Why Do We Yawn? 5 Reasons and Why It’s Contagious

Yawning regulates brain temperature, relieves ear pressure, and wakes us up when we’re drowsy or bored. Excessive yawning, meanwhile, is a sign of sleep debt.
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Man sitting at work with cup of coffee yawning

Why do we yawn? And why is yawning contagious?

  • Yawning is a common behavior, but the exact reasons why we yawn are still not fully understood.
  • One theory suggests that yawning helps to cool the brain. Another theory suggests we yawn when we are bored or tired to help us stay alert. Yawning can also relieve ear pressure.
  • While yawning in moderate amounts isn’t necessarily a sign of sleep debt, excessive yawning (more than 20 times a day) means you're almost certainly not getting enough sleep.
  • Scientists also aren't sure why yawning is contagious, but it's though to be linked to empathy and social bonding.
  • The RISE app can help you build 20+ good sleep hygiene habits to help you keep your sleep debt low and your days yawn-free.

You feel it coming. The urge to suppress it is real. After all, its implications are far-ranging — from being seen as tired and sleep-deprived to bored and even rude. Unfortunately, there’s no way to hold back the yawn as you exhale gustily — or try to hide it behind your hand.

We’ve all yawned during a time that’s not socially acceptable. During your professor’s speech, on a Zoom call with your manager, or at the dinner table with your family. Even when it’s socially acceptable, i.e., when you wake up and turn in for the night, yawning still has the stigma of not being at your best self.

So, why do we yawn if it’s a social cue that’s, at best, seen as a sign of fatigue, and, at worst, seen as disrespectful (especially in the Hindu culture)? You may be surprised to hear science views yawning, at least in moderate amounts, as a benign part of human nature. Keep reading to find out more.

What Is Yawning? The Science of It

As simple as a yawn might be, there’s more to it than meets the eye. Robert R. Provine, the pioneer researcher on yawning, once wrote that the yawn is “the least understood, common human behavior.” Even now, almost 40 years later, researchers are still searching for the answers on the why and how of yawning.

While yawning may be similar to taking a deep breath — opening your mouth for a long, deep inhale before letting the air whoosh out — they are not one and the same. Scientists noted physiological differences in heart rate, respiratory rate, lung volume, and other related organs.

There are also different types of yawns:

  • True yawns: Also called “rest yawns“ and “spontaneous yawns,” these yawns usually happen when you’re drowsy, bored, or relaxed. They may be triggered by anxiety, too.
  • Tension yawns: Also known as “aggressive yawns,” “emotion yawns,” and “social yawns," they typically occur during a conflicting or arousing situation.

As you can see, the type of yawn depends on the trigger, which brings us to the question at hand, “Why do we yawn?”

Why Do We Yawn? Science Shares 5 Reasons

RISE app screenshot showing how much sleep debt you have
While yawning in moderate amounts isn’t necessarily due to sleep deprivation, excessive yawning is most certainly a sign of sleep debt, which the RISE app can help you track to manage your yawns.

We typically yawn about 20 times a day. Most yawns occur in the moments after you wake up and before bed. 

Scientists have worked out that yawning is directly connected to thermoregulation (how your body regulates its core temperature). Yawning may be a brain cooling mechanism that can ward off the subjective sleepiness typically correlated with increases in body temperature and the associated declines in mental efficiency. It’s also linked to boredom (no surprise there!), waking us up through various arousal mechanisms, which we’ll soon explain. 

Excessive yawns, i.e., yawning more than 20 times a day, typically indicate sleep debt — the amount of sleep you’ve missed in the past 14 days relative to your sleep need. Sleep debt downgrades how you feel and function while awake — fortunately, it’s debt you can pay back. (Head here for more on sleep debt and how the RISE sleep and energy app can help you get back on track.)

Ahead, we detail the various reasons why we yawn.

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1. Regulates Internal Temperature

Just like the CPU of a computer, the brain generates intense heat out of all body organs. Unfortunately, much of the brain’s functions are temperature-sensitive, with high temperatures associated with cell damage. This makes thermoregulation — maintaining optimal brain temperature within a certain range through cooling mechanisms — key to our survival. On a less severe note, the hotter your brain, the drowsier you feel, which explains why we tend to sleep so much during a fever.

According to a paper published by Guggisberg and colleagues in the Journal of Neuroscience and Biobehavioral Reviews, yawning serves as a potential brain-cooling mechanism to stave off cellular damage and keep you awake. The cooler you feel, the less likely you will doze off.

When you yawn, your facial muscles contract and relax. This boosts blood flow to your neck, head, and face to promote better heat dispersion and lower your brain’s temperature. Opening your mouth to take in ambient air also helps cool your brain down. And if you find yourself tearing during your yawn, know that it’s just another way to blow off steam, or in this case, heat, from your head.

One study involving parakeets showed that when surrounding temperatures increased, so did the frequency of yawning. In another study by Andrew Gallup and colleagues, a warm or cold pack was placed on the foreheads of human test subjects. They observed that the cold pack lowered the rate of contagious yawning while the warm one raised it.

2. Keeps Boredom and Drowsiness at Bay

When we’re bored or tired, we tend to yawn. Here’s how yawning functions as an arousal mechanism to activate the brain:

  • When your surroundings are no longer interesting enough to hold your attention or your brain temperature is higher than normal, the sleep generating system comes alive, making you drowsy.
  • At this point, your brain has to choose between wakefulness or sleep. If it goes with the former, it induces a yawn. When humans yawn, our heart rate significantly rises, suggesting a hike in arousal levels.
  • Yawning also physically stimulates the carotid bodies located in the neck. This enhances arousal and alertness, making you feel more awake.

As you can see, yawns are your body’s reaction to help you stay conscious during passive activities that need little interaction, like listening to a dull meeting or driving long-distance. Research shows we tend to yawn more when repeatedly looking at boring stimuli as opposed to interesting ones.

3. Wakes Us Up

As mentioned earlier, sleepiness is associated with higher temperatures and boredom. Because yawning brings down our core body temperature and intensifies our arousal level, yawning is one way to wake ourselves up when we’re tired. It’s also why we yawn so much in the early morning to shake off the last of sleep inertia, and in the moments before bed as a last bid for consciousness before we turn in.

When we yawn, we also tend to stretch different parts of our body — think the lungs, muscles, and joints. Stretching promotes blood flow and improves oxygen levels, both of which can help you feel more awake. These effects are more pronounced if you hold your stretch for a short while (roughly two minutes).

4. Relieves Ear Pressure

As anyone who has descended in an airplane knows, a rapid change in air pressure can lead to the uncomfortable sensation of blocked ears.

Yawning helps relieve the ear pressure by opening up the eustachian tubes connecting your ears to the back of your throat. This equalizes air pressure in your ears with the surrounding air pressure.

Interestingly, swallowing also opens up the eustachian tube. For that reason, scientists think relieving ear pressure is merely a secondary function of yawning.

5. Soothes the Feeling of Breathlessness

If you’re hyperventilating due to anxiety or stress, your body may resort to yawning.

During hyperventilation, you think you need more air hence the deep inhalation. A yawn repositions the muscles in the upper airway to widen its diameter. There‘s also a 300-400% boost in lung volume. On top of that, yawning expands your rib cage, which tells your brain you’ve taken in enough oxygen to stop feeling breathless.

Why Is Yawning Contagious?

Seeing, hearing, reading, or even just thinking about someone else yawn almost always makes you yawn, too. This is known as ”contagious yawning.”

That makes you wonder, “Why is yawning contagious?”

The exact science behind it isn’t fully known yet. But neuroscientists suspect the yawn contagion is a marker of social empathy. Mirror neurons in the brain are thought to be the mechanism behind contagious yawning. These neurons match our actions to the people around us. So if you see other people yawn, chances are you’re compelled to become a yawner, too, even if you aren’t bored or tired.

A recent study noted that the yawn contagion is higher for strong social bonds (like friends and family members) than weak ones (think acquaintances and strangers). But this phenomenon isn’t just restricted to humans. Some non-human primates also experience it.

For example, a study in the Journal of PLoS One indicated that bonobos (a great ape species) show higher yawn contagion among kin and friends. Another study conducted by Campbell and de Waal discovered that chimpanzees display an ingroup-outgroup bias in contagious yawning. That means the animals are more likely to yawn when they see video clips of familiar individuals yawning versus unfamiliar ones.

Interestingly, women display a higher degree of yawn contagion than men. Scientists think it may be because the fairer sex is generally more empathic than males.

On the flip side, certain neurological disorders that impact one’s social skills may mean they are less prone to contagious yawning. For example, scientific evidence indicates people with schizophrenia and autism have a lower rate of yawn contagion. Relatedly, psychopathic individuals lacking empathy are relatively immune to contagious yawning. Kids under 4-5 years old also don’t practice contagious yawning because their brains aren’t fully developed yet.

Another possible social function of contagious yawning may be as a survival mechanism. Seeing someone yawn makes you subconsciously think they are sucking the air out of the space you’re in, prompting you to yawn to get your fair share of oxygen. In a New York Times article, Dr. Gallup suggests contagious yawning may also be a way to “promote coordinated arousal” in a group. This alerts them to external threats more quickly for enhanced protection.

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Do We Yawn Because We Need Oxygen?

For hundreds of years, we mistakenly believed we yawn because of low oxygen levels in our bodies. Breathing in a lungful of breath is thought to expel the “bad, carbon dioxide-rich air” and improve brain oxygenation.

In 1987, Provine and colleagues disproved this theory. Although not a new study, it uncovered one groundbreaking insight: Breathing in more oxygen or carbon dioxide didn’t change the yawning frequency. This makes sense as unborn babies in the uterus yawn even though their lungs aren’t fully developed.

Why Do We Yawn So Much? How Much Is Too Much?

We typically yawn about 20 times a day. Most yawns occur in the moments after you wake up and before bed.

The book, The Mystery of Yawning in Physiology and Disease, uses the Two Laws of Sleep — sleep debt (part of the sleep homeostatic process) and circadian rhythm (the internal body clock) — to explain this phenomenon:

  • Upon waking up, you experience morning sleep inertia. This is also known as wake-up grogginess, in which yawns peak. If you carry sleep debt, your sleep inertia is likely more intense than usual. This could also mean you yawn more frequently.
  • Past the sleep inertia, the frequency of yawns gradually rises throughout the day, mimicking the daytime buildup of sleep pressure. There’s also a mild spike in yawns during the afternoon, which may be related to the afternoon circadian dip in energy that happens to everyone. If you’re sleep-deprived, chances are you’re yawning more often, too.
  • Pre-bedtime, especially in the three hours before sleep, you yawn even more. Scientists theorized this could be because sleep pressure is at its climax. Once again, sleep debt intensifies sleep pressure, which, in turn, may be associated with a higher frequency of yawns.

How much and when you yawn is also linked to your chronotype, i.e., your ideal sleep-wake preferences. (We’ve detailed everything you need to know about chronotypes here.)

Chronotypes are categorized into early chronotypes (early birds), late chronotypes (night owls), and intermediates (everyone in between).

On average, night owls yawn more often than early birds. Whereas late chronotypes yawn more during the daytime and less in the early evening, early chronotypes yawn less frequently during daylight and more in the evening. Researchers highlighted that the different frequencies between chronotypes support the possibility that the circadian rhythm influences yawning.

So far, researchers don’t have the full story on how yawns, sleep, and the circadian rhythm are connected. But what they do know is that sleepiness and the proximity to sleep determine how much yawning takes place in a day.

On a medical-related note, excessive yawning may be due to brain damage. Think neurological health issues like multiple sclerosis (MS), epilepsy, migraine, and stroke. A small-scale study involving 60 patients with MS discovered that more than one-third of the participants felt their symptoms got better after yawning, with almost half of them noting the relief lasted for several minutes or longer post-yawn. Certain mental health conditions like chronic stress and anxiety and sleep disorders like obstructive sleep apnea can trigger excessive yawning, too.

If you find you’re yawning way more than usual, it’s best to speak with a healthcare professional to identify the root cause.

For the most part, though, excessive yawning is a sure sign of sleep debt.

In other words, it’s in your best interest to keep sleep debt low and stay in alignment with your circadian rhythm to tamp down the yawns. That’s where the RISE app can help. It shows your running sleep debt on the Sleep screen, so you know why you’re yawning more than usual or not.

Stave off the Sleepiness + Boost Your Energy With RISE

RISE app screenshot showing best times to boost your energy
The “Plan an energy boost” feature in the RISE app tells you the best time to level up your energy levels and work against the yawns based on your unique chronobiology.

Even in moderate amounts, yawning can make you feel like you’re sleepy, disengaged, and generally not at your best. Not to worry, though, as the RISE app and our step-by-step Sleep Guide can help.

Aside from helping you keep your sleep debt low, RISE shows your daily energy peaks and dips on your Energy Schedule to help you preempt those yawns. Take advantage of the app’s features like ”Plan an energy boost” to help you supercharge your peaks and stay productive during your dips. Meanwhile, our Sleep Guide is centered around good sleep hygiene protocols to help you consistently meet your sleep need, so you’re less prone to daytime sleepiness and the yawns that come with it.

Get the RISE app today and bookmark the Sleep Guide for better energy and better days.

More questions about sleep answered:

Summary FAQs

Is yawning from a lack of oxygen?

Scientists used to think we yawn due to a lack of oxygen. But more recent research in the 1980s disproved this theory since breathing in more oxygen or carbon dioxide didn’t affect how often one yawns.

Is yawning good for you?

Yawning, in moderate amounts (around 20 times per day), is seen as benign. It helps to cool and regulate our internal temperatures, alleviate boredom and tiredness by waking us up, relieve ear pressure, and soothe the feeling of breathlessness.

Why do we yawn when we’re not tired?

The primary reason we yawn when we’re not tired is to relieve boredom. Other possible reasons include relieving ear pressure and engaging in contagious yawning.

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