Why We Yawn

Okay, let’s start by apologizing: the subject of this article probably made you yawn. According to a study cited by the New Yorker, “eighty-eight percent of people who were instructed to think of yawns yawned themselves within thirty minutes.” So, sorry about that. If it’s any consolation, imagine how difficult it was to write this — I’m squarely one of the 88%.

And if you think about it — about how yawning is contagious, I mean — that’s a bit weird. We typically associate yawning with being tired, but right now, you’re not necessarily tired at all. So: why do we yawn when we see someone yawn, talk about yawning, read about yawning, and even think about yawning?

The short answer is we don’t know. According to University of Maryland Professor Robert R. Provine, who is probably the leading researcher on the subject (via that New Yorker article), “yawning may have the dubious distinction of being the least understood, common human behavior.” That said, there are a few theories, none of which we can reliably state, yet, as the reason. And one the most promising one is that our it helps us cool down our brains.

That’s was the theory being tested by Melanie Shoup-Knox, a researcher at Princeton University in 2011. WebMD outlined his team’s thinking:

• When you start to yawn, powerful stretching of the jaw increases blood flow in the neck, face, and head.
• The deep intake of breath during a yawn forces downward flow of spinal fluid and blood from the brain.
• Cool air breathed into the mouth cools these fluids.

Shoup-Knox’s team performed a few tests in furtherance of the theory. First, they surmised that, because cool air is important to the equation, you’re more likely to yawn when it’s cooler outside than if it’s warmer. Again per WebMD, Shoup-Knox ran an experiment in Arizona — once in the winter, with temperatures of around 71°F, and again in the summer, with temperatures in excess of 95°F. In both cases, eighty test subjects were shown images of other people yawning. The results: “in the cooler weather 45% of people yawned when they looked at the pictures. But in hotter weather, only 24% of people yawned. Moreover, people yawned more if they’d been outside longer in the cool weather, and yawned less if they’d been outside longer in the hot weather.”

Second, Shoup-Knox tried to chill some test subject’s brains externally. Per Smithsonian, his team showed videos of people yawning to those in the test while the subjects were also asked to hold hot or cold packs on their heads. Again, temperature made a difference: “When participants held a warm pack to their forehead, they yawned 41 percent of the time. When they held a cold pack, the incidence of yawning dropped to 9 percent.”

Again, the science here is hardly well-established — there are many questions and concerns about the data which have prevented the scientific community form reaching a consensus. And there are many other theories as well. But one thing is for sure, as Shoup-Knox’s co-author, Andrew Gallup points out: we often can’t control the need to yawn, and it isn’t always (or even most often) triggered by boredom. Therefore, he concludes, “it happens in a meeting, it should not be a sign of disrespect or insult.” (Rather, maybe the opposite is true — maybe it means we’re thinking so hard, we need to cool our brains down?)

Bonus fact: Ever wake up in the morning and both yawn and stretch simultaneously? That act has a name — it’s called pandiculation. It comes from Latin; it’s stem means “to stretch oneself.”

From the Archives: One Small Step for Man, One Giant Yawn for Mankind: How we got bored of Neil Armstrong. (Temporarily.)

Related: “The Going-to-Bed Book” by Sandra Boynton. A must-have for a parent of a young kid.