BYDK* – Chronic yawning may mean you are the smartest person in the room

Yawns are known to be contagious and often occur at inopportune times. But, have you ever stopped to consider why humans and countless other mammals yawn so frequently? What purpose does it serve?


For a long time, the most widely believed theory was that yawning helps oxygenate our blood. Now, however, new research from Utrecht University reports yawning actually serves to cool the brain.

“According to study co-author Andrew Gallup, from the State University of New York Polytechnic Institute, yawning works as the mind’s AC system “through the simultaneous inhalation of cool air and the stretching of the muscles surrounding the oral cavities, yawning increases the flow of cooler blood to the brain, and thus has a thermoregulatory function.”

“Tons of recorded observations support this theory. Brain temperature always drops post-yawn, and ambient brain temperature can be used to accurately predict when the next yawn is coming. Moreover, when people hold an ice pack or cold beverage to their head or neck, they rarely yawn.

So, with all this under consideration, researchers theorized that the larger the brain, the more cooling down it needs. In other words, a big brain means a long yawn. To investigate, a total of 1,250 yawns emitted by 55 mammal species and 46 bird species were analyzed. Additional videos of animals yawning on the internet were also considered.


“In this new study, we wanted to see how universal that theory is, and especially whether it holds true for birds,” comments behavioral biologist and study co-author Jorg Massen. “We went to several zoos with a camera and waited by the animal enclosures for the animals to yawn. That was a pretty long haul.”

“Getting video footage of so many yawning animals requires quite some patience, and the subsequent coding of all these yawns has made me immune to the contagiousness of yawning,” explains co-lead author Margarita Hartlieb of the University of Vienna.

Next, the duration of all those yawns was compared and linked to brain and neuronal data. Ultimately, that process led researchers to conclude that regardless of body size, yawning duration increases “with the size and number of neurons in the brain of a given species.”

Mammals (including humans) also tend to yawn longer than birds, but that can be explained by differences in body temperature. Birds have a higher core temperature, which means it takes less air (yawning) to cool down.

In summation, it seems mammals and birds both evolved over time to yawn as a way to keep our minds in top shape. The brain doesn’t work well when it’s overheating.

On a lighter note, this study certainly flips the script on the typical narrative surrounding yawning. Yawning is often seen as rude or inconsiderate like we’re deliberately trying to let everyone know we’re bored, but maybe in reality the opposite holds true. The next time a friend laments your multiple yawns during a story, remind him or her that your brain was just trying to stay alert and functioning.

“We should maybe stop considering yawning as rude, and instead appreciate that the individual is trying to stay attentive,” Mullen concludes.

*Bet You Didn’t Know!

The full study can be found here, published in Communications Biology.


Don’t Yawn at This Post

Bears do it; bats do it. So do guinea pigs, dogs and humans. They all yawn. It’s a common animal behavior, but one that is something of a mystery.

Humans can yawn from:

  • Boredom
  • sleepiness
  • hunger
  • anxiety
  • stress

All these trigger changes in brain chemistry, which can trigger a spontaneous yawn. But it’s not clear what the yawn accomplishes. One possibility is the yawn perks you up by increasing heart rate, blood pressure and respiratory function.

When violinists get ready to go on stage to play a concerto, they often yawn, says Provine. So do Olympians right before a competition, or paratroopers getting ready to do their first jump. One study found that yawning has a similar impact on the brain as a dose of caffeine.

Not all yawn researchers agree with this theory.

Researchers** reviewed several theories of yawning and concluded that the arousal theory lacks evidence. What they did find were several studies that show yawning is highly contagious among humans, suggesting that “yawns might have a social and communicative function,” 

“Looking at yawns, hearing yawns, thinking about yawns or talking about yawns will likely trigger a contagious response. Contagious yawning may have evolved in early humans to boost social bonding, according to Robert Provine, professor of psychology and neuroscience at the University of Maryland, Baltimore County. A good group yawn could serve to perk everyone up to be more vigilant about danger, he says.”

“Another piece of evidence backing up the social bonding theory of yawning is a 2011 study by Ivan Norsicia and Elisabetta Palagi that found people are more likely to copy a yawn if they know the person who is yawning. A stranger’s yawn is less likely to trigger a contagious response. And while babies yawn spontaneously, children don’t engage in contagious yawning until about age 4 — around the same time they’re becoming more socially connected.”

What about other animals? All vertebrates, critters with backbones, yawn spontaneously. But very few yawn contagiously.

“Until the last few years, the feeling was that contagious yawning was unique to humans,” Provine says.

“. . . two more species have been added to the list of contagious yawners: dogs and chimpanzees. When two groups of chimpanzees were shown videos of familiar and unfamiliar chimps yawning, the group watching the chimps they knew engaged in more contagious yawning. This study, by Matthew Campbell and Frans de Waal, supports the theory that yawning plays a role in the evolution of social bonding and empathy.”

“And dogs not only catch each others’ yawns, they are susceptible to human yawning as well. In one study, 29 dogs watched a human yawning and 21 of them yawned as well — suggesting that interspecies yawning could help in dog-human communication.”

*Robert Provine, professor of psychology and neuroscience at the University of Maryland, Baltimore County. Provine has studied what he calls “yawn science” since the early 1980s, and he’s published dozens of research articles on it. “There’s still no consensus on the purpose of a yawn” he says, “the simple yawn is not so simple”.

DID YOU YAWN just reading about yawning?

** Adrian Guggisberg, a professor in the department of clinical neurosciences at the University of Geneva.