"Earworms", some people call them. Songs that get stuck in your head go round and round, sometimes for days, sometimes for months. For no clear reason you cannot help yourself from humming or singing a tune by Lady Gaga. To a psychologist, the most interesting thing about earworms is that they show a part of our mind that is clearly outside of our control. Earworms arrive without permission and refuse to leave when we tell them to. They are parasites   living in a part of our minds. If you have got an earworm you can suffer an attack of it simply by someone mentioning the tune, without having to hear it. This proves that earworms are a part of long-term memory. Humans have an "inner ear", for remembering phone numbers, for instance. When it gets infected with earworms, rather than review our plans for the day, or lists of things to remember, the inner ear gets stuck on a few short bars of music or a couple of phrases from a song. A part of us that we normally do not have to think about, that should just do what we ask, has been turned against us, upsetting us with a request that we never asked for. The mind is an inner world which we do not have complete knowledge of, or have control over. Fortunately psychology can provide some advice on how to deal with an uncontrollable mind. Consider the famous "don't think of a white bear" problem, which tells you to try not to think about white bears, or to do something else, to avoid both thinking of the white bear and not thinking of the white bear. For earworms, the solution may be the same. Our inner ear has become infected with an earworm. This is a part not under our control, so just sending in instructions to "shut up" is unlikely to be of much help (and has been shown to make it worse). Much better is to employ the inner ear in another task. If your mind is poisoned by Brittany Spears' Toxic, for instance, then try singing Kylie Minogue's Can't Get You out Of My Head. Let me know if works! According to the passage, earworms are    _   .
songs that keep going round in our mind worms that live in a part of our brain tunes by pop singers like Lady Gaga parasites clearly under our control