Why Do I Cry?

Chloe Effron
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.

Here’s the easy answer: you cry because your brain tells a gland under each of your eyelids to make tears. These are called the lacrimal (LAH-kruh-mul) glands. But your body doesn’t just make one type of tear. It makes three! Each type of tear has a special job to do.

Some tears protect your eyes. Basal (BAY-sul) tears spread over your eyes all the time to keep them moist and get rid of bad bacteria. Reflex tears wash away stuff that gets in your eye, like sand or dirt. And then there are emotional tears. These are connected to your emotions, or feelings, like sadness, anger, fear—even happiness! These strong feelings cause your heart to pump faster, your breathing to speed up and the opening in your throat to get bigger, making it hard to swallow. They also cause your eyes to make emotional tears. A lot of people feel calmer after they cry, but we’re not sure why. Emotional tears are unique to humans. We are the only creatures on Earth that cry because of our feelings.

Some scientists think we cry as a result of how ancient humans learned to survive. Crying and tears may have been ways to let other people know we are upset and that we want help from them. We know babies cry loudly to get help from their parents. But as we grow up and learn to take care of ourselves, we make less noise when we cry and instead make tears. Some scientists think early humans learned that quieter crying kept them safe from enemies, and from getting caught by wild animals that might eat them! But with tears, they could still let other people know they needed help without making a lot of noise.

For further reading, check out our story "7 Teary Facts About the Science of Crying." 


'Lost Species' of Tiny, Rabbit-Sized Deer Photographed in Vietnam for the First Time in 30 Years

Global Wildlife Conservation
Global Wildlife Conservation

The silver-backed chevrotain, also called the Vietnamese mouse-deer, is elusive. It's so elusive that scientists had feared it was extinct after none had been photographed for decades. But as The Washington Post reports, the first images taken of the mammal in nearly 30 years prove that the species is still alive in the woods of Vietnam.

No larger than small dogs, chevrotains are the tiniest ungulates, or hoofed animals, on Earth. They have vampire-like fangs and skinny legs that support their bodies. Silver-backed chevrotains are characterized by the silver sheen of their tawny coat.

The tiny population native to Vietnam has been devastated by poachers in recent decades. That, and the animal's natural shyness, make it incredibly difficult to study. Before this most recent sighting, the last time scientists had recorded one was in 1990.

Global Wildlife Conservation, the Southern Institute of Ecology, and the Leibniz Institute for Zoo and Wildlife Research teamed up in hopes of documenting the lost species. Researchers interviewed residents and government forest rangers in the Vietnamese city of Nha Trang about the silver-backed chevrotain, looking for tips on where to find one. Residents said that while populations had been hit hard by hunting, the animals were still around.

Based on this local ecological knowledge, scientists set up three camera traps in the Vietnamese woods. In just five months, they captured 275 photographs of the little mouse-deer. They then installed 29 additional cameras and snapped 1881 new images in that same length of time.

“For so long this species has seemingly only existed as part of our imagination," Global Wildlife Conservation associate conservation scientist An Nguyen said in a statement. "Discovering that it is, indeed, still out there, is the first step in ensuring we don’t lose it again, and we’re moving quickly now to figure out how best to protect it.”

Now that a silver-backed chevrotain population has been located, researchers plan to conduct the first-ever comprehensive survey of the species. Once the data is collected, it will be used to build a plan for the species' survival.

[h/t The Washington Post]

The Great Tryptophan Lie: Eating Turkey Does Not Make You Tired

H. Armstrong Roberts/iStock via Getty Images
H. Armstrong Roberts/iStock via Getty Images

While you’re battling your cousins for the best napping spot after Thanksgiving dinner, feel free to use this as a diversion tactic: It’s a myth that eating turkey makes you tired.

It’s true that turkey contains L-Tryptophan, an amino acid involved in sleep. Your body uses it to produce a B vitamin called niacin, which generates the neurotransmitter serotonin, which yields the hormone melatonin, which helps regulate your sleeping patterns. However, plenty of other common foods contain comparable levels of tryptophan, including other poultry, meat, cheese, yogurt, fish, and eggs.

Furthermore, in order for tryptophan to produce serotonin in your brain, it first has to make it across the blood-brain barrier, which many other amino acids are also trying to do. To give tryptophan a leg up in the competition, it needs the help of carbohydrates. Registered dietitian Elizabeth Somer tells WebMD that the best way to boost serotonin is to eat a small, all-carbohydrate snack a little while after you’ve eaten something that contains tryptophan, and the carbs will help ferry the tryptophan from your bloodstream to your brain.

But Thanksgiving isn’t exactly about eating small, well-timed snacks. It’s more about heaps of potatoes, mountains of stuffing, and generous globs of gravy—and that, along with alcohol, is more likely the reason you collapse into a spectacular food coma after your meal. Overeating (especially of foods high in fat) means your body has to work extra hard to digest everything. To get the job done, it redirects blood to the digestive system, leaving little energy for anything else. And since alcohol is a central nervous system depressant, it also slows down your brain and other organs.

In short, you can still hold turkey responsible for your Thanksgiving exhaustion, but you should make sure it knows it can share the blame with the homestyle mac and cheese, spiked apple cider, and second piece of pumpkin pie.

[h/t WebMD]

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