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  • 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,

  • shows 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.

  • 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 owner's,

  • 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 all together.

  • 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?

Oh, excuse me!

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B2 TED-Ed yawn yawning contagious hypothesis mirror

【TED-Ed】Why is yawning contagious? - Claudia Aguirre

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    VoiceTube posted on 2014/03/02
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