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Why Is Yawning Contagious?

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What is yawning? And why do we do so much of it? Neuroscientist and yawn expert Robert Provine says it's "ancient and autonomic." It stems from early evolution and is common to many creatures—even fish do it. It's autonomic in the sense that it roots in the brainstem, way down in the basement level of the brain, where certain responses are so built-in they don't even qualify as reflexes.

Yawning has many triggers, including boredom, sleepiness, and temperature. A 2014 study suggested that there's a "thermal window" (at around 68°F) for human yawning; as ambient temperature approaches body temperature or goes down near freezing, we yawn less. According to the paper, we may yawn to regulate the temperature of our brains. This isn't the same as saying we yawn to take in extra oxygen, as evidence to date says we don't. It means that yawning might act to draw brain-soothing ambient air in through the nose and mouth.

COPYCAT YAWNING?

Over the years, scientists have observed "contagious yawning" in chimpanzees, humans, baboons, bonobos, wolves, and, to a certain extent, dogs. Yawning feels good, so why not join in when someone else yawns? Well, you're not really "joining in," because you aren't copying the yawn on any conscious level. It happens because you just can't help it. If you become self-conscious about a yawn, it stops.

While many past studies have documented the phenomenon, a more recent study, published in the journal Adaptive Human Behavior and Physiology, contends that yawns may not be contagious after all—or at least that we have not yet proven it. Experimental psychologist Rohan Kapitány of the University of Oxford conducted a review of the scientific literature on contagious yawns and found very little conclusive evidence to back up our long-held assumption that yawns are contagious.

"The belief that yawns are contagious seems self-evident," Kapitány told PsyPost, "but there are some very basic reasons for why we might be mistaken in this. If we fail to dissect that which we think we know, we might end up with conclusions that do not reflect reality. In this instance, the literature hasn't questioned the basic features of contagious yawning, and ended up with a wide range of unstandardized methodologies and conclusions."

Still, because Kapitány's study was small and extremely limited, he and his fellow authors urge other scientists to challenge their findings with experiments of their own.

"I may be wrong!" Kapitány said. "Maybe yawns are contagious!" Kapitány says he'd like to see "more robust" attempts to falsify the claim that yawns are contagious rather than "simply demonstrating it over and over [in] slightly different contexts with richer and richer explanations."

WHO DOESN'T CATCH YAWNS?

Some people with autism or schizophrenia don't exhibit a yawn-contagion response. The same is true of children under the age of four years. This has led to a variety of theories about yawning's relationship to empathy and the brain's mirror-neuron system (MNS). The idea here is that MNS deficits might lead to missing hidden empathetic cues that trigger contagious yawning. The MNS seems to be involved in the process to some extent. fMRI scans on a range of people have shown that other parts of the brain also "light up" in response to images of yawning, perhaps more so than the areas normally associated with empathy.

YAWN AND RUN

Parts of the amygdala—a brain area associated with fear and heightened attention—light up in response to images of yawning. We sometimes yawn when we're nervous, such as before a sporting performance.

So, perhaps we yawn at those times to prepare our brains for "fight or flight." Maybe contagious yawning is a smart evolutionary shortcut for readying the brains of an entire group of hominins for swift action in response to a threat. (If that's the case, then some older members would have been left behind, because older people are a little less susceptible to yawn contagion.) We are social mammals; this kind of evolutionary refinement of an existing trait (general purpose yawning becoming contagious yawning) might have helped groups to survive.

Or maybe it's a lot less deep than that. Laughing also feels good, and it too can be contagious. Like laughter, contagious yawning might help groups to bond—by signaling unselfconscious, relaxed sleepiness. Perhaps it has more to do with feeling safe than with feeling threatened.

STRAGGLERS AND FAKES

Contagious yawning is still a bit of a scientific mystery. We love to speculate about it and try to home in on the reason for it. But why should an evolutionary trait have one specific reason behind it? Often, traits survive because they cover a number of bases. Other times, they're simply evolutionary stragglers whose original purpose has faded out, but because they don't work against a creature's survival, there's no pressure to get rid of them.

One modern adaptation of yawning is not so contagious—fake yawning. You might do this as a less-than-subtle means of signaling that a conversation has dragged on too long. Why not engage in a scientific experiment next time you're in a meeting with your boss? Lean back in your chair and yawn, then note down whether he or she yawns right back at you. Maybe there's a scientific discovery in there … but probably no pay raise.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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What's the Difference Between Stuffing and Dressing?
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For carbohydrate consumers, nothing completes a Thanksgiving meal like stuffing—shovelfuls of bread, celery, mushrooms, and other ingredients that complement all of that turkey protein.

Some people don’t say “stuffing,” though. They say “dressing.” In these calamitous times, knowing how to properly refer to the giant glob of insulin-spiking bread seems necessary. So what's the difference?

Let’s dismiss one theory off the bat: Dressing and stuffing do not correlate with how the side dish is prepared. A turkey can be stuffed with dressing, and stuffing can be served in a casserole dish. Whether it’s ever seen the inside of a bird is irrelevant, and anyone who tells you otherwise is wrong and should be met with suspicion, if not outright derision.

The terms are actually separated due to regional dialects. “Dressing” seems to be the favored descriptor for southern states like Mississippi, Tennessee, South Carolina, and Georgia, while “stuffing” is preferred by Maine, New York, and other northern areas. (Some parts of Pennsylvania call it "filling," which is a bit too on the nose, but to each their own.)

If “stuffing” stemmed from the common practice of filling a turkey with carbs, why the division? According to The Huffington Post, it may have been because Southerners considered the word “stuffing” impolite, so never embraced it.

While you should experience no material difference in asking for stuffing or dressing, when visiting relatives it might be helpful to keep to their regionally-preferred word to avoid confusion. Enjoy stuffing yourselves.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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Why Do the Lions and Cowboys Always Play on Thanksgiving?
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Because it's tradition! But how did this tradition begin?

Every year since 1934, the Detroit Lions have taken the field for a Thanksgiving game, no matter how bad their record has been. It all goes back to when the Lions were still a fairly young franchise. The team started in 1929 in Portsmouth, Ohio, as the Spartans. Portsmouth, while surely a lovely town, wasn't quite big enough to support a pro team in the young NFL. Detroit radio station owner George A. Richards bought the Spartans and moved the team to Detroit in 1934.

Although Richards's new squad was a solid team, they were playing second fiddle in Detroit to the Hank Greenberg-led Tigers, who had gone 101-53 to win the 1934 American League Pennant. In the early weeks of the 1934 season, the biggest crowd the Lions could draw for a game was a relatively paltry 15,000. Desperate for a marketing trick to get Detroit excited about its fledgling football franchise, Richards hit on the idea of playing a game on Thanksgiving. Since Richards's WJR was one of the bigger radio stations in the country, he had considerable clout with his network and convinced NBC to broadcast a Thanksgiving game on 94 stations nationwide.

The move worked brilliantly. The undefeated Chicago Bears rolled into town as defending NFL champions, and since the Lions had only one loss, the winner of the first Thanksgiving game would take the NFL's Western Division. The Lions not only sold out their 26,000-seat stadium, they also had to turn fans away at the gate. Even though the juggernaut Bears won that game, the tradition took hold, and the Lions have been playing on Thanksgiving ever since.

This year, the Lions host the Minnesota Vikings.

HOW 'BOUT THEM COWBOYS?


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The Cowboys, too, jumped on the opportunity to play on Thanksgiving as an extra little bump for their popularity. When the chance to take the field on Thanksgiving arose in 1966, it might not have been a huge benefit for the Cowboys. Sure, the Lions had filled their stadium for their Thanksgiving games, but that was no assurance that Texans would warm to holiday football so quickly.

Cowboys general manager Tex Schramm, though, was something of a marketing genius; among his other achievements was the creation of the Dallas Cowboys Cheerleaders.

Schramm saw the Thanksgiving Day game as a great way to get the team some national publicity even as it struggled under young head coach Tom Landry. Schramm signed the Cowboys up for the game even though the NFL was worried that the fans might just not show up—the league guaranteed the team a certain gate revenue in case nobody bought tickets. But the fans showed up in droves, and the team broke its attendance record as 80,259 crammed into the Cotton Bowl. The Cowboys beat the Cleveland Browns 26-14 that day, and a second Thanksgiving pigskin tradition caught hold. Since 1966, the Cowboys have missed having Thanksgiving games only twice.

Dallas will take on the Los Angeles Chargers on Thursday.

WHAT'S WITH THE NIGHT GAME?


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In 2006, because 6-plus hours of holiday football was not sufficient, the NFL added a third game to the Thanksgiving lineup. This game is not assigned to a specific franchise—this year, the Washington Redskins will welcome the New York Giants.

Re-running this 2008 article a few days before the games is our Thanksgiving tradition.

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