Can’t get that new song out of your head? You’ve probably got an earworm, which “tends to be this little fragment, often a bit of the chorus of the song, that just plays and replays like it’s stuck on loop in your head,” says Elizabeth Margulis, director of the Music Cognition Lab at the University of Arkansas and author of On Repeat: How Music Plays the Mind. The quirky YouTube hit “What Does the Fox Say?” by Ylvis, Starship’s “We Built This City,” and The Baha Men’s “Who Let the Dogs Out?” are just a few tunes known to spawn earworms, according to Margulis. (Check out this SciFri segment for more on earworms.)

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The phenomenon is quite common. For instance, a study from the Proceedings of the 10th International Conference on Music Perception and Cognition found that more than 91 percent of people reported having an earworm at least once a week, while about a quarter had them more than once a day.

As frequent as earworms may be, however, what triggers them and why they occur still remain mysteries. That’s mainly because earworms—which tend to last eight seconds—are by definition involuntary, and therefore tracking them in a scientific setting can be a near-impossible task. Researchers have yet to develop consistent methods of inducing earworms in test subjects. The data that researchers have culled on the subject so far come from surveys of a few thousand people or from small diary studies—but participants can be unreliable in recalling how often they get earworms, for how long, what they were doing at the time, what might have caused the earworm to disappear, and so on.

Music cognition research suggests that earworms could have something to do with how music affects the brain’s motor cortex, according to Margulis. When people listen to music, “there’s a lot of activity in the motor planning regions,” she says. “People are often imaginatively participating even while they’re sitting still.”

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Repetitive listening could also breed earworms. Indeed, 90 percent of the time, we listen to music we’ve heard before, says Margulis, and “when you’ve heard [a song] the fourth or fifth time, [one] note carries with it just so clearly the implications of the next note. You can almost feel exactly what’s going to happen next.”

A song’s structure might contribute to brain burrowing, too. “There are general patterns of characteristics for songs that frequently get stuck, such as being simple, repetitive, and having some mild incongruity,” James Kellaris, a professor of marketing at the University of Cincinnati who’s conducted research on the influence of music on memory, wrote in an email.

“Fundamentally, an earworm is your brain singing.”

In one study, researchers led by Victoria Williamson, a visiting professor at Switzerland’s Lucerne University of Applied Sciences and Arts and a fellow at the University of Sheffield, analyzed more than 50 different musical features and found that earworm songs—tunes that were mentioned by at least three different people in her survey—tend to have notes with longer durations but smaller pitch intervals. This makes sense, she says, because these are two main features that make songs easier to sing, even for the musically untrained. “Fundamentally, an earworm is your brain singing,” Williamson says. Earworm songs also have a certain amount of built-in predictability, coupled with enough novelty to pique a listener’s interest.

While almost everyone gets earworms at some point, Williamson’s research has found that people with neuroticism and non-clinical levels of obsessive compulsion experience them more often, and for longer periods of time. “These people tend to have more repeated thought processes in general, so it’s perhaps not a huge surprise that these are reflected in their experiences of mental music as well,” she says.

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Earworm susceptibility also has an idiosyncratic component—experiencing them seems to involve being in the right mood (or wrong one, depending on your opinion of the earworm) at the right time. “In addition to traits of songs and traits of people (such as being mildly neurotic or having high exposure levels to music), situation comes into play as a third factor,” Kellaris wrote. “It appears that earworms are more likely to bite when the victim is tired, stressed, or idle.”

Despite the complaints of sufferers, however, the majority of our earworms are actually somewhat enjoyable or neutral experiences, according to Williamson. Her research has shown that people consider only about 30 percent of earworms to be “annoying.” “We’re more inclined to remember the things that annoy us,” she says. “So if you ask somebody about an earworm, they’ll tell you about the one that annoyed them yesterday. They won’t tell you the three or four they briefly had in their head which they didn’t really notice, or [which] just kept them company as they walked around.”

Once an earworm lodges in your psyche, how do you get rid of it? Williamson says the best method is for people to distract themselves with other music or to do something that involves language—perhaps tackle a crossword or start a conversation with somebody. A second technique seems counterintuitive: Engage with the earworm song itself by listening to it repeatedly so as to exhaust the earworm or “complete it,” says Williamson. Because earworms are only fragments of music, listening to the entire track might relieve a person of repeating the same part in her head.

So go ahead, interact with that earworm! And let us know which are your favorite or least favorite ones. We’ll try to keep them out of our heads.

Below is a playlist of some earworm songs you’ve already told us about through Twitter and Facebook. Listener beware!

*This article was updated on May 28, 2014 to reflect the following correction: The original text stated that a study led by Victoria Williamson found that “91 percent of people reported having an earworm at least once a week, while about a quarter had them more than once a day.” That finding was actually reported in a study led by Lassi A. Liikkanen.