When are children’s brains viewed as “adult brains”?

Until recently, scientists generally believed the brain does not change much after childhood. However, in the last 15 years, due to advances in brain imaging technologies, neuroscientists have been able to scan the living human brain at all ages to track changes in the brain’s structure and function across the lifespan. This research revealed the human brain continues to develop throughout adolescence and well into adulthood.

So at what age does the brain become adult? The short answer is, we don’t know. There is no magical age at which brain development suddenly stops. The brain is constantly changing, even in adulthood and old age. Whenever you learn anything — a new word, a new face, a new function on your computer — your brain has changed to enable learning. And the brain changes induced by learning in adults look quite a lot like the changes that occur during brain development.

The prefrontal cortex undergoes particularly protracted development during the teenage years and beyond. This brain region is involved in a wide range of high-level mental abilities, including planning, inhibiting inappropriate behaviour, controlling emotions, making decisions, self-awareness, and understanding other people. One finding from MRI studies is that gray matter — which contains brain cell bodies and local connections between cells — in the prefrontal cortex increases in volume during childhood, peaks in adolescence, and then starts to decrease. This decline continues throughout the 20s.

The Question Was Answered By

Sarah-Jayne Blakemore

Professor of Cognitive Neuroscience
University College London