The anchoring effect: how a random number influences our judgements

Tversky and Kahneman’s wheel of fortune (1974), prices in the shop, salaries in interviews and how to protect ourselves

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Translated from the Albanian original by the editors. Shqip

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Illustration: a ship at anchor, a symbol of the first number that holds us without our noticing
Original illustration by the lexoshpejt editors. Not a historical photograph or object.
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What is the right price for a coffee? Often we do not know exactly. But if the first menu we see has a coffee at 4 euros, a coffee at 2 euros seems cheap. If the first cost 1 euro, the same coffee at 2 euros seems expensive. The first number becomes a reference point, like an anchor holding a ship close to it.

The wheel of fortune experiment

In a famous 1974 article the psychologists Amos Tversky and Daniel Kahneman described an experiment. In front of participants a wheel with numbers from 0 to 100 was spun, rigged to stop at 10 or at 65. They were then asked: is the percentage of African countries in the United Nations higher or lower than this number? And what do you think it is?

Those who had seen the number 10 gave on average an estimate of about 25 per cent. Those who had seen 65 gave about 45 per cent. The number on the wheel was clearly random, and participants knew it. Even so, it pulled their judgement towards itself.

Why it happens

When we do not know the answer, the mind starts from a point and then adjusts. The problem is that the adjustment is usually insufficient: we stop too close to the starting point. Also, the first number brings to mind thoughts consistent with it, and these thoughts support a judgement near it.

The first number we hear is not just information. It is the starting point of all the thinking that follows.

Where we meet it

  • In the shop: the crossed-out "former" price on a label makes a discount look bigger.
  • In negotiations: the first offer often sets the zone where the agreement ends up.
  • In job interviews: the first salary figure mentioned affects what is accepted as reasonable.
  • In professional estimates: various studies have shown similar effects even among experts, for example in valuing property.

How to protect ourselves

  1. Make your own estimate before hearing the other person's number. Write it down, so it does not shift without your noticing.
  2. Look for different reference points. Before buying, compare several prices; before a negotiation, know the market.
  3. Consider the opposite. Ask: why might the right number be much higher, or much lower? Studies suggest this question reduces the effect.

Sources and further reading

  1. Tversky, A. & Kahneman, D. (1974). Judgment under uncertainty: Heuristics and biases. Science, 185(4157), 1124–1131. doi:10.1126/science.185.4157.1124
  2. Kahneman, D. (2011). Thinking, Fast and Slow. New York: Farrar, Straus and Giroux. WorldCat

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