At birth a baby’s brain is already a quarter of the size of an adult’s brain. In the first few years of life, the brain goes through an incredibly fast period of development. By the age of 5 years, a child’s brain has almost reached the same size as the adult brain! But what will probably really get you thinking is that babies are born with almost all of the 86 billion brain cells that they will have for the rest of their lives.
So, that makes for a bit of a puzzle… how can the brain still increase in size during childhood when the number of actual brain cells is about the same as it will be in adulthood?
Brain cells reach out and talk to each other by making connections with other nearby brain cells. When you learn something new, a new connection is created. As soon as we are born, we experience lots of new and exciting sights, sounds, smells, and tastes from the outside world. All those new experiences cause our brain to make lots of new connections. These connections make ours brains grow rapidly! So rapidly in fact, that by our second year our brain is about 83% of the size of the adult brain! That’s why toddlers have such big heads compared to their bodies!
So that’s it! Even though the number of brain cells is very similar between childhood and adulthood, the number of connections between the cells increases and makes the brain grow.
But is that the end of the story?
Well, no. At three years, something intriguing happens… the brain begins to lose a lot of those connections it has worked so hard it make. This process is called ‘synaptic pruning’ and continues until early adulthood. The brain seems to consider which connections are really needed, and “deletes” those connections that are not used so often.
But what’s the point of creating all those connections, for a lot of them to be thrown away? Well, by creating more connections than are needed, the developing brain is flexible enough to handle all the possible things a child might need to learn. And by ‘deleting’ the connections that are not being used that often, our brain becomes more efficient. Interestingly, this doesn’t cause our brains to shrink back to baby size. In fact, the space that opens up allows the connections that we do use a lot to be strengthened.
This process of keeping some connections and losing others depends completely on the experiences a child has. So, when children have a stimulating environment this supports this natural process and gives them an abundance of healthy brain cell connections that will help them navigate the world in the future.