens the feelings those muscles help produce.
Broaden-and-build theory: Positive emotions widen thinking and build lasting resources.
Cannon-Bard theory: The feeling and the bodily reaction fire at the same time, independently.
Cognitive empathy: Understanding what another feels without necessarily feeling it.
Compassion: Being moved by another's suffering and wanting to relieve it.
Compassion fade: Caring drops as the number of victims rises.
Compassion fatigue: The emotional exhaustion of those who care for the suffering too long.
Constructed emotion: Emotions are built by the brain, not triggered as fixed reactions.
Contempt: A cold sense of looking down on someone as beneath one's regard.
Core affect: The ever-present background feeling, mapped by pleasantness and energy.
Disgust sensitivity: How easily and strongly a person is revolted varies and shapes judgment.
Display rules: Learned social conventions about which emotions you may show, to whom, and when.
Distraction: Steering attention away from a feeling to turn down its volume.
Dual-factor model of affect: Good moods and bad moods are two separate dials, not one slider.
Durability bias: We predict our feelings will last far longer than they actually do.
Embarrassment: The flustered discomfort of a social slip in front of others.
Emotion regulation: The strategies we use to influence which emotions we feel and how.
Emotional contagion: Feelings spread from person to person, often without anyone noticing.
Emotional granularity: How finely a person distinguishes among their emotional states.
Emotional intelligence: The ability to perceive, use, understand, and manage emotions.
Emotional labor: The effort of managing your feelings—and faking the right ones—because the job demands it.
Empathy: Sharing in and understanding the feelings of another person.
Envy: The painful longing stirred by what someone else has.
Eudaimonia vs hedonia: Well-being from meaning and growth versus well-being from pleasure.
Excitation transfer: Arousal left over from one event spills over to intensify the next.
Expressive suppression: Hiding the outward signs of an emotion while still feeling it inside.
Facial feedback hypothesis: Your facial expression doesn't just show emotion, it shapes it.
Glückschmerz: The flash of displeasure at someone else's good fortune.
Gratitude: The warm appreciation felt when someone benefits you.
Guilt: The self-conscious pang over a specific wrong you've done.
Hedonic adaptation: We drift back toward a stable happiness baseline after good or bad events.
Hedonic contingency: Happy people screen activities for whether they'll keep the mood going.
Hubris: Excessive, overbearing pride and self-confidence that courts a fall.
Humiliation: The crushing sense of being unjustly degraded and put down in front of others.
Identifiability effect: A determinate, identified target draws more concern than an abstract one.
Impact bias: Overestimating how intensely and how long future events will move us.
Incidental affect: A leftover feeling from one source that bleeds into an unrelated decision.
Integral affect: The feeling that comes directly from the thing you're deciding about.
Interoception: The sense of the body's internal state that feelings are built on.
James-Lange theory: We feel afraid because we tremble, not the other way around.
Jealousy: The fear and anguish of losing a valued relationship to a rival.
Life satisfaction: A reflective, overall judgment of how well your life is going.
Mere exposure effect: We come to like things simply because we have encountered them before.
Misattribution of arousal: We mislabel the source of our physical arousal, pinning it on the wrong cause.
Mood congruence: Our current mood colors what we remember and how we judge.
Mood maintenance hypothesis: People in a good mood avoid risks and effort that might spoil it.
Mood repair: Actively doing things to lift yourself out of a bad mood.
Moral disgust: The visceral revulsion of physical disgust, recruited to condemn moral wrongs.
Moral elevation: The warm, uplifted feeling of witnessing moral beauty.
Moral emotions: Feelings tied to the interests or welfare of others or society.
Mortality salience: Being reminded that you will die changes what you value and defend.
Negativity bias: Bad is psychologically stronger than good.
Nostalgia: A bittersweet longing for a cherished personal past.
Ostrich effect: We avoid information we expect to be unpleasant by simply not looking.
Personal distress: The self-focused anxiety stirred up by another's suffering.
Pessimism bias: Expecting outcomes to turn out worse than the odds actually warrant.
Pity: Feeling sorrow for another's suffering, from a position of distance and relative comfort.
Positivity offset: At zero input, we lean mildly positive, which keeps us exploring.
Pride: The glow of achievement, in healthy and arrogant varieties.
Psychic numbing: The more who suffer, the less we are able to feel.
Psychophysical numbing: Each additional life saved feels less valuable as the numbers grow.
Reappraisal: Changing how you think about a situation to change how it feels.
Resilience: The capacity to adapt and bounce back from adversity.
Risk as feelings: Emotional reactions to risk often diverge from, and override, cool calculation.
Rumination: Brooding repetitively on distress and its causes without moving toward a solution.
Schadenfreude: The guilty pleasure of taking joy in another's misfortune.
Scope insensitivity: Our feelings and willingness to pay barely scale with the size of a problem.
Self-transcendent emotions: Feelings that pull attention beyond the self toward others and something larger.
Set-point theory of happiness: Each person has a baseline happiness they keep returning to.
Shame: The painful sense that one's whole self is flawed or exposed.
Somatic marker hypothesis: Bodily 'gut feelings' tag options with value and are necessary for good decisions.
Subjective well-being: How people evaluate and feel about their own lives.
Sympathy: Feeling concern for another's plight without sharing the feeling itself.
Two-factor theory of emotion: Emotion equals physiological arousal plus a label drawn from the situation.

Heuristics & Biases

Action bias: The pull to do something rather than wait, even when waiting is better.
Anchoring: The first number you see drags every estimate that follows toward it.
Anchoring (negotiation): Whoever names a number first usually shapes the deal.
Attribute substitution: Answering an easier question than the one actually asked.
Automation bias: We over-trust the computer's answer and stop checking for ourselves.
Availability cascade: A belief snowballs as repetition makes it feel true and dissent grows costly.
Availability heuristic: If examples come to mind easily, we assume they're common.
Base rate neglect: We fixate on specific detail and forget the underlying odds.
Basic anchoring effect: An irrelevant number you weren't even comparing can still bias your estimate.
Bias blind spot: We spot bias in everyone but ourselves.
Clustering illusion: Finding patterns and streaks in genuinely random data.
Compatibility principle: An attribute counts more when it matches the form of the response.
Confirmation bias: We seek, notice, and remember what fits what we already believe.
Congruence bias: Testing only your favored hypothesis, never the alternative.
Conjunction fallacy: A vivid, specific story can seem likelier than the plain fact it contains.
Conservatism (belief revision): Given new data, we update our probabilities, but not far enough.
Conservatism bias: Updating beliefs too little when new evidence arrives.
Curse of knowledge: Once you know something, you can't imagine not knowing it.
Denominator neglect: We fixate on the number of cases and overlook the size of the pool.
Dilution effect: Adding irrelevant facts to relevant ones weakens, rather than sharpens, a judgment.
Disconfirmation bias: We scrutinize evidence against our beliefs far harder than evidence that flatters them.
Dunning–Kruger effect: The less skill we have, the more we overrate it.
Extension neglect: Judging a set by a typical member, not by how many members it has.
Fast-and-frugal heuristics: Simple rules that use little information yet often decide as well as complex models.
Fast-and-frugal trees: A short decision tree with an exit at every question, for quick high-stakes calls.
Fluency heuristic: When both options are familiar, trust the one that comes to mind faster.
Focusing illusion: Whatever you're thinking about feels more important to your happiness than it really is.
Fundamental attribution error: Blaming people's character while excusing the situation.
Gambler's fallacy: Believing that after a run of one outcome, the opposite has become 'due.'
Gaze heuristic: To catch a ball, fix your gaze on it and move so the angle stays constant.
Halo effect: One salient good trait makes us assume all the unrelated ones are good too.
Hindsight bias: Once we know how it turned out, we feel we saw it coming all along.
Hot-hand fallacy: Reading a meaningful, self-sustaining streak into what is really just chance.
Illusion of control: Overestimating how much our own actions sway outcomes that are really down to chance.
Illusory correlation: Seeing a relationship between two things that aren't actually linked.
Information bias: Seeking more information even when it can't change what you'll do.
Insensitivity to sample size: Ignoring that small samples swing far more wildly than large ones.
Law of small numbers: Wrongly expecting even tiny samples to mirror the whole population.
Less-is-more effect: Knowing or using less can sometimes yield more accurate decisions.
Neglect of probability: We weigh how bad an outcome would be while ignoring how likely it is.
Non-regressive prediction: Forecasting an extreme result from an extreme cue, ignoring the noise.
Normalcy bias: In a disaster, we assume things will stay normal and underreact.
Omission bias: We judge harm caused by doing something as worse than the same harm caused by doing nothing.
Optimism bias: We expect good things to befall us, and bad things to spare us, more than the odds allow.
Outcome bias: Judging a decision by how it turned out rather than by how sound it was when made.
Overconfidence effect: Our subjective certainty routinely outruns our actual accuracy.
Partition dependence: How the options are grouped sways the probabilities we assign them.
Planning fallacy: Plans are built on the best case, so projects run late and over budget with striking regularity.
Proportion dominance: A big percentage beats a big absolute number for grabbing our attention.
Pseudodiagnosticity: Gathering evidence that fits a hypothesis without checking the alternative.
Ratio bias: A 9-in-100 chance can feel bigger than a 1-in-10 chance.
Recognition heuristic: If you recognize one option but not the other, bet on the familiar one.
Representativeness heuristic: We judge how likely something is by how much it resembles our mental prototype, not by the actual odds.
Self-generated anchoring: Even the anchor you invent yourself drags your final answer toward it.
Self-serving bias: Success is my doing; failure is bad luck or someone else's fault.
Subadditivity effect: Spelling out the parts of an event makes it seem more likely than the whole.
Survivorship bias: Studying only the winners and missing the silent evidence of everyone who failed.
Take-the-best heuristic: Decide using the single best clue, and ignore everything else.
Tallying: Count the reasons for each option equally instead of weighting them.
Time-saving bias: We badly misjudge how much time a change in speed actually saves.
Unpacking effect: Breaking a possibility into named pieces raises its judged probability.

Memory & Perception

Associative memory: Knowledge stored as a web of linked ideas, where activating one pulls up its neighbors.
Autobiographical memory: The personal record of one's own life events and experiences.
Boundary extension: We remember having seen more of a scene than was actually shown.
Change blindness: We miss large changes to a scene when they happen out of focus.
Childhood amnesia: The near-absence of memories from our first few years of life.
Chunking: Grouping items into meaningful units to pack more into limited memory.
Context-dependent memory: We remember more when the surroundings at recall match those at learning.
Cryptomnesia: Mistaking a buried memory for an original idea of your own.
Cue-dependent forgetting: The memory is still there; you just lack the right cue to reach it.
Decay theory: Memories fade simply because time passes and traces weaken.
Desirable difficulty: Making learning harder in the right ways makes it last longer.
Dual coding theory: Information encoded as both words and images is remembered better.
Duration neglect: How long an experience lasts barely affects how we remember it.
Encoding specificity principle: You recall best when the cues at retrieval match those present when you learned.
Episodic memory: Memory for specific personal experiences, tied to a time and place.
Experiencing vs remembering self: The self living a moment and the self recalling it want different things.
Fading affect bias: The sting of bad memories fades faster than the glow of good ones.
False memory: Vividly remembering something that never happened.
Feeling of knowing: The sense that you could recognize an answer you currently can't recall.
Flashbulb memory: A vivid, confident memory of where you were when shocking news broke.
Forgetting curve: Newly learned information drops away fast at first, then levels off.
Generation effect: Information you produce yourself is remembered better than information you merely read.
Imagination inflation: Merely imagining an event makes you more confident it actually happened.
Interference theory: We forget because other memories compete with and crowd out the target.
Judgment of learning: Your on-the-spot prediction of how well you'll later remember something.
Leveling and sharpening: Retold memories lose some details and exaggerate others.
Levels-of-processing effect: The deeper the meaning you extract, the better you remember.
Metamemory: Your knowledge of, and ability to monitor and control, your own memory.
Method of loci: Remembering items by mentally placing them along a familiar route.
Miller's magical number seven: Immediate memory holds only about seven items at once.
Misinformation effect: Misleading information encountered after an event rewrites the memory of it.
Mnemonics: Deliberate tricks that impose structure to make material memorable.
Mood-congruent memory: A given mood makes you recall material whose emotional tone matches it.
Peak–end rule: We judge a past experience by its most intense moment and how it ended, not by its sum.
Picture superiority effect: We remember images far better than the equivalent words.
Primacy effect: First impressions and early items carry extra, lasting weight.
Proactive interference: Old learning gets in the way of remembering something new.
Reality monitoring: Telling apart memories of real events from memories of imagined ones.
Recency effect: The most recent items and events loom largest in memory and judgment.
Reconstructive memory: Remembering is rebuilding the past from fragments, not replaying a recording.
Reminiscence bump: We disproportionately recall events from our teens and twenties.
Retroactive interference: New learning crowds out and disrupts memory for older material.
Rosy retrospection: The past looks better in memory than it actually felt at the time.
Schema: A mental template of how things usually go that guides what we notice and recall.
Self-reference effect: Information tied to yourself is remembered far better.
Self-serving memory bias: Memory quietly edits the past to flatter the present self.
Semantic memory: Your store of general facts, concepts, and word meanings.
Semantic network: Knowledge stored as a web of concepts linked by meaningful associations.
Serial position effect: We remember the first and last items in a sequence best, and the middle worst.
Source confusion: Remembering a fact but misremembering where it came from.
Source-monitoring framework: How the mind decides where a given memory came from.
Spacing effect: Learning spread out over time produces far better retention than cramming.
State-dependent memory: What you learn in one internal state comes back best in that same state.
Suggestibility: The tendency for leading information to reshape what we remember.
Telescoping effect: We misremember when events happened, pulling recent ones forward and distant ones nearer.
Testing effect: Recalling information strengthens memory far more than rereading it.
Tip-of-the-tongue phenomenon: The maddening state of knowing a word but being unable to retrieve it.
Transfer-appropriate processing: Learning helps most when the mental work at study matches the work at test.
Von Restorff effect: The item that stands out from its neighbors is the one we remember.
Working-memory span: How much information you can actively hold and juggle at one time.

Methods & Evidence

A/B testing: An online randomized experiment comparing two versions to see which performs better.
Acquiescence bias: The tendency to agree with whatever a survey statement asserts.
Aggregation: Averaging many independent estimates often beats any single expert.
Attrition bias: When the people who quit a study differ from those who stay, results skew.
Average treatment effect: The average causal effect of a treatment across everyone in the population.
Back-door criterion: A graphical rule for which variables to adjust for to get a clean causal estimate.
Bayes factor: A ratio measuring how strongly the data favor one model over another.
Bayes' theorem: The formula for updating a belief in light of new evidence.
Bayesian inference: Treat unknowns as probability distributions and update them with data.
Berkson's paradox: Two unrelated traits look anticorrelated once you only study a selected group.
Bias–variance tradeoff: Simple models miss the pattern; complex ones chase the noise—the art is balancing the two.
Blinding: Hiding who got the treatment so expectations don't contaminate results.
Blocking: Grouping similar subjects before randomizing so nuisance differences don't muddy the comparison.
Bonferroni correction: Divide your significance threshold by the number of tests you run.
Bootstrapping: Estimating uncertainty by resampling your own data, over and over.
Brier score: A scorecard for probabilistic forecasts that rewards being both accurate and well-calibrated.
Calibration: Being right as often as you say you are.
Campbell's law: The more a social indicator is used to decide things, the more it gets corrupted.
Causal inference: The science of moving from 'these vary together' to 'this causes that.'
Ceiling and floor effects: When a measure tops out or bottoms out, it can't detect real differences.
Cohen's d: How far apart two groups are, measured in standard deviations.
Collider bias: Controlling for a shared effect of two variables can invent a fake correlation.
Common method bias: Spurious correlation that arises just because two things were measured the same way.
Confidence interval: A range of plausible values for a quantity, with a stated coverage rate.
Confounding: A hidden third variable that drives both the cause and the effect, faking a link.
Construct validity: Whether a measure actually captures the abstract thing it claims to.
Content validity: Whether a test's items actually cover the full concept it claims to measure.
Control group: The comparison arm that shows what happens without the intervention.
Convergent validity: Measures of the same construct should agree with one another.
Counterbalancing: Varying the order of conditions so sequence effects cancel out.
Counterfactual: What would have happened to the same unit under the road not taken.
Credible interval: A range that genuinely has, say, a 95% probability of holding the true value.
Cronbach's alpha: A number summarizing how consistently a scale's items hang together.
Cross-validation: Testing a model on data it wasn't trained on to see if it really generalizes.
Demand characteristics: Participants guess the study's aim and act to fit it.
Difference-in-differences: Compare the change in a treated group to the change in an untreated one.
Directed acyclic graph: A diagram of arrows that encodes which variables cause which.
Discriminant validity: A measure should not correlate with things it's supposed to be distinct from.
Double-blind: Neither the participant nor the experimenter knows who's in which group.
Ecological fallacy: Inferring about individuals from group-level averages — and getting it wrong.
Ecological validity: Whether the study resembles the real situation it's about.
Effect size: How big an effect is — not just whether it exists.
Equivalence testing: Formally testing that an effect is too small to matter, not just absent.
Experimenter bias: A researcher's hopes can leak into a study and quietly nudge the results their way.
External validity: Whether findings generalize beyond the study.
Factor analysis: A statistical method that distills many correlated measures into a few underlying dimensions.
False discovery rate: The expected share of your 'significant' findings that are actually false.
Field experiment: A randomized trial run in the real world, not the lab.
Fixed effects: A modeling trick that controls away everything stable about each unit to isolate real change.
Forest plot: A stacked chart showing each study's effect and the pooled summary.
Frequentist inference: Probability as long-run frequency, with no probabilities attached to hypotheses.
Funnel plot: A scatter of studies whose lopsided shape hints at missing results.
Garden of forking paths: Even one analysis can be biased if you'd have chosen differently on other data.
Generalizability: Whether a study's findings hold beyond the specific people, place, and setting tested.
Goodhart's law: When a measure becomes a target, it stops being a good measure.
HARKing: Hypothesizing After the Results are Known, then pretending you predicted it.
Hawthorne effect: People change their behavior simply because they know they're being observed.
Heritability: The share of trait differences in a population traceable to genetic differences.
Heterogeneity: When studies of the same question genuinely disagree in their results.
Hypothesis testing: The formal procedure for deciding whether data are surprising enough to reject a default assumption.
Instrumental variables: Use an outside nudge that affects the cause but nothing else to untangle causation.
Intention-to-treat analysis: Analyze everyone in the group they were assigned to, regardless of compliance.
Inter-rater reliability: Whether independent judges score the same thing the same way.
Internal validity: Whether a study really shows that the cause it claims produced the effect.
Latin square: A design layout that balances treatment order so practice and fatigue can't bias results.
Leading question: A question worded to nudge the respondent toward a particular answer.
Likelihood ratio: How much more probable the evidence is under one hypothesis than another.
Local average treatment effect: The causal effect estimated only for those whose behavior responds to the nudge or instrument.
Measurement error: The gap between what you measure and the true value you meant to capture.
Mediation: The mechanism in between — how a cause produces its effect.
Megastudy: A massive field experiment that tests many interventions against the same outcome in one population at once.
Meta-analysis: Statistically pooling many studies into one overall estimate.
Moderation: When the strength or direction of an effect depends on a third variable.
Multiple comparisons problem: Run enough tests and some will look significant by pure chance.
Multiverse analysis: Run every reasonable version of an analysis and report the whole spread.
Natural experiment: An accident of the world that mimics random assignment when a true experiment is impossible.
Natural frequencies: Stating risks as counts of people, not percentages, makes the math click.
Non-response bias: When the people who don't answer differ from those who do, the sample lies.
Nudge unit: A government or organizational team that designs, applies, and rigorously tests nudges.
Null hypothesis significance testing: The ritual of testing data against a 'no effect' hypothesis via p-values.
Omitted variable bias: Leaving a relevant cause out of a regression warps the coefficients you keep.
Optional stopping: Repeatedly checking results and stopping when they turn significant inflates errors.
Order effects: The sequence of questions or conditions can change the answers people give.
Overfitting: A model that memorizes noise in the data instead of the real pattern.
p-curve: The shape of a set of significant p-values reveals whether real effects underlie them.
p-hacking: Tweaking analyses until a result crosses the significance threshold.
Parallel trends: The key bet behind difference-in-differences: absent treatment, the groups would have moved together.
Placebo effect: Belief in a treatment produces a real, measurable improvement.
Posterior probability: Your updated belief about a hypothesis after weighing the evidence.
Power analysis: Planning sample size to give a study a real chance of finding a true effect.
Practical significance: Whether an effect is big enough to matter in the real world, not just statistically detectable.
Pre-mortem: Imagining a project has already failed, then working backward to expose the risks before they happen.
Pre-registration: Committing publicly to your hypotheses and analysis plan before seeing the data.
Prior probability: What you believed about a hypothesis before seeing the new data.
Propensity score matching: Pair treated and untreated units with the same predicted chance of treatment.
Pseudo-opinion: People will confidently give an opinion on something entirely made up.
Publication bias: Positive, novel results get published while null results are quietly buried.
Random-effects model: Treating groups or studies as draws from a wider population rather than as fixed.
Randomization: Letting chance decide who gets the treatment, so groups start out comparable.
Randomized controlled trial: The gold standard for causal evidence: randomly assign people to treatment or control.
Rank-ordering: Asking people to put options in order rather than score each one separately.
Reference class forecasting: Predicting a project's outcome from the track record of similar past projects rather than from its own details.
Registered report: A study peer-reviewed and accepted before any data are collected.
Regression analysis: Modeling how an outcome changes with one or more predictors.
Regression discontinuity design: Compare units just above and just below a sharp cutoff for treatment.
Regression to the mean: Extreme measurements tend to be followed by more average ones, purely by chance.
Reliability: Whether a measure gives consistent results across items, raters, and occasions.
Replication: Repeating a study to see whether its finding holds up.
Replication crisis: A large share of published findings fail to reproduce when independently repeated.
Researcher degrees of freedom: The many small analytic choices that quietly let you find what you want.
Response bias: Systematic tendencies in how people answer that distort what surveys actually measure.
Reverse causation: The arrow runs the other way — the supposed effect is really the cause.
Risk of bias: The chance that flaws in a study's design or conduct have skewed its results.
Robustness check: Re-running an analysis under different assumptions to test if the result survives.
Sampling bias: Your sample systematically over- or under-represents parts of the population.
Scalability: Whether an intervention that worked in a study still works when rolled out at scale.
Selection bias: Who ends up in your sample is tied to the very thing you're measuring.
Signal detection theory: Separating true sensitivity from the bias to say 'yes.'
Simpson's paradox: A trend in every subgroup can vanish or flip when the groups are combined.
Smallest effect size of interest: The smallest effect big enough to actually care about — set before you look.
Social desirability bias: People answer to look good, not to tell the truth.
Standard error: How much an estimate would bounce around across repeated samples.
Statistical control: Holding other variables constant in analysis to isolate a relationship.
Statistical power: A study's ability to detect a real effect when one genuinely exists.
Statistical significance: How surprising the data would be if there were truly no effect.
Subjective probability: Probability as a personal degree of belief, not a long-run frequency.
Surrogate outcome: A stand-in marker used instead of the outcome you actually care about.
Systematic review: A rigorous, reproducible survey of all the evidence on a question.
Test-retest reliability: Whether the same people get the same scores when measured again later.
Type I error: Crying wolf — declaring an effect that isn't really there.
Type II error: Missing a real effect — failing to detect what's actually there.
Value of information: How much it is worth to learn something before you decide.
WEIRD samples: Most behavioral findings come from a narrow, globally unrepresentative slice of humanity.
Within-subjects design: Every participant experiences every condition, serving as their own control.

Models & Frameworks

Attribution theory: The study of how people explain the causes of behavior and events.
Behavioral audit: A systematic review of a product, service, or policy to find behavioral barriers and opportunities for improvement.
Behavioral diagnosis: Pinpointing exactly which behavior, by whom, and which barriers drive a problem before designing any solution.
Behavioral insights: The applied use of behavioral and social science to design policies, products, and services that fit how people really act.
Behavioral journey mapping: Charting every step a person takes toward a goal to find the moments where behavior stalls and intervention can help.
Behavioral segmentation: Dividing a population by their behaviors, motivations, and barriers so interventions can be tailored to each group.
Behavioral spillover: When one behavior change spreads to other related behaviors — sometimes reinforcing, sometimes undermining the goal.
Behavioral systems mapping: Diagramming the web of actors, behaviors, and influences around a problem to find high-leverage points for change.
Behaviour change technique taxonomy: A shared vocabulary of 93 discrete techniques for changing behavior.
Behaviour change wheel: A systematic method to design interventions, built around COM-B.
Capability approach: A welfare framework judging well-being by what people are actually able to do and be, not by income or resources alone.
COM-B model: Behavior happens when Capability, Opportunity, and Motivation align.
Covariation model: We decide a cause by checking what the effect reliably varies with.
Diffusion of innovations: How a new idea, product, or behavior spreads through a population over time, from a few innovators to the last laggards.
EAST framework: To change behavior, make it Easy, Attractive, Social, and Timely.
Ecological rationality: A heuristic is 'rational' if it fits the structure of its environment.
Elaboration likelihood model: Persuasion travels two routes: central (argument) and peripheral (cues).
Falsifiability: A claim is scientific only if some possible observation could prove it wrong.
Fogg behavior model: Behavior happens when Motivation, Ability, and a Prompt converge at once.
Goal systems theory: Goals and the means to reach them form a connected mental network, where one action can serve many goals and one goal many actions.
Habit formation: The process by which repeated behavior in a stable context becomes automatic, triggered by cues rather than decisions.
Habit loop: Habits run on a loop: a cue triggers a routine that delivers a reward.
Health action process approach: A health-behavior model that splits change into a motivation phase and a volition phase, bridging the gap between intention and action.
Health belief model: We act on our health when we feel at risk and believe that acting will help.
Heuristic-systematic model: We process persuasive messages either carefully (systematic) or via shortcuts (heuristic).
i-frame vs s-frame: The choice between fixing problems at the individual level (nudges) versus the systemic level (rules, prices, structures).
Implementation science: The study of how to get proven interventions actually adopted, delivered, and sustained in real-world settings.
Information–motivation–behavioral skills model: Behavior change requires accurate information, the motivation to act, and the concrete skills to carry it out.
Intervention ladder: A scale of policy options ranked from least to most intrusive on liberty.
Intervention mapping: A six-step protocol for designing behavior-change programs grounded in theory, evidence, and stakeholder input.
Levels of analysis: The same behavior can be explained at several layers—from neurons to evolution—each a valid lens.
Logic model: A one-page diagram linking a program's inputs and activities to its outputs, outcomes, and impact.
MINDSPACE: Nine of the strongest, mostly automatic influences on behavior, as a checklist.
Motivated tactician: We think carefully or lazily depending on our goals of the moment.
Naïve scientist: The early model of people as rational, logical causal reasoners.
Normalization of deviance: Rule-breaking that goes unpunished quietly becomes the new standard, until it fails.
Normalization process theory: A sociological account of how a new practice becomes embedded as routine, everyday work rather than a temporary project.
PERMA model: Five measurable building blocks of human flourishing.
Precaution adoption process model: A stage model of taking up a precaution that starts before awareness and includes a distinct 'decided not to act' dead end.
PRIME theory: A synthesis of motivation in which moment-to-moment behavior is governed by plans, responses, impulses, motives, and evaluations.
Protection motivation theory: We are moved to protect ourselves when a threat feels serious and likely and we believe a response will work and we can do it.
Rationality: The standard of reasoning and choosing well — and the benchmark biases are measured against.
RE-AIM framework: A checklist for judging an intervention's real-world public-health impact across five dimensions, not just whether it works in a trial.
Realistic conflict theory: Competition over scarce resources breeds intergroup hostility.
Reasoned action approach: An updated synthesis of reasoned-action and planned-behavior theory: intention drives behavior, fed by attitudes, norms, and perceived control.
Self-categorization theory: We shift between seeing ourselves as 'I' and as 'we.'
Self-regulation theory: We steer our own behavior by comparing where we are to a goal and acting to close the gap, like a thermostat.
Six sources of influence: A change framework that crosses motivation and ability with personal, social, and structural levels to give six distinct levers.
Social cognitive theory: We learn behavior by observing others, with self-efficacy deciding whether learning becomes action.
Social identity theory: Part of who we are comes from the groups we belong to.
Support theory: Probability judgments attach to descriptions of events, not the events themselves.
Theoretical domains framework: Fourteen domains that together capture every psychological and environmental influence on a behavior.
Theory of change: An explicit map of how and why a set of activities is expected to produce a desired long-term outcome.
Theory of planned behaviour: Intentions — shaped by attitudes, social norms, and perceived control — predict behavior.
Theory of reasoned action: Behavior follows from intention, which is set by attitudes and subjective norms.
Tiny habits: A method for building habits by starting absurdly small, anchoring to an existing routine, and celebrating immediately.
Translational gap: The chronic gulf between what research shows works and what actually gets used in policy and practice.
Transtheoretical model: Behavior change unfolds through stages, from not-yet-ready to maintaining the new behavior.
Uncertainty: Not knowing what will happen — sometimes with known odds, sometimes without any.
Voltage effect: The tendency for an idea's impact to shrink — or sometimes grow — when it moves from a small pilot to large-scale rollout.
Wise intervention: A brief, precisely targeted change to how people interpret themselves or a situation that can yield large, lasting effects.

Motivation & the Self

Achievement goal theory: Why you pursue success — to truly master something or to look competent to others — shapes how you respond to difficulty.
Achievement motive versus fear of failure: Achievement behavior reflects a tug-of-war between the hope of succeeding and the fear of failing.
Approach-avoidance conflict: The tension of wanting and dreading the same goal, which pulls you toward it from afar and pushes you back up close.
Approach-avoidance motivation: Behavior is energized either by moving toward what's good or by moving away from what's bad — and the two systems differ.
Autonomy: The need to feel one's actions are self-endorsed and freely chosen.
Basic psychological needs: Autonomy, competence, and relatedness are the nutrients all motivation and well-being depend on.
Cognitive dissonance: The discomfort of holding conflicting beliefs drives us to resolve it.
Collective efficacy: A group's shared belief in its joint capability to organize and execute the actions needed to succeed.
Competence: The need to feel effective and to master challenges.
Curiosity: The drive to seek out novelty and knowledge, often sparked by an awareness of what we don't yet know.
Defensive pessimism: Bracing for the worst as a strategy to actually perform better.
Drive reduction theory: Unmet biological needs create tension that motivates behavior aimed at restoring internal balance.
Endowed progress effect: Giving people a head start toward a goal makes them try harder to finish it.
Equity theory: We judge fairness by comparing our effort-to-reward ratio against other people's, and feel driven to correct any imbalance.
ERG theory: A leaner revision of Maslow that collapses needs into three and lets people pursue them in any order.
Expectancy theory: We work hard only when effort seems to lead to performance, performance to reward, and the reward is something we actually want.
Expectancy-value theory: Motivation is the product of how likely you think success is and how much you value it.
Extrinsic motivation: Acting for a separable outcome — pay, grades, praise, avoiding punishment.
Flow: Total, energized absorption in a well-matched challenge.
Forbidden-fruit effect: Telling people they can't have something makes them want it more.
Goal contagion: Merely observing someone pursue a goal can make you unconsciously adopt and pursue that goal yourself.
Goal-setting theory: Specific, challenging goals reliably drive higher performance than vague ones.
Grit: Sustained passion and perseverance toward very long-term goals, beyond mere short-term effort.
Growth mindset: Believing ability can be developed through effort, not fixed at birth.
Implicit theories of intelligence: Whether you believe ability is fixed or improvable quietly shapes how you handle challenge and failure.
Intrinsic motivation: Doing something for its own sake — out of interest, enjoyment, or meaning.
Intrinsic versus extrinsic goals: What you aim for in life — growth and connection versus wealth and image — predicts your well-being.
Job characteristics model: Five features of a job determine how motivating it feels, by triggering psychological states like meaningfulness and responsibility.
Learned helplessness: After enough uncontrollable failure, people and animals stop trying even when escape becomes possible.
Learned industriousness: When effort itself has been rewarded, the sensation of working hard becomes less aversive and even reinforcing.
Locus of control: Whether you see your outcomes as driven by your own actions or by outside forces.
Maslow's hierarchy of needs: Human needs stack in a pyramid, from basic survival up to self-fulfillment, with lower needs claiming priority.
Mastery versus performance goals: Aiming to get better at something behaves very differently from aiming to prove you're good at it.
Meaning in life: The sense that one's life makes sense, has direction, and matters.
Means-efficacy: Belief in the tools, resources, or methods at your disposal — the complement to believing in yourself.
Mindset of abundance versus scarcity: Feeling that a vital resource is in short supply captures the mind and reshapes how we think and choose.
Moral licensing: Doing one good deed gives us license to follow it with a bad one.
Motivation crowding: External incentives can displace internal or moral motives.
Need for achievement: A stable drive to meet high standards, master challenges, and accomplish difficult things for the satisfaction of doing so.
Need for affiliation: A drive to form and maintain warm, friendly relationships and to feel accepted by others.
Need for closure: A desire for a firm answer to a question — any definite answer — rather than confusion and ambiguity.
Need for cognition: A stable individual difference in how much a person enjoys and seeks out effortful thinking.
Need for power: A drive to have impact, influence, or control over other people and one's environment.
Need to belong: A fundamental human drive to form and maintain lasting, caring relationships.
Optimism (dispositional): The stable trait of generally expecting good things to happen.
Overjustification effect: Paying people for something they already loved can crowd out the love.
Possible selves: The future selves we hope to become, expect to become, or fear becoming — and how they pull behavior now.
Possible selves theory of procrastination: The less connected you feel to your future self, the more readily you sacrifice that stranger's interests for present comfort.
Psychological ownership: The feeling that something is 'mine' — even without legal title — and the investment and care that feeling brings.
Psychological reactance: Pressure to comply can trigger the urge to do the very opposite to reassert one's freedom.
Regulatory fit: Motivation and persuasion feel stronger when the way you pursue a goal matches your underlying orientation.
Regulatory focus theory: We pursue goals either to achieve gains (promotion) or to avoid losses (prevention), and messages that fit feel more persuasive.
Regulatory mode: Whether you're driven to get moving or to get it right.
Relatedness: The basic need to feel connected to, and cared for by, other people.
Reward sensitivity: How strongly cues of reward energize a person's pursuit and approach.
Self-actualization: The drive to realize one's full potential and become everything one is capable of becoming.
Self-affirmation theory: Affirming a valued part of the self lets us face threatening truths.
Self-compassion: Treating yourself with the same kindness you'd offer a struggling friend, instead of harsh self-criticism.
Self-concept: The organized set of beliefs a person holds about who they are.
Self-concept maintenance: People cheat or bend rules just enough to gain while still being able to see themselves as honest.
Self-determination continuum: Extrinsic motivation isn't one thing — it ranges from feeling forced to fully owning the reason behind an action.
Self-determination theory: Motivation thrives when three basic needs — autonomy, competence, and relatedness — are met.
Self-discrepancy theory: The gap between who you are and who you think you should or want to be produces specific, predictable emotions.
Self-efficacy: Your belief in your own capability to carry out what a task requires.
Self-enhancement: The drive to maintain and inflate a positive view of oneself.
Self-esteem: A person's overall evaluation of their own worth — how much they like and value themselves.
Self-perception theory: We infer our own attitudes by observing how we behave, as an outside observer would.
Self-regulation (cybernetic model): Goal pursuit works like a thermostat: sense where you are, compare to the goal, act to close the gap.
Self-verification theory: We seek feedback that confirms our existing self-view, even when it's negative.
Sociometer theory: Self-esteem is an inner gauge of how accepted or rejected we are by others.
Terror management theory: Awareness of our own mortality drives us to cling to cultural worldviews and self-esteem that promise symbolic immortality.
Two-factor theory: What makes workers satisfied and what makes them dissatisfied are two different things, not opposite ends of one scale.
Yerkes-Dodson law: Performance rises with arousal up to a point, then falls — and the optimum is lower for hard tasks.

Time & Self-Control

Abstinence violation effect: After one slip, an all-or-nothing mindset turns a single lapse into a full relapse.
Affective discounting: Hot, affect-rich rewards are discounted more steeply than cold, abstract ones.
Akrasia: Acting against your own better judgment.
Commitment device: Binding your future self to the plan your present self wants.
Common difference effect: Adding the same delay to both options flips impatient choices into patient ones.
Construal level theory: The more psychologically distant something is, the more abstractly we think about it.
Delay of gratification: Resisting a smaller-sooner reward for a larger-later one.
Delay-speedup asymmetry: It costs more to delay a reward than you'd pay to speed the same reward up.
Discounted utility model: The classical benchmark: future utility is discounted at a single constant rate per period.
Dread: Anticipating a bad event is itself painful, so we'll rush to get it over with.
Ego depletion: Self-control as a limited resource that tires with use.
Fresh start effect: Temporal landmarks make us more willing to pursue goals.
Future self-continuity: How much you identify with your future self predicts how well you save and plan for it.
Goal-gradient effect: Effort and motivation intensify the closer you get to a goal.
Hot-cool system framework: Self-control is a tug-of-war between an impulsive 'hot' system and a reflective 'cool' one.
Hot–cold empathy gap: When calm, we badly mispredict how we'll act once aroused — and vice versa.
Hyperbolic discounting: We discount the near future steeply but the distant future only gently.
Hyperbolic discounting curves crossing: Two reward curves that cross over time produce a predictable last-minute change of heart.
Hyperbolic discounting of self-control tasks: Because near-term effort is discounted least, the cost of acting now looms largest of all.
Intention-action gap: Good intentions routinely fail to translate into the behavior they were meant to produce.
Intertemporal choice: Trading off costs and benefits that arrive at different points in time.
Ironic process theory: Trying hard not to think or do something makes it more likely to intrude.
Magnitude effect: Big rewards are discounted more patiently than small ones.
Picoeconomics: Modeling self-control as bargaining among successive, competing selves over time.
Present bias: Overweighting the immediate at the expense of the future, even against our own plans.
Procrastination: Voluntarily delaying what you know you should do now, against your own interest.
Projection bias: Assuming your future tastes, needs, and moods will look just like today's.
Psychological distance: How far away something feels — in time, space, social terms, or likelihood — relative to the here and now.
Quasi-hyperbolic discounting: A tractable model with one extra kink that captures present bias in a single parameter.
Reflection on risk over time: Importing prospect theory's reference point and loss aversion into choices over time.
Restraint bias: We overrate our power to resist temptation, and walk straight into it.
Savoring: Looking forward to a treat is pleasurable, so we sometimes delay it on purpose.
Self-control: Overriding momentary impulses so behavior lines up with longer-term goals.
Self-licensing: A virtuous act earns us psychological permission to indulge in a vice next.
Sequence effects: People want experiences to get better over time, even when that lowers the total.
Sign effect: Gains are discounted more steeply than losses of the same size.
Sophisticated vs naive agents: Whether you foresee your own future self-control failures determines how you plan around them.
Temporal discounting and the brain: How neural systems weigh immediate rewards against delayed ones.
Temporal reframing: Recasting a large yearly cost as a tiny daily one makes it feel trivial and acceptable.
Temptation bundling: Pairing a chore you avoid with a pleasure you crave so the temptation pulls you toward the task.
Time discounting: The further off a reward sits, the less it is worth to us right now.
Time inconsistency: Today's carefully made plan is overturned by tomorrow's self when the moment arrives.
Visceral factors: Hot drive states like hunger, craving, and fear hijack choice toward immediate relief.
What-the-hell effect: One small slip triggers a binge — 'I already blew it, so why hold back?'
Willpower depletion debate: The contested question of whether self-control runs on a limited, tiring resource.