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00:00There are some great questions that have intrigued and haunted us since the dawn of humanity.
00:13What is out there?
00:18How did we get here?
00:24What is the world made of?
00:30The story of our search to answer those questions is the story of science.
00:38Of all human endeavours, science has had the greatest impact on our lives, on how we see the world, on how we see ourselves.
00:47Its ideas, its achievements, its results are all around us.
00:53So, how did we arrive at the modern world?
00:56The answer is more surprising and more human than you might think.
01:03It is a tale of power, proof and passion.
01:14This time, one of the more intimate questions we've ever asked.
01:28What makes us human?
01:30The question, what is human nature?
01:43What is it that shapes our thoughts, feelings and desires, is one that philosophers, writers and religious leaders have all struggled with.
02:01I am particularly interested in how science has wrestled with this particular question.
02:12And that's not just because it gets to the heart of who we are, but also because it gets to the heart of what science itself is.
02:19I want to begin with one of the great civilizations of the ancient world.
02:31Egypt.
02:32The ancient Egyptians were amongst the first people we know about to really wrestle with the question, what makes us human?
02:45We humans are acutely aware of ourselves, of the sense of being alive, of living within our own skin.
02:58But where does this me reside?
03:01Where is the control center?
03:04Where is the essence of what I truly am?
03:06Egyptian beliefs about what made us human are revealed in their attitudes to the afterlife.
03:18Certain organs like the stomach, lungs or liver were seen as so critical they were frequently removed, embalmed and put back inside the body for burial.
03:30The Egyptians believed that the heart was the key to the afterlife, that when you died, it would testify to your good or your bad deeds.
03:42In this papyrus over here, you can see a heart being weighed up against a feather.
03:47If it was heavier than the feather, then this demon over here would come and eat it, and that was all over for you.
03:52In fact, the idea of being light-hearted or heavy-hearted come from the Egyptians.
03:58And in a way you can understand why they thought that emotions resided in the heart.
04:04But certainly when I have been broken-hearted, I felt it in my gut and in my chest.
04:11So, the Egyptians treated the heart with great reverence.
04:16But what about that other organ we now regard as more central to our humanity?
04:21Here at Manchester University, a team of Egyptologists are studying a 2,500-year-old mummy.
04:35An endoscope is going to be pushed up its nose to show me how the Egyptians treated the brain.
04:41Carefully.
04:42As we enter the nose, go through the nasal septum.
04:54How extraordinary.
04:55It's like going into some sort of hidden cave.
05:01It is, isn't it? It's a secret world, really.
05:06We would normally be stopped from going through there because of the bone that would separate the brain from the nasal cavity.
05:12Which should be there?
05:13Yes, which should be there, of course.
05:14Right.
05:15And so now you're actually entering the skull.
05:18Yes.
05:24Ooh.
05:25That's sort of the citron at the top of the head, isn't it?
05:28But there seems to be something missing.
05:32Yes.
05:33There's a brain missing.
05:35How extraordinary.
05:37Do they not see the brain as important?
05:39They recognize that the brain controlled some of the bodily actions, but they certainly didn't think that the individual personality was located in the brain.
05:51So they removed it and discarded it.
05:54They just took it and shucked it out.
05:55Yes.
05:56It shows certain contempt for what we regard as one of our more important organs now.
06:00Absolutely, yes.
06:01Yes.
06:02The Egyptian concept of what makes us who we are was a mystical union between the physical body and an everlasting spirit.
06:19One of the recurring ideas to emerge out of early civilizations like the Egyptians was the belief that we are more than simply flesh and blood.
06:28There is something else, something which is special and makes us human.
06:34This conviction is one of the most powerful and enduring in human history.
06:45This belief shaped thinking for millennia.
06:50But as Europe emerged from the Middle Ages, people started to approach the question differently.
06:55The physical and intellectual frontiers of Europe were changing, and that would encourage a very different view of who we are.
07:16That new view can be glimpsed here, the grandest royal palace in France.
07:22Amongst this great splendor, there's an intriguing technology that to me reflects a great change in how we saw ourselves.
07:41Captured in one magnificent room.
07:52And this is it. It's the Great Hall of Mirrors in Versailles.
08:02It is absolutely fantastic.
08:08And the whole room utterly dominated by this wall of mirrors
08:12which extends down almost 100 metres.
08:14I've never seen mirrors on this scale.
08:22This really is cutting-edge technology.
08:40Now, this is not absolutely perfect.
08:42The surface is not completely smooth.
08:44You can see little bubbles here in the glass.
08:47It's not perfect. It's not like a sort of modern mirror.
08:50But the size and the scale is unlike anything which was really done before.
08:55And compared to the sort of curvy, worthy things in
08:58that most people would know of.
09:00And centuries earlier, this was something different.
09:05Because there was nothing, nothing, nothing like this
09:07had been developed before.
09:10And allowed people to just stand there and look at themselves
09:13and think, you know, who am I? This is me.
09:16This is me.
09:19These mirrors represent the culmination of an idea
09:22that had been emerging in Europe since the Renaissance.
09:28The notion that we are all individuals,
09:32not members of a class or a guild,
09:36but defined by our own desires, ambitions and destinies.
09:40Along with this growing awareness of self came different questions.
09:49What makes me who I am?
09:52Why do I have these hopes, these fears, these talents, these expectations?
09:58And most importantly of all, what is this I, anyway?
10:02Anyway.
10:12Throughout history, the technology of the age
10:15has stimulated new ways of looking at the world.
10:21You can see a thing which looks a little bit...
10:22I don't know what it is.
10:23It looks like some sort of sea creature.
10:25Possibly a prawn.
10:27New inventions have created metaphors
10:32to help us think about what makes us human.
10:37This cult makes me smile.
10:41In 17th century France,
10:44the philosopher René Descartes
10:46was wrestling with the question of human nature.
10:48For inspiration, he drew on a technological wonder of the age,
10:55water-powered mechanical statues.
11:05The story goes that Descartes is wandering through the Royal Gardens
11:09and he sees a fountain.
11:11And in the middle of the fountain,
11:13there is an enormous statue of Neptune,
11:15which is sprouting water a bit like this.
11:16And this particular Neptune, when you come close,
11:19it sort of starts to jab at you with the triad.
11:23And Descartes is rather taken by this.
11:25And he starts to think,
11:27and he thinks perhaps animals are just a form of automator.
11:32Perhaps a prawn really has some sort of gears in it
11:36with lots of sort of intersecting bits and pieces.
11:39And then he starts wondering,
11:41perhaps that's what our bodies are.
11:42They're just sophisticated machines.
11:48For the time, this was a very daring idea,
11:52to suggest we are like machines.
11:55But it begged the question,
11:57what special quality actually makes us human?
12:05Descartes was a man desperate for certainty.
12:07But this was no time to find it.
12:1017th century Europe was riven by religious and political conflict.
12:21Old certainties of church and state were crumbling.
12:26What, thought Descartes, could he trust?
12:32What could he really know?
12:35Descartes is wracked by doubts,
12:40and he wants to find out something he can believe in.
12:44Imagine, says Descartes, the tower,
12:46the tower, and the tower is in fact round,
12:49but you perceive it as square.
12:51Or, for example, this thing here.
12:52From a distance, it probably looks square,
12:54but actually when you hold it up,
12:55it is clearly round.
12:57Your vision has been deceived.
13:02And then Descartes wondered
13:04if all his senses were deceiving him.
13:08He could feel the warmth of his fire,
13:11see its light, hear its sound.
13:13But he'd experienced the same sensations in a dream.
13:20So perhaps the whole world he was living in
13:24was nothing but an illusion.
13:31Descartes is now beginning to really question everything.
13:34The moon, the sky, the stars.
13:37Perhaps they're all figments of his imagination.
13:39But what about mass?
13:42Two plus three.
13:43It always equals five, doesn't it?
13:45But maybe there's a demon who's taken possession of his brain.
13:50Descartes is really beginning to doubt everything.
13:54Down to the very question
13:57of whether he himself existed at all.
14:00And then, finally, he got there.
14:05He realised that the act of doubting implied a doubter.
14:11There was one thing he could be absolutely certain of
14:14was the existence of his own thinking, doubting mind.
14:18He summed it up in a neat philosophical phrase.
14:23I think, therefore, I am.
14:28It may be a familiar phrase, but it contains a profound idea.
14:34The claim that the essence of our humanity lies in our thoughts,
14:39our ability to reason.
14:40And reason was to form the basis of a new experimental science.
14:55Across the channel, a much more bloody approach
15:00to the question of who are we
15:02was to emerge from a great political clash.
15:05The English Civil War.
15:09Oxford was a key royalist stronghold.
15:13For some caught up in the action, turmoil spelt opportunity.
15:22Here in Oxford, a young man called Thomas Willis
15:25was part way through his medical training,
15:28which in those days lasted an incredible 14 years.
15:31The Civil War interrupted his studies,
15:35which in many ways was a very good thing.
15:41Studying medicine didn't necessarily make you a good doctor.
15:45For one very good reason.
15:51Medical teaching was still largely based on ideas from antiquity.
15:57The disruption of his studies gave Willis the opportunity
16:00to investigate the body for himself.
16:06By now, people were exploring the anatomy of the brain.
16:10But still, no-one really knew what it did.
16:17In the mid-1600s,
16:19Willis began a groundbreaking series of dissections.
16:23And I'm about to get a privileged glimpse
16:26of what he would have seen.
16:28The human brain.
16:31There we are.
16:32The human brain.
16:33Isn't it wonderful?
16:34It is.
16:36It is utterly unbelievable when you think
16:38that this brain once thought it reasoned.
16:42It's a unique feature of the universe, really.
16:46When a brain is sort of fresh, it's a very different consistency, isn't it?
16:49Yes, it is.
16:50I tell the students it's a bit like a badly set jelly.
16:54Presumably, if you were to cut that, you really would have great difficulties.
16:57Yes, it would just fall to pieces, really.
16:59Willis was one of the first to use a new technique.
17:07Preserving brains in alcohol.
17:10This made them firm enough to dissect with great precision.
17:14You ready to cut them?
17:17Yes, ready to cut.
17:26Isn't it strange?
17:27What's really curious is there's almost no structure or definition to it, is there?
17:41Well, the thing that really catches your eye is the ventricles in the centre,
17:44which were what everybody was preoccupied with before Thomas Willis.
17:49And the idea was that this part of the brain may have acted as a sort of pump
17:55and important activities may have gone on in the fluid that was moving around in the ventricles.
18:01So, in a sense, all this is just muscle,
18:04and all the thought and the important stuff is somehow taking place in these holes over here.
18:08Yes, and it was Thomas Willis who realised that the actual structure of the brain
18:12was what was critically important.
18:14When Willis looked at animal brains, he concluded,
18:18our intellect and thoughts must lie in the parts of the brain animals don't possess.
18:24Thomas Willis was very struck by the corrugated surface of the human brain
18:30as compared to the smooth surface of the sheep.
18:33And this enables a huge volume of cerebral cortex
18:36to be contained within the relatively small volume of the skull.
18:40And that's where he thought being human resided, isn't he?
18:43Yes.
18:45You can see there's a ribbon of cortex going over the surface of the cerebral hemisphere.
18:49Right, you see.
18:50Yes, that's right.
18:52And this cortex was where he realised people were likely to have their thoughts.
18:56Willis had established a link between the state of the brain and the state of the mind.
19:05He wrote the first book specifically about the brain.
19:10From now on, anatomical studies would become one of the great foundations of a scientific explanation of who we are.
19:22Reason was now seen as the pinnacle of human nature.
19:36It had been shaped by philosophical doubt and detailed dissections of the brain.
19:42Europe entered a new age, a celebration of the rational mind.
19:53Faith in reason would underpin the growth of trade and the building of empires.
19:59In 1837, something was causing a stir at London Zoo.
20:16Their first orangutan, Jenny, was introduced to an astonished audience.
20:22Exotic animals were being brought to Britain from across the empire.
20:33Even Queen Victoria herself came calling.
20:42Jenny's arrival would challenge assumptions about what makes us human.
20:47Right, come this way, Michael.
20:50I'll introduce you to Batu.
20:52He should be waiting.
20:54There he is.
20:56Hello.
20:57This is Batu.
20:59Wow, he's big.
21:01This is very big.
21:02What a beautiful face.
21:03Very big and very strong.
21:05Right, can I do this?
21:06Yeah, just be careful with the orange, yeah.
21:08Yeah.
21:10Oh, very delicately done.
21:12He doesn't want to drop it.
21:13He's even ruder than my kids.
21:19That's rude, stop it.
21:21You could actually see that wonderfully sullen look on his face.
21:24Yeah.
21:26That look of, mmm, don't like that.
21:28It's a very human expression.
21:32Bad behaviour.
21:34Oh no, that's terrible.
21:38It's wonderful, this is a great sense of independence.
21:40Stop it now.
21:44So you've spat at me.
21:46You've played your game.
21:48What are you going to do next?
21:49Come on.
21:53God, that's smelly.
21:54One of the visitors to the zoo was young Charles Darwin.
22:06But this isn't the familiar story about evolution.
22:12His visit to the zoo was part of his lesser known research.
22:20Fascination with animal emotion.
22:24One day Darwin saw something that really astonished him.
22:28Jenny was playing with the keeper.
22:33And the keeper had an apple.
22:35And the keeper was taunting Jenny by waving the apple in front of her
22:39and not letting her get hold of it.
22:41And in Darwin's words, the ape threw herself on her back
22:44and cried precisely like a little child.
22:46Darwin became convinced that the expressions of emotion he saw in Jenny and in humans were the same.
23:00His research developed over 30 years.
23:03Tenderness, shame, joy, he saw them all in animals.
23:19Darwin's painstaking work led to one of his most important books.
23:23The expression of the emotions in man and animals.
23:28It was greeted with alarm and fascination.
23:32Now this is a really incredible book, partly because of the illustrations.
23:37Because this is one of the first books ever to include photographs.
23:40And they feature people.
23:43People in various states of distress, if you like.
23:46This consulate, sad, very sad looking.
23:49He examines it in almost microscopic detail.
23:51There's a very interesting picture here of a woman's forehead.
23:54And he notices these two lines coming up here, which are later called in fact the Darwin grief muscle.
24:05What Darwin was undermining in his work was a fundamental belief.
24:12A belief in human uniqueness.
24:24By suggesting a close kinship with animals, he'd also open the lid on the rational mind.
24:30Hinting at a dark subterranean world of instincts, desires, emotions.
24:37The animal within.
24:43Here was an irony for Victorian science.
24:47The power of reason which made us unique had been turned on ourselves.
24:52And revealed us to be less exalted, less rational, than had been suspected.
25:10A new side of ourselves was being unearthed.
25:15Darker and more dangerous.
25:17In Paris, doctors began to explore this untamed side.
25:26At La Salle Petrière.
25:31This imposing looking building was originally used to store gunpowder.
25:37But then they decided they could put it to better use.
25:41To lock away thousands of people who were regarded as just as unstable and dangerous.
25:46The destitute and the insane.
25:56It had been Europe's most notorious women's asylum.
25:59With nothing to offer but cruel imprisonment.
26:08These are some of the cells where they kept the women.
26:11And these are the original bars behind which they were imprisoned.
26:15And there is something terribly poignant about the idea of thousands of women chained up.
26:22In filthy living conditions.
26:25Utterly without any prospect of release.
26:29No hope.
26:31No hope at all.
26:32No hope at all.
26:37But attitudes were changing.
26:40After years of revolution, the asylum had become a place of care.
26:45Rather than simply imprisonment.
26:51One of its most famous physicians was Jean-Martin Charcot.
26:54Often the best way to understand the normal is to study the abnormal.
27:04And here there were 5,000 troubled minds to study.
27:12Charcot was one of the first people to try and separate out and categorize different forms of mental and neurological illness.
27:20He took incredibly detailed notes and he also took lots of photographs.
27:29One condition in particular had been puzzling doctors.
27:34They called it hysteria.
27:39Patients suffered paralysis, seizures, blindness and violent fits.
27:45Charcot presumed these symptoms were caused by a physical disease.
27:50But then he began to use a remarkable new approach.
27:57Five.
27:59Six.
28:01Hypnosis.
28:03Seven.
28:05Charcot found he could induce and relieve symptoms of hysteria using hypnosis.
28:10And become aware of any feelings of lightness.
28:13Going up.
28:15It could produce extraordinary effects in the body.
28:18Drifting up and up now.
28:20And the balloon really sort of taking off now.
28:23And bobbing from side to side.
28:25Okay. Can you see the balloon?
28:27Okay. It's a big blue balloon.
28:29Okay. And it's sort of Winnie the Pooh blue balloon.
28:32Okay. But you get that feeling of the...
28:34I've tried hypnosis before.
28:36But this is the first time it's really worked.
28:40Okay. And just notice what's happening there.
28:43Over the course of an hour, I mysteriously lost coordination of my hand.
28:48It gets even more noticeable.
28:50In fact, it's become really shaky now.
28:53I had my hands stuck together.
28:56The knuckle looked.
28:58Oh.
29:00And most bizarre of all,
29:01one side of my visual field was rendered almost useless.
29:06These are a bit fainter.
29:08Okay.
29:10And I have a sense of something over there, but not really.
29:12Okay.
29:13Not really objects.
29:14Okay.
29:16One, two...
29:18That was extremely odd.
29:20It was a bit like I was there, but I wasn't there.
29:23That he was talking to some other part of me.
29:27And the other part of me was responding.
29:29Higher.
29:31And higher.
29:33And the idea you could just do it with the power of words.
29:36Quite strange.
29:38Charcot's observations of hysteria led him towards a radical conclusion.
29:48If symptoms could be induced or relieved by hypnosis,
29:53then perhaps they were not signs of some pathological disease.
29:57Perhaps they were caused by emotions
30:00that the patients themselves were not even aware they were feeling.
30:03Charcot never fully grasped what he was dealing with,
30:08what we would now call the unconscious mind.
30:14In amongst the crowds at one of Charcot's famous demonstrations
30:19was a young Austrian doctor, Sigmund Freud.
30:22A man who would famously use the study of hidden emotions
30:29and repressed urges
30:31to develop this extraordinary concept of the unconscious mind.
30:38Freud's ideas would become a significant cultural influence
30:42on the 20th century.
30:47They would join a rising tide of other ideas
30:50that would form a wholly new approach to who we are.
30:55Psychology.
31:05A less than rational self had been revealed.
31:11By animals brought back from distant lands.
31:14By changing attitudes to mental illness.
31:18And a new door into the unconscious mind.
31:24We could no longer see ourselves simply as creatures of reason.
31:28By the end of the 19th century, Europe was in the throes of a bold new age of communication.
31:47Thousands of miles of new railway linked the continent's great cities.
32:02Telegraph cables joined people across the globe.
32:07This interconnected world led to a different way of looking at how the brain works.
32:24This new technology naturally enough inspired new metaphors to describe the nervous system.
32:29For example, if I pinch my finger, then the pain fibres go down the line, up into my spinal cord and from there to the brain.
32:39The thing is, what happens next?
32:41Well, everyone knew there were complicated signal boxes and junctions up there,
32:45but nobody knew just how they worked.
32:46The Spanish countryside.
33:04Home to a scientist I deeply admire.
33:07He had a passion for art that would shape his future career as a neuroscientist.
33:13His name was Santiago Ramon y Cajal.
33:28When he was a young man, Cajal was obsessed by art.
33:32As he later wrote, I was gripped by an irresistible mania.
33:36I painted everything that captivated my sight.
33:38Earth, foliage, plants, the human form.
33:43He was actually extremely good at putting down on paper what he saw.
33:49Cajal's passion for art was coupled with a fascination for a new technology.
33:56Photography.
33:58This is the sort of camera that Cajal would have used.
34:00I've got it lined up on the mountains now.
34:03I've got a photographic plate in here, which is basically a bit of glass with some photosensitive chemicals on.
34:10And then you lift this.
34:13And you trigger the shutter.
34:16Should take about 20 seconds.
34:19When that's done, this goes down and the glass plate you take away with you, off to the mysteries of the darkroom.
34:25It was his twin passions, art and photography, that would shape his most important discovery.
34:38What it is that makes the brain work.
34:40To see, observe and make things visible is one of the great challenges of science.
34:51The challenge for neuroscientists was uncovering the fine structure of the brain.
34:57The task Cajal set himself was to reveal the communication networks that exist inside our heads.
35:07I've come to the Cajal Institute to see how he did it.
35:14I always feel like I'm getting into surgery again.
35:18Great. So, mouse?
35:22Yeah, tricky to brain.
35:24My first job is to chop up a rather slippery mouse brain.
35:28Very small.
35:30Hey.
35:32It's trickier than it looks.
35:34There we go.
35:35It's like cutting onions.
35:38Yes, at one point.
35:39I'm good at cutting onions.
35:40Yeah.
35:45The search was on for a stain that would make the mysterious structure of the brain visible under the microscope.
35:55Cajal was shown a technique using chemicals from the darkroom.
36:00Chemicals that could make brain tissue turn black.
36:04You can see it's a really complicated process.
36:07Lots of different stages.
36:10Cajal spent nearly 20 years fiddling away, doing minor adjustments, just seeking perfection.
36:17The great debate was whether the brain was just a mesh of fibres or made of distinct individual units.
36:27Placing stained tissue under the microscope, Cajal became convinced that there were individual building blocks in the brain.
36:44Neurons.
36:45Neurons.
36:46Neurons.
36:47Neurons.
36:48Neurons.
36:50Neurons.
36:51Now that is absolutely beautiful.
36:57That is a neuron.
36:59That is what they were looking for.
37:01Now, the signal goes up here into the cell body and then somehow gets distributed by thousands of axons and dendrites, linking with all the other neurons in the brain.
37:12in the brain now only about 1 in 40 of the neurons actually get stained and
37:17appeared and that might sound like a bad thing but it's actually an incredibly
37:21good thing because if all the neurons here were stained then this would be a
37:25confusing mass you wouldn't be able to make any sense at all because it's just
37:291 in 40 you can pick them out
37:33you can see Cahal's artistic influence here beautiful drawings of neurons
37:46he mapped out groups of neurons and theorized how they might work
37:57that nerve impulses travel along them in one direction passing from one cell to the next
38:07many years later his theories would be confirmed
38:14Cahal realized that these neurons are the basic units of the human brain we now know there are at
38:23least 100 billion of them and all these connecting branches well there are trillions of connections
38:28and somewhere in here emotion and thought are born somewhere in here is the answer to what makes a
38:38human
38:53half a century later the world descended into chaos
39:01out of the turmoil of world war ii came a secret invention built here at bletchley park in rural
39:10England
39:10Colossus
39:16the most complex machine that had yet been built
39:19designed to crack enemy codes it would also shed light on the question of who we are
39:27what was truly astonishing about Colossus was the speed at which it could work enemy messages which
39:36had previously taken teams of human code breakers six weeks to crack could now be done by the machine
39:42in six hours it must have seemed truly superhuman
39:50here was a machine doing something that till now only the intelligent human mind could do but much faster
39:58once again the technology of the day offered a model for how the brain might work
40:06when you think about it it's a bit like a primitive brain with the valves representing the neurons and the wiring
40:16representing the connecting axons and dendrites
40:19people had begun to theorize that kahao's neurons worked a bit like electronic switches
40:36if intelligence could be replicated by the on-off switching of a machine
40:41perhaps the reasoning mind wasn't as uniquely human as we thought
40:50one of the biggest human brains at bletchley was alan turing often called the father of modern computing
40:58in 1950 he thought of an ingenious way of judging whether computers show some form of intelligence by
41:05devising a test
41:09the turing test is actually more of a turing question the question he asked himself was would
41:15it be possible to build a computer that was so intelligent and so good at having chats with humans
41:22that you could be chatting to the machine and not be aware that you're not actually talking to another
41:27person well he suggested that by the year 2000 we would have cracked the problem we are well beyond that
41:34point let's see right what is your name you don't remember no i don't remember
41:46i'm plugged into one of the more sophisticated programs designed to respond to turing's challenge
41:53okay let's try some general knowledge i mean computers should be able to do general knowledge
41:58it doesn't ever seem to really answer the question anyway this is garbage let's try a different tack
42:08favorite films transformers 2 maybe that is some sort of computer joke i can't believe anybody liked
42:16transformers 2 what films make you cry science fiction and comedies what do you like right it's not very
42:30impressive i've not enjoyed myself i'm not having a great conversation here
42:37i think what you can learn from this is that computers are good at computing basically crunching
42:42numbers and things like that what they clearly lack is the thing that really gives any form of human
42:49interchange any worth any value feelings like humor warmth love affection any of the things that we
42:57actually value perhaps too much to expect from a machine bye bye
43:04for centuries technology has provided metaphors to explain who we are the computer is simply the latest
43:18we have seized on but its failings reveal that what makes us human lies in something a machine cannot do
43:25we are passionate irrational creatures often driven by forces we do not understand
43:47at the turn of the 20th century a great nation was coming of age
43:55the united states the land of the free personal rights and liberties
44:19this was the perfect home for the thriving discipline that focused on ourselves as individuals
44:25as well as individuals who have been living in the world
44:27psychology
44:35psychology as the name implies originally started out as the study of the psyche or mind the idea was
44:42you could look into yourself introspect and learn about human nature that way however here in america
44:48a small group of psychologists soon decided that was nowhere near rigorous or vigorous enough
44:55they wanted to turn psychology into a science so they decided to focus on something they really could
45:01measure and manipulate behavior
45:12this approach called behaviorism was transformed into a systematic science by one of the 20th century's
45:18most controversial pioneers his name was bf skinner
45:27skinner was convinced that our behavior is the product of our environment learnt from our experiences
45:39since skinner thought that environment was all important i thought it would be quite interesting to
45:43have a look at where he worked this is his study isn't it wonderful
45:52this is completely unchanged from when he died over 20 years ago
45:58he liked music so he had this adapted so he could just pull that
46:04and play his music this is a man who likes to tinker and adjust things
46:15this is the bed in which he used to sleep it is absolutely filled with his paraphernalia
46:21it was his passion for gadgets for things that he could adapt and change that led him to his greatest
46:32invention a device which is as iconic to behaviorists as the telescope is to astronomers the operant
46:40conditioning chamber or skinner's box
46:42skinner's experiments would reveal something surprising and very disturbing about the human condition
46:58this is an operant chamber otherwise known as skinner box
47:02many people in my field still dr robert allen uses similar methods to those skinner used
47:07is an area where the pigeon stands uh there are response keys the pigeon has to peck on these
47:13buttons if it pecks them in the right order it gets a reward so what are you going to do to impress
47:20me with a pigeon today i'll show you okay let's go get a pigeon
47:26who's this one this is g21 g21 i don't think of pigeons as being smart i must admit they're very smart
47:33is he going to demonstrate just how smart indeed okay in you go g21 okay
47:41hungry yeah it looks like
47:46the pigeon has to work out whether the center light shines red or green for longest
47:53if it's green it has to peck the button on the right oh he's smart long green means go right okay
48:01so will he go right yes he will you're confident in your bird don't you i am very confident
48:08if it was red that was longest he has to go the other way now he has to go left okay watch
48:15yes he's done it he's very good i have to say i'm good at predicting
48:20well done g21 go boy go
48:22what these experiments showed was how easily behavior could be learned even manipulated
48:36i was about to see how quickly this can happen
48:40we are going to shape the turning response by delivering reinforcers for his approximate
48:49behavior you're going to make him sort of turn in circle that's correct better said
48:56each time the pigeon turns left dr allen delivers food to reinforce that behavior
49:03until after just 20 minutes he has the pigeon dancing round in circles
49:08pigeons and bird seed may not look controversial but what was so shocking at the time
49:17was that skinner applied his ideas to human behavior
49:25what skinner was saying is that we are in many ways like pigeons that we are the product of the
49:30numerous interactions we have with our environment whether it's falling in love the job the friends
49:36you make all these things which appear to be decisions are actually the product of things that have
49:41happened to us in the past we can no more exercise free will than this pigeon can decide whether
49:47to peck or indeed turn in a circle skinner was convinced his discovery could be used to benefit mankind
50:00we could change people's behavior by changing their environment
50:13but in the context of the cold war the ability to control behavior left some people fearful it could be
50:20misused because in skinner's view free will was nothing but an illusion
50:30now most of us believe that being able to make choices is an important part of being human
50:36but here was skinner saying that that was an illusion that actually it was a piece of pre-scientific
50:42nonsense akin to believing in a flat earth or demonic possession you can imagine how popular that
50:48message was in the land of the free and the rugged individual
50:52behaviorism was soon joined by other approaches through the 1960s and beyond
51:04there were new drugs therapies personality tests new ways to measure our thoughts memories and emotions
51:14psychology has grown into a vast science as diverse and multifaceted as we are
51:22so who are we
51:33well we are the product of our genes and our environment
51:46billions of neurochemical reactions firing every single second of our lives
51:52in us reason and emotion are frequently at war
52:03thoughts passions memories and behavior emerge unbidden out of the depths
52:10brain scans reveal many parts of the brain operating outside our conscious awareness
52:15we are the product of numerous daily interactions
52:35and the quest to understand the essence of who we are
52:38we are has revealed something fascinating going on inside our heads
52:43something none of us are ever aware of
52:48i can show you what i mean with a famous visual illusion
52:52it's called the aims room that is so bizarre
53:05clearly what i'm seeing is i'm seeing a very very tall person over there and a short person over there
53:13and when they swap over there's a moment where my brain just goes clunk
53:19i absolutely know this is an illusion but my brain just won't let me see through the illusion
53:24so how's it done well if you come over this way it's really obvious hi there thank you
53:39okay so essentially the room really dips down here lots of space above my head there is a sharply sloping
53:46floor floor as i march up the room begins to narrow until i'm really crunched into the corner
53:53there's very little space between the ground and the top here and that's how
53:57the illusion is created essentially the room is a trapezoid
54:07the ames room shows us something very important about how the brain is working
54:11part of my brain which knows the rules of a room it has assumptions models built in there and it
54:20knows based on experience the normally rooms the ceiling and the floor is parallel and that the walls are at right angle
54:32from one particular viewpoint the room looks like it fits that mental model and the brain has such a
54:38powerful belief that this quirky shaped room is normal that people appear to have changed size
54:47this illusion reveals something fundamental about how the brain works
54:54our perception of reality is not just based on what is out there but it is also partially constructed
55:01we have these models running in our head and they are constantly being tested against the evidence
55:08of our senses
55:17this process of building models in our heads is happening from the moment we are born
55:24this child is using her senses to find out about the world
55:28is that person in the mirror and now the baby or is it me why does that thing make a noise when i shake it
55:41what she's doing is constantly learning by testing everything around her
55:46thousands of little experiments like these will create her unconscious assumptions
55:57they'll build the models that shape her view of the world
56:01that's how she will be able to make her way through life
56:04it is very charming when you think that in a way what she's doing now is acting rather like a mini scientist
56:17she's investigating the world she's forming her theories her hypotheses and she's testing them against reality
56:25and that in a sense is what science is and it's going on inside each and every one of us from the moment we are born
56:35is that right chloe is that right it is
56:44in this program we've seen that humans are creatures of both rational thought
56:51and emotional turmoil
56:53and in this series i've shown how science too has been shaped by reason and emotion
57:03as well as by the tumult of the world in which it operates
57:09its intellectual achievements have transformed our lives
57:13but it hasn't been straightforward the story of science is a messy one wrapped up in politics belief
57:30money and rivalry proof forever shaped by power and passion
57:35science is a very human activity
57:44something we unconsciously do every day
57:49observing the world building mental models and testing them
57:55but it's when we deliberately started using the scientific method
57:59that we went way beyond our individual capabilities
58:02we went way beyond our individual capabilities
58:05i think science is the greatest collective endeavor that mankind has ever undertaken
58:18over the last few thousand years the human brain has not changed at all
58:23evolution does not go that fast but what has changed is our understanding of the world
58:28we don't have to rely simply on the wisdom of our own brain
58:34we have language we have literature and now we have computers and that links us all together that
58:41gives us if you like the wisdom of all those who have gone before
58:49and that was the final part of the story of science catch up with the junior apprentices at nine
58:54tomorrow here on bbc hd but next tonight stay with us for drama in crash
59:16you