We only use 10% of our brains

We use essentially all of our brain. Functional MRI scans across two decades have shown that even simple tasks (reading, walking, scratching your head) activate widely distributed networks across both hemispheres, and that almost every region of the brain has documented activity in some task or other across the day. Damage to even small areas, the size of a peanut, produces specific and often catastrophic deficits, which would not be the case if 90 percent were spare capacity. The 'ten percent' figure has no scientific origin; the closest plausible source is a 1907 William James line that humans use 'only a small part of their possible mental and physical resources,' which got mangled into a numeric claim by self-help authors decades later. Einstein never said it. The brain is the most metabolically expensive organ in the body, consuming about 20 percent of your daily calories. Evolution does not pay that bill for spare hardware. The whole organ is on. The 'untapped potential' idea is appealing, marketable, and roughly as accurate as saying you only use 10 percent of your liver.