Yawning

 

Yawning

There has been relatively little research carried out on the subject of yawning, but it is known that humans yawn about twenty times a day and also that babies in the womb yawn from about 11 weeks’ gestation. Tiredness and boredom are cited as common causes of yawning. (Surely unborn babies aren’t bored? ‘I’m fed up hanging around in here. There’s nothing to do or see. There must be more to life than this.')

A yawn is an involuntary reflex, involving an intake of breath through the mouth and a swift exhalation. In addition to yawning when weary or bored, conversations about yawning can cause participants to yawn. Simply reading the word ‘yawn’ triggers the reflex.

Yawning is contagious, perhaps even more so than smiling, but children are not affected by contagious yawning before the age of four. It is difficult to resist the urge to yawn when others are doing so. Yawns aren’t always silent, either. They are frequently accompanied by sighs or verbalisations like, ‘Oh, dear me’ or perhaps inarticulate grunts or groans. Stretching often plays a part, too.

Gallup, in the journal ‘Evolutionary Psychology’, presented the hypothesis, in 2007, that yawning regulates brain temperature. Taking a lot of air into the lungs through yawning cools the blood that flows to the brain and improves the ability to concentrate.

In 2014, researchers looked at how outdoor temperatures affected the frequency of yawning. When it’s hot, people yawn more. When the temperature drops yawning is less frequent. When it reaches 37° C (98.6°F) which is the average body temperature, yawning is no longer effective in cooling the brain.

However, the hypothesis, though popular, is not proven. For example, it cannot account for mouth-gaping or yawning in cold-blooded animals.

Many animals yawn. Contagious yawning is thought to be an evolutionary behaviour, particularly in pack animals, to induce attention within the group and alertness to danger. The theory is that if an individual yawns, it is indicating to the rest that it is sleepy and therefore less vigilant. The yawn spreads, increasing the overall watchfulness and safety of the pack.

Human yawns are contagious to dogs, but it is not certain that cats are similarly affected.