You may have heard that humans only use ten percent of their brain and that if you could unlock the rest of your brainpower, you could do so much more. You could become a super genius, or acquire psychic powers like mind reading and telekinesis.
This “ten-percent myth” has inspired many references in the cultural imagination. In the 2014 movie Lucy, for example, a woman develops godlike powers thanks to drugs that unleash the previously inaccessible 90 percent of her brain.
Many people believe the myth, too: about 65 percent of Americans, according to a 2013 survey conducted by the Michael J. Fox Foundation for Parkinson’s Research. In another study that asked students what percentage of the brain people used, about one-third of the psychology majors answered “10 percent.”
Contrary to the ten-percent myth, however, scientists have shown that humans use their entire brain throughout each day.
There are several threads of evidence debunking the ten-percent myth.
Neuropsychology
Neuropsychology studies how the anatomy of the brain affects someone’s behavior, emotion, and cognition.
Over the years, brain scientists have shown that different parts of the brain are responsible for specific functions, whether it’s recognizing colors or problem-solving. Contrary to the ten-percent myth, scientists have proven that every part of the brain is integral to our daily functioning thanks to brain imaging techniques like positron emission tomography and functional magnetic resonance imaging.
Research has yet to find a brain area that is completely inactive. Even studies that measure activity at the level of single neurons have not revealed any inactive areas of the brain.
Many brain imaging studies that measure brain activity when a person is doing a specific task show how different parts of the brain work together.
For example, while you are reading this text on your smartphone, some parts of your brain, including those responsible for vision, reading comprehension, and holding your phone, will be more active.
Some brain images, however, unintentionally lend support to the ten-percent myth because they often show small bright splotches on an otherwise gray brain. This may imply that only the bright spots have brain activity, but that isn’t the case.
Rather, the colored splotches represent brain areas that are more active when someone’s doing a task compared to when they’re not, with the gray spots still being active but to a lesser degree.
A more direct counter to the ten-percent myth lies in individuals who have suffered brain damage – like through a stroke, head trauma, or carbon monoxide poisoning – and what they can no longer do, or do as well, as a result of that damage. If the ten percent myth is true, the damage to many parts of our brain shouldn’t affect your daily functioning.
Studies have shown that damaging a very small part of the brain may have devastating consequences. If someone experiences damage to Broca’s area, for example, they can understand the language but can’t properly form words or speak fluently.
In one highly publicized case, a woman in Florida permanently lost her “capacity for thoughts, perceptions, memories, and emotions that are the very essence of being human” when a lack of oxygen destroyed half of her cerebrum – which makes up about 85 percent of the brain.
Evolutionary Arguments
Another line of evidence against the ten-percent myth comes from evolution. The adult brain only constitutes two percent of body mass, yet it consumes over 20 percent of the body’s energy. In comparison, the adult brains of many vertebrate species – including some fish, reptiles, birds, and mammals – consume two to eight percent of their body’s energy.
The brain has been shaped by millions of years of natural selection, which passes down favorable traits to increase the likelihood of survival. It is unlikely that the body would dedicate so much of its energy to keep an entire brain functioning if it only uses 10 percent of the brain.
The Origin of the Myth
Even with ample evidence suggesting the contrary, why do many people still believe that humans only use ten percent of their brains? It’s unclear how the myth spread in the first place, but it has been popularized by self-help books, and may even also grounding in older, flawed, neuroscience studies.
The main allure of the ten-percent myth is the idea that you could do so much more if only you could unlock the rest of your brain. This idea is in line with the message espoused by self-help books, which show you ways you can improve yourself.
For example, Lowell Thomas’s preface to Dale Carnegie’s popular book, How to Win Friends and Influence People, says that the average person “develops only 10 percent of his latent mental ability.” This statement, which is traced back to psychologist William James, refers to a person’s potential to achieve more rather than how much brain matter they used. Others have even said that Einstein explained his brilliance using the ten-percent myth, though these claims remain unfounded.
Another possible source of the myth lies in “silent” brain areas from older neuroscience research. For example, in the 1930s, neurosurgeon Wilder Penfield hooked electrodes to the exposed brains of his epilepsy patients while operating on them. He noticed that some brain areas caused his patients to experience various sensations, but that others seemed to experience nothing.
As technology evolved, researchers later found that these “silent” brain areas, which included the prefrontal lobes, did have functions after all.
Putting It All Together
Regardless of how or where the myth originated, it continues to pervade the cultural imagination despite an abundance of evidence showing that humans use their entire brain. However, the thought that you could become a genius or telekinetic superhuman by unlocking the rest of your brain is, quite admittedly, a tantalizing one.
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