Learning to link the squiggles of text on a page or screen to words, words into sentences, and sentences into ideas, facts, and knowledge – aka reading – is a basic intellectual task required of modern humans.
But reading doesn’t come easily to everyone. Dyslexia, or difficulty with reading and spelling words, is one of the most common reading disorders, affecting somewhere around 10 per cent of children, though estimates vary.
While it was long thought to involve problems with the sounds letters and groups of letters make – what’s known as phonology – or issues with vision, more modern research has revealed dyslexia to be a complex learning disability involving multiple brain regions, and likely more than one potential cause.
One of the most important takeaways from contemporary research is that while dyslexia has a genetic component, it is far from predestined, and that early interventions can go a long way toward heading off a reading disability.
Nature meets nurture
The causes of dyslexia are “an interaction between genetics, the brain, perception, cognition, and environment,” says Prof Nadine Gaab, an associate professor of education at the Harvard Graduate School of Education.
Her research has shown that components of dyslexia can be present as early as infancy, when specific genes begin causing the brain to develop differently. Though the genetic underpinnings of dyslexia are not fully understood, we do know there are many genes at play.
A 2022 paper in Nature Genetics identified 42 genes likely associated with dyslexia, while a 2025 study in Nature Translational Psychiatry found 80 genes the authors say are linked to the disorder.
Even so, “these genes are not deterministic, they are probabilistic,” Gaab says.
That is, possessing genes linked to dyslexia is not sufficient to cause a reading disability. Researchers estimate dyslexia is somewhere between 40 per cent and 60 per cent heritable, meaning genetics is roughly half the story.
Myriad factors in a child’s environment also likely play an important role, from stress to health.
Together, genes and the early-life environment lead to distinct changes in several regions of the brain associated with pre-reading and reading skills, including areas involved in print recognition, oral language, and connecting symbols to sounds.
Important to remember, says Gaab, is that interpreting written language is not something humans evolved to do, but rather a technology we developed later on.
“We basically have to repurpose brain areas that were initially designed to do something else in order to build what we call the reading network,” she says.
“It's a very complex task that we ask kids to master in no time.”
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Brain scaffolds
People with dyslexia seem to have a harder time adapting these brain regions for reading. In her research, Gaab has followed a group of children at genetic risk for dyslexia from infancy through to late adolescence, monitoring their brain development using fMRI at various stages.
At a group level among dyslexics, Gaab found distinctive patterns of brain development, including lower volumes of grey matter in regions of the brain involved in reading, and lowered levels of connectivity between those brain regions, beginning in infancy.
It’s a finding that aligns with other studies showing that dyslexia is associated with reduced grey matter in reading areas of the brain.
One region of particular interest to Gaab is called the arcuate fasciculus.
It connects two areas of the brain involved in speech, Broca’s Area and Wernicke’s Area, and she thinks that in dyslexics it may be underdeveloped, and hence less optimised for transmitting information.
Gaab’s takeaway: “Some kids are born with brain scaffolds that are less optimal for learning to read,” she says. That can lead to reading and learning difficulties, and so without specialised interventions, their classmates will begin to pull further and further ahead.
Lost in sound
Another aspect of brain function that could be important, at least for some dyslexics, is the job of encoding sounds.
Prof Tracy Centanni, a dyslexia researcher and perceptual neuroscientist at the University of Florida, has conducted brain imaging studies that watch how the brain responds to specific sounds or words. For example, the brain reacts in a very specific way when we hear the word ‘dad,’ she says.
“In a subset of kids with dyslexia, what we're finding is that their brain doesn't respond the exact same way every time they hear the same sound,” she says. Instead, the brain may encode ‘gad’ or ‘tad,’ she says, interfering with their ability to learn.
“If the sound is inconsistent in the brain, it makes it really hard to match the letter on the page to the right sound,” she says.
“They're really thinking about every single letter, trying to match the sound to the letter. And it's always slow and effortful.”
Centanni’s work is also pointing to the existence of subtypes of dyslexia, a topic that’s still debated in the field. Centanni says some dyslexics may have issues with auditory processing while others might have problems with visual processing, working memory, brain connectivity, or other things.
“I don't know that there's right now a stable set of labels [for subtypes of dyslexia] that exists yet, but I think we're working on getting there,” she says.
Those subtypes could end up being an important tool for interventions aimed at addressing dyslexia.
The disorder is likely treatable in most people through methods such as using music and rhythm, teaching children to recognise patterns in words and to be more aware of their sound, or shared reading with a more experienced reader to help guide children through any difficulties.
Though according to Gaab, we’re still falling short of what’s ideal for deploying these steps.
It’s important to begin intervention early, she says, by the age of four or five. The challenge is that’s the age when children are just beginning to learn to read, and identifying dyslexia at that stage is difficult.
To help, Gaab and her collaborators have built a screening tool that assesses core elements of reading proficiency in children who haven’t learned to read yet and generates a risk score for dyslexia that can help guide decisions.
“In pre-kindergarten, or even before that, you can do comprehensive early risk screening and then respond to the screening with good teacher training and intervention,” Gaab says.
Other researchers have created diagnostic tools, as well, like the Rapid Online Assessment of Reading (ROAR) platform from the Stanford Reading & Dyslexia Research Program, which provides teachers with a free tool to diagnose dyslexia, and which is being used in 20 states in the US.
Interventions like these could be crucial for children who fall behind on reading, Centanni says, especially because it can be so hard to catch up.
By the time dyslexia is often diagnosed, many students are already deploying reading skills to learn new information.
This means the child with dyslexia is essentially relearning to read with the new interventions, while in tandem trying to keep up with the class.
That kind of deficit can be chronic if not addressed, Centanni says, and can contribute to things like the school-to-prison pipeline for children who feel left out or unable to learn.
Still, in most cases, all that’s needed is dyslexic-specific interventions, she argues.
“This idea that kids with dyslexia aren't smart enough to get it is just such an old myth that we've debunked for ages,” she says.
Even as interventions for dyslexia proliferate and teachers grow more confident in diagnosing and addressing it, it’s unclear whether rates of dyslexia have much changed.
That’s due to factors like changing definitions of dyslexia, poorly constrained sample populations in studies, and the difficulty of establishing standards for reading difficulties.
And though current interventions are shown to be effective, it’s also clear that we need to learn more about the root causes and implications of dyslexia.
Some studies indicate that those with dyslexia may also have higher rates of maths difficulty and might have difficulty recognising faces.
There’s still much to learn about dyslexia, and about how our brains handle reading more generally. In fact, studying the disorder may even reveal new insights into how the human brain functions, helping neuroscientists better map the capabilities of human cognition.
And, if it’s any help to readers finishing an article full of new concepts and ideas, remember: reading is a lot harder than it looks.
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