Perception Filter

""Because they seeing see not; and hearing they hear not.""

- Jesus, Matthew 13:13

""The technology involved in making something properly invisible is so mind-bogglingly complex that 999,999,999 times out of a billion it's simpler just to take the thing away and do without it... The 'Somebody Else's Problem field' is much simpler, more effective, and "can be run for over a hundred years on a single torch battery.""

- Douglas Adams, Life, The Universe and Everything

Your standard invisibility typically makes you transparent to light. While quite effective, it does have a number of catches, since you usually can be heard or otherwise detected. Not to mention that you would be completely blind. So it's actually not a good way of being stealthy.

Perception Filter does not have these catches, because it affects the minds of the observers, making them subconciously look in another direction or pay no attention to the subject, or erasing the subject from short term memory. It typically doesn't work on cameras and other objects that don't have a mind to screw with.

Very often used by witches in Fantasy. Power to avert everybody's eyes apparently is a must for them.

See also: Weirdness Censor, Invisible to Normals, The Nondescript. Compare Jedi Mind Trick.

Anime and Manga

 * Popped up, of all places, in a Mahjong game... specifically, in the anime Saki. Touyoko Momoko, the 'star player' of Tsuruga Academy, has a special ability to 'disappear' by blending into the background. Depending on how attentive her opponents are, it may take her a while to disappear, but once she does, the rest of the players at the table simply ignore her, as well as her discarded tiles - allowing her to pull off some truly insidious gambits. It doesn't work on Nodoka once she's in the zone - she's just seeing the entire table like a PC-monitor, and there's no room for tricks like that in Online Mahjong.
 * People notice Kagero Usui from Sayonara, Zetsubou-sensei only when his balding head is exposed. The reason is never explained.
 * The power "dummy check" in To Aru Majutsu no Index prevents people from being noticed.
 * In Ghost in the Shell, sufficently skilled hackers can essentially edit themselves out of people's vision, this trick is used in Stand Alone Complex by the Laughing Man.
 * In Mahou Sensei Negima,.
 * The villain of the sixth Karano Kyoukai movie, "God's Word", is able to use the Language of Magic to plant perfect suggestions into people's heads, such as "you will lose track of me", which makes it impossible to locate him for anyone who hears it even if he stands right next to them. This way,.
 * Eyeshield 21. One of the players for the Devil Bats, Ishimaru, is so plain that he's practically invisible, even on the field.

Comic Books

 * In an Archie Comics story, Jughead justifies his drab, downbeat style of dress to Veronica by showing her that it renders him de facto invisible to teachers, canvassers for charity, and such, in contrast to her bold, stylish fashions. At the end of the story, an impressed Veronica likewise starts dressing not to be seen.
 * The Shadow is one of the best-known examples.
 * In The Ballad of Halo Jones, Glyph had their sex changed so often they ended up with a gender-neutral body and this ability. While they find it much easier to get whatever they want (being able to bypass a checkout counter and so on), they are very lonely since they can't turn off this 'power'.
 * One of the people who was Doctor Fate for a while, Inza Nelson, would switch between her civilian identity and Doctor Fate right in front of people, and got away with it by mind-controlling everyone in the area for a split second to not notice.

Fan Fiction

 * It's used to explain how the Celebrity Paradox can exist in A Time To Kill. The Tenth Doctor tells Donna that "the combination of sounds, vowels, consonants, cadence" in James Bond's standard introduction ("Bond James Bond.") acts as an audio perception filter, meaning that Bond can introduce himself to people and they won't remember details about him, including the fact that he's the living embodiment of what should be a fictional character. Then, to demonstrate, the Doctor uses the line on Donna, and she instantly forgets everything he told her about Bond.

Film

 * The Jimeoin film The Extra has him using this in the climax.
 * In Bram Stokers Dracula, Gary Oldman is having his way with Lucy and as Mina comes down, he murmurs, "No. Do not see me." And she doesn't.
 * The Red Leptons in Buckaroo Banzai don't wear disguises to look human, they simply use a hypnosis device to be perceived as human.

Literature

 * Invoked in one of Father Brown books. Nobody takes this explanation seriously.
 * Another variant, fully realistic and closer to Hidden in Plain Sight, appears in an aptly-named Invisible Man.
 * The Others in Night Watch use a variety: people don't just avert their eyes, they step aside instinctively.
 * They also use it for their property. That is why no Other has to worry about their car being stolen. If humans simply thought the car wasn't there, they try to park in that spot. This way, they don't perceive the car but also keep on driving. When Anton has to avoid using his powers in order to appear human, he suddenly has to be worried about leaving his car in a "bad neighborhood".
 * Vampires (one of the weakest Other groups) experience Glamour Failure if a human looks in a mirror. The vampire would be visible in the mirror but not in direct line-of-sight. It is unknown if it's the same for other groups.
 * In the Circle of Magic book Magic Steps, the kid Pasco develops the ability through his magic. Uses it to sneak around.
 * Dina and her father from The Shamer Chronicles can make it so that others don't notice them.
 * The Temps short story "Nothing Special" by Brian Stableford uses it for social commentry; the main character is a British paranorm of Asian origin, and we only get told what his power is in the last sentence - the rest of the story continually describes him as being ignored, but the reader doesn't make the connection.
 * In the Lord Darcy books "invisibility" means that people just instinctively avoid looking where you are. They can still see you in a mirror, though. In one of the books a character asks "suppose they made the mirror invisible as well?" and is told they could, but you have to look somewhere, and the more places your eyes slide away from, the more likely you are to become suspicious.
 * As well as Discworld witches, who get covered above under fantasy, Susan Sto Helit can "fade into the foreground". This seems to be a theme in Discworld: Pratchett maintains that if something is utterly outlandish and impossible enough (for example, a donkey standing on top of a very very high pole), humans will go out of their way to not notice it or subconsciously pretend it doesn't exist. Animals, who do not have the advanced mental perception filters humans have that enable them to see exactly what isn't there and not see what is, do not fall under the blanket of this trope.
 * Discworld loves this -- Death himself uses it to go unnoticed, though it may be a case of outright Weirdness Censor.
 * While still a student Lord Vetinari practiced standing so still that no one saw him. It worked.
 * The SEP field in The Hitchhiker's Guide to the Galaxy works like this.
 * The concept is parodied in Ravenous Bugblatter Beast of Traal from the Hitchhiker's Guide to the Galaxy. It's an animal that is so mind-bogglingly stupid that it assumes that if you can't see it, it can't see you.
 * In David Eddings Sparhawk series of books, there are several different approaches to invisibility. The one most frequently seen, used by the Child-Goddess Aphrael (also known as 'The Nimble Goddess' or 'That damn sneaky thief that you just can't hate even though she just robbed you blind 'cuz her smile is so cute'), is basically this - she magically diverts people's attention, so they sorta' know you're there, but they don't pay attention to you. They'll even step out of the way to let you past, without noticing that they're doing it.
 * The same is used briefly in the Belgariad, to make Garion's giant sword a bit less conspicuous. In the Malloreon, one is applied to a book of prophecy to keep unauthorized people from reading a certain passage. All the passages are clearly written and intact in every copy of the prophecies, simply written on an area of parchment the size of one letter.
 * Then we also have the young boy and insanely clever budding thief, Gher in the Redemption of Althalus who can 'dodge' telepathic powers such as those from one of the companions, Leitha. As he describes it, he can tell where a telepath is aiming his or her mental "ears" and just "steps out of the way".
 * In Star Wars Expanded Universe, while usually Jedi Mind Trick is utilized instead, some species can rather "hide their presence in the Force".
 * A witch in His Dark Materials does this with magic. Will Parry is also implied to be able to do something like this.
 * Magic-users in Diana Wynne Jones's Deep Secret can put "don't-notice" workings on objects, though it works only as a weak Weirdness Censor.
 * Harry Dresden, the protagonist of Jim Butcher's The Dresden Files novels, attempts to create a potion of invisibility. It's quite possible for him to become truly invisible with such a potion, but the ingredients are too costly. Instead, he cheats by using the effects of this trope. The potion causes those around him to avoid paying any real attention to him and act as though he were not there.
 * This actually turns out to be a problem when he wants to get an Innocent Bystander's attention to warn them about a rampaging werewolf, but they keep on forgetting he's there while he's still in front of their faces. Presumably, if he'd sprung for the invisibility potion, they never would have seen him but would have listened to a warning just fine.
 * In Barbara Hambly's vampire novels, starting with Those Who Hunt the Night, vampires who seem to appear and disappear are really doing this.
 * In the October Daye series, the faerie have a spell that Toby refers to as a "Don't Look Here". It's good enough that people driving cars avoid the user without ever realizing the spellcaster is there.
 * Elizabeth Bear's Promethean Age books have the "pass-unseen" spell.
 * The protagonist of Nnedi Okorafor's Who Fears Death uses this trick to infiltrate an enemy town. She called it "going ignorable."
 * Daniel Suarez' FreedomTM uses a technological version that only works on digital cameras (see: Ring of Aggys.)
 * William Gibson's Zero History also does the technological variant (see: Ugly T-Shirt)
 * Early in The Dragon Knight series, Jim magically invokes this several times as an economic substitute for true invisibility.
 * The aliens from Peter Watts' Blindsight use a hard-scifi version. They detect the saccadic flickering of human eyes and only move in-between the flickers. On the one hand, it only works on a single observer. On the other hand, it is extremely effective against a single observer.
 * The Kurii on Gor have a very ancient invisibility ring that can't be duplicated because they lost the technology, which causes light to bend around the wearer. It has the side effect of making the user see in the red color of the specturm.
 * The Science Fiction novel A Gift from Earth by Larry Niven features a protagonist with a form of invisibility. He has a Psychic Powers that allows him to force others not to notice him. His unconscious use of this power when he's nervous makes his social life awkward, but it is quite useful for other things. The limitations are that he has to be looking someone in the eyes for it to work, but when it happens they will literally forget he was even there.
 * Note that this power can't protect him from mechanical surveillance (in contrast with Invisible Boy from Mystery Men, he is invisible only when people are looking at him and only to people who are looking at him).
 * Unlike many other forms of invisibility that actually render the user transparent, this form can extend to clothing, items carried, and even other people standing near him since it operates by creating a "psychic blind spot" that causes whoever it's affecting to simply not notice anything there.
 * And at one point in the novel
 * It eventually became listed among the "officially recognized" psychic powers in Niven's "Known Universe" and was named "Plateau Eyes," based on the fact that the original novel was set on the colony world, Plateau.
 * In J. K. Rowling's Harry Potter, the Knight Bus seems to work the same way as Hitchhiker's Guide's Somebody Else's Problem Field.
 * As does The Leaky Cauldron and the door to St Mungos (when it's not disguised as an abandoned department store) and presumably most wizarding establishments.
 * It's stated in GoF that the Wizards have spells that make Muggles remember stuff they had to do when they enter the AoE of the spell.
 * In the Wheel of Time books Grey Men are people who have given their souls to the Dark One, and as a result always blend into their surroundings. They are used as assassins in public areas, quite capable of walking right up to someone and stabbing them without ever being noticed. They are quite cleverly dealt with in the textual medium by casual insertion into a descriptive passage, so that the reader is likely to ignore them as well as the characters.

Live Action TV
"It just shifts your perception a tiny little bit. Doesn't make us invisible, just unnoticed. Oh, I know what it's like! It's like when you fancy someone and they don’t even know you exist.
 * In Doctor Who this is called a "Perception Filter". It's used to explain why the TARDIS can go unnoticed even though it's mode-locked in its anachronistic police box form (with some help from humanity's natural Weirdness Censor, of course). A number of other objects have had this applied to them, such as the pavement-stone-lift used by Torchwood's Cardiff branch.
 * The Chameleon Arch, a Gadget Watch a Time Lord can store their consciousness in, has one to prevent the newly-created disguise personality from opening it. They'll keep it with them, but will assume it's broken unless their attention is specifically drawn to it.
 * In the 2007 finale, the Doctor extends the effect to the TARDIS keys he and his companions carry, allowing them to avoid detection after Mr Saxon has them declared public enemies.

[cut to longing looks from both Martha and Jack]"


 * In "The Vampires of Venice", the titular vampires only look human due to a complicated perception filter disguising their true form (though it doesn't hide the teeth).
 * It's possible to beat the perception filter with sufficient training. The Master reveals that he can detect people using filters. Also, Suzie in the Torchwood episode "Everything Changes" reveals that she has trained herself to resist the "invisible lift's" perception filter.
 * In Dark Angel one man turns out to be a genetically engineered precog with a "stealth frame". People avoid eye contact with him and willfully forget that he's there.
 * An episode of Captain America used a gadget created by the Red Skull, which emitted high-frequency sound-waves to make mooks invisible to people.
 * A villain in The X-Files episode "Unrequited" could make a blind spot appear in the middle of people's eyes and hide in it: People could see everything around it, but when trying to look directly at him, didn't see anything and their brain extrapolated the world without him.
 * In Misfits this is Simon's power. When it's active, his power goes so far as to make observers perceive doors as remaining closed when he opens them.
 * The invisibility spray in an episode of Get Smart is described as working this way.

Tabletop RPG

 * In both Vampire: The Masquerade and Vampire: The Requiem, the vampiric power Obfuscate works this way.
 * Legend of the Five Rings has an Air Spell that does this.
 * Advanced Tabletop Game/Dungeons&Dragons: Apart from psionic invisibility, which is, obviously, a Jedi Mind Trick, regular Invisibility is an illusion spell, so it affects the visual perception of the observers so they won't see the invisible target.
 * In Mage: The Ascension, Mages can buy this ability as the background "Arcane", which means people tend to forget them right away after seeing them.
 * In Rifts and the other Palladium game, this is extraordinarily frequent. Just like the real ninjutsu example below, ninjas in Ninjas & Superspies and Rifts have the ability to cloud the minds of others with chi as well as use numerous arts of invisibility that combine prowling and sneaking with misdirection and manipulation of human psychology. Psychics can use Invisible Haze, which is similar.

Videogames

 * One character in Zeno Clash uses a very creative variety of this trope: he wants to be invisible. Being invisible means there's nobody who can see him... so he tears out the eyes of every living creature he finds.
 * In Second Sight the "charm" ability works by making the people around you not consider you a threat. This also means it can be used to calm down allies (useful when escort ) but it won't work on machines (like security cameras and metal detectors) and attempting to use it when a hostile NPC can see you causes their anger to burn out your powers. From a programming point of view it also allows the developers to leave the NPCs reaction animations unchanged (enemies just act like friendly NPC when you walk past them).
 * The Jedi Knight games use this as the basic effect for Force Persuade/Jedi Mind Trick (depending on which entry you're playing); you're still visible, you just "persuade" the Mooks that you're not really there. Overlaps with Jedi Mind Trick.
 * Koishi Komeiji of Touhou Project uses her power over the subconscious mind in this way to move about unnoticed by others.
 * The Stone Mask in The Legend of Zelda: Majora's Mask has this effect, making the player "inconspicuous as a stone." Link can't see an NPC wearing the mask without the help of the Lens of Truth.
 * The aliens in X-COM: UFO Defence and Terror From the Deep are able to locate X-Com bases by detecting brain waves (UFO) and using Molecular Control-based sensors (TFTD). The Mind Shield/M.C. Generator facilities can prevent UFOs from finding a base by jamming their sensors.

Web Original

 * The gamma in Shadow Unit Season 1 Episode 7 "Overkill" had this as a superpower.
 * This is one of the Slender Man's powers. Unless he's targeting them directly, people don't notice him at all. If they happened to have a camera with them, they will promptly shit bricks when they watch the footage.

Real Life

 * Ninjitsu. Yes, there is real life ninjutsu, it is not magic, and it actually works has a whole class of techniques for doing this, based on human psychology and perception, it boils down to blending in with the background. Documented ninjitsu lessons even cover such things as how to hide in the middle of an open field (it involves crouching into a non-human shape, so someone at a distance will just see a blob and think it's a bale of hay or whatever).
 * Spies are trained that way to sneak around, avoiding being chased, et cetera, often by means of being The Nondescript.
 * When little children play hide-and-seek, one child can close his eyes, and nobody will notice him. When a child's mind have not developed yet, they think that if they don't possess a piece of knowledge, nobody else does.
 * Peekaboo is based on the fact that child (now a toddler) does not know that something can exist without them observing it.
 * Knowing that things exist even if you can't observe it is called Object Permanence - maybe Perception Filters override this logic.
 * Stage magicians, clowns, fortunetellers, and similar performers are actually trained to do exactly this. It again boils down to tricks on human psychology really.
 * It is amazing how some of the players in this video manage to escape the viewer's attention while passing the ball by using feints and whatnot. Can you count how many times do they do it?
 * Derren Brown played this trick on a film student in this video. All he does is speak a bunch of nonsense, then add "You just simply don't see me". Then he intentionally plays out a scene from the old The Invisible Man film. The camera focuses on the student's face a lot, and you can see how his vision is deliberately unfocused, as if he can't help it, and how freaked out he is when Derren picks up a doll, as if the doll is moving on its own.