Interview with Jonah Lehrer, who wrote "Imagine: How Creativity Works."
"... there are probably three neurologically distinct forms of creativity. One is when you have these moments of insight that come out of the blue--when you have epiphanies in the shower. Those seem to come from the part of the brain that's involved in things like the interpretation of metaphors and the processing of jokes. Another form is really working hard at solving a problem--it's not nearly as fun as having an epiphany, but it's just as important. The last form is spontaneous improvisation--what Miles Davis did."
Via Richard Andrews, Sandeep Gautam, Katherine Stevens