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[[caption-width-right:324:Struck by a radioactive[[labelnote:*]]MRI[[/labelnote]] seizure, Peter Parker gained the ability to use proportional amounts of his brain!]]

->''"[This myth is] one of the hardiest weeds in the garden of psychology."''
-->-- '''Donald [=McBurney=]''', neuropsychologist

A situation where a character's miraculous abilities are not so much a product of "superpowers" as this being something humans in the series universe could have but are unable to access for some reason. That is, until they reach BrainCriticalMass.

This trope name comes from the oft-repeated but false assertion that humans only use 10 percent of their brains. We use all of our brains, just not all at the same time-in much the same way that hitting a few specific notes on a piano will produce a beautiful tune, whereas mashing them all at the same time would only create a crashing cacophony.

There are occasions in some people's lives in which the entire brain fires up at once. They're called seizures.[[note]]More precisely, seizures occur when the parts of the brain start firing off randomly. In some general seizures, the entire brain can have neuronal activity at once for brief moments.[[/note]]

For exceeding the limitations of the body to epic effect, see CharlesAtlasSuperpower. Also see PinealWeirdness, which tends to show up in similar places. Very prevalent in SciFi as a common trope with mentalists and [=ESP'ers=].

[[JustForFun/TropesExaminedbyTheMythBusters This trope was examined by]] the Series/MythBusters, throwing the 10% theory right out the window when it was proven that the human brain is at least 15% active ''while sleeping'', and even more so when awake. There is debate as to how much of our brain activity takes place on the level of conscious thought, with roughly a tenth being a common figure cited, but this is still very different from claiming our brains are 90% inactive.

----
!!Examples:

[[foldercontrol]]

[[folder:Anime and Manga]]
* ''Manga/{{Akira}}'' has Tetsuo and the Espers, who have crazy mental abilities due to this trope. It's implied that the rest of humanity has the same potential, but it goes unrealized.
* In ''Franchise/DragonBall'', all humans have the potential to fly and shoot energy beams - if they are lucky enough to find someone who can teach them how to use Ki energy.
** Though Ki is moreso a "life" energy than a "mental" one, seeing as how all people (quite frankly any and all living beings put out Ki regardless of mental capacity such as plants) possess Ki, which is more of a indicator of their strength
* The ''Night Head Genesis'' anime states at the start that normal people leave ''70%'' of their brain unused. Once again, this explains psychic powers.
* ''Manga/FistOfTheNorthStar'' does something similar with ''breathing''. The real secret to Kenshiro's CharlesAtlasSuperpower is harnessing the traditionally untapped 70% of his breathing. The Ripple in ''Manga/JoJosBizarreAdventure'' works that way, too.
* The Stone Mask-created [[OurVampiresAreDifferent vampires]] in ''Manga/JoJosBizarreAdventure'' gain their power through the activation of unused parts of the brain via acupuncture. This awakens the human's evolutionary potential (with abilities like WallCrawling, liquid eye beams, superspeed/strength, regeneration, sucking blood through their fingers, and creating zombies) and it inverts the lifeforce energy in their bodies (making them undead-like beings weak to sunlight and [[BattleAura Ripple]], the amplified essence of life)
* Played straight in ''LightNovel/ACertainMagicalIndex'', as the eponymous character has a PhotographicMemory, and can only retain 1 year of memory in her mind, because 85% of it is taken up with an eidetic recollection of the [[NeuroVault complete contents of 103,000 spellbooks]]. [[spoiler:That is, until it gets subverted with a sledgehammer when a professor reveals that the "15% left over for a year's memories" is complete BS and ''gives a proper explanation of how the mind works'' in the series. Cue SugarWiki/MomentOfAwesome as the hero realizes that he's been played for a sucker.]]
** The main character even realizes he's a sucker when he does the math: if 15% = 1 year then you would die around the age of 7.
* ''Anime/MobileSuitGundam'''s Universal Century:
** ''[[Anime/MobileSuitGundamCharsCounterattack Char's Counterattack]]'' (where it is mentioned) may use this explanation for why [[PsychicPowers Newtypes]] exist--that people used only a part of their brains on Earth, and began to use the rest after moving into space. However, it was said to be "half" of the brain being used, not 10%. Also the conversation was between a couple of teenagers, so they may simply not know what they're talking about (they also take a fairly romantic interpretation of the idea/purpose of Newtypes, which Gundam [[SlidingScaleOfIdealismVersusCynicism goes back and forth on)]].
** This first appeared in the writings of Zeon Zum Deikun, inventor of the Newtype concept, in the ''Anime/MobileSuitGundam'' novelizations.
** This is in turn based on the writings of Timothy Leary, specifically the 8-Circuit Model of Consciousness which predicted that people's brains would develop in new ways in the future, becoming more enlightened to cope with the challenges of space travel.
* The foundation of superpowers in ''Manga/{{NEEDLESS}}''.
* In an episode of ''Manga/KatekyoHitmanReborn'', Reborn gives Gokudera an unique brand of TrainingFromHell by making him eat ramen while withstanding I-pin's Gyoza-ken. Reborn's technical explanation is that, since the Gyoza-ken affects directly the brain, the fact of being able to eat ramen while resisting the muscular spasms the technique provokes would force Gokudera to use all of his brain capacity (whose standard usage is defined here as 30%).
* This is part of the premise for ''Manga/{{Psyren}}''. Like many others, this explains psychic powers, though they seem no less limited than any other set of superpowers in other series.
* In ''BIchi'', the Clowns can supposedly use 50 to 60% of their brains when activating their powers. However, this detail in only mentioned in the introduction and the Clowns' powers don't have anything to do with using more of their brains in the end.
[[/folder]]

[[folder:Comic Books]]
* ComicBook/{{Deathstroke}}, a.k.a. Slade, from ''ComicBook/TeenTitans'', has this as one of his powers (though it's not stated outright in the series, only the comics). Later retconned in that he uses his brain in various ways that regular humans do not. His grey matter got re-routed and reprogrammed. Makes slightly more sense - at least in terms of comic book science.
** In all fairness, this original trope was applied to him back when most people thought it really was true. It was dropped once that changed.
* According to Todd Ingram in ''ComicBook/ScottPilgrim'', ninety percent of your brain is filled up with curds and whey. Hence his [[ItRunsOnNonsensoleum telekinetic vegan power]]. Arguably an aversion, though, as Todd is shown to be the dimmest and least imaginative of the League of Evil Exes. While it is canon that veganism gives psychic powers in the Pilgrim universe, Todd's explanation comes off more like a thinly-veiled insult, and Kim in particular seems skeptical.
** Also, when he's revealed to have broken the rules of veganism, he had his powers taken by the "vegan police".
* This fake statistic appeared in the ''ComicBook/IronMan'' mini "Hypervelocity", as the AI protagonist was frustrated at being forced to function at a relatively slow "cognitive clockspeed".
** Mmm, it's clearly a take off on the myth, but I don't know if it's scientifically inaccurate in this case. (The idea of an AI who initially believes himself to be human setting his initial amount of processing power to reflect the human level isn't that crazy.)
* [[Franchise/TheDCU DC Comics]] villain The Key once claimed to have tapped into "the ninety percent of the brain we never use" via a device he built, which allowed him to devise all manner of amazing plans and schemes. This is an aversion, though, as it also drove him completely mad, leading to the implication that he only THINKS he's tapping into new parts of his brain.
* An odd ''Franchise/{{Superman}}'' story featured a stand-up comedian having part of his unused brain areas activated in an accident, which gave him telekinetic powers, which he used unconsciously to become a sand-covered monster that tried to amuse people to counter his fear of not being laughed at. He was only cured once Superman used his super laughter so that he could finally hear through all the sand that someone was laughing. Okay?
* ValiantComics invoked this with the [[DifferentlyPoweredIndividual Harbingers]], people with StockSuperpowers. Unlike their [[{{Mutant}} equivalents]] in some other comic universes, Harbingers are not physically different from other humans. Elevated levels of activity in their brains result in [[PsychicPowers psionic abilities]] that give them their powers. Ordinary humans can duplicate Harbinger powers through the use [[AppliedPhlebotinum special cybernetic brain implants]].
* In a statement that impressively manages to be wrong ''in every particular'', ''ComicBook/{{Marville}}'' gave us this as an add-on to reciting the 10% myth verbatim:
-->'''Guy Who Is Probably God''': Listen, it would be a disaster if humans used all of their brains[[note]]see above[[/note]] -- Einstein got 20% more[[note]]impossible for obvious reasons, although there were ''some'' anatomical and cellular oddities with his brain; also, while Einstein was pretty damn smart, ''three times'' more intelligent than the average person is kind of pushing it[[/note]] and he accidentally drew the roadmap that led to nuclear weaponry[[note]]Oy. First, Einstein's theories had actually very little to do with nuclear fission - they explained why there was a lot of energy available, but the majority of the science behind nuclear weapons came from Becquerel, the Curies, Bohr, Fermi, Meitner, Frisch and Szilard, and Einstein wasn't even on the Manhattan Project or any other experiment into nuclear fission. Also, Einstein ''deliberately encouraged'' the initial development of the atomic bomb as a deterrent against the Nazis, who were also working on their own A-bomb project; it should be stressed that he was horrified when the bomb was actually used, especially since he'd visited Hiroshima before the war.[[/note]].
[[/folder]]

[[folder:Film]]
* This is part of the plot of the 1986 film ''Film/FlightOfTheNavigator'', where a young boy discovers an alien probe had experimented with using the unused ninety percent of his brain for [[NeuroVault data storage]].
-->'''Max:''' Back on Phaelon, we discovered that your inferior species uses only ten percent of your brain. So we filled it all the way up with star charts to see what would happen.\\
'''David:''' What happened?\\
'''Max:''' ''It leaked.''
* Richard uses this as an insulting mnemonic device to help Film/TommyBoy remember the figure 1.5%.
-->'''Richard:''' Let's say the average person uses 10% of their brain. How much do you use? '''1.5%.''' The rest is clogged with malted hops and bong resin.
* Besides the milk-white complexion and hairlessness, this is what made the protagonist of the film ''Film/{{Powder}}'' so special.
* Pretty much how [[MyBloodRunsHot Extremis]] is applied in ''Film/IronMan3''. Aldrach, through years of research, has found that the human brain has an empty space, hinting that humanity is not at the apex of evolution.
* ''TheLastMimzy'' does this; their newly-unlocked abilities include telepathy, telekinesis, and super-hearing, as well the ability to control spiders by emitting certain frequencies, to send objects through small warp portals, and to draw ancient patterns without ever having seen or heard of them. In the future, levitation is also a standard part of humanity's milieu.
* It is implied in ''Film/{{Phenomenon}}'' that the incredible mental and psychic abilities John Travolta's character, George, suddenly gains after seeing a strange light in the sky is caused by [[spoiler:a tumor spreading across his brain and activating unused parts of it. Also, killing him.]]
* In ''Film/DefendingYourLife'', everyone on Earth is said to use 3-5% of their brains. When a person dies and goes through the CelestialBureaucracy, they have the chance to [[AscendToAHigherPlaneOfExistence move up to the next level]], where it's possible to use more of their brain. Then after that lifetime, they have the chance to move up to the next level and so on; each level allows one to use more and more of one's brain, which means being more intelligent and less afraid.
* Referenced for the sake of a joke in ''Film/WeddingCrashers''. "You know how they say we only use ten percent of our brains? I think most people only use ten percent of their hearts."
* In ''Film/MyFavoriteMartian'', Uncle Martin states that Martians earn their powers from fully using their brains. Tim disagrees, and the reply is "[[InsaneTrollLogic Your astronauts pee in their spacesuits. Case closed.]]"
* ''Film/TheSorcerersApprentice'' uses this trope straight to describe how sorcerers get the [[AWizardDidIt powers]].
* ''Film/{{Inception}}'' says this is why in dreams your brain can work faster, as the majority of your brain's processing ability is devoted to processing sensory perceptions. With the use of shared dreaming technology, the brain can work much faster, allowing for a dreamworld hour to pass in minutes in the real world.
* In ''Film/ScottPilgrimVsTheWorld'' vegan evil ex-boyfriend Todd Ingram claims the source of his psychic powers is that he's able to use more than 10% of his brain because isn't gunked up with all that filthy animal protein. The brain is ''made'' out of animal protein, but given that Todd also says that he does not know the meaning of the word "incorrigible" [[spoiler:and he does not]], this creates [[UnreliableExpositor reasonable doubt of the credibility of his claim]].
** Of course, he loses his powers not because he violated the vegan diet but because the Vegan cops took them away (because he violated the diet). This pretty much negates his claim.
* In ''My Stepmother is an Alien'' the alien Celeste explains that "We use 104% of our brain capacity, as opposed to your 36%."
* In the 2009 film ''Film/RaceToWitchMountain'', the extraterrestrial humans Sarah and Seth have access to telekinesis, telepathy, and phasing, which Sarah states the humans on Earth can not use yet, because they "haven't learned to use that part of [their] brain yet." Ironically, in an interview with Creator/AnnaSophiaRobb, who plays Sarah, she confirmed that the director wrote that line in because he wanted to be "as scientifically accurate as possible."
* In the film ''Film/{{Limitless}}'', starring Bradley Cooper and Creator/RobertDeNiro, Cooper plays a down-on-his-luck writer who takes a smart drug called NZT-48 that, according to the drug dealer who introduces it to him, allows him to access 100% of his brain as opposed to "the twenty percent", granting him superhuman intelligence and prescience.
* Implied in ''Film/TheShadow'', in the end, the BigBad gets a spike through his head and has to have a part of his brain that "no one uses" removed. It turns out that this was where his psychic powers were located.
* ''{{Film/Lucy}}'' is playing it 100% dead straight, straighter than we've seen in a decade or two. Unlocking more and more takes her down the Jean Grey path of increasing mind powers. Using 100% of one's brain capacity leads to omniscience ''and'' omnipotence, making the title character practically a PhysicalGod. The trailer also features Morgan Freeman's character [[ArtisticLicenseBiology --said to be one of the world's top experts on the workings of the human brain-- repeating the misconception]]. According to WordOfGod, they were aware this is just a myth but chose to go with it anyway as a WhatIf.
[[/folder]]

[[folder:Literature]]
* ''Literature/TheImmortals'': Daine makes a reference to this in ''Wolf-Speaker'' while sharing the mind of a wolf whose brain was changed by association to her magic: "Numair had said, in an anatomy lesson, that humans used little of their brains... For Brokefang the difference was that each nook and cranny of his skull was packed with ideas."
* The Creator/DouglasAdams book ''Literature/TheLongDarkTeaTimeOfTheSoul'' plays with this: a character in a coma has a dream in which her mind is represented by an infinite collection of cabin trunks, of which ten percent contain past memories, and the remaining ninety percent contain [[EverythingsBetterWithPenguins penguins]].
* Comes up multiple times during ''Literature/TheDresdenFiles''. Harry Dresden's mental passenger Lasciel resides in the so-called "unused parts of Harry's brain.'' [[MrExposition Bob]] even quotes the 'ten percent' stat when they discuss it. All of this could be partially [[HandWave hand waved]] with the previously established plot element that Wizards have a different cellular biology than most, allowing for better healing and longevity. It's possible Wizards have abnormal neurology.
* Artemis's magic in ''Literature/ArtemisFowl: The Lost Colony'' is another case of this trope. Humans lost the kind of brainpower necessary for that long ago.
* Creator/RoaldDahl's ''Literature/{{Matilda}}''; the eponymous little girl gained access to psychic powers because she was willing to use more of her brain than the rest of her family was. It's all but stated, in the book, that this is a direct result of her not being intellectually challenged enough, since she [[spoiler:starts to lose her powers once she's moved up a grade]] at the end of the book. The same explanation [[spoiler:(but without power loss)]] is given in the FilmOfTheBook.
** This could be more of a jab at Matilda's family, since they aren't exactly the brightest bulbs in the shed. The trope isn't actually invoked at any point.
* Mark [=McHenry=] of ''Literature/StarTrekNewFrontier'' could not only use 100% of his brain, he could specify at any given time what percentage of his brain is dedicated to what activity. This is because [[spoiler:Mark isn't quite human, due to his being descended from the Greek God Apollo.]]
* Comes up in ''[[ComicBook/XWingSeries Starfighters of Adumar]]'', but context makes it pretty clear that this is a joke. Wes is known for being somewhat [[{{Manchild}} immature]], and he tells Wedge that he thought he heard something last night, when Wedge was... [[DidYouJustHaveSex getting lucky]].
-->'''Wedge''': "That old lack of oxygen thing will get you every time. How much brain damage did you suffer? [...] And, more importantly, was it to any of the parts of your brain that you use, or was it in the majority portion?"
* In ''Literature/{{The Secrets of the Immortal Nicholas Flamel}}'', this is the basis for the idea of having one's powers "Awakened".
* ''Literature/TheZombieSurvivalGuide'' makes this same error in comparing zombies' senses to those of humans, speculating that undead without eyes have a "sixth sense" derived from the unused part of the brain. Oh, and it claims that we, the living, only use ''5%'' of our brains, doubling this trope's inaccuracy.
* The Franchise/DoctorWhoExpandedUniverse novel ''The Gallifrey Chronicles'' comes ''very close'' to getting this right ... but doesn't.
-->There was an old myth that humans only used ten percent of their brains. This was a simple misunderstanding. Give or take, there was activity in every part of the human brain. But the physical structures were capable of ten times the activity they performed. It wasn't that a human being had a brain like a house with nine tenths of the rooms sealed off, it was more like a road network wasn't carrying as much traffic as they were designed to carry.
* In ''Discworld/SmallGods'', Terry Pratchett said that the other 90 percent of the brain powers a sort of WeirdnessCensor so that the fact that the entire world we take for granted is, in fact, amazing, is ignored.
-->It is a popular fact that nine-tenths of the brain is not used and, like most popular facts, it is wrong. Not even the most stupid Creator would go to the trouble of making the human head carry around several pounds of unnecessary gray goo if its only real purpose was, for example, to [[BrainFood serve as a delicacy for certain remote tribesmen in unexplored valleys]]. It is used. And one of its functions is to make the miraculous seem ordinary and turn the unusual into the usual.\\\
Because if this was not the case, then human beings, faced with the daily wondrousness of everything, would go around wearing big stupid grins, similar to those worn by [[TheStoner certain remote tribesmen who occasionally get raided by the authorities and have the contents of their plastic greenhouses very seriously inspected]]. They’d say “Wow!” a lot. And no one would do much work.
** From a certain point of view, this description is almost entirely accurate. A huge amount of brain power goes into basic data filtering and interpretation, all so that the relatively small part of our brains that does the thinking we're conscious of doesn't get overwhelmed. Show a person the raw data of their nerves and it would just look like static.
* The protagonist of ''[[http://www.gutenberg.org/files/32272/32272-h/32272-h.htm Insidekick]]'' by J. F. Bone develops psi powers (telepathy and teleportation), plus eidetic memory, after being invaded by a symbiont which activates a "large dormant portion" of his brain.
* In Stephen King's ''Literature/{{Cell}}'', the people who are hit by the Pulse lose almost all of their higher level reasoning skills. After this, [[spoiler: they slowly regain higher level thought, but they use unusual parts of their brain to do it, resulting in them developing telepathy and eventually telekinesis]]. Granted, this is just a hypothesis in-Universe, but the "we only use ten percent of our brains" myth gets thrown around a lot by some highly educated people.
* In ''Beneath the Dark Ice'', the protagonist's superhuman abilities are thought to have come from when he was shot in the head in a way that forced the brain to direct more blood to the areas of the brain with the most 'unknown functions'. How this accounts for super strength and endurance is not obvious.
* The Mule from Literature/{{Foundation}} could use an intellect ExplosiveOverclocking power on others (cause intuition and creativity to skyrocket, but has bad effects on the one it is used on). The way it is described, it seemed less about using new parts of the brain, and more about using all of it ''non-stop'' without any chance to rest for weeks on end, but he, himself, mentioned a normally low efficiency (20%) as an explanation. This could be attributed him having "education, that of the tramp worlds, and the backwash alleys of space."
* In Creator/IsaacAsimov's ''Pebble in the Sky'', the main character, who has inadvertently been pushed forward from our time to that of the novel, during the Galactic Empire period that leads up to the Foundation books, gets an experimental "Synapsifier" treatment in the hope it will help him learn the language. It does that and more ... he starts becoming telepathic, and strongly enough so that at one point he kills one of the bad guys that way, without even intending to.
** Played with in that novel makes quite clear ''why'' humans only use a small percentage of their brain at any one time: using more is damaging to the person in question, to fatal levels (partly because, as opposed to the Mule's power mentioned above, once the Synapsifier has been used on a person the effect is permanent). Evidently those ninety percent are there to keep the brain running for year after year.
* This is a big part of the plot of the ''Literature/MyTeacherIsAnAlien'' series. In the second installment, one boy, a school bully of below-average intelligence, has his brain "fried" to make him a genius and a telepath. In the third, the aliens remove the protagonist's brain temporarily to study it. The reason is that humans have the most powerful, yet under-used, brains in the galaxy, and the aliens are trying to figure out why we suppress our supposedly vast mental powers.
** [[spoiler: It's part of our unconscious HiveMind. Turns out we used to use it all, but as humanity spread the sheer amount of psychic chatter overwhelmed the conscious mind, and so humans suppress it to stay sane]].
* Mentioned in David Gerrold's novel ''When Harlie Was One'' as the supposed "reason" why the sentient computer of the title, despite being like a human brain, is so much more efficient.
* In the short story [[http://sfreader.com/contest-2008-1.asp "On a Clear Day You Can See All the Way to Conspiracy"]] by Desmond Warzel, a caller to a radio show invokes the "ten percent" myth and the host smacks him down, even giving the "seizure" explanation mentioned in the introduction above.
[[/folder]]

[[folder:Live-Action TV]]
* ''Series/{{Alphas}}'': Stanton Parrish has a variation of this: He has the ability to consciously control every process in his brain, even those that are not consciously controlled in ordinary humans. This makes him able to instantly recover from any injury and prevents him from aging. However, it comes with several downsides: His emotional relationships with others are disrupted, making him similar to a [[TheSociopath sociopath]] and his ability to retain memories is disrupted to an extent (likely due to the fact that his brain, powerful as it is, still lacks the capacity to hold over 200 years worth of memories all at once.)
* ''Series/{{Angel}}'': Gunn clarifies that his mental capacity wasn't "enhanced" when Wolfram & Hart made him a lawyer; the Senior Partners just "revved up some idling brain cells."
* Johnny's powers in the television version of ''Series/TheDeadZone'' come from the fact that a normally unused part of his brain became active to compensate for a damaged section.
* Referred to in the {{premiere}} of ''Series/{{Heroes}}'' as an example of one way humanity might make a sudden evolutionary leap, but then mercifully dropped. Only to be brought back up in season three, in a speech by Sylar.
* ''Series/{{Eureka}}'''s scientific adviser was on record as making sure that when that concept was used on the show, the line was "ten percent... at any one time" specifically to dodge this trope.
* ''Series/StargateSG1'' and ''Series/StargateAtlantis'' have several instance where this comes up and is dodged in the same manner that Eureka does -- by upping the percentage used at a time, rather than overall. Increasing the amount used to almost 100% is one of the criteria to AscendToAHigherPlaneOfExistence (or at least, it's required for doing so without somebody who's already ascended helping you).
** One ''Atlantis'' episode involves a device that artificially boosts brain activity in order to facilitate ascension. Which proved problematic because the human brain isn't ''supposed'' to function that way: eventually it would have basically caused a permanent seizure, so once brain activity got to the ascension threshold, it was basically a matter of "ascend or die."
* Referred to in ''Series/KyleXY''. The titular Kyle has a highly advanced brain, learning to speak in one day, and learning kung fu and Chinese from watching an old Bruce Lee movie. They give him a CAT scan and the scan showed he used 80% of his brain. However, the doctors noted this as strange, citing the problems one would have at 100% brain usage (such as seizures), and wrote it off as a machine malfunction. The audience and the character Josh know it's not a malfunction by being GenreSavvy. It is later shown that if he uses his powers too much, he will get a seizure.
* ''Series/JohnDoe'' actually acknowledges that only about 10% is in use at any given time, but implies that tapping into the other 90% at the same time is what allows some of the characters to use their psychic abilities.
* In ''Series/{{Seinfeld}}'', when George stopped having sex, his brain was free to do other things, accounting for his sudden burst of knowledge. Jerry compared George's brain to a cabbage, with a tiny leaf being the part he normally devoted to anything that wasn't sex. This seems to work the opposite way for women (as shown with Elaine's sudden stupidity), by which Jerry meant that most of men's brainpower is normally invested toward obtaining sex, while a woman always has men available to take care of her sexual needs ''for'' her; therefore a celibate man becomes super-intelligent since his brain is freed up, while a celibate woman loses all her brainpower into thinking about sex.
* In ''Series/{{Fringe}}'', the 10% fallacy is averted only to be replaced with a different (even more absurd) rationalization. [[spoiler: A MadScientist several decades in the past developed a drug that prevents babies from losing the natural potential they have at birth.]] In a DoubleSubversion the MadScientist in question fails completely in clinical trials only to be proven right when [[spoiler: Olivia]] develops psychic powers. Maybe.
** Another subversion on that show: The reason Walter is mentally askew is that [[spoiler: 10% of his physical brain was removed and implanted in other people's brains, giving them all bits and pieces of a complex design, in a bit of Lego brain surgery. Getting back that 10% puts him on track to solving an important puzzle.]]
* In the last episode of ''Series/LoisAndClark'', Dr. Mensa uses the rest of his brain and gets [[MyBrainIsBig an enlarged brain]], the power of mind control and the moniker "Fat Head".
* The main plot line for an episode of ''Series/HoneyIShrunkTheKids''. To make matters more silly, accessing the other 90% gave the character in question godlike powers. All this was caused by a device that was established in a previous episode to be used for [[FreakyFridayFlip brain-swapping]].
* In ''Series/StarTrekDeepSpaceNine'', this is cited as why Dr. Bashir can lose a portion of his brain and be completely fine (this was before Bashir was {{Retcon}}ned to be super-intelligent.)
* Spoofed in an Italian RealTrailerFakeMovie parody of ''Limitless'', mercilessly titled ''Italiano Medio'' (''[[SelfDeprecation Average Italian]]'').
-->'''Protagonist's friend:''' You know that story, that we use only twenty percent of our brain? *hands him pill*
-->'''Protagonist:''' OK, I'll try it just out of curiosity. *swallows pill*
-->'''Protagonist's friend:''' With this, you'll only use ''two percent''.
* Disproven on ''Series/{{Mythbusters}}'', Tory's brain scans showed him using 15-30% of his brain, depending on what he was doing.
* Referenced episode 5 of Series/AlmostHuman where an alleged [[ISeeDeadPeople spirit medium]] says her powers are the result of the Cerebellux procedure, which enhances use of brain pathways.
[[/folder]]

[[folder:Other]]
* There are plenty of jokes referring to people ''[[InvertedTrope without any brain at all]]'' working as [[AcceptableProfessionalTargets politicians, lawyers, and the like]]. An old joke tells of a Brit, a Frenchman, and a German arguing whose medicine is better; the Brit mentions a man whose kidney was removed and he went back to work in three weeks, the Frenchman mentions a man whose lung was removed and he went back to work in two, and the German mentions a man whose brain was removed and he went on to ''[[AdolfHitler lead the country]]'' within a week. Modern variants often replace the three with men from different states, the last one being a Texan talking about GeorgeWBush.
[[/folder]]

[[folder:Tabletop Games]]
* ''TabletopGame/{{Aberrant}}'' uses this as part of the MetaOrigin for novas. Most humans have an underdeveloped, uncharted node in their brain that maps the background forces of the universe. When a nova Erupts, this node becomes active, allowing for limited manipulation of reality -- a.k.a., superpowers.
[[/folder]]

[[folder:Video Games]]
* In ''VisualNovel/ChaosHead'', Norose muses that Gigalomaniacs use the remaining 90% of their brain unlike normal humans, and this is responsible for their abilities. And possibly even worse, it's also stated that 80% of the brain is used for processing visual data.
* ''Franchise/AssassinsCreed'' has Eagle Sense and Eagle Vision. It lets the user make out if the people surrounding them are friends, enemies or targets. The science behind it all is that [[spoiler: humans were created by a race of other beings and then cross-bred when the other race went extinct. Every human has a certain concentration of DNA from those beings and the higher it is the higher this sense is developed]]. Most people aren´t aware of this ability but it can be awoken through [[spoiler: reliving memories of an ancestor]]. The sense can range from simply seeing people in blue, red, yellow when standing still over being able to walk around while doing it to seeing the paths people went as colored lines.
* This is given as the reason why Fuka, a human [[OrdinaryHighSchoolStudent Ordinary Middle School Student]], can keep up with her demon teammates in ''VideoGame/Disgaea4APromiseUnforgotten''. She deluded herself into thinking the afterlife is AllJustADream, and since it's her dream, she's free to do anything she wants. This allows her brain to unlock her full potential.
* In ''VideoGame/DragonBallOnline'', set more than 200 years after the main series, this happened with the book "Groundbreaking Science" written by Gohan, explaining Ki manipulation to the saiyan blooded humans.
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[[folder:Web Comics]]
* ''Webcomic/CaseyAndAndy'' examines this, thanks to [[http://www.galactanet.com/comic/view.php?strip=369 Anti-Stupid Science Man!]]
* Parodied in ''Webcomic/ScaryGoRound'', where a man survives having 90% of his brain eaten by a zombie because by incredible coincidence she ate only the 90% that no one uses.
* Sofia of ''Webcomic/BreakpointCity'' explains her telekinesis this way.
--> ''You know how most people only use 10% of their brain? I use 11%.''
* ''Webcomic/FreakAngels'' seems to be hinting at the fact that they have simply not reached their full psionic potential. Arkady's continual experimentation with her abilities seems to be a testament to this.
* A joke that unfortunately never made it into ''Webcomic/PennyArcade'' but does show up on their podcast uses the concept:
-->"You know how people only use ten percent of their brain?"
-->"I've heard that."
-->"Well I only use ten percent of my ''penis''."
** [[http://www.penny-arcade.com/comic/2007/2/19/ One comic]] uses this trope as part of an advertisement for "air for gamers".
[[/folder]]

[[folder:Web Original]]
* A Website/{{Cracked}} article compares this notion to becoming a better writer by using every key on your keyboard in every sentence.
* Parodied in ''Script/AHDotComTheSeries'', episode "The Narcissus Syndrome":
-->'''Thande''': You know how we only use ten percent of our brain capacity?
-->'''Torqumada''': No, because that's a ridiculous urban myth.
-->'''Thande''': Shut up, I'm trying to [[LiesToChildren explain something]] to the unscientific Muggles here.
* In ''WebVideo/ToBoldlyFlee'', it's stated that a critic's brain usage is typically [[SelfDeprecation 5%]], but [[spoiler:Ma-Ti's brain uploading]] has boosted Spoony's brain usage to 92%.
* [[http://www.scp-wiki.net/scp-1475 SCP-1475]] of the Wiki/SCPFoundation is a {{Deconstruction}}. He gave himself a [[DisposableSuperheroMaker non-reproducible drug]] that lets him use 100% of his brain 100% of the time. This not only gave him [[MasterOfYourDomain complete control over his body]], but let him rewire his brain so that [[TheSleepless he doesn't need to sleep anymore]]. However, in a true case of BlessedWithSuck, this completed destroyed his autonomic nervous control (that is, the body's ability to automatically regulate the heart/lungs/etc), so he has to spend most of his concentration on keeping himself alive. Not only does this not leave him much concentration to use his voluntary muscles, he's also suffered permanent damage to a lot of his organs due to having messed it up in the past.
* [[http://www.villainsource.com/ Villain Source]] sells brain pills that are guaranteed to increase your IQ by 300% or your money back! (The small prints adds that if you believe this, then you really need those pills).
* ''TheOnion'' [[https://www.youtube.com/watch?v=-kdkFJa2VJM parodied]] the concept with a man who invented a device that lets him fire all his neurons at the same time. Every time he turns it on, he has a seizure.
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[[folder:Western Animation]]
* Parodied in ''WesternAnimation/TheSimpsons'' when Bart becomes ultra-focused after taking medication for attention deficit disorder: "You know how most people use only ten percent of their brains? [[TriviallyObvious I am now one of those people.]]"
* The ''WesternAnimation/BatmanBeyond'' episode "Mind Games" has an UnreliableExpositor claim this to explain psychic powers.
* In ''GodzillaTheSeries'' Dr. Nick Tatopoulos states this is the reason as to why the aliens were able to copy their minds into human brains.
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[[folder:Real Life]]
* TruthInTelevision to an extent; humans can still function (though not to full capacity, obviously) if parts of their brains are removed. Most notably, the practice of lobotomizing criminals was considered a humane alternative to the death penalty for quite some time. Splitting the corpus callosum (the tissue connecting the two hemispheres of the brain) was a common cure for seizures in the 70s (and is still occasionally done in severe enough cases)[[note]]Disconnecting the two sides of the brain prevents the seizure from spreading to both hemispheres and limits the severity of the episode.[[/note]]; the side-effects only occur in very specific, usually engineered scenarios, and are much preferable to the seizures in the first place.
** Removing a damaged hemisphere can even result in a significant ''improvement'' in cognitive function... in the other hemisphere, which rewires itself and takes on the tasks once done by the removed half. Whether it improves overall ability is unlikely, given that split-brain patients often act like two people sharing one body, and often work at cross-purposes.
** The basic rule now is that you do '''not''' remove any part of the brain unless it's absolutely necessary, because functions ''are'' centralized to specific parts, and depending on what is being lost and the patient's age there are distinct upper limits to how much function will be regained. People have permanently lost the ''concept'' of color, while prefrontal lobotomies are a good source of NightmareFuel...
* One source of the myth itself (of many possible ones) is a series of experiments done on rodents in which the poor creatures had large parts of their brains burned away but could still run a particular maze. However, all this proves is that memory is distributed in the brain rather than localized; the rodents still lost other functions. Besides, mice aren't men.
* Approximately 90% of cells in the brain are not actually neurons, but glial helper cells that keep the neurons alive and functioning. So only 10% of the cells are used directly; the other 90% are vital to keeping that 10% healthy and alive.
** However, not only are these cells necessary for brain function, but if you stick human glial helper cells in mouse brains the mice become smarter, suggesting that they do play a pretty important role in cognition.
* The famous [[http://en.wikipedia.org/wiki/Phineas_Gage Phineas Gage]] had a railroad spike driven through his brain, causing massive damage to his frontal lobes. He recovered, memories and abilities mostly intact, but with a radically changed personality-friends and family said he was "no longer Gage." Despite the injury, he managed to live for another twelve years (it apparently damaged the pain receptors, too, as when he was brought in for treatment Gage casually asked the doctor whether he was all right, oblivious to the freaking ''metal rod'' lodged through his skull).
* There is a famous case of a character who came to a doctor complaining of headaches, and turned out on the X-rays to have no cerebellum. Apparently, he'd been born without one, and the cerebrum had simply taken over all the necessary tasks-to such success that he was working as a steeplejack!
* Dolphins and other cetaceans have adapted to function actively while 50% of their cerebrum is ''asleep''. This is good, since their breathing is entirely under conscious control, and total loss of consciousness thus equals suffocation.
* Some birds can also have half their brain asleep while the other half keeps watch for danger from one eye.
** Generally speaking, all air-breathing aquatic animals and all land-based prey species that sleep out in the open do this as well, sleeping with only half their brain at a time. Only animals that tend to hide themselves in very well protected locations such as dens or single-family bungalows in the suburbs can afford to sleep with their entire brain.
* [[IdiotSavant Autistic savants]] are people who, due to cognitive disabilities, have focused on specific skills and as such have refined them to an unusually high skill level, sometimes operating in a somewhat bizarre manner (such as some artists who, rather than sketching, immediately start drawing the finished drawing piece by piece in proportion; some of these skills can be extremely narrow or bizarre as well). While the common perception is that this is a DisabilitySuperpower, in reality ALL humans are capable of developing savant-like abilities, and indeed many "ordinary" people do have savant-like abilities. The reason savants stick out so much is because their ability is so far in excess of everything else that they can do, they become defined by it as far as other people (and frequently they themselves) are concerned. People who ''don't'' suffer from cognitive disabilities aren't referred to as savants, they're just viewed as highly skilled individuals.
* There was a girl who had half her brain gone. The left hemisphere was just not there. So far she seems to be living a fairly normal life with a fairly normal, if quirky, degree of intellect.
** While half of the brain can be removed in a young child and they can still live a fairly normal life due to the other half compensating (due to the symmetrical design and the child's brain being extremely flexible) it's worth adding that an adult who had half their brain removed in adulthood would not be able to function properly.
* May have originated when we only ''knew the function of'' (some small percentage) of the brain, and that got misreported as "We only ''use'' (some small percentage) of our brain." Areas having to do with other than motor control or sensations are now called "association areas", and they have a role in interpreting, integrating, and acting on sensory input in combination with stored memories. Higher brain functions, in other words. In the same way that your house has only a fraction of its rooms being actively used at any given time, only a fraction - a rather large one - of your brain is active at any given moment - but, as with the house, that doesn't mean the rest isn't useful. The history of this trope is fairly well outlined in the free first chapter of [[http://eu.wiley.com/WileyCDA/WileyTitle/productCd-047143499X.html this book]]. Furthermore, Bill Nye (y'know, [[Series/BillNyeTheScienceGuy the Science Guy]]) wrote a fairly accessible essay on the subject [[http://web.archive.org/web/20080506104856/http://encarta.msn.com/encnet/Features/Columns/?article=BNBrainCapacity here]].
** It's been shown that the ability to interpret and integrate sensory input takes a large amount of processing power from the brain. Octopuses, with their eight arms, have to give up complete control of their arms just to use them all at once. They still can't form a mental image of whatever it is their arms might be holding.
** TL;DR: We do use all of our brain, it's just that most of it is for things like graphics rather than "consciousness".
*** Indeed, a lot of things which seem simple and trivial to us are actually extremely difficult and take an enormous amount of computational power to do. Computers can do math vastly faster than we can but are uncreative, cannot understand human speech very well (and have a great deal of difficulty creating it), and have trouble seeing the world as a 3D environment in the way that we do. This is part of why AI is so difficult-for a computer, doing extremely complicated calculations is simple, but navigating a three-dimensional environment, let alone responding to something else moving around in said environment, is really, really hard.
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