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Scientists Say We Can Smell Happiness

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The old saying goes that happiness is contagious. New research suggests there might actually be some science to back that up. Happiness, scientists say, has a distinct smell that humans can sense on one another. And when we get a good whiff of someone else's joy, we get happier too. 

The key lies in our sweat. According to psychological scientist Gün Semin of Utrecht University in the Netherlands, senior research on the study, "[B]eing exposed to sweat produced under happiness induces a simulacrum of happiness in receivers, and induces a contagion of the emotional state." 

He and his team collected sweat samples from a group of 12 men as they watched videos meant to induce different emotions, like happiness and fear. The sweat samples were then passed along to a group of female test subjects for sniffing.

The researchers wanted to know how the different sweat samples made women feel. To measure this, they watched for changes in facial expression that might indicate an emotional response. When women were exposed to “happy sweat,” their faces displayed classic microexpressions associated with pleasure: the muscles around their eyes activated as if they were about to flash a genuine, happiness-induced grin. This is called the “Duchenne smile,” and it’s a giveaway sign of true joy. The man who discovered it, French anatomist Guillaume-Benjamin-Amand Duchenne de Boulogne, once said, "The muscle around the eye ... is only brought into play by a true feeling, an agreeable emotion. Its inertia in smiling unmasks a false friend."

We already knew that chemicals in our sweat can convey fear. When we “smell” fear on someone else, the stress centers in our brains are activated and we become more alert, ready to defend ourselves from a threat. That's evolutionarily useful.

Pamela Dalton, an olfactory scientist at the Monell Chemical Senses Center in Philadelphia, says the communication of danger-induced fear is so important that she "would expect the ability to communicate a happy emotion to [actually] be less potent than the ability to transmit a negative emotion." But that may not be the case.

The findings could have big implications for how we treat depression or mood disorders. “If we can actually extract the biochemical combination that is induced by happiness, then you can have products that are ‘laced’ with this biochemical and will make people feel more positive,” Semin says

More research is needed before we can put happy spray in a can. “Researchers would have to parse out its unique chemical cocktail from among the 180 to 200 known chemicals that make up human body odor,” writes Rachel E. Gross at Slate. “That’d be like determining Coca-Cola’s proprietary formula from scratch.” Also, the study only looked at how sweat influences women. The researchers claim this is because “women generally have both a better sense of smell and a greater sensitivity to emotional signals than men do.” But we’d need to know if the effect exists for men, as well. 

Finally, while this study is fascinating, it should be taken with a big grain of salt until the findings can be replicated. Why? It was funded in part by Unilever, which sells—you guessed it—Axe body spray. 

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The Surprising Reason Why Pen Caps Have Tiny Holes at the Top
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If you’re an avid pen chewer, or even just a diehard fan of writing by hand, you’re probably well acquainted with the small hole that tops off most ballpoint pen caps, particularly those classic Bic Cristal pens. The reason it’s there has nothing to do with pen function, it turns out. As Science Alert recently reported, it’s actually designed to counter human carelessness.

Though it’s arguably unwise—not to mention unhygienic—to chomp or suck on a plastic pen cap all day, plenty of people do it, especially kids. And inevitably, that means some people end up swallowing their pen caps. Companies like Bic know this well—so they make pen caps that won’t impede breathing if they’re accidentally swallowed.

This isn’t only a Bic requirement, though the company’s Cristal pens do have particularly obvious holes. The International Organization for Standardization, a federation that sets industrial standards for 161 countries, requires it. ISO 11540 specifies that if pens must have caps, they should be designed to reduce the risk of asphyxiation if they’re swallowed.

It applies to writing instruments “which in normal or foreseeable circumstances are likely to be used by children up to the age of 14 years.” Fancy fountain pens and other writing instruments that are clearly designed for adult use don’t need to have holes in them, nor do caps that are large enough that you can’t swallow them. Any pen that could conceivably make its way into the hands of a child needs to have an air hole in the cap that provides a minimum flow of 8 liters (about 2 gallons) of air per minute, according to the standard [PDF].

Pen cap inhalation is a real danger, albeit a rare one, especially for primary school kids. A 2012 study [PDF] reported that pen caps account for somewhere between 3 and 8 percent of “foreign body aspiration,” the official term for inhaling something you’re not supposed to. Another study found that of 1280 kids (ages 6 to 14) treated between 1997 and 2007 for foreign body inhalation in Beijing, 34 had inhaled pen caps.

But the standards help keep kids alive. In that Beijing study, none of the 34 kids died, and the caps were successfully removed by doctors. That wasn’t always the case. In the UK, nine children asphyxiated due to swallowing pen caps between 1970 and 1984. After the UK adopted the international standard for air holes in pen caps, the number of deaths dropped precipitously [PDF]. Unfortunately, it’s not foolproof; in 2007, a 13-year-old in the UK died after accidentally swallowing his pen cap.

Even if you can still breathe through that little air hole, getting a smooth plastic pen cap out of your throat is no easy task for doctors. The graspers they normally use to take foreign bodies out of airways don’t always work, as that 2012 case report found, and hospitals sometimes have to employ different tools to get the stubbornly slippery caps out (in that study, they used a catheter that could work through the hole in the cap, then inflated a small balloon at the end of the catheter to pull the cap out). The procedure doesn’t exactly sound pleasant. So maybe resist the urge to put your pen cap in your mouth.

[h/t Science Alert]

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Big Questions
What Causes Sinkholes?
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Mark Ralston/AFP/Getty Images

This week, a sinkhole opened up on the White House lawn—likely the result of excess rainfall on the "legitimate swamp" surrounding the storied building, a geologist told The New York Times. While the event had some suggesting we call for Buffy's help, sinkholes are pretty common. In the past few days alone, cavernous maws in the earth have appeared in Maryland, North Carolina, Tennessee, and of course Florida, home to more sinkholes than any other state.

Sinkholes have gulped down suburban homes, cars, and entire fields in the past. How does the ground just open up like that?

Sinkholes are a simple matter of cause and effect. Urban sinkholes may be directly traced to underground water main breaks or collapsed sewer pipelines, into which city sidewalks crumple in the absence of any structural support. In more rural areas, such catastrophes might be attributed to abandoned mine shafts or salt caverns that can't take the weight anymore. These types of sinkholes are heavily influenced by human action, but most sinkholes are unpredictable, inevitable natural occurrences.

Florida is so prone to sinkholes because it has the misfortune of being built upon a foundation of limestone—solid rock, but the kind that is easily dissolved by acidic rain or groundwater. The karst process, in which the mildly acidic water wears away at fractures in the limestone, leaves empty space where there used to be stone, and even the residue is washed away. Any loose soil, grass, or—for example—luxury condominiums perched atop the hole in the ground aren't left with much support. Just as a house built on a weak foundation is more likely to collapse, the same is true of the ground itself. Gravity eventually takes its toll, aided by natural erosion, and so the hole begins to sink.

About 10 percent of the world's landscape is composed of karst regions. Despite being common, sinkholes' unforeseeable nature serves as proof that the ground beneath our feet may not be as solid as we think.

A version of this story originally ran in 2014.

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