I believe............................

................................this is what Mihaly Csikszentmihalyi  called Flow:  The Psychology of Optimal Experience :  


"So that's just survival instinct. And when I'm doing math, it's all-encompassing and I'm 100% in it, and there's really nothing else to think about when I'm doing math," he said. "I love mathematics, I love the elegance, I love the challenge, and so that's been natural for me."
-as excerpted from here


thanks craig