Mental models
Mental models are reusable thinking tools — frameworks that help you reason more clearly and decide better. Each entry below explains what the model is, how it works, how to apply it, a worked example, and where it breaks down.
Explore further: Cognitive biases · Comparisons · Glossary · Ideas
Cognitive biases & psychology
The map is not the territory
“The map is not the territory” means any model, description, or belief is a simplified representation of reality — never reality itself. Maps are useful precisely because they leave things out, but mistaking the map for the terrain leads you astray.
Incentives
Incentives are the rewards and punishments that drive behaviour. To predict what people will do, look not at what they say or intend but at what they are actually rewarded for. As Munger put it: "show me the incentive and I will show you the outcome."
Hyperbolic discounting
Hyperbolic discounting is our tendency to over-value rewards that arrive sooner and steeply discount ones that arrive later — and to do so inconsistently, caring far more about a delay that starts now than the same delay further out.
Reciprocity
Reciprocity is the deep social rule that we feel obliged to return what others give us — a favour, a gift, a concession. Receiving something creates a sense of debt we’re uncomfortable leaving unpaid.
The sunk cost fallacy
The sunk cost fallacy is the pull to keep investing in something — money, time, effort — because of what you’ve already put in, rather than what it will return from here. Past costs are gone whatever you do; only future costs and benefits should decide the next move.
The Dunning–Kruger effect
The Dunning–Kruger effect is the finding that people with the least skill in an area tend to overrate their ability most — because the knowledge needed to do a task well is the same knowledge needed to judge how well you’re doing it. Competence and the ability to see your own incompetence arrive together.
Confirmation bias
Confirmation bias is the tendency to seek, notice, and remember evidence that fits what we already believe, while overlooking or explaining away what doesn’t. We treat beliefs as things to defend rather than test, so gathering evidence quietly becomes reinforcing a belief.
Loss aversion
Loss aversion is the finding that losing something hurts about twice as much as gaining the same thing feels good. Because the pain of a loss outweighs the pleasure of an equal gain, we take irrational risks to avoid losses and pass up fair bets that would pay off.
Anchoring
Anchoring is the way an initial number — even an arbitrary or irrelevant one — pulls our later estimates toward it. Once an anchor is in mind we adjust away from it, but rarely far enough, so the first figure we hear quietly shapes the final judgment.
The availability heuristic
The availability heuristic is our habit of judging how likely or common something is by how easily examples spring to mind. Vivid, recent, or heavily-reported events feel frequent; quiet or abstract ones feel rare — so memorability, not actual frequency, drives our sense of the odds.
Cognitive dissonance
Cognitive dissonance is the mental discomfort of holding two beliefs — or a belief and an action — that clash. To ease it, we usually don’t change the behaviour; we change the belief, quietly rewriting what we think so it fits what we’ve already done.
The framing effect
The framing effect is the way the same facts, described differently, lead to different decisions. “90% survive” and “10% die” are identical — yet people choose differently depending on which frame they’re given, because the wording sets the reference point.
Social proof
Social proof is our tendency to decide what’s correct by watching what others do — especially under uncertainty. When we’re unsure, the behaviour of the crowd becomes evidence, so “everyone’s doing it” quietly turns into “it must be right.”
The endowment effect
The endowment effect is our tendency to value something more simply because we own it. The price at which people will sell a thing they hold is reliably higher than the price they’d pay to buy the same thing — ownership itself adds value that isn’t really there.
The halo effect
The halo effect is the way one strong impression — attractiveness, confidence, a single success — spills over and colours our judgment of unrelated qualities. If someone or something is good in one visible way, we assume it’s good in others, without checking.
The planning fallacy
The planning fallacy is our persistent tendency to underestimate how long a task will take, how much it will cost, and how likely it is to go wrong — even when we’ve been burned by identical tasks before. We plan for the best case and are surprised by the ordinary one.
Decision-making, probability & reasoning
First-principles thinking
First-principles thinking is breaking a problem down to its most basic, undeniable truths and reasoning up from there — rather than reasoning by analogy to how things are usually done. It strips away inherited assumptions and rebuilds from the ground.
Inversion
Inversion is solving a problem from the opposite end — asking how to fail, then avoiding that. Instead of “how do I succeed?”, you ask “what would guarantee disaster?” and systematically eliminate it.
Circle of competence
Your circle of competence is the set of areas where you genuinely have expertise. The model says: know its boundary, operate inside it, and be honest about what lies outside — because most costly errors come from acting confidently beyond your real knowledge.
Occam’s razor
Occam’s razor is the principle that, among competing explanations, the one requiring the fewest assumptions is usually the best place to start. Simpler explanations are more likely and easier to test — not always right, but the right default.
Hanlon’s razor
Hanlon’s razor says: never attribute to malice that which is adequately explained by stupidity, carelessness, or circumstance. Most harm done to you isn’t a deliberate attack — it’s error, oversight, or someone not thinking about you at all.
Bayesian thinking
Bayesian thinking is updating your beliefs in proportion to new evidence — starting from a prior probability and revising it as data arrives, rather than holding fixed opinions. Strong evidence should shift you a lot; weak evidence, only a little.
The Lindy effect
The Lindy effect says that for non-perishable things — ideas, books, technologies — life expectancy grows with age. The longer something has already survived, the longer it’s likely to last. A book in print 50 years will probably outlast one published this year.
Regression to the mean
Regression to the mean is the tendency for extreme results to be followed by more average ones, simply because luck evens out. An exceptional performance is usually part skill, part chance — and the chance part rarely repeats.
Expected value
Expected value is the average outcome of a decision if you could repeat it many times — each possible result weighted by its probability. It tells you which choice pays off in the long run, even when any single outcome is uncertain.
Marginal thinking
Marginal thinking is making decisions based on the next additional unit — the extra cost and extra benefit of one more — rather than on totals or averages. Good decisions weigh the margin: is this next step worth it, here and now?
Chesterton's fence
Chesterton's fence is the principle that you should not remove or change something until you understand why it was put there in the first place. If a rule or structure seems pointless, that’s a reason to investigate — not to demolish.
Via negativa
Via negativa is the principle that improvement often comes from removing the harmful, false, or unnecessary rather than adding something new. Knowing what to subtract — bad habits, weak links, wrong ideas — is frequently more powerful and reliable than knowing what to add.
Signal vs noise
The signal-to-noise model distinguishes meaningful information (signal) from random, irrelevant fluctuation (noise). Most data is mostly noise, and the core skill of good judgement is separating the few signals that matter from the overwhelming static around them.
Ergodicity
Ergodicity is whether the average outcome across many people (the ensemble average) equals the average for one person over time (the time average). When they differ — a non-ergodic system — what looks good "on average" can still ruin any individual who plays.
Streetlight effect
The streetlight effect is searching for answers where it’s easiest to look rather than where the answer actually is. It’s named for the drunk who hunts for his lost keys under the streetlight "because that’s where the light is" — not where he dropped them.
The OODA loop
The OODA loop is a decision cycle — Observe, Orient, Decide, Act — repeated continuously. In a contest, whoever runs the loop faster and orients more accurately gets “inside” the rival’s cycle and disrupts their ability to respond.
The Eisenhower matrix
The Eisenhower matrix sorts tasks on two axes — urgent vs important — into four boxes: do now (urgent + important), schedule (important, not urgent), delegate (urgent, not important), and delete (neither). It separates what matters from what merely shouts.
Survivorship bias
Survivorship bias is the error of drawing lessons only from the things that made it through some filter — the survivors — while the failures, which are invisible, silently distort the picture. What’s missing from the data is often more instructive than what’s in it.
The gambler’s fallacy
The gambler’s fallacy is the mistaken belief that a run of one outcome makes the opposite “due.” After five reds on the roulette wheel, black feels overdue — but the wheel has no memory, and each spin’s odds are exactly what they always were.
Base-rate neglect
Base-rate neglect is the habit of judging a specific case on its vivid details while ignoring how common the category is to begin with. A test result, a stereotype, a striking match — all mislead when we forget the background rate they sit against.
Economics, markets & investing
Opportunity cost
Opportunity cost is the value of the best alternative you give up when you make a choice. The true cost of anything isn’t just its price — it’s everything you could have done with the same time, money, or attention instead.
Margin of safety
Margin of safety is building a buffer between what you expect and what you can withstand — so that errors, bad luck, or wrong assumptions don’t cause catastrophe. You plan for the world being worse than your best estimate.
The Pareto principle
The Pareto principle — the 80/20 rule — observes that for many outcomes, roughly 80% of effects come from 20% of causes. A small share of inputs (customers, effort, code, sources) produces most of the results.
Compounding
Compounding is growth that feeds on itself: returns generate further returns, so gains accelerate over time rather than adding up linearly. Small, consistent advantages — in money, skill, or relationships — become enormous given enough time.
Diminishing returns
Diminishing returns is the principle that as you add more of one input, the extra output it produces eventually shrinks. The first unit of effort or resource yields a lot; each later unit yields less, until adding more is barely worth it.
Network effects
A network effect is when a product or service becomes more valuable as more people use it. Each new user adds value for existing users — so growth feeds growth, and the largest network often wins by a widening margin.
Comparative advantage
Comparative advantage is the principle that you should specialise in what you give up the least to produce, then trade — even if someone else is better at everything. Relative cost, not absolute skill, is what makes trade and specialisation pay.
Supply and demand
Supply and demand is the model that prices and quantities are set by the interaction of how much sellers offer and how much buyers want. Scarcity raises price; abundance lowers it; the two forces settle at a market-clearing equilibrium.
Economies of scale
Economies of scale are the cost advantages a business gains as it grows: producing more spreads fixed costs over more units, so the cost per unit falls. Bigger players can charge less, invest more, and squeeze out smaller rivals.
Tragedy of the commons
The tragedy of the commons is when individuals, each acting in their own rational self-interest, deplete a shared resource that everyone needs — because the benefit of overusing it is personal while the cost is spread across all.
Goodhart's law
Goodhart's law states that when a measure becomes a target, it ceases to be a good measure. Once people are rewarded for a metric, they optimise the metric itself — often at the expense of the real goal it was meant to track.
Parkinson's law
Parkinson's law is the observation that work expands to fill the time available for its completion. Give a task a week and it takes a week; give it a day and it often takes a day — because tasks stretch to consume whatever time they’re allotted.
Creative destruction
Creative destruction is the process by which new innovations replace and dismantle the old — Joseph Schumpeter’s term for how capitalism continually revolutionises itself from within, destroying established companies and industries even as it creates new ones.
Path dependence
Path dependence is when the outcomes available today are constrained by the sequence of decisions and events that came before — history matters, and early choices can lock in long after the reasons for them have vanished. Where you can go depends on where you’ve been.
Mr. Market
Mr. Market is Benjamin Graham’s parable for the stock market personified as a moody business partner who offers to buy or sell every day at wildly swinging prices. You’re free to ignore him — and should only deal when his mood offers you a bargain.
Barbell strategy
The barbell strategy is combining two extremes while avoiding the middle: pairing a very safe core with a small allocation of high-risk, high-upside bets. Nassim Taleb’s approach to thriving under uncertainty — protected on the downside, exposed to the upside.
Zero-sum vs positive-sum
A zero-sum game is one where one person’s gain is another’s exact loss — the pie is fixed. A positive-sum game is one where exchange and cooperation grow the pie, so everyone can come out ahead. Knowing which you’re in changes how you should play.
The cobra effect
The cobra effect is when an attempted solution makes the problem worse, because the incentive it creates is gamed. People optimise the measure you reward rather than the outcome you wanted.
Jevons paradox
Jevons paradox is the counter-intuitive finding that making the use of a resource more efficient often increases total consumption of it — because greater efficiency lowers the effective cost and unlocks many new uses.
Strategy, game theory & competition
Switching costs
Switching costs are the time, money, effort, and risk a customer must spend to move from one product to a competitor. High switching costs lock customers in, protecting a business even when rivals offer something better or cheaper.
Game theory
Game theory is the study of strategic decisions, where your best move depends on what others choose and theirs depends on you. It models situations as "games" with players, choices, and payoffs — revealing why rational individuals sometimes reach bad collective outcomes.
Optionality
Optionality is having choices with limited downside and large potential upside — keeping options open so you can benefit from good outcomes while capping your losses on bad ones. It is valuable precisely because the future is uncertain.
Prisoner's dilemma
The prisoner's dilemma is a game where two players each do better by betraying the other, so both betray and both end up worse than if they had cooperated. It shows how individually rational choices can produce a collectively bad outcome.
Red Queen effect
The Red Queen effect is the need to keep improving just to maintain your position, because competitors and the environment are improving too. Like the Red Queen in Through the Looking-Glass, you must run as fast as you can simply to stay in the same place.
Leverage
Leverage is using a small input to produce a disproportionately large output — Archimedes’ "give me a lever long enough and I will move the world." As a mental model, it asks where a little effort, capital, or insight can be amplified into outsized results.
Economic moat
An economic moat is a durable competitive advantage that protects a business from rivals, the way a moat protects a castle. Warren Buffett’s term for what lets a company sustain high returns over time without being competed away.
Flywheel
A flywheel is a self-reinforcing loop where each part feeds the next, so momentum builds over time. Jim Collins’ metaphor: early pushes are hard and produce little, but the accumulated turns make the wheel eventually spin almost by itself.
Local vs global optimum
A local optimum is the best option within your immediate vicinity; a global optimum is the best option overall. The trap is that improving step by step can strand you on a local peak — better than everything nearby, yet far below the highest summit elsewhere.
Moore's law
Moore's law is the observation that the number of transistors on a chip roughly doubles every two years, so computing power grows exponentially while cost falls. More broadly, it’s the model that some technologies improve at a steady exponential rate.
Nash equilibrium
A Nash equilibrium is a state in a game where no player can do better by changing their strategy alone, given what everyone else is doing. It’s a stable standoff — not necessarily the best outcome for anyone, just one no one can unilaterally improve on.
Schelling point
A Schelling point is the choice people converge on when they must coordinate without communicating — the option that feels natural, obvious, or salient to everyone. Absent a way to talk, we each pick what we expect the others to pick.
Systems, networks & complexity
Second-order thinking
Second-order thinking is considering not just the immediate result of a decision but the consequences of those consequences — the “and then what?” effects that ripple out over time. First-order thinking stops at the obvious; second-order traces the chain.
Systems thinking
Systems thinking is understanding something by how its parts interact as a whole — through feedback loops, delays, and relationships — rather than analysing parts in isolation. Behaviour emerges from structure, so the system, not the individuals, often drives outcomes.
The Peter principle
The Peter principle states that in a hierarchy, people tend to rise to their level of incompetence. Workers are promoted for being good at their current job — until they reach a role they’re bad at, where they stay, no longer competent enough to be promoted further.
Dunbar's number
Dunbar's number is the theory that humans can maintain only about 150 stable social relationships — the cognitive limit on the number of people with whom you can sustain meaningful, reciprocal connections. Beyond it, groups need rules and hierarchy to hold together.
Emergence
Emergence is when a system exhibits properties or behaviours that its individual parts do not have on their own. The whole becomes qualitatively different from the sum of its parts — wetness from water molecules, consciousness from neurons, a market from traders.
Entropy
Entropy is a measure of disorder, and physics says it always increases in a closed system. As a mental model, it captures the universal tendency for things — rooms, organisations, relationships — to drift toward disorder unless energy is continually spent to maintain order.
Bottleneck
A bottleneck is the single constraint that limits the output of an entire system — the narrowest point through which everything must pass. The theory of constraints holds that improving anything except the bottleneck does nothing for overall throughput.
Natural selection
Natural selection is the process by which traits that aid survival and reproduction become more common over generations. As a general mental model, any system with variation, selection, and heredity will evolve — not just life, but ideas, products, companies, and cultures.
Metcalfe's law
Metcalfe's law states that the value of a network grows roughly with the square of the number of its users (n²), because each new user can connect with all the others. Doubling the users roughly quadruples the potential connections — and the value.
Preferential attachment
Preferential attachment is the tendency for those who already have more to gain still more — "the rich get richer." In networks and society, new connections, attention, or resources flow disproportionately to whoever already has the most, widening the gap over time.
Gall’s law
Gall’s law holds that a complex system that works is invariably found to have evolved from a simple system that worked. A complex system designed from scratch rarely works and cannot just be patched into working.
Conway’s law
Conway’s law states that any organisation that designs a system will produce a design whose structure mirrors the organisation’s own communication structure. The shape of what you build copies the shape of how your teams talk.
The Streisand effect
The Streisand effect is when trying to hide, remove, or censor information unintentionally draws far more attention to it. The act of suppression becomes the story, spreading what it meant to bury.
Physics, mathematics & nature
Critical mass
Critical mass is the threshold at which a system becomes self-sustaining — the point where enough has accumulated for a process to keep going on its own. Below it, the effort fizzles; above it, growth or change becomes self-propelling.
Activation energy
Activation energy is the initial push required to start a reaction or change — the upfront cost of getting going, even when the change is beneficial once underway. As a mental model, it explains why beginnings are disproportionately hard, and why lowering the barrier unlocks action.
Risk, ethics & society
Antifragility
Antifragility is the property of things that gain from disorder — they grow stronger under stress, volatility, and shocks rather than merely resisting them. It goes beyond resilience: the resilient survive chaos; the antifragile improve because of it.
Skin in the game
Skin in the game means having a personal stake in an outcome — sharing in the losses, not just the gains. Nassim Taleb’s principle holds that those who make decisions should bear their consequences, or their judgement and incentives become dangerously distorted.
Redundancy
Redundancy is having backup capacity — spare parts, reserves, multiple pathways — so that the failure of one component doesn’t bring down the whole system. It looks inefficient in good times and proves essential in bad ones.
The Overton window
The Overton window is the range of ideas the public currently finds acceptable to discuss and enact. Policies inside it are politically viable; those outside seem radical or unthinkable — until the window shifts.
The veil of ignorance
The veil of ignorance is a thought experiment for fairness: design the rules of a society — or any deal — as if you didn’t know which position in it you’d occupy. Not knowing your wealth, talents, or identity, you’d choose rules fair to every position.
The black swan
A black swan, in Nassim Taleb’s sense, is a rare event that is a huge surprise, carries enormous impact, and — only afterwards — gets explained as if it had been predictable. Because they sit outside past experience, black swans dominate history while staying invisible to models built on the ordinary.