Developmental Milestones

At birth, the human brain is the most immature organ in the body. It grows rapidly, particularly during the first three years. By age five, the brain has reached 90% of its adult capacity. The structures of the brain involved in learning, memory, motor control and every other brain function are established by age five.

The kind of connections between brain cells, called neurons, depends on how the brain is used, the variety and richness of circumstances it’s exposed to, and genetics.

In the first year of life, when critical emotional components of the brain are formed, a secure and predictable environment is most important, including lots of touching and having needs met promptly. Also, key to brain development in the first three years are being talked to, being played with, and having a varied, stimulating environment — balanced by opportunities to rest, which is when the brain reorganizes itself. These very simple but vital things set the stage for all later learning.

Although most brain development occurs during the first three years of life, the school years continue to support brain development. It’s easy for children to learn, especially from about age 3 to age 6 — not just academics, but social rules, dinosaurs’ complex names, how to play sports and games, directions, how to work gadgets, what goes where. The impulse control and judgment parts of the brain, however, develop later in the school years and aren’t completely activated until after adolescence. Learning is a process that continues throughout life. During the school years, the brain works in concert with the growing body to focus on the development of certain kinds of learning. For example, while language-related synapses in the brain grow mainly in the first three years, learning to speak and understand new words, and eventually write them, happens throughout the school years, especially up to age 10. Basic motor skills continue to develop through about age 12.

Adapted from Your Child’s Growing Brain,

Information about specific ages are available below so you can assess how your child is developing, learn how you can help, and know when to seek professional assessment.