Do we really only use 10% of our brains?

Specific areas of the brain handle specialised tasks. Even if the activity is high in some parts of the brain while you are reading this text, the rest of the human brain is not completely shut down. It’s running all the time, but more like in a “standby mode” ready to process information.

The long-standing myth stating that the typical human only uses 10% of their mental capacity is one of the most pervasive myths in medical history. Within it lies all kinds of false assumptions that speak volumes about popular misconceptions of neurological science. Exploring this myth makes for a fascinating commentary on how falsehoods perpetuate themselves. 

Possible Origins of Brain myth 

With a nudge and a wink, one might joke that at least some people (insert your least favorite politician here) appear to use only 10% of their brains. That’s one of the things that makes this myth so attractive; the jokes just write themselves. 

The full origins of the myth may forever be lost in history. One early thread we can trace is by Harvard psychologists William James and Boris Sidis in the 1890s, who merely asserted that humans seldom realize their full mental capability – an easily defended claim, as any formal education will demonstrate. These researchers were misquoted in an introduction to Dale Carnegie’s book How to Win Friends and Influence People, where the introduction’s author, Lowell Thomas, misquotes James / Sidis by claiming the 10% figure. 

An advertisement in a 1929 copy of the World Almanac claims, “Scientists and psychologists tell us we use only about TEN PERCENT of our brain power.” Early medical literature is fraught with fraudulent claims like this, especially in the “snake oil” market. 

Another possible source of the misconception is a misquote of the actual fact that at any given point in time, only about 5% of neurons in the brain are actively firing. If 100% of the neurons in the brain are firing at once, we call that a grand mal seizure, and it’s followed by a blackout. Compare it to your house: At any given time, some of the lights are on or off, depending on what’s needed, but just because 90% of the lights in your house are off doesn’t mean your house is 90% unused. 

Popular Media Usage 

Along came the Internet, and this quote has falsely been attributed to the likes of Albert Einstein (if I got a dollar for every quote Einstein supposedly said..), anthropologist Margaret Mead, and self-help author Dale Carnegie, among many others. 

Media has not helped, especially since the “10% myth” is such a handy plot device. As recently as the episode “Black Museum” from the 2017 run of the sci-fi anthology Black Mirror, a museum host bumps it up to saying we only use 40% of our brains in a throw-away explanation about housing the consciousness of one human in the brain of another. 

The 2014 sci-fi thriller Lucy is an especially egregious case, taking this myth as the starting point for a story about a female who discovers how to unlock the remaining 90% of her brain to become superhuman. The myth is printed verbatim right on the film poster. The film spawned a number of parodies, such as substituting the myth of humans swallowing eight spiders per year. 

In the 1966 John Travolta film Phenomenon, the myth is used to justify Travolta’s character developing mental superpowers. The fact that Travolta had been a noted Scientologist at the time should bear reflection; Scientology takes untapped brain potential as part of its doctrine. 

The 2010 sci-fi thriller Inception also invokes this trope, while dealing with humans who are able to dive into other people’s minds and manifest in their dream worlds while they sleep. 

There are near-countless more examples out there, especially in comic books, science fiction, paranormal X-Files plots, or anyplace where you’d need to explain a human gaining mental powers or otherwise exploiting untapped brain reserves

How We Really Use Our brain

If we need any evidence of our full utilization of our grey matter, a good pointer is the established fact that our brains use 20% of our body’s available energy, while only being 2% of our body weight. This can explain why we feel more irritable and stressed when we’re hungry. 

Another fact to take into account is that brain power, measured in raw IQ points, is more a matter of how many neurons we have than how many of them are used at once. It’s been shown that the human brain can both lose and gain neurons. The generation of new neurons is called “neurogenesis,” and it’s been established since 1962 that we can grow new neurons pretty much at will, simply by exercising the mind and body. 

In brief, neuroscientist Barry Beyerstein lists the following facts in his book, Mind Myths: Exploring Popular Assumptions About the Mind and brain to refute the 10% myth

• Brain functioning is profoundly impaired by even the smallest brain damage. 

• Brain scans show that 100% of our brain is functioning at all times, just to varying rates of intensity. 

• The above-mentioned 20% brain usage of the body’s energy. 

• The brain has localized functioning, so that different parts are used for sensory processing, memory recall, regulating emotions, and so on

• An electrode inserted into the brain at any point records some activity at all times. 

• Under-utilized brain cells have a tendency to die off, so if we only used 10% of them, autopsies would reveal 90% dead cells in the brain


As the literary figure, Jonathan Swift wrote in 1710, “Falsehood flies, and the truth comes limping after it.” – A quote which, ironically enough, is subject to the same game of cultural misquoting. 

Neuroscience and medical science, in general, is a fertile ground for popular misconception because the average layman doesn’t know enough about these complex subjects, and news media is a sloppy way to stay informed – witness the constantly fluctuating reporting of health news on whether coffee, eggs, or alcohol is good or bad for you. On top of that, the human mind is an inherently difficult object to study; one can’t simply open a hatch and watch the gears turn. You can only dissect a brain once its owner has deceased. And we’re talking about the most complex three pounds of meat in the known universe. Some of our latest research in neuroscience overturns theories we’ve had about the mind for decades

People tend to cling to this myth, especially because there is a plainly evident spectrum of human mental capacity. It’s cited as an inspirational quote to entice others to expect more of themselves. It’s also cited as the validation of all kinds of social ills, and underachieving – there go those lazy kids only using ten percent of their brain again! But most telling about the appeal of popular falsehoods, it’s short. It’s easy to remember. It can fit in a tweet or a film poster. 

Neurological science is a deep subject, far too complex to be summed up in a Twitter tweet. Our understanding of how the human mind works is constantly evolving and doubtless will continue to be a frontier of new understanding. 


The Straight Dope trashed this myth in a column in 1991. 

Scientific American tackles the myth in this article. 

The Center for Sensorimotor Neural Engineering in Seattle, Washington has an article debunking this myth in the “Neuroscience For Kids” section.

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