Babies might not be the best conversation partners. But just because they can’t articulate themselves, that doesn’t mean they’re not listening to you. Furthermore, new research is making a solid case to engage babies with more speech: it helps to shape and develop their brain structure.

Scientists have long recognized the benefits of talking to young children, as it aids in language development and vocabulary expansion. However, this new study delves deeper, revealing a fascinating relationship between the quantity of adult speech children are exposed to and a crucial substance in the brain called myelin, which plays a vital role in improving the efficiency of nerve signals.

Words and the developing brain

Researchers, led by Prof. John Spencer from the University of East Anglia, used a device cleverly fitted inside a vest to record the amount of speech to which 87 six-month-old infants and 76 thirty-month-old toddlers were exposed at home. Overall, the team logged 6,208 hours of speech.

Next, 84 children from both cohorts visited a hospital. Once the children were fast asleep in a specially designed quiet room, the team sprang into action. Stealthily, they lifted each child onto a trolley and carefully transferred them to the MRI scanning room, where their brains were scanned.

These brain scans served to measure the amount of myelin in each child’s brain. Comparing the speech and myelin data revealed a compelling connection between adult speech exposure and myelin concentrations in the brain.

As the brain develops, myelin naturally increases. But surprisingly, the study revealed contrasting outcomes for six-month-old infants and thirty-month-old toddlers.

The research indicated that larger amounts of adult speech were associated with higher myelin concentrations in the language-related pathways of the brain for thirty-month-olds. However, for their younger counterparts, greater exposure to speech correlated with lower concentrations of myelin.

To explain this intriguing discrepancy, Prof. Spencer proposed that the impact of speech on brain development may depend on the brain’s stage of growth. During infancy, when the brain experiences rapid neuron growth, increased input could serve to prolong this critical period. However, at thirty months, the brain enters a different phase, where it begins to prune away unnecessary connections and form specific ones. Myelin plays a vital role in this stage, helping to structure the brain and facilitate efficient communication within neural pathways.

So does this mean you should talk less to young babies and more to toddlers? Not necessarily. This research is very much a work in progress.

Causality between speech and myelination shouldn’t be assumed outright, as the reverse was observed in infants around six months old. Future studies should examine whether greater myelination in these brain regions has any bearing on language and cognitive development in the long term.

Another important caveat is that children who receive more exposure to language at home and exhibit higher myelination may simply have inherited genes associated with greater linguistic abilities.

The study also revealed that the associations between speech exposure and myelin concentrations were more pronounced, particularly in the right hemisphere of the brain, for children of highly educated mothers. This may be perhaps because mothers with more education may have a more expanded vocabulary or may simply have more to share in speech.

“The cool thing will be if the six-month-old kids who show that negative relationships turn into 30-month-old kids who show a positive relationship,” Professor Spencer told The Guardian.

How to talk to babies

“It might feel a bit odd to chatter on and on to a six-month-old – clearly, they don’t understand everything you are saying. But gradually, hour by hour and day by day, it all adds up. All that chatter matters,” the researcher wrote in an op-ed for The Conversation.

Professor Spencer stresses that the way we talk to babies and toddlers matters, and different approaches yield varying outcomes.

In the early stages, the quantity of language exposure plays a significant role. Research indicates that children raised in language-rich environments tend to have an advantage in language development. However, this advantage stems from direct interaction with the child rather than conversations overheard between others.

As children grow older, the focus shifts to the quality of conversations. Engaging in high-quality, turn-taking exchanges with caregivers proves immensely beneficial. These conversations are contingent, meaning they are responsive to the child’s actions, and vice versa.

By joining in and following the child’s lead during play, caregivers can initiate these interactions. Naming objects, highlighting colors and shapes, and incorporating playful sounds all contribute to capturing their attention and establishing connections between words and objects.

Parents are encouraged to talk to their children, follow their lead, and engage in silly verbal games together. In doing so, you’ll not only foster their language development but also enjoy the journey alongside them.

The findings appeared in the Journal of Neuroscience.