After the last episode about the brain,

a lot of people have asked me

why yawning is contagious.

So today’s question will be, well:

Why is yawning contagious?

And here’s the opening to give you 5 seconds to yawn.

[yawn] Aw shit.

Yawning is a natural and an ancestral behavior

which is common to many animal species.

We can realise that by seeing

how early it appears during gestation [as early as the 13th week].

Here’s Von Baer’s law stating that:

the more ancestral and common to animals a behavior is,

the sooner it appears during gestation

the more specific it is, the later – but it doesn’t matter.

All the vertebrates in the world


All of them.

Apart from giraffes.

A giraffe is a bit like a platypus:

as soon as you see one,

you know it won’t fit in anywhere anyway.

We don’t know why we yawn.

We long thought it was to oxygenate the brain,

But it’s wrong.

We can see that yawning increases awareness… OK.

We think it may cool the brain… OK.

But the truth is: we don’t know what it’s for.

However, we know perfectly well why yawning is contagious.

[yawn] Aw fuck!

If yawning is contagious, it’s because of our ability to empathize,

meaning the ability we have to be mentally

able to put ourselves in someone else’s shoes.

There’s a specific group of neurons responsible for this ability.

And these are called “mirror neurons”.

[Best Visual Effects 2014].

These mirror neurons have been discovered almost by accident in 1996

in Parma, Italy, by a research team led by professor Giacomo Rizzolatti.

Rizzolatti had placed electrodes in a monkey’s head and was studying his brain,

and one day, when he was on a break, he took his sandwich

and he saw on the monitoring screen that the monkey had just made a move.

Except that the monkey had not moved at all.

So he had an idea!

He deduced that in the monkey’s head,

seeing someone move

caused the same activity as making the move itself.


That’s how mirror neurons were “discovered”.

When you do something -for example when you catch something with your hand-

it triggers neurons in your brain, in the motor cortex.

But some of these neurons are also triggered

when you only see someone do this action.

Or when you picture yourself doing this action.

That’s how mirror neurons work.

That means that seeing someone do something,

or picturing yourself doing something,

as far as the brain is concerned, it’s exactly the same as really doing it.

But professor Vilayanur Ramashandran went one step further.

He asked the following question: “if it’s the same for the brain,

how come there isn’t any confusion?

How come the brain

doesn’t interpret the fact of seeing someone grab an object

as the sensation that we are ourselves grabing an object?”

Well, there isn’t any confusion because there are sensory receptors on the skin

-which respond to touch, to pain, to heat;

go watch this video if you don’t know what I’m talking about-

so, the receptors on the skin tell the brain:

“Everything’s fine here, nothing to report.”

So the brain is able to say:

I’m processing the same information but there’s no sensation,

hence it doesn’t happen to me!”

But Ramachandran was not over yet,

so he went another step further and asked:

“And now, what if I anaesthetize completely someone’s arm,

and I make this person (with his numbed arm)

watch someone whose arm is being pinched.”

In the brain this should happen:

seeing someone being pinched should trigger a similar activity in his brain.

Supposedly, the brain should ask the receptors: “Are we being pinched?”

Except that here, it doesn’t happen at all, since the arm is totally numb.

Which leads your brain to think that you’re the one being pinched!

Because your arm is numb.

Even though your arm is numb!

And that’s mad.

Ramachandran pushed it even further.

He didn’t go on anaesthetizing every random guy passing.

You can’t do that.

It’s wrong.

So he went on to see people who had been amputated

saying: “After all

when you’re missing an arm or a leg,


Indeed when someone is amputated, they often

still have sensations in the missing limb,

and still feel the limb moving and reacting to

orders from their brain.

For example the brain can tell the missing hand to open up

and in his head he can feel the hand opening up.

But sometimes this phantom limb can be quite uncomfortable.

It can itch, it can hurt, etc.

And Ramachandran asked himself:

“What happens if someone’s missing left arm is itching him

and he sees someone else getting his left arm scratched

or massaged, if it’s a muscular stiffening?”

Well, the pain is alleviated!

Since the brain doesn’t have any receptors on the missing limb,

since… the limb is missing,

and so the simple fact of triggering the mirror neurons

makes the brain think the itching is gone.

But it goes even further, because Ramachandran is one crazy guy!

What happens with a phantom limb

is that the pain can be absolutely unbearable.

For example if someone has lost his arm,

he can still feel as if his fist is constantly clenched.

And that hurts like hell.

Because it’s painful.

Because it’s like that.

And so Ramachandran had a crazy idea

He invented something cheap.

-really, actually cheap-

He took a shoe box, he removed the top,

put a mirror in the middle, made two holes for the arms and voila!

By putting the valid hand in one of the holes, facing the mirror,

he was able to trick the patient’s brain

into believing that his other hand was back

through the reflection of the valid hand.

And then, Ramachandran told the patient:

“Now focus, and clench both your fists tight.

very very thight!

And when I’ll tell you to, you’ll unclench both your fists at the same time.”

The patient did so and after unclenching their fists

the pain disappeared instantly

and entirely.

Good job, Mr Ramachandran!

Well, except that the pain didn’t disappear completely…

Well, it did,

but temporarily.

So what Ramachandran said was:

“since my invention is cheap and easy to make,

take it home and practice there.”

And after a few weeks, the patients called back saying: “there’s a problem,

the phantom limb is gone.

-You mean the pain is gone? -No!

The pain is gone,

but so is the phantom limb!

I haven’t got sensations from my missing arm anymore.”

-Isn’t that good news?”

-It is.”

So in fact it was good news.

But the question arises: what happened?

What happened was that the brain was confronted to a huge “What The F*ck?!”

Which we know it hates.

Sometimes it says: “your arm isn’t there but it hurts like hell.”

And sometimes, with the mirror box, it says: “well your arm is here in fact!

And it doesn’t hurt!”

And so the brain faces a confusion,

a paradox,

a contradiction,

a “What The F*ck?”,

a “Heavens, what’s that?”,

which it can’t solve rationally.

And we know that when the brain can’t solve a problem, it does the best it can.

And that’s what it does there.

The brain goes into complete denial and says:

“Ok, you know what? There’s no pain, no arm, there’s nothing!


All the informations coming from this limb, phantom or not,

won’t be processed anymore.

Pain, presence, sensation, anything,

it doesn’t exist anymore.”

And the phantom limb disappears.


Well, actually, not quite.

Some patients had the feeling that their arm was gone but not their fingers!

Since the brain hates paradoxes

and doesn’t want to imagine it has fingers floating around,

those patients imagined they had their fingers attached on their shoulders.

Badass brain right there.

He pulled out the big game!

Mirror neurons are also involved in other things.

They are also responsible for the so-called “pre-empathic state”,

the state in which an emotional contagion is possible.

The emotional contagion is the ability to transmit emotions on a contagious way,

kind of like the yawning.

In 2012 a study was conducted on Facebook on nearly 700,000 users.

The object of this study was to see in what way it would impact the users’ mood

if they were to receive more positive messages or more negative ones.

And so, for a few days, they were sent specifically positive messages

or negative messages according to the group they were in.

Of course, no surprises:

those who had received good messages were in a rather good mood,

and those who had received bad messages were in a rather bad mood.

Ethics is not the point here,

it complied with Facebook’s Terms of Service.

-You know, the thing we all agree to without reading-


Anyhow, it highlighted the fact that emotions are contagious.

We all know that: when you scroll through a Facebook wall,

there’s often a picture of a child suffering from cancer

and you’re told to like, to comment or to share,

and you see 680,000 likes, 220,000 shares

and 35,000 comments.

Boris Cyrulnik is also very interested in this topic.

In a radio program,

[link in the description]

he talked about the risks linked to the fact

that we spend more and more time in front of screens, and not with people,

so our mirror neurons are not stimulated anymore.

At least not in the same way.

And we see that everyday,

when we read an email, a text, a comment, etc.

We don’t always know how to interpret the tone of the message.

Sometimes we take it dead serious when it’s really a joke,

Sometimes we take it the wrong way.

There can be a lot of misunderstandings with the messages we get and with their tone.

And what’s fantastic is how we’ve managed to spontaneously solve this problem

with the smilies!

A smiley is a graphic representation of a face using text symbols.

I’m happy.

I’m laughing!

I’m laughing at you.

I’m laughing a lot.

I’m sad.

I’m surprised!

I’ve got swag.

I don’t know.

And when we talk about emotional contagion

we’re only that close of talking about mass manipulation.

An experiment was conducted by the mentalist Derren Brown where he asked publicists

to make an advertising campaign for an unknown taxidermy brand…

in 20 minutes.

So he sent them a cab and arranged an appointment in his office.

The taxi trip was about 20 minutes long so when they arrived

they could tell right away what kind of campaign they wanted.

And when they arrived in the office, there was a closed envelope on the desk.

The publicists explained: we’re going to do this, and that.

At one point Derren Brown opened the envelope

and in there, there was absolutely everything they had thought of.

How did he do that?

So, normally, when it comes to magic, you don’t explain the trick…

but this one helps me make my point.

On the way they took to go to Brown’s office,

he had put advertising posters,

which gave indications about what he wanted.

So while in the cab, the publicists saw those ads without paying attention,

and that’s what gave them the ideas they had to have

for their campaign… for this random taxidermy brand…

no one knows anything about.

And that’s linked to something very popular right now

which has many ethical problems: neuromarketing.

“How can we manipulate your brain

to sell you our products.”

Simply put.

That’s just plain manipulation.

We all saw that ad with the girl eating yoghurt or chocolate

and it seems like she’s about to orgasm.

The idea behind these campaigns,

is to make you use your mirror neurons to think:

“Yeah it’d be cool to feel like that…

and she’s eating a yoghurt.


I know what you’re thinking:

“they really think we’re dumb”

But it works, so be careful!

It triggers unconscious mechanisms in our brain.


So it works.

Let me make myself clear: if your mirror neurons don’t work,

you’re not superman. You fall into one of the following categories:

schizoid personality,



and the likes. [Wasp attack in: 3, 2, 1…]

Where is it?

I heard a Brrrr-Vzzzz-Zmmmm!

Mirror neurons are also responsible for crowd behaviours,

for mass movements.

When you see a flock of birds, a school of fish or a herd of cattle,

there are mirror neurons behind it.

We know that during a mass stampede…

Just imagine a crowd where everyone is quiet and peaceful and 5 minutes later

it’s just an enraged mob where everyone just wants to smash everything up,

we know it’s not in everyone’s intention to smash everything up.

That some kind of collective consciousness has taken over.

People are merely imitating what they think the others will do.

That’s what’s called herd behaviour.

And notably there’s the herd behaviour in financial markets

which can have serious consequences.

In the world of finance, some people will just follow what other people do

instead of making their own analysis and taking their own decisions.

That can sometimes lead to exaggerations.

For example a share will go up 14% instead of 1%

-that’s good-

but it could also lose 19% instead of .5%,

which is not that good.

It can end up with people being fired, it can end up with broken lives.

But that’s only short-term consequences.

On the long-term, it leads to speculative bubbles.

You have people behind their screens thinking “ah, people are buying subprimes.

Subprimes are good, I’ll buy some too.”

And that’s not even too bad, there’s even worse.

The worse is the bank trader thinking:

“ah everybody’s buying subprimes, I’ll buy some, me too.

For all my clients.

And for the bank.

And I’ll talk to my friends about it.

And we’ll make loads of money.”

That creates a disproportionate movement

and when it collapses it causes widespread panic.

And there’s a reason we say “widespread panic”,

It’s exactly the same thing as a mob panicking.

It’s important to understand that today, in August 2014,

we’re still affected by the effects of the subprime crisis…

from 2008!

Mirror neurons are similar to Humans: capable of the best and the worst.

Mirror neurons allowed us to build civilizations,

and to learn by copying others,

and to pass on things like the use of fire, tools, agriculture, language…

All those things that enabled us to settle down and build civilizations.

However, they’re also responsible for our worst behaviours.

Even today we don’t know everything about the brain.

It’s a very complex thing.

And we’re still unable to figure out something that should be obvious:

where does our self-consciousness come from?

What’s certain is that mirror neurons are an essential part of these mechanisms.

And without them, there would be no emotion, no feeling,

no recognition of others,

no art.

Plain and simple: there wouldn’t be anything.

At all!

Until then, stay curious,


and take some time to e-penser (e-think)

French Transcription: Cyril
Correction: Az’ English translation: Edouard
Correction: 3D / Az’
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