Why is yawning contagious? - Claudia Aguirre

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*Yaaawwwwwn* Did just reading the word make you feel like yawning yourself? Known as contagious yawning, the reasons behind this phenomenon have been attributed to both the physiological and psychological. It's been observed in children as young as four and even in dogs! Claudia Aguirre visits the many intriguing theories that might explain contagious yawning.

Lesson by Claudia Aguirre, animation by TED-Ed.

Oh, excuse me!

Have you ever yawned
because somebody else yawned?

You aren't especially tired,

yet suddenly your mouth opens wide

and a big yawn

comes out.

This phenomenon is known
as contagious yawning.

And while scientists still
don't fully understand

why it happens,

there are many hypotheses
currently being researched.

Let's take a look at a few
of the most prevalent ones,

beginning with two
physiological hypotheses

before moving to a psychological one.

Our first physiological hypothesis

states that contagious yawning
is triggered by a specific stimulus,

an initial yawn.

This is called fixed action pattern.

Think of fixed action pattern
like a reflex.

Your yawn makes me yawn.

Similar to a domino effect,
one person's yawn triggers a yawn

in a person nearby
that has observed the act.

Once this reflex is triggered,
it must run its course.

Have you ever tried to stop
a yawn once it has begun?

Basically impossible!

Another physiological hypothesis

is known as non-conscious mimicry,

or the chameleon effect.

This occurs when you
imitate someone's behavior

without knowing it,

a subtle and unintentional
copycat maneuver.

People tend to mimic
each other's postures.

If you are seated across from someone
that has their legs crossed,

you might cross your own legs.

This hypothesis suggests

that we yawn when we see someone else yawn

because we are unconsciously copying
his or her behavior.

Scientists believe that this chameleon
effect is possible

because of a special set of neurons
known as mirror neurons.

Mirror neurons are a type of brain cell

that responds equally
when we perform an action

as when we see someone else
perform the same action.

These neurons are important
for learning and self-awareness.

For example, watching someone
do something physical,

like knitting or putting on lipstick,

can help you do those same
actions more accurately.

Neuroimaging studies using fMRI,
functional magnetic resonance imaging,

show us that when we seem someone yawn
or even hear their yawn,

a specific area of the brain
housing these mirror neurons

tends to light up,

which, in turn, causes us to respond
with the same action:

a yawn!

Our psychological hypothesis also involves
the work of these mirror neurons.

We will call it the empathy yawn.

Empathy is the ability to understand
what someone else is feeling

and partake in their emotion,

a crucial ability
for social animals like us.

Recently, neuroscientists have found
that a subset of mirror neurons

allows us to empathize
with others' feelings

at a deeper level.

(Yawn)

Scientists discovered
this empathetic response to yawning

while testing the first
hypothesis we mentioned,

fixed action pattern.

This study was set up to show
that dogs would enact a yawn reflex

at the mere sound of a human yawn.

While their study showed this to be true,
they found something else interesting.

Dogs yawned more frequently
at familiar yawns,

such as from their owners,

than at unfamiliar yawns from strangers.

Following this research,
other studies on humans and primates

have also shown that contagious yawning

occurs more frequently
among friends than strangers.

In fact, contagious
yawning starts occurring

when we are about four or five years old,

at the point when children

develop the ability to identify
others' emotions properly.

Still, while newer scientific studies aim
to prove that contagious yawning

is based on this capacity for empathy,

more research is needed to shed light
on what exactly is going on.

It's possible that the answer lies
in another hypothesis altogether.

The next time you get caught in a yawn,

take a second to think
about what just happened.

Were you thinking about a yawn?

Did someone near you yawn?

Was that person a stranger
or someone close?

And are you yawning right now?

(Yawn)

(Lip smacking)