What Causes Us To "Get The Bug?"

Take a joyful musical safari. If you haven’t yet read/heard it, check out Zachary Woolfe’s New York Times article 5 Minutes That Will Make You Love Classical Music

It’s a time capsule into today’s classical music aesthetic here in the U.S. (I imagine European musicians would choose dramatically different pieces). But I have a question for you that especially interests me. What is it that causes us to “get the bug,” to not only obsess about a particular piece, but also to essentially adopt a life mission to convince others of the magic of that particular piece? For every person, that special gateway seems to be a different piece of music. Yet each person experiences the same deep passion and absolute conviction of that work’s primacy.

Why does that happen? If you want share your insight, please comment.