The Limits of the Human Brain

FROM THE LECTURE SERIES: Understanding the Misconceptions of Science

By Don Lincoln, Ph.D., Fermi National Accelerator Laboratory (Fermilab)

Nobody knows why the myth that people use only 10% of their brain is so pervasive, but it is. And, it is not true. But even if the 10% brain myth were to be true, using 10 times more of one’s brain would not give any supernatural powers to anyone.

A 3D illustration of a half-skeleton, half-man with a transcendental brain.
The human brain has fascinated many people. It is this fascination which has made the 10% brain myth very popular. (Image: Vitstudio/Shutterstock)

The Misapprehensions about the Brain

The human brain is one of the most amazing objects to have developed in the history of the Earth. There is no question that things like the Earth, the Sun, the Moon, and the stars have their allure, but they are just things. They have no sense of self.

The brain is the seat of the mind and the home of the soul. It makes a person who they are. It holds their memories and it forms their desires. It gets them into trouble, too.

Because of this, scientists and even non-scientists have spent a great deal of time thinking about the human brain. And that is actually a problem. There are a tremendous number of articles written on the subject. Online, there are articles linking the brain with digestion, with sleep, with drug use, with concussions, and with so many more things.

And it does not help at all that the press simply loves these kinds of articles. It will publish just about anything about the mind that is found in even quasi-scientific literature, no matter if the result has been replicated or even is viewed charitably by the scientific community. It is no wonder that the general public has so many misunderstandings about the brain. They are just everywhere. And now to consider one of the commonly believed canards that is often encountered.

This is a transcript from the video series Understanding the Misconceptions of Science. Watch it now, Wondrium.

The 10% Brain Utilization Myth

Nobody knows why the myth that people use only 10% of their brain is so pervasive, but it is. It is not true, though. In fact, it is ridiculous, when it is thought about. It leads to such cinematographic marvels as the 2014 movie Lucy. In Lucy, the title character is accidentally dosed with a large quantity of a fictional drug. She gains telepathy, telekinesis, and mental time travel. She no longer feels pain.

Image of a brain in grey with a 10% wedge of color.
If 90% of the brain was not used, then there would be a huge evolutionary pressure to reduce the size of brains. (Image: Shannan Muskopf; Derivative work MagentaGreen/CC BY-SA 3.0/Public domain)

Over the course of the movie, she gains more and more capabilities until she eventually becomes god-like with the ability to move through time, and she goes back and interacts with a different Lucy, the real one discovered in Africa and also called Lucy. She then goes back and witnesses the Big Bang. It is all an entertaining and ridiculously unlikely plot. It is ridiculous because, well, it just is. But even if the myth were true, using 10 times more of one’s brain wouldn’t give anyone those kinds of powers.

Learn more about getting smarter about intelligence.

The Origin of the 10% Brain Utilization Myth

So, how did this myth get started? Actually, it is not really known. But it has been around a long time. It has been a staple of the self-help community for nearly a century. In the 1929 World Almanac, there is an advertisement that says, “There is no limit to what the human brain can accomplish. Scientists and psychologists tell us we use only about 10 percent of our brain power.”

And some years later, the myth perhaps had an even bigger stage when, in 1936, American writer Lowell Thomas wrote a foreword to Dale Carnegie’s hugely popular book, How to Win Friends and Influence People. In it, he wrote, “Professor William James of Harvard used to say that the average man develops only 10 percent of his latent mental ability.”

Digging a little deeper, it turns out that William James was indeed a professor of psychology at Harvard back in the 1890s. He and his collaborator Boris Sidis studied Sidis’s own son, a boy by the name of William Sidis. William Sidis was a child prodigy and extremely precocious, with exceptional mathematical and linguistic talents.

William James was known to say in public lectures that he realized later in life that people meet only a fraction of their full mental potential. It is a short jump from that statement to the oddly-specific statement that only 10% is used. However, no matter the popularity of the myth, it is incorrect. How is this known?

Learn more about how statistics can lie to you.

Checking the Veracity of the 10% Brain Utilization Myth

Well, the simplest response is a bit morbid. If there were a distinct 10% of the brain used and someone experienced a serious, but not fatal, brain injury, well then there would only be a 10% chance that they would experience some sort of bad outcome. Basically, 9 out of 10 brain injuries would have no impact on a person’s life. But that is not true. Even modest damage anywhere in the brain has a negative consequence.

Now that, of course, assumes that there are distinct parts of the brain that are used. Maybe only 10% of the brain is used, but that 10% is spread all through the skull. After all, it is known that the neurons in the brain are a complex mesh, interlocking with one another. However, scientists have actually embedded micro-electrodes in patient’s brains and can see that it is not just that 10% of the neurons are firing.

There are many other reasons why this myth is known not to be true, but a big one comes from human evolution. The brain takes a lot of energy to run. It takes about 20% of the energy consumed by human metabolism, in spite of being only about 2% of the body’s mass. If 90% of the brain were not used, there would be a huge evolutionary pressure to reduce the size of brains and skulls.

An infant’s large skull is a huge danger during childbirth, especially in the days before modern medicine. It was not at all uncommon for women to die in childbirth simply because the baby’s head was too big to fit through the pelvic opening. Evolution is known to not have an intent, but any adaptation that will increase the chances that a baby will survive will be selected.

The bottom line is that the idea that humans use only 10% of their brain just is not true.

Common Questions about the Limits of the Human Brain

Q: What percentage of the brain is used?

As per a survey from 2013, most Americans believe that they only use 10 % of their brains. But most cognitive neuroscientists agree on this being a myth.

Q: Can 100 % of the brain be used?

Yes, according to most psychologists and cognitive neuroscientists, every part of the brain is used.

Q: How many brain cells do humans have?

It is believed that an average human brain has around a hundred billion brain cells.

Q: What is the memory capacity of the human brain?

It is believed that an average adult human brain can store the equivalent of 2.5 million gigabytes of digital memory.

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