What are we doing when we yawn?

Yawning helps cool a warm brain

Sometimes, a yawn signals a physical or medical issue

In dogs (and perhaps humans), a yawn is one of an arsenal of calming signals

When you yawn, you are:

• Drowsy
• Bored
• Signaling your wish to be left alone
• Imitating another yawner
• Uncertain

Or perhaps all of the above.

When we ask why we yawn, we are engaged partly in science, partly in psychology and partly in sociology. Each field offers an answer.

What happens when you yawn

Current research points to the idea that a yawn helps to cool the brain when its temperatures rise. Yawning, according to a much-cited 2012 study, acts like a radiator “by removing hyperthermic blood from the brain and simultaneously introducing cooler blood from the lungs and extremities, thereby cooling cortical surfaces through convection.”

While it’s long been suggested that yawning is the way the body delivers a boost of oxygen to the brain, researchers say that’s not the case. What the brain gets when you yawn is an injection of blood. 

Contagious yawning

It turns out a lot of people have studied the way yawns seem to be spread like a cold, as one person’s yawn triggers an empathetic yawn of your own.  The 2017 study, "A Neural Basis for Contagious Yawning," published in Cell, suggests a link between a person’s motor excitability and propensity to imitate another person’s yawn. They scanned their subjects’ brains to see whether they yawned in response to another person’s yawn, even when they were instructed not to yawn. Turns out it’s pretty hard to resist yawning when someone else yawns first.

In the yawn-inducing language of the researchers, “[transcranial magnetic stimulation] measures of cortical excitability and physiological inhibition were significant predictors of contagious yawning …. These data demonstrate that individual variability in the propensity for contagious yawning is determined by cortical excitability and physiological inhibition in the primary motor cortex.”

So that clears that up.

Actually, the researchers say the work has implications for understanding epilepsy, dementia, autism and Tourette syndrome.

Signs of a problem

Sometimes, a yawn signals a physical issue, from simple drowsiness to a concussion. It is a common symptom of multiple sclerosis, and may also signal a stroke or the sleepiness associated with a concussion. These are serious issues that require medical attention.

The U.S. Centers for Disease Control and Prevention even devotes a page to the perils of drowsy driving, noting that yawning is a clear sign the driver may be impaired. Just as when a person drives drunk, a drowsy driver may have slower reflexes and poorer judgment than a person who is fully awake. This can endanger others.

Yawning, etiquette and social cues

Perhaps you remember attending a party that stretched into the wee hours. Perhaps you noticed a guest who wouldn’t stop talking to a host who appeared increasingly disinterested. Then you saw the host yawn.

Worse, perhaps you’ve been that guest. Or that host.

In this context, the yawn delivers the message that the yawner wishes the conversation to end, without requiring him to say “Will you please go now?” It’s the politest possible way to signal the end of one’s patience.

If you find yourself giving or receiving a yawn in such circumstances, it may be appropriate to re-examine your social choices, or your social graces. 

In dogs, a yawn is one of an arsenal of “calming signals.” It is a cue that the dog is uncertain, as when he realizes he’s in the office of a veterinarian who’s standing above him, staring at him. This behavior is seen in other animals, too, and, if we are honest, in humans who may not be sure how to respond to an unexpected set of circumstances. 

If you’re yawning because you’re always tired or sleepy, consult a health care provider.  You can find a Providence St. Joseph Health provider near you in our online directory. 

Washington: Kathryn Severyns Dement Sleep Disorders Center, Sleep Center for Southwest Washington

Oregon: Providence Sleep Disorders Centers

Montana: Sleep Center at Providence St. Patrick Hospital  

California: Sleep Disorders Center at St. Joseph Hospital, Orange

This information is not intended as a substitute for professional medical care. Always follow your health care professional's instructions.