This may have to do with being relaxed, not really thinking about the problem at hand and letting your intuition take over. I have had experiences where working intensely on a problem, even for weeks, didn't solve it but walking away from it and being totally relaxed and the solution just popped in my head. It could be in a shower, having a meal with friends, in the middle of the night or on a walk. You already have the necessary facts and observations but somehow you have not made that last intuitive leap. And when you do, you instantly know it is right as all of a sudden the cloud of possibilities collapses to a single point!
I don't think of it as creativity as much as sparking one's intuition. The "sleep technique" test also relies pattern recognition, which is sort of a limited creativity. You are making the final connection as opposed to opening up a whole new world of possibilities.
I often have really good ideas under the shower that eluded me while thinking hard about it at my desk. I really wonder when they can reproduce the creative boost of taking a shower in a lab experiment.
I don't think of it as creativity as much as sparking one's intuition. The "sleep technique" test also relies pattern recognition, which is sort of a limited creativity. You are making the final connection as opposed to opening up a whole new world of possibilities.