Do People Only Use 10% of Their Brains?
A 2013 poll surveying over 2000 Americans found that 65 percent thought that this statement is true. And yet, the simple and unequivocal answer is: No. Despite a myth so prevalent that it is easily accepted as a pivotal plot point in movies or a motivational tactic or even justification for psychic claims, everyone uses 100 percent of their brain.
There are a number of logical refutations of this myth—why would big brains evolve if they're nothing but dead weight?—but outright proving its fallacy is relatively easy with modern technology. PET and fMRI scans show that even when we're sleeping, our entire brain is active on some level.
But even before imaging techniques allowed scientists to definitively debunk this myth, how did it arise in the first place? And why has it held on into the era of such increased understanding of how the brain works?
Although it's impossible to prove as the exact origin of the myth, there is a traceable misappropriation of a vague claim that seems to be the first written mention. In 1907, prominent philosopher and psychologist William James wrote in The Energies of Man that "We are making use of only a small part of our possible mental and physical resources." He meant—probably—that we all had untapped potential within us, a likely, although hardly inflammatory, assertion. Twenty-nine years later, in the introduction to Dale Carnegie's How To Win Friends and Influence People, Lowell Thomas wrote, presumably referencing that quote, "Professor William James of Harvard used to say that the average man develops only ten per cent of his latent mental ability."
Again, there's no overt neurological claim—mental ability does not mean brain mass—but from here the sentiment seems to have spun off; versions of it found use in the science fiction and spiritual communities. It didn't help matters that in the 1920s and '30s, prominent psychologist Karl Lashley attempted to isolate regions of the brain by removing areas of the cerebral cortex in rats. When he found they were still able to learn and remember specific tasks, it contributed to the idea that there are large swatches of "inactive" brain mass.
Decades later, the myth has persevered because of the attractive possibilty it seems to present. It absolves us for not reaching our full potential, offers a persistent insecurity for self-help gurus to appeal to, and provides a pseudo-scientific explanation for the limits of human comprehension.