Why Is The “Using 10 Percent Of Your Brain” Myth So Pervasive?

In the film Lucy, Scarlett Johansson awakes groggily, looking around the room, wondering where she is. Her voice plays over a rapid-fire montage: “What happened? What did you do to my stomach? What’s going on?” Cut to Morgan Freeman, giving a neuroscience lecture. “It is estimated most human beings normally use 10 percent of their brain’s capacity. Imagine if we could access 100 percent. Interesting things begin to happen.”

Johansson investigates his research and contacts him. She reveals, “I have access to 28 percent of my cerebral capacity. I can feel every living thing.” She can make twenty people collapse simply by raising her hand. She can learn the Chinese alphabet in an hour. Freeman warily expresses his concerns that her brain functioning may reach 100 percent. “With all of this knowledge, we can unlock secrets that go beyond our universe. I’m not even sure if mankind is ready for it.”

This movie is one of many to reference a figure you’ve probably heard time and time again, “We only use 10 percent of our brain. What could accomplish if we could access the other 90 percent?” Of course, neuroscience proves that this number is entirely erroneous.

For starters, consider this claim from an evolutionary standpoint. As Dr. Barry Beyerstein explains in Scientific American, “Brain tissue is metabolically expensive both to grow and to run, and it strains credulity to think that evolution would have permitted squandering of resources on a scale necessary to build and maintain such a massively underutilized organ.” Additionally, the human brain is only a small part of your body weight, and yet it requires a disproportionately high amount of your body’s energy — about 20 percent. Why would the brain require so much glucose and oxygen if only a negligible fraction of it was active?

Further proof that invalidates this “10 percent” myth is illustrated in cases of brain damage. As Beyerstein states, “Observing the effects of head injury reveals that there does not seem to be any area of the brain that can be destroyed by strokes, head trauma, or other manner, without leaving the patient with some kind of functional deficit.”

In reality, 100 percent of the brain is nearly always active. Indeed, “Even when you think you are doing nothing your brain is doing rather a lot — whether it’s controlling functions like breathing and heart rate, or recalling the items on your to-do list,” as Claudia Hammond explains for the BBC. Furthermore, when a neuron stops firing for a period of time, its synaptic connectivity ceases — when it comes to the brain, you must “use it or lose it.”

So why is this myth so pervasive?

Part of it has to do with the fact that it is commonly misattributed to both Albert Einstein and to William James, who wrote, “We are making use of only a small part of our possible mental and physical resources.” For whatever reason, people have used James’ ideas about potential to suggest that our brain is at fault for our shortcomings. The fallacious notion that our brain is using only a small portion of its capacity is an attractive scapegoat — it’s so hard for me to learn Spanish and get my office organized because 90 percent of my brain is just sitting there, doing nothing. This idea is “exploited by those who want to sell us hope of greater success by tapping into hidden reserves of mental energy either through brain enhancing programs or supernatural powers,” as Dr. Bruce Hood states in Psychology Today.

Furthermore, limitations in early brain studies were probably misinterpreted by those without a scientific background. With rudimentary tools to study the brain, scientists could only figure out what 10 percent of the brain was responsible for. The other 90 percent was referred to as the “silent cortex.” Many took this to mean that “silent” equated with “dormant.” Now, however, we refer to this as the “association cortex” an area of your brain that is involved with language, abstract thinking, and many other things.

Unfortunately, it looks like this urban legend is here to stay. While it’s fine to enjoy movies like Lucy for their entertainment value, keep in mind when you hear Morgan Freeman’s voice echoing, “Imagine if we could access 100 percent” — remember to thank your neurons that you already do.

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1 Comment

  1. Simplistic pseudoscience reigns easily in a society where over 40% of adults surveyed do not believe in evolution, another 15% are “unsure” about it, & belief in democracy means that their ignorance is equal to my knowledge. Our schools fail miserably, & those in power are indifferent.

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