View source for Humans use only 10 percent of their brains

{{Claim
| name = Humans use only 10 percent of their brains
| status = False
| claim = People use only about 10 percent of their brains, leaving vast untapped mental capacity that could be unlocked through training, products or special techniques.
| domain = Education & Learning
| tactic1 = Pseudoscience / Junk Science
| era = Historical
| first_seen = 1930s
| origin = Self-help literature of the early twentieth century, including a misattributed claim in Lowell Thomas's 1936 preface to Dale Carnegie's ''How to Win Friends and Influence People''
| last_reviewed = 2026-10-27
}}
The claim that '''humans use only 10 percent of their brains''' is one of the most widespread myths about the mind. It appears in advertisements, self-help books and films such as ''Limitless'' (2011) and ''Lucy'' (2014), which imagine what people could achieve if they unlocked the remaining 90 percent. Surveys have found that a majority of people in some countries believe it. The claim is false. Brain imaging shows that all parts of the brain are active over the course of a day, damage to almost any area causes some loss of function, and the brain consumes so much energy that it would make no evolutionary sense to maintain a large, unused organ.

== The claim ==
The myth suggests that most of the brain lies dormant and that ordinary people could become dramatically smarter, more creative or even gain psychic powers by activating it. It is used to sell courses, supplements, "brain training" programs and psychic or paranormal claims.

== Origin ==
The myth's origins are uncertain, but several influences have been identified:

* '''William James.''' The American psychologist wrote in the early 1900s that people use only a small part of their possible mental resources. He was making a general point about human potential, not a measurement of brain tissue.
* '''Self-help literature.''' In his 1936 preface to Dale Carnegie's bestselling ''How to Win Friends and Influence People'', the broadcaster Lowell Thomas wrote that James had said the average person develops only 10 percent of their latent mental ability. James is not known to have given that figure.
* '''Early neuroscience.''' Researchers in the early twentieth century found that stimulating some areas of the brain produced no obvious movement or sensation, and called them "silent" cortex. These areas are now known to handle complex functions such as planning, language and integration.
* '''Misattribution.''' The claim is often falsely attributed to Albert Einstein.

== What the evidence shows ==
* '''Imaging.''' Functional MRI and PET scans show that different tasks activate different regions, and that over the course of a day virtually all of the brain is active. Even during sleep many regions are active.
* '''Damage.''' Strokes, injuries and diseases affecting almost any part of the brain cause some deficit. If 90 percent were unused, much brain damage would have no effect.
* '''Energy.''' The brain makes up about 2 percent of body weight but uses roughly 20 percent of the body's energy. Evolution would be unlikely to maintain such an expensive organ if most of it were idle.
* '''Use it or lose it.''' Neurons and connections that are not used tend to weaken or die; large, permanently unused regions would degenerate.
* '''Microstructure.''' Recordings of individual neurons show activity throughout the brain.

It is true that not all neurons fire at the same time; in fact, if they did, the result would be a seizure. The brain also has a remarkable capacity to learn and adapt, known as neuroplasticity. But that is very different from having unused capacity waiting to be switched on.

== Why it persists ==
The myth is appealing because it is optimistic: it suggests everyone has hidden potential that could be unlocked. It has been repeated by self-help writers, advertisers and films, and is often linked to products promising cognitive enhancement. Its vague, scientific-sounding number makes it memorable.

== Lessons for readers ==
* Be skeptical of precise-sounding statistics without a clear source.
* Check famous attributions; many quotations credited to Einstein or other notable figures are invented.
* Ask what evidence underlies claims about the brain, especially when they are used to sell products.
* Human potential can grow through learning and practice, but not by switching on dormant brain tissue.
* Films and fiction are not reliable sources of scientific information.

== See also ==
* [[Listening to Mozart makes babies smarter]]
* [[People learn better in their preferred learning style]]
* [[Phrenology reveals character from the shape of the skull]]
* ''[[Library:Calling Bullshit|Calling Bullshit]]'' (Bergstrom and West)

== Sources ==
* Barry L. Beyerstein, "Whence cometh the myth that we only use 10% of our brains?," in Sergio Della Sala, ed., ''Mind Myths: Exploring Popular Assumptions About the Mind and Brain'' (Wiley, 1999).
* Scott O. Lilienfeld, Steven Jay Lynn, John Ruscio and Barry L. Beyerstein, ''50 Great Myths of Popular Psychology'' (Wiley-Blackwell, 2010).
* Lowell Thomas, preface to Dale Carnegie, ''How to Win Friends and Influence People'' (Simon & Schuster, 1936).
* Marcus E. Raichle and Debra A. Gusnard, "Appraising the brain's energy budget," ''Proceedings of the National Academy of Sciences'' 99, no. 16 (2002).