You're driving to work, listening to your favorite radio station, when on comes Britney Spears' "Baby One More Time." By the time you pull into your office parking lot, you have, "Oh baby, baby" running through your head. You hum it at your desk. You sing it on your way to the restroom. You tap it out on the conference table during your morning meeting. When five o'clock finally rolls around, your coworkers are shooting you the evil eye and you're ready to pull your hair out.
Why do songs get inextricably stuck in our heads? Experts say the culprits are earworms (or "ohrwurms," as they're called in Germany). No, they're not parasites that crawl into your ear and lay musical eggs in your brain, but they are parasitic in the sense that they get lodged in your head and cause a sort of "cognitive itch" or "brain itch" -- a need for the brain to fill in the gaps in a song's rhythm.
When we listen to a song, it triggers a part of the brain called the auditory cortex. Researchers at Dartmouth University found that when they played part of a familiar song to research subjects, the participants' auditory cortex automatically filled in the rest -- in other words, their brains kept "singing" long after the song had ended [source: Prokhorov]. The only way to "scratch" brain itch is to repeat the song over and over in your mind. Unfortunately, like with mosquito bites, the more you scratch the more you itch, and so on until you're stuck in an unending song cycle.
There are many other theories about why songs get stuck in our heads. Some researchers say stuck songs are like thoughts we're trying to suppress. The harder we try not to think about them, the more we can't help it. Other experts claim that earworms are simply a way to keep the brain busy when it's idling [source: University of Cincinnati]. Just as there are many theories, there are many names for the phenomenon. It's been called everything from "repetunitis" to "melodymania."
So why do some songs get stuck in our heads and not others?