Wheel stops at 10, guess 25%; at 65, guess 45%: a Thinking, Fast and Slow spending checklist

A rigged wheel stopped at 10, and students estimated that African countries make up about 25% of UN member states. For the group whose wheel stopped at 65, the average estimate was 45%. The correct figure is 28%. The number on the wheel had nothing to do with the answer, yet it pulled the two groups' estimates in opposite directions.

This is the anchoring experiment described in a strategy+business review dated 29 May 2012, drawn from Thinking, Fast and Slow. Its author, Daniel Kahneman, was born on 5 March 1934 and died on 27 March 2024, aged 90. In 2002 he shared the Nobel Memorial Prize in Economic Sciences with Vernon L. Smith, for integrating psychological research into economics, especially on how people judge and decide under uncertainty.

The book was published in the United States by Farrar, Straus and Giroux in 2011, and Wikipedia lists the US edition at 498 pages. The paperback on Penguin's UK page runs to 624 pages, with a publication date of 22 February 2024 and a price of £16.99 (as of October 2026; prices may change at any time). The two page counts come from different editions.

Two systems: the fast one often decides first

The book divides thinking into two modes. System 1 is fast, automatic and emotional, and works unconsciously; System 2 is slower, effortful and more logical, and is conscious thought.

The strategy+business review notes that System 1 is effortless and intuitive, relying on heuristics that can mislead; System 2 is slower and more deliberate, and can sometimes overrule System 1. The catch is that System 2 is not as diligent as people expect, while System 1 can be very persuasive.

Penguin's description goes a step further: even careful reasoning can be affected by errors and biases. In other words, feeling that you have thought something through is not the same as having done so.

Loss aversion: losing £100 hurts more than winning £100 pleases

Loss aversion comes from the prospect theory of Kahneman and Amos Tversky. Their paper appeared in the journal Econometrica in 1979 and is described as the most cited paper in that journal. The core of the theory is that people give losses more weight than equivalent gains, so they are more inclined to avoid a loss than to pursue an equal gain.

Daniel Read of Warwick Business School gave a contrast in an article dated 3 April 2024. Faced with gains, most people prefer a certain £100 to a 50% chance of £200; faced with losses, most would rather gamble on a 50% chance of losing £200 than accept a certain loss of £100. In other words, people tend to be cautious about gains and risk-seeking about losses.

The same article points to a practical use of this tendency: charging customers for paper cups is more effective at getting people to bring their own than offering a discount to those who do. That is consistent with losses carrying greater weight.

Anchoring: the first number is the hardest to shake

The wheel experiment at the start is anchoring. Wikipedia gives another example: one group was asked whether Gandhi lived to be 114, another whether he lived to be 35, and the first group's estimate of his age at death was far higher than the second's.

In everyday life, the first price you see, a valuation someone mentions in passing, or the first line on a quotation can each become that wheel.

Before you read: some of the book's research has been questioned

The book is not beyond criticism. According to Wikipedia, one analysis gave the studies cited in chapter 4 a replicability index of just 14, and some priming research has also been questioned. Kahneman himself admitted: "I placed too much faith in underpowered studies" (as quoted by Wikipedia). Readers should not treat every experiment in the book as settled.

A self-check list for spending and investing

The scenarios below were put together by the editors from the concepts above. They are not taken from the book, are general prompts for thinking only, and do not constitute investment or financial advice. For personal investment, tax or insurance decisions, consult a licensed professional.

Everyday spending

• Before you buy, decide whether this is an impulse of the moment or a choice you could explain to a friend with the same reasons. The former is more likely System 1 in charge.
• When an original price sits beside a discounted one, ask yourself: if you had never seen the original price, would you be willing to pay this one?
• When pushed by words such as "limited time" or "about to miss out", notice whether you are pursuing a gain or trying to escape the feeling of a loss.

Large purchases

• Write down the first price you heard, then deliberately find a fully independent reference price and compare the two before making an offer.
• Delay the decision for a while, giving the slower, more effortful System 2 a chance to step in.
• When comparing options, write down both what you get and what you give up, so you do not stare at only one side.

Investment decisions

1. Check whether you are reluctant to sell because of your purchase price; that price may be just another anchor.
2. When facing a paper loss, notice whether you are more willing than usual to take risks in order to win it back.
3. Write down your reasons for a decision and compare them with the outcome later, to see whether you relied on evidence or on feeling.

Slowing down is a habit you can practise

Penguin's page describes the book as offering methods to help people think more slowly and more accurately in work and everyday decisions. This checklist cannot free you from System 1, and you do not need to be free of it. What is worth doing is adding one more check at the moment when the number is biggest and the emotion strongest: where did the first number that popped into your head come from?

Prices and details correct as of October 2026

Compiled by the F50 Editorial Team from public sources, for general reference only and not professional advice. Details are correct as of the publication date and may change.