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These are the user uploaded subtitles that are being translated: {164}{243}NARRATOR: Too often, | we take our bodies for granted, {248}{313}but under pressure, | our bodies can show us {318}{412}how extraordinary | they truly are. {432}{485}This complex machine grew {490}{575}out of millions of years | of evolution. {580}{647}So intricate, | we're still mystified {652}{732}by many of the things | going on inside us. {737}{773}A hidden world, {778}{916}but one we can now explore | in 3-D as never before. {921}{1044}Our sight relies on the most | complex system in our bodies. {1084}{1154}Using three-quarters | of our brain power' {1159}{1188}when we're challenged, {1193}{1297}our eyes focus on the smallest | detail at lightning speed. {1385}{1449}They allow us to see | in the dark' {1454}{1520}even to see to the magic | of the impossible. {1546}{1652}Our brain allows us to see | even while we sleep. {1669}{1795}And someday, we may be able | to see without our eyes. {1814}{1917}That's how extraordinary | our sight truly is {1922}{1987}when we're pushed to the limits. {2067}{2152}[ Siren wailing ] {2157}{2239}[ l ndistinct talking on radio ] {2244}{2354}A murder suspect races | through downtown Los Angeles. {2359}{2412}[ Tires screeching ] {2653}{2755}Pursuing him is LAPD officer | Stan Berry. {2790}{2876}What he's got to do | in this superfast world {2881}{2958}is to figure out what matters | and what doesn't {2963}{3011}at 1 00 miles an hour. {3016}{3073}MAN: 1 4, there's two occupants | in the car. {3101}{3141}[ Horn blares ] {3146}{3256}NARRATOR: And to keep up with | the suspect without crashing. {3305}{3373}BERRY: l need to know about | the traffic to the right of me, {3378}{3442}traffic coming | to the left of me. {3447}{3513}But you also need to focus | on what's ahead of you. {3518}{3586}ls there pedestrians | walking down the street? {3625}{3669}And then also try to keep up {3674}{3758}with the fleeing suspect' | as well. {3812}{3892}NARRATOR: Nature designed the | eyes to let him do just that. {3985}{4072}Sight guides the human body. {4077}{4114}[ Tires screeching ] {4119}{4207}[ Siren wailing ] {4271}{4328}2- 1 -900, l am west... {4333}{4406}NARRATOR: Many animals | have special kinds of vision. {4411}{4495}But in humans, we can do it all. {4567}{4627}Like no other creature on Earth, {4632}{4732}our vision can distinguish | around 1 0 million colors... {4737}{4802}[ Horn blaring ] {4807}{4865}...switch focus from infinity {4870}{4934}to mere inches | in a fifth of a second... {5000}{5096}... pinpoint detail | in the brightest sunshine {5101}{5146}or darkest shadow... {5203}{5324}...take in a wide-angle view | of almost 1 80 degrees. {5329}{5450}All of this takes the massive | power of the human brain. {5555}{5627}70% of the neurons in the brain {5632}{5707}in some way subserve | the visual system. {5724}{5819}lt's been given | an extraordinarily high degree {5824}{5849}of emphasis {5854}{5961}by all the mechanisms that | have gone into its creation. {5966}{6027}[ l ndistinct talking on radio ] {6032}{6119}NARRATOR: Human eyes function | as survival sensors, {6124}{6202}giving us essential information | at the crucial time. {6336}{6410}Berry constantly relies on them. {6462}{6584}The eyes' mechanics are | the most complex in the body. {6589}{6655}Their intricacy is unmatched. {6717}{6820}As a ball, the eye pivots | in all directions, {6825}{6890}locking onto moving targets. {6962}{7052}lt does so with the help | of unlikely allies -- {7057}{7172}two cups of fat -- shock | absorbers for the eyeballs. {7232}{7308}Light enters through an aperture | in the iris, {7313}{7403}an elastic mesh | of interlocking fibers. {7431}{7529}l n bright light' it snaps down | to the size of a pinhole {7534}{7582}in a fifth of a second. {7635}{7679}Light hits the lens -- {7684}{7771}not a hard disk' | but a bag of fluid. {7805}{7906}The lens projects an image the | size of a large postage stamp {7911}{7973}onto the retina | at the back of the eye. {8012}{8113}Then the retina' | a mass of nerves, {8118}{8175}sends impulses to the brain. {8180}{8231}Surprisingly, the right eye {8236}{8291}signals the left side | of the brain, {8296}{8376}and the left eye transmits | to the right side. {8451}{8522}Our eyes have evolved | a crucial feature {8527}{8600}that still keeps us | from going extinct. {8658}{8709}20 minutes into his chase, {8714}{8829}Officer Berry is about to test | that feature to its limits. {8880}{8928}Speeding into a dangerous | intersection, {8933}{9040}he faces questions literally | involving life or death. {9076}{9136}[ Engine revving ] {9141}{9203}ls anything moving? {9208}{9260}Where is it? {9262}{9299}What is it? {9304}{9382}[ Siren wailing ] {9387}{9470}A vehicle is stopped ahead, | blocking the way. {9503}{9612}To the right' a car speeds | toward the intersection. {9617}{9709}On the left' | a third driver about to move. {9941}{9972}[ Horn blares ] {9977}{10057}But suddenly, | something else comes into view. {10157}{10272}And here's where | the human eye's design pays off. {10301}{10345}At the back of the eye, {10350}{10462}most of the retina consists | of millions of rods. {10467}{10565}These cells see no color | or detail. {10570}{10680}But let anything anywhere | in our field of view move, {10685}{10731}and the rods spot it. {10819}{10922}The eyes swivel | to look directly at the vehicle. {10980}{11065}Now other cells at mid-retina | kick in. {11131}{11281}A pinhead-sized dot holds | six million cells called cones. {11296}{11382}They're all about color | and detail. {11387}{11442}DR. D'AM l CO: That's why, | when we look at something, {11447}{11486}we look directly at it -- {11491}{11559}because we have | our highest visual acuity {11564}{11617}right in the center. {11622}{11681}NARRATOR: Locking his eyes | on the moving object' {11686}{11801}Officer Berry can judge speed, | direction, and danger. {11836}{11875}The brain responds, {11880}{11998}sending signals | at an amazing 1 80 miles per hour {12003}{12093}to his hands and feet in time | to clear the intersection. {12144}{12189}[ Horn blares ] {12194}{12287}[ Siren wailing ] {12292}{12363}This is one of hundreds | of life-or-death decisions {12368}{12403}that Officer Berry makes {12408}{12483}to bring the 40-minute chase | to a safe end. {12530}{12603}[ l ndistinct talking on radio ] {12608}{12730}He does this thanks to the eye's | incredible skill at adjusting {12735}{12835}when information threatens | to overload what we're seeing. {12897}{12968}This ability matters | as much today {12973}{13047}as it did for our ancestors. {13087}{13167}Evolution left us | with another skill, {13172}{13241}one that's still priceless. {13335}{13404}l n the dark' | we can make out the world {13409}{13483}with only the smallest | of clues. {13584}{13676}The will to live through a fire | depends on our skill {13681}{13798}at navigating the murderous | darkness of smoke-filled rooms. {13803}{13904}Firefighters reach a house | in Bradenton, Florida. {13909}{13951}Agent 56, go ahead | and charge the line. {13956}{14039}NARRATOR: But they don't know | if anyone's trapped inside. {14085}{14113}l'm set. {14118}{14157}Ready? {14251}{14305}NARRATOR: | Now firefighter Dan Fleming {14310}{14398}enters a dangerous world | of shadows and shapes... {14447}{14490}...so murky and cloudy, {14495}{14577}you'd think it impossible | to see anything. {14756}{14838}Dan struggles to build a picture | of the whole house {14843}{14909}from frag ments he makes out | in the haze. {14935}{14997}[ Heavy breathing ] {15002}{15059}How is the house laid out? {15083}{15139}Where is the fire? {15166}{15232}Are there any survivors? {15273}{15379}You're trying to determine | what the house looks like, {15384}{15492}what the occupants are about' | who would be inside this home. {15669}{15715}NARRATOR: | Despite the darkness, {15720}{15803}Dan's eyes im mediately start | to adjust. {15896}{15958}They have amazing sensitivity. {15975}{16065}l n complete darkness, | from 1 4 miles away, {16070}{16171}we can detect the light | from a single candle. {16176}{16265}You try to find bits and pieces | of light {16270}{16318}to help you | find your way through. {16323}{16408}[ l ndistinct talking on radio ] {16630}{16709}NARRATOR: l n low light' | we rely on the rod cells {16714}{16780}that cover most of the retina. {16785}{16887}Highly sensitive, they only | register black and white. {16938}{16996}But Dan needs to see in color. {17001}{17056}He's searching for a fire. {17160}{17243}FLEM l NG: | lt was very faint at first. {17272}{17372}l thought to myself' "That must | be the seat of the fire." {17377}{17469}very orange glow -- | l mean, it was really orange. {17564}{17614}NARRATOR: | To see color' {17619}{17696}you use cone cells | at the retina's center. {17864}{17917}We get all our color vision {17922}{18030}from being able to distinguish | only three colors. {18035}{18104}SADU N: The cones are sensitive | to different colors. {18109}{18161}There's those that are | particularly sensitive {18166}{18262}to blue light' those to green | light' and those to red light. {18267}{18327}And they need a lot more light | to fire. {18332}{18429}So if they get enough of | the photons of the right color' {18434}{18480}they fire and say to you, {18485}{18574}"There's a spot of green | or red or blue at this point." {18615}{18716}NARRATOR: Using these red, | blue, and green signals, {18721}{18773}the brain creates an impression {18778}{18855}spanning the entire | visual spectrum... {18886}{18965}...a range | of over 1 0 million colors. {19384}{19439}[ l ndistinct talking on radio ] {19444}{19557}Color vision leads Dan | straight to the fire. {19825}{19919}FLEM l NG: To my surprise, | it went out very quickly. {19924}{20008}And l started scanning around to | see what else was in that room. {20040}{20141}Whenever you can get glimpses, | that's so important' {20146}{20244}but l'm taking the whole room in | as l'm scanning. {20331}{20371}NARRATOR: | l n a flash, {20376}{20459}Dan's brain calculates | what has to be there, {20464}{20564}even though he sees | only tiny frag ments. {20625}{20718}This is what our brains do | constantly -- {20723}{20829}fill gaps with data | from our visual memory bank. {20907}{20990}l n fact' our brain interprets | most of our vision {20995}{21078}out of a lifetime | of stored images. {21232}{21289}Then Dan recognizes something. {21294}{21388}A white shape -- | a cup of coffee. {21523}{21654}Black and white squares -- | a half-completed crossword. {21789}{21840}Are these crucial signs {21845}{21923}that someone could still be | in the house? {21945}{22005}There, through the smoke, {22010}{22135}Dan sees a blurred | and unusual shape. {22202}{22280}FLEM l NG: My initial instinct was | there's something on the couch. {22285}{22336}l'm not sure what it was. {22418}{22458}Requesting backup! {22486}{22524}We have a saying -- {22529}{22608}When in doubt' check it out' | and that's what l did. {22613}{22694}Give me a hand! | l got a victim! {22699}{22747}Get the gurney in here, guys. {22752}{22833}NARRATOR: Dan Fleming has used | his brain's visual memory {22838}{22947}to transform a blur | into the outline of a body, {22952}{23006}saving a man's life. {23086}{23136}The power of human sight {23141}{23225}comes from millions of years | of evolution. {23248}{23300}We can't even understand it. {23323}{23429}And technology today can't begin | to match the sophistication {23434}{23501}of our incredible eyes. {23654}{23691}But for the first time, {23696}{23799}science is pushing human vision | to new limits {23804}{23923}by connecting directly | with the brain's vision center. {23928}{23989}This means that one day, | we might even see {23994}{24113}in the invisible worlds | of infrared, have X-ray vision, {24118}{24207}or plug video games | straight into the brain. {24302}{24359}Cheri Robertson from Missouri {24364}{24456}is about to step | into this virtual world. {24575}{24656}l was in a car accident | when l was 1 9 years old. {24661}{24712}l was a passenger in the car. {24717}{24802}And the driver fell asleep at | the wheel, and we hit head-on {24807}{24839}with a small truck' {24844}{24942}and both of my eyes | were just destroyed. {25033}{25088}NARRATOR: | Hoping to regain her sight' {25093}{25194}Cheri volunteers | for a pioneering procedure. {25266}{25320}lt involves marrying technology {25325}{25452}to the huge processing power | of the brain's visual cortex. {25571}{25634}lt was a chance for me | to be able to see again {25639}{25729}when the doctors had always told | me l would never see anything. {25804}{25934}NARRATOR: Cheri is about to have | an extraordinary experience. {26016}{26094}Doctors drill through both sides | of her skull, {26099}{26157}exposing her brain. {26209}{26275}Then they implant | two triangular plates, {26280}{26363}each holding | 200 tiny electrodes, {26368}{26463}directly onto Cheri's | visual cortex. {26578}{26638}Finally, the surgeons | string cables {26643}{26740}from the plates to terminals | sticking out of her skull. {26839}{26913}Next' the electrodes run | through a computer {26918}{26982}to a camera | on Cheri's eyeglasses. {27007}{27065}All of this technology | is designed {27070}{27143}to help Cheri regain some sight. {27171}{27249}ROBERTSON: lt was, l guess, | quite a shock for me {27254}{27282}when l felt my head {27287}{27353}and l felt these terminals | sticking out behind my head. {27358}{27470}'Cause l guess | l really wasn't expecting that. {27510}{27581}NARRATOR: But for her to see | what the camera sees, {27586}{27643}many things have to happen. {27648}{27758}And that requires a step | into the unknown. {27784}{27896}Each electrode touches a | different part of Cheri's brain. {27901}{27960}When the system triggers | an electrode, {27965}{28064}she sees a flash somewhere | in her visual field. {28069}{28149}Where, the doctors don't know. {28154}{28193}Now. {28219}{28310}NARRATOR: So they trigger | each electrode one by one {28315}{28412}to learn where in her visual | field Cheri sees flashes. {28417}{28451}MAN: Now. {28456}{28509}ROBERTSON: Oh, wow. | That was right there. {28514}{28555}Okay. {28560}{28611}NARRATOR: | When she sees a flash, {28616}{28726}Cheri points to top, bottom, | left' or right. {28731}{28767}[ Beeping ] {28844}{28962}With every electrode mapped, | the doctors connect the camera' {28967}{29018}making certain that what it sees {29023}{29090}matches the flashes | in Cheri's brain. {29095}{29160}ROBERTSON: | Yeah. Right in the same spot. {29231}{29286}So it works for us. {29336}{29404}NARRATOR: Finally, | with the camera mounted, {29409}{29535}Cheri's mother helps connect the | gear to try the new settings. {29583}{29627}WOMAN: Ready? {29632}{29682}l think my computer | gained weight. {29687}{29724}[ Laughs ] {29809}{29910}NARRATOR: Has technology helped | bring Cheri's sight back? {30029}{30074}Oh! {30096}{30136}Wow! {30180}{30222}Oh, wow. {30227}{30292}[ Laughs ] | Oh, wow. {30309}{30420}When l finally saw my first | light' it took my breath away. {30425}{30474}l could not believe it. {30479}{30530}We knew it worked, {30535}{30608}and that was very, | very thrilling for me. {30613}{30670}Oh, something's lighting me up. {30690}{30785}NARRATOR: | We can't know what Cheri sees. {30790}{30854}But we do know | what she describes. {30925}{31007}Whoa. l'm seeing | two big dots of light. {31012}{31104}And they are white with | a little bit of red in them. {31138}{31250}Wow. Those were two really big | flashes, and they moved. {31275}{31370}Wow. l saw a big flash | of light there. {31405}{31453}NARRATOR: | This early in the project' {31458}{31553}doctors have activated | only some of Cheri's electrodes. {31558}{31643}Eventually, they hope to connect | many more, {31648}{31718}vastly improving the scope | of her vision. {31723}{31758}Oh, wow. {31790}{31885}Because l can only use 1 0 | of my electrodes, {31890}{31973}whenever an object goes | in front of my camera' {31978}{32049}l will see two flashes of light. {32054}{32146}And they're about the size | of a big peanut M&M -- {32151}{32214}just one on top of the other. {32219}{32291}Saw a couple more. | l'm not sure if it's the waves. {32296}{32380}And that way, l know | that there is an object there. {32385}{32453}Now, l'm not sure what it is. {32458}{32513}They're sailboats? {32541}{32596}ls that it still here? {32601}{32653}That is cool. {32674}{32782}When l am able to use | all of my electrodes, however' {32787}{32816}l will be able to see {32821}{32877}the outlines of things | l'm looking at. {32882}{33069}So l'll know if l'm looking | at a tree or a person or a car. {33074}{33165}So l'll actually know | what l'm looking at. {33208}{33306}NARRATOR: No one pretends | that Cheri's vision is back. {33311}{33402}But the fact she can sense | any of the visual world {33407}{33488}makes her | an extraordinary pioneer. {33511}{33611}l magine if one day we could feed | complete vision signals {33616}{33659}directly to the brain. {33664}{33714}What could we see? {33719}{33802}We might see a world | that we've been blind to, {33807}{33897}as if we were seeing | through night-vision lenses, {33902}{34001}infrared cameras, | even X-ray vision. {34089}{34140}l magine a sum mer weekend {34145}{34241}on a California beach | dense with bodies. {34300}{34392}But for one onlooker' | this seemingly calm scene {34397}{34484}may be a series of accidents | waiting to happen. {34595}{34637}How does a lifeguard know {34642}{34704}when a raised arm means, | " l need help "' {34709}{34791}not' "Hey, this is fun"? {35141}{35222}The guard's skill at spotting | that one desperate person {35227}{35306}among thousands is phenomenal, {35311}{35384}truly testing his sight | and understanding. {35618}{35749}We see the way we do so we can | spot danger to ourselves. {35754}{35798}l call! {35803}{35879}NARRATOR: But nothing | is threatening the lifeguard. {35989}{36027}l n fact' the eye, {36032}{36102}observing a harmless pattern | across its view, {36107}{36160}normally relaxes. {36190}{36275}Motion-sensing rod cells | switch off {36280}{36378}when they detect action | that's consistent and constant. {36556}{36635}So the lifeguard | has to trick his eyes. {36711}{36761}He does this by scanning, {36766}{36859}forcing his eyes to lock | onto small details. {36864}{36940}TU RN ER: Our frontline defense | are the tower guards. {36945}{37008}Their job is to scan the water' {37013}{37125}so their eyes are moving | across the water {37130}{37222}and letting their brain filter | out that information they see, {37227}{37268}looking for something wrong, {37273}{37403}looking for that odd one out | that truly is in danger. {37476}{37586}NARRATOR: Taking in all | this information is hard work. {37591}{37712}Human sight has only two degrees | of detail vision at the center. {37790}{37900}To check the whole beach, | the lifeguard sweeps... {37962}{38039}...jumping from point to point | for detail. {38106}{38192}Each jump is called a saccade. {38197}{38309}A saccade is the movement | that the eyes make together {38314}{38370}when they're looking directly | at one thing {38375}{38450}and all of a sudden, | they look at something else. {38455}{38571}We have mechanisms that wire | the muscles that move our eyes {38576}{38609}to the image. {38614}{38721}And we can quickly lock | onto a new image all at once. {38833}{38917}NARRATOR: The saccade function | lets him jump visually {38922}{38990}from each potential risk | to the next. {39006}{39076}He repeatedly scans | his field of vision, {39081}{39175}updating his visual memory | every few seconds. {39180}{39312}But even more is going on as | he uses another complex skill -- {39317}{39365}interpretation of detail. {39370}{39404}KAF ORD: | Being a seasoned lifeguard, {39409}{39499}l can recognize distressed | victims in the water' {39504}{39564}whether they look | really labored, {39569}{39644}whether they're comfortable | or not' by their body language. {39649}{39679}Those are sort of indicators {39684}{39767}that allow you to recognize | a rescue before it happens. {39847}{39905}NARRATOR: | The muscles rotating our eyes {39910}{39981}give us an astounding breadth | of view. {39999}{40057}Even while perfectly still, {40062}{40158}we can rotate our eyes | from far left to far right {40163}{40214}in a quarter of a second. {40327}{40405}So when a riptide | suddenly overcomes a swim mer' {40410}{40486}Drew knows within moments. {40868}{40988}Now he has to judge whether the | swim mer can get back to shore, {40993}{41067}whether he's too far out | for a rescue attempt' {41072}{41140}or whether' despite the riptide, {41145}{41199}Drew has a chance | of reaching him. {41204}{41323}That split-second call demands | an accurate sense of distance. {41375}{41485}We have two eyes, and they're | separated by this distance, {41490}{41546}and that permits each image {41551}{41668}to be slightly different | than the other image. {41673}{41728}And that slight dissimilarity {41733}{41843}gives me a sense | of how far away something is. {42027}{42116}NARRATOR: We constantly judge | shifting distances, {42121}{42197}hardly giving the process | a thought. {42202}{42270}But this special process | only occurs {42275}{42379}in humans and other predators | for spotting and catching prey. {42523}{42583}That's the hunting skill | the lifeguard uses {42588}{42666}to home in | on the struggling swim mer. {42928}{43016}We can all find the detail | we need in a busy scene {43021}{43073}when it's for our own safety. {43128}{43194}But when guarding the lives | of others, {43199}{43345}that same skill requires | training and intense focus. {43382}{43525}l n day-to-day life, we fill in | parts of the passing picture {43530}{43629}as our visual memory | makes shortcuts and assumptions, {43634}{43721}putting together a picture of | the world that seems complete. {43800}{43910}What happens when | those assumptions prove wrong? {43942}{44048}That's where we get the phrase | "smoke and mirrors "' {44053}{44137}the tools of visual confusion | illusionists use {44142}{44249}to exploit the science of sight | to fool our vision. {44463}{44592}Movies present spectacular | sights and grand illusions. {44737}{44837}This is a movie set' | but how big? {44842}{44918}[ Alarm blaring ] {44923}{45036}What looks like a space station | on an alien planet... {45041}{45091}MAN: Cut! {45096}{45145}NARRATOR: | ... is a trick. {45197}{45240}WOMAN: | 68 "B "' take 1. {45300}{45357}NARRATOR: | A tiny model near the camera {45362}{45456}and a full-size stage | further away. {45480}{45571}Film makers are essentially | the masters of illusion. {45588}{45640}Here we see the two actors. {45645}{45697}We assume | they're in a massive set' {45702}{45744}because we don't have | the ability {45749}{45777}to think' "Hold on a second. {45782}{45832}This is just a small set' | and the actors {45837}{45896}are a considerable distance | away from it." {45901}{45939}MAN: Cut! {45944}{46019}visual illusions trip up | the perceptual system, {46024}{46092}the system | that is normally right. {46097}{46155}Here we're exploiting | the loopholes, {46160}{46235}when suddenly, | we're very, very wrong. {46319}{46425}NARRATOR: l llusions exploit | how we see the world. {46493}{46587}They rely on the difference | between what the eye sees {46592}{46675}and what the brain understands. {46680}{46800}Magicians have always relied | on this delicate confusion. {46852}{46875}Hi, there. {46909}{46961}[ Echoing ] | l'm Marco Tempest. {46966}{47024}l'm a magician. {47029}{47126}Now, here's a little | optical illusion. {47131}{47231}Now, let me show you just | how easy it is to fool the eye. {47236}{47314}l have a three-dimensional | object right here. {47319}{47403}And l also have | a two-dimensional object' {47408}{47449}this paper disk. {47454}{47538}Now, if l place | this three-dimensional object {47543}{47603}next to | the two-dimensional object' {47608}{47669}something very strange | is happening. {47674}{47721}Check this out. {47792}{47834}lt looks like {47839}{47931}the two-dimensional object | has become three-dimensional. {47936}{48024}But if we get rid | of the three-dimensional object' {48029}{48090}something else is happening. {48134}{48179}Check this out. {48202}{48244}Do you see? {48249}{48448}The cube now looks like | it's completely two-dimensional. {48596}{48644}All right. | Here we go. {48649}{48760}NARRATOR: From another angle, | the secrets reveal themselves. {48784}{48845}l also have | a two-dimensional object' {48850}{48919}this paper disk right here. {48924}{48958}Now, if l place the... {48963}{49006}NARRATOR: | Underlying the trick {49011}{49080}is a genuine | scientific principle, {49085}{49130}explaining how our brains {49135}{49208}build a three-dimensional | visual world. {49213}{49255}Check this out. {49274}{49363}This is all about | how we read perspective. {49368}{49407}The three-dimensional cube, {49412}{49472}once established as being | three-dimensional, {49477}{49543}stays three-dimensional | in our minds. {49548}{49606}Even when we look | at the taped lines, {49611}{49679}it still looks three-dimensional | to us. {49684}{49812}lt's almost like our eye | fills in the missing information {49817}{49907}and wants the object | to be three-dimensional. {49912}{49949}And that's where l get you. {49954}{49987}All right. {50031}{50132}NARRATOR: Our world is filled | with visual information. {50174}{50284}The brain copes | by creating shortcuts, {50289}{50410}relying on experience to fill | gaps with informed guesswork. {50501}{50549}Light and shadow. {50600}{50696}The size, shape, and distance | of objects. {50786}{50905}We assume the world operates | according to fixed rules. {50964}{51047}But sometimes | we're just plain wrong. {51167}{51251}Take this ordinary-looking room. {51288}{51355}l look to be much, much larger | than Sarah. {51360}{51403}And this isn't camera trickery. {51408}{51478}l nstead, | it's an incredible illusion. {51498}{51555}Because when l'm in this corner' {51560}{51642}Sarah suddenly looks much, | much larger than me. {51647}{51752}Now, in reality, the two of us | are roughly the same size. {51757}{51822}lt's all to do | with the amazing way {51827}{51901}in which this room | has been constructed. {51947}{51999}NARRATOR: | Not regular in shape at all, {52004}{52136}the room has a bizarre geometry | that's disguised as normal. {52225}{52294}We see square rooms so often... {52333}{52441}...we fool ourselves | into thinking this is one, too. {52505}{52597}lt's amazing | how easily our eyes get fooled. {52602}{52786}We see an umbrella' and we | im mediately think of rain. {52791}{52876}But on a beautiful day | like today... {52925}{53057}[ Echoing ]...we don't | really need an umbrella. {53087}{53178}NARRATOR: Magicians exploit more | than our assumptions {53183}{53257}about the objects and spaces | around us. {53297}{53409}You're about to see | what looks like a simple trick. {53414}{53503}But it has a deeper' | more elusive level. {53517}{53595}Welcome to the color-changing | card trick' {53600}{53672}using this blue-back deck | of cards. {53677}{53722}Now, the idea is very simple. {53727}{53793}l'm just going to spread | the cards in front of Sarah {53798}{53904}and ask her to push any card | towards the front of the table. {53940}{53969}SARAH: Okay. {53974}{54092}l'm going to go for | this card here. {54097}{54127}Wl SEMAN: | Excellent. {54132}{54215}Sarah could've chosen | any of the cards in the deck' {54220}{54263}but she selected the one {54268}{54334}which is now laying facedown | on the table. {54339}{54384}l'm going to ask her | to look at the card {54389}{54444}and tell us what it is. {54506}{54598}The card l chose was, in fact' | the 3 of clubs. {54603}{54645}Wl SEMAN: | The 3 of clubs. Excellent. {54650}{54706}That comes back into the deck. {54711}{54811}l'm now going to spread | the cards faceup on the table. {54816}{54855}A click of the fingers, {54860}{54966}and Sarah's card | still has a blue back. {54971}{55012}What's more surprising {55017}{55134}is that all of the other cards | now have red backs. {55139}{55243}And that is the amazing | color-changing card trick. {55285}{55385}NARRATOR: But this trick really | doesn't involve cards at all. {55426}{55467}lt clearly shows {55472}{55533}how the brain picks up | only a tiny bit {55538}{55614}of the available | visual information. {55679}{55748}l n fact' | as the trick was occurring, {55753}{55822}four other color changes | went on. {56020}{56079}Welcome to the color-changing | card trick' {56084}{56154}using this blue-back deck | of cards. {56159}{56286}NARRATOR: As the trick unfolds, | the camera stays on the cards. {56291}{56348}...which is now laying facedown | on the table. {56353}{56403}NARRATOR: | Most of us don't notice changes {56408}{56490}in clothing and background | made off-camera. {56515}{56596}The color-changing card trick | exploits this idea {56601}{56640}that we have a very good idea {56645}{56704}of what's happening | right in front of our eyes. {56709}{56796}l n fact' 90% of that information | we're just not seeing. {56801}{56836}lt doesn't feel like that. {56841}{56882}lt feels like, | as we look around, {56887}{56939}we're perceiving the whole | of the world. {56944}{56979}That's not the case. {56984}{57079}We really are only just focused | on a tiny, tiny area. {57135}{57250}NARRATOR: l llusions are about | more than entertainment. {57255}{57315}They reveal how what we see {57320}{57388}depends on assumptions | our brains make. {57584}{57736}Our eyes and brain collaborate | to make sense of the world. {57774}{57851}But our brains need years | of training {57856}{57926}before they can turn | what our eyes see {57931}{58022}into a meaningful image | in an instant. {58170}{58301}F ollow a blind man as he uses | his eyes for the first time, {58306}{58408}and hear him describe | what his brain can see. {58597}{58683}Michael May has undergone | radical surgery {58688}{58781}to repair eyes ruined | in a boyhood accident. {58877}{58952}He hopes that when | the bandages come off' {58957}{59081}he'll be able to see | for the first time in 40 years. {59219}{59264}MAY: l didn't expect | anything to happen {59269}{59327}for at least a couple of weeks. {59332}{59451}So to go into that room and | have the bandages peeled back {59456}{59571}and then to actually | see light coming in {59576}{59657}was more than words | can really describe. {59805}{59878}All of a sudden, | there's the overwhelming whoosh {59883}{59960}of visual input' {59965}{60073}things resolving into colors | and shapes, {60078}{60149}images whooshing everywhere. {60250}{60319}NARRATOR: | Rebuilt eyes allow light {60324}{60394}to reach Michael's retinas. {60486}{60559}First thing you should see | is your wife. {60564}{60623}NARRATOR: | But Michael has a problem. {60640}{60690}After 40 years in the dark' {60695}{60799}his brain doesn't recognize | what his eyes can see. {60804}{60957}vision wasn't as simple | as just turning on the sight {60962}{61031}and all of a sudden | being able to read a book. {61036}{61093}lt's much more complicated | than that. {61098}{61180}vision isn't something | where you flip a switch. {61185}{61220}Come here, baby. {61225}{61309}NARRATOR: So, what visual sense | will Michael have {61314}{61398}of a world he hasn't seen | in 40 years? {61549}{61593}Once blind, {61598}{61713}Michael May's repaired eyes | now work almost perfectly. {61718}{61817}But surprisingly, | he can hardly see. {61894}{61989}The reason is the age | at which Michael lost his sight. {62074}{62170}A freak chemical explosion | at age 3 blinded him. {62175}{62237}[ Monitor beeping ] {62242}{62334}40 years later' he underwent | an experimental procedure {62339}{62389}to restore his sight. {62394}{62457}Doctors replaced a key part | of the eye {62462}{62540}destroyed in the accident' | his cornea. {62562}{62651}This clear' paper-thin coating | protects the eye {62656}{62711}and helps it focus. {62780}{62826}The damage to Michael's eyes {62831}{62901}kept him from making out | anything. {62945}{62987}He hoped that new corneas {62992}{63070}would mean another chance | to see the world. {63075}{63130}...you should see is your wife. {63151}{63210}NARRATOR: | But 40 years of blindness {63215}{63287}left him with a larger problem. {63385}{63489}MAY: l was trying to | latch on to images {63494}{63545}and make sense of the world. {63568}{63616}lt wasn't as though l saw a face {63621}{63689}and said, "Oh, that's a smile "' | automatically. {63694}{63791}l had to intellectualize | this whole process, {63796}{63843}dissect it' | and then figure it out. {63885}{63984}NARRATOR: Michael May has | no visual memory of the world. {63989}{64056}Are you making a funny face? {64098}{64163}NARRATOR: lt's not something | we're born with. {64168}{64252}At birth, | everything we see is new, {64257}{64309}but we archive the images, {64314}{64376}learning their content | and meaning. {64381}{64480}We build our visual memory | through experience. {64535}{64583}At the back of the brain, {64588}{64703}over half a billion brain cells | make up our visual cortex' {64708}{64784}the processor and storehouse | for vision. {64816}{64908}Early in our lives, | we build our visual memory. {64913}{64964}And as long as we live, {64969}{65072}that library helps us | make sense of the world. {65133}{65170}SADU N : | The interpretation {65175}{65240}and therefore the recognition | of certain things {65245}{65297}takes a tremendous amount | of experience. {65302}{65364}l n this sense, | the brain is learning to see. {65369}{65434}And this is taking place | over the first six years {65439}{65511}or' to a smaller extent' | even the first nine years. {65626}{65687}NARRATOR: But when Michael | was blinded at 3, {65692}{65765}he'd only just started | to understand the things {65770}{65840}that make up his ability | to see. {66091}{66205}Size, shape, and distance, | light and shade. {66298}{66459}MAY: ls that a curb, a step | down, a step up, or a shadow? {66464}{66583}Just in terms of the brain's | ability to analyze the depth, {66588}{66690}to see the edge and to realize | that there's a 6-inch drop {66695}{66834}to the curb, l'm just not able | to perceive that information. {66851}{66953}lf he had spent | a childhood seeing {66958}{66990}and playing with his bicycle {66995}{67060}and riding off curbs | of different sizes, {67065}{67127}he would have learned subtle, | different cues {67132}{67164}that lets him distinguish {67169}{67236}between a 3-inch curb | at one distance, {67241}{67293}a 6-inch curb a little further' {67298}{67371}and a 9-inch curb | further than that. {67376}{67417}Deprived of that experience, {67422}{67510}it gets to be very hard to do so | on an optical basis alone. {67535}{67613}NARRATOR: Now Michael's | adult brain has to struggle {67618}{67704}to catch up on the learning | it missed as a child. {67709}{67806}But Michael does recognize | and enjoy some things. {67811}{67916}MAY: l'll use a cane to deal | with what's in front of me. {67921}{67953}And then l can look around {67958}{68050}and appreciate the things | that l can perceive -- {68055}{68188}bright-colored flowers, | landmarks, people walking by -- {68193}{68267}things like that | that l can use my vision for. {68272}{68347}And l don't even think | about what's in front of me. {68371}{68449}NARRATOR: Michael May inhabits | a weird world {68454}{68515}between blindness and sight' {68520}{68615}frustrated by his lack | of visual memory. {68715}{68795}F or most of us, | this same visual memory {68800}{68914}unlocks another universe, | the world of dreams. {69179}{69268}When you're in a dream, | that is your reality. {69273}{69343}You visually are seeing things. | You are hearing things. {69348}{69394}You can literally feel things. {69399}{69473}You can see your body moving, | et cetera. {69478}{69518}And you can experience anything {69523}{69592}that you would experience | in waking life in a dream. {69613}{69684}NARRATOR: Dreams consist | of images we've collected {69689}{69720}with our eyes. {69725}{69830}Like a film editor' | the brain reassembles them. {69943}{70015}M l LLER: l'm usually | on my stomach with my arms out' {70020}{70054}kind of like Superman, {70059}{70145}and l'm gliding | over different sceneries. {70150}{70274}l find it a bit of a high to go | in between, dodge the buildings, {70279}{70358}and go fast | and go up and down and over. {70398}{70509}l feel like a bird soaring | in the air. {70514}{70571}l've always wished l could fly. {70588}{70702}NARRATOR: l nterestingly, many | people share the dream of flying {70707}{70803}and endure the nightmare | of being pursued. {70826}{70913}The brain can create | utterly realistic scenes, {70918}{70974}even though | we've never experienced them. {71019}{71059}WOMAN : | Someone's following me, {71064}{71143}and l have this urge | to just run away. {71148}{71240}MAN : l started running away | from it' seeking higher ground. {71245}{71290}WOMAN #2 : | He was faster than me. {71295}{71369}WOMAN #3: But l ran into | the back door of the hospital. {71374}{71467}NARRATOR: Reports of such bad | dreams recur throughout history, {71472}{71521}and the meaning | of these night visions {71526}{71595}has always fascinated us. {71620}{71754}3,000 years ago, the Egyptians | compiled a book of dreams. {71759}{71808}lt listed familiar dream images {71813}{71874}and offered interpretations | of them. {71879}{71950}DR. PARKl NSON : | Dreams were a sort of moment {71955}{72061}when the boundaries between | this world and the next world {72066}{72106}seemed very thin. {72140}{72204}But for many of the dreams | in the dream book' {72209}{72313}it's clearly a search for | what will happen in the future. {72377}{72449}NARRATOR: Now we explain | bad dreams as useful {72454}{72573}in helping us conquer deep, | often universal fears, {72578}{72697}just as we see good dreams | as fulfilling our fantasies. {72719}{72794}Sights seen in dreams | may well connect us {72799}{72894}to our ancestors' instincts | and fears -- {72899}{72982}yet another example | of how our sense of vision {72987}{73079}has always dominated our lives. {73520}{73613}Our visual system shows | better than any other {73618}{73698}how intricately our bodies work. {73755}{73862}Throughout history, it has | supercharged human development' {73867}{73970}and it could allow us | to take charge of our future. {73999}{74081}Sight dates back | to our deep past -- {74086}{74224}unsung, unnoticed, | a faculty we take for granted. {74229}{74368}But when revealed, sight shows | how everyday life depends on it. {74422}{74582}Pushed to the limits, we can see | the superhero inside us all, {74587}{74629}the human body. 39526