I forget who said it...perhaps it was John Gierach...but not too long ago I quoted him on my Facebook page about this. He said that at some point everything we know about trout fishing is proven wrong. It's so true. In fact, it's true of all fishing. But it seems to me to be more true with trout than any other species I've ever fished for. Do it enough and you'll be taught an exception to every rule by some trout somewhere. Good instincts seem to separate the cream from the milk at times like that. I can't "quantify" it either, but many people speak of the unique quality of what I call the "just add water" fisherman. Put any kind of tackle in his or her hands on any water anywhere and soon enough he or she will be catching fish. Call it "fish sense." Call it the ability to think like a fish. Call it whatever you will. But most of us have met someone who just has a knack for catching fish that separates them from most reasonably respectable anglers. I know several of these guys. None of them can explain it in a detailed way either.