Why do we yawn? Nobody knows for sure. It is one of those things, like falling in love, that everybody does but nobody can explain. There are many theories out there for both these human conditions. But that is exactly what they are – theories.
Being tired makes us yawn
Most people yawn when they are bored or tired. Right. But WHY? The theory is that we do not breathe deeply enough when we are tired and yawning supplies extra oxygen and gets rid of excess carbon dioxide. Yes, it is true that yawning opens the mouth wide; we breathe in deeply and exhale deeply and slowly as well. But this theory has been tested and found lacking. Giving people extra oxygen during experiments did not stop them from yawning nor did they yawn more often when breathing extra carbon dioxide. So much for that theory.
Others believe that the yawning wakes us up a bit more, because it stretches our lungs and other muscles associated with breathing, such as the diaphragm. Exercising muscles makes us more awake and increases the heart rate, right? Well maybe so, because many people yawn while they are exercising and some athletes yawn just before the start of a race. But that is not it for yawning, either.
Then there is the evolution theory. This is an interesting one. Some scientists believe we started yawning in prehistoric times as a way to show others our teeth, as a kind of warning growl. A sort of yawning haka, to intimidate our opponents?
The next (unproven) theory on the list is that the act of yawning helps to keep the lungs lubricated. The inside of the lungs is coated with an oil-like substance called surfactant. It sort of oils the lungs and keeps them from collapsing. Otherwise, we would find taking deep breaths harder and harder. Yawning to oil the lungs? Mmmm.
Yawning ventilates the brain
A reasonably new theory that sounds quite intriguing is that yawning flexes the sinuses and cools down the brain. It is essential that the brain does not overheat. There is a theory around that seems to explain the function of the sinuses, something that has always puzzled scientists. It seems sinuses expand to cool the brain and yawning seems to supply cool air, particularly to the sinuses behind the cheekbones. So yawning might just be a manual fan to the brain. There has been limited experimentation proving that the temperature of a person and of laboratory rats is higher just before yawning and significantly lower after yawning.
Feeling empathy might be related to yawning
Then there are strong suggestions that our ability to yawn is closely tied up with being able to feel empathy. Yes, apparently the better you yawn, the more empathy you feel for others. Experiments on autistic children have showed that they are not big on yawning. An autistic person lacks the skill of social interaction with other people, especially the skill to empathise with others. Non-autistic children would yawn very readily when others around them did, while autistic children hardly yawned in response to observed yawns.
Whatever the reason for yawning, one thing is clear; it is certainly contagious. Simply put, when others yawn, so do you, without being able to help yourself. Quite a neat party trick! Even fetuses in the womb have been observed to yawn and surely they are not bored or in need of extra oxygen to their lungs (as they do not actually breathe air).
This guest post was written and contributed by health blogger Zoe. For more information on sleep and how to get a great night’s rest, visit Archers Sleep Centre.