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How Our Brains Create Meaning From The Sounds Around Us

ARI SHAPIRO, HOST:

As the sounds that I'm making right now enter your ear, your brain is effortlessly turning those air vibrations into a sentence that has meaning. Now, if we start to distort my voice, your brain has a harder time deciphering what I'm saying. And if we auto-tune my words, turn them into music and put a beat under them...

(SOUNDBITE OF MUSIC)

SHAPIRO: ...Your brain processes this sentence in still different ways. So what exactly is going on in your brain to make sense of those sounds? Well, that's the focus of neuroscientist Nina Kraus' new book "Of Sound Mind: How Our Brain Constructs A Meaningful Sonic World." Welcome to ALL THINGS CONSIDERED.

NINA KRAUS: Oh, thank you. I'm glad to be here.

SHAPIRO: Well, let's talk about those two examples to start. As my voice distorted there, what was actually happening in our brains?

KRAUS: Well, you know, our brain does a really good job picking up what is going on in our sonic world. And so if we're getting garbled information, if we're getting information that has background noise, it's going to affect the signal that the brain hears in the first place. That said, each one of our brain - our hearing brains is different, and it will process the information that we hear based on our life in sound. As we have, throughout our lives, made sound to meaning connections, eventually much of what we do happens automatically.

SHAPIRO: Well, let's talk about that experience. You write that in your biography, there are at least a couple of things that make your brain different from other people. For example, you were raised in a bilingual household. Your mother was a pianist. How did growing up with those kinds of features change your brain or anyone's brain, for that matter?

KRAUS: It's hugely important. Music is really the jackpot if you think about the hearing brain. So the hearing brain engages how we think and feel, what we know, what we remember, how we move, how we interact with our other senses. So if, as a child, you know, you have made music and you have associated musical meaning with the ones you love and feeling safe, you're going to develop a nervous system that reflects that experience.

SHAPIRO: You've also researched the connection between music and emotion. And you spoke about this at an event a few years back with the opera singer Renee Fleming, where she sang "Song To The Moon" from the opera "Rusalka" by Antonin Dvorak. Let's listen first to a bit of this piece of music.

(SOUNDBITE OF SONG, "SONG TO THE MOON")

RENEE FLEMING: (Singing in Czech).

SHAPIRO: The beauty of this seems almost to defy science. And yet you are a scientist who has studied, among other things, why this feels beautiful, why this feels emotionally compelling. What can you tell us?

KRAUS: Well, you know, it brings back - just listening to this brings me back into the moment.

(SOUNDBITE OF SONG, "SONG TO THE MOON")

FLEMING: (Singing in Czech).

KRAUS: When you're listening to a beautiful piece like the "Song To The Moon," your limbic system is being activated by sound. And it will also be producing dopamine that will occur, if you know the piece, as you anticipate what's coming. And also, when you reach the musical climax of the piece, then the dopamine will be increasingly released.

(SOUNDBITE OF SONG, "SONG TO THE MOON")

FLEMING: (Singing in Czech).

KRAUS: So, again, one's experience with sound is going to affect that reaction that one will have when listening to a beautiful voice like Renee's.

SHAPIRO: You run a lab at Northwestern University called Brainvolts where you research the connection between sound and the brain, some of these issues we've been talking about. And you brought a demonstration that sort of vividly portrays some of your research's findings. Can you walk us through it?

KRAUS: OK. So listen to this sound, and see if you can figure out what words are being said.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: The juice of lemons makes fine punch.

SHAPIRO: Wow. That sounds incomprehensible.

KRAUS: Now listen to what the sentence actually is when it's not garbled.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: The juice of lemons makes fine punch. The juice of lemons makes fine punch.

KRAUS: Now listen to the first sentence again.

(SOUNDBITE OF ARCHIVED RECORDING)

UNIDENTIFIED PERSON: The juice of lemons makes fine punch. The juice of lemons makes fine punch.

SHAPIRO: Now it sounds totally clear. I absolutely hear, the juice of lemons makes fine punch. What are you showing us there?

KRAUS: All right, so do you believe me that what you know about sound influences how you make sense of it?

SHAPIRO: Interesting. Our previous experience shapes our interpretation of the sounds we encounter in the world.

KRAUS: Bingo.

SHAPIRO: So your research can actually show us what the brain experiences when it encounters sound. How does that work?

KRAUS: Absolutely. As I'm talking to you now, the neurons in your brain that respond to sound are producing electricity. And with scalp electrodes, we can measure that electricity. I can then sonify it so that we can listen to what your brain produced when it was listening to whatever it was that you were listening to. And what is remarkable is that when we play back the brain's response to sound, it will actually physically resemble the sound that stimulated the brain in the first place.

SHAPIRO: OK, let's do it. What do you want to play for us?

KRAUS: So here is a person listening to "Amazing Grace." So here's the sound that we're hearing.

(SOUNDBITE OF MUSIC)

KRAUS: And this is the response that we captured as they were listening to this particular clip of "Amazing Grace."

(SOUNDBITE OF MUSIC)

KRAUS: Pretty recognizable, right? So we have so much to work with. We can listen to this person's response to sound, so you can imagine we can compare different kinds of people and different kinds of brains. Another really nice example that I have is three healthy brains listening to "A Hard Day's Night." Listen to how three different healthy brains process that sound - brain one.

(SOUNDBITE OF BEATLES SONG, "A HARD DAY'S NIGHT")

KRAUS: Brain two.

(SOUNDBITE OF BEATLES SONG, "A HARD DAY'S NIGHT")

KRAUS: Three.

(SOUNDBITE OF BEATLES SONG, "A HARD DAY'S NIGHT")

KRAUS: So I think it's a really compelling point that each one of us hears the world differently. And here is a biological example of how this is the case.

SHAPIRO: That's neuroscientist Nina Kraus. Her new book is "Of Sound Mind: How Our Brain Constructs A Meaningful Sonic World." Thanks a lot.

KRAUS: You're welcome. Thank you so much.

(SOUNDBITE OF BEATLES SONG, "A HARD DAY'S NIGHT") Transcript provided by NPR, Copyright NPR.

Corrected: September 28, 2021 at 9:00 PM PDT
An earlier version of this transcript mistakenly said Renée Fleming was singing in Russian. She is singing in Czech.