Do humans really only use ten percent of their brains?

 Chimp brain

The brain of a chimpanzee. Human brains are approximately three times larger.


Do humans really only use ten percent of their brains? The claim is as old as misinformation, and is the basis for many a science fiction film, to boot.

The idea that human beings only use ten (or so) percent of their brain capacity has been around for a little over a century. Indeed, it’s become somewhat ingrained in popular culture, appearing on the regular in advertisements, television programs, movies, and even books.

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This premise seems to have begun in one of two places. The first is thanks to a mangling of the words of 19th century philosopher William James, Henry’s less windbaggy brother. In his 1907 essay “The Energies of Men,” James observed:


Most of us feel as if a sort of cloud weighed upon us, keeping us below our highest notch of clearness in discernment, sureness in reasoning, or firmness in deciding. Compared with what we ought to be, we are only half awake. We are making use of only a small part of our possible mental and physical resources. In some persons this sense of being cut off from their rightful resources is extreme, and we then get the formidable neurasthenic and psychasthenic conditions, with life grown into one tissue of impossibilities, that so many medical books describe.


The second comes from noted Canadian neurosurgeon Wilder Penfield, who dedicated his life to the study of the brain, and, among other things, pioneered a technique for studying the extent to which damaged areas of the brain are crucial to its function.

One of Penfield’s observations was that the stimulation of only a few areas of the brain–something like 10% of the whole–could lead to a detectable effect in the body: trip the right combination of neurons, and the patient moves his hands, or sneezes, or winces in pain.

It’s not hard to see how either notion could be twisted around by hucksters and producers for their own various ends. A 1956 advertisement for W.B. Germain’s The Magic Power of Your Mind assured potential readers that “The ‘hidden nine-tenths’ of your mental strength lies buried…discover, release[,] and use it to gain new success, personal happiness–a fuller, richer life.”

Post-Germain and pre-Lucy, Michael Clark’s Reason to Believe: A Practical Guide to Psychic Phenomena quotes a would-be psychic named Craig Karges: “We only use 10 to 20 percent of our minds. Think how different your life would be if you could utilize that other 80 to 90 percent known as the subconscious mind.”

Assorted quotes about the unlocked ninety percent of the brain’s potential have also been attributed to Albert Einstein. If you’re looking for an intellectual authority to lend credence to a somewhat dubious notion, Einstein’s a pretty good go-to.

And, finally, the ten percent myth makes a good basis for a summer action movie.

Unfortunately, for those among us with Matrix-like delusions, the idea is incorrect.


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Barry Gordon, a neurologist at Johns Hopkins University in Baltimore, assures us that “we use virtually every part of the brain, and…[most of] the brain is active almost all the time. Let’s put it this way: the brain represents three percent of the body’s weight and uses 20 percent of the energy.”

While every part of the brain is not active all of the time, scientists liken its situational use to that of the human body. You don’t need your arms as much as you do your legs while you’re walking, for example. Or, if you’re sitting in a chair talking to a friend, your facial muscles are much more active than your thighs.

This is also the reason why brain scans will sometimes show areas of high activity contrasted with areas of little or none. Such scans are made while patients perform one or two specialized activities. A short-term memory test would show a great deal of activity in the frontal lobe. Short-to-long-term memory conversion testing would show activity in the hippocampi, and long-term memory testing would activate various areas around the brain, all of which are essential for the retrieval of stored information.


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This was the same conclusion the good people at MythBusters reached a few years ago, with the “Brain Drain” portion of their “Tablecloth Chaos” episode.

Among other things, the crew found out that about 15% of the brain was active even while a person sleeps. That number jumped to 30% when one of the hosts attempted to tell a story that involved as many different parts of his brain as possible.

If you need a short answer to the 10% question, think of it this way: Have you ever heard of someone suffering a traumatic head injury, but coming away just fine, because the injury only affected the 90% of the brain that we don’t use?

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(Photo credits: Do humans really only use ten percent of their brains via WENN)