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Yawn and oxygen

Besides the common cold, the most contagious thing known to humanity is yawning! What bizarre forces are at work here? Dr Karl has been trying to stay awake long enough to find out...

We were having a meeting at the end of a long and hard day spent working on a totally new project (in the daring field of comedy-science TV), when suddenly, a bout of contagious yawning spread through the group. The person who started off this mini-epidemic of yawning said, in her defence, that she must be low in oxygen, and that was why she had to have a big yawn - to get more air in. Like all good myths, it has only a tiny whiff of truth.

Certainly, after you've been doing a few hours of constant breathing at rest, your lungs become "stiffer" and less compliant. And yes, one decent yawn will return your lungs back to their usual flexibility. However, this does not affect blood oxygen levels (at least, not in healthy people). Now one of the leading Yawn Experts on the planet is Robert R. Provine, professor of psychology at the University of Maryland. He's been studying yawning for decades. He did the experiment where he checked rates of yawning, in terms of how much oxygen the volunteers breathed in. Our normal air is mostly nitrogen (about 80 per cent), and only about 20 per cent is oxygen. Well, forget this wimpy 20 per cent rubbish. Even when he gave his volunteers 100 per cent oxygen to breathe, they still yawned at the same rate.

Yawning has all kinds of strange links to different aspects of human experience.

For example, the yawn has a strange link to sexuality. In male rats, medications that make them yawn and stretch will give them erections. In most humans, antidepressant drugs such as clomipramine and fluoxetine can put a damper on sexual desire and performance. But in a tiny minority of people, these medications have the interesting side effect that whenever that person yawns, he or she has an orgasm.

Another weird link is that when you yawn, you sometimes spontaneously stretch your arms – and this can lead to a bizarre phenomenon. For example, a stroke occurs when part of the blood supply in the brain is blocked, causing damage to the brain. So, a stroke could leave a person paralysed on one side of their body, due to localized damage in the brain. No matter how hard they try, they cannot move the arm on that side. But back in 1923, the British neurologist, Sir Francis Walshe noticed that when they yawned, a few of the stroke victims would move their otherwise-paralysed arm.

And here's another strange link. In heart attack victims and in people recovering in Intensive Care Units, a spontaneous yawn is a sign that hopefully the person is on the way to recovery.

Yes, yawning is correctly linked to tiredness and to boredom – but sometimes super-awake and super-interested people will yawn. Look carefully at the athletes getting ready for a sports event. They will have trained for ages for this one short event, and they will be fully alert and well-rested – and yet they will yawn before their race, or bout or parachute dive. Musicians about to perform will often yawn, perhaps because of nervousness. Dogs preparing to attack, and Siamese Fighting Fish about to rumble will all yawn, perhaps in anticipation. These are all seemingly-odd times for a yawn to erupt.

So one theory is that yawning is associated with a transition – from waking to sleep (and vice versa), alert to bored (and vice versa), sexual arousal (and vice versa) and indeed, changing from any one activity to any other activity. However, we still don't understand contagious yawning yet. But we do know that empathetic types (the people who say express concern when you stub your toe) are more likely to "catch" a yawn, while "cold fish" types are pretty much immune to yawning in synchrony.

And finally, we know that thinking, hearing or reading about yawning has a 50 per cent chance of setting you off yawning. So, did this story make you yawn, or am I just really boring?

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