Scarlett Johansson uses all of her brain - and so do you

JORDAN GAINES LEWIS
Last updated 13:35 24/07/2014
Scarlett Johansson

HANG ON, I'M THINKING: Scarlett Johansson kicks the brain gears into action and starts using all of her grey matter in the film Lucy.

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It's a common conversation starter to assert that we only use 10 per cent of our brains.

In Lucy, the soon-to-be-released thriller about a woman forced to work as a drug mule for the Taiwanese mob, Professor Norman lectures, "It is estimated most human beings only use 10 per cent of their brain's capacity. Imagine if we could access 100 per cent. Interesting things begin to happen."

Now, I know Morgan Freeman is well versed in playing the wise sage, and I know that I haven't earned my PhD yet - but professor, I beg to differ.

You see, we all access 100 per cent of our brains every day. And we don't have to be telekinetic or memorise an entire deck of cards to do it.

In the film, the drugs implanted into Lucy - played by Scarlett Johansson - leak into her system, allowing her to "access 100 per cent" of her brain.

Among other things, Lucy can move objects with her mind, choose not to feel pain and memorise copious amounts of information.

In a way, the idea that we only use 10 per cent of our brains is rather inspiring. It may motivate us to try harder or to tap into some mysterious, intact reservoir of creativity and potential. There are even products that promise to unlock that other 90 per cent.
 
As ludicrous as the claim is, however, two-thirds of the public and, get this, half of science teachers reportedly still believe the myth to be true.

The notion is so widespread that when University College London neuroscientist Sophie Scott attended a first aid course, her instructor assured the class that head injuries weren't dangerous because "90 per cent of the brain [doesn't] do anything."

How did this misconception come about?

We may be able to track its roots back to psychologist William James, who wrote in his 1907 text The Energies of Men that "we are making use of only a small part of our possible mental and physical resources.

" I tend to agree with this sentiment when I spend my evenings on the couch watching reality television, but James didn't intend to lend credence to this 10 per cent myth.

Someone else did. Lowell Thomas, in his foreword to Dale Carnegie's 1936 book How to Win Friends and Influence People, reinterpreted the statement and, it seems, sprinkled in a few of his own ideas.

"Professor William James of Harvard used to say that the average person develops only 10 per cent of his latent mental ability," Thomas wrote.

Here's the thing: The brain has rapidly tripled its original size across 2 million years of human evolution. Despite only accounting for 2 per cent of our body weight, the brain gobbles up a whopping 20 per cent of our daily energy intake.

Our brains are also remarkably efficient, having evolved gyri (ridges), which have dramatically increased our cortical-surface-area-to-total-volume ratio relative to other species.

The "we only use 10 per cent of our brains" claim would mean that we're effectively evolving in the opposite direction - and that we're doing this very quickly.

Another obvious way we know that we're using more than 10 per cent of our brain at any one time is through approaches like functional magnetic resonance imaging and positron emission tomography.

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PET and fMRI are imaging techniques that reveal areas of relatively high brain activity in real time.

Imaging studies tell us that not only are many brain areas recruited when performing even the simplest of tasks, like watching a movie, but that the activity between these areas is extremely dynamic.

But the "10 per cent myth" may have been perpetuated by one 10 per cent figure that is true.

Despite the brain having nearly 100 billion neurons, this cell type is vastly outnumbered by another: glial cells. Glial ("glue") cells are responsible for maintaining homeostasis (keeping everything ticking well), providing structural support, insulating neurons with an insulating substance called myelin, and removing pathogens and debris.

The actual ratio of glial cells to neurons is disputed, although many texts claim that it may be roughly 10:1. In other words, neurons are only 10 per cent of our entire brain.

Think about yourself right now.

Are you engaging your muscles to sit yourself upright? Using your hand to scroll your computer mouse (or thumb on your mobile device)? Perhaps you're eating something? Listening to music? Breathing?

Then rest assured, you're using more than 10 per cent of your brain right now.

* Jordan Gaines Lewis is a neuroscience doctoral candidate at Penn State College of Medicine.

- Washington Post

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