General brain development

General brain development
Discover how quickly your little one’s brain develops in the first few years of life.

During early childhood, and even before birth, a child’s brain experiences intense growth. As children this age have so much to learn, more neural connections are made during this period than at any other stage of their life. Here’s a look at what’s happening inside your little one’s noggin.

A brain in the making

A child’s brain begins to form while they’re still in the womb. Several thousand neurons are created every second. When a baby is born, their brain has about 100 billion neurons—all the neurons they’ll need throughout their lifetime, and then some.

For the brain to function, these neurons have to connect to one another. The very first connections are made when the baby is still in the womb. A baby hears sounds and voices, moves their body, and feels the amniotic fluid around them, and this stimulation helps strengthen the connections between neurons.

At birth, their brain weighs about a quarter of what it will weigh when they reach adulthood. During their first year, their brain doubles in size, and will triple by the time they’re 3 or 4 years old. Every new milestone your child reaches and new skill they learn is a sign of this incredible growth. Smiling, babbling, holding a spoon, playing, walking—all these abilities are linked to brain development.

Critical connections
Neurons form connections in response to environmental stimuli. These connections are called synapses. Every kiss, every diaper change, every game—in short, every experience impacts the creation of new synapses. These connections are essential to the development of your child’s brain.


Every time your little one learns something new, connections form in their brain. Billions of these connections will be created throughout your child’s first years.

As some of these connections are formed, others are strengthened, while those that aren’t being used are eliminated. The brain’s ability to “rewire” its own connections is called neuroplasticity.

When children get enough stimulation, have varied experiences, and are surrounded by people who love and take care of them, their brains develop better.

Synapses that are used the most become stronger, and those that are faulty or unnecessary are pruned. By getting rid of certain connections, the brain becomes more efficient.

The brain is at its most flexible, or “plastic,” during early childhood, when it’s developing rapidly. As a child grows and learns new things, their brain adapts to accomodate their experiences.

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

How environment impacts the brain

During early childhood, the brain’s ability to modify its connections has its advantages, but also makes it more vulnerable. 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 the brain doesn’t develop as well.

That’s why the first few years of life are so important for brain growth and why parents play such a big role. Whenever you care for your child, comfort them, give them affection, talk to them, or play with them, you’re helping their brain develop properly.

Your little one also needs to eat well! Breast milk, for example, is rich in essential fatty acids that may promote healthy brain development. A number of studies have found that breastfed children perform better on intelligence tests. It’s thought that breast milk accelerates cognitive development. However, the beneficial effect seems to diminish over time.

Making sure your child gets a good night’s sleep is also a way to promote brain development. When your child sleeps, their brain keeps working. It consolidates what they learned by storing it in their memory and continues to build new connections.

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 around the age of 25. After that, our brains continue to make and break connections, but more slowly than during early childhood.

The role of genetics
A child’s brain development is influenced by a complex interaction between their genes and environment. 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.

Is stress bad for the brain?

The first day of daycare, a doctor’s appointment, moving to a new home—when children experience stressful situations, their brains trigger the production of a stress hormone called cortisol. This hormone helps them adapt to the situation and cope better.

Normal, everyday stress is useful. But stress becomes harmful when it’s prolonged, frequent, and intense. This is called chronic or toxic stress. For instance, a child who is abused or who witnesses serious family conflicts may experience toxic stress.

Developing brains are more vulnerable to this type of stress. A chronically stressed child may be at greater risk of developing mental health problems later on. But there is hope, because children’s brains are highly adaptable! Many studies show that care, affection, and strong relationships in early childhood can offset the negative effects of chronic stress.

A shaken baby means a brain at risk
Shaken baby syndrome happens when someone forcefully shakes a baby. The baby’s head swings in all directions, causing the brain to move inside their skull. As the brain is soft and fragile, it can bleed and swell. Shaking a baby is incredibly dangerous: one in five babies who are shaken will die. Others may suffer permanent damage, such as vision loss, paralysis, epilepsy, cognitive deficiencies, developmental delays, or behavioural issues. If you feel like you’re going to lose control because your baby won’t stop crying, put them in their crib and walk away. If you can, ask someone else to take over or call someone to talk about your feelings. Make sure you’ve calmed down before you pick up you baby again.

Things to keep in mind

  • Most of the brain’s neuronal connections are made during early childhood.
  • A child’s brain adapts and develops according to what they learn.
  • The attention and affection you give your child, and the interactions you have with them, help their brain develop properly.


Naître et grandir

Research and copywriting: Nathalie Vallerand
Web adaptation: The Naître et grandir team
Scientific review: Dr. Tuong-Vi Nguyen, Assistant Professor, Department of Psychiatry, Faculty of Medicine, McGill University
November 2018


Photos: GettyImages/olesiabilkei and PeopleImages


Sources and references

Note: The links to other websites are not updated regularly, and some URLs may have changed since publication. If a link is no longer valid, please use search engines to find the relevant information.

  • Encyclopedia on Early Childhood Development. “How can we support optimal brain development in infants?”
  • The brain from top to bottom.
  • Sunderland, Margot. The Science of Parenting. DK, 2016, 304 pp.