Yawning is a common but perplexing human function. Scientists have several theories for why we yawn, but none of them are certain. Common triggers of yawning include tiredness, boredom, waking up and stress. Seeing or hearing other people yawn can also cause you to yawn.


What is yawning?

Yawning is the opening of your airway and mouth to take a long, deep breath of air. It’s a complex muscular movement. In seconds, your entire airway fully dilates (expands). And surrounding muscles powerfully stretch or tense, most significantly around your throat (pharynx). Another term for yawning is oscitation. Scientists don’t know the exact purpose of yawning.

A yawn typically lasts four to seven seconds. It involves the following steps:

  • A long inhale (breathing in) using your nose and then mouth.
  • A brief episode of powerful muscle stretching around your mouth and throat.
  • A rapid exhale (breathing out) using your mouth with muscle tension release.

Yawning is mostly involuntary, meaning you don’t have control over it. And most scientists consider it a reflex. However, you can make yourself yawn by breathing in gradually while retracting the tip of your tongue and opening your jaw repetitively. In addition, seeing other people yawning often triggers one.

More facts about yawning

  • Yawning usually happens in fits of two or three with increasing intensity.
  • A fetus starts yawning in the uterus about 12 weeks after conception. A fetus yawns around 25 times per day, and the frequency of yawning tends to decrease with age.
  • Yawning isn’t unique to humans. You’ve probably seen your cat or dog yawn. Many other animals yawn too, including birds and fish.


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Why do we yawn?

Researchers debate the purpose of yawning, and there’s no clear consensus. Currently, there are three main theories:

  • To “wake up” your brain: The arousal hypothesis states that yawning activates your brain. This theory is tied to the fact that tiredness and boredom tend to trigger yawning the most. Boredom happens when the main source of stimulation in your environment is no longer able to keep your attention. This triggers drowsiness by stimulating your body’s sleep-signaling system. Researchers think that at this moment, your body must make an effort to maintain contact with your external environment. So, your body uses yawning to keep yourself awake. When you yawn, your heart rate increases. This may help you stay alert. Several of your facial muscles tense and stretch during a yawn, which may also help wake you up.
  • To cool down your brain: The brain-cooling hypothesis suggests that brain temperature decreases with yawning due to the intake of excess air and changes in facial blood flow. Studies in both animals and humans show that yawning occurs before, during and after instances of abnormal thermoregulation, like heat stress and hyperthermia (high body temperature).
  • To relate to others: The communication hypothesis is based on the contagiousness of yawning. Researchers who support this theory think that yawning functions as a communication or group synchronization function. They think it might serve to signal boredom or feelings of stress to others around you. Most researchers think social interaction is a minor function of yawning that coexists with a more significant function.

For several years, the main theory was that yawning brings in more oxygen — mainly for your brain. More recently, researchers discarded this theory, as studies revealed that a controlled lack of oxygen doesn’t result in more yawning than usual. In addition, this theory doesn’t explain why a fetus yawns, as a fetus gets oxygen through blood via its umbilical cord.

For the time being, yawning remains a mystery. This is because yawning has complex mechanical, biological, neurological and behavioral influences. It’s hard to know where one influence ends and the next begins. In addition, researchers haven’t studied yawning nearly as much as other human behaviors and functions.

What triggers yawning

Evidence suggests that tiredness is the most common trigger of yawning. Other triggers include:

  • Waking up. It’s common to stretch and yawn at the same time when you wake up.
  • Boredom.
  • Certain stressful events. For example, athletes tend to yawn before a game.
  • Imitating a yawn (which triggers a “real” yawn).
  • Hunger.
  • Seeing or hearing a yawn.
  • Reading or thinking about yawning.

Why are yawns contagious?

In humans and certain social animals, seeing or hearing another yawn can trigger yawning. Researchers call this contagious yawning. And it’s usually difficult to suppress. Once again, researchers don’t know for sure why this happens. But they think it’s related to empathy — our ability to understand and share the feelings of another.

Studies show that the susceptibility to contagious yawning correlates with empathic skills in neurotypical people. In other words, the more empathic a person is, the more likely they are to experience contagious yawning. In addition, several studies have revealed that the susceptibility to contagious yawning decreases in neurodivergent people who have difficulty with social interactions. This typically includes people with autism spectrum disorder.

Research also shows that we’re much more likely to have contagious yawning when we see or hear a close loved one yawn as opposed to a stranger. This also suggests a strong empathetic influence.

Contagious yawning may fit into what psychologists call mirroring (limbic synchrony) — subconsciously copying the body language, behavior, speech and facial expressions of people we’re emotionally close to. Psychologists think it’s a nonverbal way to show empathy.


How do we yawn?

Yawning involves a complex coordination of several muscles in your chest, throat and face. Physical steps of yawning include:

  1. Your diaphragm (a muscular structure that helps you breathe) and rib muscles (intercostal muscles) contract. This causes you to breathe in air.
  2. Your lower jaw (mandible) opens, making a “gaping” of your mouth. It’s possible to yawn without completely opening your mouth. But these yawns aren’t usually as “full” or satisfying.
  3. The tip of your tongue retracts and moves downward. In addition, your larynx (voice box) and a bone in your neck above your larynx (hyoid bone) significantly move downward with the help of certain contracting muscles.
  4. After this, the rate at which you’re breathing in air accelerates. Your soft palate (the back of the roof of your mouth) and part of your pharynx rise. This is when you may hear an inhaling sound. Your ears may also pop due to the opening of your eustachian tubes.
  5. At this point, your pharynx’s diameter has increased three to four times its normal size. And your hyoid bone is as close to your lower jaw as it can be.
  6. Peak forces of certain muscles cause your jaw and pharyngeal muscles to stretch as much as possible. This is when you may stretch other muscles in your body, like your arms. This is also known as the stretch-yawning syndrome or pandiculation. You might also make a facial grimace, have closed eyes and/or have watery eyes.
  7. After this most intense point (climax) of the yawn, your muscle tension releases, and you exhale. Many people let out a sound or vocalization at this point. You may also feel a rewarding sensation.

Scientists think neurotransmitters in your hypothalamus (a part of your brain) play a role in kicking off the yawning process. Yawns are also associated with increased levels of neurotransmitters, neuropeptide proteins and certain hormones.

Conditions and Disorders

Is excessive yawning a problem?

Adults yawn about nine times a day on average. But some people yawn up to 20 times a day, and that’s normal for them. Healthcare providers consider excessive yawning as more than three yawns per 15 minutes several times a day. Some people with excessive yawning claim upwards of 100 instances.

Excessive yawning can be a symptom of certain conditions. It can interrupt your day-to-day. Some cultures consider yawning to be rude, which can also negatively impact your life.

Causes of excessive yawning

Excessive yawning can be a symptom of certain conditions or situations, including:

Many neurological conditions are linked to excessive yawning, too, including:

If you have excessive yawning over a few days, talk to your healthcare provider. If you have excessive yawning and other signs of stroke, like sudden numbness or weakness in your face, arm or leg, get emergency medical care.


Why does my throat hurt when I yawn?

If your throat hurts when you yawn, it’s likely because your throat is irritated with an infection, injury or dryness. Your throat stretches and opens up significantly when you yawn, which can cause more inflammation, and thus, pain. A lot of air is moving through your throat, as well. The dryness can make existing irritation worse.

Possible reasons for throat soreness when you yawn include:

Why do my ears hurt when I yawn?

Yawning opens the tiny tubes that run from the middle ears to the back of your nose and throat called eustachian tubes. They’re normally closed.

One role of your eustachian tubes is to drain excess fluids and secretions from your middle ear. If your eustachian tubes are clogged (eustachian tube dysfunction), you may experience pain in your ears when you yawn

On the flip side, yawning can relieve the ear discomfort and hearing problems you may experience during rapid altitude changes, like in airplanes and elevators. This happens because your eustachian tubes open, fixing the amount of air pressure on either side of your eardrum.

Why do my eyes water when I yawn?

When you yawn, several muscles in your face tense and stretch. Sometimes, this can pull on and stimulate your lacrimal glands, which leads to tears and watery eyes.

Tiredness and fatigue can lead to dry eyes. So, you may just be experiencing yawning (because you’re sleepy) and your eyes’ reaction to dry eyes — lacrimation — at the same time.

A note from Cleveland Clinic

Yawning is a common — yet mysterious — human function and behavior. If you find yourself yawning a lot, first try to figure out why. Are you bored or tired? Have you read a lot about yawning (like this article)? If nothing seems to make sense, talk to your healthcare provider. Excessive yawning can be a symptom of certain conditions and a side effect of certain medications. Together, you can figure out the cause.

Medically Reviewed

Last reviewed on 10/16/2023.

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