Transcript

Kim Mills: Music, conversation, birdsong, a truck backing up, the hum of a refrigerator, the leaf blower across the street. We live in a world of constant complex sound, yet most of us don't spend very much time thinking about the role that sound plays in our lives. Polls find that most people, when asked to rank their senses, value sight the highest with hearing a distant second. But sound is integral to our lives, even to our mental health. And no two people's sonic world is exactly the same. Our life experiences shape the way that our brain processes sound. And sound is deeply intertwined with everything from our ability to read, to our cognitive health as we age.

So why is sound so undervalued, especially by those of us who can hear? How does our brain turn sound waves into brain waves? Do the brains of musicians differ from those of non-musicians? Why is sound crucial to reading? Do other animals experience sound in the same way that humans do? How does unwanted noise affect our ears and our brain? Why does our hearing change as we age? And what can all of us do to create a better, healthier sonic world?

Welcome to Speaking of Psychology, the flagship podcast of the American Psychological Association that examines the links between psychological science and everyday life. I'm Kim Mills.

My guest today is Dr. Nina Kraus, director of the Auditory Neuroscience Lab, also known as Brainvolts, at Northwestern University. She's a scientist, inventor, and amateur musician who studies many aspects of auditory learning. The list of her research topics includes music, concussion, bilingualism, reading, aging, and autism. She has invented new ways to measure sound processing in humans and has conducted studies in traditional research labs as well as in schools, community centers, and clinics. She is the author of hundreds of peer-reviewed research articles and speaks frequently to the media about sound and the brain. Her recent book is called Of Sound Mind: How our Brain Constructs a Meaningful Sonic World.?

Thank you for joining me, Dr. Kraus.

Nina Kraus, PhD: I'm so glad to be here. Thanks, Kim.

Mills: A moment ago, I mentioned that people tend to rate sight as their most valued sense, far ahead of hearing. Why do you think that hearing is so much less valued?

Kraus: Well, for one, it's invisible, and what we can see is right in front of us. What we can hear actually is all around us 360 degrees, but we live in a visually biased world. And I think also as time is going on, we're forgetting how to listen and how important hearing is. Sound very much connects us. It connects us with others, it connects us with the world in a way that is really different from the way we are connected with our other senses. Sound is evolutionarily ancient. Sound processing in the brain really derived from primitive organisms, from cells that would move with vibration. And eventually in vertebrates we have a complex auditory pathway, but the fundamentals of hearing and the vibrations that we are able to discern and that any organism can discern is evolutionarily ancient and biologically important.

Mills: Now, you spend the first third of your book explaining the basics of how sound works, how the ear and the brain convert sound waves into brain activity. What makes sound unique in terms of how it's processed in the brain?

Kraus: Well, first of all, even though the speed of light is faster than the speed of sound, the way we process sound in the brain is faster. And if you can imagine, so right now as we're having this conversation, sound waves are occurring, and within every sound wave there is a tremendous amount of information that is happening in time. It's here and then it's gone. It only is present for a second or for a millisecond, frankly. And whereas what we see is something that is much more stable in terms of timing, so that the timing requirements are going to be different. The brain needs to make sense of sound similarly to how we make sense of a visual object. There are many ingredients that we right away are able to discern: What is the shape, the size, the color, how heavy is it?

And with sound, remember sound first of all is invisible and all of the ingredients are also invisible, but they are there. So if we give it a thought, we realize that sound consists of pitch. How high or low the sound is. It consists of timbre. Timbre is determined by the harmonics in sound. Timbre is what allows us to tell the difference between two different instruments that are playing the same note. The harmonics enable us to distinguish one consonant from another, a “ga” from a “ba.” There is so much timing in every single wave form. And, Kim, you are actually looking at these wave forms and you can see how they stop and start, and how they have so many timing elements that the brain needs to make sense of. So the brain is processing pitch, timing, timbre, phase, other ingredients with microsecond precision and the signal, the sonic signal, the sound wave requires that that be done.

Mills: Let's talk for a minute about the connection between sound and language, especially reading. People tend to think of reading as a visual activity, but your research has shown that sound is critical to our ability to read. Why is that?

Kraus: Well, it's not just my research. There really has been decades of research showing that sound is critical to the ability to read. So why is it that we learn to speak before we learn to read? And again, if we draw on evolution, think about the fact that we have been speaking and using sound for hundreds of thousands of years for communication. We've only been reading for the past 3000 years. And in fact, Socrates was concerned that we would lose our ability to remember because sound and memory are very, very, very closely tied. But first of all, we have to make sound-to-meaning connections when we learn to talk. So that's the first thing that happens. And then if we have made strong sound-to-meaning connections, then it will be easier for a child or anyone to connect the sounds with a symbol on a page, a letter, and we can measure sound processing in the brain.

So as I'm talking to you now, the neurons in your brain that respond to sound are producing electricity. And with some scalp electrodes, we can measure your brain's response to sound and we can figure out how good a job your brain is doing at processing all those different sound ingredients that I spoke of. Pitch, timing, timbre, phase. And we can see where are the strengths, where are the bottlenecks? And we can see that in children who have difficulty reading and who have delayed language skills, we typically see that aspects of timing and of the processing of the harmonics, which of course really do enable us to distinguish one consonant from another.

I use the metaphor of the brain as mixing board. So imagine this complex sound that has all the different ingredients is coming into your head and then your brain is a mixing board where the faders go up and down on these different ingredients, pitch, timing, and timbre. And if you have difficulty reading the slider, the fader on the harmonics, fader is going to be low and certain aspects of timing is going to be low. And so we can see, oh, there actually is a bottleneck. All you can see is, oh, here's a child who has difficulty learning to read. You don't know what's up with them. If you measure their sound processing, you can see, well, actually there's nothing wrong with their sound processing. Everything's perfect. Or you can see, well, there really are some bottlenecks and that can guide us in many ways.

Mills: So what happens with people who are congenitally deaf, then how do they learn to read? Does their brain have to work in a different way?

Kraus: Yeah, it can work in a different way. And now many people who are congenitally deaf get cochlear implants which enable them to actually bypass the ear and stimulate the hearing nerve, stimulate the brain directly, but they're still getting information from sound. So they're still making the same sound to meaning connections and would learn reading in much the same way. That said, if a person is not hearing at all, if they really are born congenitally deaf and they remain deaf, we know that the brain is remarkably plastic and able to change based on what inputs it's getting. So that if the sonic inputs are nonexistent, then other parts of the brain will develop and will become stronger, and learning to read and learning many other things can be done through these other channels.

Mills: And then if you put electrodes on the head of somebody who's congenitally deaf and trying to understand what it is that they're processing, I mean, do you get some kind of reading? Because I've seen the readings that you get from people who two people hear the same thing. I think you've got the example of a Beatles song that's being played for two people and then you can play back what it is that they've actually heard. And it's remarkable. I mean it sounds just like the Beatles, but what do you get if you're dealing with somebody who really does not hear?

Kraus: Well, we haven't done that experiment and it's probably one we should do. We have done actually quite a bit of work in people who are hearing impaired. So we can see that the people who have a significant hearing loss and especially one that they've acquired throughout their life, they have learned because the hearing brain is vast. And we can see people—I mean, just last week we had an 86-year-old musician with a very severe hearing loss in both of his ears and his sound processing was remarkably excellent.

Because here's the thing. The hearing brain is vast. So the hearing brain engages how we think, how we feel, what we know, what we remember, what we pay attention to, how we integrate our other senses. So this is the hearing brain. This is the brain that responds to vibrations. Think of Beethoven. Beethoven was deaf and composed some of the very best music that we have in our world because the hearing brain is vast, the hearing brain is vast. And this is, it's counter to the way many people think about the senses. They think about the senses as being these parallel things. They think about what we know, how we feel, even our psychological state. All of that is really part of how we sense the world and how the hearing brain in particular pulls together information from all of these sources in order to make sense of the world.

Mills: In the book you talk about how several different types of expertise seem to give people a kind of auditory advantage. You've done research with musicians, athletes, and people who are bilingual. And what's really fascinating is that in all of these cases, these different skills seem to make people better at processing sound, but in different ways. Can you talk about that, how these different types of expertise in music, language and athletics affect the hearing brain?

Kraus: The punchline is we are what we do and our lives and sound shape our brains. They shape who we are. So if I am a musician, I will have learned. And as we measure sound processing in the brain across musicians, across the lifespan, what we see is that actually the processing of the harmonics and of timing are especially enhanced. They're especially strong. Remember those are the ingredients of sound that we need for language. So by strengthening your music skills, you are strengthening your language skills.

If you speak another language, what we see is that the strength of the fundamental frequency, which is often associated with the pitch of a sound. For example, there's a certain pitch associated with your voice, Kim, and with mine. And we think of auditory objects. There is a fan whirring, or any kind of sound that you can think of often has a pitch and it has a fundamental frequency. And it turns out that if you speak another language, your processing of that component of sound, that ingredient of sound, is really strong, which helps you distinguish one person speaking from another, for example. Because if you speak another language, you always have the languages you know, they're all in your head at the same time. But you get really good at distinguishing sound based on the fundamental frequency.

If you are an athlete, you have an especially quiet brain. So all of us, I mean, our neurons right now are firing. The brain is always on and there is static electrical activity that happens constantly in the brain. But we have learned, and this is through work that we've done with Northwestern University's elite, Big 10 Division 1 athletes. We have a grant that the NIH is funding to study these athletes over five years. And that's 500 of them, males, females, across different sports. And what we find is that in healthy athletes, the noise, the background noise is suppressed. And so if you think of a signal being a sound that you want to hear and the noise being the impediment, they are able to engage with the world better because their senses, if you will, are heightened.

Mills: I think you also found that it doesn't really matter what sport that you're participating in. So while you could be a football player and there's a whole lot of noise happening on the field and you've got to be able to focus on what your colleagues are saying or what your coach is saying from the sidelines. But somebody who runs cross country, which is a very solo kind of effort, that they still have the same kind of brain. That's fascinating how that has happened. Do you understand the ideology of that?

Kraus: Again, because sound and the hearing brain is so associated with movement and being very attuned to—When you're running, you're hearing the sounds that your footfalls are making. You know if you're running a certain way that feels good, that is efficient, you're getting sensory feedback all the time. You're looking around you, where are you placing your body? So I think any kind of deep athletic experience is going to require focused attention on the sensory environment.

Mills: Let's talk about noise. You make the case in the book that exposure to unwanted noise harms not only people's ears but their brains. Why is that? What's happening to us when we are encountering noise?

Kraus: I think there is rising awareness that very loud sounds are bad for our ears and can damage our hearing as far as our ear is concerned. But there is very little awareness of the really terrible impact that our noisy world can have on our brain. So I'm talking about sound that is moderate level intensity. You mentioned the truck at the beginning in your intro. If there's a truck idling outside, I will not pay attention to it, I'll just be talking to you. But when it turns off, when the guy cuts the ignition, I kind of go, “ah.” And the same is true, you're in your kitchen and the refrigerator cycles off. So we didn't even realize that we're stressed.

I do think that the extraneous noises that we have in our lives, many of which can be changed, can be eliminated, contribute to our feelings of stress, because hearing is our alarm sense. Again, from evolution, we know that hearing is what tells us if the sound I'm hearing, can I eat it? Can I mate with it? Do I need to run away? This is very, very, very important information for survival. So we're all under this low-level stress because of the sounds that we're hearing. Also, sound distract us. So every time we get a notification of some kind, every time your neighbor is opening their car door and you hear these constant sounds, they distract your focus. So we hear many people saying these days, “I feel stressed and I can't seem to focus.” And I think that a lot of good could come of honoring and being aware of how bad the effects of living in a noisy place and that noise in general has on the hearing brain and on our ability to make sense of the world around us.

Mills: So how is this noise pollution affecting other animals? I mean, I think you've done some looking into what's happening to the other creatures around us who are maybe suffering from all the noise pollution that we're creating.

Kraus: So much. Underwater animals, whales, dolphins, they all communicate with sound. Shipping, oil well digging, all of that really gets in the way of animal communication. And there were some wonderful experiments that were done during the first couple weeks of the pandemic when, for example, shipping ceased. Also, people were noticing how you could hear the birds. And it wasn't because it was quieter. The birds were actually singing at a lower volume, but they were singing at a lower volume because they no longer had to compete with the racket that we humans are making. And so they were producing quieter songs, but songs that were richer in texture. And the success of a species depends on—Well, in birds, the male bird sings and the female bird chooses. So if the male is able to sing a fancier song, he's going to likely get more female companions. But this is so important, it's important for plants, it's important for the life in the soil. The sounds that we make affect most living things. So we are harming ourselves and we are certainly harming other living creatures and their ability to know where they are to go about their business of thriving.

Mills: In your book you also talk about the connection between sound and rhythm and how important that is. And certainly it makes a big difference in how humans communicate, but I thought it was really interesting how animals use rhythm as well. But not very many animals have rhythm. Why is that? And the animals that have rhythm, where do they get it from? Where do we get it from? And the fact that you can't make a chimpanzee dance, but a cockatoo may dance to music. Why?

Kraus: Everyone knows that there is rhythm in music and there's so much rhythm in language. Rhythm tells us when things stop and start. Every Martin Luther King Day, my husband and I listen to his I Have a Dream speech. And the rhythm, it's a song in his voice, is really what carries you. It integrates the experience tremendously because there're also rhythms, there are rhythms outside the head, there are brain rhythms inside the head. If I were reading you his speech just in the way I normally would be reading a recipe, you'd be looking at your watch, you wouldn't want to be listening to that. And it turns out that kids who have difficulty moving and tapping to a beat can have some language problems.

You asked about other animals. It seems that rhythm is especially important in animals that do vocal learning. So some birds and bats and many sea creatures, whales, these are animals that can move rhythmically and they also learn by imitation. They learn by imitation. And so the rhythm seems to be an important part of this and something that we have been very interested in. We find that if a child has a music education and makes music, their rhythm skills are enhanced as their brain rhythm skills are enhanced. And some of the language benefits that we see with music are coming from rhythm, but rhythm has a wonderful synchronizing part of it. I mean, just inherently we synchronize and neurons inherently when they are firing together, they synchronize. You have the synchrony of neural activity.

One of the things that I hadn't mentioned is that making sense of sound is one of the hardest jobs that we ask our brain to do. It requires this microsecond timing precision. So if you get hit in the head, for example, if you have a concussion, you're going to disrupt this sound processing. And some of the work that we have been doing is showing how it is that if you have sustained a concussion, sound processing is disrupted. We can measure this automatically. It can give us a lot of information about the status of an athlete's injury, can help us inform return-to-play decisions, can help us monitor treatment, all kinds of things. But why am I saying this? Because it relates to rhythm.

We have some early findings showing that rhythm skills are disrupted after you've had a concussion. And so rhythm training is something that is a way in which we can use our hearing brain to improve brain health. This has certainly been shown in many neurological disorders. So rhythm is fundamental for health and for communication.

Mills: And related to that, we were talking a few moments ago about the types of expertise that seem to give people an auditory advantage, and one of those is studying music. Does listening to music have the same effect on people's brains?

Kraus: It doesn't have the same effect. Surely it has some effect, but the ones that we have studied are who have you become based on your life and sound? So the things that you do a lot of, the languages that you speak, the music that you make, when you actively learn a musical instrument, it doesn't matter if you're good or not. But if you spend some time making music, you are making these deep sound-to-meaning connections. You are engaging your vast hearing brain, which engages our cognitive sensory motor and reward systems. So we are able then to strengthen our ability to process sound even when we are asleep.

For example, you pay attention to the sounds that are important to you. If you're asleep and I put scalp electrodes on your brain, we will measure a response when we say “Kim,” because you have learned that that is a sound that is worth paying attention to. We learn based on what we do. We automatically learn to process sound differently. And this is what we have learned with playing either a musical instrument. Singing of course counts, but as far as listening, just listening. I like to say that you're not going to get muscles, you're not going to become physically fit watching sports. So actually partaking in the sports will fundamentally change you. And I believe at least this is what we have seen, that making music will fundamentally change how your brain automatically processes sound.

Mills: Well, last question. I know we could go on and on, but I know we do have to wrap this up. So I'm going to ask you what recommendations you would give to our listeners who want to think more carefully about how they arrange their sonic world and maybe make some improvements to it overall.

Kraus: My recommendations based on, I'm a biologist, based on the biology that I live and breathe every day, is strengthen the sound mind. Strengthen the sound mind by making music, by learning languages, by being a bird watcher, which is of course you're listening, and read to your kids. I so often see parents on their phone and they're walking with their kid and I'm thinking, “Talk to your kid, don't talk to your phone.” What is so important about sound is that sound connects us, sound connects us. So use this ability to connect with your loved ones. I teach them how important that kind of connection through sound is.

And with respect to noise, ask yourself, “is this noise necessary?” I can turn the thing off on my car door so that it won't beep every time I open and close a door. There are things that our society really should be paying attention to. For example, if you think of an airport, that's a noisy place, or even a grocery store. So inherently, there's going to be sounds which are perfectly necessary sounds, but every time you scan a barcode, do you need to hear—And think about the poor person who is on the other side of that all day long. I mean, you're just enduring it for a little while.

Similarly, what if it's fall now and the days have been so wonderful, and the leaf blowers are ridiculous in terms of the amount of noise. And how anyone in our community can on the one side of their mouth say that they are concerned about global warming, and on the other hand, condone using these leaf blowers. I don't understand. But the fact is that even if they are a block away, I don't even see them, you have this droning that is going on like the truck that is impeding our ability to focus and think. And so to the extent that we can take a stand in our personal lives, in our educational lives, in our lives with medicine, and really think about the importance of sound, how important it is for our health in so many ways. There really are ways that we can strengthen our sound mind and that we can think of ways to keep it as healthy as possible.

Mills: Well, thank you. I appreciate very much you're taking the time to talk to me today. I want to assure you that I have a rake and that's what I've been using on my leaves and will continue to do so. But thank you, Dr. Kraus. It's been really interesting.

Kraus: And that's a nice sound.

Mills: It is. It is.

Kraus: Thanks, Kim.

Mills: You can find previous episodes of Speaking of Psychology on our website at www.speakingofpsychology.org or on Apple, Stitcher, or wherever you get your podcasts. And if you like what you heard, please leave us a review. If you have comments or ideas for future podcasts, you can email us at speakingofpsychology@apa.org. Speaking of Psychology is produced by Lea Winerman. Our sound editor is Chris Condayan.?

Thank you for listening. For the American Psychological Association, I'm Kim Mills.