Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey, brain Stuff,
Speaker 1: Lauren Vogelbaum Here. Next time you're in a meeting or
Speaker 1: a group discussion, you can try a little experiment. Take
Speaker 1: a big yawn, covering your mouth out of courtesy, and
Speaker 1: watch to see how many people follow suit. There's a
Speaker 1: good chance you'll set off a chain reaction of deep
Speaker 1: breaths and wide open mouths, and before you finish listening
Speaker 1: to this episode, it's likely that you'll yawn at least once.
Speaker 1: Don't misunderstand. We don't intend to bore you here, but
Speaker 1: just thinking about yawning can make you do it it
Speaker 1: just as seeing or hearing someone else yawn makes us
Speaker 1: do it too. My jaw, for the record, is practically
Speaker 1: itching right now, holding one back. But why do we
Speaker 1: yawn in the first place, and why is it so contagious? Today,
Speaker 1: let's talk about what we know and don't know about yawning.
Speaker 1: Yawning is an involuntary action that causes us to open
Speaker 1: our mouths wide and take a deep breath. Oh, we
Speaker 1: know it's involuntary because we do it even before we're born.
Speaker 1: Yawning has been reported in fetuses as early as eleven
Speaker 1: or twelve weeks old. It's been linked to healthy progress
Speaker 1: during early brain and facial muscular development from around twenty
Speaker 1: four to thirty weeks in grown adult humans. While we
Speaker 1: typically associate yawning with relaxation and drowsiness, your heart rate
Speaker 1: can rise as much as thirty percent during a yawn.
Speaker 1: When we yawn, we increase the flow of blood to
Speaker 1: the brain, so yawning is also assigned or cause of arousal.
Speaker 1: Many parts of the body are in action when you yawn.
Speaker 1: At first, your mouth opens and your jast stretches powerfully,
Speaker 1: allowing as much air as possible to be taken in
Speaker 1: an increasing blood flow to the neck, head, and face.
Speaker 1: Inhale well slowly and deeply, meaning your abdominal muscles flex,
Speaker 1: and your diaphragm contracts and pulls down underneath your ribcage,
Speaker 1: allowing your chest to expand above it and your lungs
Speaker 1: to fill with air. The stretching in your jaw may
Speaker 1: also open up your sinus system and allow airflow there.
Speaker 1: You pause, and then you breathe out more quickly than
Speaker 1: you breathed in. Your diaphragm relaxes, curving back upward towards
Speaker 1: your lungs which deflate a bit, and your jaw relaxes,
Speaker 1: and you probably close your mouth. So this isn't just
Speaker 1: a deep breath. And we know that our bodies control
Speaker 1: yawning and breathing with different mechanisms. Yawning may serve a
Speaker 1: number of functions, especially in different animals. After all, humans
Speaker 1: are not the only animals that yawn. Other mammals, birds,
Speaker 1: and even fish dow too. Some researchers think that yawning
Speaker 1: first evolved about four hundred million years ago in jawed fish,
Speaker 1: and that pretty much all vertebrates yond spontaneously to help
Speaker 1: regulate bodily functions. Though interestingly, the duration of yawns across
Speaker 1: different species seems to be positively correlated to how large
Speaker 1: and complex that species brain is. Like, researchers analyzed over
Speaker 1: a hundred species of birds and mammals and found that
Speaker 1: animals with more brains yawn for longer. In humans, fatigue,
Speaker 1: sleep deprivation, or boredom easily bring on yns. But scientists
Speaker 1: are discovering that there's more to yawning than most people think.
Speaker 1: There's a few hypotheses about why we do it spontaneously
Speaker 1: and why it's contagious in groups. An old hypothesis that
Speaker 1: yawning helps to draw in more oxygen or remove a
Speaker 1: buildup of carbon dioxide in our bodies. This would make
Speaker 1: a bit of sense in contagious yawning because larger groups
Speaker 1: of people off put and more carbon dioxide, which means
Speaker 1: our bodies might want to act to draw in more oxygen.
Speaker 1: But this one has been disproven. Lots of research has
Speaker 1: been done on it, including by Robert Provine, who was
Speaker 1: a developmental neuroscientist at the University of Maryland, Baltimore County
Speaker 1: and a leading expert on yawning. His team found that
Speaker 1: giving people additional oxygen did not decrease yawning, and decreasing
Speaker 1: the amount of carbon dioxide in a subject's environment also
Speaker 1: didn't prevent yawning. These air makeup changes did affect subject's
Speaker 1: breathing rates, however, showing that we breathe and yon for
Speaker 1: different reasons. Furthermore, the bodies attempt to regulate blood oxygen
Speaker 1: levels couldn't explain all yawning because we know that marine
Speaker 1: mammals sometimes yawn when they're underwater and therefore not taking
Speaker 1: in air, and human fetuses in the womb aren't using
Speaker 1: their lungs to breathe either. They receive oxygen through the
Speaker 1: placenta and the millicle cord. More recently, researchers proposed another
Speaker 1: hypothesis that yawning is a way humans and other mammals
Speaker 1: help regulate our brain temperature. The brain releases a certain
Speaker 1: amount of heat, which gets dissipated partially through warmed blood
Speaker 1: flowing from the brain being replaced with cooler blood from
Speaker 1: the rest of the body. It's dangerous for the brain
Speaker 1: to get too warm in humans. Anything above one hundred
Speaker 1: fahrenheit or about thirty seven point eight celsius is hazardous,
Speaker 1: and anything above one of four fahrenheit or forty celsius
Speaker 1: can be deadly. So having an automated mechanism to increase
Speaker 1: blood flow and also ventilate the sinuses of cooler air
Speaker 1: as happens when you yawn, it seems like an evolutionarily
Speaker 1: good play. This has been proven out in rats, in
Speaker 1: which arising brain temperatures will trigger yawning, which will then
Speaker 1: decrease those brain temperatures, and it's been shown to a
Speaker 1: contagious yawning in humans. In the early two thousands, a
Speaker 1: team out of the State University of New York Polytechnic
Speaker 1: Institute led by one Andrew Gallup found that when subjects
Speaker 1: purposefully regulated their brain temperature by breathing through their noses
Speaker 1: or by using cold compresses on their foreheads, it suppressed
Speaker 1: their contagious yawning. Other participants yawned in response to video
Speaker 1: of people yawning about forty eight percent of the time,
Speaker 1: but the subjects cooling their brains only yawned contagiously nine
Speaker 1: percent of the time. Also, a research published just this
Speaker 1: year in spring of twenty twenty six indicated that yawning
Speaker 1: may help your system circulate cerebras spinal fluid and thus
Speaker 1: help remove waste materials from the brain, maybe to help
Speaker 1: get you ready for a good sleep, or maybe to
Speaker 1: help flush you out when you've failed to get a
Speaker 1: good sleep. But okay, oh, we have to talk more
Speaker 1: about that yon contagion thing. Humans are also not the
Speaker 1: only species that can catch a yawn. This has also
Speaker 1: been observed in other social species, including chimpanzees, bonaboes, lions, parakeets,
Speaker 1: and domesticated dogs. Though we should note here that the
Speaker 1: individual response of any given animal to seeing or hearing
Speaker 1: or thinking about another animal yawn can vary significantly. For example,
Speaker 1: adult humans will yawn in response to seeing a yawn
Speaker 1: something around sixty percent of the time. A recent study
Speaker 1: has shown that a fetus will yawn about half the
Speaker 1: time that it's mother yawns about a minute afterwards, perhaps
Speaker 1: due to some kind of physical or chemical prompt But
Speaker 1: after a child is born, yawns don't seem to be
Speaker 1: catching until the kidd in question is four or five
Speaker 1: years old. Perhaps coincidentally, this is around when children usually
Speaker 1: start developing a sense of empathy, so there's another hypothesis
Speaker 1: that contagious year yawning is a test of empathetic response.
Speaker 1: This is backed up by the observation that chimpanzee infants
Speaker 1: don't yawn contagiously either, and whether bonibo catches a yawn
Speaker 1: depends on how close they are to the original yawning individual.
Speaker 1: The yawns of friends and family members are much more
Speaker 1: likely to elicit a contagious yawning response, and the same
Speaker 1: seems to be true of humans. A few studies have
Speaker 1: tried to test this based on yon responses in autistic
Speaker 1: versus allistic children and adults, working off the concept that
Speaker 1: these groups process facial cues and empathetic responses differently. Often
Speaker 1: these sorts of tests will show a subject video of
Speaker 1: someone moving their mouth versus actually yawning, and then measure
Speaker 1: the subject's response from there. But empathy in general and
Speaker 1: the autism spectrum, both relatedly and separately, are very complicated,
Speaker 1: and the results of these studies really only indicate that
Speaker 1: more research is necessary. A leading hypothesis these days has
Speaker 1: to do with yawning occurring around states of bodily change,
Speaker 1: like between sleeping and waking. It also ties back into
Speaker 1: yawning creating increased blood flow to the brain, which can
Speaker 1: help us be more alert. The concept goes that yawning
Speaker 1: is an involuntary response to stressful situations. Some Olympic athletes
Speaker 1: will yawn right before their event. Some dogs will yawn
Speaker 1: when they're anxious like at the vets office, or excited
Speaker 1: like when you come home. It's a way to sort
Speaker 1: of stretch and come into your body and focus, and
Speaker 1: evolutionarily seeing that happening to someone in your group and
Speaker 1: automatically getting in on it too sounds pretty worthwhile, even
Speaker 1: if a yawn just means that your compatriot is sleepy
Speaker 1: and trying to wake up, it'd be good for you
Speaker 1: to join in on the increased vigilance the aforementioned Andrew
Speaker 1: Gallup at a Sunny polytechnic recently ran a study where
Speaker 1: they showed subjects video of people yawning or just moving
Speaker 1: their mouths, and then showed them images that could include
Speaker 1: a threatening stimulus in the form of a snake or
Speaker 1: a non threatening stimulus in the form of a frog.
Speaker 1: The subjects were then asked to pick out the snakes
Speaker 1: and frogs and the images as quickly as possible. After
Speaker 1: watching people yawn, the study subjects became able to identify
Speaker 1: the snakes faster, and only the snakes. This had no
Speaker 1: effect on frog identification. So even though we still don't
Speaker 1: know for sure why we yawn, we do know lots
Speaker 1: of interesting things about it. By the way, there is
Speaker 1: such thing as excessive yawning. It can indicate that something
Speaker 1: in your system is off. Usually that's your sleep quality,
Speaker 1: but it can also be something more immediately serious, like
Speaker 1: a heart attack or stroke, or epilepsy or multiple sclerosis.
Speaker 1: So if you suddenly find yourself yawning a lot, especially
Speaker 1: if you have any other symptoms or changes that seem
Speaker 1: out of place, get in touch with the healthcare provider.
Speaker 1: It probably doesn't count, though, if the yawns you're noticing
Speaker 1: all happened while you were listening to this episode, though
Speaker 1: we hope it wasn't that many. Today's episode is based
Speaker 1: on the articles why do We Yawn? By Melanie red
Speaker 1: Zeki McManus and why is Yawning Contagious? By Josh Clark,
Speaker 1: both on how stuffworks dot Com. Brain Stuff is production
Speaker 1: of iHeartRadio in partnership with how stuffworks dot Com and
Speaker 1: is produced by Tyler Klang. For more podcasts from my
Speaker 1: heart Radio, visit the Aheartradio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows.