Researchers say that the age-old adage of sleeping on a complex decision may not be the best choice at all.
Two research groups have challenged the "unconscious thought" theory regarding complex decisions, proposed in 2006 by Ap Dijksterhuis at the University of Amsterdam in the Netherlands, following experiments in which volunteers were showed a series of cars and their attributes on a screen, before being asked to think carefully about choosing the best car, and the other half to solve anagrams-a distraction technique to allow unconscious processing.
That study had shown that people in the anagram group were more likely to choose the cars with the best attributes, leading the researchers to conclude that it is best to leave tough choices to the unconscious thought.
The new research questioned that conclusion, and instead suggested that the volunteers made their decisions when they first viewed the data, based on an immediate gut instinct.
The researchers behind the two studies said that those in the anagram group simply recalled this original decision when asked to choose. However, they added, those in the "thinking" group reconsidered their first impressions while the details of the cars faded from their memory, which led to poorer choices.
"What Dijksterhuis ignored is that people might already decide when they first hear about the cars, and not after thinking about it or solving anagrams," says psychologist Daniel Lassiter of Ohio University in Athens.
With a view to testing that hypothesis, the researchers repeated Dijksterhuis's experiment with a twist. The volunteers were aked to memorise the cars' attributes while viewing them, thus distracting their attention from making an immediate decision.
Lassiter said that incontrast to Dijksterhuis's experiment, students made better choices when they spent time thinking, rather than solving anagrams.
Writing about the finding in the journal Psychological Science, Lassiter said that that was strong evidence against the idea that unconscious deliberation is superior to conscious decision-making.
Axel Cleeremans from the Free University of Brussels (ULB) in Belgium carried out a very similar experiment to Lassiter, but using apartments instead of cars, and came to the same conclusion.
This second study also saw volunteers being asked to choose as soon as they had viewed the apartment information, with no time for any deliberation.
According to Cleeremans, the decisions made were of the same quality as those made by the volunteers he asked to solve anagrams.
Presented at the annual meeting of the Association for the Scientific Study of Consciousness in Berlin, Germany, these findings provide further evidence that unconscious thought does not improve decision quality.
Dijksterhuis, however, maintains that unconscious thought exists, and insists that he has conducted further experiments directly comparing decisions formed after a period of unconscious thought with those based on first impressions only. He says that the experiments have shown the former to be superior.
He intends to submit his new findings for publication.
John-Dylan Haynes of the Bernstein Center for Computational Neuroscience in Berlin says that the new results show that unconscious thought during anagram solving had no great effect on decision quality.
However, he says, unconscious processing could be important for gut reactions.