Why Do We Yawn?

iStock/BraunS
iStock/BraunS

The short answer is that no one really knows.

The long answer is that no one really knows, but there are plenty of interesting theories:

1. The idea that we yawn to get rid of carbon dioxide and take in more oxygen has been disproved by research, but persists as the "common wisdom" answer. According to this theory, people breathe more slowly when they're bored or tired and less oxygen gets to the lungs. As CO2 builds up in the blood, the brain reflexively prompts a deep, oxygen-rich breath.

The problem with this theory is a 1987 study by Dr. Robert Provine, who is regarded as the world's foremost yawn expert. Provine set up an experiment in which volunteers breathed one of four gases that contained varying ratios of CO2 to O2 for 30 minutes. Normal air contains 20.95% oxygen and 0.03% carbon dioxide, but neither of the gases in the experiment with higher concentrations of CO2 (3% and 5%) caused the research subjects to yawn more.

2.

Last year, a team of researchers at the University of Albany proposed that the purpose of yawning is to cool the brain. They conducted an experiment similar to Provine's and again found that raising or lowering oxygen and carbon dioxide levels in the blood did not change the amount or length of yawns.

Subsequent experiments focused on two well-established brain cooling mechanisms: nasal breathing and forehead cooling. When you breathe through your nose, it cools the blood vessels in the nasal cavity and sends that cooler blood to the brain. Likewise, when you cool your forehead, the veins there, some of which are directly connected to the brain, deliver cooler blood. The researchers found that their test subjects with warm or room temperature towels pressed against their heads yawned more than those with cold towels. Subjects who breathed through their noses during the experiment did not yawn at all.

The researchers said their evidence suggests that taking in a big gulp of air with a yawn cools the brain and maintains mental efficiency.

3. Another theory says that yawning has more to do with sociology than physiology and also tackles the question of contagious yawning.

Almost all vertebrates yawn spontaneously, but only humans, chimps and macaques yawn as a result of watching another individual do it. Given that these are social creatures that live in groups, the contagious yawn may have evolved as a way to coordinate behavior and maintain group vigilance. When one individual yawned, the group took that as evidence that their brain temperature was up and their mental efficiency was down. If all members of the group then yawned, the overall level of vigilance in the group was enhanced. In humans, who have color-coded charts to signal how vigilant they should be, yawns may still be contagious as a vestigial response.

While yawns are still largely a mystery, here are some things we know for certain:

"¢ The average yawn lasts about six seconds.

"¢ In humans, the earliest occurrence of a yawn happens about 11 weeks after conception "“ while we're still in the womb.

"¢ Your heart rate can rise as much as 30% during a yawn.

"¢ 55% of people will yawn within five minutes of seeing someone else yawn.

"¢ Blind people yawn more after hearing an audio tape of people yawning.

"¢ Reading or even thinking about yawning can cause you to yawn.

"¢ While researching and writing this story, I yawned 37 times.

What’s the Difference Between Crocheting and Knitting?

djedzura/iStock via Getty Images
djedzura/iStock via Getty Images

With blustery days officially upon us, the most pressing question about your sweaters, scarves, hats, and mittens is probably: “Are these keeping me warm?” If you’re a DIY enthusiast, or just a detail-oriented person in general, your next question might be: “Were these knitted or crocheted?”

Knitting and crocheting are both calming crafts that involve yarn, produce cozy garments and other items, and can even boost your mental well-being. Having said that, they do have a few specific differences.

To knit, you need needles. The size, material, and number of those needles depends on the project; though most traditional garments are made using two needles, it’s also possible to knit with just one needle, or as many as five. But regardless of the other variables, one or both ends of your knitting needles will always be pointed.

While crocheting calls for a similar long, thin tool that varies in size and material, it has a hooked end—and you only ever need one. According to The Spruce Crafts, even if you hear people refer to the tool as a crochet needle, they’re really talking about a crochet hook.

crotchet hook and garment
jessicacasetorres/iStock via Getty Images

Part of the reason you only use one hook brings us to the next difference between crocheting and knitting: When crocheting, there’s only one “active loop” on your hook at any given time, whereas knitting entails lining up loops down the length of your needles and passing them between needles. The blog Darn Good Yarn explains that since each loop is attached to a long row of stitches, accidentally “dropping” one off the end of your needle might unravel the entire row.

Of course, you have a better chance of avoiding that type of manual error if you’re using a knitting machine or loom, which both exist. Crocheting, on the other hand, has to be done by hand. Since machines can create garments with extremely small stitches, some knit clothes can be much more lightweight or close-fitting than anything you’d be able to crochet—and knitted clothes can also be mass-produced.

When it comes to what the items actually look like, crochet stitches characteristically look more like knots, while knit stitches seem flatter and less bulky. However, materials and techniques have come a long way over the years, and now there’s more crossover between what you’re able to knit and crochet. According to The Spruce Crafts, socks and T-shirts—traditionally both garments that would be knitted—can now technically be crocheted.

knitting needles and garment
Sedan504/iStock via Getty Images

And, believe it or not, knitting and crocheting can even be used to depict complicated mathematical concepts: see what a crocheted hyperbolic plane, Lorenz manifold, and more look like here.

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

What Happens to Leftover Campaign Funds When a Candidate Drops Out?

After nearly one year of campaigning for the Democratic presidential nomination, Kamala Harris has officially bowed out of the 2020 election. She's not the only would-be president to call it quits so far. So what happens to all the leftover campaign funds when a candidate drops out?

One thing's for sure: Upset candidates can't console themselves by putting the dough toward a new yacht and sailing off to recuperate. The Federal Election Commission has strict rules about what federal candidates can and can't do with leftover campaign money, and the biggest directive is that they can't pocket it for personal use.

Here's what a campaign committee is allowed to do with any lingering cash: it can donate the funds to charities or political parties; it can contribute $2000 per election to other candidates; and it can save the money in case the candidate chooses to run again. However, those regulations don't apply to the relatively new super PACs (Political Action Committees); this is only the third election where they have played a role, and there are currently no rules to stipulate what happens to that money beyond that it cannot go to fund another federal candidate. Much of that money tends to be returned to its original donors, used to wrap up the failed campaign, or donated to back a state-level candidate. The goal, however, is always to spend all of that money.

Running a campaign is an expensive proposition—Barack Obama spent nearly $750 million on his 2008 White House bid, and in 2012 he spent $985 million on reelection while challenger Mitt Romney spent $992 million—and insufficient cash is often a reason campaigns go belly up.

As for winning (or sometimes losing) politicians, they'll often put their leftover funds toward their next race. If they choose not to run, they have to abide by the same FEC rules. Wonder why this law is in effect? Until 1993, U.S. Representatives who took office before January 8, 1980, were allowed to keep any leftover campaign cash when they retired, but a study showed that a third of Congress kept and spent millions in campaign donations on personal items like clothing, jewelry, artwork, personal travel, and dry cleaning. Embarrassed, Congress passed a law negating this custom for the House; the Senate already had provisions in place so this wouldn't happen.

In reality though, officials can usually find a way to make that cash still work for them (and state laws differ from federal ones). After Chris Christie won reelection as New Jersey's governor in 2014, his campaign was granted permission to use some of its remaining war chest to cover the legal fees Christie incurred during the Bridgegate scandal. And this was well before he dropped $26.7 million on his failed 2016 presidential bid.

An earlier version of this article originally ran in 2012.

SECTIONS

arrow
LIVE SMARTER