->''"Keep absolutely still. [[TyrannosaurusRex Its]] vision's based on movement."''
-->-- '''Dr. Grant''', ''Film/JurassicPark''

A Living Motion Detector is a person, monster, or robot that can only detect you if you're moving. Depending on its level of intelligence, it may forget about you when you stand still, or it may go looking for you. A common tactic in combating one is to somehow make objects around you move while you yourself stay still, causing it to attack the moving object instead of you.

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!!Examples

[[AC:{{Anime}} and {{Manga}}]]
* Notorious B.I.G., a Stand in ''Manga/JoJosBizarreAdventure: Golden Wind'', has this trait. Trisha managed to confuse it by using her Stand to shake the chairs on the train she was riding, leading it to attack them instead.
** [[spoiler:Dio's raptor form]] in Steel Ball Run
* In explaining why [[OurZombiesAreDifferent their zombies are different]], ''HighSchoolOfTheDead'' posits that, since the brain and the optical nerves are dead, zombies detect through vibrations instead of visual signifiers. This can be useful for distracting zombies, as a wet cloth thrown against a locker will cause a horde to turn away from the human standing right in front of them.

[[AC:{{Film}}]]
* A variant in ''Film/PitchBlack'', in that the monster can't see you if you stand between its eyes, because of a blind spot caused by their armored heads.
* The underground Graboids in ''Film/{{Tremors}}'' can only detect you by the vibrations caused by your movements.
* In a variant, the Blind Dead from the Spanish film series of the same name can only track you down if you make a sound. Staying still helps. It can't save you forever, however -- [[spoiler:they can hear your heart beating.]]
* ''Film/TheDeadlySpawn'' has very toothy grinning aliens who are blind but hunt by sound. Be very quiet and it won't notice you.
* Invoked in ''Film/TheUglyDachund'', where Mr. Toyama plays dead after he mistakes [[CanisMajor Brutus]] for a lion.
* The T-Rex from ''Film/JurassicPark'' has "vision based on movement".

[[AC:{{Literature}}]]
* The Tyrannosaurs in ''Literature/JurassicPark'' is thought to be one. This is a side effect of its frog DNA (frogs really can't see prey if it doesn't move).
** In [[Literature/TheLostWorld1995 the second novel]], it was explained that T-Rexes could see things that were standing still perfectly well, as one man fatally found out. The T-Rex in the first book had just been ignoring the humans because it wasn't hungry.
* Hunter-seeker drones in ''Literature/{{Dune}}'' fly towards anything that moves, killing on contact.
* In PiersAnthony's On a Pale Horse (IncarnationsOfImmortality #1), Zane faces off against a demon that looks like a 5 meter tall preying mantis. He realizes that it can only perceive him as prey if he moves. (And he can even do that as long as he doesn't move in a way that resembles the motion of prey.)
* The dragons in the ''[[Literature/TheSteerswoman Steerswoman]]'' books, [[spoiler:which are actually robots]].
* In Literature/ShadowsForSilenceInTheForestsOfHell, moving too fast will draw the attention of the shades. If their eyes are closed, you can move slowly and they won't notice you. If their eyes are green, then holding perfectly still may cause them to lose interest and close their eyes again. If their eyes are red, you'd better run, because only getting behind silver will save you.

[[AC:LiveActionTV]]
* ''Series/{{Angel}}'':
** The assassin in "Blind Date" is blind but has learned to detect "other parts of the electromagnetic spectrum." The net result is that she's a human example of this trope, at least when she's fighting someone like Angel who doesn't generate body heat.
** Also:
--->'''[[ProudWarriorRaceGuy The Groosalugg]]''': I once happened upon a herd of Bur-beasts and as you know, engorged Bur-beasts will couple with AnythingThatMoves. I was forced to stand perfectly still for eleven days and nights.
* The Raston warrior robot from the ''Series/DoctorWho'' episode "The Five Doctors."
* The monster Silvagon of Ultraman Tiga could only see movement, leading to a hilarious scene where Ultraman strikes at it, then freezes up as soon as it turns to face him. This gets especially silly when he's forced to hold a precarious crane stance. Eventually Silvagon gets fed up and starts blindly running around, lashing at the air.

[[AC:TabletopGames]]
* ''TabletopGame/DungeonsAndDragons'' has a shrieker, a giant underground mushroom that reacts to light or movement. Its sole purpose is to alert and attract monsters
* In ''TabletopGame/{{Warhammer 40000}}'', according to the 5th edition Tyranid Codex, it was, until recently, believed that Raveners couldn't see anything that wasn't in motion. It was later proved that they can see stationary objects (and people) just fine; they are compelled to chase opponents, when a biologist studying them ordered his men to remain still when attacked by them.

[[AC:VideoGames]]
* One of the boss creatures in ''VideoGame/HalfLife1'' was a massive but completely blind tentacle that detected you by your footsteps. You could either crawl past silently, or set off an explosion and run past while it struck at the louder noise.
* Similarly, Los Garradors in ''VideoGame/ResidentEvil4'' are blind and hear your movement if you're running, as well as your [[EscortMission commands to Ashley]]. Sadly for them, you fight them in the vicinity of bells - one strategy for defeating them involves shooting the bell and then shooting its weak point (ForMassiveDamage) while it's distracted. Another is simply walking, which they can't hear.
* One of the enemies in ''Yoshi's Island'' is Boo Man Bluff, a blindfolded Boo that homes in on Yoshi whenever the cute little dinosaur makes a sound. That includes jumping, throwing eggs, or even touching coins; the ghosts have good enough hearing to hear the obligatory video game blips and beeps. To add to the fun, the ghost can only home in on the place where you last made the sound, and looks quite clueless and confused when you aren't there. The blind Boos also appear in ''SuperPrincessPeach''.
* The Berserker from the first GearsOfWar was blind, but could detect where you were through your footsteps, as well as your smell.
* The Witch from ''VideoGame/Left4Dead'' doesn't seem to care about you until a) get really close, b) make a ton of noise in her direction or c) blind her with your flashlight. Then she gets pissed, and it's LosingYourHead time!
* The Lickers in ''VideoGame/ResidentEvil2'' and ''VideoGame/ResidentEvil5''.
* ''VideoGame/FalloutNewVegas'' has Blind Deathclaws, which have high perception despite their blindness, and which will alert other Deathclaws when they detect you.
* ''VideoGame/DeepSleepTrilogy'' has the bottom feeders, who will devour you if you move the mouse too far too fast.

[[AC:WebOriginal]]
* The Kua-Toa of ''WebVideo/TalesFromMyDDCampaign'' can see invisible things only if those invisible things are moving.

[[AC:WebComics]]
* The "Fun-sized mobile agony and death dispenser" clank in [[http://www.girlgeniusonline.com/comic.php?date=20080908 this]] ''Webcomic/GirlGenius'' comic reacts to movement, including that of one's lips and chin.

[[AC:WesternAnimation]]
* Poked fun at in ''WesternAnimation/FamilyGuy'' where Peter and Lois encounter a prostitute who sees by movement.
* WesternAnimation/PhineasAndFerb and Candace travel back in time and encounter a T-Rex, Phineas advises this technique and admits his surprise that it actually works.
* ''WesternAnimation/AvatarTheLastAirbender'': Toph Bei Fong is blind from birth, but this, by forcing her to rely on her other senses, has resulted in her earthbending abilities being so developed that [[DisabilitySuperpower she can sense every movement and position of every person and object around her]], so long as it's standing on earth, metal or stone. By sensing a person's heartbeat and physical reactions she can also tell [[LivingLieDetector whether or not they're lying]].
* Parodied on ''WesternAnimation/TheAmazingWorldOfGumball'', when Gumball and Darwin try it on Tina. Tina responds with "That only works in movies."
* In an episode of ''WesternAnimation/TheAdventuresOfJimmyNeutron'', when Jimmy, Carl, and Sheen accidentally travel back to prehistoric times, Carl is attacked by a T-Rex and Sheen tells him not to move, only for Jimmy to tell him that theory has been discredited, so Sheen tells Carl to run.

[[AC:RealLife]]
* This is TruthInTelevision for some animals.
** Frogs are extremely near-sighted, but capable of detecting movement at a distance.
** Many insects. The compound eyes present in many species are awful at making out detail, but excellent at detecting even minute movement.
** As well as many fish.
* Dogs are visually more attuned to motion than color.
* Some strains of the Siamese cat have poor eyesight due to genetic problems. These cats react better to motion than stationary scenes or objects as a result. Some will move ''their'' heads to produce the necessary movement in their field of view so that they can determine where everything is.
* While many people think that [[BullSeeingRed bulls hate red,]] they're actually enraged by the motion of the cloth, not the color.

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