Myth 2 of 10
2. Myth: we only use 10% of the brain
The idea that we leave 90% of the brain idle has no scientific basis. Imaging scans show activity in practically every region over the course of the day, and damage to almost any area causes some effect.
An organ too expensive to sit idle
Scans such as functional magnetic resonance imaging show which parts of the brain work hardest in each task. No task uses everything at once, but over the course of a day practically every region comes into action, including during sleep.
If 90% of the brain were useless, damage to those areas would make no difference. That is not what we see: lesions in almost any part of the brain affect some function, such as speech, memory, vision or movement.
It would also make no sense from the body's point of view. The brain consumes a lot of energy for its size, and keeping tissue without function would be a waste that evolution would hardly have preserved.
The origin of the myth is uncertain. It appears in self-help books from the early 20th century and is often attributed, without proof, to famous scientists, including Albert Einstein. Cinema helped spread the idea, with films about people who unlock the rest of their brain.
Even at rest, the brain remains active. There is a set of regions that works precisely when the mind is free, recalling things, imagining or making plans, and scientists call it the default mode network.
Did you know? What the brain does is learn: it creates and strengthens connections between neurons throughout life. This ability to change with experience is called plasticity.
