Why do we yawn?
In the course of a lifetime a human being yawns about 250,000 times, each time on an average of 6 seconds and with the mouth 4 cm open. Once the process of yawning has started, it is not stoppable, just like sneezing or hiccup. All that sounds plausible and well explored. Yet still yawning is one of the big mysteries of science.
Although yawning is an inherent behavior that each and every one of us accomplishes day in, day out, we still don’t know the matter and the function of this mechanism. There must be a biological reason to it, why else do fetuses do it in the maternal body already and don’t stop doing it for a lifetime?
It is clear today that tiredness is by far not the only reason that induces us to yawn. Boredom, hunger and even stress can also be triggers.
Yawning is not a reaction to oxigen deficiency, as we assumed in former times. American psychologist Robert Provine conducted experiments with his students in 1987 already that demonstrated that an enhanced amount of carbon dioxide in the breathing air would not increase the frequency of yawning and on the other hand the oxygen content of the blood would not rise significantly through yawning. In fact yawning stimulates the heat exchange in the brain. That is what British researcher Andrew Gallup, who conducted associated studies some years ago, claims. A brain that is overheated by - for instance - fear or stress is less efficient. We yawn when the body temperature increases and by doing so we ensure that coolish blood is being pumped to the brain. By that the temperature adjusts and the ideal brainpower is guaranteed. Through monitoring human beings and different mammals Gallup also discovered that there must be a correlation between the duration of yawning and the complexity of the brain, yet not to the bodyweight. The more complex the brain the longer the average length of yawning.
So far, so good. And what about the common assumption that yawning is contagious? That is true! According to scientist Giacomo Rizzolatti yawning is referable to certain neural cells that are responsible for intuition und empathy in humans. We emphathize when exactly these cells let us realize how others are feeling. Then we laugh with them, cry with them… and yawn with them. Also an experiment by researcher Catriona Morrison and her team seems to prove that being infected by a fellow human’s yawn indicates the capability for empathy. They exposed testees in a waiting room to the frequent yawning of a fellow being. The researchers counted, how often the not-informed study participants picked up the heartily yawning and yawned with him. A following test was to show more about the testees’ capability for interpreting the emotional expression of other human beings. Those who joined the yawning in the waiting room extra frequently were the ones to come off especially well.
There are many interesting studies on this topic that, owing to space constraints, we can’t list all. Yet, as mentioned at the beginning, the scientific researches in terms of yawning are far from being completed. Everbody is likely to have his individual yawn experiences and probably also his own queries that he hasn’t found any answers to yet. It’s a fact that researches are being carried on. So let’s be curious of which insights the scientists gain in the future.
By the way – if you are interested: The science of yawning is called chasmology.