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You’re Getting Very Sleepy: Why We Yawn

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For many people, the sight, the sound, or the suggestion of another person yawning is enough to set them on their own yawning fit. For me, even seeing my cat begin to yawn and stretch can induce a wave of fatigue that’s enough to make me feel tired.


We yawn when we hit the afternoon slump, and we yawn when we’re ready to call it a day, and sometimes we yawn for no good reason at all. Yawning is an involuntary act that’s shared by many species—not just cats and dogs, but monkeys, apes, other mammals, and even some reptiles. The truth is, not much research has been done about yawning and the reasons behind it, so it remains among the strange, unexplained body quirks that we puzzle over every day. A behavior exhibited by so many different species might appear to be vitally important, but in the case of yawning, its prevalence is anyone’s guess.


Open Wide!
A yawn is a peculiar set of gestures—the mouth gapes open, our abdominal muscles flex, the diaphragm pushes down, and we take in an extra-large breath of air. If you’re like me, watering eyes might also accompany your yawns. The whole process takes about six seconds. Yawns are highly recognizable and humans do them even before we’re born. Research shows that fetuses can yawn as young as eleven weeks old.


Many people yawn when they’re tired or drowsy. Indeed, yawns do accompany feelings of exhaustion or lethargy, but researchers haven’t exactly pinpointed why we yawn. Any ideas that seek to ascribe yawning to a particular purpose are simply theories, not proven medical explanations. The physiological theory of yawning is a popular assumption, and it hypothesizes that yawning results from a lack of oxygen and an overabundance of carbon dioxide. The large draw of breath in a yawn theoretically enables us to take in extra oxygen and remove carbon dioxide from the bloodstream, but this theory has some big holes. If we yawn when we need oxygen, then why don’t we yawn while we’re exercising and our bodies are using up oxygen very rapidly? I’ve never been mid-workout, muscles screaming, and had to stop for a quick yawn. Also, this theory has been tested and disproved; in a study, giving air with additional oxygen or carbon dioxide to the test subjects didn’t reduce or increase the frequency of their yawns.


Some other scientists say that boredom and fatigue exclusively cause yawning. Much of our yawning does occur when we’re tired, but people have been known to yawn even while in the middle of important activities during which they couldn’t have been bored or tired. Boredom doesn’t explain why a singer would yawn immediately before taking the stage, or why an Olympic athlete might yawn right before their big moment. Yawning may help to distribute an important lubricant throughout our lungs, helping them function and enabling them to fully inflate, but that theory still leaves many questions unanswered.  


Can You “Catch” a Yawn?
Adding to yawning’s mystery is the fact that it seems to be contagious. About 50 percent of people report that they’re very likely to yawn when they see other people yawning. Besides humans, chimpanzees are the only other animal known to experience contagious yawning, according to researchers in Japan. Since scientists don’t yet have a firm grasp on what causes yawning in the first place, trying to ascertain why yawns spread from person to person is an even more daunting task.


One theory about contagious yawning postulates that it might have helped hunter-gatherer humans to coordinate their biorhythms and sleep cycles. Yawning demonstrated that it was time to retire for the night, and after one person started to feel ready for sleep, the contagious aspect of yawning helped disseminate the idea throughout the group. Research conducted at the University of Albany suggests that yawning cools the brain so that it keeps people alert, and that groups of people yawning together stay more alert and can more easily detect danger. Yawning is sometimes seen as an unconscious herding behavior, helping to coordinate group movements.


Of course, there’s no imminent danger that causes people to yawn during a boring meeting, and yawning can just as easily occur at midday or midnight, so these theories have much to prove. The best hypothesis about contagious yawning is that the act itself has the power of suggestion. Just as seeing a television show about bugs can make your skin crawl, watching someone else yawn can make you feel drowsy too. The human mind is highly skilled at exerting influence over the body, as demonstrated by the placebo effect and people feeling down and tired on gray, rainy days. Perhaps the most sensible explanation for yawning’s supposed contagion is simply that human beings are highly suggestible and we internalize what we see into how we feel.  


Yawning is a normal bodily function, but an excess of yawning could be a symptom of disease. There are at least ten conditions that count yawning as a symptom. Excessive yawning can indicate the onset of a migraine, and it can be among the signs of ALS (Lou Gherig’s disease), Parkinson’s disease, and multiple sclerosis. Reduced frequency of yawning is a sign associated with schizophrenia. 


Buddhists believe that yawning, along with sneezing, falling asleep, and orgasm, brings on a special state of being in which people experience a “clear light” that allows them to glimpse another level of consciousness. Westerners might think of yawns as rude or discourteous, but the next time you’re bored in a meeting or yawn as a relative shows you their vacation pictures, there’s no need to apologize. You weren’t uninterested; you were just having a spiritual experience.

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