Why Do We Yawn?

Have you ever wondered why seeing someone yawn makes you feel like yawning?

Yawning is an involuntary deep breath, with your mouth open wide, that’s followed by a slow exhale as your mouth closes. There’s a short pause in the breathing cycle between inhaling and exhaling that doesn’t occur except when you’re yawning.

Yawning is often considered contagious. Seeing someone else yawn, seeing a picture of a person yawning, or even thinking about yawning can make you do it, too.

This article will go over why humans yawn. You’ll also learn why yawning is contagious and what some of the theories about yawning are.

Why We Yawn

In the 4th century BCE, Hippocrates wrote that “yawning precedes a fever.” He said, “Like the large quantities of steam that escape from cauldrons when water boils, the accumulated air in the body is violently expelled through the mouth when the body temperature rises.” Since then, we’ve learned more about yawning but there is still so much that we don’t understand.

Several research-backed theories about yawning include:

• Drowsiness or sleepiness: It’s common to yawn when you’re sleepy. Some people think that yawning is actually stimulating and a counter-measure to falling asleep, but there is little evidence to support this idea. Yawning most likely occurs because you’re feeling drowsy.
• Decreased arousal: Research has also suggested that you’re more likely to yawn when you are in a less stimulating environment (i.e. you’re bored).
• Contagious yawning: If you see another person yawn (or a photo or video of a person yawning) or think about yawning, it can make you yawn—even if you aren’t sleepy or bored.
• Chemical causes: Androgens (like testosterone), oxytocin, and certain prescription medications (like Prozac and other antidepressants) can make you yawn more.

There are also theories about why we yawn that are interesting but are not backed up by strong evidence:

• An ear protective mechanism: While it is true that yawning can equalize pressure between your inner ear and the outside atmospheric pressure by opening your eustachian tube, it does not appear to be an evolutionary adaption to protect your ear. Other actions, like chewing gum and drinking, can also equalize pressure in your inner ear.
• Regulation of brain temperature: It has been observed that a hot and cold pack on your forehead can make you more or less likely to yawn. However, it is more likely that the hot pack induces yawning by decreasing your arousal state, while a cold pack increases arousal and decreases the number of yawns. Your circadian rhythm may also play a role in this response.
• A response to decreased oxygen and increased carbon dioxide: This is one of the oldest ideas about yawning, but there is no evidence to support it.

Why Is Yawning Contagious?

Have you ever seen anyone yawn and immediately catch yourself doing the same? There are three triggers for a contagious yawn:

• Seeing someone yawn
• Seeing a picture or video of a yawn
• Hearing a yawn

Yawning and Empathy

Contagious yawning may have a social meaning. It’s more likely to happen in similar groups—for example, you’d be less likely to yawn when you see your dog yawn than when you see a coworker yawn.

Some scientists think that yawning has an empathic (understanding of feelings) purpose. Research has shown that certain conditions that might affect a person’s empathy, including autism spectrum disorder and schizophrenia, are linked with less contagious yawning. However, autistic people and people with schizophrenia still yawned spontaneously.

Research has also suggested that:

• Babies and young children who have not yet developed socialization skills are less likely to yawn if they see someone else yawn.
• Autistic people, people living with schizophrenia, people who have had a stroke, and people with psychopathic traits may also be less likely to experience contagious yawning. This might be due to their different experiences with empathy and how they perceive faces.

Another theory is that yawning originated as a social, non-verbal way to communicate your state of mind. That said, since yawning is associated with boredom and drowsiness, it’s usually considered disrespectful to yawn in social environments. Yawning can also signify hunger and mild stress.

Benefits of Yawning

Even if we don’t fully understand it, yawning seems to have some benefits.

• Equalized pressure: Yawning equalizes pressure in your inner ear by opening your eustachian tube.
• Social cues: A yawn can offer a clue about how you±re feeling (though this could be a disadvantage, too).
• Stimulating effect: Yawns are thought to stimulate arousal and increase vigilance when you’re sleepy thanks to the mechanical stimulation of receptors in your neck (carotid bodies).

There are also some possible benefits of yawning that have been suggested but are not backed up by evidence:

• Yawning might prevent your lung from collapsing.
• Yawning may renew surfactant in the lungs, which helps with breathing.

Types of Yawns

There are actually several different types of yawning. In fact, you may even be able to stop a yawn by using one of these types.

• Nose yawn: By sealing your lips during the exhalation phase of the yawn, you can actually yawn through your nose.
• Eyes-open yawn: Your eyes typically will close or squint during a yawn. By propping/forcing your eyes to be open, you can actually block or stall the yawn. You can stop others from yawning if you do this. Squinted eyes are a potential trigger to yawning because this facial expression is associated with yawning.
• Clenched-teeth yawn: When you feel the yawn starting, clench your teeth as you inhale. This tends to be described as an unsatisfactory yawn.

Summary

We’re not exactly sure why we yawn. We know that it typically happens when we’re bored or sleepy and it might have benefits for our ears and even our social lives.

We also know that when we see someone else yawn—or even think about yawning—we’re more likely to do it. That said, some people don’t seem to experience contagious yawning.

The next time you yawn, take it as a cue to check in with how you’re doing. Sometimes, a yawn is just a yawn, but it can also be your body’s way of telling you it’s time for bed or that you need to stimulate your mind.