July 2026
- Jul 18, 2026ConceptsThe Sunk Cost Fallacy: Why We Throw Good Money After BadSweis and colleagues reported in Science in 2018 that mice, rats and humans all showed sensitivity to sunk costs in a foraging task, and that the bias appeared only after the decision to pursue a reward had been made, not in the deliberation before it. Arkes and Blumer's 1985 theatre study showed the same pull: season ticket holders who paid full price attended more plays than discounted buyers seeing identical performances.
- Jul 12, 2026ConceptsThe Availability Heuristic: Why Vivid Beats LikelyAsked whether K appears more often as the first or third letter of English words, most people in Tversky and Kahneman's 1973 study said first; in typical English text it is roughly twice as common in third position. Recall ease, not frequency, drove the answer. Schwarz and colleagues sharpened the point in 1991: people asked for six examples of their own assertiveness rated themselves as more assertive than people asked for twelve.
- Jul 9, 2026ConceptsThe Anchoring Effect: How the First Number Shapes the RestKahneman describes an experiment where people estimated a redwood's height after being given either 1,200 feet or 180 feet, anchors 1,020 feet apart. Their mean estimates came out at 844 and 282 feet, a gap of 562 feet, so roughly 55 percent of the distance between the anchors passed into the answers, which Kahneman calls typical. The defenses with a track record: consider the opposite, and commit to your own number first.
June 2026
January 2026
July 2025
June 2025
- Jun 29, 2025ExplainersHow Incentives Shape OutcomesWhy rewards often produce the opposite of what was intended. Gneezy and Rustichini studied ten Haifa daycare centers, adding a late-pickup fine at six and leaving four as controls: late pickups immediately increased and remained elevated even after the fine was removed, because the fine converted a social obligation into a priced service. Wells Fargo set a quota of 8 products per customer its own research showed was unachievable.
- Jun 19, 2025ExplainersOrigins of Decision Theory: Key DevelopmentsMost people prefer a certain million to a gamble with a higher expected value, then reverse that preference when both options become unlikely, which breaches the independence axiom underpinning expected utility. Savage produced the pattern himself. This page traces the field from Pascal and Fermat through Bernoulli's utility solution to the St. Petersburg paradox, von Neumann and Morgenstern's axioms, and the Ellsberg and prospect theory challenges.
- Jun 19, 2025ExplainersOrigins of Behavioral EconomicsEconomists long defended the rational actor model by arguing that human mistakes are random and cancel out in aggregate. Behavioral economics dismantled that defense by showing the errors run in predictable directions. A rigged wheel of fortune stopping at 10 or 65 moved estimates of African membership in the UN from roughly 25% to roughly 45%, and students handed a coffee mug demanded a median of about $7.12 to sell it while buyers offered only about $2.87.
- Jun 17, 2025ExplainersStep-by-Step: Analyzing Incentive StructuresMap five layers, not just pay: financial, social and status, career, intrinsic, and punishment. The sharpest diagnostic asks what would happen to someone who fully optimized for the stated goal, since in many organizations that person is dismissed as naive. Gneezy and Rustichini reported that late pickups roughly doubled after Israeli daycare centers introduced a fine for lateness, and stayed high even after the fine was dropped.
- Jun 3, 2025ExplainersTranslating Behavioral Economics into Real DecisionsClassical economics assumed homo economicus, a perfectly rational agent describing a species that does not exist. Simon's bounded rationality showed people satisfice rather than optimize, then Kahneman and Tversky showed the errors are systematic even with time and information. The gap this article closes is between knowing and using: understanding anchoring does not stop an asking price from anchoring you, and knowing about present bias does not start your retirement saving.
February 2025
January 2025
- Jan 26, 2025ConceptsThe Norm of Reciprocity: Gifts, Debts, and ObligationsIn Regan's 1971 study a confederate either did or did not hand participants an unrequested Coke, then asked them to buy raffle tickets at twenty-five cents. Those who got the Coke bought 1.91 tickets on average against 1.08, a 77 percent increase from a gift worth about ten cents. The second finding mattered more: how much participants liked the confederate had no significant effect once the gift was controlled. The obligation came from the rule, not the relationship.
- Jan 10, 2025ConceptsProspect Theory: Why Framing Changes How Outcomes FeelTversky and Kahneman's 1981 disease problem put the same numbers two ways: 72 percent picked the certain option when it was framed as 200 lives saved, while 78 percent picked the gamble when it was framed as 400 deaths. The 1979 Econometrica model behind that reversal, its value and probability weighting functions, the disposition effect in Odean's brokerage data, and the limits: coefficients vary by country, and awareness alone does not switch the effect off.
- Jan 8, 2025ConceptsMental Accounting: Why a Dollar Is Not Always a DollarRichard Thaler's 1985 framework says we sort money into separate psychological accounts with their own spending rules, even though a dollar buys the same thing everywhere. Prelec and Simester found bidders offered roughly twice as much for the same sporting event tickets when told they would pay by credit card rather than cash. The same architecture explains sunk cost escalation, tax refund splurges, and why a labeled envelope protects savings better than a mental note.
December 2024
- Dec 27, 2024ConceptsThe IKEA Effect: Why We Overvalue What We Build OurselvesWhy labor inflates perceived worth independently of quality. Norton, Mochon and Ariely documented the effect in a 2012 Journal of Consumer Psychology paper built on experiments handing participants flat-pack IKEA boxes to assemble, finding they assigned disproportionately high value to objects they had put together themselves. The mechanisms are effort justification, competence affirmation and ownership, which is distinct from the endowment effect.
- Dec 25, 2024ConceptsThe Decoy Effect: How Choices Influence Your DecisionsDan Ariely tested The Economist's old subscription page on 100 MIT students. With digital-only at $59, print-only at $125 and print-plus-digital at $125, 84 picked print-plus-digital, 16 picked digital-only, and nobody picked print-only. Remove the option nobody wanted and it flipped: 68 chose digital-only, 32 the premium bundle. Huber, Payne and Puto named this asymmetric dominance in 1982, though a 2014 meta-analysis found the pull weaker when real money is at stake.
- Dec 22, 2024ConceptsChoice Architecture: Designing Decisions for ImpactJohnson and Goldstein found the legal default predicted consent better than culture, income or religiosity, and Madrian and Shea watched 401k participation move from 37 to 86 percent on automatic enrollment alone. The page is honest that its famous cafeteria study is compromised by Wansink's misconduct findings, and it names sludge, the same architecture used to make good choices harder.
- Dec 18, 2024ConceptsWhat Is the Peak-End Rule: Why Endings Define ExperiencesIn the 1993 cold water study by Kahneman, Fredrickson, Schreiber, and Redelmeier, 69 percent of participants chose to repeat the longer trial, the one with strictly more total discomfort, because it ended on a slightly warmer note. A 2003 randomized trial of 682 colonoscopy patients found the extended-procedure group rated the experience as less unpleasant, though the difference in returning for repeat screening was modest.
- Dec 12, 2024ConceptsUnderstanding Cognitive Bias: Irrational JudgmentsPeter Wason showed Oxford undergraduates the sequence 2, 4, 6 in 1960 and asked them to find the rule by proposing sequences of their own. They offered 8, 10, 12 and declared confidently it was even numbers or constant intervals. The rule was any three ascending numbers. Almost nobody proposed something like 3, 11, 47, which would have tested the theory rather than confirmed it. Biases are systematic, so they compound rather than cancel.
- Dec 7, 2024ConceptsHyperbolic Discounting: Why the Present Always WinsPeople demand a large premium to wait one month starting today, but almost none to wait one month starting a year out, the signature of a discount curve that is steep near and shallow far. The most revealing result is a correction: Kidd, Palmeri and Aslin showed in Cognition in 2013 that children who had just met an adult whose promise went unkept waited far less on the marshmallow task. They were reading an unreliable environment, not failing at willpower.
- Dec 1, 2024ConceptsWhat Is the Status Quo BiasJohnson and Goldstein's 2003 Science analysis of European organ donation found consent rates of 85.9 to 99.98 percent in opt-out countries against 4.25 to 27.5 percent in opt-in ones, with survey support for donation similar across them. Madrian and Shea's 2001 study of one company's switch to automatic 401(k) enrollment saw new-employee participation move from about 37 to 86 percent. The article separates the bias from rational switching costs.
November 2024
- Nov 29, 2024ConceptsChoice Overload: When More Options Produce Fewer DecisionsAt Draeger's Market in 1995, Iyengar and Lepper's 24-jam tasting table drew 60 percent of passing shoppers against 40 percent for the 6-jam table, yet 30 percent of those who stopped at six jams bought a jar versus 3 percent at twenty-four. The effect is real but conditional: Scheibehenne's 2010 meta-analysis of 50 studies found a mean effect size near zero, and Chernev's 2015 review of 99 studies pinned it to four moderators.
- Nov 28, 2024ConceptsThe Endowment Effect: Why We Overvalue What We OwnIn the autumn of 1990, Kahneman, Knetsch and Thaler handed Cornell students a bookstore coffee mug at random. Sellers would not part with theirs below a median of $7.12, while buyers offered a median of $2.87 for the identical object, and a third group choosing between mug and cash valued it at $3.12. Twenty minutes of possession moved the price by a factor of about 2.5 and falsified the Coase theorem's prediction that trade would clear.
- Nov 27, 2024ConceptsThe Overconfidence Effect: The Mistakes of the SmartAlpert and Raiffa asked people for ranges they were 90 percent certain contained the right answer. The truth fell outside those ranges roughly 40 to 50 percent of the time. The error is not boastfulness, it is compressed uncertainty, and Moore and Healy showed in 2008 that lumping it in with the better-than-average effect produced contradictions, since overplacement reverses on hard tasks while overprecision does not. Gigerenzer argues frequency formats shrink the gap.
- Nov 25, 2024ConceptsFraming Effect: How Presentation Influences DecisionsMcNeil, Pauker, Sox and Tversky gave 238 patients, 491 students and 424 physicians a choice between surgery and radiation for lung cancer, with identical data shown as survival or mortality figures. Surgical preference fell from 82 percent in the survival frame to 53 percent in the mortality frame, and the shift was statistically indistinguishable across groups. Trained physicians were as susceptible as medically naive patients. The words, not the numbers, did the work.
- Nov 22, 2024ConceptsThe Optimism Bias: Why We Expect the Best OutcomesNeil Weinstein's 1980 study asked 258 undergraduates to compare their own odds of major life events against an average peer. They rated themselves below average on every negative event and above average on every positive one, knowing full well that not everyone can be below average. Tali Sharot's later work found the mechanism that keeps it going: beliefs update strongly toward good news about real risk and much more weakly toward bad news.
- Nov 21, 2024ConceptsGambler's Fallacy: Misconceptions About RandomnessTheir 2016 study found the same corrective pattern in loan officers approving applications and umpires calling pitches, controlling for the merits of each case. A roulette wheel has no memory, but the people watching it keep a ledger, and so do professionals trained for case-by-case objectivity. The page is careful on the hot hand too, noting Miller and Sanjurjo's 2018 correction and that the debate continues rather than treating it as settled illusion.
- Nov 19, 2024ConceptsAnchoring Bias: The First Number Shapes Your MindHow an arbitrary number bends judgment even when everyone knows it is meaningless. Kahneman and Tversky spun a wheel of fortune rigged to land on 10 or 65, then asked what percentage of African countries belong to the UN. Those who saw 10 averaged 25 percent; those who saw 65 averaged 45. Participants watched the wheel being rigged and still could not escape it, because adjustment from an anchor is typically insufficient.
- Nov 13, 2024ConceptsLoss Aversion: Why Losing $100 Hurts More Than Winning $150Kahneman and Tversky's 1979 prospect theory paper found that most people needed stakes of roughly $200 to $250 before accepting a coin flip risking $100. De Martino, Camerer and Adolphs, in PNAS in 2010, then studied two patients with focal bilateral amygdala damage: both tracked expected value and probability normally, yet both showed dramatically reduced loss aversion. Also covers Boston housing sellers, NFL fourth downs and the cultural variation in the coefficient.
- Nov 11, 2024ConceptsRegression to the Mean: Statistical Insights ExplainedA senior flight instructor told Kahneman that praising a clean maneuver was followed by worse flying and criticizing a sloppy one by improvement, so reward clearly did not work. He was right about what he saw and wrong about the cause. Extreme runs contain luck that does not repeat, so the next run drifts toward the pilot's true average whatever anyone says. An entire training culture had been built on evidence the mathematics produced by itself.
October 2024
August 2024
March 2024
January 2024
December 2023
- Dec 14, 2023ConceptsWhy Smart People Make Irrational Financial ChoicesOne illustrative case: an engineer on $180,000 paying minimums on $22,000 of card debt while contributing to a matched retirement account, effectively borrowing at 22 percent to earn 3. He could explain compound interest fluently. What he could not explain was why his behavior diverged from what he knew. Fifty years of behavioral economics documents that gap as patterned, not random, and intelligence does not inoculate anyone.
- Dec 7, 2023ConceptsWhat Is Game Theory? Strategy, Equilibrium, and Why PeopleRational individual choices routinely produce collectively worse outcomes. In the Prisoner's Dilemma, defection dominates whatever the other player does, so both serve three years instead of one. Repetition changes that. In Robert Axelrod's tournaments, the winner was Tit-for-Tat: cooperate first, copy the opponent's last move, four lines of code, and it won the second tournament too. This guide covers equilibria, signaling, auctions and deterrence.
- Dec 3, 2023ConceptsWhat Is Behavioral Economics? How Psychology Overturned the Rational ActorJohnson and Goldstein's 2003 Science paper on organ donation across 11 European countries is the sharpest demonstration: effective donation rates averaged around 15 percent where people had to opt in and around 97 percent where they had to opt out, with demographics, medical infrastructure and stated attitudes otherwise comparable. Covers prospect theory, loss aversion, anchoring, nudge policy and Gigerenzer's objection.
November 2023
- Nov 28, 2023ConceptsUnderstanding Financial Decision-Making Through PsychologyBrickman, Coates and Janoff-Bulman published a now-classic 1978 study finding lottery winners were not significantly happier than a control group and took significantly less pleasure in everyday activities. The windfall recalibrated their baseline without changing the structure of their finances. That is the paradox: money matters enormously, yet the relationship to well-being is more psychological than most people realize.
- Nov 17, 2023ConceptsKey Cognitive Biases and Their Impact on Decision MakingWhich biases matter and what actually reduces them. Kahneman and Tversky's 1974 Science paper identified availability, representativeness and anchoring, and named taxonomies have since grown past 180 entries. Larrick's 2004 review found that teaching people about biases produces modest effects that often fail to generalize, so pre-mortems, appointed dissent and reference class forecasting work better. Gigerenzer argues simple rules often beat optimization.
- Nov 10, 2023ConceptsEffective Money-Saving Strategies Backed by ResearchThaler and Benartzi committed workers to future raises in advance, sidestepping present bias because a decision about money you have not received yet does not hurt. Automatic enrollment separately pushed 401(k) participation from roughly 37 to 86 percent among new hires. The lesson is to stop competing against present bias and change the environment so the choice never comes up.
October 2023
August 2023
January 2023
December 2022
- Dec 31, 2022ConceptsPsychological Ownership: Why We Claim What's Not OursCompletion is what converts labor into felt ownership, which is why consulting employees and then overriding their input can leave less ownership than never consulting them at all. Pierce's framework explains the pull: ownership feelings grow through control, deep familiarity and self-investment, and they serve needs for efficacy, identity and a sense of place, so a threat to what feels yours lands on all three at once.
- Dec 27, 2022ConceptsInflation Psychology: Behavior in Times of Price IncreaseWhy inflation is a psychological phenomenon as much as a monetary one. Coibion and Gorodnichenko found using University of Michigan survey data that household expectations track the prices of frequently purchased goods, notably gasoline and groceries, so a gas spike adding 0.3 percentage points to headline inflation can move expectations by several full points. Expectations are self-fulfilling: believing in 5 percent inflation produces wage demands and preemptive price rises.
- Dec 21, 2022ConceptsThe Bandwagon Effect: Impact on Markets and ElectionsWhy people follow crowds against their own judgment. The 1992 informational cascade model of Bikhchandani, Hirshleifer and Welch showed that once enough people make the same visible choice, following is the rational Bayesian response because the crowd's aggregate signal outweighs a private one. That also makes cascades fragile: each follower has discarded their own information, so the whole structure rests on whether the early movers were right.
- Dec 7, 2022ConceptsUnderstanding Bounded Rationality in Decision MakingHerbert Simon's bounded rationality explained. Simon's argument was not that people are irrational but that rationality must be judged relative to real constraints on information, time and cognitive capacity, and the Royal Swedish Academy awarded him the 1978 Nobel Memorial Prize for this contribution. Classical expected utility theory requires enumerating every option and outcome, which is intractable in real decisions, so people satisfice instead.
- Dec 4, 2022ConceptsWinner's Curse: Why Winning Auctions Can Cost YouWhy winning a competitive bid is itself bad news. Three petroleum engineers named the effect in 1971 after noticing that firms winning offshore oil leases earned the worst returns: whoever submits the highest estimate of an uncertain value has almost certainly overestimated it. Bazerman and Samuelson showed it survives even when participants know the setup, and Andrade, Mitchell and Stafford found acquirer shareholders earned essentially zero across 4,256 mergers.
November 2022
- Nov 26, 2022ConceptsWhat Is Behavioral Economics? Psychology and Decision-MakingKahneman and Tversky described an identical procedure two ways. Framed as a 90 percent survival rate, 84 percent of physicians recommended the surgery; framed as a 10 percent mortality rate, only 50 percent did. Prospect theory explains why: people judge outcomes as gains or losses against a reference point, and losses weigh roughly twice as much. Gigerenzer's critique, that some of these are adaptive rather than errors, remains a live argument.
- Nov 23, 2022ConceptsSunk Cost Fallacy and Its Effect on Decision MakingTwo governments converted the logic into a legal obligation, and a minister defending the program in 1968 argued that the investment already made demanded seeing it through. The lab version is just as clean. Arkes and Blumer tracked Ohio University theater subscribers and found those who paid full price attended more performances, including in bad weather, though the money was gone either way. Staw's Big Muddy study showed the original decider escalates most.
- Nov 19, 2022ConceptsMoral Hazard Explained: Risk from ProtectionThey separated it from physical hazard, the objective risk of the insured thing, because transferring financial risk also transfers the motivation to prevent loss. Three ingredients are needed: a guarantee, separation between who decides and who pays, and actions nobody can observe. Without that third element a contract could simply require the locked garage and verify it monthly.
- Nov 18, 2022ConceptsThinking About Risk: A Practical Framework ExplainedRisk and uncertainty are not the same thing, a distinction Frank Knight drew in 1921. Under risk the probabilities can be estimated from data or theory; under uncertainty they cannot, and you may not even know the full range of possible outcomes, so standard tools become unreliable. Volatility is not risk either: a cash deposit with zero nominal volatility can carry enormous purchasing power risk during high inflation.
- Nov 14, 2022ConceptsEffective Budgeting Strategies: Building a Functional BudgetHouseholds underestimate annual expenses by 20 to 30 percent when planning month to month, and one unexpected bill often triggers abandoning the whole system rather than adjusting it. Sinking funds fix the irregular costs. The research on present bias points the same way, since removing the decision through automation beats trying to out-willpower an impulse at the end of a tiring day.
October 2022
September 2022
- Sep 28, 2022ConceptsWhat Is the Principal-Agent Problem and Why It MattersDelegation, divergent interests and information asymmetry together mean an agent can serve themselves at the principal's expense without anyone acting in bad faith. Graham, Harvey and Rajgopal surveyed over 400 executives and found 78% would sacrifice long-term economic value to meet short-term earnings targets. Jensen and Meckling called the total cost monitoring plus bonding plus the residual loss that survives both.
- Sep 9, 2022ExplainersAsymmetric Information in Economics: Key ConceptsIt won the Nobel Prize 31 years later, and the model it set out now predicts a death spiral in unregulated insurance, where sick buyers raise premiums, healthy buyers drop out and premiums rise again. The page separates the four distinct problems the term covers, since hidden information and hidden action call for different remedies. One concrete marker of the gap: Levitt and Syverson found homes owned by real estate agents themselves sold for about 3.7% more.
August 2022
July 2022
- Jul 24, 2022ConceptsWhat Is the Hot Hand Fallacy: When Streaks Are IllusionsGilovich, Vallone, and Tversky analyzed Philadelphia 76ers shooting and concluded the hot hand was a cognitive illusion. In 2018 Joshua Miller and Adam Sanjurjo showed in Econometrica that conditioning on streaks in a finite sequence systematically understates a shooter's baseline. Corrected, the Cornell shooting experiment shows a statistically significant hot hand. Whether that effect is large enough to change how coaches call plays remains open.
- Jul 16, 2022ConceptsWhat Is Narrative Economics: How Stories Move MarketsShiller's claim is that the stories a society repeats about money change spending, borrowing and hiring, and that they spread like contagion, with infection rates, superspreaders and epidemic curves. He tracks them through newspaper and book archives: frugality language spiking in 1930 to 1932, Bitcoin's rotating justifications, GameStop reaching 483 dollars on a story about making the suits pay. The criticisms get a full hearing too.
- Jul 1, 2022ConceptsWhat Is the Default Effect: Why Pre-Selected Options WinJohnson and Goldstein compared eleven European countries and found survey support for donation was broadly similar while consent rates were not: Germany at 12 percent under opt-in, Austria at 99.98 percent under opt-out. Defaults cut both ways. Madrian and Shea found automatic enrollment lifted 401(k) participation from about 49 to 86 percent, then left many employees stranded at a default contribution rate well below what they needed.
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