Why we laugh

Hi. I'm going to talk to you
today about laughter,

and I just want to start by thinking about
the first time I can ever remember

noticing laughter.

This is when I was a little girl.
I would've been about six,

and I came across my parents
doing something unusual

where they were laughing.

They were laughing very, very hard.

They were lying on the floor laughing.

They were screaming with laughter.

I did not know what they were laughing at,

but I wanted in.

I wanted to be part of that,

and I kind of sat around
at the edge going , "Hoo hoo!"

Now, incidentally,
what they were laughing at

was a song which people used to sing

which was based around
signs in toilets on trains

telling you what you could
and could not do

in toilets on trains.

And the thing you have to remember
about the English is, of course,

we do have an immensely
sophisticated sense of humor.

(Laughter)

At the time, though, I didn't
understand anything of that.

I just cared about the laughter,

and actually, as a neuroscientist,
I've come to care about it again.

And it is a really weird thing to do.

What I'm going to do now
is just play some examples

of real human beings laughing,

and I want you think about the sound
people make and how odd that can be,

and in fact how primitive
laughter is as a sound.

It's much more like an animal call
than it is like speech.

So here we've got some laughter for you.
The first one is pretty joyful.

(Video laughter)

(Laughter)

Now this next guy, I need him to breathe.

There's a point in there
where I'm just, like,

you've got to get some air in there, mate,

because he just sounds
like he's breathing out.

(Video laughter)

This hasn't been edited, this is him.

(Video laughter)
(Laughter)

And finally we have this,
the human female laughing.

And laughter can take us to some pretty
odd places in terms of making noises.

(Video laughter)

(Laughter)

She actually says, "Oh my God,
what is that?" in French.

We're all kind of with her.
I have no idea.

Now, to understand laughter,
you have to look at a part of the body

that psychologists and neuroscientists
don't normally spend very much time

looking at, which is the ribcage,

and it doesn't seem terribly exciting,

but actually you're all
using your ribcage all the time.

What you're all doing
at the moment with your ribcage,

and don't stop doing it, is breathing.

So you use the [??] muscles,
the muscles between your ribs,

to bring air in and out of your lungs

just by expanding
and contracting your ribcage,

and if I was to put a strap
around the outside of your chest,

it's called a breath belt,
and just look at that movement,

you see a sort of rather gentle,
sinusoidal movement, so that's breathing.

You're all doing it. Don't stop.

As soon as you start talking,

you start using your breathing
completely differently.

So what I'm doing now is you see
something much more like this.

In talking, you use a very fine
movement of the ribcage

to squeeze the air out,

and in fact, we're the only animals
that can do this.

It's why we can talk at all.

Now, both talking and breathing

has a mortal enemy,

and that enemy is laughter,

because what happens when you laugh
is those same muscles

start to contract very regularly,

and you get this very marked
sort of zig-zagging,

and that's just squeezing
the air out of you.

It literally is that basic a way
of making a sound.

You could be stamping on somebody.
It's having the same effect.

You're just squeezing the air out.

Each of those contractions
-- ha! -- gives you a sound.

And now if the contractions run together,
you can get these spasms,

and that's when you start getting
these "haaaaa" things happening.

I'm brilliant at this. (Laughter)

Now, in terms of the science of laughter,
there isn't very much,

but it does turn out that pretty much
everything we think we know

about laughter is wrong.

So it's not at all unusual, for example,
to hear people to say,

"Humans are the only animals that laugh."

Nietzsche thought that humans
are the only animals that laugh.

In fact, you find laughter
throughout the mammals.

It's been well-described
and well-observed in primates,

but you also see it in rats,

and wherever you find it

-- humans, primates, rats --

you find it associated
with things like tickling.

That's the same for humans.

You find it associated with play,
and all mammals play.

And wherever you find it,
it's associated with interactions.

So Robert Provine, who has done
a lot of work on this, has pointed out

that you are 30 times more likely to laugh

if you are with somebody else
than if you're on your own,

and where you find most laughter

is in social interactions
like conversation.

So if you ask human beings,
"When do you laugh?"

they'll talk about comedy and they'll talk
about humor and they'll talk about jokes.

If you look at when they laugh,
they're laughing with their friends.

And when we laugh with people,
we're hardly ever actually

laughing at jokes.

You are laughing to show people
you understand them,

that you agree with them, that you're
part of the same group as them.

You're laughing to show
that you like them.

You might even love them.

You're doing all that at the same time
as talking to them, and in fact,

the laughter is doing a lot
of that emotional work for you,

something that Robert Provine
has pointed out, as you can see here,

and in fact, the reason
why we were laughing

when we heard those
funny laughs at the start,

and why I was laughing
when I found my parents laughing,

is that it's an enormously
behaviorally contagious effect.

You can catch laughter from somebody else,
and you are more likely to catch laughter

off somebody else if you know them.

So it's still modulated
by this social context.

You have to put humor to one side,

and think about
the social meaning of laughter,

because that's where its origins lie.

Now, something I've got very interested in
is different kinds of laughter,

and we have some neurobiological evidence
about how human beings vocalize

that suggests there might be
two kinds of laughs that we have.

So it seems possible that the neurobiology
for helpless, involuntary laughter,

like my parents lying on the floor
screaming about a silly song,

might have a different basis to it
than some of that more polite

social laughter that you encounter,
which isn't horrible laughter,

but it's behavior somebody is doing
as part of their communicative act to you,

part of their interaction with you.
They are choosing to do this.

In our evolution, we have developed
two different ways of vocalizing.

involuntary vocalizations
are part of an older system

than the more voluntary vocalizations
like the speech I'm doing now.

So we might imagine that laughter
might actually have two different roots.

So I've been looking at this
in more detail.

To do this, we've had to make
recordings of people laughing,

and we've just had to do whatever it takes
to make people laugh,

and we got those same people
to produce more posed, social laughter.

So imagine your friend told a joke, and
you're laughing 'cos you like your friend,

but not really because
the joke's all that.

So I'm going to play you
a couple of those.

I want you to tell me if you think
this laughter is real laughter,

or if you think it's posed.

So is this involuntary laughter
or more voluntary laughter?

(Audio laughter)

What does that sound like to you?

Posed? Posed.

How about this one?

(Audio laughter)

(Laughter)

I'm the best.

(Laughter) (Applause)

Not really.

No, that was helpless laughter,

and in fact, to record that,
all they had to do was record me

watching one of my friends listening
to something I knew she wants to laugh at,

and I just started doing this.

Now, what you find is that people
are good at telling the difference

between real and posed laughter.

They seem to be different things to us.

Interestingly, you see something
quite similar with chimpanzees.

Chimpanzees laugh differently
if they're being tickled

than if they're playing with each other,

and we might be seeing
something like that here,

these sort of involuntary laughter,
tickling laughter,

being different from social laughter.

They're acoustically very different.

The real laughs are longer.
They're higher in pitch.

When you start laughing hard,

you start squeezing air out
from your lungs

under much higher pressures
than you could ever produce voluntarily.

So for example, I could never
pitch my voice that high to sing.

And also, as I stay, you start to get
these sort of contractions

and weird whistling sounds,

all of which mean that real laughter
is extremely easy,

or feels extremely easy to spot.

In contrast, posed laughter,
we might think it sounds a bit fake.

Actually, it's not. It's actually
an important social cue.

We use it a lot, we're choosing
to laugh in a lot of situations,

and it seems to be its own thing.

So, for example, you find
nasality in posed laughter,

that kind of "ha ha ha ha ha" sound

that you never get, you could not do,
if you were laughing involuntarily.

So they do seem to be genuinely
these two different sorts of things.

We took it into the scanner
to see how brains respond

when you hear laughter.

And when you do this,
this is a really boring experiment.

We just played people
real and posed laughs.

We didn't tell them
it was a study on laughter.

We put other sounds in there
so to distract them,

and all they're doing
is listening to sounds.

We don't tell them to do anything.

Nonetheless, when you hear real laughter
and when you hear posed laughter,

the brains are responding
completely differently,

significantly differently.

What you see in the regions in blue,
which lies in auditory cortex.