The third and final Christmas Lecture with Professor Bruce Hood.

Have you ever seen a face in a piece of burnt toast? Why are our brains so obsessed with people-patterns? It's not just other humans either, your brain likes to give a personality to anything that shows a hint of character; whether it's your teddy bear, your pet fish or even your car.

Yet there are elements of being human that prove virtually impossible to recreate artificially. Can a robot ever fall in love? With sensors to measure our response to some revealing live demonstrations, Bruce looks at what makes the human brain so special and how it is built to read other people's minds. Why do you feel pain when somebody else gets hurt? What attracts you to another person? Are your eyes a window to your soul? Discover what makes us truly human.


Being Human


Christmas Lecture
Professor Bruce Hood
London, UK
Filmed in:
The Theatre


Collections with this video:
CHRISTMAS LECTURES 2011 - Meet Your Brain

Licence: © 2011 The Royal Institution




Billy, I've got a problem. I've got to pay the director and I've only got 5 pounds.

That's it?

Can you help me?

Yeah. You've just gotta do this. Fold it once like so, twice like that, three times. Just squeeze it, give it a magic blow, and your fiver should look more like a tenner.

That should cover -

If that works.

That'll cover his expenses. Thanks very much. Watch this lecture and I'll explain how Billy does her magic. Thank you.



Full house, good.

Welcome to the 2011 Royal Institution Christmas Lectures. I'm Bruce Hood, and I'm about to amaze you with mind-reading. Now, I don't need a brain scanner to do this. Instead, I'm going to use my own mind to read yours. Now, I've got some playing cards here, and I'm going to put them out on the table. Let's see, yes. OK. Now I want you to select one of the cards. But in fact, I'm going to read your mind. I'm going to influence your mind, OK? So choose a card and concentrate on it. And I'm trying to read your mind. And now I'm controlling your mind.

Focus on the card. Have you got it? Have you got it in your mind? Hold it there. Yes. Yes, let's see. I think it's going to be that one. OK, prepare to be amazed. Your card is no longer there.



Now, did I read your minds and control your thoughts?


Of course not, no. That would require psychic powers, which simply don't exist. Despite what you may have seen or heard, humans don't really have supernatural powers. And if they claim they do, then they're either fooling themselves or using a trick, just like I did. What I really did, of course, was I got you to focus your attention on one card so that you ignored all the other cards. And all I had to simply do was change all the cards so every card is different. Now, even though that mind-reading was a stunt, we can mind-read others, and actually we do this all the time, not with any supernatural spooky powers, but with just the way we understand others and try to predict what they're going to do next.

If you think about it, how often do you try and figure out what someone else is thinking? You try to work out what's on their mind by watching their behavior, looking at the expressions on their face, and imagining what you would do in their situation. In a sense, you're putting yourself in their shoes. In fact, you're the best mind-reader in the animal kingdom.

How do we become so good at mind-reading? Well, the answer is childhood. It's not a time of immaturity. It's the research and development phase of our lives. We're absorbing ideas from those around us and trying to work out what they're thinking, some new ways of seeing the world. And the more time a species spends in childhood, the more creative their minds are, the more social they are, and the more sophisticated their brains. Our childhoods are all about becoming human.


Now, other species have hardly any childhood at all. For example, these are baby chicks, only a few days old. Aren't they cute? Yeah? Hi, guys. You're on television.


I'd like to introduce you to another baby, not a chick this time, but a young human called Finn. Now, quietly, quietly. Here we go. Hello.

Thank you.

Hello. This is baby Finn. How old is he? Can I hold him?

Of course you can.

There we go.

He's 11 weeks old today.

Happy birthday, weekly birthday, Finn. Can you see him? So how far is he walking at the moment?

Not very far.

Oh. Is he reading?

No, not much.

Not reading. What school is he at?

No school.

He's not at school yet?


Well, what does he do?

Sleeps, eats, poos.

I was only joking, of course. He can't do very much on his own. If we left him by himself, he probably would be in a lot of trouble. Whereas these little chicks are much younger and they probably would survive a lot better. So Finn always needs his mother. Let me give you back for a moment.


It might look like Finn's not doing very much, but his brain is busy wiring up, taking in all this information, listening to me as we speak. He's taking in all this social interaction and he's storing it in his brain. By the time he reaches maturity, Finn will have a social brain. With his social brain, he'll learn from others and actually all about others. When he can do that, he can predict -


Sh, sh, sh.

- what they'll do next. Finn, are you thinking what I'm thinking? Are you?


Big smile. How do we know that babies are social? And when does it all begin? Well, let me take you all back just before when you were born. Let's imagine we're inside the womb. OK, let's bring lights down.


So you can't see very much inside the womb, can you? Just listen. What's that sound? Hands up. What do you think that is?

The heart.

It's the heart beat. That's right. And sometimes you can hear your mother's voice.

Well, we've decided not to find out if it's a boy or girl.

You see, the human voice has a melodic quality that infants pick up on. And even before they're born, babies can recognise their own mother's voice. In one study, the mothers read Cat in the Hat by Dr. Seuss. You can just hear it.

The sun did not shine. It was too wet to play. So we sat in the house all that cold, cold, wet day.

Now, when the babies were born, they preferred their mothers' version of the story in comparison to anyone else's. Now the only way the babies could have learned their mothers' voice was by listening to it whilst they were still in the womb. So your brain starts learning before you're even born. And after you're born, even though the senses are still very limited, babies will pay special attention to humans. For example, humans can recognise faces, prefer them in comparison to other patterns. Can I have some patterns here?

So these are patterns that are used in these studies. And here we have one which looks like a face. And here we have one which is all the same but it's a kind of random pattern. Let's see if Finn still prefer faces to random patterns, yeah? OK, so can you record over me? Hello. You get to hold that.




Shh, quiet, quiet, quiet. So let's see. How about this face? Oh, is that interesting?


Not as interesting as his hands.

Oops. Do you see how Finn, when he sees the pattern, he follows it with his eyes? Now, Finn's 11 weeks old. But when the scientists did this with newborns, newborns seem to come out ready looking for faces. So faces are like magnets for babies, capturing their attention so that they can hardly look away. Now, we're not going to give a loud round of applause. I think he seems to be settled. But we'll still just wave goodbye to Finn. Bye, Finn. You can go now. Bye. There you go. Thanks very much. See you in 15 years.


Faces are important to Finn, but what happens when you get older? Well, I'd like to introduce you to Esme. Come on through, Esme. Hi there.


So Esme we've chosen because she's wearing these eyeglasses, which are special. Now, what these glasses are is they have a mirror and they have a small camera. So the reflection of Esme's eyes are being fed into the computer, and the computer is processing this information. And you'll be able to see exactly where Esme is looking when she looks around the world. So if you have a look on the screen. Let's bring you over here, Esme. I have my assistant here, Thalia. So tell me what you can see.

I can see a brain, some drinks, some apples and some tea, some mugs, a cash register.

OK, let's try you with another pattern. So if you look at the - That one. There we go. So here's the same scene again. Who are you looking at?

I'm looking at the people who are talking on the phone and being very busy.

So in the same scene, when you have faces present, faces are just that much more interesting and important to humans. So the human face is something that we're very interested in. Let's see what it is about the human face that you enjoy. There we go. So she's actually tracing out a triangle, isn't it? Her eye movements are on the eyes and looking at the mouth, and then between the eyes. And in fact, the eye region's really the most important part of the human face. And if you measure brain activation, it's driven a lot by the eye region.

So let's have a look around at the audience, shall we? So why don't you look at this section over here. What can we see? So Esme's looking around and just picking out all the faces. There you are. Don't you look good. Give a little wave. Hello, Esme. There you go. Thank you very much, Esme. We can let you go. OK, off you go. Round of applause for Esme.


We've become so good at recognising faces that there are areas of our brain devoted just to this. And these are found in a small processing area just behind your ears. Now, in some unfortunate cases, when people get damage to these regions, they can lose the ability to tell faces apart, and even they can fail to recognise famous faces, friends, or even members of their own family. And anything that resembles the structure of a face, with two eyes and a mouth, can trigger these brain areas, which is why we tend to see faces all the time. Now take a look at some of these examples up here.

Does that look like a face?


Yeah? Anyone see it?


Yeah? How about this one?




That's an easy one. You see, there's a face there, isn't it?


I like that one.


Yeah, that's very good. That looks like a shark. And there we have -


Anyone in the Royal Institution, if you go to the toilets and look at the taps, you'll see there are faces on the taps. So we're just programmed to find faces anywhere. Here's another face up on the screen. Take a good look at it. Anyone recognise who it is?


Albert Einstein.

Shout it out.


Yes, it is Albert Einstein. But have another look at the face again. There's something a little bit peculiar about it. As it's moving, it looks like his eyes are following you. Tell you what, let's bring in Albert Einstein, because I want to show you this effect a little bit more closely. Round of applause for Albert Einstein.


OK, now this is called a hollow face illusion. And it was discovered by another Christmas lecturer, Richard Gregory. Now, the thing about faces, they usually point out the way. We don't often see faces as in the case, like a mask pointing in the way. Now, when you see the inside of the mask, your brain just assumes that it's a face pointing out the way. And that's why you get this strange effect, because the eyes appear to rotate in the opposite direction. You don't have a model for an inverted face in your brain, but you do have them for faces that point out the way.

And that's why you experience this very bizarre, peculiar illusion. So I think it's a big round of applause for Albert Einstein.


Now, the more faces we see, the stronger the mental model the face becomes. Faces are one of the most important ways we tell each other apart. Now here's a familiar-looking face. Does anyone know who that is?


Shout it out.


Professor Brian Cox. Are you sure? Or is it his evil twin?

[LAUGHTER] Now, what's wrong with his face? Anyone know? Yes.

His eyes are upside-down.

That's right, his eyes and his mouth are upside-down. But so long as the features of the eyes and the mouth are roughly in the correct location, we take it to be a normal face. Now, as you get older and more experienced with faces, you process them differently, using lots of shortcuts. So you tend not to notice the details so much. What's really interesting is that younger children would be faster to notice there's something wrong with Brian's face, because they look at the features rather than the face as a whole.

So why are we so interested in faces? Well, they communicate huge amounts of information, particularly about emotions. Now, these emotions are the states of the body that prepare you for action. They affect our behavior, our breathing, our pulse rate, even how we digest our food, all the really important things that we need to do to survive. Now, if I show fear and panic on my face, then I'm signaling to you, and you know there's a problem and that we should get out of here pronto.

Now, there are thought to be six basic types of emotions. Now look up here on the screen and see if you can tell me which emotions these are. All right, what do you think emotion A is? Anyone like to suggest? Shout it out.


Angry, hands up for angry. OK, that's right. What about B?


Do we have fear? Hands up for fear. I think that is fear. What about C?


That's the easy one. That's surprise. Now, what's going on in D?


That's well and clear. And what about E?


Sad. And F?


Disgust, great. Charles Darwin, the great evolutionary biologist first suggested that we use emotional expressions as a form of communication. So let's see how good you are with that. I think I'm going to get you over, Andy. Or maybe Joe. Why don't you come. Let's see if you can do some emotions for us. Come on. Would anyone like to pull an emotional face? OK, chap at the end here. Let's pull one. What's that supposed to be, anyone?


I think that's fear, isn't it? Anyone else? That's happy.


OK, what about up here? Joe, can you come all the way up here? Here, go for it.


Oh, that's definitely fear. Wow, a round of applause for fear. Well done.


We're so good at reading emotional expression, we can even tell when someone's faking a smile. Now have a look at these two pictures of the same person smiling. Which one do you think is a genuine smile and which one is the fake one? Is A the genuine smile? Put up hands if you think she's being really genuine. Oh, a couple for A. And what about B? Yes, clear winner. B is the correct smile.

Now, what is about the faces which makes a difference? Well, let's just narrow it down and see. It's all to do with the eyes. She's 'smizing' - smiling with her eyes. In fact, she's using a totally different set of muscles, muscles which control the eye region. And when you see the wrinkles around the eyes, then you know the smile is genuine. Some emotions are programmed into the brain by evolution while others are shaped over childhood by those around us.

For example, babies do express several emotions early on, and even blind babies smile, even though they've never seen a smile to copy or imitate. But emotions can also be shaped by experience. Take disgust. This is one emotion that's not present in the newborn. After all, babies can be quite disgusting when you think about it. However, somewhere around the age of two, children start to learn what is disgusting by watching others.

Ah, I could do with a drink, actually. I'm feeling a bit parched. That's good juice. Anybody want to try some apple juice? How about you. Now, what's your name?


Come here, Emily. Would you like to try some of my apple juice?


I think we should use a new glass, though, don't you?


Oh, that's good. I've got a new container. This is what I use when I run out of glasses. Have a look in there.


Would you like to have some apple juice?

No thanks.


You're sure?


It seems all right to me. No? Oh, maybe you need a straw.


Because a glass doesn't fit. I know what you like. Would you like to have a straw?

No, thank you.

You sure?


Why? It's all right. Look.


It's delicious. No?

No, thank you.

A big round of applause for Emily. Thank you very much.



It was a perfectly brand-new toilet, perfectly clean and perfectly safe to drink out of. What's that? That's the wrong toilet?


No, I'm joking, of course. It's because we've come to learn that toilets are used for waste. We can't easily overcome our disgust triggered by the thought of drinking out of a contaminated toilet. Even when we know that it's brand-new, you can't help yourself feeling a bit revolted. After that drink, I'm feeling a little bit peckish, I think.

Snacks, get your snacks here. Snacks.

Ah! Something to eat. Joe, come in here. What have we got here? That's right, bugs. Mmm, I'm feeling quite good about this now. Anyone for a bug? Would you like to have a little nibble of a bug? No? No? Really? They're really quite delicious. No? What about this one? This one's got nice legs.


No? No? Can't tempt you? They're really OK, honestly.


Mmm, absolutely delicious. Actually, I think I need something to wash that down. No, no, no, not the toilet.


Mmm, these are grasshoppers. Now, grasshoppers are considered a delicacy in some countries, and they're very nutritious and highly prized. It tastes a little bit like roasted peanuts. However, Westerners generally won't eat insects. Our culture has an influence on what we find disgusting. One reason that disgust may have evolved is a useful way of signaling to others what is safe to eat. And this is because humans are omnivores, which means that we can eat many different things. In other words, children are using adults as their food tasters by watching their expressions.

Now, emotions are not just all in the mind, but they can physically affect our bodies, too. Just look at your reactions to someone doing something disgusting, like when I drank out of the toilet. Have a look up here.


It affected your behavior. Now let's try a different emotion now. Try this out. Take the straws I gave you. OK. Now first of all, I want you to put the straw in your mouth like this, so you're pouting, OK? All right, everyone got it. Put your straw in your mouth, sir. Everyone put their straws in their mouth. Actually, in the gallery, all put your straws like this. Now, I'm going to play this. Listen carefully.


OK, not much. Now take the straw out and put it like this. Ready.



Funnier, isn't it? Why is it funnier when you've got the straw like that? And why did you laugh? When you have the straw in your mouth like that, you're forcing your mouth into a certain posture. You're forcing a smile. And your brain associates physical actions. It was difficult to laugh when you had your mouth pouting. But when you had it like this, this is the same structure that you have when you're smiling. And of course, the other thing was, I played us a laughter track. And laughter is just one of those contagious emotions that just travel. When you hear someone laugh, you feel the urge to laugh yourself.

Now, emotions not only communicate information about things in the environment to pay attention to, but they bind us together socially. So let's see if we can actually measure the physical symptoms of this by measuring our blood flow. Now, I'm going to require - I'm going to actually have to give my own blood sample here, but luckily I've got a specialist. Charlotte, you're going to come in and you're going to measure - You're going to take a blood sample, are you?


OK. So what should I do?

If you'll just take your jacket off, please, and sit down for me.


If you could just take a seat.

I'm not very good with needles.

It'll be absolutely fine. I'm just going to put a tourniquet on first so that we can find your veins.

What's that smell?

It's just so it's hygienic.


I'm just going to swab you down there.

I have to say, actually, I'm not very good with needles.


Just going to prepare the needle now.


Right, you ready? It's just going to be a sharp scratch. Ready?

Nope, stop. Stop, stop, stop, stop, stop, stop. I can't go through with it. Thank you, Charlotte. Round of applause.


Of course the real purpose of that demonstration was not to take a blood sample. The real purpose was to show that we can literally experience someone else's suffering by watching them and putting ourselves in their shoes. A lot of you didn't look very happy when you saw that needle. And we have one person in the audience who's been wearing a heart monitor throughout this entire lecture. Now, we can put up their heart rate up on the screen above here. Now, you can see that, up to that point where I mentioned injection, his heart rate has been fine. But as soon as it starts mention - where you hear the word injection, it's been rising.

So the person who watched that, his anxiety was increasing, even though there was absolutely no risk to them. So why did the heart rate go? Well, it's because when you're watching someone else enduring a painful experience, you empathise with them both mentally and physically. So who was wearing the heart monitor, or is wearing it? Hello, Alex.


Now, you don't particularly like needles.

No. That was quite clear there. And you can see there, if we can now put up this thing here - Oh, actually, your heart rate's going sky high again. Is that because we're all kind of looking at you? Is it really? I mean, as I'm talking to you, your heart rate's climbing up to 120, and it's climbing -


I'm worried about you. I'm worried about you. Well, of course. The thing is, because we're social animals, as soon as we become the attention of everyone around you, and frankly, everyone in the Royal Institution here, we get very self-conscious. And that's very anxiety-inducing. So thank you for being such a good sport, Alex. Big round of applause.


Now, scientists are fascinated by our ability to copy emotions and behaviors. But how does the brain do this? Well, one current theory is that there's a mechanism called the mirror-neuron system that responds to watching other people's movements as if we're moving ourselves. Now, humans have an amazing capacity to copy and learn by observing. It's even present from birth. At first, this imitation and copying is restricted to emotional expressions such as smiling, something that most of us do in a social situation. Because if you smile at a baby, there's even a very strong likelihood that they will smile back to you.

Now, we got this a bit earlier when Finn was in earlier. We filmed this. I'm just going to show you. Here's me interacting with Finn again.


Whenever we watch other people, we're doing things which our neurons in our brains are resonating with their activity. So in effect, our brains are becoming synchronised. One way to express this is through movement. So I want you to look at this pattern on the screen now. It's just a series of dots. But can you see anything amongst those dots? Can you see the invisible person? Well, watch this. Can we have them move? Isn't that remarkable?

With just only a few dots, you can read and see someone there immediately. So for example, what sex do you think this person might be?


Hands up for male. Well, that's pretty clear. Very good. All right, so this is a man. And let's see if he's going to be a happy man. Can we have a happy man, please?


He's in a good mood, isn't he? So what's going to happen now, I wonder. Shall we get someone else to come along maybe? They're shaking hands.


It's a lady. Who thinks it's a lady? That's right, it is a lady. Shall we have a bit of fun? Shall we get them to do different actions? What shall we try? Shall we get them to clap? How about that? Let's see what clapping looks like.

There we go, clapping. How about can you pat your head and rub your tummy? OK. Actually, let's see a little bit of dance moves. Can you do the John Travolta? You see, with just a few dots, you can read incredible things. The brain can extract surprisingly complex social information from just the movement alone. From just a few dots, our brains are working out the gender and even the state of mind of someone.

I think we should get these guys in just to prove that they're not dots but they're real humans. Can we bring in the team from London South Bank University? Come on in, guys. Big round of applause, please.


So here we go here. So this is -






And Darren. Now let's have a look at what they're wearing. They're wearing these light spots. And this is what you saw on the screen, because these are reflective, and the images in the cameras were being captured. And this movement was what was producing all this rich information. So Darren, tell us a little bit why you use this and what's going on in this.

Yeah, it may surprise some in the audience, but this is the kind of technology that major computer game developers use for their animation. So I'm sure you all know the football games that are available. This is the exact technology that they use in it.

Great. And you're using it for research and development as well?

Yeah, yeah. We've got three themes of research. So we have a sports, we've got clinical, and we've got commercial side. So I mean, if we take our sports angle, we've got two focus sports - taekwondo and basketball. And by analyzing our athletes' movements, we're able to pick the important parts out so we can improve their performance.


Pretty good technology.

Well, thank you, Lex. Thank you, Will. Keep those movements going, and good luck with the research, everyone. Big round of applause for London South Bank.


What might surprise you is that babies as young as four months old can also see moving spots of light as people. Now, not only did they see movement as people, but they also start using movement to work out what someone is actually like. So have a look at the clip of this video here. This is an animation. Let's see if you can think about it another way. There we go. So given the choice, which do you think is the more friendly object?


Hands up for green. Hands up for yellow square. It's amazing, really. It's just an animation, yet we think of these things as having personalities. In fact, babies, when they watched this, were given the choice between a square and a triangle, and when they saw the square being helpful, they preferred to play with a squared object. So these babies are interpreting them and giving them rich personalities. From the very beginning, we see the world as populated with others who are acting with goals and intentions. We even apply that reasoning to inanimate objects. I mean, do you ever speak to your toys? Or if you have a computer, do you get frustrated and shout at it when it crashes? Do you say, don't crash, I haven't saved my homework?

This is exactly what we do. We give inanimate objects these qualities to make it easier to interact with them. It's another way that our brain is making assumptions about the world and adding extra information. Movement provides not only a rich source of what someone is like, but a channel of communication where no words are exchanged. Synchrony is essential to many human activities, such as dancing to music. Now, whilst some pets can be trained to dance, others can do this spontaneously. Take a look at this cockatoo called Snowball.


So cockatoos are highly social birds that bond for life, which is maybe one reason that they copy another person's movements. And obviously, Snowball is copying his owner. Now, sociable birds spend longer as fledglings, so they have long childhoods in the bird kingdom. And they're more intelligent, generally, and actually have bigger brains. So I want to try out some copying with you, but for that I'm going to need a volunteer to be a pirate. Hmm, let's see, who's going to be a pirate? I think we could have - Let's have the lady there. Would you might be coming down? Yep.


OK, and what's your name?


Olivia. OK, Olivia, I'm Captain Bruce Hook. OK, so we're on this ship, and I'm the worst captain on the seven seas. And I reckon you're going to mutiny, so I've got to teach you some discipline. I'm going to make you walk the plank. And this is my cockatoo. So get on the plank and see if you can walk in a straight line. When you're up there, just balance with your two legs. OK, hold it there. No, get yourself stable, girl. There you go. You can put your hands out if you wish. There you go. You stable? Good.

Now look what happens. Avoid the sharks. Oh, it's really hard to keep the balance. Oh, you're doing very well. Can we make her tip over? Yes, I think so, into the ocean, to the Davy Jone's locker. Are you finding it harder? Thank you. Was that much harder?


Actually, that was pretty good balance. Well done. When we watch other people, we copy their behavior and movements. And it's really difficult to maintain balance, especially when you're watching someone else wobble. So as a social animal, we prefer to be in synchrony with others. This synchronization is useful for picking up information from others. One very powerful form of synchrony is called joint attention. Now, whenever humans interact, they have to coordinate their focus of attention.

Imagine a conversation without looking at someone in the eyes. Not only is it difficult to do, but the experience would be very odd. Now, I didn't tell you to look up, did I? But you just instinctively followed my direction of gaze. And that's called joint attention. This is because joint attention, you interpreted my behavior to indicate there was something of interest worth looking at. Now, joint attention first appears in babies before they have language. And pointing to objects of interest is also a uniquely human ability. Chimps and monkeys will point to food if they want food, but they don't point to things just to share the sheer joy of interest.

Now, this human bias to share our attention with others can be manipulated and controlled by magicians who don't want us to see everything all the time. Would anyone like to see some magic? Let's shout out. Do you want to hear some magic?


OK. Ladies and gentlemen, I would like you to give a warm welcome to the amazing Billy Kidd.


Billy, you're always full of surprises, aren't you?

I know.

OK, Billy, what are you going to show us?

Well, today I am going to show you guys one of the oldest magic tricks in the world, simply known as the cups and the balls. And we use three cups in this trick and three balls as well, ball number one, ball number two, and if I can find it, ball number three. So Bruce, your job is to watch very close.

All right, I'm going to watch closely.

Really close.

Because what we do is we take ball number one and we vanish it, like this. Now wait, Bruce, I'll do it again, because you're all paying really close attention now. Ball number two. See if you can catch me, yes. We do it like this. And - You caught that, didn't you?

Yeah, I saw that.

All right. I'll do the real magic. Ball number two goes like this.


It's easy. You just need a magic wand. Ball number three, this one goes my favorite way, actually. Watching close?


And that ball is gone.


Some of you are shocked, I can tell. I'll tell you what.


Just like that, the balls come back. Now Bruce, I can tell this is somewhat melting your brain a little bit.

It is, indeed.

Being a scientist and all. So I'm going to make it a little bit simpler for you. I'm going to take ball number one and eliminate it, which would leave how many balls?

There's two there.

That's very good. He's a scientist.


Bruce, if I take the second ball and I eliminate it from the game, how many balls would we have under the middle cup? Very simple.

There's one, definitely.



But tell me this, why does that one come back?

I'm not so sure.


Ah, OK.

This one goes away. And if I tap this one, that one - OK, I'll put this one away as well. This one comes - You know what, let's make it simple. How many in the middle cup, do you remember?

I think there's one. Oh, no, there's two. OK.

I'll let you try again. How many in the middle cup? Do you remember?

There's definitely two.

No, see, it's three, Bruce.



Listen to the kids. Even simpler, for Mr. Science Man. Three balls going in as a group. Very simple now. How many here now?

There's nothing in there.

No, you see that's a big one.


But I'll make it even more difficult for you, because I know you like a challenge.


Watch close.

I am.

Watch the hat. Nothing in the hat. Watch this ball, because in a moment I'm going to make this ball vanish from the hat. With the power of the magic stick, what we do is this.



And like that, the ball's vanished.


You don't believe me, do you, Bruce?

No, it's still there.

All right, skeptic. I'll bring it back.




That's not fair.


Come on.

All right, we'll do it for real. Ready?


How many under the hat?


Very, very good. How many now? Sh, sh, sh, sh.

Ah, I can see three.

Sh, sh. How many? Just Bruce.

There's three there. I saw three. All right, you caught me that time. They were rolling around. What I can do. But I'll tell you what, the thing is you shouldn't really be watching the balls. You should be watching the cups.


Wow, that's -

And wait for it. Wait for it. A brain.

Ah, round of applause.


I had no idea. Billy, I have no idea. I think I'm going to need a volunteer to watch you a little bit closer. Can we have a volunteer? Let's choose someone from - Let's choose Sir. Why don't you come down.


Come this way. All right, now what's your name?


OK, Eric. Stand around, because Billy's going to show you a routine.

Hello, Eric.


You all right?


Stand right here. I'm going to show you something. But I need to know, do you know what this is?

A red, spongy thing.

A red, spongy thing, that's very observant. This is - We'll call it a sponge ball for now. It's not just any sponge ball. It's two. OK. Now, if you hold your hands out like this, straight in front of you, I'm going to put one in your hand here and one in your hand here, just so you can feel them. Regular balls, yes?


I'm going to take one and put it in my hand there. You're going to hang on to this one and squeeze nice and tight. Nice and tight, OK? Now put your other hand on top as well, nice and tight. And watch close, because when I squeeze mine, it vanishes. And when you squeeze yours - open them up really slowly - you have two again.



Round of applause. So what magicians like Billy are doing is they're using the power of the gaze to misdirect attention. That's about right, isn't it?


And this is why you don't notice them performing manoeuvres. Now that you know how it's done, watch her one more time, because Billy's going to explain as she does it.

So what I actually did is, when I take this ball, I put it in my hand and I look over here. My body, my eyes are all looking at this hand, which makes you guys look at this hand. But you know in reality I have it over here. So I took this ball and I made you close your hands nice and tight together.

Oh, I felt that.

You felt that? Oh, he felt it this time. You see? Mine vanished. Remember, like before? So how many did you have in your hand?

Two. Three.


Round of applause. Well done. Thank you very much.


OK, Billy, I suppose you're going to disappear again, aren't you?

Well, of course.

OK, let's see it.

Ready? See ya.


Billy Kidd.


So Billy showed us how she could manipulate others by using misdirection. And the eyes are very powerful. Direct gaze is such a powerful social cue that it explains why strangers don't necessarily look at each other when they're standing close, because it could be seen as a threat. And you can try that out the next time you're in a elevator, in a public area. If you see someone close to you, just look at them in the eyes, and they might be a little bit surprised. Now of course, it's all right to do this in some cultures. In the Mediterranean, staring at each other is actually quite acceptable.

Now, when someone starts staring at you, this triggers brain activation as you're processing the faces. So let's see if this next example works. I want you to see two pictures of me. OK, have a look at these. Now, hands up if you prefer picture A. And hands up if you prefer picture B. Wow, that seems to work. That's pretty good. I think picture B is the winner. Now, who preferred picture B? Put your hand up.

Young lady, why did you prefer picture B, do you think? Do you know? Not sure? Anyone else? Who else? Did you prefer picture B?

Yes, because you're smiling, kind of.

You think I'm smiling? Anyone over here? Why did you prefer picture B?

Your eyes are less kind of -

They're less kind of - That's right. Actually look at the pupils and you'll see that, in fact, the eyes are very dilated. The pupils are much larger in picture B then they are in picture A. And when you show people pictures which are identical except for the eyes, the tendency is always to prefer the one where the pupils are larger, because when someone looks at this, this creates activity in our arousal, and our eyes dilate, which is why we usually prefer images with larger pupils. And this signals that they're interested in us. And of course, we tend to like people who like us.

All of these cues are just about some of the ways that humans read each other's behavior. Now, when you interact with another person, one of the most important things to work out is what are they thinking. But before you can know what someone's thinking, you have to have a sense of your own self. Now, how do we develop this? Well, meet Simon the Siamese fighting fish. Now, Siamese fighting fish are very territorial. The males will attack any other male which encroaches on their territory. So let's see if Simon has a sense of self. He seems quite placid at the moment. But let's put a mirror against his tank.

I'm going to put this behind him and see if he turns around and notices there's another fish. So when he turns around, let's see if he spots himself. And what you should see is that he'll swim directly towards it, and the gills will flare out as a territorial display. So let's see if he spotted himself. There he goes. Ah! See how fast that was.

Now look, he's fluttering his gills and he's trying to attack the other fish. And he'll keep bouncing on the glass, swimming backwards and forwards, until this predator, this interloper, disappears. You see how remarkable that is?


There, he's not giving up. He's quite a toughie, is our Simon. There we go. So because he doesn't have a sense of self, he doesn't recognise that it's his own reflection. And this is actually a technique that scientists use to determine whether children and animals understand they have a sense of self, because if a baby looks in the mirror and they're very young, they just treat the reflected baby as another baby. But when they get to about 18 months, if you put, for example, a little dab of red mark on the front of the forehead and they look in the mirror, then they realise that their reflection must be their own self.

And this technique we use to study the sense of self in other animals. For example, here's a little video of an elephant called Happy. And she's in the Bronx Zoo in New York. Now, we haven't put rouge on her forehead, but we put a little mark. And she's spotted herself in the reflection and is trying to remove the tapes on the side. So she knows that that image is her and that mark must be on her head. Now, elephants and dolphins and other social animals have this idea of self-recognition.

But back to us humans again. As you grow up, you develop a sense of who you are. And by the end of infancy, you're starting to consider others. You're becoming more social. You're helping others. You're feeling their feelings. Now, very young children think that everyone around them shares the same thoughts as them. But somewhere between three and four years, they begin to understand that others can have different points of view. Now, we're going to try something to see if you can predict what someone else is thinking. I'm going to need two volunteers for this.

So I'm going to choose one from - Let's see, somewhere in the back. Oh, green-handed man there. Come on down. Sorry, green top there. And I'll choose someone from a section. Can you get down there, lady, with the - Yes, that's you. Stand up, please. Come on down. There we go. Can you go that way? Round of applause for both of our volunteers.


Hi. So what's your name?


This is Mark. And hello, what's your name?

Olivia. This is Olivia. Is that right? Well, I'm going to need one of you to go outside for the moment. So I think I will send - Olivia, would you go outside for the moment? I'm going to take you outside. And Mark, you're going to help me with my next demonstration, OK? So let me just move this cabinet forward. This is a cabinet I use where I keep my brain. So do you want to just check that they're empty?


Yep. You're happy with that?


OK, so this is my brain that we're going to use. So would you put the brain away in the brown box for me? You can do it for me. Just put it in there and then put the lid on it. OK, good. Just wait for a moment. I was just telling the audience about how we use our social brain that helps us to predict what people will do based on what they think is true. Actually, can I have the brain, Mark? You see, when we're thinking about the brain, it's really just - Mark, can I -


How did that happen?

I don't know. There's probably a secret trap door in the bottom of the box.

Do you reckon? It must be something like that. But why did you search here?

Because I put it in there originally.

All right, come around here. I'm going to show you something, Mark. Come here. Now, the reason you couldn't see or didn't know that the box was over there was because, what you didn't know - well, you kind of guessed it somewhat - but what the audience didn't know, is -


It's Billy Kidd again. Thank you very much. Come here. So you looked in the brown box because that's where you put it. So you believed it was in the brown box, didn't you?


But you didn't know how it got there to the blue box?


So your belief was false, wasn't it? Now let's see if you can work out what someone else is going to do if we do the same thing. So it was Olivia. Wasn't our guest Olivia?


What do you think Olivia would do? If I put the brain in the brown box, where will she look?

She'll look in the brown box.

That's right, because she believes it's in the brown box. But we know that Billy always moves it, doesn't she?


So where will it really be?

In the blue box.

That's right. So you realise you've just done something very clever, haven't you?


You've actually been able to work up what Olivia will do. You've been able to put yourself in her shoes. That's really quite a unique ability. We're going to have a bit of fun with that. So we'll get her back in, see if we can pull the same trick. OK, no one give away the secret. So you stand back and watch what's going to happen. So quiet, everyone. I'm going to go and get Olivia now. Hello, Olivia. It's Olivia, is it?


Come on, Olivia. So just come here. I was just explaining to Mark about this experiment that we do. And this is where I keep my brains. You can have a look in there. It's empty. You can have a look in there. That's one empty as well. This is where we store the brains. And this is my brain. So, Olivia, would you put the brain in that box, because I am just going to talk to the audience a little bit about the social brain. Now, you see, the thing about the social brain is that it's one of the most remarkable things, because we can predict what people will do based on their beliefs. Olivia, can I have my brain, please?

It's not in there.

Well, where might it be, do you think? There are two -

In this box.

Do you want to look for it?




Well done. Come on, I'll show you. It's Billy again.


OK, big round of applause. Both of you back to your seats. Thank you.


Now, that was a bit of fun, but this is a re-creation of a famous experiment for a core component of human nature called theory of mind. See, once you knew that Billy was hiding underneath, you also knew that Olivia was in for a surprise and that's why it was funny. You understood that she could not know what was coming up. And she had a false belief. Now when you think about it, comedy, drama, and many aspects of human storytelling requires us understanding a theory of mind. People who have difficulty understanding other people's points of view, such as very young children or children with autism, would typically fail this type of test. They cannot see things from someone else's perspective. They do not understand that others can have false beliefs.

Now, when we develop a theory of mind, we start to care about what others think about us. As children develop their sense of their self, identity independently of their family, they increasingly seek out the approval of all their friends. However, one problem is that they feel they're constantly being judged, which shows up as activation in parts of the brain that monitor social interactions. So it's tough being a teenager. We all know how horrible it feels to be left out. And of course, brain imaging studies have shown that, when this happens, this sort of rejection lights up those parts of the brain which respond to physical pain.

So this social rejection pain is real. Now, maybe this need to belong explains why social networking has become so popular. Hands up if you're on Facebook or Twitter. In fact, that seems just about almost everybody. That's really good. Can I ask you, you're on Facebook, why do you like being on Facebook?

Keep in touch with friends from primary school.

Keep in touch with friends. Anybody else? Hands up. Why do you like being on Facebook? Yes, sir, what do you like?

It's just easy to contact people.

It's easy to contact people. Any others? Yes.

You can show people what you're doing.

You can show people what you're doing. Anybody else? The one at the back there.

It's just nice to talk to people that you haven't talked to for a while.

So you can increase communication. And all the physical boundaries which make difficult social interactions are just that much easier when it's done electronically, isn't it? In fact, do any of you have friends in different countries on Facebook? See how easy it is when you can start talking to people across the globe. So I think this is a really interesting part of our development as a society. We now have the technologies to speak to anyone around the world at any time. And so the boundaries of physical space are no longer a problem.

Now, I sent out a tweet on Twitter. And I'm not sure if anyone's on Twitter. But a lot of people ask, what's the point of Twitter? It just seems like a thing for gossiping. But let's look at some of the responses that we got. So here we go. We've got Nicholas who said that, depending on how often you tweet, Twitter can help us feel closer to each other. I like this one. This is Tim. He says, I would not have met my lovely, fantastic, smart girlfriend if it were not for Twitter. And the one at the bottom I particularly like, because this is clearly somebody who's quite clever, and he's thought about the way that we can communicate. He thinks Twitter is a little bit like a virtual brain. Users are like neurons and the followers are like dendrites. These are the connections. And whole networks greater than the sum of the parts.

So this technology and the future is unknown, but it is exciting. And you guys are right at the prime, about to find out. Now, throughout this series of lectures, we've been considering the workings of the human brain very much from an engineering perspective, a biological computer if you like. This has been one of the dreams of science, to build an artificial brain that can perform the same skills and think like a human brain. Now, when we started building machines to copy what human brains can do, the skills that we thought that would be really difficult, such as playing chess, turned out to be easy for computers. In fact, our best grandmaster chess players can be actually beaten by machines today. But the things that are trivially easy and effortless for humans, such as picking up a chess piece, turn out to be actually really difficult for computers.

Now, robotics is developing at a rapid pace, but could we really ever build a robot that thinks and feels like a human? Could a robot ever feel empathy? Now, things like computers, they can do things like voice recognition, but getting a computer to understand a joke or a story is still a long way off.

Is that so?

Well, yes, robots can seem very human and lifelike, but that's because we program you to behave like that. But you can't really understand what I'm saying.

If I cannot understand what you say, then how can I answer you back?

Well, because you've been programmed to. I mean, look over there.

Dr. Dahl is operating me from his laptop. Hello, Dr. Dahl. But I can recognise your face. So if you move yours, I will move mine.

Really? OK, let's try that out. Ah! Not unlike baby Finn.

And I can also be programmed to recognise special voice commands. I also have movement and touch sensors so I can learn. How do humans learn to talk?

Well, we're also programmed to learn language from others when we're very young.

If I am programmed and you are programmed, what is the difference? Are not humans complex machines as well?

Well, I guess we are in a way. But at the moment, computers cannot understand human language, because, well, it's really just too complex.

We could learn, couldn't we?

Well, I guess so. But for the moment, you can only do what we tell you. So let's just leave it at that, shall we? I mean, who's presenting this lecture anyway. I want to finish by telling the audience how clever the human brain is, so just turn yourself off and go off to sleep mode, would you?

Just you wait.

All right. Applause for Nao.


You know, Nao's right. There are already robots that are learning from their own experience and reprogramming themselves. Achieving the flexibility and creativity of the human brain, however, is a long way off. But in principle, it's not impossible. In the first lecture, we looked at what the human brain is. In the second lecture, we thought of the things it can do. And in tonight's lecture, we've discovered how it's evolved special skills to learn from and pay attention to others. But why is it so important?

Take a look at that clock. That's the estimated population of the world. There are currently nearly seven billion human brains living on this planet. In the past hour or so, the world's population has already risen by almost another 10,000 brains. Are you thinking what I'm thinking? Somehow we're all going to have to get along if we're going to survive as a species. It's a challenge. But luckily, we have brains especially evolved for interacting with others. And really, this is one of the main joys of life. So good night, and look after your brain.



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