Is it true we only use 10% of our brains?
Maybe… but not the way you think!
A few weeks ago, I was re-watching Limitless — and by the way, did you know there was a recent television series based on the movie, following the same premise? (It lasted one season.) That aside, I was struck once again by the idea that humans only use 10% of their brains — a concept that is at the core of Limitless as well as other recent films such as Lucy. The enticing corollary is that if only we could tap into the other 90%, we could… well, it seems we could be very good-looking, multi-tasking geniuses with superhero fighting skills, like Bradley Cooper and Scarlett Johansson in the aforementioned films.
Of course, we know better than to get our scientific facts from science fiction. But the idea of the untapped potential of our brains is much older than these films, and it has obvious appeal. In fact, a poll conducted in 2013 on behalf of the Michael J. Fox Foundation found that 65% of Americans believe the idea that we only use 10% of our brains. [1]
I know what you’re thinking… “Hey, I know some people who only use 10% of their brains!” But jokes aside, what does that statement even mean?
Perhaps the image that comes to mind is of a mass of brain tissue sitting dormant throughout most of a person’s life, while only a small part of the brain does all the work.
This is definitely not true. We realize that all of our brain tissue serves a purpose when any part of it becomes injured. As the saying goes, “you don’t know what you have until it’s gone.” Even under controlled conditions, such as when a brain biopsy is performed to diagnose a brain tumor, the loss of a small amount of brain tissue can lead to the (usually temporary) loss of some functions. And of course, with larger brain injuries, such as due to trauma or stroke, impairments are typically obvious and in fact, can serve as clues to the specific brain regions involved.
If you picture the brain as a gray mass of dormant tissue, think again. The human brain needs a lot of energy and oxygen to keep it running, and because of that, it is a very “expensive” organ to carry around: it receives about 15% of the blood pumped by the heart and uses up as much as half of the body’s glucose [2]. About a third of this energy is necessary just to keep the brain in working order, not even to do any “thinking” [3].
Considering this, if the brain were really a bunch of ballast, most of which we never used, wouldn’t evolution have downsized this draining organ long ago? Imagine our prehistoric ancestors roaming the Earth, carrying around their huge useless brains. Now imagine a mutant human who was born with a tiny brain, only 10% of the size of ours.
Why, with all the time and effort saved from having to hunt dangerous wild animals to nourish a large brain, he or she could have accomplished great things! At the very least, he would have had a much higher chance of surviving and passing on his genes to his kids, the next generation of tiny-brained humans. Before long, the Earth would have been populated with tiny-brained people instead of us!
In fact, of course, our large and complex brain has been our evolutionary trump card. Indeed, we as a species go to great lengths to nurture the brain development of the next generation. When human babies are born, their parents keep them safe and cater to all their physical needs while their brains continue developing at a rapid rate. [4] A human baby can’t even support her head on her shoulders for several months. Compare this to a horse, who can walk shortly after birth, or a dolphin, who is born able to swim and must face the realities of the adult world much sooner than its human counterpart.
Okay, so all that tissue up there in our heads is definitely not useless filler. But maybe another way to think of it is that we don’t use 100% of our brain 100% of the time. At any given moment, only some of the neurons (the cells that do most of the glamorous work in the brain) are “active” — maybe something like 15% [5], although this is notoriously difficult to measure. So there may be some truth to the idea that we only use 10% of our brain cells at the same time.
So what would happen if we did activate 100% of our neurons at the same time? Well, this is not really something we can test, but our best guess is that it would look like… a seizure.
Why? Consider that many of our neurons are responsible for controlling opposite activities: for example, some neurons help you start walking, and others allow you to stop; some neurons speed up your heart while others slow it down, and so on. If these were all active at the same time, you would be locked in a state of limbo, unable to accomplish anything, perhaps not even to breathe!
Fortunately, we can’t actually do this to ourselves: many of the neurons in the brain are inhibitory, which means their job is to stop other neurons from being active. They would act as a circuit-breaker and help us avoid “crashing” our brains.
So, the take-home message is: yes, we DO use 100% of our brains. We DON’T use 100% of our brain cells at the same time, and really, it’s for the best!
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Sources
[1] Weller, C. (2013, Sept. 25). Most Americans still believe they use only 10% of their brain, plus 4 other brain myths. Retrieved from http://www.medicaldaily.com/most-americans-still-believe-they-use-only-10-their-brain-plus-4-other-brain-myths-258046
[2] Silverthorn, D. (2010). Human physiology: An integrated approach. New York, NY: Pearson.
[3] Du, F. et al. (2008). Tightly coupled brain activity and cerebral ATP metabolic rate. Proceedings of the National Academy of Sciences 105(17): 6409–6414.
[4] Zeni, J. (2009, July 29). The slow-developing humans — rationale for a species of newborn motor morons. Retrieved from http://brainblogger.com/2009/07/29/the-slow-developing-human-rationale-for-a-species-of-newborn-motor-morons/
[5] Atwell, D., and Laughlin, S.B. (2001). An energy budget for signaling in the grey matter of the brain. Journal of Cerebral Blood Flow and Metabolism 21(10): 1133–45.
