Do we only use 10% of our brains?
Where the claim comes from
The film version is a pill that unlocks the “other 90%” and gives you superpowers. Nobody knows exactly where the myth started. It’s often linked to the psychologist William James, who wrote that “we are making use of only a small part of our possible mental and physical resources”, and it’s sometimes attributed to Einstein. James was making a point about potential, not anatomy.
What’s actually true
From Scientific American’s explainer, which quotes neurologists at Johns Hopkins and the Mayo Clinic:
- Virtually all of it is in use. “It turns out though, that we use virtually every part of the brain, and that [most of] the brain is active almost all the time,” said Barry Gordon of Johns Hopkins, who called the myth “so wrong it is almost laughable.”
- Over a day, it’s 100%. Imaging shows that, like muscles, most brain regions are active over a 24-hour period, even in sleep. “Evidence would show over a day you use 100 percent of the brain,” said John Henley of the Mayo Clinic.
- It’s far too expensive to be idle. The brain is about 3% of the body’s weight but uses about 20% of its energy. Evolution doesn’t keep a costly organ that’s 90% unused.
- The grain of truth. At any single moment not every region fires at once. Pouring a cup of coffee, for example, lights up many regions, not all of them. And people who lose part of the brain can sometimes recover because other areas take over. Neither of those means 90% is spare.
The truth
The truth: There’s no hidden 90% waiting for a pill. You already have the whole brain, and it’s already busy. The way to get more out of it is to practise and learn, which doesn’t make a great film but does work.