Why Do Humans Yawn? Unpacking the Theories
Factoring in boredom, fatigue, and other people
Medically reviewed by Smita Patel, MD
Yawning involves a deep inhale with a wide open jaw, followed by a slow exhale and closed mouth. Though researchers don't fully understand its origins, yawning often correlates with sleepiness or when waking from sleep.
Yawning is considered "contagious" because when you see someone else yawn, it often stimulates you to yawn, too.
This article explains the theories and reasons behind yawning and why it can be contagious.
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Theories to Explain Why We Yawn
Yawning occurs as early as 12 weeks of fetal life. It is mostly involuntary, and when it begins, it cannot be suppressed. Researchers suggest several theories to explain why we yawn.
Respiration
Yawning may have something to do with a lack of oxygen. Hypoxia (lack of oxygen) is one of the oldest theories as to why we yawn and dates back to 1755.
This theory suggests that yawning is triggered when blood or brain oxygen is insufficient. The belief is that yawning removes "bad air" from the lungs and increases circulation in the brain. However, when experts measure blood oxygen and carbon dioxide, they find little correlation with yawning.
Yawning increases lung capacity and improves blood flow to the heart, benefiting respiration. Researchers also believe yawning repositions muscles to widen the airway, increasing oxygen in organs and tissues.
Arousal
Some believe yawning is an arousal defense reflex occurring when people are bored or sleepy. Yawning might happen in lower states of consciousness, including the following:
Before sleep
Upon awakening
Boredom
During a monotonous task
Medical conditions, such as multiple brain-stem ischemic strokes or frontal lobe tumors
When intoxicated by psilocybin mushrooms
Because yawning seems to occur less often during stimulating activities like cooking, cleaning, and talking, researchers suggest that yawning promotes arousal and associate it with higher brain activation.
Inner Ear Pressure
If you've ever been on a plane or driven in the mountains, you've likely experienced ear barotrauma—a change in air pressure in your middle ear—that you relieved by yawning.
When you yawn, the pharyngeal end of the eustachian tube opens and closes, equalizing the pressure in your inner ear and relieving these symptoms.
Body Temperature
Researchers have proposed that yawning cools the brain. This theory emerged after noticing that yawning occurs more often in situations in which internal body temperature rises, such as the following:
A yawn can reduce the symptoms of these chronic conditions. Research has also found that yawning is associated with outdoor air temperature. One study found that yawning occurs more frequently in the summer than in the winter, leading researchers to believe that yawning is involved in maintaining internal body temperature.
Yawning in Pets
In addition to sleepiness, a yawning dog may be indicating stress and indifference. Dogs also exhibit contagious yawning, meaning they yawn in response to human yawns.
Why Do We Yawn After Seeing Someone Else Yawn?
Have you ever seen someone yawn and suddenly have the urge to yawn? Contagious yawns have been observed in humans, other mammals, and some birds. It even occurs across species. This type of yawn emerges in early childhood as children learn social skills and cues.
Emotional Contagion
Contagious yawning differs from spontaneous yawning because it's in response to someone else's yawn. Research is not definitive as to whether this results from emotional contagion (an empathy response to familiar people) because study results have been inconsistent or inconclusive.
Reasons for Yawning in Different Situations
Yawning is not fully understood, but many theories exist as to how yawning impacts your body. As a result, you may yawn for different reasons.
1. Boredom
Yawning when bored is common—it keeps the brain awake during passive activities. Your face and neck muscles move when you yawn, which may stimulate the carotid artery. Researchers believe this could increase heart rate and stimulate hormone release.
2. Feeling Tired (or Not)
Tiredness is probably the reason people associate with yawning most, and with good reason. People yawn when they're tired because yawning promotes arousal and activates the brain.
In other words, yawning when you're sleepy is your body's way of trying to help you stay awake. Similarly, when you first wake up, yawning has the same effect.
3. To 'Pop' Your Ears
Chewing gum, swallowing, and yawning are tricks for handling inner ear pressure changes. Though this isn't spontaneous, you can intentionally yawn or mimic part of a yawn to open the eustachian tube while flying or driving through changing elevations.
4. To Regulate Body Temperature
Because one theory points to yawning as a component of regulating internal body temperature, you may notice that you yawn more if you have a fever or it's warm outside.
Yawning for Days and Days: What to Do
Experts consider excessive yawning to be more than three yawns in 15 minutes. Excessive yawning can be caused by the following:
Drowsiness
Disorders that cause daytime sleepiness (some mental illnesses, Parkinson's disease, cancer, and chronic pain)
Vasovagal reaction (stimulation of the vagus nerve)
Stroke
Epilepsy
Multiple sclerosis
Rarely, it can also result from certain medicines or problems with the body's temperature control.
To try and avoid excessive yawning, be sure to:
Get adequate sleep.
Establish good sleep habits.
Consider adjusting prescription medications if they are the cause.
Treat underlying conditions.
Use mindfulness techniques if anxiety is to blame.
Usually, excessive yawning is due to inadequate sleep. However, because some health conditions can cause excessive yawning, see a healthcare provider for a diagnosis if you don't think sleepiness is the cause.
Summary
There are several theories as to why people yawn. These include increasing oxygen to the brain, organs, and tissues, helping you stay awake, relieving inner ear pressure, and regulating body temperature. Yawning is also contagious, though researchers don't fully understand why people yawn in response to seeing other people yawn.
Excessive yawning is usually the result of too little sleep, but it can also be a sign of an underlying health condition or medication side effect. Healthy sleep habits are an excellent place to start, but see a healthcare provider if it continues.
Read the original article on Verywell Health.
