Teenage Brain “Work in Progress”

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Teenage Brain “Work in Progress”

Before brain imaging technologies became available, it was widely believed among scientists, including psychologists, that the brain was largely a finished product by the age of 12. One reason for this belief is that the actual size of the brain grows very little over the childhood years. By the time a child reaches the age of 6, the brain is already 90-95% of its adult size. In spite of its size, the adolescent brain can be understood as “work in progress”.

Brain imaging has revealed that both brain volume and myelination continue to grow throughout adolescence until the young adult period (i.e., between ages 20-30).

Brain imaging studies on adolescents undertaken by Jay Giedd at the United States National Institute of Mental Health show that not only is the adolescent brain far from mature, but that both grey and white matters undergo extensive structural changes well past puberty (Giedd et al., 1999; Giedd, 2004).

Giedd’s studies show that there is a second wave of proliferation and pruning that occurs later in childhood and that the final critical part of this second wave, affecting some of our highest mental functions, occurs in the late teens. This neural waxing and waning alters the number of synapses between neurons (Wallis et al., 2004; Giedd et al., 1999; Giedd, 2004).

"Understanding the Brain: The Birth of a Learning Science", 2007, page 45