The new findings contradict the controversial 2006 research result that unconscious thought is superior for complex decisions, such as buying a house or car.
The new study holds that conscious thought is what leads to better choices.
For the study, the researchers conducted four experiments in which participants were presented with complex decisions, and asked to choose the best option immediately ("blink"), after a period of conscious deliberation ("think"), or after a period of distraction ("sleep on it"), which is claimed to encourage "unconscious thought processes".
All the experiments gave some evidence that conscious deliberation could lead to better choices.
There was no strong evidence for superiority of choices made "unconsciously".
While making decisions such as choosing a rental apartment and buying a car, most participants made choices predicted by their subjective preferences for certain attributes (for example, safety, security, colour or price), irrespective of the mode of thinking employed.
"Our research suggests that unconscious thought is more susceptible to irrelevant factors, such as how recently information has been seen rather than how important it is. If conscious thinkers are given adequate time to encode material, or are allowed to consult material while they deliberate, their choices are at least as good as those made 'unconsciously'."
The study will be published in The Quarterly Journal of Experimental Psychology.