Brain invasion: why music can frighten us

As the Academy Awards roll around again this February to celebrate the cinematic achievements of the past year, relatively little of the red carpet attention will be going to the composers nominated in the Best Original Score category. Working behind the scenes instead of at, or in front of, the camera, these are the creators of the soundtracks which engage and manipulate our emotions and can dramatically affect how we feel. Take John Williams' instantly recognizable theme, for example, which turns a shaky video of a rather peaceful coral reef into a nail-biting introduction to the horror classic, Jaws.

But why does music affect our emotions this drastically? How can a few seconds of a soundtrack send a shiver down our spines, make our blood run cold, and help us completely forget we are being taken in by an illusion? The answer, of course, must lie in our brains, and now a team of neuroscientists at the University of Montreal may be able to throw some light on a crucial piece of the puzzle.

"We know music is very effective at communicating and evoking emotions," said Dr William Aubé, who worked on the team. "We wanted to find out why it is so effective from measuring the brain's responses to music." Part of the challenge here is that it is unclear what (if any) function music could play in the brain, making it difficult to know where to start looking for clues. But what if, the neuroscientists wondered, our brain was in fact sometimes treating music like another, more 'informative' sort of sound, the human voice? "Our brains are predicting machines that help us adapt to the environment," Aubé continued. "We're very efficient at taking information and developing anticipations and expectations to predict what's going to happen next."

In social animals such as humans, this information often comes in the form of noises made by other animals, meaning that there is a potential advantage to recognising emotion in sounds. Being able to perceive fear in another animal from its cries, for example, may be a good predictor that you are imminently in danger from the same threat. If the brain uses the same circuits to listen to music as it does to these sounds, Aubé and his colleagues reasoned, this shared circuitry might partly explain why we hear emotions in music.

To test their theory, the team brought in 47 participants and a functional magnetic resonance imaging (fMRI) scanner for an experimental study. Participants individually lay down inside the scanner and were presented with a randomly ordered series of sounds and pictures from three different groups. The first group contained specially composed, five-second musical excerpts that had previously been classified by an audience as 'fearful, 'happy', 'sad' or 'neutral'. The second group was made up of more five-second 'vocalisations' - wordless sounds made by actors expressing the same four categories (think dramatic screams, chuckles, sobs etc). The last group contained only pictures of faces displaying expressions in each category. During the whole experiment, the scanner measured the level of activity occurring in different areas of the brain.

The resulting images of brain activity revealed exactly the sort of pattern the neuroscientists had been looking for: two regions of the brain showed remarkably similar increases in activity when people were listening either to clips of fearful vocalisations or to frightening music (as compared to neutral clips), but not when they were looking at fearful facial expressions. Both of these regions are already known to be involved in processing emotions from other people's voices, faces and body language. The first region is called the insula, a large folded section of the brain that plays a role in your level of self-awareness as well as what happens when you fall in love. The second, the amygdala, consists of two small, almond-shaped groups of neurons involved in everything from how aggressive you are to how much 'personal space' you like to have between you and other people.

According to this study, the fact that the increase in activity in these two areas was correlated for vocalisations and music suggests that some of our ability to perceive emotions in music - at least, fear - does indeed lie in some of the same circuits that the brain usually uses to recognise emotions in other people's voices. Or in Aubé's words, "it provides some support for the idea that music could 'invade' regions in the brain related to voice processing, which could explain why it is so powerful in communicating emotion. Music is like a 'super-expressive' voice."

However, as the authors acknowledge, this study certainly doesn't give us the whole story. First of all, by using only five-second clips that the participants hadn't heard before, the neuroscientists deliberately measured only the brain's immediate responses to unfamiliar music and vocalisations. Listening to music for a longer time, says Aubé, particularly if it is familiar, engages all sorts of other pathways in the brain, including those associated with memories - making some music emotionally significant for some people and relatively meaningless to others. Just think how strongly your favourite song can affect your mood, or a long-forgotten piece of music can remind you of a certain time or place.

Additionally, the fact that brains only showed a correlated response to vocalisations and music expressing fear, even though people reported recognising both happiness and sadness in other excerpts, could suggest that fear is fundamentally more recognisable in music, compared to other emotions. It could also imply that there are other circuits involved in processing different emotions that the neuroscientists did not observe in this experiment.

Although this study didn't itself test what specifically made a piece of music 'frightening' or 'happy', musicologists studying the properties of emotional music have come up with a number of characteristics that can affect how certain pieces sound to us. For example, music that spends a lot of time in 'extreme registers' - that is, contains mostly very high or very low notes - can cause stress, as does music that is fast and sounds agitated. Various types of 'dissonance', or notes that don't sound pleasant together, can also be unsettling. Meanwhile, slow music in a minor key is often associated with sadness, and fast, high-pitched music in a major key is more likely to be identified as 'happy'. Exactly how music 'expresses' these emotions, and to what degree we are culturally influenced in our responses to different types of music, though, remain a bit of a mystery.

The next step, said Aubé, will be to find out how the parts of the brain identified as important in this study develop from childhood to adulthood. "If, during development, there are some brain regions that gradually get specialised for music, that would be stronger evidence that we have some invasion of sound processing circuits by music," he said. It might also help us to understand whether there is any biological role for music in humans, or whether we simply experience a pleasant coincidence of our brain being taken over by something it confuses with a human voice.

So the next time you're in the cinema and feel the hairs on the back of your neck stand up, remember that those composers on the red carpet might well be taking advantage of your confused brain to trick you into fearing a danger that does not really exist...

As if that will stop you hiding behind the seat in front.