Yawn. Simply reading that word probably got you to yawn. And while yawning is definitely a contagious phenomenon, the subject of yawning itself is not at all yawn-worthy. In fact, it's a mystery - researchers are still figuring out the purpose of yawning. See if you can manage to stifle your yawn reflex - that deep inhalation, that stretching of your jaw, the scrunched-up eyes, that long exhalation - as you gape at these theories about yawning.
A yawn is not the body's attempt to gulp up more oxygen. Though you may sometimes yawn to catch your breath, this common yawning myth was disproved years ago. In fact, yawning and breathing are triggered and controlled by totally different body processes.
A yawn can't be denied. Dr. Robert Provine, a noted yawn expert, says that a yawn has the "inevitability of a sneeze." Even when you try to clench your jaw and hold back a yawn, it still slips through. A stifled yawn will likely last just as long as a full-blown yawn, though it may not feel as satisfying.
Yawning may help us to rise and shine. Yawning happens as part of a process called pandiculation, a big, fun word that merely means "a stretching and stiffening" of the body. Envision a cat rising from a catnap, lifting its backside, stretching its front paws forward, and opening its jaws wide. We do essentially the same thing when we yawn and stretch as we awaken. Some researchers theorize that this rise-and-shine routine is how the body reverses the disorienting effects of REM sleep and gets us ready to be up and about. When we stretch, we reposition our body. When we yawn, we arouse our self-awareness. On the other hand, studies show that yawning seems to do little to energize us or help us fight back the urge to sleep once it hits.
Our yawning habits may be as unique as we are. Are you a morning person? A night owl? If you're an early riser, you probably yawn less often than more nocturnal folks. If rising with the dawn is difficult for you, you likely yawn a lot - especially in the morning! There may be an age link here, too, since it seems that as we age, we need less sleep and we yawn less often.
Yawning may be air conditioning for the brain. One currently "hot" theory says that yawning cools our brains down. The brain's temperature can spike during stressful moments, in the midst of a migraine, when we're sleep deprived or just plain drowsy. The body attempts to thermoregulate, or control the body's temperature, by releasing heat through the skull, veins in the face, or via the numerous sweat glands of the forehead. But if these methods fail, yawning may take over. As we yawn, our heart rate and blood pressure increase, and the squeeze-and-relax actions of our facial muscles enhance blood flow. We breathe in a great volume of cooler air, too, and all of these actions may help to balance brain temperature.
Humans aren't the only ones who yawn. Anyone who has spent any time around cats or dogs knows that humans aren't the only animals who yawn. Many vertebrate animals yawn, in fact, including pigs and some primates. The difference is that most animals don't yawn out of boredom. Some are thought to yawn in order to regulate temperature, to assert dominance, to synchronize behaviours, or as part of courtship rituals.
Yawns are contagious. You probably didn't need to be told this fact. During the course of reading this article, you've yawned at least once or twice, right? Empathy is at the heart of most contagious yawn theories, and people with empathy-impairing disorders like autism and schizophrenia have helped to illuminate this theory. When tested against people without these types of disorders, empathy-impaired subjects have been observed as less susceptible to contagious yawning. Being able to identify and connect with others has been an important evolutionary survival skill - but why would we identify through yawns? The earliest evolutionary purposes of contagious yawns are still a mystery.
Humans aren't the only ones who can "catch" a yawn. Empathy could be the key to unlocking the mystery of contagious yawning, but the reverse may be true as well! Contagious yawning noted among chimpanzees opens up the possibility that our closest animal relatives could share advanced self-awareness and empathy similar to ours. Dog owners may have suspected that they share a bond of empathy with their pets, but research proves it's a definite possibility. Dogs can actually "catch" the yawn urge from us humans. When sitting in a room with a yawning stranger, 21 out of 29 dogs yawned back.
Yawning may warn of more than boredom. If someone's yawning a lot, they may not be uninterested in you - something more serious may be going on. Certain kinds of medication can cause a surge of yawns, and yawning often happens before a fainting spell. Excessive yawning has also been linked to symptoms of heart problems and stroke.