There’s an interesting new paper on how the brain makes sense of music by constructing detailed models in real time. The act of listening, it turns out, is really an act of neural prediction. Here are the scientists, from the University of London:
The ability to anticipate forthcoming events has clear evolutionary advantages, and predictive successes or failures often entail significant psychological and physiological consequences. In music perception, the confirmation and violation of expectations are critical to the communication of emotion and aesthetic effects of a composition.
The paper consists of a computational model and and an experiment. The model essentially demonstrated that statistical predictions based on our personal listening experience – because I listen to Bruce Springsteen, I’m able to predict the melodies of John Mellencamp – was much better at simulating the mind than a rule-based model, in which our expectations are fixed and inflexible.
The experiment was more compelling. The scientists measured the brain waves of a twenty subjects while they listened to various hymns. It turned out that unexpected notes – pitches that violated the previous melodic pattern – triggered an interesting sequence of neural events and a spike in brain activity:
Our electrophysiological results showed that low-probability notes, as compared to high-probability notes, elicited a larger (i) negative ERP component at a late time period (400-450 ms), (ii) beta band (14-30 Hz) oscillation over the parietal lobe, and (iii) long-range phase synchronization between multiple brain regions.
There are two interesting takeaways from this experiment. The first is that music hijacks some very fundamental neural mechanisms. The brain is designed to learn by association: if this, then that. Music works by subtly toying with our expected associations, enticing us to make predictions about what note will come next, and then confronting us with our prediction errors. In other words, every melody manipulates the same essential mechanisms we use to make sense of reality.
The second takeaway is that music requires surprise, the dissonance of “low-probability notes”. While most people think about music in terms of aesthetic beauty – we like pretty consonant pitches arranged in pretty patterns – that’s exactly backwards. The point of the prettiness is to set up the surprise, to frame the deviance. (That’s why the unexpected pitches triggered the most brain activity, synchronizing the activity of brain regions involved in motor movement and emotion.) I wrote about this concept in Proust Was A Neuroscientist:
Before a pattern can be desired by the brain, it must play hard to get. Music only excites us when it makes our auditory cortex struggle to uncover its order. If the music is too obvious, if its patterns are always present, it is annoyingly boring. This is why composers introduce the tonic note in the beginning of the song and then studiously avoid it until the end. The longer we are denied the pattern we expect, the greater the emotional release when the pattern returns, safe and sound. Our auditory cortex rejoices. It has found the order it has been looking for.
To demonstrate this psychological principle, the musicologist Leonard Meyer, in his classic book Emotion and Meaning in Music (1956), analyzed the 5th movement of Beethoven’s String Quartet in C-sharp minor, Op. 131. Meyer wanted to show how music is defined by its flirtation with–but not submission to–our expectations of order. He dissected fifty measures of Beethoven’s masterpiece, showing how Beethoven begins with the clear statement of a rhythmic and harmonic pattern and then, in an intricate tonal dance, carefully avoids repeating it. What Beethoven does instead is suggest variations of the pattern. He is its evasive shadow. If E major is the tonic, Beethoven will play incomplete versions of the E major chord, always careful to avoid its straight expression. He wants to preserve an element of uncertainty in his music, making our brains beg for the one chord he refuses to give us. Beethoven saves that chord for the end.
According to Meyer, it is the suspenseful tension of music (arising out of our unfulfilled expectations) that is the source of the music’s feeling. While earlier theories of music focused on the way a noise can refer to the real world of images and experiences (its “connotative” meaning), Meyer argued that the emotions we find in music come from the unfolding events of the music itself. This “embodied meaning” arises from the patterns the symphony invokes and then ignores, from the ambiguity it creates inside its own form. “For the human mind,” Meyer writes, “such states of doubt and confusion are abhorrent. When confronted with them, the mind attempts to resolve them into clarity and certainty.” And so we wait, expectantly, for the resolution of E major, for Beethoven’s established pattern to be completed. This nervous anticipation, says Meyer, “is the whole raison d’etre of the passage, for its purpose is precisely to delay the cadence in the tonic.” The uncertainty makes the feeling. Music is a form whose meaning depends upon its violation.