0:00:05 > 0:00:09Inside each and every one of us is the most marvellous
0:00:09 > 0:00:14and complicated object in the known universe - the human brain.
0:00:15 > 0:00:19This great big blancmange of hardware is responsible for
0:00:19 > 0:00:24everything from our personality to our potential,
0:00:24 > 0:00:27but have you ever used to your brain to wonder
0:00:27 > 0:00:30why don't men ask for directions?
0:00:30 > 0:00:32Why are zombies scary?
0:00:32 > 0:00:34And can I trust my brain?
0:00:36 > 0:00:40Join me as we venture deep inside the landscape of your mind
0:00:40 > 0:00:46to discover the things you need to know about the human brain.
0:00:47 > 0:00:49Starting with...
0:00:52 > 0:00:56Well, according to Aristotle, you don't really use it at all.
0:00:56 > 0:00:59He thought it was just a radiator for keeping us cool.
0:00:59 > 0:01:04But modern science now knows that even though it looks like a wobbly walnut,
0:01:04 > 0:01:07you use all of your brain all of the time.
0:01:07 > 0:01:10In fact, even though it's only 2% of your body mass,
0:01:10 > 0:01:15this machine devours nearly a quarter of your energy.
0:01:15 > 0:01:18To only use 10% of its capability
0:01:18 > 0:01:23would be like buying a Sherman tank for the school run.
0:01:24 > 0:01:29This idea that we only use 10% has been perpetuated
0:01:29 > 0:01:33by some psychics and self-help gurus for many years.
0:01:33 > 0:01:36They claim that the untapped 90% is where
0:01:36 > 0:01:39we will find our superhuman powers.
0:01:39 > 0:01:41However...
0:01:45 > 0:01:46..it simply isn't true.
0:01:46 > 0:01:50It would be madness if we only used 10% of our brains.
0:01:50 > 0:01:53Our brains have evolved for some reason to be the size that they are.
0:01:53 > 0:01:57Our brains are huge and they're extremely complex.
0:01:57 > 0:02:00And in fact, it's dangerous that they're the size that they are.
0:02:00 > 0:02:02We're a species where childbirth can be very, very dangerous
0:02:02 > 0:02:05and that is because of the size of the baby's head.
0:02:05 > 0:02:07I did a first aid course about 15 years ago
0:02:07 > 0:02:10and it was taught on the course that head injuries aren't serious
0:02:10 > 0:02:12because we only use 10% of our brains.
0:02:12 > 0:02:15And I was thinking, "What?!" I mean, this is incredible.
0:02:15 > 0:02:18This was being said by somebody who was standing up and talking,
0:02:18 > 0:02:20knowing his name, breathing,
0:02:20 > 0:02:23all of that being made possible by his brain working extremely hard.
0:02:23 > 0:02:29Right now, your brain is powering 100 billion neurons.
0:02:29 > 0:02:34There's over 100,000 miles of this electric spaghetti at work
0:02:34 > 0:02:39in your brain, enough to go around the world four times.
0:02:39 > 0:02:42Even the simple act of drinking tea
0:02:42 > 0:02:44creates a lightning storm of activity.
0:02:44 > 0:02:48But first, you need to know what tea is.
0:02:48 > 0:02:54So your hippocampus calls up old memories of drinking tea.
0:02:54 > 0:02:58Then your visual cortex cleverly picks out the cup from the saucer,
0:02:58 > 0:03:02before your motor cortex lifts the cup to your mouth.
0:03:02 > 0:03:04Mmm!
0:03:04 > 0:03:07And while these bits of your brain are enjoying a tea break,
0:03:07 > 0:03:11the rest of your brain is hard at work supporting these neurons.
0:03:11 > 0:03:14We tend to think that the brain is made up of neurons,
0:03:14 > 0:03:17which are the brain cells that do all the work in your brain.
0:03:17 > 0:03:20But actually the vast majority of cells in your brain are glial cells
0:03:20 > 0:03:23and they are there to support the neurones.
0:03:23 > 0:03:25It's like the neurones are thoroughbreds
0:03:25 > 0:03:27and they need a whole team of people to look after them.
0:03:27 > 0:03:31So, there's an underlying army of cells that provide insulation,
0:03:31 > 0:03:36food and protection, and sweep up dead neurons.
0:03:36 > 0:03:40All in, you have about one trillion brain cells.
0:03:40 > 0:03:42In fact, there are more cells in your head,
0:03:42 > 0:03:45than there are stars in the entire galaxy.
0:03:45 > 0:03:49So, we're already using the entire brain,
0:03:49 > 0:03:52but what if we fancy a bit of an upgrade?
0:03:52 > 0:03:55How can we get more out of what we've got?
0:03:55 > 0:03:57How can I boost my brain?
0:03:58 > 0:04:02You can train your body, but is there a workout for your brain?
0:04:02 > 0:04:04Before you invest in the latest
0:04:04 > 0:04:08brain-training games by Dr Do-Very-Little,
0:04:08 > 0:04:11you might want to consider this recent research
0:04:11 > 0:04:13from the University of Cambridge.
0:04:13 > 0:04:15They took eight scientists, 12 brain-training games
0:04:15 > 0:04:21and over 11,000 volunteers through a six-week mental workout,
0:04:21 > 0:04:26and found no improvement to intelligence whatsoever.
0:04:26 > 0:04:30Another myth is the so-called Mozart effect.
0:04:30 > 0:04:34This is the idea that by listening to the musical genius you will
0:04:34 > 0:04:36somehow boost your own brilliance,
0:04:36 > 0:04:39and you do, but only by a very tiny amount
0:04:39 > 0:04:41and it only lasts for about 15 minutes.
0:04:41 > 0:04:46So you'd probably get the same effect by having a nice cup of tea.
0:04:46 > 0:04:49It's been shown that this can work with all sorts of music,
0:04:49 > 0:04:50it hasn't got to be Mozart.
0:04:50 > 0:04:54Basically, you can boost your brainpower with certain sorts of tasks
0:04:54 > 0:04:58for about 15 minutes with the U2 effect, the Blur effect, whatever you like.
0:04:58 > 0:05:01You can do it with music cos music just basically energises you a bit.
0:05:01 > 0:05:03There's nothing special about Mozart.
0:05:04 > 0:05:08But there is one way to get maximum brain gain.
0:05:09 > 0:05:12Playing any musical instrument,
0:05:12 > 0:05:14even the drums.
0:05:14 > 0:05:17You see, your brain is a bit like plasticine.
0:05:17 > 0:05:20It's shaped and moulded by the things you do.
0:05:20 > 0:05:23Musicians have more connections between the two sides.
0:05:23 > 0:05:28They've got bigger cerebellums and up to 130% more grey matter.
0:05:28 > 0:05:32And that's because intense concentration and co-ordination
0:05:32 > 0:05:34physically improves the brain.
0:05:34 > 0:05:37Learning to play a musical instrument basically involves
0:05:37 > 0:05:39activity throughout the entire brain,
0:05:39 > 0:05:42getting all different brain areas talking to each other.
0:05:42 > 0:05:46Playing music can change your brain because there's this neuroplasticity,
0:05:46 > 0:05:51we form new brain connections when you do something like, say, learn to play piano.
0:05:51 > 0:05:54It's essentially the perfect work-out for the brain.
0:05:54 > 0:05:57But before you dust off that saxophone, there's something you should know.
0:05:57 > 0:06:02It takes about 10,000 hours to become an expert in something.
0:06:03 > 0:06:08And your plasticine brain starts to stiffen as you get older.
0:06:08 > 0:06:11But there is another way to boost your brain,
0:06:11 > 0:06:13and you don't have to start young.
0:06:13 > 0:06:17London cabbies are required to learn 25,000 streets
0:06:17 > 0:06:20within a six-mile radius of Charing Cross.
0:06:20 > 0:06:24Some scientists got under their bonnets with a brain scanner,
0:06:24 > 0:06:28and they found their memory centre was actually bigger.
0:06:28 > 0:06:32The hippocampus had grown to accommodate all that extra knowledge.
0:06:32 > 0:06:36But they still have trouble working out the correct change.
0:06:39 > 0:06:45So, those London cabbies have a natural advantage when it comes to navigation.
0:06:45 > 0:06:49But what about the rest of us? How do we get from A to B?
0:06:49 > 0:06:51And more importantly...
0:06:54 > 0:06:59Navigation doesn't come easily to human brains,
0:06:59 > 0:07:02or indeed jellyfish, who haven't got any.
0:07:02 > 0:07:07No, nature's great navigator is the Arctic Tern.
0:07:07 > 0:07:12They clock up an incredible 44,000 air miles every year.
0:07:12 > 0:07:16Their tiny brains contain biomagnetite,
0:07:16 > 0:07:19which can sense the earth's magnetic field.
0:07:19 > 0:07:22A bit like having a compass in your own head.
0:07:22 > 0:07:24Humans don't have that luxury.
0:07:24 > 0:07:27But we're not all slaves to sat nav just yet.
0:07:27 > 0:07:32Some trends suggest that men and women have developed different ways of getting about
0:07:32 > 0:07:35and it might be down to the way we use our brains.
0:07:36 > 0:07:41Now, if you've ever been in a car with a member of the opposite sex,
0:07:41 > 0:07:43I'm sure you'll agree we have
0:07:43 > 0:07:47very different opinions about which way to go.
0:07:47 > 0:07:50So, you're off on a trip, in a race to the airport.
0:07:50 > 0:07:54It's thought that women tend to use each brain hemisphere equally,
0:07:54 > 0:07:57making them better at language.
0:07:57 > 0:08:01They like to navigate using landmarks that can be described.
0:08:01 > 0:08:05Go past the big clock and turn left at the shoe shop.
0:08:05 > 0:08:09However, research suggests that men tend to use their right brains more.
0:08:09 > 0:08:11It's slightly bigger than the left
0:08:11 > 0:08:13and isn't really interested in talking,
0:08:13 > 0:08:18preferring instead to create a 3D model of the surroundings.
0:08:18 > 0:08:21Men tend to be much better than women on visuospatial
0:08:21 > 0:08:25and navigation tasks, such as rotating 3D objects in your head,
0:08:25 > 0:08:30wayfinding on maze tasks and also other mental rotation tasks.
0:08:30 > 0:08:34Men think about places as points on a compass.
0:08:34 > 0:08:36They just want to head south.
0:08:36 > 0:08:38So, who's right?
0:08:38 > 0:08:41The female method would be more efficient.
0:08:41 > 0:08:45Using landmarks, you might get to your destination quicker,
0:08:45 > 0:08:47and with fewer wrong turns.
0:08:47 > 0:08:49That is until the sun goes down.
0:08:49 > 0:08:52Unable to see the landmarks, you've had it,
0:08:52 > 0:08:55although there is some doubt about this theory.
0:08:55 > 0:08:56It's pretty controversial.
0:08:56 > 0:08:59You can see these differences, but they tend to be trends
0:08:59 > 0:09:01and sometimes we read more into these trends,
0:09:01 > 0:09:04maybe because we want there to be interesting differences.
0:09:04 > 0:09:07If you get a load of people to do some visuospatial tasks,
0:09:07 > 0:09:11then 75% of the people who do really, really well on them will be male.
0:09:11 > 0:09:16But that doesn't mean that there aren't some women who are really, really good at it, as well.
0:09:16 > 0:09:20So, why don't men ask for directions?
0:09:20 > 0:09:22Because we're not lost.
0:09:22 > 0:09:24Even when we are.
0:09:28 > 0:09:29Hiya!
0:09:29 > 0:09:32We humans really are clever, aren't we?
0:09:32 > 0:09:37We're able to represent three-dimensional space in our mind's eye,
0:09:37 > 0:09:41manipulate it and then use it to travel over really long distances,
0:09:41 > 0:09:44which sort of leads to an interesting question...
0:09:47 > 0:09:52Your brain will do practically anything to keep your body alive.
0:09:52 > 0:09:54However, for a lot of life's problems,
0:09:54 > 0:09:56it's only got one answer.
0:09:56 > 0:09:59Food poisoning - vomit.
0:09:59 > 0:10:02You're pregnant - vomit.
0:10:02 > 0:10:05Even a bumpy road - you guessed it, puke city.
0:10:07 > 0:10:11Vomiting is your body's answer to quite a lot of problems.
0:10:11 > 0:10:15Bangs on the head, ingested poisons, vomiting is the answer.
0:10:15 > 0:10:20It's your body trying to get rid of things it thinks could be causing the problem,
0:10:20 > 0:10:22things that might be poisoning you.
0:10:22 > 0:10:28The trouble is your brain is sometimes wrong, and here's why.
0:10:28 > 0:10:33Buried deep inside your inner ear, you've got a motion detector.
0:10:33 > 0:10:36It's called the vestibular system and it's basically
0:10:36 > 0:10:40three fluid-filled chambers full of microscopic hairs.
0:10:41 > 0:10:45When you move, the fluid sloshes about.
0:10:45 > 0:10:49It bends the hairs to let your brain know which way you're going.
0:10:50 > 0:10:54So, as you bounce along in the back of a car,
0:10:54 > 0:10:58the fluid in your inner ear is splashing about,
0:10:58 > 0:11:00but your eyes tell a different story.
0:11:00 > 0:11:02Seeing the inside of a car,
0:11:02 > 0:11:04they think your body is completely stationary.
0:11:05 > 0:11:10Your brain can't agree on what you feel and what you see,
0:11:10 > 0:11:15so it jumps to the only logical conclusion - you've been poisoned.
0:11:15 > 0:11:18Your brain heroically steps in to save the day.
0:11:18 > 0:11:23It tells your stomach to contract, forcing its contents back out.
0:11:23 > 0:11:26Try explaining that to the owner of the car.
0:11:26 > 0:11:28Something that really seems to help with travel sickness
0:11:28 > 0:11:31is to be able to look at some fixed point like the horizon
0:11:31 > 0:11:32or something far in front of you.
0:11:32 > 0:11:34This seems to be why drivers don't get sick,
0:11:34 > 0:11:37because that's what they're doing when they drive.
0:11:37 > 0:11:42It's not just car travel that affects your vestibular system.
0:11:42 > 0:11:45A similar thing happens when you drink too much.
0:11:45 > 0:11:47Alcohol is a bit of a sly one.
0:11:47 > 0:11:50Its tiny molecules sneak into your inner ear.
0:11:50 > 0:11:54It's much lighter than water, thinning the fluid,
0:11:54 > 0:11:57causing it to become massively over-sensitive.
0:11:58 > 0:12:01The result is the dreaded spin,
0:12:01 > 0:12:03and more vomit.
0:12:06 > 0:12:09That's the annoying thing about alcohol - once you've had a few,
0:12:09 > 0:12:12you're too drunk to remember that you've already had enough.
0:12:12 > 0:12:17But what if your memory's already a bit random even without the booze?
0:12:17 > 0:12:18Or to put it another way...
0:12:21 > 0:12:26So, you're at the office party and you've just met your dream girl.
0:12:26 > 0:12:30But there's a problem - you've already forgotten her name,
0:12:30 > 0:12:32and everyone else's.
0:12:32 > 0:12:35Don't worry, you're not losing your marbles,
0:12:35 > 0:12:37just your chance of a date.
0:12:37 > 0:12:41When you meet someone for the first time, there is so much activity
0:12:41 > 0:12:44going on in the brain to do with governing that social interaction.
0:12:44 > 0:12:47It's all about "What am I going to say next?
0:12:47 > 0:12:49"What are they going to think of me?"
0:12:49 > 0:12:52The last thing you're thinking about is the person's name,
0:12:52 > 0:12:54so of course you forget it.
0:12:54 > 0:12:55Making memories is tricky.
0:12:55 > 0:12:59Your neurons have to forge new connections.
0:12:59 > 0:13:01If you remembered everything you heard,
0:13:01 > 0:13:04you'd soon run out of brain space.
0:13:04 > 0:13:07So your mind deliberately makes it hard.
0:13:07 > 0:13:10First, you have to get through your working memory,
0:13:10 > 0:13:13which is constantly being rewritten
0:13:13 > 0:13:16because it can only hold about seven things.
0:13:16 > 0:13:20That's why it's hard to remember anything longer than a phone number.
0:13:20 > 0:13:21But, if important,
0:13:21 > 0:13:26it gets stored in your long-term memory by your hippocampus.
0:13:26 > 0:13:28Usually, though, there's no logic to names,
0:13:28 > 0:13:31which makes them hard to keep hold of.
0:13:33 > 0:13:36Names can be difficult because they can be so arbitrary,
0:13:36 > 0:13:38because there's not necessarily meaning to help you.
0:13:38 > 0:13:42So here's a John. Well, there's not necessarily anything Johnish about John.
0:13:42 > 0:13:44There could be lots of Johns,
0:13:44 > 0:13:47they won't necessarily have anything in common with each other.
0:13:47 > 0:13:50So all you've got to go on is to remember the link itself.
0:13:50 > 0:13:52There's nothing else to help you.
0:13:53 > 0:13:56Now, if this new girl's name was King Kong,
0:13:56 > 0:13:59and she looked like a massive gorilla,
0:13:59 > 0:14:02then she'd be almost impossible to forget.
0:14:02 > 0:14:04Luckily, she's not.
0:14:04 > 0:14:05But you get the idea.
0:14:05 > 0:14:11So to help, you need hold on tight to new names by repeating them to yourself, over and over.
0:14:11 > 0:14:14But remembering Anne is only half the battle.
0:14:14 > 0:14:16You then you need to find her name again,
0:14:16 > 0:14:19and your brain is like a messy bedroom,
0:14:19 > 0:14:22with memories scattered all over the place.
0:14:22 > 0:14:23However, there is a trick.
0:14:23 > 0:14:26You can create a "memory palace".
0:14:26 > 0:14:30To do this, you link new names with the memories you've already got,
0:14:30 > 0:14:33like objects around your home.
0:14:33 > 0:14:35So, to remember Anne, give her a spray tan,
0:14:35 > 0:14:38and mentally put her in the back of your van.
0:14:38 > 0:14:41By creating this rich visual imagery,
0:14:41 > 0:14:43your neurons make more connections
0:14:43 > 0:14:47and you might stand a chance of getting that date after all.
0:14:56 > 0:15:01As well as being good for remembering names and places,
0:15:01 > 0:15:03your brain has a dark side,
0:15:03 > 0:15:07because it controls one of our most automatic responses...
0:15:09 > 0:15:10..fear.
0:15:10 > 0:15:13So, why are zombies scary?
0:15:15 > 0:15:18If you didn't fear things, you wouldn't live for very long.
0:15:18 > 0:15:22You'd forever be walking into oncoming traffic
0:15:22 > 0:15:25or picking fights with tigers.
0:15:25 > 0:15:29And evolution prefers the activities that keep you alive
0:15:29 > 0:15:34by staying well away from the brain-hungry reanimated undead.
0:15:34 > 0:15:36But how does fear work?
0:15:36 > 0:15:40If there's a sudden bang, even newborn babies will jump,
0:15:40 > 0:15:43and this is the startle reflex that they're born with.
0:15:43 > 0:15:46Fear is something that's so crucial to all of us.
0:15:46 > 0:15:49So, if you hear an almighty crash,
0:15:49 > 0:15:51you'll jump.
0:15:51 > 0:15:55The sound goes straight to your amygdala,
0:15:55 > 0:15:57the emotional part of your brain.
0:15:57 > 0:15:58It's a bit trigger-happy,
0:15:58 > 0:16:02and initiates your fear response without really knowing the score.
0:16:02 > 0:16:05This sends your brain into overdrive,
0:16:05 > 0:16:07releasing up to 30 different hormones
0:16:07 > 0:16:10that cause a physiological response,
0:16:10 > 0:16:14so your pupils dilate to let in more light.
0:16:14 > 0:16:19Your digestions shuts down and saliva production grinds to a halt.
0:16:19 > 0:16:21Your mouth goes dry.
0:16:21 > 0:16:25Rapid breathing sends more oxygen into your bloodstream.
0:16:25 > 0:16:28Your heart beats faster and veins constrict,
0:16:28 > 0:16:31forcing blood and more energy to your arms and legs.
0:16:31 > 0:16:35And all this happens in just one fifth of a second,
0:16:35 > 0:16:39before you're even consciously aware of what's going on.
0:16:41 > 0:16:44Meanwhile, as the shuffling silhouette comes into focus,
0:16:44 > 0:16:47the pictures get beamed to your visual cortex.
0:16:47 > 0:16:50Your hippocampus flicks through your memory bank
0:16:50 > 0:16:53and finds all those old horror films.
0:16:53 > 0:16:58You correctly recognise the unidentified intruder as "zombie".
0:16:59 > 0:17:01The really scary thing about zombies
0:17:01 > 0:17:03is that they're a little bit too like us.
0:17:03 > 0:17:06But we know deep down that they're fundamentally different.
0:17:06 > 0:17:09They're revolting, but they are very human at the same time.
0:17:09 > 0:17:11They're not really there.
0:17:11 > 0:17:14There's some absence of humanity behind the eyes.
0:17:14 > 0:17:15There's something missing.
0:17:15 > 0:17:17So, your amygdala was right.
0:17:17 > 0:17:23Finally, you're ready to fight for your life or to run like hell.
0:17:23 > 0:17:25But there's no rush.
0:17:25 > 0:17:28All this happened in just a fifth of a second,
0:17:28 > 0:17:29and zombies are slow.
0:17:33 > 0:17:35Fortune may favour the brave,
0:17:35 > 0:17:40but evolution definitely favours those who keep out of trouble.
0:17:42 > 0:17:43And to help you with this,
0:17:43 > 0:17:46your brain has another trick up its sleeve - pain.
0:17:48 > 0:17:50But have you ever wondered...
0:17:53 > 0:17:59Sphenopalatine ganglioneuralgia to give its scientific name,
0:17:59 > 0:18:02characterised by a sharp pain to the forehead
0:18:02 > 0:18:06while having an ice cream or very cold drink.
0:18:06 > 0:18:09But first things first. What is pain?
0:18:09 > 0:18:11Your average Egyptian thought
0:18:11 > 0:18:14it was caused by spirits getting in through his nostrils.
0:18:14 > 0:18:18So he sported a nose ring, not for fashion,
0:18:18 > 0:18:21but to ward off the evil apparitions.
0:18:21 > 0:18:23Science didn't catch up until 1906,
0:18:23 > 0:18:27when the first pain receptor was discovered.
0:18:27 > 0:18:32And it turns out there's an army of up to 80,000 of them beneath your skin.
0:18:32 > 0:18:35When disturbed, they send word to your cortex,
0:18:35 > 0:18:38which registers the source of the attack.
0:18:38 > 0:18:42It's your body's way of telling your brain that you're in danger.
0:18:42 > 0:18:46Believe it or not, pain is actually a good thing
0:18:46 > 0:18:49because it alerts you to potential sources of harm.
0:18:49 > 0:18:54So, what's so dangerous about tucking into a rum and fudge sundae?
0:18:54 > 0:18:57Well, when the cold stuff hits the roof of your mouth,
0:18:57 > 0:19:00the tiny blood vessels contract so rapidly,
0:19:00 > 0:19:02a small pain message is sent to your brain.
0:19:02 > 0:19:06But the message intersects with an eight-lane mega-highway,
0:19:06 > 0:19:08running from your forehead.
0:19:08 > 0:19:10By the time it's arrived at your cortex,
0:19:10 > 0:19:13your brain thinks it's come from all over your head,
0:19:13 > 0:19:16and that's where you feel the crippling pain.
0:19:16 > 0:19:19Pain is a really interesting sensation
0:19:19 > 0:19:21because it's highly subjective.
0:19:21 > 0:19:25So, you could be either picking up a kettle and it's really, really hot.
0:19:25 > 0:19:26If it's empty you'll drop it.
0:19:26 > 0:19:29If you're picking up a kettle that's full of boiling water,
0:19:29 > 0:19:31and it's really, really hot,
0:19:31 > 0:19:33you'll place it back down rather than drop it,
0:19:33 > 0:19:36because hurling boiling water all over yourself would be worse.
0:19:36 > 0:19:39So, how best to deal with pain?
0:19:39 > 0:19:42Scientists think swearing might be the answer.
0:19:42 > 0:19:46When given permission to shout a four-letter word of your choice,
0:19:46 > 0:19:49you can withstand pain for up twice as long.
0:19:52 > 0:19:53But the people around you
0:19:53 > 0:19:57might prefer it if you just took a couple of aspirin instead.
0:20:02 > 0:20:05You don't need to go far to find a painkiller.
0:20:05 > 0:20:09Inside your brain is a private pharmacy making its own.
0:20:09 > 0:20:11They're called endorphins.
0:20:11 > 0:20:16But there's one human activity that generates even more brain chemicals than this -
0:20:16 > 0:20:18love.
0:20:20 > 0:20:24Plato thought he knew a thing or two about love.
0:20:24 > 0:20:29He reckoned that men and women were originally joined together.
0:20:29 > 0:20:33A super-being with four arms and two heads,
0:20:33 > 0:20:35we tried to overthrow the gods.
0:20:35 > 0:20:39But they didn't take kindly to that sort of thing,
0:20:39 > 0:20:41so Zeus split us in two
0:20:41 > 0:20:45and we've been trying to get back together ever since.
0:20:45 > 0:20:49A nice story perhaps, but the truth is far more powerful.
0:20:50 > 0:20:52When it comes to love,
0:20:52 > 0:20:56we are completely at the mercy of our brain's biochemistry.
0:20:56 > 0:20:59Wait till you get a load of these guys.
0:20:59 > 0:21:04Cupid's arrow comes dipped in a heady cocktail of brain chemicals.
0:21:04 > 0:21:07They are literally addictive, like cocaine,
0:21:07 > 0:21:12and they work in three different stages throughout the course of your life.
0:21:12 > 0:21:15Amongst the first is dopamine and testosterone.
0:21:15 > 0:21:18They give you the racing heart, sleeplessness,
0:21:18 > 0:21:22and the butterflies in your stomach when you meet someone you fancy.
0:21:24 > 0:21:27But that's just the warm-up act, lust.
0:21:27 > 0:21:31If you look at the brain chemically in the early stages of love,
0:21:31 > 0:21:34the absolute head-over-heels area of it,
0:21:34 > 0:21:36it's interesting that the levels of serotonin,
0:21:36 > 0:21:39which makes people feel happy, are actually low,
0:21:39 > 0:21:42which is surprising and is what you would see in somebody
0:21:42 > 0:21:44with an obsessive compulsive disorder.
0:21:44 > 0:21:50The second stage of love pushes you head over heels into romantic love,
0:21:50 > 0:21:55and enter the real star of the love parade - oxytocin.
0:21:55 > 0:21:57This is released when you have sex,
0:21:57 > 0:21:59and creates that special bond.
0:21:59 > 0:22:03It's the superglue that holds you together.
0:22:04 > 0:22:07But around three years after your first date,
0:22:07 > 0:22:12dopamine production slows down and the romantic gestures die off.
0:22:12 > 0:22:15The third and final stage of your relationship
0:22:15 > 0:22:18depends on endorphins to keep you together.
0:22:18 > 0:22:20These are your natural painkillers
0:22:20 > 0:22:24and give you that sense of well-being and security,
0:22:24 > 0:22:26potentially for the rest of your life.
0:22:29 > 0:22:33Actually, the frenzied brain activity we see in the lovestruck
0:22:33 > 0:22:36has similarities with mental illness.
0:22:36 > 0:22:38Your brain is driving you mad,
0:22:38 > 0:22:40which leads me to ask...
0:22:46 > 0:22:49Do you see strange things in the corner of your eye,
0:22:49 > 0:22:52or mistake one thing for another?
0:22:52 > 0:22:54Do not adjust your brain!
0:22:54 > 0:22:57There is a problem with reality.
0:22:57 > 0:23:00There's just too much information out there,
0:23:00 > 0:23:03and your brain can't take it all in.
0:23:03 > 0:23:05If it did, your head would be so big,
0:23:05 > 0:23:08your neck couldn't support your expanding cranium.
0:23:10 > 0:23:14So, to make sense of the world, your brain takes a few shortcuts,
0:23:14 > 0:23:17and sometimes it gets it wrong.
0:23:17 > 0:23:23For starters, only 1% of what you see is actually in focus.
0:23:23 > 0:23:25Everything else is a blur.
0:23:26 > 0:23:29Hold your hand out like this.
0:23:29 > 0:23:32Look at the end of your thumb.
0:23:32 > 0:23:36That little bit there represents everything that you can see clearly.
0:23:36 > 0:23:38Everything else is just a blur.
0:23:38 > 0:23:41You can't necessarily trust your brain
0:23:41 > 0:23:45because although the things that you can see and hear can feel real,
0:23:45 > 0:23:50actually the majority of that is your brain filling in all kinds of details all the time,
0:23:50 > 0:23:53because you don't see that much and you don't hear that much.
0:23:53 > 0:23:57In fact, your eyes are constantly on the move,
0:23:57 > 0:24:01so your brain takes snapshots, three per second,
0:24:01 > 0:24:04to build a composite picture, piece by piece.
0:24:04 > 0:24:06It can't capture everything
0:24:06 > 0:24:09so it fills the blanks with memories and guesswork.
0:24:12 > 0:24:13Test it out.
0:24:13 > 0:24:16Take a look at this flashing image.
0:24:16 > 0:24:21Your brain is only taking in the important bits of this scene,
0:24:21 > 0:24:22so things get missed.
0:24:22 > 0:24:24Did you notice the change?
0:24:24 > 0:24:27It's called "change blindness",
0:24:27 > 0:24:32and it proves that you can't take in everything all of the time.
0:24:32 > 0:24:35So, if your eyes are constantly on the move,
0:24:35 > 0:24:38how come the world isn't one big blur?
0:24:38 > 0:24:43Well, your brain cleverly turns your eyes off every time they move,
0:24:43 > 0:24:47leaving you in the dark for 200 milliseconds at a time,
0:24:47 > 0:24:48which adds up.
0:24:48 > 0:24:53For about two hours a day, you are blind.
0:24:56 > 0:24:59One of the reasons we know so much about things such as
0:24:59 > 0:25:04time perception, and memory and fear is because we've been able to study
0:25:04 > 0:25:05those unfortunate people who,
0:25:05 > 0:25:10for one reason or another, have bits of their brains missing,
0:25:10 > 0:25:13and that brings me to my final question...
0:25:17 > 0:25:21There's a very simple way to figure out how important
0:25:21 > 0:25:23certain brain bits are.
0:25:23 > 0:25:26Take a piece out and see what happens.
0:25:27 > 0:25:31You'll quickly discover which sections make you happy...
0:25:33 > 0:25:36..or remember where you live,
0:25:36 > 0:25:39and the bits that know the difference between your dad
0:25:39 > 0:25:41and a daisy.
0:25:41 > 0:25:47But removing perfectly good brain parts to see what happens isn't cool.
0:25:47 > 0:25:50However, that sometimes happened by accident.
0:25:50 > 0:25:54Nowadays, we use brain scanners to understand how the human brain works,
0:25:54 > 0:25:56but up until 20 years ago,
0:25:56 > 0:26:00the only real way we could find out more about what the human brain did
0:26:00 > 0:26:04was by working with patients who had some sort of damage to their brain,
0:26:04 > 0:26:05nature's accidents if you like.
0:26:05 > 0:26:08In 1953, one of those accidents
0:26:08 > 0:26:12left a man unable to make any new memories.
0:26:12 > 0:26:14But, on the upside, this allowed us
0:26:14 > 0:26:19to identify the hippocampus as the bookkeeper to our memory banks.
0:26:19 > 0:26:23But perhaps the strangest story is that of Phineas Gage.
0:26:23 > 0:26:24In 1848, in the USA,
0:26:24 > 0:26:29demolition man Phineas was blasting his way through solid rock,
0:26:29 > 0:26:32making way for a new railroad,
0:26:32 > 0:26:36ramming gunpowder into a hole with an iron bar.
0:26:36 > 0:26:39Health and safety hadn't really taken off yet.
0:26:39 > 0:26:42Unsurprisingly, the gunpowder went off,
0:26:42 > 0:26:45sending the bar straight through his face.
0:26:45 > 0:26:50It landed around 100 feet away, having removed his frontal lobe
0:26:50 > 0:26:51and his inhibitions.
0:26:51 > 0:26:54Talk about a bad day at work.
0:26:54 > 0:26:58According to the records, he sprang back to his feet and vomited,
0:26:58 > 0:27:02which caused even more of his brain to fall out onto the ground.
0:27:02 > 0:27:07Amazingly, he survived, but with dramatic consequences.
0:27:07 > 0:27:11He went from being a nice guy to short-tempered and rude.
0:27:11 > 0:27:13He even lost his job.
0:27:13 > 0:27:14If it wasn't for him,
0:27:14 > 0:27:17we wouldn't have known what this prefrontal cortex does.
0:27:17 > 0:27:21The man goes from being incredibly disciplined,
0:27:21 > 0:27:24reliable individual, to totally socially inept,
0:27:24 > 0:27:28having a conversation, starting to urinate in front of people.
0:27:28 > 0:27:33He was absolutely unable to control his impulsive behavior.
0:27:33 > 0:27:38So, Phineas' personality switch proved, for the first time ever,
0:27:38 > 0:27:42that your grey matter defines who you are.
0:27:42 > 0:27:45In spite of all the wondrous and surprising things
0:27:45 > 0:27:47the human brain can do,
0:27:47 > 0:27:49I think it's fair to say that
0:27:49 > 0:27:53most of us wander around blissfully unaware that we even have one.
0:27:53 > 0:27:57You don't need to know you have a brain.
0:27:57 > 0:27:59It's just there.
0:27:59 > 0:28:02But if you stop and think about it for a second,
0:28:02 > 0:28:07you realise that it's your brain that makes you truly human.
0:28:07 > 0:28:09It makes you you
0:28:09 > 0:28:11and not me,
0:28:11 > 0:28:13and you should be happy about that
0:28:13 > 0:28:16because I appear to have had my head cut off.
0:28:16 > 0:28:18Goodbye.
0:28:40 > 0:28:43Subtitles by Red Bee Media Ltd