Ninety Percent Of Your Brain / Literature

• In Alan Mendelsohn, the Boy from Mars, the Klugarsh Mind Control course claims that only 10% of your brain is in use, and that the secret to telepathy, telekinesis, etc. is learning to access the rest of your brain.
• Area 51: It's revealed eventually that humans don't use much of their mental potential as a result of the Airlia deliberately inhibiting this when they created us.
• In Artemis Fowl: The Lost Colony, it's said that humans lost the kind of brainpower necessary for Artemis's magic long ago.
• 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.
• In Cell, the people who are hit by the Pulse lose almost all of their higher-level reasoning skills. After this, 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.
• Initially played straight in A Certain Magical Index, as the eponymous character has a Photographic Memory, and can only retain 1 year of memory in her mind, because 85% of it is taken up with an eidetic recollection of the complete contents of 103,000 spellbooks. Eventually subverted 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. The main character even realizes that he's been played for a fool when he does the math: if a year's worth of memories really took up 15% of your brain, you'd max out around age 7 and not be able to ever remember anything new.
• In The Destroyer, it's mentioned that Sinanju allows you to use more of your brain, which in turn allows you to do incredible stuff.
• In Diary of a Wimpy Kid: Double Down, Greg hears that humans only use 90% of their brains. He hopes that people don't figure out how to get the last 10%, imagining it being complete chaos.
• In the Doctor Who New Adventures book All-Consuming Fire, a character with psychic abilities (pyrokinesis, specifically) is discovered to have suffered a major head trauma that destroyed a large chunk of his brain. Bernice mentions the 90% thing, and speculates that the man's brain, in the course of rerouting around the damage, started using a previously unused part of the brain and activated the pyrokinesis.
• Comes up multiple times during The Dresden Files. Harry Dresden's mental passenger Lasciel resides in the so-called "unused parts of Harry's brain". Bob even quotes the 'ten percent' stat when they discuss it. All of this could be partially handwaved with the previously established plot element that Wizards have a different cellular biology than most, allowing for better healing and longevity. It's possible that Wizards have abnormal neurology.
• The Eighth Doctor Adventures 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.
• The psychic villain of the Fear Street novel One Evil Summer claims at one point, "You know, they say people use only a small portion of their brains. Well, I use all of my brain. I can do anything. Anything!" Of course, she is kind of insane...
• The Immortals: 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 protagonist of 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.
• The Long Dark Tea-Time of the Soul 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 penguins.
• 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 starts to lose her powers once she's moved up to sixth form at the end of the book. The same explanation (but without power loss) is given in the 1996 film.
• "The Mule": Part of the Emotion Control powers that the Mule had was to cause intuition and creativity to skyrocket, at the expense of their lives. He describes human brains as normally operating at 20% efficiency (essentially failing to use 80%), and he can use his power to force all of it to work non-stop without any chance to rest for weeks on end.
• My Teacher Is an Alien: In the second Novel, one boy, a school bully of below-average intelligence, has his brain "fried", which makes him a genius and a telepath. In the third, the aliens remove the protagonist's brain temporarily to study why humans have the most powerful, yet under-utilized, brains in the galaxy. It's part of our unconscious Hive Mind. 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 so we can stay sane.
• The Name of the Wind explains its magical naming system by drawing a line between the waking mind and the sleeping mind, with the sleeping mind being more powerful and more knowledgeable but difficult to access.
• In Desmond Warzel's short story "On a Clear Day You Can See All the Way to Conspiracy", 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 in the main page.
• Pebble in the Sky: The main character, who has inadvertently been pushed forward from our time to the far future setting of the novel, 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 the novel makes quite clear why humans only use a small percentage of their brain at any one time (within the context of the setting): using more is damaging to the person in question, to fatal levels (partly because 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.
• Mentioned and immediately debunked in Run Program. The person debunking it, Dr. Madsen, compares it to a car driving on a highway. If it was operating at 100% capacity, then every single system would be on at the same time. Imagine wipers constantly working, both the gas and the brake pedals floored, with every single gear engaged (including the reverse), and doors constantly opening and closing. That would be our brains at 100%. This trope is also inverted in the explanation of how Madsen manages to develop a fully functional A.I.: since only a small percentage of the human brain is active at any given time, and a good part of that activity is maintenance of bodily functions (which is simply unnecessary for an A.I.), an artificial intelligence only needs to simulate a relatively small portion of those synapses at a time.
• In The Secrets of the Immortal Nicholas Flamel, this is the basis for the idea of having one's powers "Awakened".
• In Small Gods, the other 90 percent of the brain powers a sort of Weirdness Censor so that the fact that the entire world we take for granted is, in fact, amazing, is ignored. (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.)
  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 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 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.
• Mark McHenry of Star Trek: New Frontier 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 Mark isn't quite human, due to his being descended from the Greek God Apollo.
• This is the operating premise of the Transformers: Generation 1 interactive book Project Brain Drain. The Decepticons plan to drain the awesome untapped mental energies of the human brain from the attendees of a rock concert.
• 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 When Rabbit Howls, Ten-Four opines that people only use 10% of their brains and 3% of their physical energy due to being so sedentary. The theory throughout the book that people with multiple personalities all start as super-intelligent children was popular at the time.^note This is also sloppy interpretation; Dr. Cornelia Wilbur said she personally had never met a multiple who was not highly intelligent, and that became "all multiples are geniuses" in the popular imagination and even among doctors who should have known better.
• The Zombie Survival Guide 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. As the claim is presented as being purely speculative regarding zombie abilities, it could be a case of an In-Universe error by the author.

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