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00:00I look in the mirror and I don't know who that is.
00:11I could be looking straight at something and I just don't know what I'm looking at.
00:18It's almost as if I am daydreaming, there is no sense, no meaning in what I see.
00:29One man can't recognise everyday objects, another can't recognise faces.
00:34Damage to their brains is preventing them from making sense of the world.
00:44If it's the brain that sees, how does it do it?
00:47How does our brain manage the immense task of generating vision?
01:12Las Vegas, the brightest city on earth, a city that erupts every night into an explosion
01:19of light.
01:27It feels as though we see it all without effort, but our brains are working away frantically.
01:39Vision seems so simple, we just open our eyes and we see what's there, but in fact
01:44we're taking on an awesome challenge.
01:47What's actually hitting our eyes is a jumble of light and transforming this jumble into
01:51the complex world we know demands a phenomenal amount of brain power, yet we do it all in
01:56the blink of an eye.
02:05Every aspect of everything we see has to be constructed inside our heads, movement, shape,
02:12colour, size, what everything is and where it is.
02:19Nothing in the world is simply there, it all has to be pieced together by the brain.
02:31The more we learn about how the visual system actually works, the more it seems to contradict
02:35the actual experience of sight.
02:38Information coming into our eyes is dismantled and reassembled so convincingly that we never
02:42realise what's actually going on.
02:47As neuroscientists gradually discover the elegant tricks and bold shortcuts the brain
02:51uses, it's becoming clear that our mental image of the world is only loosely based on
02:56reality.
02:58Could our experience of just seeing what's out there be an elaborate illusion?
03:15Even the most basic features of vision are constructed by the brain.
03:19The most compelling evidence for this comes from the study of extremely rare cases of
03:24highly selective brain damage.
03:33Twenty years ago, Giza Lilipold suffered a stroke.
03:38It left her unable to see motion.
03:45Everything she sees is frozen, even though her other senses shout out that the world
03:52is moving by.
03:55For Giza Lilipold, looking at a moving object is an unsettling experience.
04:22Faced with the massive amount of visual information coming into our eyes, it seems
04:52we divide up the task of building the scene in our heads into different components.
04:57And Giza has lost one vital component of her visual world.
05:12My first impression was that it's something really very strange.
05:17When I asked her, now what is your problem, she told me I can't see objects in motion.
05:25And like others, I didn't believe it, because nobody has ever described a case like this.
05:47Professor Joseph Zil has studied the unique phenomenon of Giza Lilipold for 20 years.
06:06His tests reveal how she now struggles to make sense of the world.
06:12She relies on the fact that the static image she is seeing is eventually updated.
06:18After a delay of a few seconds, she can deduce that something is moving if the snapshot in
06:22her mind has changed.
06:32Giza Lilipold's stroke damaged a small area at the back of her brain.
06:36What makes her unique is that the damage was precise and also symmetrical.
06:41This accident of chance proves that when damaged, particular brain regions can selectively
06:47prevent the processing of movement.
06:50It is very difficult to imagine how the world of Lilipold may look like.
06:59Although she cannot see movement in the sense of tell us whether something is moving or
07:05not, or tell us the direction of movement or the speed of movement, moving objects appear
07:12to her as restless.
07:14And this is what makes her feel very unwell and irritates her and makes life so difficult
07:21for her.
07:23I don't look as much as possible when you are in front of me and it moves.
07:34I usually look at another one where not so much is moving.
07:50Her eyes only capture static images, still photographs of the world outside.
07:58These images travel to the back of the brain where they are incorporated into the sensation
08:03of seeing movement.
08:08And we now know that different aspects of vision are dealt with by different visual
08:13subsystems.
08:17No one knows why the brain is organised this way, but it makes sense to me that this division
08:22of labour is the most efficient way for coping with everything that's bombarding the eye.
08:31If the brain would be built in a way that only one structure or one mechanism or one
08:37module would have to process all the visual information which is coming in, then it would
08:44take much longer time.
08:46So the solution is to have smaller visual areas, smaller mechanisms, and each mechanism
08:54is dealing with just one aspect of visual information like form or colour or depth or
09:00movement.
09:01Gradually, neuroscientists are building up a detailed map of this parallel processing.
09:08The raw jumble of information from the eyes travels to the primary visual cortex and on
09:12to a series of increasingly specialised areas for processing.
09:16So far, over 30 different areas have been discovered, working on motion, colour, depth,
09:25shape and even which way an edge is pointing.
09:28We can't say yet exactly what they all do, but recently an underlying logic to this assortment
09:34of areas has been uncovered.
09:35OK, so if you close your eyes.
09:41These two bars are exactly the same size.
09:44It seems as though my visual system has been totally fooled by this illusion, but this
09:49experiment proves that's not the case.
09:51OK, if you open your eyes again, can you tell me which looks longer if either of them do?
09:56Yes, this one looks longer.
09:58Fine, OK.
09:59The precise movements of my fingers are tracked by a special set of cameras as I reach for
10:04the bars.
10:06Perfect.
10:09If my entire visual system has been fooled, then my grasp should be wider for the bar
10:14that looks bigger.
10:18And open them.
10:19And tell me again, are they the same or different?
10:22No, this looks bigger.
10:23OK.
10:24So, when I say go, pick up the one on the right, two, one, go.
10:34Great.
10:38The movements of my fingers reveal a fascinating aspect of the workings of my brain.
10:45The bars look different lengths, but my fingers shape to pick them up in exactly the same
10:51way for each.
10:53Part of my visual system, which is guiding my hand, has not been tricked by the illusion
10:58and is acting independently of what I'm consciously seeing.
11:06This kind of ingenious research shows that all the specialised visual areas are organised
11:11into two different pathways with very different roles.
11:16One pathway, which was guiding my hand, helps us interact with the world.
11:22We're unaware of it, but every movement we make is fed by information from this pathway.
11:29The more laborious task of recognising what things are is handled by a different pathway.
11:37Maybe that's so we don't have to wait until we know what something is before we move to
11:41deal with it.
11:44It seems my hand can ignore what I think my eyes are actually seeing, because these two
11:48tasks are treated so separately in the brain.
11:52We don't yet fully understand why this segregation occurs, but of the two, it is the recognition
11:56system that seems to take up more brain power.
12:00Recognition is a vital part of our visual system.
12:02It turns seeing into understanding.
12:10Of all the things we need to recognise, there's one which is fundamental to how we live our
12:15lives, the human face.
12:18It's how we know who someone is, whom we love, whom we hate and whom we fear.
12:24Our brains seem tuned to spot faces.
12:33We have so much hardware in our heads that is dedicated to recognising faces.
12:43It takes almost nothing to make us see a face.
12:46I mean, just a big chunk of our brain is saying, where's the face, where's the face?
12:52So the most minimal configuration of lines and a couple of curves will look like a face.
13:01Even clouds, the man in the moon, just the pattern of craters on the moon, we see as a face.
13:23But Lincoln Holmes finds recognising a face impossible.
13:2830 years ago, he was in a car accident that damaged an isolated part of his brain,
13:33and he is now completely face-blind.
13:38On those moments when I am suddenly alone and I don't know where anybody that I'm with is,
13:46there can be a surge of fear.
13:50There can be a surge of fear, and it's lonely in that sense.
13:56The very thought of something so basic as recognising faces being lost is not only hard to imagine,
14:07but it's pretty scary.
14:11One of the things that makes it hard for people to believe that I have such a deficit
14:17is that I'm not blind.
14:20I see them.
14:23And seeing, in our vocabulary, is synonymous in some ways with understanding.
14:29I see what you mean.
14:32And it's very hard for folks to understand that I can see them,
14:37and it's very hard for folks to understand that I can see them and not know who they are.
14:43Sometimes it seems like maybe he recognises me because I'm in the right place at the right time.
14:48I've said we're going to meet at such and such a location, and he finds me and he says,
14:53Hi, Holly.
14:56But I think it's because we've made pre-arrangements that, yes, we're going to meet at X place at X time.
15:02Maybe another way to put that is that when there are just the two of us sitting here, that's one thing.
15:06When we go out to the supermarket, say, and get separated,
15:09then there are a couple of dozen female faces walking all around.
15:13I haven't got a prayer. I haven't got a prayer.
15:16I haven't got a prayer picking you out of all those faces.
15:25What's that?
15:26That's a key.
15:27Great.
15:32That's an apple.
15:33Okay.
15:38That's a place setting with a knife, fork, and spoon and a plate.
15:42All right.
15:47Who is it?
15:49Who is it?
16:00I don't know. I don't know.
16:02Okay.
16:04Young woman, old woman?
16:11To be very honest, I'm having trouble answering that question.
16:16Well, let me give you some biographical details.
16:20She's a movie star from the 1950s, very glamorous.
16:25She sang happy birthday to President Kennedy once.
16:30Madeleine Monroe?
16:31Yes.
16:33Madeleine Monroe, as you know, had a close affiliation with more than one Kennedy.
16:38But that's neither here nor there.
16:41Right.
16:42When I'm asked by people sometimes, do faces just all look the same,
16:46the answer to that question is that no, they don't all look the same.
16:52And they say, well, why don't you recognize them?
16:54And the answer is, they don't all look the same, but they don't all,
17:00in other words, they don't all look like John Smith.
17:05None of them look like anyone.
17:09They all are faces, but they are not recognizable as anyone's face, any of them.
17:17He sees the skin. He can see the texture of the skin.
17:21He can see the individual features fairly well.
17:26But what he doesn't see is the totality of the face.
17:34He can't simultaneously apprehend all of those different parts together.
17:40And that's what we have to do to be able to recognize a face.
17:47It's hard to imagine what Lincoln is actually seeing when he looks at a face.
17:52It seems that his brain is not allowing him to put all the pieces of the puzzle together.
17:57Instead, he is confronted with a jumbled-up mixture of features
18:00that don't connect with even the most familiar of faces.
18:09OK. How about that person?
18:17Mm-hm. Don't know.
18:20Any sense of familiarity?
18:24No. No.
18:27What about the... There's a child's face sort of looking over his shoulder.
18:34Any familiarity there?
18:41This is the nastiest one of all, isn't it?
18:43Yes.
18:44This is me.
18:45Yes.
18:48How do you feel looking at a picture of your own face and not recognizing it?
18:56For me, it is a face.
19:01It's not my face.
19:04It's a face.
19:07And there is some sense of incompleteness there.
19:13But...
19:21So be it.
19:27Lincoln's story has helped reveal how our brains process faces.
19:38Each time we look at another human being,
19:40a specific facial recognition system is activated.
19:44It turns out that this system is so specialised
19:47it only deals with faces which are the right way up.
19:52It seems that facial recognition is such a demanding
19:55and important part of our lives
19:57that we need to dedicate a whole subsystem of the brain to this task.
20:01And the work with Lincoln suggests that this face area
20:04plays no role in recognising any other type of object.
20:13This is a human face.
20:16This is a human face.
20:22Muhammad Ali.
20:24Cassius Clay.
20:26Yes, absolutely right. Good.
20:30Albert Einstein.
20:32Good.
20:37It's oblong.
20:42It's got lots of legs on it.
20:46There's a black thing at the top of it, I don't know what it is.
21:00If I told you that it was a kind of scrubbing brush, and what you refer to as the legs are
21:05actually the bristles, the black part at the top is actually just a shadow that's falling
21:11from the lighting, it's not actually part of the object itself.
21:15I can see how that could be a scrubbing brush, but I didn't get it.
21:25In Ottawa, Kevin Chappell provides another vital clue to the brain's visual recognition
21:31system.
21:33He has no trouble with faces, but a car accident has left him totally unable to make sense
21:38of the world.
21:39He sees all the details, but not what things are.
21:43Well, after all these years, I've kind of got used to it now.
21:52It's me, it's how I am, it's my world.
21:57Often I'll let things just pass me by.
22:00If I have to, then I'll make an effort to figure out what it is.
22:04For example, the upper part of what I'm seeing is blue, therefore probably sky.
22:12The green is obviously if it's sticking up, it's the skyline, there are trees.
22:20If it's flat, it's grass.
22:26That's how I make my sort of judgments about where I am.
22:31Many times I'm wrong.
22:36It's a very interesting and fairly rare condition whereby the eyes are working just fine and
22:43can take in the light from the visual world in a perfectly normal fashion.
22:52The problem is, in Kevin's case, in being able to decode these signals and produce a
22:58coherent interpretation of the world.
23:04So it's not like he has lost his knowledge of what objects are, and it's not like he
23:08simply cannot produce the name for it, you know, maybe he's just forgotten what the word
23:12is.
23:13None of those can account for his problem.
23:16The problem is an inability for the information from the visual world that's coming into his
23:21brain to make contact with this knowledge that he has about objects.
23:27I really don't know what they're coloured, coloured squares.
23:39There are some faces in the squares.
23:43I can see seven faces.
23:49What about in the parts where there aren't faces?
23:52There was just red blotches and black blotches.
23:56Oh, and they could be playing cards.
24:00The blotches is like...
24:03So it's interesting that you were so rapidly able to pick up the faces, but the suits somehow
24:11didn't quite make sense to you.
24:22It's becoming increasingly clear that the brain segregates objects from faces, but we
24:34still don't fully understand why or how this compartmentalisation occurs.
24:39What is so special about faces that means they need separate processing in the brain?
24:46One reason might be that faces actually look very similar.
24:50So a specialised area within the brain is required with a finer, more powerful level
24:54of processing.
24:56Without this facility, we'd be able to spot a face, but we wouldn't be able to distinguish
25:01whose face it was.
25:12Object recognition seems to be a simpler task.
25:15It doesn't need such a high level of processing.
25:18Once we've named an object, we don't normally need to take the recognition task any further,
25:23and so a more basic part of the brain is used.
25:32But even with all these specialised systems working away, the brain would be overloaded
25:37if it tried to tackle every detail of every object at once.
25:44So we just don't bother.
25:46We're all equipped with a means of selecting the key aspects of a scene one at a time.
25:52This attention system allows us to concentrate on one thing while the rest of the world falls
25:58into the background.
26:02All this happens so automatically that we don't notice it, but our brains are constantly
26:07scanning the scene, not just passively analysing what's coming in, but actively deciding what
26:12it is it wants to see.
26:14It seems that we don't just have to point our eyes in the right direction, we also have
26:19to point our brains.
26:24The difference between these two men seems obvious.
26:27Their faces are different, their hair is different, even their shirts are a different colour.
26:33And yet an experiment by psychologists Dan Simons and Chris Chabris at Harvard reveals
26:38that our brains actually process very little of what comes in through the eyes.
26:43In this experiment, a subject comes up to a counter and a first experimenter hands them
26:50a consent form.
26:54As soon as they finish signing the consent form, they hand it back to the first experimenter,
26:59who then takes the consent form, ducks down behind the counter to put it away, and a different
27:04experimenter then stands up and hands the subject a packet of information and sends
27:09them into a hallway where we ask them questions about it.
27:13This wonderful experiment uncovers an aspect of the brain's attention system known as change
27:18blindness.
27:19Change blindness is the idea that we often miss large changes to our visual world from
27:24one view to the next.
27:26We're often not able to see large changes that would appear to be perfectly obvious
27:31to somebody who knows they're going to happen.
27:34And incredibly, in 75% of cases, the subjects don't notice a thing.
27:42The lady who took me up here, she opened the door for me and told me to walk over to the
27:47desk.
27:48I think there was a sign that said experiment, and a man there gave me a form to sign.
27:57There was the guy standing under a big sign that said experiment, and to my left there
28:03was like a pot with some dirt in it and some plastic containers.
28:12Oh, I filled out a form.
28:15How long would it be about before...
28:17And I asked him how long it would take, and he said about 10, 15 minutes or so.
28:22I guess I have the time to do that.
28:26Did you notice anything unusual at all after you signed the consent form?
28:30I just signed it, and I didn't even pay attention to anything that was written on it.
28:34Okay.
28:35After you handed it back to him, did you notice anything unusual happen at all?
28:40If you could just take this into the next room.
28:42No, I probably wasn't even looking in that direction.
28:45I probably turned and looked towards the clear door.
28:48I saw some people there, and then I turned back and looked at him for a second.
28:53Okay.
28:54Did you notice anything unusual at all after you signed the consent form?
28:58No.
29:00This is only going to take 5 to 10 minutes?
29:02Yeah, it'll be real short.
29:04Okay.
29:05The person who stood up was actually a different person.
29:07Okay.
29:08I gather you didn't notice that that was different?
29:10No.
29:11A different person actually stood up and handed you this form and sent you out toward me.
29:15I gather from your action you didn't notice that?
29:18No.
29:19Okay.
29:20Don't feel bad about that.
29:22Actually, most of the time we find about 75% of people don't notice.
29:25Are you serious?
29:26Yeah.
29:27The person who stood up with the packet was actually a different person.
29:29Wow.
29:30Than the first person.
29:32That is incredible.
29:33So I gather you didn't see it.
29:34I didn't catch that, no.
29:35Okay.
29:36What's really interesting is that some people notice these changes
29:39and other people don't notice these changes.
29:44Okay, if you could just take this.
29:46And we really don't yet have a good idea what separates those people who don't
29:50from those people who do.
29:54It might be that there are individual differences
29:56and some people are better able to detect these sorts of changes.
29:59But it's also possible that it's just coincidence
30:03that the people who noticed it
30:05just happened to be focusing on a feature that changed.
30:08They just happened to be paying attention to the color of the person's shirt.
30:13And the people who failed to notice it
30:16just happened to be paying attention to something else.
30:22The brain's attention system allows us actively to select what to look at.
30:27It makes us very good at concentrating on tasks
30:31but it can also make us miss something happening right in front of our eyes.
30:41Magic is all about making us think we are seeing everything
30:45when in fact we are missing the most important thing of all.
30:48Magicians exploit the brain's attention system to the extreme
30:52but understanding how attention is organized in the brain
30:55has been a difficult challenge.
31:01Once again, it's damage to the brain
31:04which reveals much about how the normal brain functions.
31:07The attention system is often affected
31:10after injury to the right-hand side of the brain.
31:13This leads to a condition known as neglect.
31:16Neglect leaves patients with a baffling syndrome
31:19as if half their world has disappeared.
31:25Neglect is a very difficult concept.
31:28It's a medical term that has been used for almost 100 years
31:31to describe a variety of behavioral conditions
31:34that is, what patients actually do when they've had a stroke.
31:37And most of these patients have strokes
31:40involving the right hemisphere, the right part of their brain.
31:43And basically what they tend to do, which is descriptive of neglect
31:46is they ignore one side of space.
31:49So, for instance, they dress one side of their body
31:52they write on the right-hand side of the page
31:55they miss things on the left-hand side.
31:58The stroke that Peggy Palmer suffered ten years ago
32:01has left her with extreme neglect of the left-hand side of her world.
32:04Peter Halligan has spent many years testing Peggy
32:07to try and understand exactly what is going on in her brain.
32:10Sure, yes, go on.
32:13This time, Peggy, I'm going to show you this picture of a cat
32:16and I'd like you to draw it as accurately as you can.
32:19Right, OK.
32:22Neglect is very little, if anything, to do with your eyes.
32:25The vast majority of the problem arises
32:28from the brain processes involved in attention.
32:46And your attentional system provides for where your attention is.
32:49And your attentional system provides for where your eyes move.
32:52So, in other words, if something happens in my visual field
32:55that's interesting, I'll move my eyes there.
32:58But why would you move your eyes there
33:01only if your attentional system indicated you needed to move there?
33:04So your eyes are slaves to your attentional system
33:07and what's wrong in neglect is the attentional system has been damaged.
33:10You notice that this cat has got two tails?
33:13No, I didn't notice that.
33:17You don't have it on that side, do you?
33:20No.
33:23Is there anything else missing in it?
33:26For instance, look around the left-hand side, is there anything?
33:29Yes, that shoulder's missing, isn't it?
33:32The other part of the body is, isn't it?
33:35I don't think about it, you see.
33:38So you thought you'd drawn a complete cat with all the details?
33:41Yeah.
33:44Did that surprise you?
33:47I was very surprised to see that other tail, very surprised, yeah.
33:50Because I really didn't see that at all.
33:53And what do you think when you see something like this now, when I draw attention to it?
33:56I don't know how I could have missed it.
33:59I don't know how I could have missed it, I really don't.
34:02Peggy, as far as I'm aware, never reports when you ask her afterwards
34:05seeing half a cat.
34:08In fact, I can draw half a cat and show it to her
34:11so she can know the difference.
34:14What she draws is different to what she actually seems to see inside her brain.
34:17So Peggy is actually seeing a whole picture.
34:20Her brain is filling in the gaps,
34:23completing the parts that are missing.
34:26Peggy's neglect reveals another vital aspect of the brain's visual system.
34:29In her mind, her drawing is complete.
34:32What is missing on paper
34:35is generated by her imagination.
34:41The power of our imagination
34:44is what makes a good horror film so frightening.
34:57It isn't necessarily what's up on the screen
35:00that really gets our pulses racing.
35:03It's what we think is on the screen.
35:06It seems that the less we see, the more we imagine.
35:09And filmmakers have learnt that there's nothing more vivid
35:12than the pictures we can generate inside our head.
35:19But the imagination isn't just active occasionally.
35:22Research increasingly suggests
35:25that our brains are constantly distorting what we see.
35:28Using imagination, our brains take a bold shortcut.
35:31We guess what's out there from past experience
35:34rather than having to build up the image in our minds
35:37each time from scratch.
35:45Every moment we open our eyes,
35:48our brains are filling in a vast amount of additional information.
35:51The brain doesn't just allow us to see what's out there.
35:54It actually invents much of it.
35:57And over the last few decades,
36:00neuroscientists have slowly begun to understand
36:03how we can create this highly personal inner world.
36:07If you look around,
36:10the world seems to be high-resolution,
36:13almost photographically sharp and complete.
36:16But in fact, you're actually taking in remarkably little.
36:19A lot of what you see or you think you're seeing,
36:22you're actually filling in from memory.
36:25You're actually completing from information
36:28that's been stored from previous times,
36:31previous experiences with the world.
36:35How the brain does this has baffled scientists for decades.
36:38But in recent years,
36:41an extraordinary theory has emerged.
36:44Anatomical studies have revealed that the visual brain
36:47relies as much on information coming from our memories
36:50as from our eyes.
36:53We are using our knowledge of everything we've ever seen in the past
36:56to imagine what is actually out there.
36:59One of the most remarkable facts about the brain
37:02is that of the 32 known visual areas,
37:05virtually all of them that send
37:08a connection to another area
37:11receive a connection backwards from that area.
37:14And those backwards connections
37:17are of comparable size to the forward one.
37:20So there's an enormous amount of information flowing backwards.
37:25The discovery of these pathways has completely revolutionised
37:28our understanding of the visual brain.
37:31We can no longer think of vision as a one-way street,
37:34with information flooding in from the outside world.
37:37Instead, it seems to be a two-way street,
37:40with massive amounts of stored information
37:43flowing backwards from deep inside the brain.
37:46So that's a two-edged sword.
37:49On the one hand, it makes it easier.
37:52You don't have to register every little thing that's out there.
37:55But on the other hand, it's dangerous.
37:58So our perception of the world
38:01is affected as much by what our brains expect to see
38:04as what is actually in front of us.
38:07This room looks normal,
38:10but in fact it's massively distorted.
38:13The girls are exactly the same size
38:16and yet your brain won't allow you to see them that way.
38:23You can't tell that the left side of the room
38:26is much bigger than the right side,
38:29or that the floor slopes down to the left corner,
38:32and that the furniture has been specially designed to fool your brain.
38:36All this creates the illusion
38:39that the girl is changing size as she walks across the room.
38:43Your brain simply will not let you
38:46see the room as it actually is.
38:49Instead, it uses its store of memories
38:52to take a shortcut,
38:55creating an image of this room
38:58based on how you expect all rooms to look.
39:01It's an astonishing example
39:04of how much our visual memories,
39:07our imaginations, can influence
39:10what is right in front of us.
39:13It's not just a matter of how big the room is,
39:16it's a matter of how small it is.
39:19It's not just a matter of how big the room is,
39:22it's a matter of how small it is.
39:25It's not just a matter of how big the room is,
39:28our imaginations can influence
39:31what is right in front of our eyes.
39:36Kevin Chappell helps us understand the process at work.
39:39When he walks onto a football field,
39:42he doesn't understand a thing.
39:45He sees green, but doesn't recognise the grass.
39:48He coaches the local football team
39:51even though the moving white object
39:54doesn't come together in his head as a ball.
39:57brain to imagine what is in front of him. These images are so vivid it allows him
40:02to hide how little he actually sees. I still have the knowledge of what objects
40:07are based on my visual memory and the ability to imagine. You're on a green
40:12field and the ball's round and it's white and you kick it. When the players
40:20get in together and they're sort of tackling each other and there's a
40:25scramble in the goal mouth, I can't tell you what's going on. It's like this
40:30collage of different colours and movement. It's the images stored inside
40:36his brain that allow Kevin to cope with the world around him. His brain damage
40:40has left these pathways undamaged, even though his recognition system is
40:45completely destroyed.
40:49Go ahead.
40:52It's kind of a plate with writing on it.
41:03Why don't you go and hold it? Go on, go ahead and hold it. Close your eyes.
41:08It feels like an old 45. Do you have an image now in your mind of what that is?
41:24It's a 45 with the centre punched out. Bizarrely, Kevin can use his
41:32imagination to draw objects he can't recognise in the real world.
41:39You know, let's go ahead and do some drawing. Why don't we start off by
41:44getting you to draw something like a scrubbing brush. Okay.
41:51Kevin presents to us a very clear example of a person who, unable to
42:02recognise objects, is nevertheless able to see those same objects in his mind's
42:08eye. In other words, to be able to have very detailed and distinct and rich
42:15visual mental imagery. That's pretty good. So that's kind of the handle and
42:23these are all the bristles coming down. Yes, and there's also, I'll try to give some
42:27depth to it as well. It's not just like the other drawings, which is just 2D, it's a 3D drawing.
42:32Good. There seems to be a complete split between what Kevin can see and what
42:39he can imagine. He can't even recognise his own drawings. Do you have any idea what
42:45this is?
42:52Tape? It's actually a bicycle and it's something that you yourself have drawn
43:03for me previously. This is your drawing of a bicycle. It doesn't look familiar to
43:07you? No, it doesn't look like a bicycle either. It's very surprising to find a patient like
43:14Kevin who shows a dissociation between visual mental imagery and perception. The received
43:20wisdom in this area has been that visual mental imagery and visual perception are simply two
43:25sides of the same coin. It's just that one proceeds from the outside world inwards and
43:30the other one proceeds from the brain in a downwards fashion. In fact, having a patient
43:35who shows a dissociation like this suggests that these two processes are really not one
43:41and the same as has traditionally been argued. Kevin's condition has revealed a separation
43:49between the parts of the brain that generate imagery and the parts we use for perception.
43:54So how do these two systems fit together? That someone like Kevin exists makes it very
44:00difficult to understand where all the different components of vision are finally brought together
44:05in the brain. There doesn't seem to be any very obvious area of the brain where the back
44:11projections and the forward projections reach each other and make contact and eureka, a
44:21coherent interpretation of the world is provided. In fact, there probably is no such area. I
44:27think even if we were able to go and look in the brain and see whether we could identify
44:32such an area, I think we would fail in that pursuit.
44:42It's the most intensively studied of all the senses and yet vision remains elusive. But
44:50one by one, we're uncovering all the ingenious strategies and shortcuts our brain uses to
44:55tackle the awesome challenge of seeing. Everything we're learning takes us further and further
45:01from the simple idea that we just open our eyes and see what's there.
45:11A few years ago, I worked in New York with Professor Rodolfo Linas. He's always liked
45:17making provocative claims and now he's convinced it's time for a revolution in how we think
45:22of vision. It sounds extraordinary, but for him, seeing is just another form of dreaming.
45:31If you consider what happens when you dream, you find that amazingly, you actually do feel
45:41pain and you do feel surprised and you see things and you hear things and the people
45:45that you know talk to you in the proper language, with the proper intonation. So what that tells
45:50you that dreaming and being awake are next of kin, if not exactly the same thing.
45:58If this were to be the case, and this is a hypothesis, then we would begin to really
46:02understand what the brain is about, because the brain is about making images.
46:13This idea is in complete contrast to our normal understanding of the visual system. Rodolfo
46:19believes that everything is running in reverse, with the brain creating images that are then
46:25transformed into reality by the information coming in through the eyes.
46:34Basically the brain is a dreaming machine. It is the brain that generates reality, secretes
46:41reality so to speak. The reality is modulated, it's limited by the senses. We need to see,
46:49we need to perceive, we need to dream actively, because this is the only way that we can take
46:56this huge universe and put it inside a very tiny head. We fold it, we make an image, and
47:02then we project it out. That's what we do.
47:08We are only just beginning to understand how the brain conquers the massive challenge of
47:13perception. If Rodolfo Linus is right, then what is going on inside our brains is much
47:19more important than what is going on around us. As I see it, vision is not about simply
47:25soaking up the outside world. Instead it's an active process. It's a process that is
47:31As I see it, vision is not about simply soaking up the outside world. Instead it's an active
47:37process, which invents, ignores and distorts what's entering through the eyes.
47:45It seems that all this is an optional extra. What counts is what goes on inside our heads,
47:51and what happens there is completely personal. It's not so much that our visual system rebuilds
47:56the outside world, but rather that we create from scratch our own private universe, our own reality.
48:10In the next programme, what is it about our brains that has put us in charge of the planet?
48:15What is the source of our unique power to create cities and civilisation?
48:26Transcribed by ESO, translated by —
48:56Transcribed by —