The “brain isn’t done until 25” factoid is based on a funding cutoff

https://boingboing.net/2026/02/19/new-research-debunks-the-brain-at-25-factoid.html

“A large-scale study analyzing more than 4,200 brain scans from infancy to age 90 has since blown past that boundary, according to neuroscientist Taylor Snowden writing in The Conversation. The brain’s network efficiency — a measure researchers call “small worldness” — doesn’t reach its adult configuration until the early 30s, around age 32. After that, those building trends flip direction, and the brain shifts from forging new pathways to locking in the ones it already has.”