Johnson: in the arts, "it is usually only a matter of time before genre boundaries appear. They appear because we induce them: distinctions have a practical value to us. We want to know where a new style begins, where its boundaries are, and who is in or outside of them. We draw demarcations because they are convenient and they help us to talk and focus our valuable time and attention; and once they are established they become self-fulfilling prophecies, because conventional delineations of style affect the distribution of rewards."