Your brain's busiest construction project was over before your third birthday. During your first few years of life, it formed millions of new synapses every second. By the time you were a toddler, some regions of your brain contained roughly twice as many synapses as they do today.

During the first few years of life, your brain goes into overdrive, forming new connections between brain cells at an astonishing pace. Scientists estimate that, during this period, the brain creates millions of new synapses every second. By the time a child is about two or three years old, some regions of the brain contain roughly twice as many synapses as they will in adulthood.

At that stage, flexibility matters more than efficiency. The brain creates an abundance of connections that experience will gradually refine.

As children explore the world, every sound, face, word, and movement helps determine which connections are worth keeping. Frequently used pathways strengthen, while those that are rarely used are gradually removed in a process called synaptic pruning.

Far from being a sign of loss, this pruning is one of the brain's greatest engineering achievements. 

Instead of carrying around an oversized network forever, the brain streamlines itself, making communication faster, more efficient, and better suited to the life each person actually lives.