Short Wave When is your brain actually an "adult"?
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Jan 14, 2026 
Duncan Astle, a neuroscientist and professor at the University of Cambridge, dives into brain development and connectivity. He discusses a study revealing four turning points in brain maturation, suggesting that full adulthood may not be reached until around 32. Duncan explains the growth in brain connectivity during childhood and the ongoing myelination up to age 32, which enhances efficiency. He also links prolonged brain development to adolescent impulsivity, providing valuable insights for parents on adapting to their children’s evolving needs.
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Cringing At Your 20s Self
- Regina Barber recalls feeling mature in her 20s and now cringing at small past behaviors.
- Her example illustrates common retrospective embarrassment as judgment systems mature.
Cortex Thinning Is Developmental
- The cortex peaks in thickness around age 3–4 and then thins, with the frontal lobe finishing thinning around age 25.
- This thinning reflects developmental reorganization, not simple decline, and shapes cognitive control.
Adolescence Extends To About 32
- Analysis of 4,000 MRIs reveals four lifespan turning points with a prolonged 'adolescent' phase lasting until about 32.
- From 9 to 32 the brain prioritizes myelination of long-range connections to integrate distant regions efficiently.