Hey, Vsauce. Michael here.
And today we're going to talk about
yawning.
Why do we yawn and why is yawning contagious?
How come when I see someone yawn or even
think about it it makes me
kinda of want to yawn?
First things first, definitions.
When you yawn, you inhale air and
stretch your ear drums.
That's why your ears pop when you yawn.
Now, if you yawn and at the same time
stretch your whole body,
that is called pandiculation.
A common misconception about
yawning is that people yawn
when they need more air,
more oxygen.
But studies have shown that no matter how much
oxygen is in the air around a person,
they won't yawn more or less frequently.
And when people exercise
and their bodies do, in fact,
need more oxygen, they don't yawn more often.
Instead, research has shown that our
first answer most likely lies
in being cool.
When you are
exhausted, tired, deep brain
temperatures increase, but your brain is
like a computer - it operates best
at a very specific temperature.
And so yawning,
bringing all this outside air in through
your ears and your mouth,
cools your facial blood and actually
helps cool down
your brain.
This phenomenon is particularly easy to observe
when parakeets yawn. Researchers have
found that parakeets only yawn within a
very specific range of temperatures.
Too cold outside and yawning will cool
the brain too much.
Too hot and yawning will actually warm
it up. Parakeets are perfect test
subjects for this effect,
because they yawn just like you and me,
except they don't exhibit
contagious yawn.
If you show a person a video of other people
yawning, it's likely that the person
watching will yawn
his or herself, unless you put an
ice pack on their forehead, keeping their brain cooler.
Seriously. The University of Albany has
found that people contagiously yawn
less frequently when they have
ice packs on their head,
which means that yawning to cool your brain
isn't just for the birds.
Studies have shown that
yawning also increases blood pressure, stretches
facial muscles and increases focus.
When you panticulate, you stretch
all of your muscles, making them better
ready to be used
at any moment.
So when it comes to a herd of prey animals,
contagious yawning make sense,
because a herd that
yawns together stays alert together.
Under this theory, yawning is advantageously
contagious, because that first
animal to yawn
acts as a sort of reminder to the rest
of the herd to keep themselves
ready and alert. But, of course, when we say that yawning is contagious, we don't mean
like
a disease.
Instead, it's a bit more closely related
to empathy.
Sympathy is when you are
concerned for others, where you wish
someone was better off.
Empathy is the ability to
recognize and share the emotions that other people
feel. 
Emotional contagion is when
the emotions of people around you
influence the way you feel
without you even having to separate
yourselves from them, like when
being around happy people lifts your spirits or how
anger and fear can lead to mob mentality.
Now,
children with autism, who exhibit
impaired social interaction and
communication,
yawn less frequently than other children
when viewing videos of people yawning.
So,
is yawning an emotional contagion or is it about
empathy?
Well last year, the University of Pisa
found that yawn contagiousness is greatest with
family and then friends and then
acquaintances and lastly strangers.
And a study at Leeds University brought
in participants to take a test that
measured how
empathetic they were.
But before the test began,
amongst them was one person
who worked for the researchers
and this person yawned
every minute for 10 minutes.
Interestingly, the people who wound up
scoring the highest
on the empathy test were also the ones
who contagiously yawned along
the most.
Let's talk more about animal
yawning. What fascinates me so much is that
animals across many species
all yawn, but they do so for different reasons.
Animals like guinea pigs and some monkeys yawn
to intimidate and show their sharp scary teeth.
Some penguins yawn to attract mates 
and when snakes yawn,
it seems to be about realigning their
jaws and opening their tracheas
to breathe better after a big body
disfiguring
meal.
Fish yawn more frequently when water
oxygen levels are low or water heat levels
are high. So, when you yawn you're
participating in the behavior shared
across all kinds of animals,
but most likely you're yawning for
purposes unique to your species -
us humans.
What's really cool is that
yawning is most likely an ancient signal
telling the rest of us humans
"let's do this, let's survive."
And as always,
thanks for watching.
