The plot for the science fiction action thriller Lucy revolves on the myth we only use 10 percent of our brains. Myth. Directed by Luc Besson and starring actress Scarlett Johansson as the eponymous heroine with co-star Morgan Freeman playing the scientist trying to help her, the film depicts a young woman who involuntarily ingests an experimental drug that increases her ability to tap her brain's other 90 percent. Her basic skills are enhanced, her perception is sharpened, her abilities to analyze and learn speed up, and she gains paranormal abilities that include telekinesis, telepathy, and a form of mental time travel. As she reaches 90 percent brain usage, other characters wonder what will happen when she hits 100 percent.
Why do so many people think our brain usage is 10 percent? We do not know for certain where this arbitrary percentage originated, although we do know it has no basis in science. As early as the 1890s, William James asserted - reasonably enough and without specifying any amount - that we only utilize a fraction of our intellectual potential. By the time an ad in the 1929 World Almanac claimed, "Scientists and psychologists tell us we use about TEN PERCENT of our brain power" (cited in Beyerstein, 1999, p. 11), the number had crept in. Different sources will make different claims about where that number comes from, but they are guessing. We really do not know.
In point of fact, the brain uses more energy than any other organ in the human body, so it stays busy. "We use virtually every part of the brain, and [most of] the brain is active almost all the time," says Johns Hopkins School of Medicine neurologist Barry Gordon. "The brain represents three percent of the body's weight and uses 20 percent of the body's energy."
"It's impossible to work out how much of our brain we are using quantitatively. However, it is definitely much more than 10 percent," says Barbara Sahakian said, University of Cambridge professor of clinical neuropsychology. Others, like Dr. Eric Chudler, assert flatly that we already use our brains in their entirety. How well we make use of them, well, that's another story.
In the Discovery Channel series MythBusters, their build team (Grant Imahara, Kari Byron, and Tory Belleci) took a crack at this one in episode 151, "Tablecloth Class," and deemed it busted. Beyerstein (1999) and many other professionals make key points when refuting the myth, including but not limited to these:
Lucy is not the first film to perpetuate this nonsense, not by any means, nor will she be the last.
Beyerstein, B. L. (1999). Whence cometh the myth that we only use 10% of our brains? In S. Della Sala (Ed.), Mind-Myths: Exploring Popular Assumptions about the Mind and Brain (pp. 3-24). Chichester: John Wiley and Sons.