Why Do Songs Get Stuck in Your Head?

You heard it once, in a shop, for about twenty seconds. Now it is four hours later, you are brushing your teeth, and the same few bars are still going round in your head like a small, cheerful washing machine. You did not ask for it. You do not even like the song. And the harder you try to think of something else, the louder it seems to get.

This is so common that it has a name, earworm, borrowed from the German Ohrwurm. Psychologists, who prefer longer words, call it involuntary musical imagery. Surveys by researchers in Britain suggest that about nine out of ten people get a song stuck in their head at least once a week, and while most of us simply find it odd, around fifteen per cent say their earworms are genuinely disturbing.

An earworm is rarely a whole song. It is usually a fragment of fifteen to thirty seconds, very often the chorus, playing on a loop with no beginning and no end. It tends to arrive when the mind is not busy with much else: while doing chores, going for a walk or standing in the shower. A song you have heard recently, or heard many times, is more likely to stick, and a single word, a picture or a passing association can dig up a tune you have not heard in years.

So why do some songs stick and others slide straight off? A team at Goldsmiths, University of London, asked around three thousand people which tunes most often got stuck in their heads, then studied what those songs had in common. The earworms were usually faster, with a lively tempo. Their melodies had a fairly ordinary, easy-to-remember shape, but with something unusual in it, such as a surprising leap between notes or a phrase that repeats.

In other words, a good earworm is familiar enough for the brain to hold on to easily, and just odd enough to catch its attention. Advertisers who write jingles have known this by instinct for a very long time. Now there is data behind it.

Getting rid of one is harder, but there are clues. In 2015 psychologists at the University of Reading played 98 volunteers two very catchy songs, then asked them not to think about the songs for three minutes and to press a key every time they did. Volunteers who were chewing gum while they tried reported the song coming back about a third less often. Moving your jaw, the researchers explained, interferes with the inner voice we use to rehearse sounds in short-term memory, and an earworm seems to rely on that same inner voice to keep itself going.

Other research points the same way. Scientists at Western Washington University found that giving the mind a moderately difficult task, such as an anagram, a puzzle or a good book, was an effective way of stopping an earworm. The task needs to be just hard enough to occupy the part of the mind the song is using. Too easy, and the tune simply plays along in the background, as anyone who has hummed their way through the washing-up already knows.