3.2.1—Brain development

Brain development is the maturation and reorganisation of neural systems across childhood and adolescence. Growth in connectivity and executive control can change what a person can learn or regulate, but development is not a single timetable.

Genes, nutrition, stress, sleep and social experience interact with maturation. A developmental difference may reflect timing, opportunity or measurement rather than a fixed ability or a simple biological cause.

A teenager may improve planning as fronto-parietal networks mature, while practice and school demands also shape the skill. The same age range contains large individual variation, so averages are not a destiny.

Maturation is not the same as inevitability. Separate biological change, experience, task demands and the evidence used to infer a mechanism.

A critical period is a narrow developmental window in which particular input is required for typical development; a sensitive period is a time of heightened responsiveness when later learning may still occur. Neuroplasticity allows experience to strengthen, weaken or reorganize neural connections within biological constraints. Evidence of poorer outcomes after late input supports a timing effect only when deprivation, opportunity, recovery and alternative explanations are also considered.