THIS year’s National Science and Engineering Week takes place from March 14-23 and will see galleries, universities, schools and museums across the region running events to showcase the real life application of science and the critical role science plays in our lives. Here psychologist Dr Lauren Stewart shares her insights into the so-called ‘earworms’, music that constantly replays in your head.

HAVE you ever woken up with a song that you just can't get out of your head? Or found your mind wandering only to pick out a tune you haven't heard in years? Those random songs are actually something that scientists today think are quite important. They've even given them a name: "earworms".

What is an earworm? An earworm is a short part of a tune that comes into your head and then repeats for a while, for anything from a few minutes to hours. It can have words or it can just be a melody or a rhythm. Earworms are generally very persistent, and it can be difficult to make them stop.

Earworms are a really common phenomenon. Over 90 per cent of the population experience them at least once a week, so it seems like having the odd earworm is perfectly normal. But one in three people classify their earworms as unpleasant. This means that although earworms are essentially harmless they can get in the way of what you are trying to do, and can stop you from thinking straight.

What triggers earworms? They're random, right? Wrong. Scientists have shown that earworms come at very specific times. It's not just because you've heard Katy Perry for the 100th time that week on the radio but quite often, the song your brain chooses has a meaning attached to the lyrics, which relates to some aspect of your life. Even more common is our "song memory", where we attach certain emotions to a song we recall from the time. So if you listened to a lot of Jay Z when stressing about exams, there's a chance that you might pull that song out of the bag when you encounter another stressful time.

Are some tunes more likely to stick in our heads? Scientists have found that it's not just a lot of radio play and success in the charts that makes a record particularly memorable, there are also factors about the song itself that almost encourages our brain to recall them.

One of the things scientists have found is that if the notes are closely spaced together, that makes the song more likely to be memorable: think about the chorus to Rihanna's "Umbrella". Songs that have notes which last a long time, such as Abba's "Waterloo" are also likely to have the sticky-factor.

Why do they pop into my head at random times? Idle brains. Scientists have found that earworms wiggle their way in when our brain doesn't have much to think about. You're unlikely to get an earworm, for example, in the middle of your GCSEs - but you might get one that morning, before your brain has "woken up" and started to assess the day.

So my friend hates anything by Will I Am. Can I (cruelly) implant an earworm into her head?

That's the very subject of scientific trials at the moment: seeing whether you can effectively con a brain into remembering a certain tune.

Why do earworms matter?Scientists believe that earworms are similar to something called "spontaneous thought", which is where you have a sudden memory about an event that may have happened many years ago.

Scientists believe this happens because our brain is finding a way to process a certain situation. In the case of earworms, it's believed that it is the brain's way of creating a state of "alertness and readiness" - which means we deliberately choose music to have a certain effect. Now what we mean by effect varies from person to person. So in a stressful situation, one person might recall music that's fast - a way to challenge and tackle the stressful situation; another might recall music that's slow - a tempo to calm them down.

* National Science and Engineering Week aims to celebrate the role science plays in our lives today and encourage young people - particularly girls at mixed state schools – to study science. Alarmingly, while the number of young people studying science at school is rising every year nearly half of all mixed state schools have no girls studying A-level physics at all. UK universities have also expressed concern that the vast proportion of single science subjects at GCSE level are studied by pupils from the independent sector. Information on events taking place during the week can be found at britishscienceassociation.org/NSEWevents