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
Status
Explained
Well understood mechanically, though it still surprises people.
41 entriesFilter these further →
Beginner
Ages 8+, no background needed.
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
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
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
Buridan's Ass
A donkey stands exactly halfway between two identical bales of hay. With no reason on earth to prefer either, does it starve?
c. 1340 (the attribution; the example is far older)14 min read
Chesterton's Fence
You find a fence in the middle of a field with no obvious purpose. Remove it? Chesterton says no — and the reason reveals something about reform.
19297 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
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 Coastline Paradox
How long is the coastline of Britain? The answer depends on how you measure it. As the ruler gets shorter, the answer grows without bound.
1951 (Richardson), 1967 (Mandelbrot)7 min read
The Abilene Paradox
Everyone at the table agreed to a trip that not one of them wanted to take. How does a group choose what every member is against?
197417 min read
Intermediate
Curious teenagers and general adult readers.
Achilles and the Tortoise
The fastest runner alive can never catch a tortoise with a head start. The argument is airtight. So where does it go wrong?
c. 450 BCE15 min read
Goodhart's Law
The moment you measure something and start rewarding the number, the number stops telling you what it used to.
1975 (Goodhart's formulation), 1997 (Strathern's phrasing)14 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
Gabriel's Horn
A shape you can fill with a finite bucket of paint but whose inside you could never finish painting. How?
16417 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
The Ellsberg Paradox
You know exactly how many red balls there are, and nothing about how many are black. Does knowing more make a bet more attractive?
19617 min read
The Paradox of Thrift
Every family starts saving more. The economy ends up with less saving. How can everyone doing the right thing produce the wrong outcome?
19367 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
Peto's Paradox
A whale has a thousand times more cells than you and lives longer. It should be riddled with cancer. It is not.
1975 (observation), 1977 (Peto's fuller statement)17 min read
The Tristram Shandy Paradox
A man writes his autobiography but keeps falling behind. If he had infinite time, would he ever catch up?
1759 (novel), 1903 (paradox formulated)8 min read
Advanced
Undergraduate level in the relevant field.
Zeno's Dichotomy Paradox
To cross a room you must first cross half of it, then half of what is left, and so on without end. So how does anyone move?
c. 450 BCE18 min read
The Allais Paradox
Offered the same improvement in odds twice, most people take it once and refuse it the second time. Both choices feel obviously right.
1952 (posed at the Paris colloquium), 1953 (published)22 min read
The Giffen Paradox
Some things sell more as the price goes up, and the people buying them are behaving perfectly sensibly.
1895 (Marshall's third edition); 2008 (first credible field evidence)18 min read