You talk and then the audience starts yawning. And then you can ask people to experiment on their yawns – like closing the lips, or inhaling through clenched teeth, or trying to yawn with the nose pinched closed. It is through experiments like these that we can try to explore a millennia-old mystery: why do we yawn? We all know that tiredness, boredom, or the sight of someone else can all bring along the almost irrepressible urge – but what purpose does it serve the body? Yawning may have the dubious distinction of being the least understood, common human behaviour. We may be closer to an answer, but it’s one that has split the field.
Many theories have instead focussed on the strange, contagious nature of yawning. Around 50% of people who observe a yawn will yawn in response. It is so contagious that anything associated with it will trigger one… seeing or hearing another person, or even reading about yawning. For this reason, some researchers have wondered if yawning might be a primitive form of communication – if so, what information is it transmitting? We often feel tired when we yawn, so one idea is that it helps set everyone’s biological clocks to the same rhythm. In my view the most likely signalling role of yawning is to help to synchronize the behaviour of a social group – to make them go to sleep more or less at the same time. With the same routine, a group can then work together more efficiently throughout the day.
|Danario Alexander of the San Diego Chargers yawns before the start of an American football match|
Perhaps the best evidence comes from two troubled women who approached Gallup soon after he first published his results. Both were looking for relief from pathological yawning attacks, sometimes lasting an hour at a time. “They’d have to walk away and go to a secluded area – it affected their personal and professional lives,” says Gallup. Intriguingly, one of the women found the only way to stop the yawning attack was to throw herself into cold water. Inspired, Gallup asked them to place a thermometer in their mouths before and after the attacks. Sure enough, he saw a slight rise in temperature just before the yawning bouts, which continued until it dropped back to 37C.
Importantly, this brain chill might underlie the many, seemingly contradictory, events that lead to yawning. Our body temperature naturally rises before and after sleep, for instance. Cooling the brain slightly might also make us more alert – waking us up when we are bored and distracted. And by spreading from person to person, contagious yawns could therefore help a whole group to focus.
|Does this picutre make you yawn?|
Yawning – and perhaps other bodily functions, like sneezing – shares some strange parallels with sex. The facial expressions involved are surprisingly similar – just take a look at this picture and you can see where he’s coming from.
|Like sex, yawns and sneezes involve a build-up that ends in a pleasant climax|
I’m willing to bet you’ve been stifling a few yawns yourself by this point. So go ahead, let it out – and do so in the knowledge that you are enjoying one of life’s most enduring mysteries.
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