Episode 4 Bang Goes the Theory

Good evening and welcome to the show.

Have you just arrived home?

Have you fought your way through queues and off crowded trains

and did you do the British thing of queuing very politely,

but actually inwardly seething?

With this country's population growing to 70 million people,

-we're going to have to learn how to cope in crowded places, aren't we?

-We are.

So, in tonight's show,

Jem experiences the crush of a crowded gig

and finds out where's the worst place to stand...

It's a bit of a squeeze to say the least!

Number-crunching Legend Johnny Ball hits the streets of London and counts cabs

to show how maths can help you guess the size of a crowd.

Whether we'll get this right, I can't be sure.

And later, I'll be seeing if a random group of people

can cooperate with each other without even knowing it.

Not only have they figured it out, they're actually playing a game.

So if you haven't guessed it yet...

Tonight's show is all about the science of crowds,

-the hows...

-The whats...

-..the whens

-..and the whys.

Where better to start than outside a football stadium on match day?

-Who do we love?

-ALL: Arsenal.

THEY LAUGH

We're all used to, aren't we, phrases like group mentality

or following the crowd?

But is there any actual basis to that

and can being part of a large group

actually make you do things that you wouldn't normally do?

I've never seen Arsenal play live,

but I can already feel the camaraderie here rubbing off on me.

It's almost kind of like you belong to something.

You're reclaiming it for yourselves,

all the things you wouldn't normally do, like walk in the middle of the road,

it's suddenly OK. People talking to each other and everyone bonding.

It feels nice.

Being in this crowd doesn't make me want to go on the rampage

and from what I've seen, no one else here is about to riot either.

But is there some kind of Jekyll and Hyde switch

that can bring out our worst or our best when we're in a big group?

I've joined world expert on crowd psychology,

Steve Reicher to find out. And he's a Spurs fan.

Yes, people do behave differently in groups.

They are transformed in groups.

That sense of empowerment,

you making history and controlling the world on your own terms,

that's exhilarating, that's exciting,

that's one of the things people get out of crowd behaviour.

Behind that empowerment is a shared sense of identity.

This crowd are united just by the colours of red and white,

wherever they come from.

These Arsenal fans down here are going to be thrilled

if somebody, often from another country, kicks a ball into the goal.

Not because they've done anything,

not because they've achieved anything,

because the group has done well.

And in groups and in crowds

it's the fate of the group that you care about.

If they do well, you've done well. If they are valued, you are valued.

That doesn't mean that they just do anything and get carried away.

But there are instances perhaps within a group,

there was a chap, I remember in the student loan protest

who threw a fire extinguisher...

Potentially he's not going to do that when he's not in a group?

People just don't behave in that way generally.

The interesting thing in that incident

was there had been confrontation with the police.

There had been a certain level of conflict, but at that moment,

when somebody did something which threatened life and limb,

which so clearly violated people's sense of what was acceptable,

actually, that de-escalated the conflict.

OK, so being in a crowd can change your behaviour,

but it doesn't automatically make us all rioters.

In fact, you're usually reined in by the crowd if you get out of control.

Quite how being part of crowd could have such a profound effect on us

has always been a mystery.

But here at the University of Nijmegen,

Dr Vasily Klucharev thinks he may have found an answer.

And in order to show me, he needs me inside his functional MRI scanner.

While I'm in here, he wants me to perform a test.

On a screen above me, 100 faces are displayed, one after the other.

I have to score them for beauty out of eight.

Here's the weird part - after each score I give,

the screen shows me how other people rated that face.

20 minutes later, Vasily shows me the inside of my head

and explains his testing had nothing to do with beauty

and everything to do with those red bits in my brain.

So in fact, this experiment

was about social conformity.

We are interested in how much

actually you change your opinion in line with others.

I thought there was something fishy going on,

because I was trying to figure out,

why were you showing me what other people were thinking?

Basically, we hypothesise

that whenever your opinion deviates from the group opinion,

your brain will emit certain error signals,

that you did something wrong when you judged faces differently.

-So, you've done something wrong?

-Exactly.

Is this an unconscious thing we do because we want to follow the crowd?

It's very automatic response.

During the scanning, we saw when you experienced a conflict with others,

your brain emitted this kind of signal.

If I chose one thing and the group chose something different

I actually felt, blimey, did I miss something here?

Have I done something wrong?

It's that hard-wired alarm signal in the brain

that Vasily has been looking at over the last few years.

And by looking at the size of that response,

he can now categorise people as conformists, or rebels.

I just wanted to show you, that here in the medial pre-frontal cortex,

this area is very important for learning

and it drives behavioural adjustments.

In conformists, we see that area lights up.

In nonconformist, this area doesn't respond.

So all these terms, peer pressure, following the crowd,

these are things we're all familiar with,

they're actually backed up really, by real, solid data?

Exactly, so we've perhaps for the first time,

suggested real neurobiological mechanisms for this.

So looking at the picture of my brain,

am I a conformist, or am I a rebel?

-Am I a free thinker?

-Let's have a look.

You have a smaller, but still some activity here,

so I would say that your brain activity is somewhere in between.

What does he mean "somewhere in between"?

My rebel legend dreams shattered.

Vasily reckons he can prove his diagnosis

in the final stage of the test.

He reckons I can never override

my annoyingly slightly conformist tendencies,

so when faced with those same 100 pictures,

I'll subconsciously adjust my scores closer to the groups' scores.

Although now I can't remember any of the scores from before,

I'm determined not to be influenced and 10 minutes later...

OK, I'm good.

..I'm ready for the results.

-This is an index of extreme conformist.

-Yes.

The person changed a lot in the second session

and this is your change.

You can see you changed a bit your opinion,

on average, slightly in line with the group.

It's a defeat.

Despite my best efforts to score the faces exactly as before,

I have been swayed by the group opinion, just as Vasily predicted.

Tell me, why does this happen?

Why is there perhaps a tendency for human beings to want to conform?

Is there a selective reason?

Because I'm a biologist, I'm very much biased by biology

and I think there is an evolutionary reason for this.

Simply the group is smart.

The average group opinion is better than individual opinion.

So, hang on, I think I'm a nonconformist.

What we'll do is hook you up to Vasily's MRI scan and have a closer look.

Looking forward to that.

As we all know, last year was a census year.

70 million people now living in the UK, which got us to thinking,

how do you figure out the size of the population

if you don't actually have a census form?

Had you count the number of fish in the sea, for example?

Very simple. You use maths.

Not my forte, I'll be honest, but made bearable when I was a kid

by this week's special guest, none other than Johnny Ball himself.

We asked him to think of a number.

He'd never heard that joke before.

Hello. As it happens,

I know a very good mathematical way of estimating an unknown population.

Using, ping-pong balls.

What a lot of ping-pong balls. But how many?

Well, I don't know so I'm going to try to estimate the number.

I could count them one by one, but that would take ages,

so this is a little more tricky.

What I do is take a good sample,

quite a few balls and I mark them with a felt tip pen. Here we go.

One, two...

This technique is called capture, recapture.

Biologists use it to find out animal populations.

..98, 99, 100.

Now what do I do? I pour all these back in again.

With real animals you might clip or tag them

and then set them free and hope that they mix back randomly.

I think that might be pretty random

but I'm going to choose another 100, but this time,

we're going to use a blindfold.

Four, five, six...

'I've put the blindfold on so I can't see whether I'm choosing the ones

'that are marked or not.' 100.

The question is how many of those hundred are marked? So here we go.

'Knowing how many are marked by my original mark....'

One mark. Two mark.

'..will help me to work out how many there are overall.'

17.

Nope. No.

No.

This is the theory.

If you divide the 17 balls into the second sample of 100 balls,

the proportion should be the same as dividing the first

sample of 100 balls into the total number of balls.

'So, second sample divided by 17...'

Equals 5.88.

'Now the first sample multiplied up - and that gives...'

588 balls.

That's our estimate.

It is time to reveal the actual number of balls.

There are...

600.

Not bad at all.

'It's all very well finding out how many ping-pong balls are in a tank...'

Taxi! 'But things get much more difficult in the real world.'

So here is another capture recapture experiment.

How many black cabs are there in London?

By using the same maths as I did with the ping-pong balls, I'll try to estimate that number.

'I genuinely have no idea how many they are out there,

'there must be thousands. So I will need some help.'

-Off you go!

-OK.

'The bigger the sample, the more accurate our estimate will be.

'So we spent two hours counting cabs in five places across London.'

This counting taxis is not as easy as it looks.

Whether we will get this right, I can't be sure.

'We are noting the unique licence numbers as our way of tagging the taxis.

'We then come back the same time the next day to count taxis for another two hours,

'to see what proportion of them we've tagged the day before.

'Now into the warm for some maths.'

So there we are, we have counted taxis on two separate days for two hours each session.

We've fed all the figures into the computer

so now it is the moment of truth.

How many taxis did we count?

The number of taxis we spotted on both days, having run them

through the computer, is 321.

So we now do the same maths that we did with the ping-pong balls,

and it should give us our estimate.

So the second day's numbers divided by the number of repeats.

Equals 6.64 or roughly a sixth of the cabs we saw on day two had been

marked the day before as well.

So all we need to do is take 6.64

and multiply it by the number of cabs we saw on day one to

get our estimate of the number of cabs on London's streets.

The total estimate is 12,140. With some decimal places.

'So how accurate is that? I know just the person to ask.

'Bob Oddy is a long-time taxi driver

'and now General Secretary of the Cabbies' Union.

'So what did he think of our number?'

Well, the total number of taxis licensed in London would be about 23,000 -

-give or take a dozen or so.

-We were miles out! Wow!

-But you're talking about the number of cabs working at any one time.

-Yes.

Well, allowing for day shift, night shift, overlaps,

11-12,000.

We were spot on!

Bob, thanks ever so much.

Taxi!

So this capture recapture system worked very well for us

and it does work in quite a lot of places.

As for me, I will be happy to catch a London cab any time.

But as far as counting was concerned, never again.

It's a good job taxis work in shifts. Imagine the chaos

if they all crowded onto the roads at once.

But there are times when PEOPLE simply can't avoid

crowding together - at rush-hour, sports events and big rock concerts.

One-two, one-two.

When you get a large crowd, you can have hundreds of tons

of people sloshing around like a liquid.

When that happens you get the human version of flows,

waves and pressures building up.

I've come to Bucks New University to find out how that is measured

and what it's like to be in the thick of it.

This is Professor Chris Kemp, an expert in crowd safety.

He has designed a pressure suit capable of monitoring impact

and temperature readings from anywhere in the crowd.

One, two, three, four - let's go, guys!

I'm going to put the suit into action at this specially staged concert.

Like most of us, I've headed straight for the front.

Just run in.

Chris directs wave after wave of sweaty students

to pile on the pressure.

It's a bit of a squeeze to say the least!

With about 100 of them charging into me, this was a pretty realistic simulation.

Chris, I've not felt crowd pressures like that

since Friday nights out in Telford in the late '80s.

I remember bars where you could be up there

and lift your feet off the floor and you don't fall.

What do the numbers say from your read-outs?

This is where the first row of people hit you, OK?

I remember.

Then it goes down because the pressure isn't sustained.

Is that a significant difference?

It is, because it is one pound per square inch.

This is where the second row hits you, then the third row,

then the fourth row, etc.

The pressure on the barrier was 2.67 kilonewtons per metre.

To translate, that is over a quarter of a ton of crowd pressure.

That's like a small horse falling on you. It is!

Is that typical of an intense gig or does it get bigger than that?

It does. The biggest recorded crowd pressure that

we know about is 8.6 kilonewtons at a gig.

But that has just been for a second. It is when it is sustained that it's dangerous.

If you take Hillsborough, that was sustained pressure in one small area with a lot of people.

That's why the fences were taken down because there was no way out.

Research has shown that a sustained 1.2 kilonewtons

for 15 minutes is enough to be fatal.

Are there times when it really drops off or times when it really peaks?

What does happen is that if you are on a barrier, a wall,

or a fence, you have the ability to push backwards,

but then if people are coming forwards, one metre to one-and-a-half metres,

the people there have the double pressure coming into them.

That's where you have got to watch a little bit.

So the message is don't stand a couple of rows

back from the front if you want to avoid the highest pressures.

But pressure isn't the only thing to watch out for in a crowd. There's also heat.

When you first came into the pit the temperature around you was 24 degrees.

As you gradually go through there's a curve upwards to 32 degrees

over a half an hour period.

That's an eight degree increase in the temperature around you.

-That's quite high.

-And it felt high.

Would you say that heat is almost more of a danger in big crowds than pressure?

It can be, and it's interesting when we record this

because last summer at a very hot festival we recorded

a 14 degree increase in temperature on two of the girls who were in the pit.

That's because they were very small and the lads around them

were very tall and it traps the air inside that so it can't get out.

But if you do get into trouble what's the best time to get out?

Pressure drops significantly when people put their hands in the air to clap at the end.

-Right.

-The actual body mass of the arms is taken out of the equation. It's in the air.

If you want to move when you're in a crowd like that,

wait until the end of the song and then sneak through.

What we want is for everybody to be as safe as possible

so anything we can do to support that we will do.

What an amazing crowd you are. You're so amazing.

It's time for this week's brain teaser with the great

brain teaser himself Dr Yan. Yan? Yan?

This week I'm going to try and guess how many buses there are in the whole of London,

but unlike Johnny Ball I'm not going to do any counting whatsoever.

Can you guess how I'm going to do it? I'll give you a clue.

The answer is hopefully all around me.

As always, you can find Yan's answer on our website,

and whilst you're there follow the links to the Open University

for more crowd science.

Don't forget to check for details of the Bang live roadshows.

You can get hands on with us in Edinburgh in a couple of weeks.

Then we are off to Sheffield and Poole.

Tickets are free from our website.

OK. So far we've been looking at the problems with crowds, but we've all seen schools of fish

or flocks of birds moving beautifully as a single unit.

Almost as if they have a collective consciousness

and this is one of science's greatest mysteries.

It got me thinking, could human beings behave the same way?

In about 20 minutes or so, this cinema is going to fill up

with a few hundred people, fingers crossed.

They will be taking part in an experiment

and the thing is they have no idea about what this experiment is about.

And I'm not going to tell them anything,

but it all comes down

to this plastic paddle with a red and a green side.

The question is, will they be able to figure out for themselves what it's all about?

Our guinea pigs in this social experiment are visitors to Birmingham's Giant Screen.

Each one of them has been given one of the reflective paddles on their way in.

And watching them all from beneath the giant screen are cameras which

record which side of the reflective paddles they are holding up.

Our crowd don't know it yet but the experiment starts as soon as they sit down.

People are looking at their paddles, everyone is looking at it and wondering what on earth

it's for, like "What is this for?" Look, here's something interesting, look. Here we go.

Suddenly everybody's holding their paddle up to the screen...

..and they're making the connection now almost instantaneously.

Just a couple of people did it and suddenly everyone did it.

You can see them pointing with their fingers. "There's me. There's me."

Another thing the audience don't realise is that we've actually divided them into two teams.

We're going to introduce something else - the classic video game Pong.

Obviously we've updated the graphics a bit, but the aim is still

to bounce the shark across the screen past the opposing team's bat.

The teams have to work together to control their bat.

It'll only move right to the top if they all showed green at once

and the more red that they show, the further down it moves.

That's amazing because it's all about cooperation.

Between them they have realised that some people have to be red

and some people have to be green.

It's difficult to keep it moving because you've got to get the right

amount of people showing red and the right amount of people showing green

depending on where you want it.

Obviously these guys are just sensing each other,

feeling it, and working it out amongst themselves.

FROM CROWD: Right, go red.

Oh, they just got it in time.

In hardly any time at all each team is suddenly working as one.

CHEERING

Here's the incredible thing. This has happened with no instruction whatsoever.

CHEERING

Pong was always my favourite videogame.

CHEERING

APPLAUSE

What made you decide, "I will do a bit of green, no, I will do a bit of red"?

I know most people are going to go red because everyone was

shouting red, we'll go green.

I can't believe the way it works.

How that's coordinated I've no idea.

I didn't think they would get that so quickly.

You see what we can do when we work together?

If that kind of cooperation is possible,

even at a subconscious level,

you wouldn't know it in the chaos of morning rush-hour.

Up and down the country, as the trains are pulling in, it's every man for himself.

Britain's population recently passed 70 million and the majority of these people live in our cities.

Huge numbers like these can create real challenges for urban planners

because they have to make sure that crowds that big

can move around quickly and safely.

Delays and queues aren't the only worries.

Tragedies can and do happen,

especially during emergency evacuations.

I've come to a very windy vantage point

high above the streets of London to find out how

scientists are tackling the problem.

Andrew, from here when you look at that massive crowd it does look

fairly organised and calm despite the number of people.

That's right.

Especially at large densities, you start to see collective behaviour emerging.

The crowd doesn't just act as individuals on their own.

It starts to exhibit good behaviour.

Andrew uses computer models to analyse the way crowds move

through a cityscape.

This can help him predict bottlenecks

and ultimately to make cities safer for us all.

Aside from razing everything to the ground and starting again,

what can we do to deal with the growing number of people

moving into our cities?

It would be lovely to demolish everything

and start again, wouldn't it?

We have to work with the cities we have. The only way that is good to happen is

if we use the new technologies that are emerging to understand

the crowd and even to start to influence the crowd in subtle ways.

'With his colleague Anders Johansson from the University of Bristol,

'Andrew has been studying how crowd flow is affected by the most common

'bottleneck - the doorway.

'They've asked me to round up some friends to help carry out an experiment.'

As an added extra incentive we've got some cupcakes at the other

end of the doorway.

There are not enough cupcakes for all of you.

The challenge is to get to that cupcake without actually killing

the person next to you.

-Are you guys ready? ALL:

-Yes.

OK, three, two, one, go!

SHOUTING

Whoa!

Filter through, filter through.

SHOUTING AND LAUGHTER

-They are really packing through.

-20.75 seconds.

There was a lot of jamming and then flowing again, jamming and then flowing again. Is that normal?

What we are see during evacuation conditions,

we have periods of total blockage

and then sudden outbursts of small groups, intermittent outflows.

OK. Really that's a classic example of how what can go wrong

when too many people are trying to rush through a tiny narrow

-entrance like that.

-Exactly. This is the faster-is-slower effect.

The more that people push, it lowers the outflow of people through the doorway.

OK, fair enough.

The team's research has produced some surprising solutions to the problem.

We really want to prevent people from clogging in the doorway.

One way to achieve that is to put an obstacle in front of the door which

will prevent people from clogging, it will split up the crowd.

OK that sounds counterintuitive,

to put an obstacle in that narrow doorway while all of you are

trying to squeeze past. It sounds like it's going to slow everything down.

-But let's see what happens.

-Yes.

-What are we using as an obstacle? A chair?

Let's use you, Liz! We'll put you in front of this!

After what I have just seen I don't think that's a good idea!

Oh, Lord! OK, are you guys ready?

-ALL:

-Yes!

Please don't hurt me! Three, two, one, go!

Whoa! Barging through!

Easy does it, guys. Nice. Keep going, keep going.

16.37. Result.

APPLAUSE

Who knew?

'It's that 20 percent speed increase that excites Andrew and Anders.

'But their discovery is still too radical for many architects.'

It's so counterintuitive that putting an obstacle in front of a doorway

would actually improve the flow,

that quite often building designers don't want to do that in case

it makes people feel less safe.

Until such measures are widely adopted

Andrew can offer us a few techniques to help speed you through doors.

One of the classic tricks is, if there is a single doorway that

a crowd is trying to move through, generally moving around the edge of the crowd

and walking along the surface of the obstacle

will get you there quicker.

Good science if you want to design, say, the Olympic Stadium

and you need to get everyone in and out really quickly.

Exactly. If you visit the Olympic Village you'll find that

every doorway has been designed with science in mind.

If you see a random bollard, it's there for a reason.

-Brilliant thinking.

-That's all for now.

We'll see you in two weeks when we will be looking at phone

and Wi-Fi signals, the effect they have on our health,

and how they could be used to beam free electricity from space.

-Goodbye from us from Oxford Circus. See you soon.

-Bye.

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