Why won't that song leave your head?

Whole songs rarely loop. What stays is usually a short, repeating chunk like a chorus. Analyzing nearly 3,000 reports, British researchers found sticky songs tend to be fairly fast, follow common up-and-down shapes, and add a slightly unexpected interval that catches the ear.

Recently heard or often-played songs float up more easily. They slip in during dishwashing or walking—hands busy, mind idle. The commute tune that returns at lunch rinse is classic.

There is usually a cue. Besides a track you just heard, a lyric word someone said or returning to a place where you heard it can spring it to mind. Many people also report more earworms when tired or stressed.

People who sing or play instruments often report them more often—minds that hold music tightly.

It is not only beloved songs. Annoying jingles stick the same way. Trying not to think of it often makes it sharper: to suppress it you keep checking what to avoid, and that check replays the tune.

Some people feel better after hearing the track once through. Looping it all day, though, usually tightens the loop.

In a University of Reading experiment, people who chewed gum reported fewer song thoughts. Chewing seems to disrupt the mouth and tongue motions used for silent singing. Moderately hard word puzzles helped too. Too easy and the song squeezes in; too hard and focus scatters.

There is no off switch, but other sounds and tasks usually take the slot and the loop fades.