Talking to babies could help shape the structure of their growing brains, according to new research.
A study led by researchers at the University of East Anglia in the United Kingdom has found toddlers who hear more speech on the regular have more efficient-looking neurons.
Specifically, brain scans showed that their language-processing regions hosted a greater concentration of myelin – the insulating sheath that surrounds neurons and allows them to send messages faster and more efficiently.
Whether that extra myelin actually impacts a two-and-a-half-year-old's language abilities is unknown, but researchers suspect it could have important benefits.
Myelin wrapped around a neuron, they say, is a bit like putting duct tape on a hosepipe with holes in it. It helps the neuron get more of its signal from point A to point B, strengthening its connection to other neurons.
"Although there is still much more to learn about these processes, the message to caregivers is clear – talk to your baby, your toddler, your child," says John Spencer, a cognitive psychologist at the University of East Anglia.
"Not only are they listening, but your language input is literally shaping their brains."
That message is simple, but it comes with some complex results. In the study, more talk did not always promote greater neuron efficiency in baby brains.
Researchers had more than 140 toddlers and infants wear recording devices over three days. In the thousands of hours of audio recordings collected, the researchers could hear what the children were hearing every day.
Then, the team selected just over half of those children to undergo an MRI scan while napping.
Among the six-month-old infants, greater language input on a daily basis was associated with less myelination – the opposite result of what was found in kids two years older.
That was unexpected, but as Spencer explains, a baby's brain development naturally goes through stages. Sometimes its brain is busy building new cells, whereas other times it's busy refining the cells it has already built.
In the first few years of life, sheer brain growth seems to take the lead. By age two, a person has already acquired a brain volume 80 percent of an adult's.
After that, the pruning and nurturing stages really kick in.
"This suggests that talking matters just as much at six months as at 30 months, but it affects the brain differently because the brain is in a different 'state'," Spencer writes in a recent piece for The Conversation.
At six months, for instance, it's possible that hearing more language might delay myelination and facilitate brain growth instead. For now, however, that's just speculation.
Saloni Krishnan, a developmental cognitive neuroscientist not involved in the study, told The Guardian that more research is needed to understand myelin's role in learning.
"It is not yet clear if greater myelination in these areas is meaningful for future language or cognitive development, or if this is a stable pattern across childhood," she says.
That said, plenty of studies have shown that language exposure is important for a child's language processing, vocabulary, grammar, and verbal reasoning. How those skills translate to processes in the brain, however, remains largely unknown.
What's more, previous studies have found that four- to six-year-olds that have more conversations with adults also show greater myelination in brain regions associated with language.
The new findings extend a similar effect to even younger kids.
More research is needed to understand how those structural changes translate to language learning.
But for now, it's wise to remember: kids are absorbing more of what you say than you might think.
The study was published in The Journal of Neuroscience.