The Earworm Riddle

‘You’re doing it again…’

Oh.

‘Sorry.’

Hmm, now where was I? Oh yes… Interrupted, I return to my train of thought as I go back to minding my own business. The trouble is, it starts to happen so softly, so imperceptibly that I don’t even realise, and before I know it I’m –

‘Shut up!’

‘Sorry!’

– unashamedly full-blown whistling Chopin’s nocturne in E flat major for all around me to hear. Again.

Something sinister is stirring in the auditory cortex, but you’ll be relieved to know that the worms we’re discussing are not of the vermicious kind (‘of, or pertaining to (wriggly) worms’ – since you were wondering. Aren’t words great?) but are instead, of the musical variety.

The term ‘earworm’ comes from the German word Ohrwurm, and refers to the strange but common phenomenon of experiencing episodes of persistent musical imagery: having a tune ‘stuck in your head’.  We probably all know this feeling: that one little snatch of a song that keeps going round and round in your head and just won’t go away; but have you ever wondered why this happens? How can we be ‘hearing’ something that is just in our heads and isn’t physically a sound? And what purpose – if any – does it serve?

Earworms are a subject near (frequently!) and dear to my brain, so naturally I was delighted to discover that they are actually an area of legitimate scientific study. My long-suffering dad has often likened life in our house to being the owner of a jukebox except that you don’t get to pick any of the songs, and it won’t turn off – such is the extent to which my sister and I are plagued by earworms. It’s often been the case that I’ll suddenly realise I’m humming something, pause in confusion wondering when I’ve heard it recently to have picked it up, only to hear an off-key, yet commendably enthusiastic humming of the very same tune drifting across from my sister’s room! (Whilst I was at home for the Christmas holidays I noticed that a slightly disturbing mash-up comprised of Liszt’s ‘Hungarian Rhapsody’, songs from ‘Les Misérables’, and the more festive ‘Baby, It’s Cold Outside’ seemed to have taken root in the Casterton household…)

Perhaps alarmingly, much of what we know about earworms comes from the considerable research effort of the advertising industry. The motive behind this is obvious if not slightly sinister, you need only think of the most legendary advert jingles which have wormed their way into our collective memory to see the power behind being able to understand how musical imagery works. Research in this field aimed at marketing suggests that music that is simple and repetitive (and therefore easy to remember) yet has an unexpected variation in rhythm is more likely to become an earworm, as it is thought that they can be triggered when we subconsciously detect something unusual about a piece of music.

From research it’s thought your average earworm is a 15-30 second loop, but can be longer. The type of music that makes an earworm varies widely, generally depending on the sort of music you’re exposed to as a result of culture and personal preference. In one study pop music, film scores and – interestingly – Christmas songs were amongst the types of music most reported as earworms. I can certainly sympathise with this as my own earworm repertoire more often than not consists of classical music, and most notably film scores. In fact, as I write this my earworm du jour happens to be the ‘Jurassic Park theme’ composed by John Williams (which I have to say, has actually been quite motivational!) And I’ve been reliably told that I was insufferable to live with in the week after I saw the first Hobbit film.

So, what is going on in our brains? How on earth can we be ‘hearing’ something that’s not physically a sound? The important yet baffling thing to understand about earworms is that they really are just in your head. When you’ve got a song on the brain there is nothing physically going on in your ears, there is no sound energy corresponding to the music you’re ‘hearing’ displacing air in a wave and hitting your eardrum.

Frustratingly, earworms as an area of science is one that researchers are only just starting to delve into properly, and so little systematic investigation has been carried out. Most studies so far seem to be concerned with the ‘what’ rather than the ‘how’ or ‘why’, and generally involve questionnaires or ‘earworm diaries’. These unfortunately are rather subjective methods which rely on your volunteers being able to accurately judge when an earworm episode starts and for how long it lasts. Being one yourself, you’ll know that humans are often prone to…well, human error, and poor judgement.

However, there is a rather simple yet clever experiment that has provided some promising information about what’s going on when we’ve got a song on the brain. A study conducted by David Kraemer and other scientists at Dartmouth College, USA used fMRI (functional magnetic resonance imaging, which produces an image based on the principle that more blood flows to more active areas of the brain) to observe the primary auditory cortex and auditory association cortex of volunteers. The subjects were played songs from their own unique playlists selected by the scientists, which contained some songs which were known to the person and some which they’d never heard before. The nifty bit is that, unbeknownst to the people in the scanners listening to their songs, the researchers had inserted gaps of silence lasting 2-5 seconds in the middle of songs beforehand.

Interestingly, activity was seen in the auditory association cortex during the gaps of silence, and more activity was measured here during the gaps in familiar songs than in unknown songs. This study is clever because it attempts to side-step the problem that earworms happen spontaneously and are therefore difficult to create in a lab setting (similar to the problem of studying tears I mentioned in my last post). The results of this study demonstrate the compulsory nature of musical imagery: our brains literally can’t help filling in the gaps! True, the unexpected silences in the songs aren’t the same thing as a proper earworm where a snippet of song is repeatedly going around your head, but they do effectively set up an earworm ‘moment’, unlike previous studies which just ask volunteers to imagine a song or note.

So is there method to this musical madness: do earworms have a purpose? One interesting theory suggests that it is a remnant from behaviour in our evolutionary past. Music and songs helped people to remember things and share information before we had invented writing. It’s thought that variations in rhythm and melody provide cues for easier recall; so perhaps when your brain comes across a new rhythm or melody that it notices as unusual it subconsciously initiates mental repetition to ensure it’s remembered?  Just think about the power rhythm and music can have in helping us to remember things (altogether now: ‘Mrs B, Mrs E, Mrs A-U-T…’). How many times during your schooldays did you, worn down with revision, bitterly marvel the ease with which you could memorise the lyrics of endless songs yet struggled with those equations? It’s one possible explanation, but for now it seems for a more conclusive answer to the questions surrounding this strange auditory quirk, we’ll just have to wait. But in the meantime, I think I feel a song coming on…

(Don’t be shy – leave a comment and share your earworms, the stranger the better! What’s your earworm of the moment? Do you have any reoccurring ones? Are they enjoyable or just annoying?)

D.Kraemer et al. (2005) Musical Imagery: Sound of silence activates auditory cortex  Nature, 434:158

Tears of the Unknown: Why do we cry when we’re sad?

Anyone with experience of being human knows that feeling ‘sad’ is often a very complex thing. When we’re young children, our emotions tend to polarise into the two categories happy and sad; and part of growing up is gradually discovering the words which enable you to name and express exactly the many subtler feelings contained by these two broad, limiting words. ‘Sadness’ is a very general term. We can feel sad due to a mixture of many subtler emotions related to sadness, or even just from one of them: loneliness, disappointment, grief, worry just to name a few. But then, deceptively, we can also feel sad just because we simply feel…sad. (I said it was complex.) And for many – depending on your disposition – crying isn’t even exclusive to sadness: we cry when we’re in pain, stressed, angry, frustrated; some even do it when they’re feeling overwhelmed with happiness!

First of all, can you imagine what it must have been like the first time one of our human ancestors ever cried?

Picture it: you’re sat on a savannah somewhere in the heart of early Africa with a member of your group picking at some fruit, and occasionally some bugs off of each other. Perhaps your friend has been feeling a bit distant from the group lately: they’ve been getting a bit less food, a bit less attention. And then, as you’re both sat watching the early human world go by, they suddenly start making alarming snorting noises! Something must be wrong – perhaps they can’t breathe! Are they choking? And then – is that? Water is oozing, no, streaming out of their eyes! Doubtless your friend’s a bit alarmed by this too, but they seem to be just going with it. It’s quite moving actually…

OK, so it probably wasn’t quite like that. Our ability to cry probably came about much more gradually, making for a far less amusing anecdote. Evolution takes time, you see, especially for us humans with our long lifespans and the time it takes us to reach maturity: we’re no Drosophila melanogastar (that’s the humble fruit fly, darling of the genetics lab, to all you non-scientists). We evolve as a species so gradually with the passing of generations that we don’t even notice until a change has been present for a long time, and we can look far back into our history to compare how we used to be.

Humans were first technically able to produce tears purely for the purpose of cleaning the eyes – basal tears – quite early on, as lots of other less complex animals are also able to do this. It’s nothing particularly special; it’s just part of having eyes. It might interest you to know that there are three types of tears: basal, reflex (produced by a well-aimed poke to the eye, or by that meanest of vegetables: the onion) and then there are emotional tears, which as far as we know are exclusive to humans. So, why does liquid coming out of our eyes have anything to do with feeling strong emotion – why not some other behaviour? What was the reason for a connection being made – literally – between our tear ducts and the groups of neurons in our brains associated with our emotions?

Before we look at some ideas and get all excited and carried away with ourselves, it’s important to just bear in mind that while studies into questions like this are great and all, they can be difficult to draw proper conclusions from. It’s hard to truly mimic real life in a lab, and as you can imagine it’s quite difficult to induce true grief in a lab and then measure it (although, thinking back to A level chemistry practicals, I might be tempted to disagree…) Crying on cue is hard enough, let alone when you’re surrounded by a capering bunch of scientists, grinning as they eagerly clutch test tubes ready to catch your tears.

You might think that tears are just salt water, but actually they contain all sorts of chemicals, and emotional tears in particular are noticeably different from basal or reflex tears. They contain more protein; are loaded with hormones, especially those produced when stressed; plus a chemical called prolactin which acts on receptors in the lachrymal glands so that they carry out the brain’s command to ‘release the tears!’ So the chemicals in emotional tears are linked to the moods we feel when we cry. One theory, which I’d like to fondly call ‘flush theory’, suggests that crying is the body’s way of flushing out chemicals present from experiencing strong emotions. And to think the eyes are said to be the windows to the soul – perhaps ‘plumbing’ would have been more accurate, though definitely not quite as romantic.  It’s a nice idea, which ties in satisfyingly with the feeling of release that often accompanies a good cry. However, from a physiological perspective it wouldn’t be the most effective way of getting rid of unwanted chemicals: even a long bout of heart-broken sobbing will only produce about a thimble-full of tears (the thimble, being of course an incredibly accurate and scientific unit of measurement).

Unless you’re a skilled actor, real tears are hard to fake. This means that they can generally be taken as a visual signal of real, genuine feeling and emotion. If you see someone crying they’re sending a sign that you should take their emotion seriously, and this is important for us as animals that have evolved to live in groups and form complex society. Crying puts you in a vulnerable state: in addition to being distracted from watching for predators due to the emotions you’re feeling, it also physically obscures your vision. So when you’re upset and someone comforts you, it’s a demonstration of trust and therefore incredibly risky from an evolutionary point-of-view: you’re laying yourself bare to the possibility that, rather than give you a pat on the back and pass you the tissues, your fellow human could just as easily kill you and steal all your food.  When you’re upset and someone comforts you (if they choose the other option, I think it’s time to look for some new friends) it’s this sharing of trust which allows you to bond together more strongly – and this would have been an advantage for groups of early humans. Crying would have to provide some sort of benefit to outweigh its disadvantage, otherwise most of our weeping ancestors would have been pounced on by leopards whilst they stumbled about with blurred vision, and being human today would be an altogether much more dry-eyed affair. Because tears were potentially dangerous to the individual and so provided this momentary vulnerability to trust others with, it’s possible that this is why we cry when upset rather than, for example, ooze earwax, or wiggle our toes, or laugh or do any other weird alternative behaviour you care to dream up.

To other early humans, our ancestors might have looked a bit ridiculous at the time with their leaking eyes, snotty noses and melodramatic wailing, but on the whole they’d be closer and stick together knowing that they could trust one another to look out for each other. And just maybe, this could have been enough of an advantage that once the tears started, they were here to stay for the rest of human history.