i disagree, but not in the context that you mean it.

let's take the example of taking a test. we'll follow two scenarios: you are taking the test, and you run into a problem you know a little about but can't get the answer right away. first scenario, you sit there and try to think the answer through, then move on. the second, you move on, then during the middle of a different problem, you realize the answer to the first problem. from personal observation, the second scenario yields better results. the reason would be that even while you're thinking about the new problems, you are still thinking about the first (maybe it's just the ocd in me), you then get the answer to the first 'hard' question for free, in that you've spent your time thinking about other things instead of trying to think about the first thing.

not really what you were talking about, but something i still feel to be true. yes, belief, but please someone with the resources find out; i've spelled out a good test for it.

just my ramblings, take it for what you will.