Which would you choose? Studies say you should list the pros and cons, then sleep on it.© Punchstock

The best way to make a tough decision is to put your feet up and think about something else. So says an investigation of people shopping for cars, clothes and furniture.

Many people assume that the best way to tackle a difficult choice is to list the pros and cons and ponder them deeply. Others believe we do better to sleep on it, leaving the decision-making to our unconscious, or intuition.

A team of researchers at the University of Amsterdam, The Netherlands, carried out a series of studies to distinguish between these ideas. In one experiment, university students read a list of features about four different cars, such as facts on their mileage and legroom, before deciding which car to pick.

The experiment was set so that some students were presented with a short list of features, making for a simple decision, while others faced a bafflingly long list of 12 competing characteristics. Some students were left to think about their decisions for a few minutes, whereas others were distracted by being asked to solve anagrams.

Don't think about it

For the simple decisions, students made better choices when they thought consciously about the problem. But for the more complex choice, they did better after not thinking about it, Ap Dijksterhuis and his colleagues report in Science¹. To carry this idea into the real world, the team also studied people who were shopping: either in an Amsterdam department store, where they bought straightforward clothes or kitchenware, or in IKEA, where they bought furniture, which one might expect to be a more complicated decision-making process. The team asked the shoppers whether they had thought hard about their purchase beforehand, and a few weeks later asked them whether they were happy with it.

These results confirmed the earlier ones. Department-store shoppers who made simple purchases were happier if they had thought consciously about their choice in advance. IKEA shoppers, on the other hand, were happier with their choice if they hadn't mulled them over.

At least when making some complicated decisions, such as choosing a car or house, the results suggest that we would actually do better to go with our gut.

The big picture

Researchers do not know exactly why this unconscious deliberation should be so successful. But it is well accepted that our conscious brain can only process a limited amount of information at one time. This could mean that we simply lose the big picture with complex decisions.

Dijksterhuis and his team also propose that, although we are unaware of it, our brains are churning through the mass of information involved in a complex decision and sifting out the best option.

The study ties in with a growing trend in psychology research over the past 15 years, suggesting that our unconscious mind is more important than we once thought. "A lot of complicated processes occur without our being aware of it," says Daniel Kahneman, an authority on decision making at Princeton University, New Jersey.

Snap decisions

The results might help to explain why experts, such as doctors or firemen, can sometimes make seemingly intuitive snap decisions that turn out to be correct. These people have a wealth of knowledge, but they don't need to consciously work through it to make an accurate judgement.

But the theory doesn't mean that going purely on impulse is a good idea: you still need some information to mull over before making your decision. Particularly when making potentially life-changing judgments such as whom to marry or which career to choose, experts say, study and deliberation are vital to reveal all the options open to us.

"I would not advise people to buy a car or house without making a list," Kahneman says. "You will probably improve your intuitions by making a list and then sleeping on it."

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• References

  1. Dijksterhuis A., et al. Science, 311 . 1005 - 1007 (2006).