Anchoring Effect
A random wheel-of-fortune spin changes your estimate of how many African nations are in the UN. The spin was meaningless. The effect was real. Why?
19746 min read
Type
Observation
Selection effects and the observer's place in the data.
45 entriesFilter these further →
Beginner
Ages 8+, no background needed.
Bystander Effect
If you collapse on a busy street, your chances of getting help may be worse than on a quiet one. Why does a crowd of witnesses make you less safe?
19688 min read
Dunning-Kruger Effect
The less you know, the more confident you feel. The more you know, the more you see how much you don't. Why?
19996 min read
Halo Effect
Why does being attractive make you seem smarter, or sounding confident make you seem right — even when neither is true?
19208 min read
Moore's Law
A pattern that held for fifty years: every two years, computers got twice as powerful for the same price. What happens when it stops?
19657 min read
Murphy's Law
If anything can go wrong, will it? The saying is a joke — but the engineering principle behind it is dead serious.
19497 min read
Occam's Razor
When two explanations fit the evidence equally, which should you believe? The one that assumes less.
c. 13206 min read
Pareto Principle
80% of results come from 20% of effort. 80% of bugs from 20% of code. Is this a law of nature, or a coincidence with a catchy ratio?
18966 min read
Parkinson's Law
Give yourself a week for a task that takes an hour, and it will take a week. Why does work expand to fill available time?
19556 min read
Placebo Effect
A sugar pill reliably reduces pain in clinical trials — measurably, not just subjectively. How does a fake treatment produce real healing?
19556 min read
Sunk Cost Fallacy
You paid for a concert ticket and now feel terrible. If you hadn't paid, you'd stay home. You paid, so you go. Why does a sunk cost change anything?
19857 min read
The Butterfly Effect
Can a butterfly in Brazil cause a tornado in Texas? Not by force — but by changing everything that follows.
1963 (discovery), 1972 (butterfly metaphor coined)7 min read
The Peter Principle
Why does every organisation seem to be run by people who are bad at their jobs? Because the good ones got promoted until they weren't.
19696 min read
Amara's Law
Every major technology is overhyped on arrival and underestimated a decade later. Why does intuition fail in the same direction twice?
19776 min read
Baader-Meinhof Phenomenon
You learn a new word. Within a week, you hear it three times. Did the world start using it when you did — or did you just stop filtering it out?
20066 min read
Brandolini's Law
A tweet spreads a false claim to a million people. Correcting it requires essays and citations. Why does the truth always have to work harder?
20137 min read
Cobra Effect
The British paid a bounty for dead cobras to reduce the snake population. When it ended, the population was higher than before. What went wrong?
19008 min read
Cunningham's Law
Ask a question online and wait hours. Post the wrong answer and be corrected in minutes. Why is the urge to correct stronger than the urge to help?
20106 min read
Hanlon's Razor
They didn't do it to hurt you. Probably they just didn't think. How much does it matter?
19806 min read
Hawthorne Effect
Workers became more productive every time the researchers changed conditions — even when they changed them back. What was the actual cause?
1924–1932 (studies), 1958 (effect named)6 min read
Hofstadter's Law
It always takes longer than you think — and that's still true even after you account for the fact that it always takes longer than you think.
19796 min read
Ringelmann Effect
Add more people to a task and each person works harder, right? Experiments show the opposite. Why does individual effort fall as the team grows?
19136 min read
Semmelweis Reflex
A doctor proved handwashing saved lives. He had the data. The medical profession ignored him for twenty years. Why does evidence trigger resistance?
18476 min read
Streisand Effect
The most reliable way to ensure millions of people see something is to try to prevent anyone from seeing it.
2003 (incident), 2005 (term coined)6 min read
The Friendship Paradox
Your friends have more friends than you do. So do mine. This is true for almost everybody, all at the same time.
199117 min read
Intermediate
Curious teenagers and general adult readers.
Pygmalion Effect
Can a teacher's expectation — with no basis in fact — make a student smarter? The data say yes. The mechanism is more unsettling than the result.
19687 min read
Schrödinger's Cat
A cat sealed in a box, neither alive nor dead until somebody looks. The story was invented to show the idea was absurd.
193514 min read
The Fermi Paradox
The universe is ancient, enormous, and full of ordinary stars much like ours. So where is everybody?
1950 (Fermi's remark), 1975 (Hart's argument)22 min read
The Twin Paradox
One twin flies away and comes home younger than the other. Yet each of them saw the other's clock running slow.
1905 (implicit in Einstein), 1911 (Langevin's traveller)20 min read
Benford's Law
Look at the first digit of every number in a newspaper. You'll see 1 far more often than 9 — and it is a mathematical law, not a coincidence.
19388 min read
Brooks's Law
A software project is six months late. You add more developers. Now it's eight months late. Why?
19756 min read
Conway's Law
Your software will look like your org chart. Not because you planned it, but because you couldn't plan it otherwise.
19685 min read
Dunbar's Number
You can maintain real relationships with about 150 people. Beyond that, a group becomes something different. Is this a law of human nature?
19927 min read
Flynn Effect
IQ scores rise 3 points per decade worldwide. If the tests measure intelligence, are we smarter? Or is something wrong with the tests?
19847 min read
Matthew Effect
Two equally talented people start. One gets a small early advantage. Decades later, the gap is enormous. Where did the extra distance come from?
19688 min read
Metcalfe's Law
Double the users of a network and the value quadruples. This simple mathematics is why some networks become monopolies and others die empty.
19806 min read
Moravec's Paradox
A computer beat the world chess champion in 1997. Getting one to pick up a cup it has not seen before is still hard.
198811 min read
Olbers' Paradox
If the universe is infinite and full of stars, every line of sight should end on one. So why is the night sky dark?
1610 (Kepler), 1744 (de Chéseaux), 1823 (Olbers)17 min read
The Mpemba Effect
A pot of boiling water and a pot of cold water go into the same freezer. Which freezes first?
1963 (observed), 1969 (published)8 min read
Zipf's Law
The most common English word is twice as frequent as the second. Why does language obey the same mathematical law as city populations?
19357 min read
Berkson's Paradox
Two things with nothing whatever to do with each other can look strongly related — purely because of who ended up in the study.
194615 min read
Advanced
Undergraduate level in the relevant field.
The Sleeping Beauty Problem
Woken with no memory of having been woken before, how confident should you be that the coin came up heads?
1997 (posed), 2000 (named and popularised)24 min read
The Ladder Paradox
A ladder too long to fit inside a barn fits inside it — and also does not — depending entirely on who is watching.
1905 (the physics), 1961 (first prominent published version)19 min read
Expert
Graduate level or specialist readers.
The Black Hole Information Paradox
Physics insists information can never be destroyed. Black holes appear to destroy it. Both of those cannot be true.
1974/75 (Hawking radiation), 1976 (the paradox stated)24 min read
The EPR Paradox
Measure one particle here and you instantly know something about its partner light-years away. Einstein thought this proved physics was unfinished.
1935 (argument), 1964 (Bell's theorem), 2015 (loophole-free tests)21 min read