MYTH: "We only use 10% of our brain." Verdict?

DEBUNKED. Imaging shows essentially all brain regions are active across a normal day, and the brain is metabolically expensive precisely because it's all in use.

The whole organ pulls its weight: the brain consumes about 20% of the body's energy while making up only about 2% of its mass — an absurd evolutionary cost for something 90% idle. Different regions activate for different tasks, but over a day essentially all of it lights up.

The myth is often misattributed to William James, who actually said something quite different — that most people use only a small fraction of their mental potential. "Unused potential" got mangled into "unused brain."