Yawning: It Isn't About Oxygen Anymore
Have you ever wondered why yawns are contagious; have you ever been in class and seen someone across the room yawn and found yourself following along? Have you ever been reading a book and, upon coming across a yawning character, been moved to stretch out your own face muscles? Most likely these things have happened to almost everyone more times than they can remember. I cannot tell you how many times I have yawned in the process of researching and writing this paper. A friend of mine began to yawn uncontrollably as I discussed my ideas with her.
Yawning is a phenomenon that occurs for most people many times a day, yet it is not one that has been studied extensively by researchers. This is an unfortunate fact because he more I read about yawning and thought about number of situations in which it occurs, the more eager I became to better understand what is behind humans' tendency to yawn.
At first, one might see yawning as a silly phenomenon to spend time studying because, well, it is just what happens when we are tired; but it is more complicated than that. We yawn when we are tired, but also when we wake up, when we are bored, and even simply because we see others doing it. When one delves into the unknown of what causes a yawn, he or she will become intrigued by how mysterious the occurrence is and surprised about how little we known about it. The following will discuss the many theories that have been put forward regarding the phenomenon and its contagious qualities and explore the implications and problems with these various theories.
There exist both theories as to why we yawn and theories as to why yawns are contagious. Let us first look into why we yawn. The theory that has long been thought to explain yawning, and the one that has often used in medical textbooks, is that we yawn due to low oxygen levels in the lungs (1). When we are in a resting state, we make use of a very small percentage of our lungs' capacity and are only using the air sacs, or alveoli, in the bottom of our lungs (1). The alveoli partially collapse when the air sacs stop receiving fresh air, cueing our brains to induce a yawn (1). This theory has been largely cast aside, however, because our lungs do not necessarily detect oxygen levels (8).
The interesting contrast to the low-oxygen theory is that some observations have been made that suggest that fetuses in the womb yawn. Doctors have observed fetal yawning in utero at twenty weeks gestation and noted a 'fetal yawning movement' (7). Mouths opened widely resembling a yawn with qualities quite different from those of a brief moment of swallowing and the mouth remained open for around two minutes (7). These observations do not support the oxygen theory because fetuses in utero do not yet have ventilated lungs (8). Other doctors have responded to these observations in the New England Journal of Medicine saying that, "there is too much of a range of variation in...