Do You Use Only 10% of Your Brain?

We may be biased, but we think the human brain is pretty special. All this week, mentalfloss.com is celebrating this miracle organ with a heap of brain stories, lists, and videos. It all leads up to Brain Surgery Live With mental_floss, a two-hour television event hosted by Bryant Gumbel. The special airs Sunday, October 25 at 9 p.m. EST on the National Geographic Channel.

The simple answer is: No.

This myth is so prevalent that it is unquestioningly accepted as a pivotal plot point in movies, a motivational tactic for self-improvement, or justification for claims about ESP and other supposed untapped abilities of the human mind. A 2013 poll surveying over 2000 Americans found that 65 percent believed the 10 percent myth. A 2007 study in the British Medical Journal (BMJ) found that even some doctors weren't immune to the fallacy. But the truth is that everyone uses 100 percent of their brain.

Proving this idea wrong 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. Our observations of individual neurons or cells reveal no inactive areas of the brain. Metabolic studies of cellular metabolism in the brain show consistent activity as well. "Evidence from studies of brain damage, brain imaging, localization of function, microstructural analysis, and metabolic studies show that people use much more than 10 percent of their brains," according to the BMJ paper. "No area of the brain is completely silent or inactive."

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?

Some attribute its origin to the prominent philosopher and psychologist William James, who in 1907 wrote in The Energies of Man, "We are making use of only a small part of our possible mental and physical resources." He probably meant that we all have untapped potential. 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."

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. We know now the brain's plasticity allows it to recover from such injury and compensate for the loss. That's the very opposite of inactive. 

Decades later, the myth has persevered because of the attractive possibility 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.