Working on problems during sleep

I found if I go to bed with a question on my mind, all I have to do is concentrate on the question before I go to sleep and I virtually always have the answer in the morning. Sometimes I realize what the answer is because I dreamt the answer and I can remember it. Other times I just feel the answer, and I start typing and the answer emerges onto the page.

~ Chris Langan, in Malcolm Gladwell’s Outliers: The Story of Success