What’s the best way to make complex decisions about, say, buying a car? (Image: Andy Reynolds / Taxi / Getty)

SLEEPING on a complex decision may not help you make the best choice after all. So say two studies that question the evidence for unconscious decision-making.

The “unconscious thought” theory for making complex decisions was proposed in a 2006 study by Ap Dijksterhuis at the University of Amsterdam in the Netherlands, and colleagues. The team showed volunteers a series of cars and their attributes on a screen, before asking half of them to think carefully about choosing the best …