Brain architecture: foundations first

Your baby's brain is built from the bottom up

The Harvard Center on the Developing Child describes the brain as being "built over time, from the bottom up," the way a house is built: simple connections and skills form first, and more complex circuits and skills are added on top of them later. The connections that form early give either a strong or a weak foundation for everything that comes after.

Genes provide the basic blueprint for how brain circuits form, but experience decides which circuits get used — and which grow stronger. Repeated use strengthens the circuits a child uses most often, based on their everyday experiences. That means your baby's brain architecture is not fixed at birth: it is actively shaped by what happens in these earliest years, day after ordinary day.