Why Do We Bite Our Nails?

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iStock

It can happen anywhere. Maybe you're waiting in the lobby of your doctor's office or studying at home for a big test—and then, without you even registering it, your fingertips are in your mouth and your teeth are gnawing away.

Even the people who do it tend to see nail biting as a nasty habit, but that doesn't make it any less prevalent. Twenty to 30 percent of people admit to biting their nails on a regular basis. Though reasons for the behavior vary, research has shown that most people do it because they need a psychological crutch, and not because they like having dirty, ragged fingernails.

According to Kieron O'Connor, a researcher at the University Institute of Mental Health at Montreal, there’s no one mood associated with nail biting. “People think you only bite when you’re stressed, but it’s not so simple,” O'Connor tells Mental Floss. “People will also bite when they’re bored and alone.” Nail biting feels good (in moderation at least), so when some people have nothing to do, or want to avoid the task in front of them, they bring their nails to their mouth out of habit. This same thing happens when nail biters feel overwhelmed by a stressful situation, or when they’re ruminating over some past behavior they feel embarrassed about. In all cases, nail biting is used as a mood regulator: a tool that distracts them or provides temporary relief or stimulation whenever an unwanted feeling comes up.

A study co-authored by O’Connor found that nail biting is more common in perfectionists. After speaking with 48 subjects, half with habit disorders like nail biting and half without, they found that the nail biters tended to be organizational perfectionists, or people who tend to over-plan, work too much, and become restless when they don’t have enough to do. “When people are perfectionists, they get bored and frustrated very easily and hold themselves to higher standards,” O’Connor says. “They plan too much, and when they can’t do all of it they have a sense of failure.”

So what is it about nail biting specifically that makes some people turn to the behavior when they’re feeling less than fantastic? Like many of our worst habits, nail biting is an evolutionary adaptation kicked into overdrive. Even before we had access to aisles worth of beauty products, humans practiced self-grooming, which includes getting rid of the occasional hangnails. But even nail biters with short, clean nails will engage in the behavior: They use it as a way to get the mental reward our brains associate with grooming without any of the cosmetic benefits.

Nail biting manifests itself at different levels of intensity. At one extreme there’s onychophagia, a condition where compulsive nail biting requires medical attention. Like skin picking and hair pulling, nail biting can be a symptom of a body-focused habit disorder. When it gets to the point that someone is harming themselves by chewing their nails so often, they usually require a mental health professional to help them curtail the behavior.

But for far more people, nail biting is just an annoying habit that’s hard for them to quit—no matter how much the squeamish people around them wish they would.

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What's the Difference Between Mold and Mildew?

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iStock.com/AndreasReh

We’re all familiar with colorful spots of something growing in our showers and in other dark, damp areas in our homes, but you may not know what to call it. Is it mold, or is it mildew? What is the difference between the two, anyway?

Both terms refer to fungus, but as it happens, it’s a squares-versus-rectangles situation. Mildew is a type of mold. The term typically describes fungi that grows flat, on surfaces like the walls of your shower or window sills. There are also several types of mildew that are specific to plants—powdery mildew and downy mildew are parasites that grow on certain trees, flowers, and crops, for example. While mold might be a colorful green or black, mildew is typically white.

The word mildew originally came from honeydew, a term for sticky secretions aphids and other insects leave on plants, which people used to think came from the sky, like dew. Eventually, the word came to refer to the mold caused by the fungi that fed on these secretions.

Leaves covered in white powder
Powdery mildew on maple leaves
iStock.com/kazakovmaksim

Most of the household growths we refer to as mold belong to just a few families of fungi species. According to the CDC, the most common indoor molds are Cladosporium, Penicillium, Aspergillus, and Alternaria. Household molds can be a variety of colors, from orange-brown to green to gray to black. (Note that not all mold that is black in color is the more toxic species we call “black mold,” or Stachybotrys.) In contrast to the powdery texture of mildew, molds are typically fuzzy or slimy.

In nature, mold can play an important role in the ecosystem, breaking down dead plants and leaves. In your house, those decomposition abilities aren’t quite so welcome. Mold spores fly through the air, and when they land in moist places, they start to grow—whether that’s on food, your ceiling, paper products, wood, carpet, leather, or elsewhere around your house—and in the process, destroy whatever they're growing on. Unlike mildew, most molds grow down into the surface of its habitat, making them more difficult to remove. In porous materials, mold grows into all the empty crevices, which is why it is often impossible to remove all the mold from ceiling tiles (or soft foods like bread).

Mold growing under a windowsill and near the carpet of a home
Mold growing in a Nashville home following a flood
Martin Grube, FEMA // Public Domain

Getting rid of the unsightly growth in your damp bathroom is more than just a matter of aesthetics. Indoor mold can cause allergic reactions, such as a stuffy nose or itchy eyes, and can lead to infections for people with compromised immune systems. Some people are more sensitive to mold than others, and may experience more symptoms when exposed to it. Generally speaking, though, mold spores are everywhere, so you’re never going to live a totally mold-free life. Spores will come into your home through windows, doorways, ventilation and climate control systems, and via your clothing, shoes, and pets.

But there’s only one way to effectively inhibit mold growth at home: Get rid of the moisture. That means fixing leaks, getting better ventilation, and possibly running a dehumidifier, according to the CDC’s recommendations on mold.

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What Happens to Films Selected for Preservation by the Library of Congress?

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iStock

On Wednesday morning, the Library of Congress announced its latest slate of movies selected for permanent safekeeping in the National Film Registry. As always, the picks varied widely. The National Film Registry’s class of 2018 includes Cinderella (1950), My Fair Lady (1964), Jurassic Park (1993), The Shining (1980), Smoke Signals (1998), and the animated short Hair Piece: A Film for Nappy-Headed People (1984), which was produced by Ayoka Chenzira, one of the first black female animators.

Originally established in 1988, the National Film Preservation Act tasks the board with selecting American films that are “culturally, historically, or aesthetically" significant. They can pick up to 25 per year, and the movies must be at least 10 years old. The National Film Preservation Board is made up of representatives from a number of industry organizations, including the Academy of Motion Picture Arts and Sciences, the Directors Guild of America, and the National Society of Film Critics. With the new selections, there are 750 films in the registry.

Selection for the registry is an honor, of course, but what does it mean beyond that? How does the Library of Congress, the U.S. legislature’s storage agency for documents and media, go about preserving movies?

According to Steve Leggett, program coordinator for the National Film Preservation Board, selection implores the Library of Congress to get the best possible copy of the film in its original format and store it in their vaults at the National Audio-Visual Conservation Center in Culpeper, Virginia. This ensures the film will be available to future generations.

For Hollywood movies, the process is usually pretty easy. “We simply ask the studio to donate a copy,” Leggett told Mental Floss in 2015. In some cases, that isn’t even necessary. The Library of Congress has more than 1 million films on file, many of them sent by studios or filmmakers for the sake of copyright registry. When the original Star Wars was selected in 1989, Leggett says, congressional librarians simply checked that the 35 millimeter print submitted with Lucasfilm’s copyright application was in good shape. It was, so no further action was needed.

For older and more esoteric selections like newsreels, silent films, documentaries, and early technical achievements in filmmaking, Leggett says the library often seeks out a copy from the community of preservationists. Universities, private foundations, and hobbyists that preserve old films might get a call from the Library of Congress if they have a good copy of a National Film Registry selection. In rare cases, the library will barter for the film, using redundant materials on its shelves. Other times, it will make a copy or pay the archivist to make a new 35 millimeter copy for them. The Culpeper facility stores nitrate prints, the original film stock for many early movies, in specialty lockers because the material is highly volatile and flammable.

Silent films can be tricky because studios often released, revised, and then re-released versions of the film. When one is selected, Library of Congress archivists collect as many aspects and versions of the film as they can, which might mean contacting several studios and archivists.

Of particular challenge in 2015 was the induction of Symbiopsychotaxiplasm: Take One, William Greaves’s quasi-documentary of his 1968 theatrical project staged in Central Park. The film was screened often through the years, as Greaves gained a cult following. It was released on DVD in 2006, but the National Film Preservation Act specified that the library should seek a copy in the original format, which it didn’t have. Leggett said Greaves’s 1968 original cut was “lost,” but the library worked with the late filmmaker's estate to create a new 35 millimeter version that resembled it.

The Audio-Visual Conservation Center itself, buried on a mountainside, has storage space controlled to stay cool and dry. “A film could survive for hundreds of years there,” Leggett says. He admits the audiovisual center wouldn’t survive a nuclear strike—in the event of World War III, the world might lose its best copy of Buster Keaton’s The General—“but it did survive an earthquake with all materials intact.”

An earlier version of this article ran in 2015.

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