[zephen]

When I was reasonably experienced, and about 6 months into a new job, one of my co-workers, Fred, had been there for a very long time.

Fred was very knowledgeable, and Fred could think. But Fred had deeply held preconceived notions that interfered with the utility of his thoughts.

Fred also had something else, though -- he could set aside those deeply preconceived notions. Not for himself, mind you, but for someone else.

I could, and did on a very regular basis, go to Fred and say "Fred! Assume X, Y, and Z. What happens if A and B?" Now even though Fred was completely sure that I was wrong about at least Y and Z, he could set aside those prejudices, and (correctly!) reason through what would happen.

Fred reminds me of the people you describe, except that instead of having Fred's code running through my brain, I was able to insert my code into Fred's brain.