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)