Why Do We Yawn When We Are Tired
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You know the feeling well. It is late in the evening, or the middle of a long afternoon, and without any warning your mouth opens wide, you take a deep breath in, and your eyes water a little. You have yawned. A minute later, you yawn again. Then the person sitting next to you yawns too, even though they were not tired a moment ago. It is one of the most ordinary things the body does, and also one of the most mysterious. Everyone yawns, from babies in the womb to old people in their chairs, and animals yawn too, from dogs and cats to fish and birds. Yet the simple question of why we yawn, and why tiredness brings yawning with it, does not have one neat answer. This article explains what we do know, in plain words. It is general information, not personal advice, and if you have questions about your own health, a qualified health professional is the right person to ask.
The short answer is that yawning is linked to tiredness, to changes in alertness, and to the brain’s need to stay awake and working well. When you are tired, your alertness drops, and a yawn seems to be the body’s way of giving itself a small push back towards wakefulness. It stretches the face and jaw, pulls in a deep breath, and briefly wakes up the brain. That is the heart of it, but the full story is richer, because yawning also appears when we are bored, when we wake up, when the room is warm, and when we see someone else yawn. To understand it properly, we need to look at what a yawn actually is, what happens in the body during one, and what tiredness has to do with it.
What a Yawn Actually Is
A yawn is not just opening your mouth. It is a short, automatic sequence that the body runs through without asking your permission. It begins with a slow, deep breath in through the mouth, while the jaw opens wide and the muscles of the face stretch. At the same time, the eardrums tighten slightly, which is why your hearing can feel muffled for a second during a big yawn, and your eyes often water. Then comes a short pause at the top of the breath, and finally a quicker breath out, as the jaw closes and the face relaxes. The whole thing takes about five or six seconds, and when it is over, you usually feel a small lift in alertness, as if you have taken a brief breath of fresh air for your brain.
What makes a yawn different from an ordinary deep breath is that you cannot easily stop one once it has started, and you often cannot start one on purpose. You can open your mouth and pretend, but a real yawn has a feeling to it that a fake one does not, and the body knows the difference. A yawn is controlled by the older parts of the brain, the parts that run breathing, swallowing and other automatic jobs, which is why it happens without thinking and why it is so hard to hold back. Trying to stop a yawn halfway usually makes it worse, and the yawn comes back stronger a few seconds later. This is also why yawning can happen when you are not even aware of being tired: the body notices the drop in alertness before your mind does, and it yawns on your behalf.
Babies yawn before they are even born. Scans have shown unborn babies yawning in the womb, long before they need to breathe air, which tells us that yawning is built into the body from the very beginning. It is not a habit we learn from watching others, although watching others can certainly trigger it. It is part of how the body is wired, and it stays with us for our whole lives. People yawn when they wake up, when they are bored, when they are tired, when they are nervous before an exam or a speech, and even when they are changing from one activity to another. That wide range of moments is a clue: yawning is not about one single cause. It is the body’s general response to a change in state, a small reset that helps the brain adjust.
Why Tiredness Brings Yawning With It
Tiredness is the most common trigger for yawning, and most people have noticed the link in their own lives. After a short night of sleep, or in the late evening when the body is winding down, yawns come one after another. The reason lies in how alertness works. When you are wide awake, your brain is active, your breathing is regular, and your attention is sharp. As tiredness grows, all of that softens. Your breathing becomes slower and shallower, your attention wanders, and your brain’s activity dips. A yawn arrives in that dip, like a small alarm that briefly wakes the system up again. The deep breath brings in more air, the stretch wakes up the muscles of the face and jaw, and the brief rise in heart rate and brain activity pushes alertness up for a short while. Then the tiredness returns, and another yawn follows.
Think of it like a person nodding off at a desk who suddenly sits up straight and shakes their head. The yawn is the body’s version of that shake. It does not cure the tiredness, and it does not replace sleep. It buys a few minutes of alertness, which is often all the body is asking for in the moment. This is why yawns come in clusters when you are tired. One yawn lifts you a little, the tiredness pulls you down again, and the body yawns once more to lift you back up. It is a rhythm, and it goes on until you either sleep or the tiredness passes, for example when you step into fresh air, start moving, or find something interesting that wakes your mind up properly.
The link with the body clock matters here too. Yawning is most common at two times of day: just after waking up, and in the evening before sleep. In the morning, the body is shifting from sleep to waking, and yawns help with that change. In the evening, the body is shifting the other way, from waking to sleep, and yawns appear as alertness falls. The same yawn can therefore mean two slightly different things depending on the hour: in the morning it is part of waking up, and in the evening it is a sign that the body is ready for rest. Both are the same action, and both are the body’s way of managing a change in its state. That is why a yawn in a classroom at three in the afternoon, when energy is naturally low, tells a very different story from a yawn at eight in the morning, when the body is still shaking off sleep.
The Brain, Breathing and the Cooling Idea
For a long time, people believed that yawning happened because the body needed more oxygen, and that a deep yawn filled the lungs with fresh air. It is a neat idea, and it feels true, because a yawn does bring in a large breath. But research has shown that the oxygen idea does not hold up on its own. People do not yawn more when the air has less oxygen, and giving people extra oxygen does not stop them yawning. Breathing matters to a yawn, but the reason is probably not about oxygen alone. The deep breath is part of the yawn, not the whole purpose of it.
A newer idea, which many researchers find convincing, is that yawning helps to cool the brain. The brain works hard and produces heat, and like any hard-working part of the body, it works best within a certain range of temperature. When the brain becomes a little too warm, for example when you are tired, or when the room is warm, a yawn may help to bring its temperature down. The deep breath pulls in cooler air, the stretch of the jaw increases blood flow around the head, and the watering of the eyes and the tightening of the eardrums are all part of that cooling process. People tend to yawn more when the air is warm than when it is cold, and holding something cold against the forehead has been shown to reduce yawning in studies. None of this is final proof, and scientists are still debating it, but the cooling idea fits a lot of what we see: yawns come when the brain is warm and tired, and they bring a brief feeling of freshness.
There is also a link with alertness that goes beyond temperature. The brain has systems that keep us awake and systems that let us sleep, and they take turns through the day. When the waking system grows tired, the sleeping system begins to take over, and yawning appears in that hand-over. The yawn briefly wakes the alertness system back up, like a nudge to a person who is drifting off. This is why yawning often comes just before sleep, and also just after waking, at the two moments when the balance between waking and sleeping is changing hands. It is a small, automatic act that helps the brain manage the shift, and it is a reminder of how much of our daily life is run by systems we never think about and never control.
Why Yawning Spreads From One Person to Another
One of the strangest things about yawning is that it spreads. You see someone yawn, and a moment later you yawn too, even though you were not tired. You read the word yawn, or you think about yawning, and you feel a yawn coming on. This is often called contagious yawning, and it is real. It has been shown in study after study: people who watch a video of someone yawning are much more likely to yawn themselves than people who watch a video of someone smiling or laughing. The effect is strongest between people who are close, like family members and friends, and weaker between strangers, which tells us something interesting about what is going on.
The best explanation we have is that contagious yawning is linked to the way the brain understands other people. When you see someone yawn, your brain briefly mirrors what it sees, almost as if it is trying on the other person’s state for a moment. This mirroring is part of how we understand each other at all: we read faces, we copy expressions, and we feel a little of what the other person feels. Yawning is one of the clearest examples of this, because it is so easy to measure. Children begin to catch yawns from others at around the age of four or five, at the same time as they begin to understand what other people are thinking and feeling. People who find it harder to read other people’s feelings tend to catch yawns less often. None of this means that catching a yawn makes you a kind person, or that not catching one makes you unkind. It simply shows that yawning is connected to the social parts of the brain, and not only to tiredness.
Animals catch yawns too. Dogs are famous for it: a dog that sees its owner yawn will often yawn back, and it yawns more for its owner than for a stranger. Chimpanzees catch yawns from each other, and so do some birds. This suggests that contagious yawning is old, much older than human language, and that it may have helped groups of animals stay in step with each other. If one member of a group becomes sleepy, the others begin to feel sleepy too, and the whole group rests together, which is safer than resting one at a time. Whether that is the true reason or not, the effect is easy to see in everyday life. In a classroom, a meeting, a bus or a family room, one yawn is rarely the last. It moves around the room like a quiet wave, and within a minute, half the people in the room have yawned, each of them wondering why they suddenly feel tired.
Yawning When You Are Not Tired
If yawning were only about tiredness, we would only yawn when we are tired. But we do not. People yawn when they wake up, when they are bored, when they are nervous, when they are about to do something important, and when they are changing from one activity to another. Athletes yawn before a race. Musicians yawn before a performance. Students yawn before an exam. In these cases, the person is not sleepy at all. They are alert, excited and a little nervous. So why would they yawn? The answer seems to be that yawning is not only about sleepiness. It is about a change of state, and the moments before a big event are exactly such a change. The body is shifting from rest to action, from calm to focus, and a yawn helps it make that shift.
Boredom is another common trigger, and it is a revealing one. When a task is dull, or a talk goes on too long, or you are sitting still with nothing to hold your attention, yawns arrive quickly. This is not because boredom makes you sleepy in the same way that a short night does. It is because boredom lowers alertness. Your brain is not being asked to do anything interesting, so its activity drops, and the yawn arrives to lift it back up. That is why a boring lecture can make a whole room yawn, while an interesting one keeps everyone awake even late in the day. The yawn is the brain’s way of saying that it needs more to do, and when the task becomes interesting again, the yawning usually stops.
Yawning also appears at moments of change in the body itself. People often yawn when they move from a cold place into a warm one, or when they have been sitting still for a long time and then stand up. They yawn during a long journey, when the body has been still and the mind has had little to do. They yawn after eating a heavy meal, when the body is busy digesting and energy feels low. All of these are moments when alertness dips or the body’s state is shifting, and the yawn arrives as a small reset. Once you see the pattern, yawning stops looking like a single thing with a single cause, and starts looking like a general tool the body uses whenever it needs a brief lift in alertness or a moment to adjust to something new.
Yawning, Boredom and Low Alertness
It is worth looking more closely at boredom, because it explains so many yawns that have nothing to do with sleep. A bored brain is an underworked brain. When you are doing something that needs no thought, like sitting in a waiting room, listening to a talk you do not care about, or watching a slow afternoon pass, your brain’s activity falls, your breathing slows, and your attention drifts. A yawn arrives in that drift, and it does two useful things. It gives the brain a brief burst of activity, through the stretch and the deep breath, and it signals to you, and to the people around you, that your attention has gone. That signal is honest, even if it is a little rude in a meeting. It says, plainly, that this moment is not holding your mind.
This is also why yawning feels so hard to control in a boring situation. You can sit up straight, you can drink water, you can pinch yourself, and still the yawns keep coming, because the cause is still there: the task is not asking enough of your brain. The only real fix is to change the task, or to change your state. Standing up, walking for a few minutes, opening a window, or switching to something that needs your attention will usually stop the yawns far better than trying to hold them back. This is useful to know, because it means a yawn in a classroom or a meeting is not always a sign of a bad night’s sleep. Sometimes it is a sign that the mind is underused, and the honest answer is to make the work more interesting, not to blame the person who yawned.
Low alertness also comes from a lack of movement. A body that has sat still for hours, in a warm room, with little fresh air, will yawn more than a body that has been moving. This is one reason long car journeys and long flights are full of yawns. The body is still, the air is warm and dry, the view barely changes, and the brain has little to stay alert for. A short walk, a stretch, or a breath of cool air at a stop will usually clear the yawns for a while, because movement and fresh air wake the brain up in a way that sitting still never will. The yawn, in this picture, is not a fault. It is a message, and the message is that the body needs movement, air or something worth paying attention to.
Children, Older People and Yawning
Yawning looks a little different at different ages, and watching those differences tells us more about what it is. Babies yawn a great deal, and they yawn before birth, which shows that yawning does not need to be learned. A baby’s yawn is a simple, whole-face event, and it often comes with a stretch of the arms and a wriggle of the whole body. Young children yawn when they are tired, when they are bored, and when they wake up, just like adults do, but they do not catch yawns from other people until they are around four or five years old. Before that age, a child can watch someone yawn all day and never yawn back. That change, when it arrives, lines up with the age at which children begin to understand that other people have thoughts and feelings of their own, which is another clue that contagious yawning is tied to the social brain.
Teenagers yawn a lot, and their parents often take it personally, as if a yawn in the middle of a conversation means the teenager is bored or rude. Often, it means something simpler: the teenager’s body clock has shifted later, so they are naturally sleepier in the morning and more alert at night, and they are also often short of sleep because of school, homework and screens. A teenager yawning at breakfast is usually a tired teenager, not a rude one, and the kinder response is to ask about their sleep rather than to scold the yawn. The yawn is information, not an insult, and it is most useful when it is read that way.
Older people yawn too, but often for slightly different reasons. As people age, their sleep becomes lighter and more broken, and their body clock often shifts earlier, so they may feel sleepy in the early evening and wake very early in the morning. Yawning in the evening is therefore common, and it is usually a normal sign of a tired body winding down. Older people also yawn more when they are sitting still for long periods, in a warm room, or after a heavy meal, all of which lower alertness. None of this is a cause for worry on its own. Yawning is a normal part of life at every age, from the womb to old age, and it only becomes something to look at more closely when it changes suddenly, becomes very frequent, or comes with other changes that are new and unexplained.
When Yawning Deserves a Closer Look
Most yawning is normal, and most of the time there is nothing to do about it except rest, move, or get some fresh air. But there are times when yawning deserves a closer look, and it is honest to name them. The first is when yawning becomes very frequent, far more than usual, and it does not go away with rest. A person who yawns dozens of times a day, every day, for no clear reason, may have something going on with their sleep, such as very short or broken sleep night after night, or a sleep pattern that never lets the body rest properly. In that case, the yawning is not the problem itself. It is a signal that the sleep needs attention, and a health professional is the right person to talk to about it.
The second is when yawning comes with other new changes, such as feeling sleepy all day even after a full night in bed, falling asleep at odd times, like during a conversation or at work, or waking up feeling unrefreshed every morning. These can be signs that sleep is not doing its job, and they are worth mentioning to a health professional, because sleep problems are common and many of them can be helped once they are recognised. This article is general information only, and it cannot say what is going on for any one person. It can only say that a sudden change in yawning, especially with daytime sleepiness, is worth a conversation, not a worry on your own.
The third point is a reassuring one: a single yawn, or even a day full of yawns after a late night, is not a sign of illness. Yawning is one of the most normal things the body does, and it has been with us since before birth. The body yawns when it is tired, when it is bored, when it is waking up, when it is cooling down, and when it sees someone else yawn. All of these are ordinary. The best response to everyday yawning is also ordinary: sleep well, move during the day, breathe fresh air, and keep the mind busy with things worth paying attention to. A yawn is a small message from the body, and most of the time, the message is simple. It is saying that it needs rest, or air, or movement, or something interesting to do, and once it gets one of those, the yawning fades away on its own.
My Take:
If you ask me what I think about yawning, my first answer is that I find it strangely comforting. Of all the things the body does, yawning is one of the most honest. You cannot fake a real yawn, you cannot easily hide one, and you cannot stop one once it has begun. It is the body speaking in its own language, without asking your permission and without caring whether the moment is polite. I like that honesty. In a world where people spend a lot of energy pretending to be wide awake, alert and interested, a yawn tells the truth: this person is tired, or bored, or waking up, or simply human. I think we should listen to that truth more often, instead of feeling embarrassed by it.
I think the most interesting thing about yawning is how it connects us to each other. When one person yawns and the whole room follows, something quiet and remarkable is happening. Without a word being spoken, without anyone deciding anything, a group of people has fallen into step with each other. I have seen it in classrooms, in buses, in family rooms and in waiting rooms, and every time it feels like a small reminder that we are not as separate as we think. Our brains are watching each other all the time, copying each other, feeling a little of what the other person feels. A yawn is the clearest proof of that, because it is so visible and so hard to fake. I find it moving, in a small way, that the body has a signal that says, without words, that we belong to the same group and share the same tiredness.
I also think we are too quick to treat a yawn as a sign of rudeness, and I think that is unfair. A student who yawns in class is not necessarily bored or disrespectful. They may have slept badly, they may have woken early, or they may simply be sitting still in a warm room after lunch, when any body would yawn. A worker who yawns in a meeting is not necessarily lazy. They may have been up with a sick child, or working late the night before, or sitting through a long talk that asks nothing of their mind. I believe that when we see a yawn, our first thought should be curiosity, not judgement. The yawn is information. It tells us that someone is tired, or that the room is warm, or that the work is dull. All three of those are useful things to know, and none of them is a reason to scold the person who yawned.
There is something I have noticed about my own yawning, and it is that yawns tell me things about my day before I know them myself. I yawn in the late afternoon, and I realise I have not moved from my chair for hours. I yawn during a long talk, and I realise my mind has wandered far away. I yawn in the evening, and I realise I stayed up too late the night before. In each case, the yawn arrives before the thought. The body knows first, and the mind catches up later. I think this is true of many body signals, and I think we would be wiser if we paid more attention to them. The body is not a machine that breaks without warning. It sends small signals all day long, and a yawn is one of the clearest of them. It says, plainly, that something needs to change: rest, or air, or movement, or something worth paying attention to.
I want to say something about the cooling idea, because it changed how I think about yawning. For most of my life, I believed the old story, that yawning was about needing more oxygen, and it felt like a satisfying answer. Learning that the story is probably wrong, and that yawning may be about cooling the brain, taught me something about how knowledge works. An answer can feel true and still be wrong, and a better answer can arrive later, from careful observation rather than from a good story. I think this matters beyond yawning. We carry many small beliefs like the oxygen story, ideas that feel right because they are simple and familiar, and we rarely stop to ask whether they are actually true. Yawning reminds me to hold my beliefs lightly, and to be ready to change them when better evidence arrives. That is not a weakness. It is how understanding grows.
I also think about yawning in the morning, because morning yawns have a different feeling from evening yawns, and I believe the difference matters. An evening yawn says the day is ending and the body is ready for rest. A morning yawn says the night is over and the body is waking up. Both are the same action, but they belong to opposite moments, and I find that beautiful in a quiet way. It shows that the body does not have one switch for yawning, or one reason for it. It has a tool, and it uses that tool whenever a change is needed. Waking up is a change. Falling asleep is a change. Moving from boredom to interest is a change. The yawn is the body’s way of helping itself through the change, and I think there is a lesson in that for how we live. Change is easier when we give the body a moment to adjust, rather than forcing it to switch in an instant.
If I could change one thing about how people talk about yawning, it would be the shame around it. People cover their mouths, apologise, and look embarrassed, as if they have done something wrong. I understand the politeness of covering the mouth, and I do it myself, but I think the apology is unnecessary. A yawn is not a failure of manners. It is a normal body function, like blinking or breathing, and it deserves no apology. I would rather live in a world where a yawn is met with a smile and a kind question, like whether you slept well, than in a world where it is met with a frown. Kindness, I believe, begins with small things like this, with how we respond to the ordinary signals of other people’s bodies.
I think about children here too, because children yawn without shame, and I believe we could learn from them. A child who is tired yawns openly, stretches, and then falls asleep without worrying about what anyone thinks. An adult who is tired fights the yawn, drinks strong tea, and pretends to be alert, until the tiredness wins anyway. I am not saying adults should fall asleep in meetings, but I am saying that the child’s honesty is closer to the truth. The body needs what it needs, and pretending otherwise does not make the need go away. It only makes the day harder. A yawn is the body’s way of asking for something simple, and I think the wise response is to listen, not to argue with it.
There is one more thing I want to be honest about, and it is that yawning is still partly a mystery, and I like that. Science has given us good ideas, about cooling, about alertness, about the social brain, but no single idea explains every yawn, and researchers themselves will tell you that the full answer is still coming. I find that reassuring rather than frustrating. It reminds me that the body is not a simple machine with a manual we have already finished reading. It is a living system, full of small wonders that we are still learning about, and a yawn is one of the smallest and most everyday of those wonders. We do it a dozen times a day without thinking, and yet we cannot fully explain why. That gap between the ordinary and the unexplained is, to me, one of the most interesting things about being human.
My final view is simple. A yawn is a small, honest signal from a body that is tired, or bored, or waking up, or cooling down, or sharing a moment with the people around it. It is not a fault, it is not a disease, and it is not something to be ashamed of. When you yawn, listen to what it is telling you. If you are tired, rest when you can. If you are bored, find something worth your attention. If you have been sitting still, stand up and move. If the room is warm, open a window and let in fresh air. And if someone near you yawns and you yawn back, smile at the quiet connection between you, because your brain has just done something remarkable without your permission: it has felt, for a second, what another person feels. In my view, that is not a small thing at all. It is one of the kindest and most human things the body does, and it deserves to be understood, not hidden.
One last thought stays with me, and it is about the quiet moments when yawning feels like a comfort rather than a warning. On a long evening at home, with the family around and the day’s work done, a yawn can feel like the body settling down, like a door closing gently on the day. It is not a sign that something is wrong. It is a sign that the day has been lived, and that rest is welcome. I think we should let those yawns come without fighting them, and let the evening be what it is: a slow winding down, a time for rest, and a reminder that tomorrow will come soon enough. The body knows how to rest, and a yawn is one of the ways it tells us that it is ready. I believe that listening to that readiness, instead of pushing past it night after night, is one of the simplest and wisest habits a person can keep.
I also think about the people who yawn the most and get the least sympathy for it, and the first group that comes to mind is night workers. A nurse finishing a long night shift, a guard who has been awake all night, a driver on a road that never seems to end — these people yawn because their bodies are doing something very hard, staying alert when every signal in the body is asking for sleep. I have a lot of respect for that, and I think the yawn of a night worker deserves understanding, not judgement. When they finally reach home and yawn their way through breakfast, they are not being lazy. They are a body asking, plainly and honestly, for the sleep it is owed. If we understood yawning better, I believe we would treat tired workers with more kindness, and we would build days that give them the rest they have earned.
Students deserve the same understanding. I have watched students yawn through early morning classes, and I have heard teachers take it as a sign of disrespect, when it is often a sign of a body clock that runs late and a night that was too short. A teenager’s brain is wired to feel sleepy late at night and to wake slowly in the morning, and when school starts early, yawning is almost guaranteed. I do not think the answer is to scold the yawn. I think the answer is to ask about the sleep, to keep the classroom air fresh, to give the body movement between lessons, and to remember that a yawning student is usually a tired student, not a rude one. The yawn is giving the teacher useful information, if the teacher is willing to hear it.
Finally, I want to say something about how yawning has changed my own days, in a small but real way. I used to fight my yawns, covering my mouth, sitting up straight, drinking strong tea and pretending I was not tired. Now I treat a yawn as a message worth reading. If I yawn in the afternoon, I stand up, I walk, I open a window, or I change what I am doing. If I yawn in the evening, I take it as a sign that the day is ending and that bed is near. If I yawn because someone near me yawned, I smile, because my brain has just done something quietly wonderful. None of this has made me a perfect sleeper, and I still have tired days like everyone else. But listening to the small signals has made my days a little kinder and a little easier, and I believe that is all any of us can ask from a body that is doing its best to look after us.
Frequently Asked Questions
In simple words, what does “why do we yawn when we are tired” mean?
In simple words, it means that tiredness lowers your alertness, and a yawn is the body’s automatic way of giving itself a small push back towards being awake. The deep breath, the stretch of the jaw and the brief rise in activity wake the brain up for a few minutes. The yawn does not cure tiredness or replace sleep. It buys a little alertness while the body waits for rest.
Why do people ask “why do we yawn when we are tired” so often?
People ask because yawning is something everyone does, many times a day, and yet the reason is not obvious. They notice that yawns come when they are tired, when they are bored, and when they see someone else yawn, and they want to know what connects those moments. It is also a question parents ask about children, and workers ask about long afternoons, because yawning is so common that everyone has wondered about it at some point.
Does “why do we yawn when we are tired” change with age or daily routine?
Yes, it can change with age and routine. Babies yawn before they are born, and young children yawn when they are tired but do not catch yawns from others until about the age of four or five. Teenagers often yawn more in the morning because their body clock runs later and they are often short of sleep. Older people often yawn more in the evening, as their body clock shifts earlier and their sleep becomes lighter. Daily routine matters too: a day with little movement, a warm room and a heavy meal will bring more yawns than an active day outdoors.
When is “why do we yawn when we are tired” most noticeable?
It is most noticeable in the early morning, just after waking, and in the late evening, when the body is winding down for sleep. It is also very noticeable in the middle of the afternoon, when energy naturally dips, and during long, still activities like a car journey, a flight or a long meeting, when the body has been sitting still and the mind has had little to hold its attention. In general, yawning feels strongest whenever alertness falls, whatever the hour.
What do people notice first when they ask “why do we yawn when we are tired”?
People usually notice the timing first: the yawns come when they are tired, or when they are bored, or just after they wake up. Then they notice that yawning spreads, because the person next to them starts yawning too. And then they notice that a yawn brings a small feeling of freshness, as if the brain has had a brief breath of air. Putting those three observations together, timing, spreading and freshness, is what makes the pattern easy to see.
How is “why do we yawn when we are tired” different from one day to the next?
It differs from one day to the next because no two days are alike. A day after a short night brings many more yawns than a day after a full night of sleep. A day spent sitting still in a warm room brings more yawns than a day spent moving outdoors. A boring day brings more yawns than an interesting one, and a day when everyone around you is yawning will bring more yawns than a day spent alone. A little variation is normal, and it is the pattern across many days, not one single day, that tells the real story.
Sources
- NHS — general health information: https://www.nhs.uk/
- World Health Organization — health topics: https://www.who.int/
- Centers for Disease Control and Prevention — health information: https://www.cdc.gov/
- Mayo Clinic — general health information: https://www.mayoclinic.org/
- Healthline — general health information: https://www.healthline.com/
