Everybody yawns — from unborn babies to the oldest great-grandparent. Animals do it, too. But why, exactly, do people and animals yawn? No one knows for sure. But there are many theories about why people yawn.
Yawning, as a mechanism for alertness, begins within the first 20 weeks after conception. It helps regulate the circadian rhythms of newborns, and this adds to the evidence that yawning is involved in the regulation of wakefulness and sleep. Since circadian rhythms become asynchronous when a person’s normal sleep cycle is disturbed, yawning should help the late-night partygoer reset the brain’s internal clock. Yawning may also ward off the effects of jet lag and ease the discomfort caused by high altitudes.
So what is the underlying mechanism that makes yawning such an essential tool? Besides activating the precuneus, it regulates the temperature and metabolism of your brain. It takes a lot of neural energy to stay consciously alert, and as you work your way up the evolutionary ladder, brains become less energy efficient. Yawning probably evolved as a way to cool down the overly active mammalian brain, especially in the areas of the frontal lobe. Some have even argued that it is a primitive form of empathy. Most vertebrates yawn, but it is only contagious among humans, great apes, macaque monkeys, and chimpanzees.
One is that when we are bored or tired, we just don't breathe as deeply as we usually do. As this theory goes, our bodies take in less oxygen because our breathing has slowed. Therefore, yawning helps us bring more oxygen into the blood and move more carbon dioxide out of the blood.
Yawning, then, would be an involuntary reflex (something we can't really control) to help us control our oxygen and carbon dioxide levels. But other studies have shown that breathing more oxygen does not decrease yawning. Likewise, breathing more carbon dioxide does not increase yawning.
Yawning is commonly perceived to be a sign of boredom or tiredness. Dr. Robert Provine, known as the yawn-expert from the University of Maryland, performed a study on 17-19 year old students to test this perception. In comparison to a group of students who watched music videos for 30 minutes, a group who watched an uninteresting color test bar pattern for 30 minutes yawned more . Dr. Provine also suggested that yawning is like stretching. Much like stretching, blood pressure and heart rate can be increased just by yawning. Perhaps animals yawn instinctively when bored or tired to get their blood pumping so that they may be physically stimulated to move or seek a new activity. But then why is it that we yawn after waking up? If we yawn after waking as a physical prompt to become active that's one thing. But yawning as a sign of tiredness can be ruled out if we yawn after waking from a restful sleep. Maybe a study could be done in which a comparison could be made between the hours of sleep and the occurrence of yawning when waking.
Another theory is that The definition of yawning is to open the mouth involuntarily with a prolonged, deep inhalation of air. Yawning is a normal response to fatigue and drowsiness, but excessive yawning can be caused by a vasovagal reaction and may indicate a heart problem. Yawning stretches the lungs and lung tissue. Stretching and yawning may be a way to flex muscles and joints, increase heart rate, and feel more awake.
Other people believe that yawning is a protective reflex to redistribute the oil-like substance called surfactant that helps keep lungs lubricated inside and keeps them from collapsing. So, if we didn't yawn, according to this theory, taking a deep breath would become harder and harder — and that would not be good!
But there is one idea about yawning that everyone knows to be true. It seems contagious. If you yawn in class, you'll probably notice a few other people will start yawning, too. Even thinking about yawning can get you yawning. How many times have you yawned while reading this article?