Why Do Dogs Sniff Each Other's Butts?

Chloe Effron // Dogs: iStock
Chloe Effron // Dogs: iStock

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

We might giggle when we see dogs sniffing each other’s rear ends, but there’s a good reason why dogs stick their noses in private places. It lets them find out all kinds of things about each other to help them get along and survive. A butt sniff for dogs is like a handshake for humans.

Dogs’ amazing sense of smell is 10,000 to 100,000 times better than humans. They also have a special part of their noses called the Jacobson's organ that lets them ignore the smell of poop when they sniff another dog’s rear. Instead, the organ detects something more important. On the sides of a dog’s anus (AY-nuss)—the place where poop comes out—are special glands that release chemicals telling the body how to grow and work properly. This is what interests dogs the most about each other’s butts. 

The chemicals tell dogs a lot about each other. They help a dog to know if another dog is male or female, how old it is, what it eats, how healthy it is, and even what kind of mood they’re in. The chemicals also help it to know if other dogs are strangers or if they’ve met before. All of this helps dogs decide how they should behave. It's how dogs first get to know each other!

To sniff out more information about dogs and their noses (and their butts!), see this video by Reactions.

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

bhofack2/iStock via Getty Images
bhofack2/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]

Sorry, Plant Parents: Study Shows Houseplants Don’t Improve Air Quality

sagarmanis/iStock via Getty Images
sagarmanis/iStock via Getty Images

Sometimes accepted wisdom needs a more thorough vetting process. Case in point: If you’ve ever heard that owning plants can improve indoor air quality in your home or office and act as a kind of organic air purifier or cleaner, you may be disappointed to learn that there’s not a whole lot of science to back that theory up. In fact, plants will do virtually nothing for you in that respect.

This botanic bummer comes from Drexel University researchers, who just published a study in the Journal of Exposure Science and Environmental Epidemiology. Examining 30 years of previous findings, Michael Waring, an associate professor of architectural and environmental engineering, found only scant evidence that plants do anything to filter contaminants from indoor air.

Many of these studies were limited, the study says, by unrealistic conditions. Plants would often be placed in a sealed chamber, with a single volatile organic compound (VOC) introduced to contaminate the air inside. While the VOCs decreased over a period of hours or days, Waring found that the studies placed little emphasis on measuring the clean air delivery rate (CADR), or how effectively an air purifier can “clean” the space. When Waring converted the studies' results to CADR, the plants's ability to filter contaminants was much weaker than simply introducing fresh air to disperse VOCs. (Additionally, no one is likely to live in a sealed chamber.)

The notion of plants as natural air filters likely stemmed from a NASA experiment in 1989 which argued that plants could remove certain compounds from the air. As with the other studies, it took place in a sealed environment, which made the results difficult to translate to a real-world environment.

Plants can clean air, but their efficiency is so minimal that Waring believes it would take between 10 and 1000 of them per square meter of floor space to have the same effect as simply opening a window or turning on the HVAC system to create an air exchange. Enjoy all the plants you like for their beauty, but it’s probably unrealistic to expect them to help you breathe any easier.

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