What Causes a Song to Repeat Over and Over in your Head?

Ever wonder what makes a song repeate over and over in your head?

Ever walk through a department store where some really bad piece of music that you hate was playing, and wake up the next day with that playing off to you inside your mind?

Ever can't get rid of a tune?

Ever wonder why?

It's all in Dianetics: the Modern Science of Mental Health.