How Much Of Our Brain Do We Use?

By Temma Ehrenfeld @temmaehrenfeld
March 28, 2019

How much of our brain do we use? We use much more than 10 percent! In fact, much of your brain is active most of the time, even when you are sleeping.

Many Americans think we each use only 10 percent of our brains in the course of our lives.

The idea is that we could do much more, if we only knew how to tap more of our brain power. But the 10 percent estimate is way off.


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So how much of our brain do we use?

Most likely, all of it. "Evidence would show over a day you use 100 percent of the brain," John Henley, a neurologist at the Mayo Clinic in Rochester, Minn, told Scientific American.

With functional magnetic resonance imaging, a common technique, researchers have demonstrated that large chunks of our brains get involved even in simple tasks. In fact, all undamaged areas are active in some way continuously, even when you are sleeping. All that activity soaks up some 20 percent of your body's energy.

Over decades, researchers have mapped areas of the brain to different functions. We have neurons to process what we see, other neurons to process what we hear, another section for smell, and so on. No unneeded areas have been found. Even slight damage to small areas can have big effects — not what you’d expect if 90 percent of the brain wasn’t in use.

Autopsies of brains would show evidence of degeneration in the unused areas, just like we see degeneration in muscles we don’t use. But there are no signs of that in brains.

Finally, why would human beings have evolved to carry around such big brains — which make childbirth painful and use up so much energy — if we didn’t use them?

Where did the myth that we use only 10 percent of the brain come from?

You might remember playing a game as a child called the “Telephone effect.” One person would whisper a phrase in someone’s ear, who then whispered it to the next person. By the end of the chain, the message would be amusingly different.

That’s basically what happened to produce the 10 percent myth.

The early psychologist William James wrote in 1907 that "We are making use of only a small part of our possible mental and physical resources." But James didn’t specify a percentage.

The figure 10 percent cropped up in advertisements for self-help books in the 1920s.

In 1936, the forward to Dale Carnegie's enormously popular 1936 book “How To Win Friends and Influence People” stated incorrectly that, "Professor William James of Harvard used to say that the average man develops only ten percent of his latent mental ability."

Then books and movies developed the myth for decades.

What’s the real story? We repeat the idea that we only use 10 percent of our brains because it makes us feel smart, capable of more. But the idea that that you could accomplish more in your life doesn’t depend on an inactive brain. Maybe your brain is busy with dumb activities.

Take James’ message to heart. You can do more if you learn new skills and use your time well.


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March 28, 2019

Reviewed By:  

Janet O’Dell, RN