Have you ever accidentally pulled your headphone socket out while listening to music? What happens when the music stops? Psychologists believe that our brains continuously predict what is going to happen next in a piece of music. So, when the music stops, your brain may still have expectations about what should happen next.
A new paper published in NeuroImage predicts that these expectations should be different for people with different musical experience and sheds light on the brain mechanisms involved.
Research by Marcus Pearce Geraint Wiggins, Joydeep Bhattacharya and their colleagues at Goldsmiths, University of London has shown that expectations are likely to be based on learning through experience with music. Music has a grammar, which, like language, consists of rules that specify which notes can follow which other notes in a piece of music. According to Pearce: "the question is whether the rules are hard-wired into the auditory system or learned through experience of listening to music and recording, unconsciously, which notes tend to follow others."
The researchers asked 40 people to listen to hymn melodies (without lyrics) and state how expected or unexpected they found particular notes. They simulated a human mind listening to music with two computational models. The first model uses hard-wired rules to predict the next note in a melody. The second model learns through experience of real music which notes tend to follow others, statistically speaking, and uses this knowledge to predict the next note.
The results showed that the statistical model predicts the listeners' expectations better than the rule-based model. It also turned out that expectations were higher for musicians than for non-musicians and for familiar melodies -- which also suggests that experience has a strong effect on musical predictions.
In a second experiment, the researchers examined the brain waves of a further 20 people while they listened to the same hymn melodies. Although in this experiment the participants were not explicitly informed about the locations of the expected and unexpected notes, their brain waves in responses to these notes differed markedly. Typically, the timing and location of the brain wave patterns in response to unexpected notes suggested that they stimulate responses that synchronise different brain areas associated with processing emotion and movement. On these results, Bhattacharya commented, "… as if music indeed 'moves' us!"
These findings may help scientists to understand why we listen to music. "It is thought that composers deliberately confirm and violate listeners' expectations in order to communicate emotion and aesthetic meaning," said Pearce. Understanding how the brain generates expectations could illuminate our experience of emotion and meaning when we listen to music.
- Pearce MT, Ruiz MH, Kapasi S, Wiggins G, Bhattacharya J. Unsupervised statistical learning underpins computational, behavioural, and neural manifestations of musical expectation. NeuroImage, 2009; DOI: 10.1016/j.neuroimage.2009.12.019
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