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LIE NO. 2: WE ONLY USE 10 PERCENT OF OUR BRAINS

We’ve all heard this myth. Some of us heard it for the first time in a classroom, some of us heard it from a friend. Some of us heard it through the media—maybe a documentary, a TV show, or a movie. This myth is
usually used in the context of highlighting longed-for possibilities: If only we could access the rest of our brains, what could we accomplish?
The story has been traced to a number of different sources, but as so often happens in the shaping of public opinion, it’s likely built on by successive events. Some attribute it to author and philosopher William James, who wrote in The Energies of Men that “We are making use of only a small part of our possible mental and physical resources.”⁹ It could have originated with the work of Pierre Flourens, a French physicist famous for his discoveries in the late 1800s about how the brain and the nervous system work and work together.
The myth could also be related to the work of Dr. Karl Lashley in the 1920s; when Lashley removed parts of rats’ cerebral cortex, an area responsible for higher order cognitive processing, he found the rats could still relearn some tasks. This led him to hypothesize —incorrectly—that whole parts of the brain were not necessarily being used.¹⁰ Some blame the earliest neuroimages from PET and fMRI scans, which showed bright blotches on a screen with simplified explanations like “This is what your brain does when you pick something up.” These images typically showed just one portion of the brain lighting up, leading the layperson to conclude that we only use a small portion of our brains at one time.¹¹
This assumption has also been perpetuated in countless ads and movies over the last hundred years. The adaption of the book The Dark Fields, which was produced as Limitless in 2011, says we use 20 percent of our brain function; the 2014 movie Lucy claimed we use 10 percent at any given time. In 2017, an episode of Black Mirror, a show known for its research and well-thought-through use of facts and statistics, touted the myth, saying, “even on a good day, we only use 40 percent of our brain capacity.” All of these storylines were focused on the idea of unlocking our greatest, albeit hidden, potential.
Needless to say, this myth is pervasive, and yet it’s not true.
In a succinct NPR segment, the host plays a clip of Morgan Freeman posing, in his dramatic bass voice, the what-if scenario upon which Lucy is based: “What if there was a way of accessing 100 percent of our brain? What might we be capable of?”
Neuroscientist David Eagleman gives a pointed response: “We would be capable of exactly what we’re doing now, which is to say, we do use a
hundred percent of our brain.”¹²
Countless evidence backs this up—too much of it to include it all here— but Barry Beyerstein, a professor of psychology at Simon Fraser University in British Columbia, described some of the major scientific discoveries that refute this myth, which I’ve paraphrased here:¹³
Studies of damaged brains show that there is no single area of the brain that can sustain damage without a loss of ability, contrary to earlier theories. Brain scans have shown that all brain areas are active, no matter what the activity. Even while we sleep, all parts of our brains show activity.
Our brains are energy-hogs. The brain takes up only 2 percent of space by weight, and yet accounts for 20 percent of energy consumption, more than any other organ. We wouldn’t need such an incredible amount of energy for an organ that functioned at 40 percent or less.
Scientists have also determined that the brain’s regions have distinct functions that work together. After extensively mapping the brain over decades, they’ve concluded that there are no functionless areas of the brain.
Finally, as we’ve learned, the brain uses a process called synaptic pruning. If we didn’t use a large portion of our brains, we would expect to see large areas of degeneration (we don’t—unless brain diseases are present).¹⁴
To sum up, this myth just isn’t true. In an interview with Scientific American, neurologist Barry Gordon from Johns Hopkins School of Medicine in Baltimore, said that the idea is “so wrong it is almost laughable.”¹⁵