From Our Neurons to Yours

How we learn to read (and why some struggle): what neuroscience teaches us about a transformative human technology | Bruce McCandliss

• Wu Tsai Neurosciences Institute at Stanford University, Nicholas Weiler, Bruce McCandliss • Season 7 • Episode 12

Share episode

In this episode, we explore the fascinating neuroscience behind how children learn to read with Bruce McCandliss, director of the Stanford Educational Neuroscience Initiative.

Key topics include:
• How our brains "recycle" visual and language circuits to create reading expertise
• The crucial threshold when reading shifts from effortful to automatic
• Why some children struggle more than others to develop reading fluency
• How teachers can tailor instruction to help struggling readers
• The profound ways literacy reshapes our brains and cognition

Join us  for a mind-expanding look at one of humanity's most transformative technologies - written language - and how mastering it quite literally changes our brains.

Learn More

Recent Academic Articles & News Coverage

We want to hear from your neurons! Email us at at neuronspodcast@stanford.edu

Send us a text!

Thanks for listening! If you're enjoying our show, please take a moment to give us a review on your podcast app of choice and share this episode with your friends. That's how we grow as a show and bring the stories of the frontiers of neuroscience to a wider audience.

Learn more about the Wu Tsai Neurosciences Institute at Stanford and follow us on Twitter, Facebook, and LinkedIn.

Nicholas Weiler (00:11):

Welcome to from our Neurons to yours from the Wu Tsai Neurosciences Institute at Stanford University, bringing you to the frontiers of brain science. I'm your host, Nicholas Weiler.

(00:27):

For most of us, reading feels as natural as seeing or hearing. It's so automatic. When you're driving down the road and you see a billboard, your brain processes those words faster than you can blink. In fact, it's hard not to read words that are in front of you. But of course, reading is not something humans have done. For most of our evolutionary history, writing has only been around for a few thousand years, and mass literacy is a much more recent phenomenon, which raises a fascinating question. How does the modern brain, which is a product of evolution, rewire itself? So that reading becomes almost second nature when you think about it that way. It's almost no surprise that learning to read is not a smooth process for everyone. This is the question at the heart of today's conversation with Bruce McCandliss. Bruce has spent his career studying what happens inside young minds as they learn to read and why some children struggle to cross that threshold into fluency. His work as the director of the Stanford Educational Neuroscience Initiative sits at the important intersection between brain science and the classroom. I began my conversation with Bruce by asking him how we got into this field in the first place.

Bruce McCandliss (01:40):

So I really became fascinated when I was an undergraduate in this field of cognitive science. So figuring out how can we use the tools of science to really understand how the mind works? And one of the central questions within cognitive science is like, how is it that we read words? How do we look at a visual word and then turn that into a thought in our mind? How does our mind turn that physical energy that's hitting our eyeball into a really specific idea in our culture? And I got fascinated with some of the science that was happening at the millisecond level of what's happening when your mind is turning a stimulus into an idea and then being able to integrate it in your thoughts and act on it. Most of the work was really at the science level happening at the adult level trying to understand how does this clock work and how could we take it apart and analyze all of its parts?

(02:34):

And at the same time, I was very fascinated with the very notion that this whole skill is something that doesn't really exist in the minds of most humans that are under four years of age and doesn't really exist in most cultures that haven't interacted with this one technology of writing things down. So I was spending part of my time working as a tutor, working with students that were really, really struggling and working with amazing teachers that had methods of helping kids overcome these barriers and kind of break through to this new way of using their mind. And I ended up trying to see if I could bring these two things together, could we kind of bring the neuroscience effort of really trying to understand the mechanisms together with this more social aspect of how do we help the next generation discover this amazing potentiality of what you can do as a human mind?

Nicholas Weiler (03:27):

Wonderful. Yeah, I mean, it is such a trip to think about the fact that as you said before, you're four years old, you can't read, and then for most of us as an adult, it's like breathing, right? You see words, you see meaning. I had this conversation with Laura Williams in psychology a couple of months ago that when we hear people talk, we're not hearing the words, usually we're hearing the meaning, but the same is true when we read. It's invisible almost. You're just seeing the meaning and it's so remarkable that this is not an ability that our brains evolved. This is a technology that human beings created that has become so central to our culture and to our society. So yeah, I'm so fascinated by what is going on in young kids when basically this technology is transforming their brain.

Bruce McCandliss (04:20):

So as your brain learns to adapt to this technology and learns to internalize it, what's happening is your brain is setting up and tuning and reshaping many, many hierarchical cortical layers of processing information and tuning it to the kinds of information that you need to extract out of a visual word. And at the same time, it's reshaping the many hierarchical levels that we use to hear language in order to make a connection with the visual system.

(04:48):

So while we just read automatically, if I put a word in front of you, you can't help but read it. It's a puzzle that pops into your mind. There's a lot going on under the hood, which is being tuned and formed into what some people call it, the systems level, a reading circuit, an integrated circuit between vision and language and our semantic hubs that is fine tuned to represent our entire mental lexicon to make rapid connections between what we know about the visual form of a word, the auditory form of a word and a semantic form of the word. And as you engage your mind in this adaptation and you build your vocabulary and you build your fluency and you build your automaticity, you are actually changing and shaping a physical circuit inside your brain, and you're changing the information flow within that circuit in a pretty dramatic way, which is bridging across multiple systems in the brain that have really, really different operating principles.

Nicholas Weiler (05:45):

Yeah, I have a five-year old and an 8-year-old, and my 8-year-old is just so book crazy, any written word, he's qd it on and he has to read it, and my 5-year-old is just starting to get there, and it's a very exciting thing to watch where a few months ago he was really just solidifying letters and letter sounds and things, and now he's starting to think about the combinations of letters and what sounds that would make. So what's going on inside my five-year-old's brain? How is that process of connecting what he's seeing with the sounds and with the meaning? How is that changing his brain?

Bruce McCandliss (06:22):

Yeah, so there's a lot of insight from this that comes from studying fully intact, thriving, healthy adults who grew up in different cultures that rely on this adaptation for reading to different degrees. There are some thriving cultures like in Portugal, there are fishing villages where reading just isn't part of their life, and they're almost completely functionally illiterate when you look at them compared to folks that have some literacy integrated in their lives versus people who like literacy sort of is their life and a lot of modern societal contexts.

(06:54):

There are really big differences in the brain that are pretty stark in terms of some forms of behavior, but also show up really, really differently. In FMRI scans, one of the most remarkable things is that the people who are literate, they actually process language differently. They often have much larger vocabularies. They often restructure the phonological codes of the vocabularies in different ways that are sort of tuned to the alphabetic principles. And we can see how it is that learn to read profoundly changes your language circuitry and has an influence on your visual circuitry. When you look at the regions of the brain that becomes specialized for processing tools or processing human faces or processing other visual categories, the brain seems to carve out a territory for representing visual words

(07:48):

And that large sort of blob becomes more active in an FMI scan when you're looking at your native script versus if you're looking at a non-native script. So it's very tuned to your individual script. But then when you go in and look at the circuitry of that, you see that there's these hierarchical levels that have been built up to extract the most important features out of your script and then start to process the most important combinations of those features and then actually represent very specific words that in this frequency dependent way, so that a word that's a hundred parts per million versus 50 parts per million versus one part per million will have a really different neural activation just in the first few hundred milliseconds.

Nicholas Weiler (08:29):

So you can actually see, if you were looking at FMRI, whether someone is looking at a very familiar word versus a very unfamiliar word,

Bruce McCandliss (08:37):

And the implications of that are remarkable because that means you have neural codes that represent that specific word and it's sensitive to how many times in your life have you seen that word?

Nicholas Weiler (08:47):

You mentioned the example of some of these studies looking at, for example, Portuguese fishing villages where reading's not really a thing that is important to them. Are you saying that these sort of visual recognition areas that become devoted to words during the development of literacy, is that pretty much equivalent to maybe what someone in this fishing village would have to their knowledge of knots or their knowledge of what the ocean looks like at the right time or different kinds of fish? I mean, is it the same kind of visual expertise that you would develop for any category of thing that you're an expert in?

Bruce McCandliss (09:22):

I think that's a really good question because kind of built into that question is this notion that as we use our human visual systems to engage in our ecological niche, the visual system starts to develop this process that we call perceptual expertise. So there are these rapid automatic visual categorization and individuation processes that happen to the objects of our expertise. And you can actually dynamically study this. People have studied this with human faces. There's this rapid change that occurs over development. You develop this perceptual expertise for faces that allow you to process faces very, very rapidly, sometimes very holistically, and that can be different for many, many different objects. If you become a radiologist, you develop this perceptual expertise where you just automatically see the structure of bones and slight deviations, or if you become a car expert, like present the object of your expertise to your retina, and then automatically there'll be like this individuation categorization process that just kicks off.

(10:23):

That's really driven by dedicated circuitry in pretty higher level parts of the visual system that rapidly process this information. One of the things that Stan Hane and I did several years ago was to say, could we take this perceptual expertise framework? Could we apply that to thinking about reading? That was a very powerful move because suddenly we saw that readers have visual perceptual expertise for the written word. The thousands of hours that we spend looking at words develops this kind of structural and then actually quite specific set of representations that allow us to see words as perceptual experts, which means that they're automatic, which means that they're highly differentiated. And it also means that we've pulled out all of the statistical structural regularities of that particular visual form. So all the statistical regularities of all the ways the letters combined, we've pulled out all the statistical regularities about what of that information is going to interface the best with our language system. We've automated these in such a way that I can show you a visual word you've never seen before in your life, and the statistics of the letters in that word will actually show how quickly it activates, how sensitive is, how rapidly you can access how that word would be pronounced.

Nicholas Weiler (11:41):

So yeah, this is getting at an interesting question, and I think this actually speaks to some of the debates in early education about the relative importance or the balance of word recognition. I've seen that word before, I know what it means versus phonetics being able to construct, I have no idea what that word is. I've never seen it before, but based on the rules of my language, I can kind of figure out how it would be pronounced and maybe there's a piece of it that looks like another word and I can reason out what it is. So what is the balance there between recognition and phonetic puzzle solving?

Bruce McCandliss (12:17):

Yeah, that's a great question because from a teacher's perspective, if you've got time to work with students and you want to spend that time, most valuably, many students even in the same class will be at completely different places in this process of adapting their neural system for fluent efficient reading. So for children who are not reaching automaticity, they're looking at a visual word and they're spending a lot of time in this error prone and sluggish effortful attempt at figuring out what visual word are they looking at? Those kids are going to really benefit from a completely different set of learning opportunities than a kid who's already sort of over this hump within a quarter of a second, they can tell you what word they're looking at. Those kids can benefit from really, really different learning opportunities.

(13:07):

So there's this kind of critical threshold, can your brain turn a visual word into its corresponding word that in your language within a quarter of a second. And once you reach this threshold, there's a lot of interaction between reading comprehension and visual word form recognition in which there's this kind of virtuous cycle that takes on where the more you're using your visual system to comprehend language, the faster and more automatic those visual representations are forming. And so you can do a lot of things with kids by really engaging them in the reading process. But before that happens when kids are still struggling, those kids can really benefit tremendously by learning opportunities that help their brain find the structure in the visual word and find the structure in the language, slow things down, use their attention to start to make these connections in the most efficient way and discover these powerful relationships so that they can be on their path to engaging in this cultural process that we call reading to learn.

Nicholas Weiler (14:09):

And so that early stage that you're talking about getting to that threshold, being able to connect the sounds of the letters into the holistic meaning of the word, is part of that crucial skill, and that makes sense, right? I mean, we're not usually sounding out words, and in fact, I remember seeing research that you can scramble the letters in words and most of us can read them just fine. The statistics are still pretty similar, even if you move some of the letters around. So we're clearly not sounding things out just faster. We're now recognizing the word as a whole.

Bruce McCandliss (14:40):

Yeah, that's a confusing thing because we think about this laborious process of letter by letter sounding out as a thing that we do, and then we stop doing that, but the brain still doing something kind of like that. It's making a connection between this orthographic code about the way the letters come together and the phonological code of the way your mind would hear that if somebody spoke it to you. And so every time we see a visual word, the mind is kind of sounding it out, even though you are not engaged in this laborious letter by letter sounding out process. That is something that I think teachers and people who are in the field of science of reading sometimes talk past each other a little bit, but it's the connection between the visual codes and words and the phonological codes in words that we hear. The quality of that connection really plays an important role in how efficiently the brain can do this kind of process.

Nicholas Weiler (15:38):

What this is reminding me of is there's this famous study that your colleague, col Grill specter in psychology did about kids and the Pokemon Brain region, and we're talking about perceptual expertise. Let me tell you, my kids are definitely experts at all of the hundreds of Pokemon that are out there. They can see immediately, oh, this is that one. They know hundreds of them. This is a water type, this is a fire type. This one evolves into that one, and all these things and that level of expertise, this is what we're talking about. It's not that you're no longer looking at some specific feature of this cartoon. They're seeing all the features, but at the same time as the expertise develops, you're seeing it as a gestalt as well, and you know how it fits into the story. So I love this idea of thinking of reading as part of perceptual expertise for that reason.

Bruce McCandliss (16:29):

Yeah, I think that's why it's such a generative framework because it does seem to be a discovery about one of the aspects in which how the human brain learns within a particular domain is we build up this perceptual expertise. So the objects of our expertise, we develop dedicated circuitry. It happens effortlessly. But one thing that's also really cool about perceptual expertise is there's kind of a rich get richer phenomenon. If you develop perceptual expertise like let's say for these Pokemon characters,

(16:56):

Your ability to learn a new Pokemon character that you've never seen before in your life is suddenly much more facile because you've pulled out the structural regularities of that particular domain so that you can now encode new Pokemon characters much faster. As somebody builds up the foundation of visual word recognition and they set up these really highly efficient generative codes for mapping letters onto language and they find the most efficient codes, suddenly they get better, not just at the words that they learned. They get better at seeing a new word they've never seen before in their life and coming up with a really rapid great pronunciation of that word. So in a sense, the more you develop this perception of expertise, the easier it is to learn and it becomes this self-reinforcing system.

Nicholas Weiler (17:43):

Oh, that's so fascinating. And again, it's a meta skill that we evolved. We can form expertise in whatever we need to form expertise in, but reading is something that, as we said earlier, it's a thing that we have to educate and train to become experts in. If it's something that's important for our society, I think that's a good transition to talking a little bit about what happens for people for whom that's more of a struggle. On the one hand, it makes me think, wow, it's amazing that we can do this at all. And so naturally it's not going to be easy for everyone. It's not something that most people had done before the Gutenberg press just a couple hundred years ago, so not too surprising. So what have we learning from this sort of neuroscience of education, the science of reading movement, about what are some of the stumbling blocks that make it harder for some kids to get over that hump that we were talking about before?

Bruce McCandliss (18:36):

From a human neuroscience perspective, reading is this remarkable combination of two skills that a four-year-old already has. They have this amazing visual processing supercomputer in their brain that represents all of these things that they've learning about. They also have this amazing supercomputer for does all this amazing time dynamic analysis of tens of thousands of really specific words that you have

Nicholas Weiler (19:00):

That you hear just in learning to speak.

Bruce McCandliss (19:02):

That's right. But there's this neuronal process of bringing these two systems together, that framework that Stan de Hain and Lauren Cohen called Neuronal Recycling, or in French, it's prettier word like sage, doesn't sound like taking out the trash. This framework has a really generative implication for thinking about challenges in education. If there are individual differences in how a kid's language system is working before they learn to read or if there's individual differences in how the kid's visual system is working, and we see in neuroscience really large individual differences among kids, the implication for that is that can have an impact on how difficult it is for that particular brain to combine these two systems into reading. So if you map out variation in pre-reads for how do you set up phonological codes for language, a whole bunch of words, you know what they mean, but can you play with the sounds of those words?

(19:59):

Can you tell me which words rhyme? Could you take one sound out of a word like split and what would be the new word? There's large individual differences in terms of how kids' brain networks are set up to engage in that kind of analysis. And it turns out that those are highly predictive of who's going to have persistent difficulties and struggle, even though they might spend the same amount of time and the same amount of effort of adapting their brain. For this one particular technology of alphabetic lithography, these kids are going to have a tremendously difficult time because their language is not already ideally structured to interface with these orthographic codes. One of the things that we've discovered is that one of the biggest predictors of persistent challenges in reading, which we think of as this visual skill actually come from the individual variation in the language system.

(20:49):

And there's remarkable studies that do brain scans of children from really young ages of a couple of months old all the way up until the reading years, and they can discover patterns in the language system and in the process of how does our brain take an auditory word and find out what the phonological codes are and then figure out what the word is, there's individual variation there that wind up spelling really big challenges for kids when it comes to late in life, reorganizing your brain to combine vision and language for this cultural skill that we call fluent reading.

Nicholas Weiler (21:25):

Interesting. So part of it is how can you take part and play with the idea of words and meanings in your mind before you even start to look at reading on the page? And then I think that you were suggesting that there may also be some individual differences on the visual side. You've also looked at things like how quickly the brain is responding to looking at letters and words. What are some of the differences you see in kids that are predictive of how quickly they can learn to read on the visual end,

Bruce McCandliss (21:57):

We have this remarkable opportunity at Stanford trying to combine education and neuroscience of working with a school for innovation that's here in the Bay area called the Synapse School. And we were able to partner with them to look at electrophysiological responses to visual words and to different kinds of visual stimuli from when the children were kindergarten age all the way up through when they were grade four, and then followed some of them all the way up until grade eight.

Nicholas Weiler (22:27):

Wow. So these kids have EEG caps on, and you can see how the brainwaves are changing.

Bruce McCandliss (22:34):

Yeah. There's a state of the art 128 channel electrophysiological laboratory right in the middle of a school that kids use just like they use the makerspace or the computer lab that's called the Brainwave Learning Center. And one of the things that we discovered in these kids is when you have a lab within a school, you can kind of see what's changing over time in terms of the brain's visual response to things like visual word forms and what's changing in their overall reading skill. As you go from kindergarten to through fourth grade, the brain's response to the visual code for words, the brain's ability to pull out the statistical patterns within a word form, there's a sensitivity to that that shows up in the electrophysiological response. So for kindergartners, you're showing children completely novel letter strings they've never seen before in their life, and some of these have all of the combinations that an expert reader would notice right away. Other of them are just random collections of letters. For many kindergartners, there's absolutely no difference in the visual system's response to these two kinds of novel stimuli.

Nicholas Weiler (23:40):

I'm smiling because again, it reminds me of my five-year-old. He will always say, what is L-B-T-X-Q spell? I don't think I could pronounce that. So again, this is exactly what you're talking about, right? There's no difference there. Yet.

Bruce McCandliss (23:57):

They haven't engaged in this expertise building process where you pull out what goes together and how do parts form holes. But one of the most remarkable things that we found was that there were individual differences that are emerging as early as first and second grade, where some children are showing a remarkable sensitivity to these structural aspects of visual word forms, and others are really kind of surprisingly insensitive to it in terms of not only what they can tell us about it, but their brain's initial response during the first couple of hundred milliseconds. So just the perceptual response to these things. It turns out that it was this structural contrast between well-formed visual word forms and poorly formed visual word forms. This structural difference was actually a really strong predictor of the rate of reading growth over the course of two years.

Nicholas Weiler (24:48):

And you're talking about hundreds of milliseconds. And so the ability to recognize is that a well-formed word or not in a quarter of a second, is predictive of how quickly they're going to learn to read.

Bruce McCandliss (24:58):

Yeah, and one of the remarkable things about that is that this is not a test of like, oh, I know this word or I don't know this word, but it's a question of do I see the structure in this new word I've never seen before? And then later on, could I automatically map that onto the way I would pronounce that word? Or what would that sound like in my mind's ear? And we think that breaking into this ability, not just knowing a whole bunch of words, but actually learning the structure of the letters, how they come together in words and mapping that to the structure of how individual sounds that we hear in words, form words together, combining the structure, the visual structural analysis, and the linguistic structural analysis, we think it actually changes the rate of learning to read over time so that kids that are breaking into this are taking off and learning a lot year by year by year. And that kids that are not really clueing into this structural regularity of visual words and auditory words, they often are on a much slower trajectory in terms of just their overall global reading ability. If you give 'em a whole list of sentences and for three minutes just say sort these into sentences that make sense and don't make sense, silently going through these, you can see a relationship with these start to form.

Nicholas Weiler (26:13):

That's so interesting. Well, this may be very new, so maybe we don't have answers to this yet, but what do you think is going on there? Why some kids, it takes longer for them to click with that structural regularity, and does that suggest any directions for interventions that could particularly help those kids?

Bruce McCandliss (26:32):

That's a really fascinating question. I've thought about that for a really long time. We all have these amazing human brains. Why aren't they all just figuring this out? One of the really very, very fun cool studies that we did was going at that question really quite directly to ask. Maybe part of the difference between kids isn't just the way their language circuits are organized, either really quite ready and well structurally aligned for learning to read versus organized in a different way. What if part of it is this salience noticing these things? Imagine that they never really discovered the structural regularities because they never really started to attend to them, or they never started noticing them, or they never really became salient. And that led to this really fascinating line of research that I did with a very talented researcher who's now at NYU Yulia Y Chava, where we said, could we run little experiments in which we teach people brand new word forms we've never seen before?

(27:28):

Look at the structural regularities to see if their brain discovers them or not, and then just manipulate the salience of these structures. Could you point out to people like, Hey, there might be some structural irregularities there, so if you want, look at the structure of these letters and how they come together and try to focus on that. And it turns out that simple manipulation of just making those combinations more salient had a tremendous impact on just a couple of hours of learning, changing the way their brain responds to these visual words, and suddenly the people who were clued in to make these relationships really salient started producing electrophysiological response that looked a lot like expert word recognition.

Nicholas Weiler (28:11):

So it really is this, there is a rule here, why don't we look for what are some of the patterns? It's like solving puzzles or jigsaw puzzles or crossword. There's a strategy, and once you know what the strategy is, it makes it much easier to solve any given puzzle.

Bruce McCandliss (28:25):

And you know what? The one really cool kind of synergy between that contrast of like, oh, draw people's attention to this. Give them learning opportunities that help them notice these things and help them practice these things and start to learn all of these systematicity a synergy between this neuroscience research that we've done and what we see in education systems. If you look at how are teachers devoting their time over the course of the minutes of a reading block, there are really, really large differences in how teachers make those learning opportunities present for kids. They put it in front of them, they give them opportunities to see the structures of letters within words and to play with the sounds of words and connect these words. Some teachers do this only a tiny little bit. Some teachers do this quite a lot in a heavy handed kind of way sometimes, but there's large variations in terms of making these relationships salient.

(29:19):

And it turns out that the number of minutes a teacher will spend on these kinds of activities versus other kinds of reading activities has a really, really profound impact on how rapidly kids learn during that particular school year. And then what we've discovered beyond that is that this makes a very, very small difference for kids who came into that class already, well on their way to perceptual expertise for visual word recognition, but for the kids that don't, the difference of how much time the teacher spends on these activities makes a larger and larger and larger difference in terms of how much they're learning, how fast they're progressing in reading over the course of that school year, there are meaningful differences between kids and these meaningful differences in terms of where kids are on this process of learning to read. There's a really big interaction between child characteristics, the kids who are struggling and the type of treatment or the type of educational opportunities they're getting. So the kids who are struggling, the more minutes the teacher spends on these word recognition skills, the faster they learn over the school year. And for the kids who are not struggling, that makes less and less difference.

Nicholas Weiler (30:30):

That's so fascinating. I mean, it makes sense because one of the key things I'm taking away from this conversation is this idea that there's this transition point. I forget that you used a great word for this before. I can't remember exactly what it was, but there's this,

Bruce McCandliss (30:44):

It's like a

Nicholas Weiler (30:45):

Threshold. Yeah, A threshold that until it clicks, it's very hard and it doesn't make sense and it's slow. And then once it clicks, I think you called it a virtuous cycle, that the more you get the expertise, the easier it is to build additional expertise. I obviously keep coming back to my kids because for them it's very novel, right? I'm seeing what it's like to either learn to read or be a new reader. And my older son, my 8-year-old, said to me the other day, when I'm reading, it's like I'm going somewhere else. It's like I'm in a

Bruce McCandliss (31:16):

Different

Nicholas Weiler (31:17):

Space. And that's this other level that you ultimately can get to and why reading is so powerful and so transformative that it can take you out of yourself and into another world, whether that's some imaginative fantasy world or just into the arguments that someone is making in an essay or a

Speaker 3 (31:36):

Nonfiction

Nicholas Weiler (31:37):

Book. You're in this mental space with someone that depends on the transparency of the words. You can't be looking at the letters at that point. It's a direct connection, a mind meld across space and time, right? This writer may have died hundreds of years ago, and you can still have this mind meld, and at the heart of it is this transition, this little thing where you figure out the statistics of the letters and the sounds and the meaning, and so, I dunno, I'm just like,

Bruce McCandliss (32:07):

That's right.

Nicholas Weiler (32:07):

Geeking out about this. It's this very magical moment,

Bruce McCandliss (32:11):

But beyond the threshold, there's something else going on. So we've been talking a lot about the dynamics of perceptual expertise for how well is your brain turn visual words into thoughts. There's another set of processes that kick in that we use for language comprehension when your brain is turning visual words into ideas at a pretty rapid rate. We are engaging in all these processes of mental model building and kind of constructing what the author's talking. And a lot of times when you're talking about reading, that's what you're talking about. And then you go talk to a scientist like me who's talking about like, well, what about the milliseconds of your visual system? Turning this into a language representation? You think these things probably have nothing to do with each other. And the remarkable thing is that these actually have an amazing connectivity to one another.

(33:02):

The speed and fluency with which your mind turns a visual word into a linguistic thought has a really, really tight connection with your reading comprehension. Once you pass this threshold of being able to turn a visual word into a linguistic thought, it turns out that there's this Chuck PTI calls it the lexical quality hypothesis, the speed automaticity and efficiency of that computation. There's individual differences there. Some people are a little bit faster. The more you do it, the faster you get. There's a really powerful relationship between how fast that split second computation is working in your brain over and over and over again, and then how you're engaging in comprehension overall, which is kind of remarkable, something we measure at this timescale of 250 milliseconds or a blink of an eye, right? The dynamics in that and the individual differences in that and the growth in that are related to how well you're doing this deeply psychological process of interacting with the thoughts of the author.

(34:03):

It becomes from completely absurd and hard to imagine, to obvious if you think about race cars. So if you go and look at race cars and you're like, amazing, this car can go faster than any other car that's been invented. People will, they try to explain why. They'll go and they'll look at the time dynamic processing happening with an engine of that car. The carburetor is making a spark and turning that spark into energy and putting that into the axle. The time dynamics of that iterative quick little process that your brain is doing is having an impact on the entire sort of dynamic of the car racing around the track. This is something that's been discovered again and again and again. It's a little bit counterintuitive, but it's also really kind of remarkable.

Nicholas Weiler (34:46):

It is absolutely remarkable. I'm going to think about reading in a different way. Hopefully it's not going to distract me from the thought process. I'm going to be thinking too much about what's going on in my brain. So I just wanted to close. I mean, after we've talked about a lot of different things, what would you like listeners to take away from this show now that they have a better understanding of what an amazing skill reading is? How should this change how we think about our own reading habits and how children learn to read?

Bruce McCandliss (35:15):

Yeah. One thing I'd like to help people to realize is that when children are going through the school age years, there are structural changes happening in the white matter tracks of their brains that are really deeply tied to the experiences they're having in school. If you follow a child over time and you follow lots and lots of children over time and look at them at multiple time points, some children will have a little growth spurt in their reading ability. When that's happening, there are changes that are occurring in the white matter tracks that are reorganizing and following that sort of growth spurt. And that's been one really, really nice discovery about how something like breaking into this new form of using your mind for something like reading can actually help guide the restructuring of your mind that's happening with strengthening certain white matter tracks. Those changes are occurring are not just maturation.

(36:11):

They're happening in the context of education systems in school. We've recently started to discover that the quality of educational opportunities and environments that kids are in has a really clear relationship with how their white matter tracks are changing over time. Even if you measure kids from fourth grade through sixth grade, their white matter tracks are changing over the course of two years. It turns out the qualities of the school system they're in has a really big impact on how fast those white matter tracks are changing. So all of this amazing plastic reorganization that we see in the emerging reader is happening inside these larger educational contexts that are supporting or not, to some extent, those changes are occurring. So there's a really, really interesting interplay that is just starting to emerge. Really, really deep dialogue between developmental, cognitive neuroscientists who are studying these changes happening in children and education systems, education practitioners, education researchers that are studying the systems that are surrounding and supporting those children, and we're starting to find really, really powerful links between these very different worlds that speak different languages. They have different terminologies, different ways of talking to each other or arguing with each other, but the connection between human neuroscience and human education, I think is a really profound one, which could be actionable. We could start changing the way we engage with children as we start to understand how their brains are changing for these fundamental skills like becoming fluent in reading and mathematical thought and executive control.

Nicholas Weiler (37:55):

Yeah, and I mean, thinking of reading as a technology and education as a crucial part of that technology really sets up a different way of thinking about this, and I know there's a lot of anxiety right now about how well kids are learning to read, how well college students are able to read lots of how many books people are able to read, what with everything happening on social media and screens and so on. That's of course a whole different conversation and maybe one that we should have you back for. But Bruce, thank you so much for coming on the show. This has been absolutely fascinating.

Bruce McCandliss (38:25):

Fantastic. Great to talk to you.

Nicholas Weiler (38:29):

Thanks so much again to our guest, Bruce McCandliss. He's the picket family professor in Stanford's Graduate School of Education and leader of the Stanford Educational Neuroscience Initiative. You can read more about his work in the show notes. If you're enjoying the show, please subscribe and share with your friends. It helps us grow as a show and bring more listeners to the Frontiers of Neuroscience. We'd also love to hear from you. Tell us what you love or what you hate about the show in a comment on your favorite podcast platform, or send us an email at Neurons podcast@stanford.edu. From our neurons to yours is produced by Michael Osborne at 14th Street Studios with Sound Design by Morgan Hunker. I'm Nicholas Weiler. Until next time.