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New Yorker writer Maria Konnikova tells us how in 1923, neurologist Sir Francis Walshe noticed some interesting things involving yawns and motor reflexes. They led him to conclude that yawning was an act outside our conscious control, deep down where our lizard brains reside. The notion that yawning was a primitive act led British naturalist Charles Darwin to point out that when you see all types of animals yawn, you can’t help but realize how much humans have in common with them. 

When do we yawn?
  • We yawn when we’re sleepy. When we go to bed or when we first get up, some of us stretch and yawn in combination, much like a cat.
  • We yawn when we’re anxious. Anxiousness leads to rapid shallow breathing. Our bodies swing into action when we yawn, expanding our rib cages so we take full, deep, breaths. 
  • We yawn to release tension. Yawning massages and loosens jaw, neck, and throat muscles, allowing them to relax.
  • We yawn when we’re hungry. Most easily accessible evidence is only anecdotal*. I could find no studies that support a direct link, although healthline.com says hunger can trigger anxiety, which in turn triggers yawning.
  • We yawn when we’re bored. When we yawn, our bodies draw in more oxygen and remove more carbon dioxide, presumably to increase alertness. Other than nodding off, yawning is such a good way to indicate boredom that we will simulate yawns to signal to others how dull and tiresome they’re being.

What do sleepy, anxious, tense, bored, and hungry have in common?

At each of these times, the yawn is a signal for us to take some action that benefits us. Neuroscientist Robert Provine says yawns send a signal to our minds and bodies that we are changing from one state to another. Some say it is also a form of social signaling that lets those around us know we are changing.

What is a yawn?

Yawning is an involuntary, sudden, three-phase breathing movement that begins with active inhalation (taking a deep breath). The second phase is the stasis that initiates the change in direction from inhalation to expiration (intake to exhaust, the third phase) and the change of control from active to passive (our lungs empty themselves). 

Yawning is the least understood human behavior

Hippocrates believed yawning signaled an oncoming fever and was the body’s way of removing bad air from the lungs. Two thousand years later, scientific theories gave up on bad air and focused on our circulatory systems. This bunch believed that yawns increased blood pressure, heart rate, and blood oxygen levels, thereby improving our alertness and motor functions. Once scientists had better tools for measuring such things, they found they were not raised by yawning, so back to the drawing board. The next bunch thinks when our brains get overheated, yawning cools them. A few have gone back to the air argument. The jury is still out on yawning and the journal articles keep on coming.

Why is yawning contagious?

Some say it’s merely a matter of involuntary empathy. I found some interesting studies that showed how we yawn more when we see family members yawn than when we see friends yawn. And it doesn’t stop there. We yawn more when we see friends yawn than when we see acquaintances yawn, and more when we see acquaintances yawn than strangers.

This continuum of yawn contagion leads most to conclude our yawning varies by our level of empathy.

Primates exhibit empathetic contagious yawning, too

Monkeys yawn more often around those with whom they have higher levels of social bonding (family, friends) than those they don’t (acquaintances and strangers) and are thus more empathetic to the expressions signaled by yawning: sleepy, anxious, tense, bored, and hungry.

The Yerkes National Primate Research Center in Lawrenceville, Georgia showed short videos of animated chimps yawning to real chimps. The clip from the video above shows one of the viewers yawning in response to the yawn of an animated chimp. The researchers concluded that “contagious yawning is controlled by the same mechanisms that make emotions contagious.”


Many studies find evidence for contagious yawning in dogs and apes, while others don’t, but all insist more studies are needed. Remember, these are academic studies that are splitting statistical hairs to churn out articles that journals will publish. As an example of how far yawn studiers are willing to go in pursuit of publication, Cal State’s Matthew Campbell and Cathleen Cox of the Los Angeles Zoo and Botanical Gardens conclude in one of their studies that “red-footed tortoises did not show evidence of contagious yawning in experimental settings.”

Chasmology is the study of yawning

The word is so new that it’s probably not in your dictionary. Wolter Seuntjens, of the Dutch Academy of Pataphysics, has two laws of Chasmology. His First Law states that yawns occur:

  • When the yawners cannot do what they would like to do.
  • When the yawners must do something they would rather not do.

His Second Law of Chasmology is a special instance of the First Law where the yawn has an erotic and sexual aspect. Two Finnish scientists say yawning stimulates blood flow that releases hormones, thus causing arousal. There is no mention in their abstract of how they discovered this, and access to how the study was conducted is blocked. Wait a minute — what the heck is pataphysics?

Pataphysics was invented by French writer Alfred Jarry to be the “science of imaginary solutions”

As Andrew Hugill says in his ‘Pataphysics: A Useless Guide, “To understand pataphysics is to fail to understand pataphysics.” Mixed in with his parody is this bit of advice: beware of pretentious nonsense. Big Think’s Jonny Thompson agrees, saying pataphysics is the belief that, even if you do manage to understand what people are trying to say, what they’re saying is probably bullshit anyway.

It’s easy to appear deeply profound if you hide behind breathlessly long and convoluted sentences

As Nobel Prize winners Albert Einstein and Richard Feynman both like to remind us, “If you cannot explain something in simple terms, you don’t understand it.”


Body mirroring is the name for the phenomenon where people imitate the actions of others, consciously or unconsciously. Many websites say you will be more successful if you make a habit of doing it. When this behavior is deliberately imitative, it is one of the tools of the master manipulator.

Social mirroring is when we see people yawn, laugh, and scratch, we do, too

Zhou-Feng Chen is the director of Washington University’s Center for the Study of Itch. His favorite video is the one of mice scratching themselves. When he shows this video to other mice, they start scratching themselves within seconds. According to an interview with PBS, Chen says when animals mimic the behavior of others, it is because they see that behavior as useful. In a world of biting insects, this makes excellent sense for furry little animals.


*Anecdotal evidence

Anecdotes are short stories with a point. Evidence is documentation that allows the drawing of conclusions. The term anecdotal evidence refers to conclusions based neither on fact nor on careful study.

We use anecdotal evidence when it supports what we believe. When the anecdotal information is against us, we dismiss it as hearsay. What we don’t say is that our anecdotal evidence is usually secondhand information, also called gossip, idle chitchat, and rumor.


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