Instant Genius - A bold new theory of dyslexia, with Prof Usha Goswami

Episode Date: April 23, 2023

About 1 in 10 people in the UK have dyslexia, which is a neurological difference that can result in difficulties learning to read and write. But what exactly causes it? Scientists aren’t in full agreement, but our guest this episode – Professor Usha Goswami, a leading neuroscientist at the University of Cambridge – poses one intriguing theory. Her work so far suggests that dyslexia is not a visual disorder, but rather a difference in how sound and rhythm are processed in the brain. She joins us to explain all. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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sound at home. Music just as the artist intended. Visit name audio.com to learn more. And welcome to Instant Genius, the bite-sized masterclass in podcast form. I'm Thomas Ling, digital at BBC Science Focus magazine. About one in ten people in the UK have dyslexia, which is a neurological difference that can result in difficulties learning to write and read. But what exactly causes it? Scientists aren't in full agreement,

but I guess today, Professor Usha Goswami, a leading neuroscientist at the University of Cambridge, poses an intriguing new theory. Although not yet conclusive, her work so far suggests that dyslexia is not a visual disorder, but rather a difference in how sound and rhythm is processed in the brain. She joins me now to explain all. So I'm going to start from the beginning and ask what actually is dyslexia?

Because there's the big stereotype that people with dyslexia are just quite bad at spelling. But I take it it's a bit more than that. I think it is a bit more than that. I think dyslexia is based in difficulties in language processing, hearing speech, where your brain represents the speech that you hear. That seems to operate a bit differently in people with dyslexia, according to my research. That's interesting. So I think quite often, if a film or TV drama depicts someone with dyslexia, they're showing them trying to read and all the letters are jumbled up with the wrong way around. How accurate is that? Is dyslexia

a problem with the visual system in that respect? Dyslexia is fundamentally a problem with the auditory system. That's according to the research that I'm doing. And all children go through a stage of the letters seeming to be jumbled up. It's a natural stage in learning to read, because your object processing system needs to recognise an object whatever angle you see it at. But the way that our alphabet works, there are certain letters like B and P, where the angle that you see it matters enormously for what it means. So all children have to learn that. People with dyslexia will always have difficulty spelling because spelling is writing down the sounds that you hear. And the dyslexic brain is not hearing those sounds quite in the same.

same way as everybody else. So the speech processing system is absolutely fine for listening and comprehending. But when it comes to formalizing that system, having some kind of code for representing the sound structure of that system, it doesn't matter whether you're learning Chinese or an alphabetic language or Dev Nagri in Hindi. Your brain is not hearing those sounds quite the same as other brains. And so it's very effortful to use these visual symbols to represent the speech code. So I think you can be extraordinary bad at spelling and grammar, but not be dyslexic. Yeah, that can happen to. You'd have to do the sort of diagnostic test for dyslexia, which really are to do with sound structures of words. Those are the kind of ways children are

diagnosed at the moment. But the research I do suggest that there's a problem right from infancy in the way the brain is processing the speech signal. Speech is such an important input for us that we have to learn to use speech. We have to be conversational partners with the people in our communities. So there's lots of redundancy in the signal. There's lots of different ways of interpreting it. The problem for people with dyslexia

is only relevant for one of those parameters and it only seems to really matter when you have to do speech written down, which is learning to read and write. It doesn't really matter for acquiring language overall. Is dyslexia always a bad thing? Like, do people with dyslexia actually have a lot of advantages in some areas? I think they must have advantage.

I think there's very little research on that. But, you know, the fact that it's still in the gene pool means that, of course, it also confers advantages. Speaking anecdotally, I would say people with dyslexia are often very creative, and they're good at thinking outside the box. So they don't seem to think in such a linear fashion as people who've spent years of their life scanning lines of print and got very, very good at it. it. People with dyslexia, their minds seem to maybe have a more spatial way of thinking about problems and issues, but it often can lead to them having solutions that other people can't

come up with. In fact, I did read recently that they're very good in cyber security because they think differently. So when you get these cyber attacks, someone with dyslexia can actually have an advantage in trying to solve how that attack is working. So I think this is going into the realm of the theoretical now, but why do you think people with dyslexia might think differently in a way that makes them more creative? Do you have any sort of theories? This is completely speculative. But yeah, I do think there's something about how you remember things. If you've got a very good speech processing system, then you've got this linear representation, certainly once you've learned to read, of what the sounds in words are. And if you're not hearing

quite in that same way, you might have a more impression. patterning. So that might be how you store other kinds of information that you get verbally so that your brain then functions differently when it's trying to put together all that knowledge. But that's a complete speculation. So what is the main disorder here? Is it down to memory then or something like that? It isn't memory. It's to do with online processing of that speech signal, which is the most complex signal our brain receives. And there's a hidden, structure in that signal which is carried by rhythm, rhythm patterns. And it's that hidden glue that the dyslexic brain is not so good at representing. It isn't that it can't represent it at all,

but it's less good than other people's brains. And so it compensates for that by over-representing other aspects of speech that don't help you in terms of learning a spelling system. So usually you don't know there's anything wrong until a child gets to school and has to try to learn formally to read. Sorry, so are you saying that a person's ability to keep a rhythm could predict if they have dyslexia or not? I believe that's correct from the kind of research studies we've been doing, because you can play somebody who already has a diagnosis of dyslexia, a simple rhythm beat like a drum beat. And you can show that when their brain is interpreting that rhythmic beat, it's slightly out of time compared to other people's brains. it's like the rhythmic synchronicity with which the brain locks into those rhythm patterns in speech is slightly out of time. And we've found that in many studies.

Okay, so probably a big question, but why might that be the case? It's somehow inherited. So we know that if you have dyslexia in the family, there's a much higher risk of the child being dyslexic. And so we can do studies now with babies who are born to parents where there's known to be dyslexia in the family, and we can look at whether babies are hearing these rhythmic beat-type inputs that we give them differently to other babies. And indeed they are. You can already show this before they've reached a year of age. So it means the brain is processing speech subtly differently. It's subtle, but it is different. It's a bit like being colourblind. If you're colour-blind,

you can still see, but your brain is processing certain bits of the wavelengths of life, normally the green-red distinction, a bit differently to other people. You don't necessarily see green versus red. You see these different shades of, they all seem similar. And the dyslexic brain, when it comes to these rhythm cues,

or at least a subset of these rhythm cues, they can't really discriminate between them. And that ends up mattering quite a lot. It's okay if you can say a bit more about how differently do people with dyslexia process language when they're reading compared to people who don't have dyslexia? So when you're reading, it's speech written down. So absolutely everybody is automatically

using their speech recognition system, even though they're not aware of that. So some people will implicitly think that they can memorize whole pages of text without going through sound, but actually your brain always goes through sound. Different brain imaging studies have shown that. If you think about a novice learning to read, so usually that child is five, six, seven years old gets to school, has a very good speech processing system. or at least so it's been thought. But then when it comes to learning this code for the speech signal when it's written down,

it doesn't matter which code that is. The child is starting to have difficulties. And according to my research, it's because that rhythm, that hidden structural blue that holds the entire signal together and that the brain then uses with brain waves to represent that signal

is functioning slightly out of time. So again, this might be a very big question. But just to understand that a bit more, How are sound waves actually sort of processed by the normal brain? A very good analogy is to think of the sea. If you're looking at the sea towards the horizon, you can see all these different waves. Some of them are bigger, like the big waves a surfer might want to catch.

Some of them are quite small. And the sea is also deep. So it's a three-dimensional wave system. And the sound wave is the same. When you're speaking, you're creating pressure that moves through the air and reaches your eardrum. And that is created by the way your vocal, track works. And the way our vocal tracks work means that that signal is complex in terms of

these different rhythm structures, which are carried by changes in loudness. So we can all hear really obvious changes in loudness. Like if you're saying a nursery rhyme like Jack and Jill went up the hill, you know, words like Jack are louder than and. And it's that kind of rhythmic structure that we can even hear in foreign languages. We can hear people's rhythm patterns. But what I'm saying is there's a lot more hidden rhythm structure in that signal, which is so complicated that the brain gets. And the ear's job is to separate out these different frequencies or time scales. And then in the cortex, each system in the sort of auditory part of the brain that's trying to respond to its rhythm pattern will respond and it will all get added back together. So we're

never consciously aware of any of this. And what my research suggests is that just one aspect of that isn't functioning in time. So when it all gets added back together, the child is getting a different perceptual experience of speech. And that only matters when you try learning a visual code. So what sort of experiments are there that might illustrate how dyslexia is linked to rhythm? Well, when we started out, actually, it was just that something I'd noticed that I thought these children didn't seem so good when we were doing nursery rhyme games and so on. And I was looking at the literature and I found that when people are speaking deliberately to a rhythm, them, their timing when they say the vowel of any word. So if you're saying sweet, seat, sweet,

seat, rhythmically on purpose, your timing when you say the eat part, as it were, the rhyming bit of the word. And I looked at a way of measuring how accurately children could hear that, but using a non-speech tone task, so we could give it in any language. And in language after language, we found that children with dyslexia couldn't really hear these, they couldn't discriminate so well, these changes in intensity. And those changes in intensity, the rate of change, it's like the surfer, you know, there's a great big wave. He wants that one because it's got this massive rate of change that he needs to catch to surf and have fun. And your brain is almost doing the same thing. It's finding the big waves and the little waves, and then it adds it

all together using its electrical signaling. And what our research suggests is it's that very big wave that the dyslexic brain is always slightly out of time. We're not sure if it's too early or it's too late, but that rhythm pattern underlies all human languages because it's the pattern that corresponds with stressed syllables. And stress syllables are the loudest ones we say. It's like any metrical structure like Jack and Jill. It's also exaggerated in baby talk, even though we're doing it quite unconsciously. That particular parameter, this large change in intensity, which is roughly twice a second across human languages. That's the one though dyslexic brain seems out of time.

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systems that deliver exceptional sound and unforgettable listening experiences at home. Try it for yourself at a focal powered by name boutique. Visit focal powered by name.com for more information. It's okay if you can just expand on the last thing you said about every sort of two seconds that there's this stress beat? So languages do sound different when you hear them, but of course there might be something structurally that's the same across languages because when the brain is born into a human community, it doesn't know which language it has to acquire. And it seems to be this twice a second parameter that's consistent across human languages. Because if you look at how often people produce a stress syllable, just in natural conversation, it's roughly twice a second. And then if

you look at baby talk, it's exaggeratedly precise twice a second. So it's as though that's how the brain gets hooked in to learning these rhythm structures. And basically when we're, you know, the preferred beat structure in music is actually the same. It's 120 beats a minute, which is twice the second. So the human brain seems to have converged on this as a natural time scale, which is like a foundation for the other things it does with sound. It's very interesting. That's really interesting. Have you identified a sort of mechanism in the brain that really underpins the difference between a dyslexic person and a non-dissexic person, particularly when they are hearing this speech? Is there sort of a part of the brain that's

involved? It is. It's the auditory cortex. So it, Another simple analogy is when the brain is not receiving a signal, so the auditory listening brain, there are still lots of electrical pulses being fired by the brainwaves because they're always active. So you could think of that like fireflies in the forest. They're all producing their little pulse of electrical energy, but it's all random. But if someone started beating a drum twice a second in that forest and the fireflies decided to signal in time with that drumbeat, then you would have a brain rhythm in effect. And so you can use sophisticated equipment to measure that electrical signaling in the brain of a baby or a child or a grown up

and see whether it's in time with whatever input you're giving that brain. And you use some mathematical algorithms and you find whether the brain's in time or not with different bits of the signal. It's not just my work. A lot of people have been doing this and it just shows how complex the listening brain is. It's quite incredible, the precision with which it works. It does sound very complex, but at its almost simplest term, have there been experiments that show that people with dyslexia do struggle to keep that beads? Exactly. So you can do it behavioral as well. You can show that they find it harder to tap in time with a beatet twice a second. Just motor tapping is correlated with individual differences in reading and spelling. But you can also do these studies that we've been doing with babies where you give a rhythmic input and you try and see whether individual differences in how much the brain is on time with that input, predict later language outcomes. And according to the research we're doing, they do. Even in babies who have no risk for dyslexia, if you have a large enough group of babies and you look at individual differences in this kind of rhythmic alignment. It's predicting their vocabulary when they're two, for example. It's really fascinating.

These are just individual differences. Everybody is individually very different. We all differ in so many things. This is just one aspect in which a brain might process sounds slightly differently, but it will have consequences developmentally. That's really interesting. So if dyslexia is mainly a problem with how the brain processes rhythm, then does this mean those with severe dyslexia are likely to struggle playing instruments like the drums, for instance? When I started this for search, I had a lot of drummers writing into me to say, you know, I thought that was interesting, but I'm very good at drumming. And they are. So I actually think, again, this is another example of individual differences.

People with dyslexia can learn musical instruments. We've done studies with students with the dyslexia at the Royal Academy of Music, for example. These are very accomplishment. musicians. And the problems there will be very subtle. So it can be things like coming in on time with the rest of the orchestra or if there are complex beat changes. So we had a ballerina who came to us and said, you know, I'm dyslexic, but how does your theory explain why? And then it turned out that she did have some problems with rhythm, but they were only when, for example, you had to make step changes on the offbeat, or I don't know, I can't remember, but it was something quite difficult. In those practice routines, she was.

She did notice she had a problem. So again, everybody should try everything. I mean, we will have so many skills. Just the fact that you haven't got this particular one doesn't mean you haven't got it at all. It just means it's a bit more of a learning struggle. If you have dyslexia, is it harder to learn, say, a drum beats, for instance?

I can't answer that because we haven't looked at that experimentally, but presumably it might be a bit, you might be a bit slower. I mean, these children do learn to read, of course. It's not that they don't learn anything, but it's a much more struggling process, You know, you go to school, you try really hard, and yet your friends seem to pick it up just easily, and you don't. And, you know, that has its own complications then

because you become uncertain of yourself. But these children are really trying very hard. It's just an automatic process in their brain that's working a bit differently. So is there any evidence that if a dyslexic person listens to a lot of music and is more familiar with different rhythms that they'll be able to read best, as well? We do have some therapies that we're trying to develop based on this rhythm theory, and I think you've got to match the music to speech. So that happens very naturally when you're singing. You know, you're trying to time the beats in the words, as it were, to the beat pattern

of music. So if you were singing Jack and Jill, you'd be timing the Jack on the, you know, Jack and Jill went up. So you do that naturally through singing, and that's why these activities are so important preschool to just do all these rhythmic activities where you're matching speech rhythms to other rhythms. So it can be musically with singing or it can be by playing bongo drums in time with, you know, poems or rhythms or marching around to nursery rhymes like the grand old Duke of York. Because rhythm is a multimodal system. We hear rhythm, we feel rhythm. And of course, we actually do see rhythm as well, even though you're not so aware of that. But when you're watching somebody speaking to you, there's a lot of rhythm cues on the face as well. And what you really want to do

for these children is to try and use the other modalities to support the auditory modality in getting these rhythms. So if a child is at risk of dyslexia through genetics, so for instance, if both their parents have dyslexia, is it quite important that they do expose their child to like a lot of nursery rhymes and things like that? I would say it is. And I also think you always try and match the beats of speech to beats in music. So you do it together, you know, you make it into games and fun because just listening on their laptop to nursery rhymes isn't going to do it. You know, you have to be active, you have to be producing your own speech, you have to be doing it for a purpose, really. And a lot of the normal things you do with toddlers, they are those kind of things. You know,

children find this great fun. Usually when you find something great fun, there's a biological purpose. You know, your brain is learning something really important. can an adult who didn't have any problems in their youth with dyslexia, can they experience an onset as they get older? What's more likely is that they always had it, but they're so high functioning in other areas that they weren't aware of it. So as I said before, there's so many individual differences. So if you're a really intelligent person with dyslexia, you can usually mask it, especially at primary school. You might struggle a bit more as you're doing your GCSEs and so on, but it might not come out until university. or even at university you may still get by.

It takes you longer to finish things than other students and so on, but you know, you can still function very well without knowing you have dyslexia. It really depends on the demand level of what you're doing. If you then became, say, a lawyer and you had to read documents every day, then you might become aware you have a problem. There are big individual differences. So it's an impossible question,

but do you think there's quite a lot of people out there who have dyslexia and might not even know it? in a way it's like every human ability there's a normal curve and if you're looking at the bottom end of the curve which we would be for those people really struggling with reading it's where do you do the cutoff you know if you could say well only the bottom 7% can be classified as dyslexia there'll be someone who's in the bottom 10%

who wouldn't get the diagnosis but may still have quite a big learning effort to become a good reader so it's all about as a community where do we decide the cutoff comes to get the diagnosis Would you describe dyslexia as being on a spectrum, as I think it's quite commonly described? It depends what you mean by spectrum. I think there are individual differences in these listening skills I'm talking about. And I think if you're someone with severe dyslexia, you're probably quite down at the bottom

end of that normal curve for these listening skills. And that's listening to these intensity changes in the ongoing speech signal. The parameter I was talking about the rising energy to reach the vow, that's not discriminated very well by people with dyslexia. So in that sense, there's a spectrum of ability for that auditory discrimination, and you'd be lower down if you were dyslexic. Are there any other sort of big predictors outside of your rhythm research do you find quite compelling? It depends what you mean by big predictors, because we do know how to diagnose dyslexia, but at the moment it's quite an effortful. You know, a child will have to do a whole battery of tasks because you're looking for

a strengths and weakness profile. You're also trying to interpret index. terms of overall ability and so on. I think what could be really exciting for the future is the way that basically machine learning is coming on so fast. If I'm right, in the future, it should be able to have people just speak to a computer and the computer can analyze these parameters of their voice and see whether they have a problem of this nature that could specify dyslexia. I think that would be really exciting. Wow. Do you think as well that technology could help develop a child, they will be less likely to have a dyslexia of onset, so to speak. So could there be like an ear implants that could help here?

Well, again, it's early days, but we are doing research of that. So we're trying to amplify in the speech signal, these twice a second beat structures. It's quite complicated to do it. But our idea is that if you play these children, this amplified speech, it should improve. their ability to hear the sound structure of words and then learn visual codes for representing that sound structure. It's quite possible that you could have some kind of brain computer interface that did help you before you go to school, but that would probably be developed in the next decade or so, but it's certainly possible. And you wouldn't have to have something implanted.

I think you could just have a hearing aid like, you know, hearing aids at the moment can be very sophisticated. You do hardly see them. But of course they're amplifying the entire sound wave. we'd be trying to just amplify specific bits of it. What do you think the next big research finding in dyslexia neuroscience could be, that will be a real watershed moment? What are the biggest unknowns? Well, for me, and what I'm pursuing at the moment, is that we should be able to show in the way dyslexic people speak,

that there's a difference in terms of these energy patterns. So when you hear someone with dyslexia talking, you don't feel that they're not using syllable stress correctly. but there should be some subtle indications because if you can't hear it, it's very hard to produce it. We know that from hearing people who've learned our language as non-native speakers. You know, there's some things they never say right. You should be able to show that in dyslexia

and that could be then a very simple diagnostic tool. So just to clarify, you think that people with dyslexia might not only process language in their brains when they hear it, but also speak it slightly differently as well. It would be subtle because again, speech is so redundant. There's other ways you can change your pitch to produce syllable stress patterns. But I think in terms of changing your intensity or amplitude, the amount of energy, that's where you'd find differences. So what sort of differences might they be? Is it that people are sort of stressing certain syllables a bit later or earlier than others? What I would predict from my theory is that they wouldn't be differentiating between the syllable stress patterns so clearly because they can't hear them so clearly. so when they're saying them, it wouldn't be as clear as for other people.

In fact, a good way to think about it is, you know, there are some words in English where the phonemes are the same, so the individual speech sounds, but depending on how you stress them, they have different meanings. Content, content, they're two different meanings. I would suggest that someone with dyslexia wouldn't be able to make those two differences as clearly as other people when they're speaking. But I don't know if that's true yet. incredibly interesting. Was there anything that I should have asked about dyslexia that you're especially

interested in that I didn't? I don't think so. I think really I want to get across this idea that this is automatic processing your brain does. Everybody's brain differs in every, you know, subtle parameter of the way that we process information from the world. So for these children, we need to find ways to support them. They can't change the way their brain is processing. We can either try and change the signal their brain gets, which is what you were asking me before. whether some kind of hearing aid could make a difference, or we need to find ways to support them in the actual task of reading and writing.

And there is some very good AI now that will, you know, it's all the stuff we have on our phones and so on. You can predict what someone's saying and write it down by them just talking. So that could help dyslexic people with spelling. And there might be words where you don't know what it says, but you can type it into an interface and it will pronounce it for you. And that will be very important for people with dyslexia.

This sounds really interesting. Is it so anything actually that people with dyslexia can do without using this technology that might help them. I think there's probably some anecdotes that people have if they are dyslexic, that if they spend a lot of time reading, for instance, that might help symptoms down the line. Do you think there's anything in that? Practice always makes perfect. I mean, if you think about a child who doesn't have dyslexia, at school, when they're 8, 9, 10, they are reading hundreds of words a day, if not 1,000. And that's practice for the brain. A child who's struggling to read will probably be reading maybe 10%

of that amount. So if you think about that overdevelopmental time, say the whole period at school, there's already a massive difference between the amount of practice the brain has had in reading if you're finding reading easy versus difficult. So it will always make a difference. That was Professor Usha Goswami, director of the Centre for Neuroscience in Education at the University of Cambridge. Thank you for listening to this episode of Instant Genius, brought to you by the team behind BBC Science Focus magazine, which you can find on sale now in supermarkets and newsagents as well as your preferred app store.

You can, of course, also find us online at sciencefocus.com. This podcast is sponsored by Name, Audio and Focal. The texture and emotional depth of music can be lost through digital sources or poor signal. Name Audio believes you can have digital precision with analog warmth. Alongside French acoustic specialist vocal, Name creates high-end audio systems, combining innovation with craftsmanship, so you can listen to music, just as the artist intended. Discover more at name audio.com.