They're those melodies you can't get out of your head:

Q: Now I have "Stars and Stripes Forever" stuck in my head. Explain that to me.

Levitin: Scientists call songs that get stuck in your head "earworms," after the German Ohrwurm. We don't know a lot about how or why they happen - it's hard to get funding to study this type of thing - but we know a little. Like, it tends not to be a whole song that gets stuck in your head, just 15-20 seconds of one, and it tends to be a simple song that even non-singers can hum without effort.

Q: Is there a cure?

Levitin: Some people get earworms so bad that it interferes with their ability to sleep or work. For those people, antidepressants and anti-anxiety drugs can help. They relax the circuits. Then again, some people become musicians because they have earworms. Neil Young told me that he started writing songs because he couldn't get rid of the tunes in his head.

This should get sales of Zoloft soaring: