Why Do We Laugh?

iStock/Chloe Effron
iStock/Chloe Effron

WHY? is our attempt to answer all the questions every little kid asks. Do you have a question? Send it to why@mentalfloss.com.

People laugh for a lot of different reasons. We laugh when something is funny, like a joke. We laugh when something surprises us, like someone slipping on a banana peel and falling on their butt. We laugh when someone tickles us. We sometimes even laugh when we're nervous or scared! Scientists don’t yet know all the reasons why so many different things cause us to laugh. But we do know laughter helps us to get along with each other.

In some ways, laughing is a way of talking. The ancestors of humans were laughing long before they had language. Before words, laughter could let others know: “Everything is OK!” Today, we still laugh as a way to let other people know that we like them, that we’re friendly, and that we’re part of a group. In fact, did you know that you can “catch” laughter from another person? Yep, even the sound of another person’s laugh can make someone start laughing. That’s a good thing, because laughter is healthy for us!

Laughter causes the release of special chemicals in your brain that help you relax and feel good. Laughing is exercise: It makes you breathe deeply, use your muscles, and get your heart and lungs going. All of this can calm you down if you’re feeling worried or scared. Scientists think laughing may also help boost your immune (ih-MYOON) system (which helps your body to fight off sickness), ease pain when you are hurt, and put you in a good mood.

Watch as one woman’s laughter spreads through a train car until everyone is laughing. Try not to giggle yourself—it’s hard!

How Did 6 Feet Become the Standard Grave Depth?

iStock
iStock

It all started with the plague: The origins of “six feet under” come from a 1665 outbreak in England. As the disease swept the country, the mayor of London literally laid down the law about how to deal with the bodies to avoid further infections. Among his specifications—made in “Orders Conceived and Published by the Lord Mayor and Aldermen of the City of London, Concerning the Infection of the Plague”—was that “all the graves shall be at least six feet deep.”

The law eventually fell out of favor both in England and its colonies. Modern American burial laws vary from state to state, though many states simply require a minimum of 18 inches of soil on top of the casket or burial vault (or two feet of soil if the body is not enclosed in anything). Given an 18-inch dirt buffer and the height of the average casket (which appears to be approximately 30 inches), a grave as shallow as four feet would be fine.

A typical modern burial involves a body pumped full of chemical preservatives sealed inside a sturdy metal casket, which is itself sealed inside a steel or cement burial vault. It’s less of a hospitable environment for microbes than the grave used to be. For untypical burials, though—where the body isn’t embalmed, a vault isn’t used, or the casket is wood instead of metal or is foregone entirely—even these less strict burial standards provide a measure of safety and comfort. Without any protection, and subjected to a few years of soil erosion, the bones of the dearly departed could inconveniently and unexpectedly surface or get too close to the living, scaring people and acting as disease vectors. The minimum depth helps keep the dead down where they belong.

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

This article originally appeared in 2012.

One Good Reason Not to Hold in a Fart: It Could Leak Out of Your Mouth

iStock/grinvalds
iStock/grinvalds

The next time you hold in a fart for fear of being heard by polite company, just remember this: It could leak out of your mouth instead of your butt. Writing on The Conversation, University of Newcastle nutrition and dietetics professor Clare Collins explains that pent-up gas can pass through your gut wall and get reabsorbed into your circulation. It's then released when you exhale, whether you like it or not.

“Holding on too long means the build up of intestinal gas will eventually escape via an uncontrollable fart,” Collins writes. In this case, the fart comes out of the wrong end. Talk about potty mouth.

A few brave scientists have investigated the phenomenon of flatulence. In one study, 10 healthy volunteers were fed half a can of baked beans in addition to their regular diets and given a rectal catheter to measure their farts over a 24-hour period. Although it was a small sample, the results were still telling. Men and women let loose the same amount of gas, and the average number of “flatus episodes” (a single fart, or series of farts) during that period was eight. Another study of 10 people found that high-fiber diets led to fewer but bigger farts, and a third study found that gases containing sulphur are the culprit of the world’s stinkiest farts. Two judges were tapped to rate the odor intensity of each toot, and we can only hope that they made it out alive.

Scientific literature also seems to support Collins’s advice to “let it go.” A 2010 paper on “Methane and the gastrointestinal tract” says methane, hydrogen sulfide, and other gases that are produced in the intestinal tract are mostly eliminated from the body via the anus or “expelled from the lungs.” Holding it in can lead to belching, flatulence, bloating, and pain. And in some severe cases, pouches can form along the wall of the colon and get infected, causing diverticulitis.

So go ahead and let it rip, just like nature intended—but maybe try to find an empty room first.

[h/t CBS Philadelphia]

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