In the new action thriller "Lucy" from writer and director Luc Besson, Scarlett Johansson plays a drug mule whose body is implanted with a substance that begins to seep into her bloodstream and affect her body — most importantly her brain.
Lucy develops the ability to use the "untapped" majority of her brain, which lies fallow in most people, the movie says. The authoritative, gravitas-laden voice of Morgan Freeman (as Professor Norman, a research psychologist) states in the film, "It is estimated most human beings use only 10 percent of their brain's capacity. Just imagine if we could access 100 percent. Interesting things begin to happen."
As the film goes on, and Lucy accesses more and more of her cerebral capacity, she gains superhuman abilities, such as speed reading, a photographic memory, encyclopedic knowledge, the capacity to learn a foreign language in an hour and psychic abilities such as telekinesis (moving objects with her mind). She sets out for revenge using her powers, and in the trailer when Professor Norman is asked, "What happens when she reaches 100 percent?" he replies, "I have no idea."
Actually, scientists have a pretty good idea of what happens when people use all of their brains — because most of us do: The 10 percent figure is a myth. [7 Medical Myths Even Doctors Believe]
"Lucy" isn't a documentary, of course, and it's hardly the first sci-fi thriller to get science wrong. But it may be the most recent high-profile example of the decades-old scientific myth, or urban legend. It's not just a throwaway scientific fact stated by a character who happens to be wrong (as in "Terminator 2," when Sarah Connor says. "There are 215 bones in the human body," when in fact there are 206). In Lucy, the myth is the entire premise of the film.
The fact is, people use all of their brains. Brain imaging research techniques such as PET (positron emission tomography) scans and fMRI (functional magnetic resonance imaging) clearly show that the vast majority of the brain does not lie unused. Although certain activities may use only a small part of the brain at a time (for example, watching reality TV shows), any sufficiently complex set of activities will use many parts of the brain.
In the book "50 Great Myths of Popular Psychology" (2010, Wiley), Dr. Scott Lilienfeld explains, "The last century has witnessed the advent of increasingly sophisticated technologies for snooping in the brain's traffic. ... Despite this detailed mapping, no quiet areas awaiting new assignments have emerged. In fact, even simple tasks generally require contributions of processing areas spread throughout virtually the whole brain."
An incredibly powerful and flexible organ, the brain can learn new languages and complex skills well into adulthood. It's tricky to say what the brain's capacity actually is, though, and the answer depends on what particular ability you're talking about. Most people can memorize only a handful of random digits using their short-term memories, though practice (and techniques such as a "memory palace," which aids recall using visualization) can significantly increase their recall.
It's not that most people have a well-defined physical or psychological limit on memory, or that people with superior memory abilities use more of their brain capacity, though. Instead, most people just don't find memorizing long strings of random numbers that important or interesting. It's all about where you put your time and (mental) resources.
So where did this 10 percent myth come from? Psychologist Barry Beyerstein of Simon Fraser University researched the urban legend for a chapter in the book "Mind Myths: Exploring Everyday Mysteries of the Mind and Brain" (Wiley, 1999), and traced the tall tale back to at least the early part of the 20th century.
In some cases people misunderstood or misinterpreted legitimate scientific findings, but the myth was really popularized by the self-help movement. Self-improvement writers such as Dale Carnegie, author of the classic book "How to Win Friends and Influence People" (first published in 1936, by Simon & Schuster) and groups such as those promoting transcendental meditation and neurolinguistic programming referenced the myth. They promised to teach people methods of getting ahead in life by tapping latent brainpower.
As cool as it would be to have superpowers like Lucy, you're not going to get them by using more of your brain. You're already using all you've got — for better or worse.
Benjamin Radford, M.Ed, is deputy editor of the Skeptical Inquirer science magazine and author of seven books, including "Hoaxes, Myths, and Manias: Why We Need Critical Thinking" (Prometheus Books, 2003). His website is www.BenjaminRadford.com.