why are yawns contagious??
412939
i think they are.. whenever i see anyone yawning i HAVE to yawn
207785
Next to questions that males ask regarding the size of their manhood, this has to be the second most asked question here!\n\nWhy we yawn when we see others yawning has baffled scientists for ages and a number of suggestions have been put forward to explain this phenomenon. What we do know is that yawning is an involuntary action- our brain does it without us thinking about it, even very young babies yawn showing that it's a built in action (Chimps do it too by the way). Just thinking about yawning can trigger the bit of the brain that causes a yawn. http://www.ratlab.co.uk/yawn.htm...\n\nMore theories can be found at the links below: \n\nhttp://www.world-science.net/exclusives/...\nhttp://www.yesmag.bc.ca/questions/yawn.h...
222830
There could be a multitude of reasons. Yawning is caused by a lack of oxygen to the lungs. You yawn because it allows an immense amount of oxygen to your lungs.
75237
I'm a registered sleep technologist.  There is no known cause to yawning. It is still a mystery. There are many, many theories, but none proven, thus far.
346467
Yawns are not contagious, its an urban legend. Watch 'Mythbusters' on the Discovery channel.
292528
Yawns usually occur because you have some lack of oxygen, usually when you are growing sleeping and not breathing properly. When a person yawms next to you, you usually stop breathing yourself, thus triggering a "contagious yawn." Need to prove this false? Next time you see someone yawn, be concious of it and make yourself take a deep breath. You wont get that contagious yawn!
441827
See the article in the site below.  It tells you why we yawn and gives evidence to support the theory that yawning is "contagious" because "as social creatures we are highly inclined to copy one another."\n\nThe article starts by saying that a good trick to see if anyone is checking you out is to yawn and see if anyone else yawns back!  \n\nHope this helps...
273757
Seeing someone yawn, hearing them yawn, or even hearing the word "yawn" triggers a reaction in our brain. Yawn contagion is largely unconscious. Wherever it might affect the brain, it bypasses the known brain circuitry for consciously analyzing and mimicking other people’s actions.\n\nThis circuitry is called the “mirror-neuron system,” because it contains a special type of brain cells, or neurons, that become active both when their owner does something, and when he or she senses someone else doing the same thing. \n\nSo basically, it's an unconscious thing that the brain does, in most cases.
414151
What's behind this mysterious epidemic of yawning? First, let's look at what a yawn is. Yawning is an involuntary action that causes us to open our mouths wide and breathe in deeply. We know it's involuntary because we do it even before we are born. Research shows that 11-week-old fetuses yawn. \n\nThere are many parts of the body that are in action when you yawn. First, your mouth opens and jaw drops, allowing as much air to be taken in as possible. When you inhale, the air taken in is filling your lungs. Your abdominal muscles flex and your diaphragm is pushed down. The air you breath in expands the lungs to capacity and then some of the air is blown back out. \n\nWhile the dictionary tells us that yawning is caused by being fatigued, drowsy or bored, scientists are discovering that there is more to yawning than what most people think. Not much is known about why we yawn or if it serves any useful function, and very little research has been done on the subject. However, there are several theories about why we yawn. Here are the three most common theories: \n\n\nThe Physiological Theory -- Our bodies induce yawning to drawn in more oxygen or remove a build-up of carbon dioxide. This theory helps explain why we yawn in groups. Larger groups produce more carbon dioxide, which means our bodies would act to draw in more oxygen and get rid of the excess carbon dioxide. However, if our bodies make us yawn to drawn in needed oxygen, wouldn't we yawn during exercise? Robert Provine, a psychologist at the University of Maryland, Baltimore County, and a leading expert on yawning, has tested this theory. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning. \nThe Evolution Theory -- Some think that yawning is something that began with our ancestors, who used yawning to show their teeth and intimidate others. An offshoot of this theory is the idea that yawning developed from early man as a signal for us to change activities. \nThe Boredom Theory -- In the dictionary, yawning is said to be caused by boredom, fatigue or drowsiness. Although we do tend to yawn when bored or tired, this theory doesn't explain why Olympic athletes yawn right before they compete in their event. It's doubtful that they are bored with the world watching them. \nThe simple truth is that even though humans have been yawning for possibly as long as they have existed, we have no clue as to why we do it. Maybe it serves some healthful purpose. It does cause us to draw in more air and our hearts to race faster than normal, but so does exercise. There's still much we don't understand about our own brains, so maybe yawning is triggered by some area of the brain we have yet to discover. We do know that yawning is not limited to man. Cats, dogs, even fish yawn, which leads us back to the idea that yawning is some form of communication. \n\nHave we provoked a yawn out of you yet? If we have, hopefully it's not out of boredom, but by the power of suggestion.
378590
People yawn when the level of carbon dioxide in their blood is a little too high, this is bad and eventually can cause unconsciousness.  To stop this you yawn, yawning means you take in a big gulp of oxygen and expel carbon dioxide.  They are thought to be contagious because if I see you yawning my brain thinks.. uh oh there is too much carbon dioxide in this room that person is already feeling the effects, to protect myself I will yawn too!\n\nBy the way you also yawn if you're tired because you're breathing naturally slows which makes carbon dioxide build up more easily.  You will yawn when you are tired to expel this excess carbon dioxide!
272413
It is an instinctual social response.  Yawning signals to others in the social group that it is time to rest.
220911
Why is yawning infectious? \n\nGemma Martin, London UK\nWhen you yawn, you equalise the pressure in your middle ear. This causes a small, localised pressure change around you, which affects others in the vicinity - and therefore they have to yawn to equalise the pressure in their own middle ears. \n\nJoe Lambert, Norwich, England\nIt's a left over mechanism from our days as troupe creatures. Infectious yawning meant that we slept togther as a group when the most tired required to sleep. \n\nPeter Brooke, By Kinmuck Scotland\nIn 1990,in Guardian Notes and Queries vol.1, an answer was that it was part of a mechanism to "synchronise wake/sleep cycles" among people in a social group, and that yawning is poorly understood. I don't know if progress has been made since then. \n\nivor solomons, norwich england\nThis applies only to group/troupe animals. It supplies a method for the most sleepy to forcefully communicate their need for rest and thus ensures that the group rests/sleeps together. \n\nPeter Brooke, By Kinmuck, UK\nYawning is essentially a reflexive method of increasing oxygen intake. Oxygen intake in this manner is primarily used as a means to stay alert. When we observe others yawn it triggers a warning to ourselves that we are in a situation where we need to be alert, hence the infectious desire to yawn yourself. \n\nAndy Preston, Otley, UK\nIf you accept the theory that yawning is related to breathing, as a means to either redistribute lung surfactant or to temporarily increase air intake, it may be that watching someone yawn triggers a subconcious concern about one's own ability to breathe, hence mimicking the yawn. Alternatively, it may be a throwback to primate warning signs, which involve displaying of teeth when threatened. The common response to this is a reciprocal baring of teeth. \n\nBrendan O'Sullivan, Birmingham, UK\nThere is no one answer to this question, other than unsatisfying ones like "because we evolved that way". Or more accurately, some species in our distant past evolved that way (if you yawn at a dog, it will often yawn back, and chimpanzees also exhibit contageous yawning). Yawning might help communicate to other members of a group that it's time for everyone to settle down for a snooze, but (like laughing and frowning), it's hard to explain why this particular behaviour should represent this meaning. \n\nAllan Dean, Wimbledon \nI've heard it's because when the alpha male in the group of apes (which turned into us)had checked everything out and knew it was safe to sleep he would yawn to other apes, as a message that all was safe, and they in turn would yawn the message through the group, so it's instinctive. \n\nDonna Thomas, Bristol, UK\nIt's because you're afraid that other people are stealing your air \n\nJimmy, Ceredigion, Wales\nSteven Platek, a professor of cognitive neuroscience at Drexel University in Phildelphia, has carried out research correlating the "echoing" of yawns with the empathetic response of the individual. In other words it is a kind of social response, and those deficient in the ability to make emotional bonds (schizotypal individuals) are less likely to yawn back. \n\nTony Dunlop, Zeal Monachorum, England
164616
The exact reason is not known but there are a number of theories:\n\n1) Excess of carbon dioxide and lack of oxygen in the blood. The brain trieggers a yawn to expel carbon dioxide and inhale oxygen.\n2) Regulation of body temperature.\n3) An increase of certain neurotransmitters in the brain, specifically serotonin, dopamine, glutamic acid and nitric oxide.\n4) A yawn is similar to stretching in that it increases blood pressure and heart rate and also flexes many muscles and joints.
1049703
Good question!\nMany people believe that we yawns are the cause of to get rid of extra carbon dioxide and to take in more oxygen. Not entirely true (see ref 1 and 3). Sometimes we yawn as we shift phases from being awaken, to feeling sleepy, and anytime during our awakened state. And sometimes they simply are contagious(2).\n\n"Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning. "(3)
467214
Yawns are one of the brain's ways of getting oxygen and fighting fatigue. If someone yawns in response to your yawn it's because they are feeling the same fatigue you are.
433222
because they make one tired so then they person that isn't tires suddenly becomes tires and yawns. but yawns shouldn't make one another person yawn because the person is just releasing co2 from their bodies.
858650
The other two answers are sufficient, but I just want to jump on the band wagon and say the same thing, but I will BS my way through with an elaborate answer so that you may think that I am answering more.\n\nI actually searched the web and found out that most scientists don't know why people yawn. If you are interested, read this short explanation : http://www.madsci.org/posts/archives/aug99/934846431.Gb.r.html\n\nI learned a lot by reading it, I hope it answers your question. You can even e-mail the person about this topic... If you find out, please post the answer and let me know...