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 Is Figgy Pudding Anyway?

bhofack2/iStock via Getty Images
bhofack2/iStock via Getty Images

"We Wish You a Merry Christmas" is an ode to figgy pudding disguised as a straightforward Christmas song. Three out of four verses in some versions are dedicated to the dish. So after listening to enough holiday music this December, you may start to wonder: What is figgy pudding anyway? And is it really so good that you'd actually beg for it on a stranger's doorstep through song?

According to NPR, figgy pudding, also called plum pudding, isn't pudding—at least not the kind of pudding many Americans think of when they hear the word—and it contains neither figs nor plums. In the UK, pudding is used as catch-all to describe any sweet dish served after a meal. Figgy pudding isn't creamy or custardy, but it is a sugary cake, which qualifies it as pudding overseas.

In its most basic form, figgy pudding is a steamed, often domed-shaped cake made with alcohol and dried fruit. The first version of figgy pudding surfaced in 14th-century Britain. Back then, it was a stew-like, savory dish containing beef and mutton as well as fruit and wine. In the 15th century, this mixture was stuffed into animal casings to make sausages that would last through the winter.

By the end of the 16th century, figgy pudding had transitioned to a fully sweet dish—right around the same time when carolers started singing "Now bring us some figgy pudding" to their wealthy neighbors around Christmas. Today, the dessert is commonly filled with currants, raisins, and soaked in rum or brandy.

So where did the first half of its name come from? In pre-Victorian England, the word plum was applied to any type of dried fruit, including raisins, so plum pudding caught on. Figs occasionally appeared in recipes throughout the dish's history, though they're not considered a traditional ingredient.

If you're thinking about cooking a throwback feast this Christmas, don't stop at figgy pudding. From oyster stew to mincemeat pie, here are some more classic British dishes that have ties to the holiday.

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 Exactly is Christmas Tree Flocking?

iStock.com/Spiderstock
iStock.com/Spiderstock

Of the many curious holiday traditions (figgy pudding? wassailing?), one of the oddest has to be spraying down small trees with a mixture of adhesive and cellulose fibers to satisfy our longing for a white Christmas.

That’s what’s happening when you adorn a tree with artificial snow, otherwise known as flocking. And yet, when decorated and lit up, there’s something beautiful and warmly nostalgic about a well-flocked Christmas tree. Here’s how professionals manufacture this Christmas miracle.  

The History of Flocking

We’ve been trying to get that snowy look on Christmas trees for longer than you might think, dating back to the 1800s using substances like flour or cotton. A 1929 issue of Popular Mechanics recommended varnish, corn starch, and flakes of the silicate mineral mica. 

But tree flocking as we know it really caught on in the late 1950s and 1960s, along with aluminum trees and other glitzy (if not natural-looking) decor of the post-war boom. General Mills marketed Sno-Flok home kits, to be applied using a gun that attached to a vacuum cleaner.

Such home kits are not so popular these days, says Tom Leonard, owner of Peak Seasons, one of the country's largest manufacturers of Christmas tree lots supplies and tree flock. Flocking itself, however, has retained a level of appeal. “Sunbelt states use a lot of it because there’s no snow there,” Leonard tells Mental Floss. “It’s tremendously popular. The West Coast, the South, and the Southeast, the vast majority of it is sold in those zones.”

The Science of Flocking

So what exactly is flocking? At its core, flocking means attaching tiny fibers to a surface to create texture (the process is also used in fashion, home decor, and crafts). The Peak Seasons recipe includes paper pulp as fiber, corn starch as adhesive, and boron as a flame retardant—there’s a safety benefit to flocking.

And the company makes a lot of it. Leonard says they're the largest manufacturer of flock in the United States and Europe. “I don’t want to share [how much], but we sell lots of flock. I mean truckloads and truckloads.”

Based in sunny Riverside, California, Peak Seasons starts with paper and a grinder. “It’s like a big roll of toilet paper and it weighs a ton and you feed it into a machine and it comes out a powder,” Leonard says. The exception is certain bright colors—flock comes in white, black, pink, ice blue, royal blue, red, green, gold, and purple—which require cotton fibers instead of paper to hold the dye. The final product is almost like baby powder, shipped all over the country in large, cement-bag-sized bags.

From there you need to affix the stuff in a nice even coat, which is where flock machines like the Mighty Sno-Blower come in. They’re basically big tanks that hold varying amounts of flock depending on the model, plus a mechanism at the bottom to fluff up the powder. The machine then pumps the powder through a hose, and a gun at the end mixes it with a mist of water.

And that’s how flock is born.

The Art of Flocking

You don’t have to go with a professional flocker, or even use manufactured flock. There are all sorts of DIY recipes that include things like soap flakes or even desiccated coconut flakes. But if you do go pro, you want to be in the hands of someone like Paul Iantosca, who has been flocking trees in the Boston area for 20 years.

Flocking one tree in bright purple (white is still most popular), Iantosca first sprays it down with water. Then, in an area closed off with plastic sheeting, he fires up the blower and blasts the tree evenly with what looks like a purple fog. The stuff gets everywhere. He wears a mask to keep it out of his nose, but some high-volume flockers wear full protective coveralls. 

The tricky part to flocking is that you can’t tell if you got it right until it dries. When it goes on, it’s cold and wet like paste. But as it dries, the Christmas magic kicks in and it puffs up, turning into fluffy white (or, in this case, purple) fuzz firmly affixed to the needles.

There are, of course, pitfalls. Not enough water, and the flocking falls off and makes a huge mess. A flocked tree can’t get wet a second time. “It won’t dry again. It’s disgusting actually,” Iantosca says. Also, when you flock a tree, the color highlights its flaws. A janky tree turns into a weird, uneven shrub.

But if you get it right and string it up with lights, you’ve got a real stunner on your hands. Iantosca’s had flocked trees for his own home for the past 10 years and his kids won’t let him go back.

“When you plug that thing in, it absolutely glows inside," he says. "It’s unbelievable.”

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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