Ulrich Pomper, Makoto Yoneya, Maria Chait
As part of
the Guardian’s ‘Brain waves’ project we measured brain responses from singers
Laura Mvula and Billy Bragg while they were listening to a self-selected,
particularly emotionally meaningful song.
In a nutshell: We focused on the effects of music familiarity on the brain’s response. Our measurements demonstrate that both Laura and Billy's brains reacted very differently to the familiar and unfamiliar music. Brain responses and pupil dialation data suggest that Laura and Billy's brains distinguished the familiar from the unfamiliar snippets within 1/10 of a second. The unfamiliar snippets evoked more activity suggesting they required more 'brain energy' to process. These are observational data (no statistics have been performed) and must be verified using a larger group of participants.
To investigate Laura and Billy’s brain response to their chosen song we used two methods: EEG and Eye-tracking (see side-bar).
Because of the particular strengths and weaknesses of EEG and eyetracking, we decided to focus on the effects of music familiarity on the brain’s response. Will Laura and Billy’s brains react differently to familiar and unfamiliar music? How quickly will the differentiation happen?
For both Laura and Billy, we first we selected a second song which was unknown to them, but which was very similar in style, tempo, and instrumentation to the chosen song. We then cut both songs into very short snippets of less than a second (750 milliseconds) and then played back those snippets in random order. We were interested to see how fast their brain would differentiate between their favourite song which they know very well, and an unknown song which still sounded very similar. This may be akin to zapping through radio or TV programmes, immediately deciding on whether you want to stay and listen or move on.
The figures and results presented below are based on relatively little data, as well as representing single subjects rather that group averages over many subjects. While they are interesting and well in line with many previous studies, it is important to stress that the analyses are exploratory in nature. We are excited to investigate this systematically on a larger group of participants and will continue updating this page with data as it becomes available.
Brain activity measured from Laura and Billy showed the characterisitc pattern we normally observe in response to short sound snippets. However, the brain responses to the unfamiliar song appear larger (in amplitude) than those to the familiar song. This can mean that more nerve cells were active (in a more coherent and organized manner) when processing the unknown song. What was striking is how fast the brain responses differed between the two songs. The first peak showing a difference appears already a tenth of a second (100 milliseconds) after the snipped started, which is remarkable.
Likewise we see a much stronger change in the pupil size following the unfamiliar compared to the familiar song. This stronger response can be interpreted similarly to the EEG effects above: Surprise, novelty, and a violation of expectations. It might be that processing the new sounds in the unfamiliar song is more difficult and uses up resources in the brain, leading to a stronger pupil response. The familiar song on the other hand is very easy and straightforward to process, because it has been heard hundreds of times before.
We also examined a second aspect of the EEG data: ongoing rhythmic activity. These ‘brain rhythms’ can be indicative of the general state of the brain. For example they differ strongly between being awake and fresh, being very tired, being asleep, or performing meditation. We see that a characteristic brain rhythm, the ,alpha rhythm’ at about 10 cycles per second, differs strongly between listening to the familiar compared to the unfamiliar song, for both Laura and Billy. If a part of the brain exhibits a strong alpha rhythm, this is generally interpreted as a sign that this part of the brain is disengaged and less active, compared to when it shows less alpha rhythm. The fact that we see less alpha for the unfamiliar song again suggests that both Laura’s and Billy’s brains are actively attending to the unknown sounds and trying to make sense of them.
Another potential interpretation is that listening to their preferred and highly familiar songs has a relaxing and partly disengaging effect on their brains. This fits with Billy’s feelings toward ‘Willin’, but potentially also with the fact that Laura’s song is a lullaby which she associates with a calm and relaxed state.
As a control we presented the stimuli used in Billy's experiment to 3 naive participants (who were unfamiliar with both songs). Their brain responses did not differ between the two songs suggesting that the effects observed above are indeed linked to familiarity and not due to other acoustic differences between the signals.
* Due to video time constraints the Billy video was focused on the fMRI results from our colleagues at Birkbeck.