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We use only 10% of our brains? It’s a myth

© 2014 - Universal Pictures
Scarlett Johansson in a scene from the 2014 motion picture "Lucy."

I’ve written here before about how scientists have thoroughly debunked that old pop-psychology assertion that individual differences in cognitive (thinking) style are because people are either “right-brained” (creative) or “left-brained”(analytical).

For example, a 2013 study, in which the brain scans of more than 1,000 participants were carefully analyzed, found absolutely no evidence that individuals demonstrate a preference for one hemisphere over another.

Another popular — and stubbornly persistent — brain-related myth is the idea that humans use only about 10 percent of their brain’s capacity.

That myth receives a good takedown in an essay published online last week in the Atlantic magazine by Sam McDougle, a doctoral candidate in psychology and neuroscience at Princeton University.

As McDougle points out, the 10 percent figure is “100 percent bogus.” In fact, it never had a scientific basis, but was likely “plucked out of the sky,” he says, by the American broadcast-journalist Lowell Thomas, who included it in his preface to Dale Carnegie‘s best-selling 1936 self-help book, “How to Win Friends and Influence People.”

Yet, almost 80 years later, the myth persists. Just last year, a survey conducted for the Michael J. Fox Foundation found that 65 percent of Americans believe it to be true.

And it’s likely to become even more ingrained into popular thinking this year, thanks to the premise of the new sci-fi thriller “Lucy.” In the trailer for that film, Morgan Freeman, playing a professor of neuroscience, is featured (rather ominously) making this statement: “It is estimated most human beings only use 10 percent of the brain’s capacity. Imagine if we could access 100 percent. Interesting things begin to happen.”

Well, if the trailer is any guide, very interesting things begin to happen to Scarlet Johansson.

What the science shows

Go ahead and enjoy the movie, but don’t believe that 10 percent claim. For it’s wrong on many levels, as McDougle explains:

First, the entire brain is active all the time. The brain is an organ. Its living neurons, and the cells that support them, are always doing something. (Where’s the “you only use 10 percent of your spleen” myth?) Joe LeDoux, a professor of neuroscience and psychology at [New York University], thinks that people today may be thrown off by the “blobs” — the dispersed markers of high brain activity — seen in functional magnetic resonance imaging (fMRI) of the human brain. These blobs are often what people are talking about when they refer to the brain “lighting up.”

Say you’re watching a movie in an fMRI scanner. Certain areas of your brain — the auditory and visual cortices, for instance — will be significantly more active than others; and that activity will show up as colored splotches when the fMRI images are later analyzed. These blobs of significant activity usually cover small portions of the brain image, often less than 10 percent, which could make it seem, to the casual observer, that the rest of the brain is idling.

But, as LeDoux put it to me in an email, “the brain could be one hundred percent active during a task with only a small percentage of brain activity unique to the task.” This kind of imaging highlights big differences in regional brain activity, not everything the brain is doing.

And that’s why the 10-percent myth, compared with other fantasies, is especially pernicious.

In fact, the entire premise of only “using” a certain proportion of your brain is misguided. When your brain works on a problem — turning light that hits your retina into an image, or preparing to reach for a pint of beer, or solving an algebra problem — its effectiveness is as much a question of “where” and “when” as it is of “how much.”

Certain regions of the brain are more specialized than others to deal with certain tasks, and most behavior depends on tight temporal coordination between those regions. Your visual system helps you locate that pint of beer, and your motor system gets your hand around it.

The idea that swaths of the brain are stagnant pudding while one section does all the work is silly. The brain is a complex, constantly multi-tasking network of tissue.

If only it were so

Of course, it’s understandable why the 10-percent falsehood appeals to us.

“If we only use 10 percent of our brains, imagine how totally great life would be if we could use more,” writes McDougle. “You could dazzle Grandma and her nursing-home crew during ‘Jeopardy.’ Or, like Lucy, you could learn Chinese calligraphy in an hour. The 10-percent myth presses the same buttons as any self-help scheme that promises to make us better, faster.”

“And that’s why the 10-percent myth, compared with other fantasies, is especially pernicious,” he adds. “It has a distinct air of scientific plausibility — it’s a zippy one-liner with a nice round number, a virus with obvious vectors in pop-psychology books, easy to repeat at cocktail parties. The myth is also part of a larger way of thinking about the brain that is characterized by misleading simplifications — like the notion that the right side of the brain is creative and the left side rational. ‘Those kinds of ideas self-perpetuate,’ LeDoux told me. ‘It’s like saying dopamine is responsible for pleasure and the amygdala makes fear. Both are wrong.’

You can read McDougle’s essay on the Atlantic website.

Comments (4)

  1. Submitted by Paul Udstrand on 07/21/2014 - 12:37 pm.


    It surprised me to see that very long ago debunked myth pop up as a movie scenario in the year 2014. I mean, has everyone seen a PET scan by now? The whole brain lights up one way or another unless there’s actual damage.

  2. Submitted by Paul Brandon on 07/21/2014 - 02:44 pm.

    A minor quibble

    The Morgan Freeman quote is:
    “It is estimated most human beings only use 10 percent of the brain’s capacity. ……”

    Note the use of the term ‘capacity’.
    That turns it from a structural statement to a functional one. We are unquestionably using our whole brains in the sense that all of the neurons are continuously active. However, we might be accomplishing a small fraction of what we could do if the same quantity of neural activity were better organized.

    I doubt that anyone writing movie scripts analyzed anything at this level of precision (they were using their brains’ capacities for other purposes).

  3. Submitted by David Markle on 07/21/2014 - 04:57 pm.

    Not use only 10%, but what is “use” and what is 10%?

    I don’t doubt that we use most of the regions of the brain at any given time, but that’s like saying there are outdoor neon lights lit in every county of the USA at night. At the level of how many individual land parcels have neon lights, then you’re getting closer to a meaningful percentage analogy. And then there’s the matter of conscious use, as opposed to unconscious, preconscious, subsconscious, autonomic, etc.: how do you calculate that, in terms of percentage? Finally, I think Harry Stack Sullivan pointed out that none of us achieves but a fraction of our capabilities!

  4. Submitted by Nathanael Ries on 07/21/2014 - 06:29 pm.

    Why can’t they at least avoid using debunked claims?

    There are so many other pseudo-scientific themes they could have gone with that, as crazy as they sound, would still make more sense than the one they ran with… Genetic mutation, biotech, alien symbiote, etc…

    At least those haven’t been outright debunked like the 10% brain usage claim they based the whole movie off of. I’ll be categorizing this film under the same class as “Sharknado”.

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