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Last Updated: Friday, 17 February 2006, 11:07 GMT
Sleep on it, decision-makers told
Meat in a supermarket
Scientists said the conscious brain could only cope with small decisions
When it comes to making tough decisions - don't sweat it, sleep on it - or so a team of scientists recommends.

A Dutch study suggests complex decisions like buying a car can be better made when the unconscious mind is left to churn through the options.

This is because people can only focus on a limited amount of information, the study in the journal Science suggests.

The conscious brain should be reserved for simple choices like picking between towels and shampoos, the team said.

Mind puzzles

Psychologists from the University of Amsterdam in the Netherlands divided their participants into two groups and devised a series of experiments to test a theory on "deliberation without attention".

One group was given four minutes to pick a favourite car from a list having weighed up four attributes including fuel consumption and legroom.

The other group was given a series of puzzles to keep their conscious selves busy before making a decision.

The conscious thought group managed to pick the best car based on four aspects around 55% of the time, while the unconscious thought group only chose the right one 40% of the time.

But when the experiment was made more complex by bringing in 12 attributes to weigh up, the conscious thought group's success rate fell to around 23% as opposed to nearly 60% for the unconscious thought group.

Sleep on it - when the decision is complex
Dr Dijksterhuis

A second study followed up a group of shoppers and asked them how satisfied they were with simple products such as kitchen accessories and clothing.

They were also asked about more complex products such as furniture.

The researchers found the shoppers they had classed as conscious shoppers reported most post-choice satisfaction with the simple products they bought.

But the results were the reverse with the furniture products.

The study says: "The scientific literature has emphasized the benefits of conscious deliberation in decision making for hundreds of years.

"In contrast, the notion that unconscious thought is fruitful hardly developed beyond the status of "folk wisdom".


But the study found that people can think unconsciously and that for complex decisions unconscious thought is actually superior.

The team argued the problem with conscious thought is that the brain can only focus on a few things at the same time, which can lead to some aspects being given undue importance.

Lead researcher Dr Ap Dijksterhuis said: "The take-home message is that when you have to make a decision, the first step should be to get all the information necessary for the decision.

"Once you have the information, you have to decide, and this is best done with conscious thought for simple decisions, but left to unconscious thought - to 'sleep on it' - when the decision is complex."

Jonathan Schooler of the University of British Columbia in Vancouver told Science the study built on evidence that too much reflection could be detrimental in some situations.

"What may be really critical is to engage in [conscious] reflection but not make decision," he added.

'Thoughts read' via brain scans
07 Aug 05 |  Health

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