I'm from a fairly traditional family.
So like a good Asian girl, I grew up studying violin and piano,
but I was also expected to take all the premed courses
and go to med school and become a doctor.
But then I went to college,
and in college,
I got really seduced by this idea
of how these seemingly abstract, elusive concepts -
like beauty and truth and love and art and, in particular, music -
could actually be understood using the objective principles of science.
So then I signed up for grad school
to study the cognitive neuroscience of music.
In grad school, I got obsessed with this question of,
Where does music come from?
Music is a multibillion-dollar industry,
and that's because people love music.
People love to rock out at concerts,
and I'd like to think there's something about the musical signal
that appeals to what is uniquely human in each of us.
Of course, this is not just true of the Western world.
This is a picture taken in Mali, in West Africa,
and he's holding this instrument called the ngoni.
And although this seems very foreign,
what his brain does to listen to music
is probably very similar to what our brains do to listen to music.
Furthermore, the physical principles that make his strings vibrate
probably are the same as what makes our instruments vibrate,
like the violin.
Now, we don't just love music; we also know lots of things about music.
Consider, for instance, this musical example.
(Simple chords on a keyboard)
All right. You might say that sounds nice and normal,
kind of like saying, "I took the T here today."
What about this?
(Same chords, the final one discordant)
Right - if you think that sounded normal, come talk to me afterwards;
we might sign you up for that tone-deafness study we're doing.
(Laughter)
When you heard that last chord, your brain does a double take, right?
There's something about it
that's like saying "I took the T here octopus."
Nothing wrong with octopus,
but it just doesn't fit the context of what happened before it;
it doesn't fit the grammar.
Now, this double take that your brain does
can be measured using electrical potentials on the surface of the scalp.
This is a picture of my mom getting her brain potentials recorded,
and she's got 64 electrodes on her cap there,
and what those do is make recordings like this.
And so on the left, I'm showing you
brain responses to expected and unexpected musical chords.
And on the right, I'm showing you the difference
between expected and unexpected on the surface of the scalp -
so this is a bird's-eye view of the scalp.
So right away,
you can see that 200 milliseconds after the onset of the unexpected chord,
your brain does this double take: "Oh, that was unexpected."
In 500 milliseconds, you get the brain saying,
"Oh, how do I integrate that into what happened before?"
So this is telling us, with millisecond accuracy,
that we know about about music;
there's something about our brains that is very sensitive
to what's grammatical in Western music.
So the question is,
Where does this knowledge come from?
How do we come to know what we know?
To answer that question,
we again have to go all the way back to the ancient Greeks.
Pythagoras found that if two strings are being played together
where one string is twice the length of the other
those two sound good together; they sound consonant.
So this two-to-one frequency ratio
is what, supposedly, brought us closer to the Greek gods.
In fact, the word "symphony"
originally means "vibrating in perfect harmony"
using these mathematical integer ratios.
So this two-to-one frequency ratio is true of music all around the world.
Now, different cultures divide that two-to-one frequency ratio
in different ways.
In our culture, the equal-tempered Western chromatic scale
divides them in 12 steps.
So this is how it sounds.
(13 tones covering a 12-note scale)
Okay.
Then two guys came along, said, "Does it have to be this way?
Why two-to-one? Why not three-to-one?"
So the Bohlen-Pierce scale is based on a three-to-one frequency ratio,
and within that, we've got 13 logarithmic divisions of that scale.
So you still get some mathematical integer ratios -
so the Greek gods are not offended here.
But what this sounds like
is completely different from Western or other types of music.
(14 tones covering an alternate scale)
So this is a really powerful approach to find out what people know about music
in the laboratory.
So we can be pretty sure people have never heard this music before,
but they come in, they can listen to this music for a while,
then we can measure how they come to know what they know.
So I'm going to play you, for about a minute,
a snippet of a piece by Stephen Yi.
It's called "Reminiscences,"
and it's written in the Bohlen-Pierce scale,
just so you get an idea.
(Ethereal music)
So this really is kind of an otherworldly new musical experience
that we're entering here,
and in our lab, what we wanted to do
was figure out how people learn this new musical system.
So we have these well-controlled melodies
that people listen to for about half an hour.
(Atonal note progression)
So you listen to these things for half an hour,
and they're defined using rules and principles,
or grammatical structures,
that we've defined ourselves.
And then the question is,
What can people learn from this new musical experience?
First thing we found was that memory increases with repetition.
Turns out, also, that preference increases with repetition.
So what we're seeing is the beginning of musical taste, right?
The more you listen to something, the more you begin to like it.
But I'm interested in how learning occurs.
It turns out that learning does not occur with repetition
but with variability.
In other words, the more ways you tell people something,
the more people are able to infer
the underlying structure of what you tell them
and then to generalize those to new instances of the same grammar.
Our question becomes, now,
We've got 100 trillion neural connections to the brain;
how did those 100 trillion neural connections
give rise to what we know and love in music?
Right now, these neural connections are in the order of nanometers,
but what we can image using the living human brain,
using this technology called "diffusion tensor imaging,"
is large bundles of these neural connections -
so highways, if you will.
And the highway we're most interested in is called the arcuate fasciculus
and it's known to be important in language.
But what we saw is the larger of an arcuate fasciculus you have,
the better you are at learning this new musical system.
So there's something structurally different
about a good and a not-so-good learner's brain.
But what's important is that these pathways
that are previously known to be important in language
are actually important in music as well.
So this tells us that there is no single center for music
or there's no one center for music in the brain.
But what we do have are these shared neural networks
that are important in language and in grammar and in expectation
and all these things that actually make us human.
So I think music -
that's actually why people like music.
It's not because it's this individualized stereotyped activity,
but it's something that tickles all the different cognitive components
and neural mechanisms that we already have.
Now, that sounds good,
but can we actually observe the brain as it is learning in real time?
So we go back to the millisecond-accuracy kind of brain-potential recording,
and it turns out that our brains respond to new music
in very much the same way as it does to Western music.
So we get the same expected-unexpected pattern
200 milliseconds and 500 milliseconds
after the onset of anything that sounds unexpected.
And furthermore, our brains respond more and more towards these expectations
throughout the course of an hour,
so as if within an hour,
we're getting more and more experts in the Bohlen-Pierce scale.
So there's no rules of music that are written in our brains,
but what we do have that are in our brains is the immense ability to learn.
So we are fundamentally open-minded creatures.
So what does that mean if we want to go back to West Africa?
I invite you to take off your headphones
and actually experience the new musical world.
Try to come up with the grammar of this seemingly foreign country.
You know, so, and what about even just being here today?
How about change your radio channel or listen to a new musical artist today?
There's something about experiencing new things
that, to me, is what it means to thrive
because to thrive is to maximize our potentials as human beings, right?
It's not to do the same thing over and over every day,
but it's to seek out new experiences,
and what I've shown you today
is that the brain is fundamentally capable of learning new things.
We can take - even within an hour,
we can have this flexible, adaptive ability
to make sense of new sounds.
So I invite you to listen to new sounds,
see new sights
and come up with the grammar of the world that's around us
so that we can learn to love it.
Thank you very much.
(Applause)