One of the most enjoyable things I experience: stepping away from something that is confusing, only to come back some time later to tackle it again, anew — if not to have had any strong insight in the meantime.

As most of us know from experience, if we concentrate too intensively on a tough problem, we can get stuck in a mental rut. Our thinking narrows, and we struggle vainly to come up with new ideas. But if we let the problem sit unattended for a time — if we “sleep on it” — we often return to it with a fresh perspective and a burst of creativity. Research by Ap Dijksterhuis, a Dutch psychologist who heads the Unconscious Lab at Radboud University in Nijmegen, indicates that such breaks in our attention give our unconscious mind time to grapple with a problem, bringing to bear information and cognitive processes unavailable to conscious deliberation.