Brain Development Signals Reading Challenges Long Before Kindergarten

By K.C. Compton - September 19, 2025

Given the complexity of the process, it’s astonishing any human has ever mastered the ability to read. Although written language is ancient — we’ve been at it for roughly 5,000 years — it’s not an innate skill. There is no “reading center” in the brain; human brains aren’t designed to automatically decipher the symbols on a page that add up to reading. 

And yet, new research shows that the skills needed for reading begin developing before a child is born, and that signs of reading challenges can emerge as early as 18 months old.

“People don’t understand that children don’t start kindergarten with a clean slate,” said Nadine Gaab, an associate professor at the Harvard School of Education involved in the research. Learning to read “is a long process with many milestones that unfold over many years, and it starts primarily with oral language. Years of brain development lead up to the point where formal instruction puts it all together and enables them to read. The process starts in utero.”

The human brain evolved specifically for spoken language, said Perri Klass, professor of journalism and pediatrics at New York University and the national medical director of the nonprofit Reach Out and Read. Every society across the world uses spoken language, but the transition from spoken to written language is a giant leap for the brain.  

That jump, Klass said, requires the brain to recruit structures and networks throughout its many layers and folds just to recognize a letter on a page, involving the vision and memory portions of the brain. The brain then must remember the sound the letter represents and connect that letter with others to make sounds that associate with the picture on a page. Finally, at lightning speed, the brain recognizes that those letters work together to say, “Cat.”  

People don’t understand that children don’t start kindergarten with a clean slate.

Nadine Gaab, an associate professor at the Harvard School of Education

“Learning to read is a challenge for all children,” she said. “And for some children it’s really a struggle. It’s not that you develop spoken language and then, boom, you get to school and develop written language. Spoken and written language have been developing together directly from birth, and all the exposure to language from the environment — what they hear from their parents, whether they’re read to, talked to, whether someone sings to them or holds them — are there. So, it’s the brain the child takes to school that helps them succeed at this impressive task of learning to read.”

Klass points to the new Harvard research to underscore how early that “brain the child takes to school” begins developing. For years, a prevailing attitude has been that a child starts learning to read in pre-K or kindergarten. A longitudinal study by Gaab and her colleagues using MRI scans and an array of other assessments confirmed that the bases for reading skills begin to develop in the child’s brain by birth and continue building between infancy and preschool. 

“We wanted to see how early the developmental trajectories of children who later develop good versus poor reading skills diverge, because that can give us a really important clue for when we should intervene, as well as what some of the risks and protective factors are,” Gaab said, 

A key finding of the study is that the developmental trajectories of children with and without reading disabilities start to diverge around 18 months, rather than at 5 or 6 years old as previously assumed.  

And yet, Gaab said, a wide gap currently stands between the time children are identified as having a reading impairment and the start of intensive intervention. This is particularly problematic for children diagnosed with dyslexia, she said, adding that researchers call this the “dyslexia paradox.” The majority of school districts in the U.S. employ a “wait-to-fail” approach, meaning that many children are only flagged by the school system after they have failed to learn to read over a prolonged period of time — often years — even though there’s evidence that reading intervention is most effective earlier. The experience of failure can erode self-esteem, she said, and lead to the higher rates of anxiety and depression that are found in struggling readers.

The Study

The study, “Longitudinal Trajectories of Brain Development from Infancy to School Age and Their Relationship with Literacy Development,” is the first to track brain development from infancy to childhood focused literacy skills — a window into later academic attainment.     

Over a decade, Gaab and co-authors Ted Turesky, Elizabeth Escalante and Megan Loh conducted MRI brain scans of 130 study participants starting at 3 months old. Half of the children had a risk of dyslexia, with either an older sibling or one or both parents diagnosed with dyslexia, which can increase a child’s risk of reading challenges. For the first year of the study, the babies peacefully slept through the scan, tucked into the MRI machine wearing noise protection (“We got really good at putting other people’s babies to sleep,” Gaab said). 

Harvard researchers use an MRI scan to determine developmental trajectories for children starting at birth. (Harvard Graduate School of Education)

At 18 months old, the babies came back for another scan, though “peacefully sleeping” was becoming a fond memory. By the time the babies were toddlers, the researchers took a break, for reasons any parent of unruly toddlers can understand. The children returned when they were a more cooperative 4 years old and every year after until age 10. 

The study also assessed such factors as cognitive abilities, literacy environment and home language. Funded by the NIH, the researchers aimed to continue for another five years and follow the participants into high school. Though the grant application had received a fundable score at NIH, future funding is uncertain due to the Trump administration’s termination of NIH grants to Harvard.

Building the Brain’s Architecture

Babies are born with the raw material they need to hear, see, move and remember. The nerve fibers, or axons, that connect these disparate brain regions don’t grow automatically. They are cultivated by babies’ environments. MRIs of the participants as infants showed predictably smaller brains that appear more solid or smooth in the images. By the time the children were 5, the scans showed a robust network of branching pathways of these nerve fibers, said coauthor Turesky.  

“The infant brain is very different compared to all other stages of life,” he said. “But if you look at the scan of a child at 5 years and then at 10 years, you can see there’s hardly any change in [those pathways]. Those early years are a time of very rapid growth.”

Brain images from MRI scans showing that the passage of five years earlier in life results in far greater brain growth as compared to five years later in childhood. (Harvard Graduate School of Education)

Though the human brain remains plastic and mutable for a lifetime, Turesky said, the scans underscore that earliest years are the busiest for building brain architecture — a fact that has important policy implications for early intervention and improved literacy curricula in preschools. 

Giving Them the ‘Good Stuff’

Some brains are better equipped to build the neural scaffolding that ultimately leads to reading, Gaab said, and some brains are less optimized, which means those children might struggle to read. It doesn’t mean their brains are faulty, or that there is something seriously wrong with them. 

“They’re built differently, and they’re optimized for other things, because every brain is different,” she said. “But it does point to the need for good early pre-reading instruction and the games and good oral language input, and home and school environment interactions that we know build these connections. Some brains just need more of the good stuff.”  

“Call it preventative education, just like preventative medicine,” she said. “Help these kids build these connections before they struggle and prevent them ever seeing a special educator or ever getting a dyslexia diagnosis.” A large number of studies now show that early intervention and prevention are leading to better outcomes for children at risk of dyslexia, Gaab said, and the research has led to some major policy changes aimed at early identification and intervention. 

That includes teaching the specific skills that can close the gap between proficient and struggling readers. Those skills include phonological awareness, letter-sound knowledge, rapid automatized naming, vocabulary and oral language comprehension. This teaching takes place naturally when caregivers read aloud to their children. Reach Out and Read, the nonprofit Klass leads, has a network of clinicians who work directly with pediatric care providers to help them integrate read-aloud experiences into their interactions with parents and provides developmentally appropriate books for caregivers to take home. 

“Our tremendous advantage in pediatric primary care is that the clinicians see the children over and over in these early years,” Klass said. “We see them for a newborn visit and a one-month, a two-month visit … The schedule is sort of engraved on all our hearts, so we get to talk with the parents about reading and early literacy repeatedly during those early years of life. 

“We know that the developing brain is shaped most of all by the interactions with the adults taking care of that child, Klass said. “The wonderful thing about this study is that it literally looks at the building of the brain and says very clearly that it’s not just that the brain is being built, but the specific structures that will allow the child to read.” 

If doctors can identify young children who are going to struggle more with learning to read as they get older, they can target those families with books and other support early on, Klass added.

“We’re hoping with…the books the caregivers are taking home, the child is learning a motivational lesson: ‘I like books. If I carry a book and give it to my parent, they might sit down and talk to me in that voice,’” Klass said. 

Klass said no one needs to tell parents to “teach” this idea to their children. The children will sort it out if they grow up around books and reading. A baby doesn’t want or need an authority on literacy to walk through the door and teach them how to read, Klass said. A baby wants their parent’s voice, presence and back-and-forth interactions. 

“Your baby wants to be on your lap hearing you read. Your baby will love books because your baby loves you.”