Does unconscious thought improve complex decision making?

In a recent study, Dijksterhuis et al. (Science 311:1005, 2006) reported that participants were better at solving complex decisions after a period of unconscious thought relative to a period of conscious thought. They interpreted their results as an existence proof of powerful unconscious deliberation mechanisms. In the present report, we used a similar experimental design with an additional control, immediate condition, and we observed that participants produced as good (and even descriptively better) decisions in this condition than in the "unconscious" one, hence challenging the initial interpretation of the authors. However, we still obtained lower performances in the "conscious" relative to the "immediate" condition, suggesting that the initial result of Dijksterhuis et al. was not due to the action of powerful unconscious thought processes, but to the apparent disadvantage of further conscious processing. We provide an explanation for this observation on the basis of current models of decision making. It is finally concluded that the benefit of unconscious thought in complex decision making is still a controversial issue that should be considered cautiously.