A spin of a rigged wheel changed people's guesses about Africa.
Researchers spun a wheel that landed on 10 or 65, then asked people what share of UN members were African countries. Those who saw 10 guessed around 25 per cent; those who saw 65 guessed around 45. An obviously irrelevant number dragged their answers. This is anchoring, one of the best-known quirks of judgement.
The anchoring effect is the tendency for an initial reference point, even a meaningless one, to pull later estimates toward it. Psychologists first noticed something like it when people judging a series of stimuli compared everything to the first and last items. Amos Tversky and Daniel Kahneman made it famous in their 1974 work on judgement under uncertainty, describing 'anchoring and adjustment': we start from a number and adjust away from it, but not far enough.
Their experiments were memorably simple. In one, people had five seconds to estimate 1 × 2 × 3 × 4 × 5 × 6 × 7 × 8. Those who saw the sequence starting with 1 gave a median guess of 512; those who saw it starting with 8 guessed 2,250. The true answer is 40,320, so both groups anchored on their first few steps. In another study, students asked whether Gandhi died before or after age 9, or before or after age 140, went on to give very different estimates of his age at death, even though both anchors were absurd.
Anchoring has been reported in consumer purchasing, salary negotiations, forecasting and legal sentencing. A car may look like better value placed beside a pricier model. It also appears hard to shake off: in some studies, warning people about anchoring did little to reduce it.
There are caveats worth knowing. In a well-known demonstration by Dan Ariely, people who wrote down high final digits of their social security number later bid more for items such as wine and chocolate. But some studies that used obviously random anchors, such as a die roll, failed to replicate the effect, and how long anchoring lasts has produced inconsistent results. The broad phenomenon is well documented, even if its size varies. The practical lesson: be wary of whoever names the first number.
Source: Wikipedia — Anchoring effect · Text summarised from Wikipedia (CC BY-SA 4.0)
