1. Humans Only Use 10% of Their Brains
This one is especially popular in self-help books and sci-fi movies. It implies we all have vast untapped potential just waiting to be unlocked. But neurologists have debunked it repeatedly—brain imaging shows that we use all parts of our brains, even while resting. Different regions light up for different tasks, but none are just sitting idle.
The origin of this myth is murky—it might have started with a misquote of early 20th-century psychologists. Hollywood definitely helped keep it alive, with movies like Lucy and Limitless running wild with the idea. It sounds inspiring, which is why people like to repeat it. But the truth is, your brain’s already working hard—you’re just not always aware of it.
2. You Swallow Eight Spiders a Year in Your Sleep
This one feels designed purely to haunt your dreams. The idea that spiders routinely crawl into our mouths at night and meet their end while we snooze is pure fiction. Arachnologists and sleep experts have both said this would be extremely unlikely—spiders avoid humans, especially breathing ones. And our mouths? Full of vibrations and moisture, two things spiders hate.
The myth probably gained traction in the early days of the internet, when weird facts spread unchecked. It was even suggested that a writer made it up just to show how easily misinformation spreads. The number eight seems oddly specific, which probably helped it stick. But rest easy—your mouth isn’t a spider trap.
3. Lightning Never Strikes the Same Place Twice
This one sounds poetic, but nature doesn’t follow catchy slogans. Lightning absolutely does strike the same place more than once, especially tall or isolated objects. The Empire State Building, for example, gets hit by lightning roughly 20 to 25 times a year. That’s because lightning is drawn to the path of least resistance, not novelty.
The idea probably caught on because it gave people a sense of safety—“it already happened here, so I’m good.” Unfortunately, that’s not how electricity works. If a structure is high, metal, or well-grounded, it’s actually more likely to get hit again. So if you’re near something like a tall tree during a storm, move—not because it’s safe now, but because it’s a lightning favorite.
4. Hair and Fingernails Keep Growing After Death
This one has a creepy ring to it, which is probably why it stuck around. The idea is that corpses continue to grow hair and nails, making death even more unsettling. But the truth is that it’s an optical illusion—after death, the skin dehydrates and shrinks, making hair and nails look longer. There’s no actual growth happening because the body’s systems shut down.
It’s easy to see how this myth took off in pop culture and horror stories. Visually, it fits the eerie tone often associated with death. But scientifically, growth requires cell activity, which stops once a person dies. So no, the dead aren’t growing ghostly claws overnight.
5. Cracking Your Knuckles Causes Arthritis
For years, parents and teachers warned that cracking your knuckles would lead to arthritis. It was a go-to scare tactic to stop the habit, often paired with exaggerated hand-wringing gestures. But science hasn’t found a connection—multiple studies show that habitual knuckle cracking does not increase your risk of developing arthritis. At worst, it might annoy the people around you or slightly weaken your grip over time.
This myth likely persisted because the sound itself is unsettling, and people just assumed something that loud had to be bad for your joints. In reality, the noise comes from bubbles forming and collapsing in the joint fluid. It’s harmless, even if it makes others wince. So feel free to crack away, guilt-free.
6. Gum Stays in Your Stomach for Seven Years
Everyone remembers being told this as a kid, usually right after swallowing a piece of gum. The warning sounded serious—your stomach, now a sticky graveyard, unable to break it down for seven years. But that’s not how digestion works. While gum is tough to digest, it doesn’t just sit there for years; it usually passes through your system in a few days like other indigestible items.
This myth stuck because gum does feel different from food—it’s chewy and doesn’t break down in your mouth. That difference probably made people assume it behaved weirdly in the body too. But your digestive system is surprisingly efficient at moving things along. It doesn’t care how minty they are.
7. Bulls Hate the Color Red
Thanks to cartoons and bullfighting imagery, red has long been seen as a bull’s trigger color. But the truth is, bulls are colorblind to red. What actually provokes them is the movement of the matador’s cape, not its hue. They’d charge at a white or blue cloth just the same, as long as it’s flapping dramatically.
This myth took hold because red is such an emotionally charged color for humans—it looks aggressive, so we project that onto animals. Plus, bullfighting traditionally uses red capes, which makes it visually easy to remember. But scientifically, it’s the motion that makes the bull mad, not the palette. So it’s not personal—it’s kinetic.
8. You’ll Catch a Cold If You Go Outside With Wet Hair
This one’s a classic from grandmas everywhere. The idea is that stepping out with damp hair in chilly weather is basically begging for a runny nose. But colds are caused by viruses, not temperature or moisture. Being cold doesn’t introduce a virus into your body—it might slightly suppress your immune response, but it doesn’t conjure illness from thin air.
This myth stuck around because people often did catch colds in the winter, and wet hair seemed like an easy scapegoat. But what really increases your risk in colder months is more time spent indoors, in close contact with others. Germs love warm, crowded places, not breezy sidewalks. So blame your coworker’s sneeze, not your damp bangs.
This post 8 Formerly Common American Beliefs That Are Basically Urban Legends Now was first published on American Charm.
