text: why is yawning addictive? if your in a group and one person starts yawning, why do others also start to yawn? yawning    everyone knows that we yawn more and for longer when we’re bored. that’s one of the reasons it’s so embarrassing. males who are bored tend to have longer yawns than bored females. and most people assume that we do it because our bodies need more oxygen. that sounds sensible, doesn’t it? after all, when we’re bored or tired, we breathe more slowly, so less air goes through the lungs, so the brain signals the lungs to take a deep breath and so we yawn. the trouble is, even breathing enriched air, or exercising so that we breathe faster, makes no difference to how often we yawn. we don’t yawn because we need more air.  we can all agree on what a yawn is like though. it’s a very deep breath, taken with the mouth round and wide open. it ventilates all parts of the lungs, something which doesn’t happen with normal quiet breathing. the mouth opens fairly slowly, closing more swiftly. there’s usually a visible swelling of the throat, our eyes close and we lower our brows. lots of animals appear to yawn, but many of the simpler creatures merely gape – opening the mouth wide and not taking a deep breath. most mammals yawn just like us though. scientists have tried hard to classify human yawns, but actually they all look the same. the only thing that changes is when we do it! there seems to be only two basic types; the ‘social yawn’, and the ‘wake-up’ yawn, which just seems part of our general stretching routine.   and just like stretching, yawning is a reflex. it even occurs in animals that have been born without a correctly formed brain. but normally it’s triggered by stimuli like tiredness, the sight of others yawning or social stress. yawning increases blood pressure and heart rate and also flexes muscles and joints. if you try to stifle or prevent it by clenching your jaws shut, a yawn is somehow less ‘satisfying’. for some reason, the stretching of jaw and face muscles is necessary. yawning seems to keep the brain aroused in situations where sleep is unwanted, like in the early morning and when struggling to stay awake at night. it’s associated with high states of alertness – and stress or fear. at athletics events, you sometimes find participants in the race of their lives standing in the starting block and yawning. or musicians as they psych themselves up before a concert.  all yawns seem to last about six seconds and are very difficult to stop once they get going. they really are infectious – it’s not just a coincidence. studies have shown that forty to sixty percent of people who see a yawn end up by joining in. yawning can be extraordinarily catching. hearing one can trigger a yawn. even sitting alone in a room thinking or reading about one can cause a yawn.  we have a brain mechanism that detects a yawning face – even in our imagination – and which then triggers the same behaviour. once the neurological machinery in our head gets underway it’s hard to stop. but why? it seems that contagious yawning is caused by something very important to humans: empathy, the ability to identify with other people’s feelings.   people who are particularly prone to contagious yawning also tend to score highly on tests that measure levels of empathy. they are people who are in-tune with what others may be feeling and contagious yawning suggests that they’re inclined, in certain situations, to unconsciously mimic their behaviour. they tend to be the same people who say ‘ouch’ when someone else stubs a toe or steps on a sharp object.  this ability to feel empathy for others is an important part of being human. it only develops when we are a year or so old – just like contagious yawning – and no animals show any signs of empathy whatsoever, except chimpanzees and orang-utans. it is a definite advantage to us as a species: binding social groups together through their feelings for one another and bringing individuals closer together.  some schizophrenics are unabl