Why Do We Yawn

Why Do We Yawn – A Mystery

Scientists have been puzzled about yawning for over two millennia. However a new theory has provided some insight regarding the same. David Robson explores and while he was in mid conversation with Robert Provine, he had a compelling urge from deep within his body and the more he tried to suppress it, the more it seemed to spread till it ultimately consumed his entire body.

Ultimately it led him to wonder on how he could stop himself from yawning. He was informed by Provine that this seems to occur often when people talk to him, during presentation. Probably the first person to study yawn was the Greek physician, Hippocrates almost 2,500 years ago who believed that yawning was helpful in releasing noxious air, especially during fever.

He wrote that `just like the large quantities of steam which escape from cauldrons when water boils, the accumulated air in the body is violently expelled through the mouth when the body temperature rises. Various examples of the idea prevailed till the 19th century when scientist projected that yawning supported respiration, activating a rush of oxygen in the blood supply while flushing out carbon dioxide. If this seems to be true, we would expect people to yawn more or less regularly based on the oxygen and carbon dioxide absorption in the atmosphere.

Several Theories Focussed on Contagious/Strange Nature of Yawning

However, when Provine requested some of the volunteers to breathe various combinations of gases, he did not come across any change. Several theories have focussed on the contagious, strange nature of yawning. He commented that around 50% who tend to observe a yawn would yawn in response. It seems so contagious that anything connected with it would trigger one, seeing or hearing another person or even reading about yawning.

It is for this reason that some of the researchers have been speculating if yawning could be a primitive type of communication and if so, what kind of information could it be transmitting? According to Christian Hess, at the University of Bern in Switzerland, the most likely signalling role of yawning is to assist in synchronizing the behaviour of social group. With the same routine, a group could work efficiently together all through the day.With several contradictory and competing concepts an emerging theory of yawning could seem to be vague.

Yawning – Chilling Brain/Stop Overheating

However, for the last few years, a fundamental mechanism has developed which could probably settle all the superficial contradictions. Andrew Gallup, presently at the State University of New York at Oneonta, had been motivated first with the idea during his undergraduate degree when he recognised that yawning could probably help in chilling the brain and stop it from overheating.

 He claimed that the forceful movement of the jaws moved the blood flow around the skull and helped to carry away the excess heat. At the time of deep inhalation, it brought cool air in the sinus cavities and around the carotid artery leading it back into the brain. Moreover, the active movement also flexed the membranes of sinuses, blowing a soft breeze through the cavities which could cause the mucus to evaporate, causing a chilling effect like air-conditioning.

The obvious test was to observe if people were more or less likely to yawn in different temperatures. Gallup observed that in normal conditions, around 48% felt the urge to yawn though when he asked them to hold a cold compress to their foreheads, only 9% succumbed to it.