Why do we Yawn?

It is easy to answer this question by saying that yawn is “catching” and we do it when we see others yawning. But that’s really just an easy way out. In fact, there are two or three distinct theories about this subject, some of them based on science and nature, others based on myth and legend. Over the decades, doctors and research specialists have come up with some solid evidence for one or two theories. Yet the absolute truth about human yawning (and even animal yawning) is not really known. It’s possible that it will always remain that way.

We all know that human beings tend to yawn when they need rest. We yawn most when we are just plain tired. But close observation has shown that people also yawn regularly when they wake up from a good night’s sleep. How can this be? There are some partial answers that have come from efforts to find the difference between “tired” yawning and morning yawning.

If there is one fact that shouldn’t be in dispute it is this: yawning is involuntary. We can’t just decide to yawn and then do it. One theory proposes that this non-voluntary action takes place when our brain signals the body that oxygen levels in the blood are too low. In this theory, animals yawn so that they take in plenty of air, to get the necessary oxygen in the blood. But serious research has shown that this is not necessarily the case. One factor that helps prove this theory faulty is that human beings don’t always yawn when they are oxygen deprived at high altitudes (on a mountain hike, for instance). But they often do when they are tired and the blood-oxygen level is low.

Animals living in communities or groups yawn as a way of communicating with others, according to another interesting theory about yawning. This activity might communicate weariness or it might allow a group leader to signal others that it is time to bed down or to get up and start moving in the morning. Therefore, yawning might be one of the most efficient ways to coordinate herd and group movements. This would help explain why one human being or animal might yawn in response to the first yawn. It’s communication! Some people have even added the idea of empathy to this discussion, proposing that animals respond with a yawn as a way of saying “Yes, I understand. Me too.” This helps strengthen the argument for why yawning is and has to be contagious.

In recent medical research, scientists have even found that a fetus will often yawn, starting about three months after conception. Some scientists have even proposed that yawning helps “cool” the brain and surrounding tissue. If we are very tired and have not slept, yawning may be a signal that it’s time to put ourselves at rest (especially the overworked brain).

Several theories have attempted to get at the root cause of yawning. But the real reason may never be known.