Why do we yawn?
What's the real reason we yawn?
Chances are by the time you finish reading this article, you will have yawned at least once. Yawning is one of the most intriguing human behaviors. And the fact of the matter is we simply don't really know why people and animals yawn.
Commonly-held wisdom says that people yawn because they are tired or bored. But there really aren't any studies that support this claim. The sum of the scientific evidence is that yawning is an involuntary respiratory reflex, but that still doesn't answer the question, Why do we yawn?
What a Yawn Really Is
Technically-speaking a yawn is the reflex opening of a person's mouth, followed closely by the deep inhalation and exhalation of air. The corresponding sighs and noises that often accompany yawns are actually optional.
What Yawning Accomplishes
Yawning is a biological mechanism that helps to regulate the carbon dioxide and oxygen levels in your blood. The act is instigated and controlled by the spinal and nerve centers. Most scientists believe that yawning is triggered by fatigue or boredom, because during these times breathing may be more shallow than normal, transporting a smaller amount of oxygen to the lungs through the cardiovascular system.
During a yawn a person's alertness is heightened by the sudden intake of oxygen, which increases the heart rate, rids the body of any carbon dioxide buildup and forces oxygen through the blood vessels and to the brain. Shortly after the yawn is finished normal breathing resumes and ventilates the lungs. This system regulation vaguely answers the question Why do we yawn? But many mysteries remain.
Mysteries of a Yawn
One of the most mysterious aspects of yawning is its contagious nature. How often have you begun yawning when you see someone near you doing the same? Most scientific analysts will tell you that the power of suggestion is strong, and you really don't need to yawn when you see a friend or coworker yawning, you just think you do. This answer doesn't really help us understand why people with lower brainstem damage or multiple sclerosis often yawn excessively, however. It also doesn't explain why fetuses yawn in the womb (at as young as 11 weeks!), since they do not breathe oxygen until they are born.
So, why do we yawn? No one really knows. Don't get upset when someone begins yawning while you are speaking to them. It's just an involuntary, mysterious behavior that most people have a hard time controlling. The accompanying roll of the eyes or loud bored noises (a common behavior by teens when they are in the vicinity of their parents) are completely controllable, however.