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Oh, excuse me!

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Have you ever yawned
because somebody else yawned?

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You aren't especially tired,

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yet suddenly your mouth opens wide

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and a big yawn

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comes out.

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This phenomenon is known
as contagious yawning.

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And while scientists still
don't fully understand

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why it happens,

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there are many hypotheses
currently being researched.

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

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beginning with two
physiological hypotheses

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before moving to a psychological one.

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Our first physiological hypothesis

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states that contagious yawning
is triggered by a specific stimulus,

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an initial yawn.

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This is called fixed action pattern.

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Think of fixed action pattern
like a reflex.

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Your yawn makes me yawn.

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

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in a person nearby
that has observed the act.

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

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

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Basically impossible!

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Another physiological hypothesis

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is known as non-conscious mimicry,

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or the chameleon effect.

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This occurs when you
imitate someone's behavior

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without knowing it,

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a subtle and unintentional
copycat maneuver.

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People tend to mimic
each other's postures.

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

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you might cross your own legs.

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This hypothesis suggests

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that we yawn when we see someone else yawn

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because we are unconsciously copying
his or her behavior.

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Scientists believe that this chameleon
effect is possible

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

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Mirror neurons are a type of brain cell

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that responds equally
when we perform an action

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as when we see someone else
perform the same action.

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These neurons are important
for learning and self-awareness.

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For example, watching someone
do something physical,

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like knitting or putting on lipstick,

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can help you do those same
actions more accurately.

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Neuroimaging studies using fMRI,
functional magnetic resonance imaging,

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

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a specific area of the brain
housing these mirror neurons

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tends to light up,

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

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a yawn!

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

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We will call it the empathy yawn.

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Empathy is the ability to understand
what someone else is feeling

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and partake in their emotion,

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a crucial ability
for social animals like us.

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Recently, neuroscientists have found
that a subset of mirror neurons

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allows us to empathize
with others' feelings

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at a deeper level.

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(Yawn)

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Scientists discovered
this empathetic response to yawning

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while testing the first
hypothesis we mentioned,

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fixed action pattern.

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

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at the mere sound of a human yawn.

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

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Dogs yawned more frequently
at familiar yawns,

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such as from their owners,

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than at unfamiliar yawns from strangers.

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Following this research,
other studies on humans and primates

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have also shown that contagious yawning

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occurs more frequently
among friends than strangers.

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In fact, contagious
yawning starts occurring

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when we are about four or five years old,

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at the point when children

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develop the ability to identify
others' emotions properly.

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

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is based on this capacity for empathy,

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

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

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The next time you get caught in a yawn,

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take a second to think
about what just happened.

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Were you thinking about a yawn?

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Did someone near you yawn?

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Was that person a stranger
or someone close?

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And are you yawning right now?

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(Yawn)

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(Lip smacking)