Who do people yawn when they are tired? The answer is nobody is actually 100% sure, although there has been some research on the subject. It is thought yawning is a signal that conditions are changing in the body, usually from one state of alertness to another. Yawning is one of those reflex things we all do without thinking about it, rather like blinking or breathing.
It is thought that tiredness triggers yawning for a number of reasons. When we are tired our breathing tends to slow down, and as a result, we take less oxygen on board. This tiredness induced oxygen deprivation can often trigger the yawning reflex. Yawning makes us take deeper breaths and this re-oxygenates the blood.
But whilst the above theory sounds very convincing, the fact that babies in utero have been shown to yawn from eleven weeks gestation onwards would suggest that the oxygenation theory is not entirely correct. Babies in the womb have not even taken their first breath, so yawning is clearly not related to oxygen.
When we yawn, the lungs expand and the heart rate increases by around 30%. This is one reason why scientists think that yawning is the body’s way of ensuring we stay alert and awake in potentially dangerous situations. It is also thought that yawning helps to cool the brain down, which also helps raise levels of alertness. This could also explain why paratroopers yawn before they jump. Just to add credence to the theory, some research carried out in 2007 showed that when subjects held ice packs to their foreheads, they were far less likely to yawn.
Although theories abound that yawing is designed to keep us awake, there is another school of thought that says yawning is also helps to relax us before sleep. Yawning helps to stretch the muscles in the neck and jaw, and this in turn helps to release any residual tension and stress.
The question: why do people yawn, is also answered by a different line of theoretical thought that yawning is a subconscious form of communication. Research has indicated that yawning is one of the ways our ancestors communicated and let the group know that it was time to do something different. It is also possible that contagious yawning could have helped to increase the general alertness of the group, which would have been useful in potentially dangerous environments.
Yawning is exceptionally contagious. One person yawns and everyone else usually follows suit. Even reading about yawning can trigger the yawning reflex. So if you are yawning now, then this assertion is definitely true! Some animals also yawn, just like humans. Dogs and cats have the yawning reflex, and dogs often yawn when humans do. Some species of birds also yawn.
But whatever the reasons why we yawn, it is not something we have any control over. If it was, we probably would not choose to yawn right in the middle of an important meeting when our boss is giving an important presentation…