By Nathalie Vallerand

Before birth and during early childhood, babies undergo rapid brain development, for everything they experience is brand new. Here’s a look at what’s happening inside your little one’s head.

Babies grow so fast! A few weeks after they’re born, their first pyjamas are already too small. And though the process is invisible to the naked eye, their brains are growing just as quickly.

A newborn’s brain weighs about a quarter the weight of an adult’s brain. “During the first year of life, the brain doubles in volume, and between ages 3 and 4, it triples,” says Miriam Beauchamp, director of the ABCs Developmental Neuropsychology Laboratory at Université de Montréal and CHU Sainte-Justine. Every new milestone your child reaches or new skill they learn is a sign of this growth. Smiling, babbling, holding a spoon, playing, walking—all of these are linked to the development of their brain.

Even in the womb, a baby’s brain is growing. Several thousand neurons are created every second. When a child is born, their brain has about 100 billion neurons—all the neurons they will need throughout their lifetime, and more.

For the brain to function, these neurons have to connect to one another. The first connections occur before birth. “In the mother’s womb, babies hear sounds and voices: they move and feel the sensation of the amniotic fluid,” says Beauchamp. “These stimulations help improve the connections between the neurons.”

Neuroplasticity

After birth, neuron connections continue to multiply. Billions of them will be created throughout your child’s first years. Every time your little one learns something, connections form in their brain. From birth to age 3, a million new connections form every second. While this is happening, other connections solidify, and still others (those that aren’t being used) are eliminated. The brain’s ability to “rewire” its own connections is called neuroplasticity.

“The connections that are used the most become stronger, and those that are unnecessary or deficient are eliminated,” says Beauchamp. “It might seem strange that the brain gets rid of certain connections, but it’s a necessary process. It makes the brain more efficient. Think of it as a tree that you make stronger by pruning the damaged branches.”

The brain is at its most pliable during early childhood, when it’s developing most rapidly. As a child grows and learns new things, their brain adapts to accommodate their experiences.

This neuroplasticity can also help a child recover after a brain injury or brain disease. For instance, if an injury occurs in one area of the brain, neurons in other areas may take over and make new connections. “That doesn’t mean there won’t be consequences for the child,” warns Beauchamp. “Their brain will try to recover, but unfortunately, depending on the severity of the situation, there could be negative physical, cognitive, social, or behavioural effects.”

Environmental influences

The brain’s ability to modify its connections has advantages, but it also carries some risk. Upsetting experiences will affect a young child’s brain more than that of an older child. Likewise, when a young child is understimulated, fewer neural circuits are used and their brain doesn’t develop as well. Since they aren’t being reinforced, these connections can end up being eliminated.

Because the early years are so important for a child’s brain development, parents have a critical role to play. When you care for, comfort, and give affection to your child, and when you talk to and play with them, you are helping their brain develop properly.

Your baby also needs adequate sleep and nutrition. “When your child is asleep, their brain is resting, but it’s not inactive,” says Beauchamp. “The brain consolidates what it has learned by committing it to memory and continues to make connections between neurons.”

What role does genetics play in brain development? “Brain development is the result of a complex interaction between genes and the environment in which a child is raised,” says Linda Booij, full professor in the Department of Psychiatry at McGill University and a researcher at the Douglas Research Centre and the CHU Sainte-Justine research centre. “Gene activity can be altered by a child’s experiences. This is true even before they’re born. That means that what happens during pregnancy can influence the genes of the unborn baby.”

When does a child’s brain stop growing? Science doesn’t have all the answers to this question yet. What we do know is that most areas of the brain reach maturity between the ages of 20 and 25. After that, connections continue to be made and unmade, but much more slowly than during childhood.

Your baby may not be walking yet, but there’s plenty of action happening in their brain. With every stimulation, the connections between their neurons get stronger.

Different areas of the brain develop at different speeds. At birth, some areas are already more advanced than others, including the regions dedicated to the five senses. This is normal, as these are the areas the baby needs most in the beginning.

“All of a baby’s stimulation comes through the senses,” explains Sarah Lippé, neuropsychologist, full professor, and director of the Neuroscience of Early Development Lab at Université de Montréal and CHU Sainte-Justine. “For instance, when you sing to your child and hold them in your arms, their sensory receptors send information to the brain, which strengthens connections between the neurons. When multiple senses are stimulated at the same time, the brain receives information through multiple pathways.”

Everyday routines, such as diaper changing, feeding, and bathing, are all opportunities to stimulate your baby’s senses and get the brain working. It’s the same when you talk to your child, cuddle them, rock them, look them in the eyes, or take them for a stroll. These kinds of interactions are essential for healthy brain development.

When he gets home from work, Charles, the father of 6-month-old Léonie, has a little ritual: he spreads out a bunch of stuffed animals, toys, and pillows on a blanket and plays with his daughter. He makes funny sounds, tickles her, has her play on her belly, lifts her gently in the air, and lets her feel different textures. “When Léonie sees her dad come home, she’s so happy,” says her mother, Emma. “She smiles, waves her arms and legs, and makes excited noises—she knows what’s about to happen!”

Development in all areas

A stimulating and nurturing environment helps babies feel secure and fosters their growth, mental development, and learning. When you see your child progressing in different areas, you know their brain is developing properly.

“The first smiles will appear around 2 months,” says Miriam Beauchamp, director of the ABCs Developmental Neuropsychology Lab at Université de Montréal and a researcher at the CHU Sainte-Justine Research Center. ”At this age, babies can also imitate some of their parents’ gestures, like sticking out their tongue. At 3 months, they start to look you in the eyes.”

This is also when children start to experiment with sounds. At 6 months old, little Léonie babbles a lot. “In the past few days, she’s started making higher-pitched and more varied sounds,” says Emma. “She’s also making sputtering noises with her mouth, like she’s trying to talk.” Experimenting with sounds helps babies develop their language skills.

Léonie’s hand-eye coordination has also improved a lot recently. “She looks at the buttons or whiskers on her stuffed animals and can now reach out and touch them,” says Emma. This shows that Léonie’s brain is letting her make more precise movements, using visual information (a stuffed animal’s whiskers, for instance) to guide her hand to the object she’s interested in.

During a baby’s first year, major changes also occur in the areas of the brain related to motor skills. That’s how, as uncoordinated as they are at birth, infants begin taking their first steps after about 12 months!

Soothe your baby when they cry

Progress is slower when it comes to controlling emotions. “The areas of the brain that produce emotions function right from the start,” says Lippé. “The areas that manage emotions, however, aren’t developed yet and are poorly connected to other areas of the brain.” That’s why babies cry so often. Babies don’t cry for no reason—it’s their only way of letting you know that something is wrong.

That’s also why it’s important to soothe babies when they cry. When you provide reassurance, you’re helping their brain develop properly, allowing the connections between the brain’s neurons that help manage stress and strong emotions to develop and strengthen. When you comfort your baby when they cry, their brain also produces oxytocin, a hormone that has a calming effect.

As communication between the different parts of the brain improves, children can begin to acquire new skills.

Significant physical progress occurs between the ages of 1 and 3. Toddlers are now able to walk, and they develop all kinds of other physical abilities. “My son can kick a ball now,” says Julie, mother of 20-month-old Émile. “He used to miss it all the time. In the past few days, he’s also started walking down the stairs while holding the railing instead of coming down on his behind.”

Despite their new physical abilities, children at this age still have no notion of danger. “Émile climbs on everything from the kitchen table and chairs to big toys,” says Julie. “Everything is a ladder to him—you can’t let him out of your sight!”

Making themselves understood

The period between 18 and 24 months is marked by significant language development. This is in part because the neurons and connections in a child’s brain are changing, such that information can travel faster through the areas of the brain related to language.

Émile’s parents have noticed that their little boy is talking more. He’s recently started to use two- or three-word sentences, such as “Gimme milk,” “No, not that,” and “Where are you, Daddy?” “He also tries to repeat what we say, even three-syllable words,” says his mom. “And when he gets it right, he claps his hands.”

In a few months, Émile should be able to make himself understood—like Raphaël, who will soon be 3 years old. “When he comes home from daycare, he tells us about his day, like how he went to the park or how the teacher told him not to push his friends,” says Gabriela, Raphaël’s mom. “He speaks French, but he also understands Spanish.” Since he started speaking, Raphaël has had fewer outbursts because he can finally express himself.

Learning to think

Between ages 1 and 3, children continue to develop their mental capacities, which will eventually allow them to learn more complex things. The area of the brain that is responsible for reasoning, planning, problem solving, taking initiative, and controlling impulses is developing. Known as executive functions, these processes are mainly controlled by the prefrontal cortex. This highly complex region is located at the front of the brain and continues to develop until adulthood.

“Executive functions aren’t fully developed until adulthood, but they start to appear gradually around the age of 2,” says Sarah Lippé. “For example, when a child pretends to change a doll’s diaper, they have to carry out a sequence of actions. That requires using their executive functions.”

Young children develop their executive functions, as well as all other intellectual, social, and motor skills, through play. Raphaël, for example, does a lot of puzzles. Puzzles improve concentration, thinking skills, and the ability to perceive and conceptualize visual information. He also plays children’s board games with his parents. “At first, we had to keep reminding him that everyone has to take turns,” says Gabriela. “Now, he’s getting better and better at waiting his turn."

Because their prefrontal cortex has yet to mature, children at this age have quite a bit of difficulty controlling their emotions and impulses. “Parents have an important role to play—they have to put words to what their child is experiencing,” explains Lippé. “Telling them that they are angry or sad and explaining why helps children understand what’s going on inside them. They’ll have an easier time recognizing their emotions the next time. It’s also a good idea to give them strategies for managing their emotions.”

Young children also learn a great deal by imitating the people around them. By modelling appropriate behaviour and emotional regulation, parents can help foster their child’s emotional development.

Your child’s brain is processing information more and more quickly, which leads to a sudden jump in intellectual ability.

One of the reasons children develop so quickly at this age is the increase in a substance known as myelin, a white coating that speeds the transmission of signals between neurons. “The brain is able to process information faster, which leads to improved intellectual, emotional, social, and motor skills,” explains neuropsychologist Sarah Lippé. The white matter in your child’s brain will continue to form until about the age of 25.

Mastering language

Children between the ages of 3 and 5 are rapidly building their vocabulary. Their sentences become longer, and their pronunciation becomes clearer. Ophélie, age 3½, now forms sentences that have a subject, verb, and complement. “The structure of her sentences has gotten a lot better over the past few weeks, but she still struggles a bit with pronunciation,” says her dad, Guillaume. “She hates when people don’t understand her!” Proper pronunciation isn’t learned overnight. By the age of 5, most children have mastered the basics of language and are able to make themselves understood.

Learning to reason . . . more or less

The changes taking place in a child’s brain between the ages of 3 and 5 open the door to different and more complex games. Increasingly, children will play with a goal in mind, like building a house. This gets kids thinking about the best approach to take and how to overcome any bumps in the road.

During this stage, children typically love to play make-believe. Ophélie, for example, often plays house with her 7-year-old sister. “She’ll play every role: mom, dad, baby—even the family dog!” says her dad. “She develops each character by having them do all kinds of activities. She also imitates what she sees going on around her. We’re having work done on the house, and last time, she went around pretending to fix the windows.”

Play has countless benefits for little ones: stimulating creativity, memory, independence, initiative, and decision making. It is also extremely important on a social level. Playing with others is how children gradually learn to share, work together, wait their turn, negotiate, put themselves in other people’s shoes, and follow rules (though this can still be challenging before the age of 5).

It is for all these reasons that your toddler should be given as many opportunities as possible to play with other kids. However, children under the age of 5 still have difficulty finding the right strategies and applying the solutions they are given to resolve conflicts. In other words, your child still needs your guidance.

Source: Naître et grandir magazine, September 2018 Research and copywriting: Nathalie Vallerand Scientific review: Anne Gallagher, full professor of psychology in the Department of Psychology at Université de Montréal and director of the Neurodevelopmental Optical Imaging Laboratory (Lionlab) at CHU Sainte-Justine. Updated: January 2024

Photos : GettyImages/krystynataran, Nicolas St-Germain, Maxim Morin, GettyImages/alina555