Thinking Errors & Cognitive Biases

Confirmation bias

Hits stick in memory while counterexamples slip through. Psychologist Peter Wason demonstrated it in 1960 with his number sequence 2, 4, 6.

💡 Did you know? Search engines and social networks can amplify it, because they show us more of what we already like.

Dunning-Kruger effect

Psychologists David Dunning and Justin Kruger described it in 1999 at Cornell University.

💡 Did you know? It was inspired by a bank robber who rubbed lemon juice on his face, believing it would make him invisible to cameras.

Anchoring effect

In 1974 Amos Tversky and Daniel Kahneman used a rigged wheel of fortune to show it.

💡 Did you know? Retailers use it with crossed-out sky-high prices that make the real price look like a bargain.

Hindsight bias

Baruch Fischhoff demonstrated it in 1975; in everyday life it sounds like “I knew it all along!”.

💡 Did you know? It makes learning from mistakes harder: if you think you knew it all along, you stop asking why you were wrong.

Gambler’s fallacy

On 18 August 1913 black came up 26 times in a row in Monte Carlo, and many lost a fortune betting on red.

💡 Did you know? The ball has no memory: on every spin the chance of red is exactly the same as before.

Sunk cost fallacy

A textbook example is Concorde: Britain and France kept building it although the aircraft could never pay off.

💡 Did you know? It is also known as the “Concorde fallacy”, after the supersonic airliner.

Halo effect

Edward Thorndike described it in 1920 when officers were rating their soldiers.

💡 Did you know? The reverse also exists: a single bad impression can overshadow everything else.

Bandwagon effect

The name comes from the band wagon in a parade that people jump on to be part of the crowd.

💡 Did you know? That is why pre-election polls are suspected of steering votes towards the favourites.

Availability heuristic

After news of plane crashes many people think flying is more dangerous than driving, although the opposite is true.

💡 Did you know? Sharks seem more dangerous than many everyday risks simply because shark attacks get far more news coverage.

Survivorship bias

During the Second World War statistician Abraham Wald advised armouring the spots without bullet holes: planes hit there never came back.

💡 Did you know? Advice from successful college dropouts is misleading too: you never hear from the many who failed.

Framing effect

Tversky and Kahneman showed it in 1981 with a thought experiment about an impending disease outbreak.

💡 Did you know? That is why a yoghurt label prefers “95% fat-free” to “5% fat”.

Endowment effect

In experiments with coffee mugs, owners asked for about twice as much as buyers were willing to pay.

💡 Did you know? Economist Richard Thaler coined the term in 1980; he won the Nobel Prize in Economics in 2017.

Barnum effect

In 1948 Bertram Forer gave all his students the same “personal” analysis; on average they rated it as highly accurate.

💡 Did you know? It is named after showman P. T. Barnum, whose shows had something for everyone.

Planning fallacy

The Sydney Opera House was finished ten years late and cost about fourteen times the original estimate.

💡 Did you know? Hofstadter’s law jokes that it always takes longer than you expect, even when you take that into account.

Status quo bias

That is why defaults are so powerful: countries with opt-out systems have far more organ donors.

💡 Did you know? Many people stay on the same energy tariff for years, although switching takes only minutes.

IKEA effect

Michael Norton, Daniel Mochon and Dan Ariely described it in 2011 and named it after the Swedish furniture store.

💡 Did you know? Back in the 1950s cake mixes reportedly sold better once buyers had to add a fresh egg themselves.