The Neuroscience of Yawning 🧠
Why the F#%* Do We Yawn?! (8min Read)
TL;DR Summary:
Yawning isn’t just about being tired—it helps cool the brain, shift between states, and strengthen social bonds.
Contagious yawning is tied to empathy and happens more with close connections.
There are many types: spontaneous, contagious, stress-driven, vocalized, and even interspecies yawns (like humans and dogs).
Yawning evolved over 400 million years ago, serving roles in brain regulation and social signaling.
Despite research, yawning remains a fascinating, mysterious behavior that connects us all.
The Neuroscience of Yawning: Why We Do It, What It Means, and Why It’s So Mysterious
You yawn. I yawn. We all yawn.
But have you ever stopped mid-yawn and wondered, "What’s actually happening in my body right now?"
Or, "Why does seeing someone else yawn make me yawn too?"
Yawning is so universal and yet so elusive.
Scientists have been asking these same questions for decades, and the answers are fascinating, if a bit surprising.
Today, I hope to shed some light on this mysterious behavior.
Let’s dive in!
What Is Yawning, Really?
Picture this: you’re sitting on the couch, your brain feeling sluggish, and suddenly you yawn.
A big one. Instantly, you feel a little more awake, your body just a bit more ready for what’s next.
But why? Is it just about being tired? Bored? Or is there something deeper happening?
Yawning is a behavior controlled by your brain’s hypothalamus—specifically, the paraventricular nucleus (PVN).
The PVN acts like a command center, coordinating signals from neurotransmitters like dopamine, serotonin, and oxytocin.
These chemicals are involved in everything from motivation to mood, but in this case, they trigger a cascade of activity that leads to a yawn.
The muscles in your face, throat, and even your lungs work together in perfect synchrony to produce that long, satisfying stretch.
And it doesn’t stop there.
Recent research has revealed that yawning also activates the motor cortex, the part of your brain responsible for movement, and even areas linked to empathy and social bonding.
So, the next time someone tells you that yawning is just a sign of boredom, you can tell them it’s also a complex neurological event.
Ok, that’s the neuroscience, but why does it happen?!
Why Do We Yawn? The Big Theories
First, what do you think? Why do you think we yawn?
Is it to wake ourselves up? To cool off? To signal something to others?
Scientists have proposed several explanations, and while no single theory has all the answers, each gives us a piece of the puzzle.
Cooling the Brain
Have you ever noticed how your laptop gets hot after hours of use, and you have to let it cool down?
Well, your brain is a bit like that. One leading theory is that yawning helps regulate brain temperature.
By stretching your jaw and inhaling deeply, you increase blood flow to the brain and bring in cooler air, which helps dissipate heat.
It’s like your brain’s built-in cooling fan.
Studies show that yawning frequency rises when the ambient temperature increases—just enough to make the brain too warm, but not hot enough to cause discomfort.
It’s like your body knows the sweet spot for staying sharp.
And if you’ve ever wondered why yawning feels so good when you’re tired, it might be because fatigue causes your brain temperature to rise slightly.
More on that in a minute.
Shifting States of Arousal
Imagine you’re about to fall asleep or trying to wake up.
Yawning often shows up during these transitions, almost like your brain is resetting itself.
Scientists call this the "state change hypothesis."
Yawning might help your brain shift gears—from sleepiness to alertness, or from boredom to focus.
Think of it as rebooting a computer: when your system is running slow, you restart it.
Yawning could be your body’s way of hitting refresh, preparing you for the next activity.
The Evolution of Yawning
Let’s rewind time—about 400 million years. Yawning didn’t start with humans.
In fact, it’s one of the oldest behaviors in the animal kingdom, dating back to jawed fishes.
Early on, it might have been a purely physiological response—like stretching or flexing muscles.
But as animals became more social, yawning likely took on additional roles.
In social animals like primates and dogs, yawning can signal stress, submission, or even dominance.
For humans, it may serve multiple purposes, from cooling the brain to promoting social cohesion.
And while not all species experience contagious yawning, the fact that it exists in humans and a few other animals suggests it has deep evolutionary roots.
Why Do We Yawn When We’re Tired?
Here’s a question I bet you’ve asked yourself: if yawning is about cooling the brain or transitioning between states, why does it happen so much when we’re tired?
The answer might lie in brain temperature and arousal.
When you’re tired, your brain’s activity slows down, and its temperature rises.
Yawning helps counteract this by cooling the brain and increasing blood flow, which might give you a brief boost of alertness.
It’s like pouring a glass of cold water on a hot engine—just enough to keep it running a little longer.
Yawning Types: Not All Yawns Are the Same
If you thought yawning was just yawning, think again.
Scientists have identified a surprising variety of yawns, each with its own context, triggers, and potential meaning.
Some of these types might surprise you—they certainly surprised me!
Spontaneous vs. Contagious Yawns
This is the most basic distinction, and it’s probably the one you’ve noticed most often:
Spontaneous Yawns happen without any external trigger. They’re your brain’s way of regulating itself—whether that’s cooling down, adjusting alertness, or transitioning between states like wakefulness and sleep. Spontaneous yawns are the "default" yawns and occur in almost all vertebrates, from humans to reptiles.
Contagious Yawns are a whole different story. They’re triggered by seeing, hearing, or even thinking about someone else yawning. These yawns are tied to social behaviors and empathy, and they don’t appear in all species. Humans, chimpanzees, and dogs are among the few creatures known to experience contagious yawning.
But Why Is Yawning So Contagious?
Here’s a fun experiment: the next time you’re with friends, yawn dramatically and see how many of them follow suit.
Chances are, at least one will yawn back—and it’s not because they’re all tired.
Contagious yawning is one of yawning’s most intriguing mysteries.
What’s going on here? Well, your brain has special cells called mirror neurons/networks that activate when you observe someone else performing an action.
These neurons are thought to be involved in empathy—they help you "feel" what someone else is experiencing.
So when you see someone yawn, your mirror neurons kick in, and you find yourself yawning too.
But it doesn’t happen equally for everyone.
Contagious yawning is more common among people who are emotionally close, like friends and family.
This has led some researchers to suggest that contagious yawning might have evolved as a way to strengthen social bonds.
It’s like your brain saying, "We’re in this together."
True/Rest Yawns vs. Tension/Aggressive Yawns
Not all yawns signal the same thing. In some animals, yawning is more than a sign of relaxation:
True/Rest Yawns: These are the yawns you experience when you’re sleepy, relaxed, or in a low-arousal state. They often come with stretching and might be part of a transition between rest and activity.
Tension/Aggressive Yawns: These yawns show up in high-stress or conflict situations, particularly in social animals like primates. Picture a tense standoff between two alpha males: a yawn with bared teeth might not mean “I’m tired” but rather “Watch out—I’m on edge.”
Humans don’t often exhibit aggressive yawns, but you might catch yourself yawning more in stressful situations.
It's your body’s way of regulating heightened arousal or anxiety.
The Gelada Yawning Hierarchy: YW1, YW2, and YW3
When scientists studied gelada monkeys (a close cousin to baboons), they discovered that yawns weren’t all the same.
In fact, they found three distinct types, each with its own intensity and social meaning:
YW1 (Covered Teeth Yawn): A gentle yawn where the teeth stay hidden. These are most common in relaxed situations and are often seen in females. Think of this as the gelada equivalent of a casual, low-stakes yawn.
YW2 (Uncovered Teeth Yawn): Here, the teeth are exposed, but the gums stay hidden. These yawns are a little more intense and might signal a slightly heightened state of alertness or arousal.
YW3 (Uncovered Gums Yawn): The "power yawn"—teeth and gums are fully bared, often accompanied by head movements. These yawns are most common in dominant males and are associated with social tension or competition. It’s like a non-verbal “back off” signal.
Interestingly, these yawns seem to serve both physiological and social purposes, with the higher-intensity yawns often acting as a form of intimidation or status signaling.
While this specific categorization isn't used for humans, the concept holds true.
Different types and intensities of yawns convey different information or serve different functions.
But Wait, There’s More
Why the ones we just covered are the big categories, there’s even more, I just don’t have time to break them all the way down!
Vocalized vs. Non-Vocalized Yawns
Vocalized Yawns: Accompanied by a sigh, groan, or other sound. Often linked to social signaling.
Non-Vocalized Yawns: Silent and typically serve a physiological purpose.
Emotion Yawns or Social Yawns
Emotion Yawns: Triggered by heightened arousal or stress, such as before a big event.
Social Yawns: Associated with empathy and connection, often contagious within close social bonds.
Interspecific vs. Intraspecific Contagious Yawns
Intraspecific Yawns: Contagious yawning within the same species, like human-to-human yawns.
Interspecific Yawns: Contagious yawning between species, such as a human yawning triggering a dog’s yawn.
Why Do We Have So Many Types of Yawns?
I bet you would have never guessed how many different types of yawns there were, I know I couldn’t as I researched this blog!
There’s a method to the madness though, each type of yawn serves a specific purpose, from cooling the brain and regulating arousal to signaling social connections or even dominance.
By categorizing yawns, scientists have uncovered a richer understanding of their roles in both individual physiology and social behavior.
Next time you yawn, think about the kind of yawn it might be. Is it spontaneous, or did you catch it from someone nearby? Is it relaxed, or does it carry a hidden message?
The more you pay attention, the more you’ll realize just how much is packed into this everyday act.
The Future of Yawning Research
Despite all we know, yawning still holds many secrets.
Why do some people never "catch" yawns? What’s the full role of the hypothalamus in coordinating yawning? And could understanding yawning lead to new insights into neurological conditions?
One thing is clear: yawning is far more than a simple reflex.
It’s a window into our brains, our social lives, and our evolutionary history.
So the next time you yawn—whether it’s spontaneous or contagious—take a moment to appreciate the science behind it.
Your brain is hard at work, keeping you sharp, cool, and maybe even a little more connected to those around you.
Until next time… Live Heroically 🧠
P.S. Email me back with the number of times you yawned reading or listening to this… I lost count of how many times I yawned writing it!
Supporting Research
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Provine, R. R. (1986). Yawning as a stereotyped action pattern and releasing stimulus. Ethology, 72(2), 109-122. https://doi.org/10.1111/j.1439-0310.1986.tb00611.x
Palagi, E., Leone, A., Mancini, G., & Ferrari, P. F. (2009). Contagious yawning in gelada baboons as a possible expression of empathy. Proceedings of the Royal Society B: Biological Sciences, 276(1676), 3097-3104. https://pubmed.ncbi.nlm.nih.gov/19889980/
Baenninger, R. (1987). Some comparative aspects of yawning in Betta splendens, Homo sapiens, Pan troglodytes, and Macaca mulatta. Journal of Comparative Psychology, 101(4), 349–354. https://doi.org/10.1037/0735-7036.101.4.349
Guggisberg, A. G., Mathis, J., Herrmann, U. S., & Hess, C. W. (2010). The functional relationship between yawning and vigilance. Behavioural Brain Research, 210(2), 175-179. https://pubmed.ncbi.nlm.nih.gov/17337071/
de Waal, F. B., & Preston, S. D. (2017). Mammalian empathy: Behavioral manifestations and neural basis. Nature Reviews Neuroscience, 18(8), 498-509. https://doi.org/10.1038/nrn.2017.72
Silva, K., Bessa, J., & de Sousa, L. (2012). Auditory contagious yawning in domestic dogs (Canis familiaris): first evidence for social modulation. Animal cognition, 15(4), 721–724. https://doi.org/10.1007/s10071-012-0473-2
Gallup A. C. (2011). Why do we yawn? Primitive versus derived features. Neuroscience and biobehavioral reviews, 35(3), 765–769. https://doi.org/10.1016/j.neubiorev.2010.09.009
Brown, B. J., Kim, S., Saunders, H., Bachmann, C., Thompson, J., Ropar, D., Jackson, S. R., & Jackson, G. M. (2017). A Neural Basis for Contagious Yawning. Current biology : CB, 27(17), 2713–2717.e2. https://doi.org/10.1016/j.cub.2017.07.062