- Person
- Daniel Kahneman
- Lived
- 1934–2024
- Field
- Psychology, behavioural economics
- From
- Israeli-American
The story
Daniel Kahneman graduated from the Hebrew University of Jerusalem in 1954 with a major in psychology and a minor in mathematics. Drafted that year as a second lieutenant, he spent a year as an infantry platoon leader and was then transferred to the psychology branch of the Israel Defense Forces.
One of his duties there was to help assess candidates for officer training, using methods developed by the British Army in the Second World War. In one exercise, a leaderless group of eight soldiers, stripped of rank insignia and identified only by numbers, had to carry a telephone pole over a wall about 2.5 metres high without letting the pole or themselves touch it. Two assessors watched, often for half an hour or more, and felt certain they could see each candidate's true character: leaders, loyal followers, empty boasters.
Feedback from the officer-training school, delivered every month or so on what the unit called statistics day, showed that the assessors' ratings predicted almost nothing. Yet when the next group arrived, Kahneman and his colleagues felt just as confident as before. He was struck by the complete lack of connection between the statistical evidence and the compelling feeling of insight, and he coined a term for it: the illusion of validity.
Almost twenty years later the term entered the technical literature in On the Psychology of Prediction, a 1973 paper with Amos Tversky. Kahneman described it as the first cognitive illusion he discovered, and the theme of overconfident intuitive prediction ran through his whole career. Much later he explained that the assessors had answered an easier question than the one they were asked: they judged an hour of behaviour in an artificial setting and told themselves a story about the future, a pattern he summed up as what you see is all there is.
He found the same illusion elsewhere. Studying the results of 25 wealth advisers over eight years, he found that none stood out consistently, and told the firm's directors that they were rewarding luck as if it were skill. His advice was to trust confident judgments only when there is independent reason to believe the person knows what they are talking about.
Why it matters
The illusion of validity helps explain why experts in fields from finance to hiring overrate their own judgment, and why checking predictions against data matters.
About Daniel Kahneman
Child survivor of Nazi-occupied France who, with Amos Tversky, mapped the systematic errors of human judgment, founded behavioural economics and won the 2002 Nobel Prize in economics.
More about Daniel Kahneman
- Daniel Kahneman showed how framing flips our choicesKahneman and Tversky showed that two logically identical descriptions of a choice, such as lives saved versus lives lost, can lead people to opposite decisions.
- Daniel Kahneman built the Israeli army's recruit interviewAt 21, Daniel Kahneman designed a structured interview for all Israeli combat recruits. It roughly tripled the interviews' predictive power and stayed in use for decades.
- Daniel Kahneman found how we remember painDaniel Kahneman showed that memories of painful experiences depend mostly on their worst moment and their end, the peak-end rule, a finding that can make medical procedures easier to bear.
- Prospect theory became the most cited paper in economicsDaniel Kahneman and Amos Tversky's 1979 paper on prospect theory, showing how people really weigh gains and losses, became the most cited paper in economics.
- Daniel Kahneman showed the eye's pupil tracks mental effortWith Jackson Beatty, Daniel Kahneman discovered that people's pupils dilate steadily as they hold more digits in memory, giving scientists a window onto mental effort.
- Daniel Kahneman's eureka moment about praise and blameWhen an Israeli flight instructor insisted that shouting worked better than praise, Daniel Kahneman realised he was seeing regression to the mean, the most satisfying eureka of his career.
- Thinking, Fast and Slow brought Kahneman's ideas to millionsDaniel Kahneman's 2011 book Thinking, Fast and Slow, describing fast intuitive and slow deliberate thinking, became an international bestseller and won major book awards.
- Kahneman and Tversky mapped the mind's shortcutsIn 1974 Daniel Kahneman and Amos Tversky published Judgment under Uncertainty: Heuristics and Biases, showing how mental shortcuts lead to predictable errors.
- Kahneman's theory helped launch behavioural economicsWhen a 1975 draft of prospect theory reached the young economist Richard Thaler, it explained his puzzles, such as the endowment effect, and helped launch behavioural economics.
- Daniel Kahneman championed adversarial collaborationDaniel Kahneman urged scientists who disagree to run joint experiments instead of trading hostile rebuttals, a practice he called adversarial collaboration.
Sources
- Daniel Kahneman: Biographical NobelPrize.org
- Illusion of validity Wikipedia
Another act of tikkun olam. This is part of tikkun olam, the Jewish idea of repairing the world, and every one of us can add to it.