In the run-up to Christmas, we're subjected to a daily barrage of festive music – on the radio and television, in shops, train stations, restaurants, pubs and bars. In the UK, old favourites by bands such as Slade and Weezer are doing their regular rounds along with newer contenders from Kelly Clarkson and Justin Bieber. And, of course, Britain's two most popular Christmas songs by Mariah Carey and The Pogues are getting their annual airing.
So are you humming Jingle Bells or All I Want for Christmas while you wrap your presents? Catchy music, "sticky tunes" or earworms, as they have become known, are songs that get stuck in our heads – and while about two-thirds are pleasant or neutral, some can become quite annoying. Earworms are common. Nearly 90% of Finnish adults reported having one earworm a week.
Musically, earworms seem to come more often from songs which have fairly conventional melodic patterns together with something unusual – a key change, or unexpected leaps or repetitions. Just like the well-known negative effects of actually heard background music on concentration and task performance, it seems that earworms can even impair our concentration on other tasks – whether those are songs with lyrics which could interfere with memory or even purely instrumental sequences like the Star Wars theme.
There's a piece doing the rounds written by journalism professor Adam Ragusea, who claims to have identified an elusive "Christmas chord" (a diminished minor 7th flat 5) that might explain the popularity of Christmas songs and why they give us earworms, although not all commentators are entirely convinced. New York-based musician Adam Neely argues it's more about context.
But research suggests that although there could be some common features, the specific songs that evoke earworms are different from person to person. This chimes with what we find when we look at how people listen to music in general. Even very similar types of listeners who live together choose different daily favorite pieces of music – and our music listening and preferences are highly individualised.
What's different about Christmas music is we are all listening to a much smaller pool of musical options at this time of year. Because of the dominance of Christmas music in public settings such as shops and bars or on the radio, we all get a lot more exposure to the same songs than we do at other times of year. So we could argue that Christmas music helps bring us together – whether we love it or hate it.
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Among the cheesy sleigh bells-filled tunes, there are some great Christmas classics – and it's interesting to note that White Christmas by Irving Berlin is not only consistently one of the most well-known Christmas songs but is the best-selling song of all time. It also has the characteristics of an earworm, with melodic shifts and slides around a simple rising and falling melodic shape, and it (like many other songs) contains that scrunchy "Christmas chord". But how does a song like that maintain its popularity over the decades?
The pattern of liking for an individual song over time is held to fit an inverted U-shape curve. According to this, when we first hear a new piece of music we tend to not like it very much. But repetition breeds liking – and repetition both within a song and through repeated listening over days, weeks and months will usually increase our liking in a fairly rapid linear way.
There's a limit to this repetition effect. Too much exposure sends liking down the other side of the curve, meaning that when we have heard something too much we eventually, and quickly, get quite fed up with it. In our research we find that people regulate their own exposure to their own music over very long periods of time, putting things to one side in favour of new music and constantly keeping their current music fresh.
Following this, coming back to music after a period of time away means it moves back up the liking curve and we can tolerate or enjoy it again. Most of us do this quite intuitively, filing songs away physically or figuratively for later, and we have labelled this kind of listening the "squirrel" approach.
That means a lot of Christmas music, whether we think it's good or bad, will be more popular than it might deserve to be as it usually only gets aired a few months of the year. By the time we're taking down the Christmas tree in January, we've all become thoroughly sick of Mariah and Weezer and so we put them away in the attic with the tree, to be dusted off and enjoyed again next year.