“Sleeping on It”

Confirmation that  it really works from the University of Geneva:

After a particularly creative night’s sleep, Paul McCartney rushed to the piano at his girlfriend Jane Asher’s house to scribble down a tune he had heard in a dream. That song, Yesterday, would become a Beatles classic.

Few can claim their slumbering hours are as productive or as lucrative, but scientists have found evidence that "sleeping on the problem" does work. By scanning the brains of volunteers, they found that a good night’s shut-eye seems to stimulate new brain connections that promote learning by turning a weak memory into a stronger one.