"Lucy" is Wrong; We Use Way More Than 10% of Our Brains

"It is estimated most human beings only use ten percent of their brain's capacity," lectures Professor Norman, played by actor Morgan Freeman, in the trailer for the new thriller Lucy. "Imagine if we could access 100 percent. Interesting things begin to happen."

I know I haven't earned my Ph.D. yet, Professor, but I beg to differ. You see, we all access 100% of our brains every day. And we don't have to be telekinetic or memorize an entire deck of cards to do it.

In the film, which opens next Friday, Scarlett Johansson's character Lucy is forced to work as a drug smuggler in a Taiwanese mob. The drug they've implanted into her body leaks into her system, allowing her to "access 100%" of her brain. Among other things, Lucy can move objects with her mind, choose not to feel pain, and memorize copious amounts of information.

In a way, the idea that we only use 10% of our brains is rather inspiring. It may motivate us to try harder or tap into some mysterious, intact reservoir of creativity and potential. There are even products that promise to unlock that other 90%.

As ludicrous as the claim is, however, 2/3 of the public and half of science teachers 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% of the brain [doesn't] do anything."

How did this misconception come about, anyway? We may be able to track its earliest 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, of course, James didn't intend to lend credence to this "10% myth."

But 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, sprinkld in a few of his own ideas. "Professor William James of Harvard," Thomas wrote, used to say that the average person develops only 10 percent of his latent mental ability."

Here's the thing: the brain has rapidly tripled its original size across two million years of human evolution. Despite only accounting for 2% of our body weight, the brain gobbles up a whopping 20% of our daily energy intake. Our brains are also remarkably efficient, having evolved gyri which have dramatically increased our cortical surface-area-to-total volume ratio relative to other species. The "we only use 10% 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% of our brain at once is through approaches like functional magnetic resonance imaging and positron emission tomography. fMRI and PET 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.

Plus, the "use it or lose it" adage seems to hold particularly true in brain health. A 2012 study by Schafer and colleagues at Harvard found that neural immune cells called microglia can remove idle, but otherwise healthy, synapses (connections) between brain cells. If we were only regularly using only 10% of our brains at any given time, we might all be prone to cerebral atrophy, resembling patients with neurodegenerative diseases like Alzheimer's.

The "10% myth" may have been perpetuated by something 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, providing structural support, insulating neurons with 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% 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? Rest assured, you're using more than 10% of your brain right now.

You may have played God in a movie, Morgan Freeman, but clearly you need a primer on how your most incredible creation-the brain-functions!

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Originally published at The Conversation UK.

Image credit: Fandango (Lucy), Lifehacker (brain), NIMH/Wikimedia Commons (fMRI), Beyond the Dish (glial cells)