EVERYONE has had the experience. You are confronted by a complex problem, with a not-so-obvious solution. You pore over it, engrossed, but still the answer will not come. Fearing you will be stuck for ever, you take a walk. Then suddenly, from nowhere, there it is. Eureka!
But did it really come from nowhere? A piece of research about to be published in the Journal of Cognitive Neuroscience, by Joydeep Bhattacharya at Goldsmiths College in London and Bhavin Sheth at the University of Houston, in Texas, suggests that although people are not consciously aware of it, their brains have to be in a certain state for an insight to take place. Moreover, that state can be detected electrically several seconds in advance of the aha! moment itself.
http://www.economist.com/science/displaystory.cfm?story_id=13489722