The idea that humans only make use of 10% of their brains is widely perpetuated in popular culture. This concept that large areas of the brain remain unused however is unfounded. While there are still numerous mysteries about how brain cells work together, every part of the brain has a known function.
Possible origins of the “10%” myth include;
the reserve energy theories by Harvard psychologists William James and Boris Sidis in the 1890s who told audiences that people only meet a fraction of their full mental potential, and a further mis-quotation of this in Lowell Thomas’ 1936 forward of Dale Carnegie’s How to Win Friends and Influence People,
early neurological researchers used the figure of about 10% to refer to the proportion of neurons in the brain that fire at any given time or to refer to the percentage of the brain’s functions that had been mapped at that time.
In the October 27, 2010 episode of MythBusters, the hosts used magnetoencephalography and functional magnetic resonance imaging to scan the brain of someone taking a complicated mental task. Finding that well over 10% was active at once, they declared the myth “busted”. (wiki)