What makes us yawn?

Yawning is a universal human behavior, yet scientists still don't know exactly why we do it or what purpose it serves. Marshall Brain explores some of the theories behind yawning in this episode.

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Episode Transcript

Speaker 1 (00:00):
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(00:30):
Hi Am Marshall Brain with today's question, what makes us yawn?
The next time you're in a meeting, try this little experiment.
Take a big yawn, cover your mouth out of courtesy,
and watch and see how many other people in the
room yawn with you. There's a good chance that you'll
set off a chain reaction of yawns. In fact, before

(00:51):
you finish here, it's likely that you will yawn at
least once. Just hearing about yawning will sometimes make people yawn.
Just to seeing or hearing someone else yawn makes us yawned.
What's behind this mysterious epidemic of yawning? First, let's look
at what a yawn is Yawning is an involuntary action

(01:13):
that causes us to open our mouths wide and breathe
in deeply. We know it's involuntary because we do it
even before we're born. Research shows that eleven week old
fetuses yawn. There are many parts of the body that
are in action when you yawn. First, your mouth opens
and your jaw drops, allowing as much air to be

(01:34):
taken in as possible. When you inhale, the air taken
in is filling your lungs to capacity. Your abdominal muscles flex,
and your diaphragm is pushed down. The air you breathe
in expands the lungs, and then some of the air
is blown back out. While the dictionary tells us that
yawning is caused by being fatigued at drowsy or board,

(01:56):
scientists are discovering that there is more to yawning. Most
people think not much is known about why we yawn
or if it serves any useful function, and very little
research has been done on the subject. However, there are
several theories about why we yawned. Here are the three
most common. The first is the physiological theory our bodies

(02:19):
induced yawning to draw in more oxygen or remove a
build up of carbon dioxide. This theory helps explain why
we yawning groups. Larger groups produce more carbon dioxide, which
means our bodies would act to draw in more oxygen
and get rid of excess carbon dioxide. However, if our
bodies make us yawn to draw and needed oxygen, wouldn't

(02:40):
we yawn during exercise? A leading expert on yawning has
tested this theory. Giving people additional oxygen didn't decrease yawning,
and changing the amount of carbon dioxide in the subject's
environment also didn't prevent yawning, so this doesn't necessarily seem
to be a very valid theory. Then there's the evolution theory.

(03:00):
Some think that yawning is something that began with our ancestors,
the idea that yawning developed from early man as a
signal for us to change activities or to do something differently.
Then there's the boredom theory. In the Dictionary, yawning is
said to be caused by boredom, fatigue, or drowsiness. Although
we do tend to yawn when bored are tired, this

(03:22):
theory doesn't explain why Olympic athletes yawned right before they
compete in their event. It's doubtful that they're bored with
the world watching them. The simple truth is that even
though humans have been yawning for possibly as long as
they have existed, we have no clue as to why
we do it. Maybe it serves some healthful purpose. It

(03:43):
does cause us to draw in more air, but so
does exercise. There's still much we don't understand about our brains,
so maybe yawning is triggered by some area of the
brain we have yet to discover. We do know that
yawning is not limited demand. Cats, dogs, even ish yawned,
which leads aspect to the idea that yawning might be

(04:03):
some form of communication. For more illness and thousands of
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hs W. Brain Stuff is sponsored by Harry's dot Com.

(04:25):
Get a great shaving experience for a fraction of the price.
The quality of the shave is so important that Harry's
purchased the factory that makes their blades. Fifteen dollars gets
you a set that includes a handle, three blades, and
shave cream. Go to Harry's dot com use the code
brain stuff to save five dollars off your first purchase.