Yawning is something we all do frequently. Sometimes it happens when we feel sleepy, bored, or simply because we saw someone else yawn. But what exactly is a yawn, and why does it happen to you?
What is Yawning?
Simply put, yawning is an involuntary act where you take a deep breath while opening your mouth and airways wide. It is a complex muscular process. In just a few seconds, your entire airway expands, and the muscles surrounding your throat, specifically the back of the throat (pharynx), stretch and tense. Some professionals refer to this as oscitation. Interestingly, scientists have yet to pinpoint the exact reason why we yawn.
A typical yawn lasts about four to seven seconds and involves the following steps:
- First, you inhale deeply, primarily through the nose and then the mouth.
- Then, the muscles around your mouth and throat stretch significantly for a brief moment.
- Finally, as those muscles relax, you exhale quickly.
In most cases, yawning is an involuntary action, meaning it is difficult to stop even if you try. While scientists classify it as a reflex, you can consciously trigger a yawn by keeping your tongue down, dropping your jaw, and inhaling slowly. It is also quite fascinating how seeing someone else yawn often triggers a yawn in you automatically.
Want to learn more about yawning?
Let’s dive a bit deeper into the science of yawning:
- Yawns often come in clusters of two or three, and you might notice each subsequent yawn feels more intense.
- Did you know that even a fetus starts yawning as early as 12 weeks after conception? A fetus may yawn up to 25 times a day, though this frequency tends to decrease as they develop.
- Humans aren't the only ones who yawn. You have likely seen your cat or dog yawn, and many other animals, including birds and fish, exhibit this behavior as well.
Why do we yawn?
Researchers have several theories, though none have been universally agreed upon. Currently, there are three primary hypotheses:
1. To “wake up” your brain?
This is known as the ‘arousal hypothesis.’ This theory suggests that yawning helps activate your brain. We tend to yawn most when we are tired or bored. When you lose focus or become disinterested in a task, your body’s sleep-signaling system may kick in. Researchers believe your body uses yawning as an attempt to re-engage with your environment. When you yawn, your heart rate increases, which may help you stay alert. Additionally, the stretching of facial muscles during a yawn provides sensory input that can help wake you up.
2. To cool down your brain?
This is known as the ‘brain-cooling hypothesis.’ This theory posits that because we inhale cool air and increase facial blood flow during a yawn, it helps reduce the temperature of the brain. Studies on animals and humans have shown that yawning often occurs before, during, or after periods of abnormal thermoregulation, such as heat stress or elevated body temperature (hyperthermia).
3. To connect with others?
This is known as the ‘communication hypothesis.’ It is based on the idea that yawns are contagious. Supporters of this theory believe that yawning acts as a form of non-verbal communication or a way to achieve group synchronization. They suggest it might signal to others that you are tired or stressed. However, many researchers believe social bonding is only a minor function, likely co-existing with other more vital physiological purposes.
For a long time, the prevailing theory was that yawning provides extra oxygen—specifically to the brain. However, recent research has largely dismissed this, as studies showing reduced oxygen intake did not result in an increase in yawning. Furthermore, this theory fails to explain why a fetus yawns, as they receive oxygen through the umbilical cord (blood), not by breathing air.
As it stands, yawning remains a scientific mystery. It involves a complex interplay of mechanical, biological, neurological, and behavioral factors that are difficult to isolate. Furthermore, yawning has not been studied as extensively as other human behaviors.
What triggers a yawn?
Evidence suggests that fatigue is the primary cause, but other triggers include:
- Waking up. It is common to stretch and yawn when you first rise.
- Boredom.
- Stressful events. For example, athletes are often observed yawning before a high-pressure competition.
- Simulating a yawn (which can often lead to a 'real' one).
- Hunger.
- Seeing or hearing someone else yawn.
- Reading or thinking about yawning (Yes, you might even be yawning while reading this!).
Why is yawning contagious?
In humans and some social animals, seeing or hearing a yawn can trigger one in you. Researchers call this contagious yawning. While it is difficult to stop, researchers believe it is linked to empathy—our ability to understand and share the feelings of others.
Studies indicate a connection between empathy skills in neurotypical individuals and their susceptibility to contagious yawning. Simply put, higher levels of empathy may increase your likelihood of catching a yawn. Conversely, some studies suggest that individuals who are neurodivergent, such as those on the autism spectrum, may show a lower tendency toward contagious yawning due to differences in social processing.
Furthermore, research shows that you are more likely to catch a yawn from a close friend or family member than from a stranger, further highlighting the role of empathy.
Contagious yawning may align with what psychologists call ‘mirroring’ (limbic synchrony). This is the unconscious mimicry of body language, speech patterns, and facial expressions among those who are emotionally close. Psychologists believe this is a subtle, non-verbal way of expressing empathy.
How Do We Yawn?
Yawning is a complex coordination of numerous muscles in your chest, throat, and face. Here is the step-by-step physical process of a yawn:
- Your diaphragm (the muscle structure that powers your breathing) and your intercostal muscles (between your ribs) contract. This creates the force needed to draw air into your lungs.
- Your mandible (lower jaw) drops, opening your mouth wide. While you can yawn without opening your mouth completely, such yawns often feel incomplete or unsatisfying.
- Your tongue pulls backward and downward. Simultaneously, your larynx (voice box) and the hyoid bone in your neck shift significantly downward due to specific muscle contractions.
- Next, your inhalation rate increases. Your soft palate and the pharynx (back of your throat) lift. This is why you may hear a rushing sound during a yawn. Your eustachian tubes also open, which may cause a 'popping' sound in your ears.
- By this point, the diameter of your pharynx has expanded to three or four times its normal size, and your hyoid bone is positioned as close to your mandible as possible.
- The maximum exertion of certain muscles causes intense stretching in your jaw and throat. This often extends to other parts of your body, like your arms, a phenomenon known as ‘stretch-yawning syndrome’ or ‘pandiculation.’ You might find yourself squinting, closing your eyes, or producing tears.
- After this peak, the tension in your muscles releases, and you exhale. Most people emit a sound or vocalization during this phase. You may also feel a sense of relief or satisfaction.
Scientists believe that neurotransmitters located in the hypothalamus of your brain play a primary role in initiating the yawning process. Yawning is closely linked to fluctuations in neurotransmitters, neuropeptide proteins, and various hormones.
Is Excessive Yawning a Concern?
An average adult yawns about 9 times a day, though some people may yawn up to 20 times daily as part of their personal baseline. Doctors generally define excessive yawning as yawning several times in a short window, specifically more than 3 times in 15 minutes. Some individuals report yawning over 100 times a day.
Excessive yawning can be a symptom of an underlying medical condition. It may interfere with your daily life or cause social discomfort. If your yawning is significantly impacting your ability to function, it is worth investigating.
Common Causes of Excessive Yawning
Excessive yawning can be a symptom of several medical conditions or circumstances:
- Conditions related to hypersomnia (excessive daytime sleepiness), such as narcolepsy, sleep deprivation, or obstructive sleep apnea.
- Opioid withdrawal syndrome.
- Certain medications, such as SSRIs, apomorphine, or naloxone.
Several neurological conditions are also linked to excessive yawning, including:
- Amyotrophic lateral sclerosis (ALS)
- Epilepsy
- Head trauma
- Migraine headaches
- Multiple sclerosis (MS)
- Stroke
Important: If you have been yawning excessively for several days, please consult your doctor. If you experience excessive yawning alongside symptoms of a stroke—such as sudden numbness or weakness in your face, arm, or leg—seek emergency medical care immediately.
Why Does My Throat Hurt When I Yawn?
If your throat hurts during a yawn, it is likely due to your throat being irritated by infection, injury, or dryness. A yawn stretches the throat to its limit, which can aggravate existing inflammation and cause pain. Additionally, a large volume of air passes through the throat during a yawn, which can worsen pain caused by dryness.
Common reasons include:
- Viral respiratory infections, such as the common cold, flu, or COVID-19.
- Bacterial respiratory infections, such as strep throat.
- Tonsillitis (inflammation and infection of the tonsils).
- Throat injuries, such as minor abrasions from swallowing rough foods.
Why Do My Ears Hurt When I Yawn?
When you yawn, your eustachian tubes—small channels connecting your middle ear to the back of your nose and throat—briefly open. They are usually closed.
One of their jobs is to drain excess fluid and secretions from the middle ear. If your eustachian tubes are dysfunctional (eustachian tube dysfunction), you may feel pain in your ears while yawning.
Conversely, yawning can actually help relieve ear discomfort and hearing issues caused by rapid changes in elevation, such as when flying in an airplane or riding in an elevator. This happens because the yawn opens your eustachian tubes, allowing the air pressure on both sides of your eardrum to equalize.
Why Do My Eyes Water When I Yawn?
When you yawn, several muscles in your face contract and stretch. This movement can pull on and stimulate your lacrimal glands, which is why your eyes may water.
Fatigue can also cause dry eyes. Therefore, you might find yourself yawning because you are tired, while your eyes simultaneously produce tears as a reaction to dryness—both happening at the same time.
What Can We Learn From This?
Yawning is a common yet mysterious human behavior. If you find yourself yawning excessively, first consider the cause: Are you bored? Tired? Did you just read about yawning (like this article)? If you cannot find a clear reason, speak with your doctor. Excessive yawning can be a symptom of a health issue or a side effect of medication. Working together, you and your doctor can get to the root of the issue.
So, the next time you feel a yawn coming on, remember these facts. It’s quite an amazing process, isn't it?
