There's a ton of interesting biopsychological ideas swirling around here that aren't completely understood and are the subject of intense debate, though there is a whole lot understood better now than ever before.
Does behaviour influence brain or brain influence behaviour?... haha, ask that to a psychologist and a biologist and biopsychologist and watch the sparks fly!

Personally, I think this right brain, left brain stuff is a bit overblown. You say "oh, I'm right brained, I'm creative." I say, "Good for you. I have both halves of my brain and they both function." End of pet peeve rant.

I think what is most important and what it boils down to in the practical outcome of this discussion is this: Someone is unsure of their ability/future in whatever capacity. If someone tells them "You weren't born to do this, and there's really only 10-15% 'potential' that you can influence through your behaviour, since you were raised in X and have gene Y." (NB: I realize I'm stretching a little bit what has been discussed above). That will be very destructive. What is true is that the more someone tries, fails, and is encouraged, the closer they will get to achieving art, whether they have that "inborn talent" or not.