Ten percent of the brain myth

The 10 percent of the brain myth asserts that humans generally use only 10 percent (or some other small percentage) of their brains. It has been misattributed to many celebrated people, notably Albert Einstein. By extrapolation, it is suggested that a person may harness this unused potential and increase intelligence.
Changes in grey and white matter following new experiences and learning have been shown, but it has not yet been proven what the changes are. The popular notion that large parts of the brain remain unused, and could subsequently be "activated", rests in folklore and not science. Though specific mechanisms regarding brain function remain to be fully described—e.g. memory, consciousness—the physiology of brain mapping suggests that all areas of the brain have a function and that they are used nearly all the time.
Origin.
A likely origin for the "ten percent myth" is the reserve energy theories of Harvard psychologists William James and Boris Sidis who, in the 1890s, tested the theory in the accelerated raising of child prodigy William Sidis. Thereafter, James told lecture audiences that people only meet a fraction of their full mental potential, which is considered a plausible claim. The concept gained currency by circulating within the self-help movement of the 1920s; for example, the book "Mind Myths: Exploring Popular Assumptions About the Mind and Brain" includes a chapter on the ten percent myth that shows a self-help advertisement from the 1929 "World Almanac" with the line "There is NO LIMIT to what the human brain can accomplish. Scientists and psychologists tell us we use only about TEN PERCENT of our brain power." This became a particular "pet idea" of science fiction writer and editor John W. Campbell, who wrote in a 1932 short story that "no man in all history ever used even half of the thinking part of his brain". In 1936, American writer and broadcaster Lowell Thomas popularized the idea—in a foreword to Dale Carnegie's "How to Win Friends and Influence People"—by including the falsely precise percentage: "Professor William James of Harvard used to say that the average man develops only ten percent of his latent mental ability". 
In the 1970s, the Bulgarian-born psychologist and educator, Georgi Lozanov proposed the teaching method of suggestopedia believing "that we might be using only five to ten percent of our mental capacity". The origin of the myth has also been attributed to Wilder Penfield, the U.S.-born neurosurgeon who was the first director of Montreal Neurological Institute of McGill University.
According to a related origin story, the ten percent myth most likely arose from a misunderstanding (or misrepresentation) of neurological research in the late 19th century or early 20th century. For example, the functions of many brain regions (especially in the cerebral cortex) are complex enough that the effects of damage are subtle, leading early neurologists to wonder what these regions did. The brain was also discovered to consist mostly of glial cells, which seemed to have very minor functions. James W. Kalat, author of the textbook "Biological Psychology", points out that neuroscientists in the 1930s knew about the large number of "local" neurons in the brain. The misunderstanding of the function of local neurons may have led to the ten percent myth. The myth might have been propagated simply by a truncation of the idea that some use a small percentage of their brains at any given time. In the same article in "Scientific American", John Henley, a neurologist at the Mayo Clinic in Rochester, Minnesota states: "Evidence would show over a day you use 100 percent of the brain".
Although parts of the brain have broadly understood functions, many mysteries remain about how brain cells (i.e., neurons and glia) work together to produce complex behaviors and disorders. Perhaps the broadest, most mysterious question is how diverse regions of the brain collaborate to form conscious experiences. So far, there is no evidence that there is one site for consciousness, which leads experts to believe that it is truly a collective neural effort. Therefore, as with James's idea that humans have untapped cognitive potential, it may be that a large number of questions about the brain have not been fully answered.
Analysis.
Neurologist Barry Gordon describes the myth as false, adding, "we use virtually every part of the brain, and that (most of) the brain is active almost all the time." Neuroscientist Barry Beyerstein sets out six kinds of evidence refuting the ten percent myth:
In debunking the ten percent myth, "Knowing Neurons" editor Gabrielle-Ann Torre writes that using one hundred percent of one's brain would not be desirable either. Such unfettered activity would almost certainly trigger an epileptic seizure. Torre writes that, even at rest, a person likely uses as much of his or her brain as reasonably possible through the default mode network, a widespread brain network that is active and synchronized even in the absence of any cognitive task. Thus, "large portions of the brain are never truly dormant, as the 10% myth might otherwise suggest."
In popular culture.
Some proponents of the "ten percent of the brain" belief have long asserted that the "unused" ninety percent is capable of exhibiting psychic powers and can be trained to perform psychokinesis and extra-sensory perception. This concept is especially associated with the proposed field of "psionics" (psychic + electronics), a favorite project of the influential science fiction editor John W. Campbell, Jr in the 1950s and '60s. There is no scientifically verified body of evidence supporting the existence of such powers. Such beliefs remain widespread among New Age proponents to the present day.
In 1980, Roger Lewin published an article in "Science", "Is Your Brain Really Necessary?", about studies by John Lorber on cerebral cortex losses. He reports the case of a Sheffield University student who had a measured IQ of 126 and passed a Mathematics Degree but who had hardly any discernible brain matter at all since his cortex was extremely reduced by hydrocephalus. The article led to the broadcast of a Yorkshire Television documentary of the same title, though it was about a different patient who had normal brain mass distributed in an unusual way in a very large skull. Explanations were proposed for the first student's situation, with reviewers noting that Lorber's scans evidenced that the subject's brain mass was not absent, but compacted into the small space available, possibly compressed to a greater density than regular brain tissue.
Several books, films, and short stories have been written closely related to this myth. They include the 1986 film "Flight of the Navigator"; the novel "The Dark Fields" and its 2011 film adaptation, "Limitless" (claiming 20 percent rather than the typical 10 percent); the 1991 film "Defending Your Life"; the ninth book ("White Night") of Jim Butcher's book series "The Dresden Files"; the shōnen manga "Psyren"; and the 2014 film "Lucy"—all of which operate under the notion that the rest of the brain could be accessed through use of a drug. "Lucy" in particular depicts a character who gains increasingly godlike abilities once she surpasses 10 percent, though the film suggests that 10 percent represents brain capacity at a particular time rather than permanent usage.
The myth was examined on a 27 October 2010 episode of "MythBusters". The hosts used magnetoencephalography and functional magnetic resonance imaging to scan the brain of someone attempting a complicated mental task, and found that over 10%, as much as 35%, was used during the course of their test.
The ten percent brain myth occurs frequently in advertisements, and in entertainment media it is often cited as fact.
In the season 2 episode of "Fetch! With Ruff Ruffman", "Ruff's Case of Blues in the Brain", they debunked the theory.
In "Teen Titans Go!", Beast Boy attempts to solve a Find-It puzzle by unlocking more percentage of brain.