why are yawns contages?
480001
Virtually any stimulus associated with yawns -- including viewing, reading about, and even thinking about, yawning -- evokes yawns. (Are you yawning yet?) Yawning spreads in a chain reaction through a group, a compelling example of human herd behavior and a reminder that we are not always in conscious control of our actions. The urge to replicate an observed yawn is clearly an automatic response triggered by our brains.
54372
Well, I don't know why yawns are contagious because scientists really don't know what cause yawn's in the first place. However, on a lesser level, I believe yawns are contagious because when you see someone yawn, you tend to think of how tired you are. Therefore, you yawn too. And plus it is pretty amusing when you have a yawn fest with someone and just cannot stop yawning back and forth.\nHope this helps!\n\nP.S. I yawned while writing this...twice actually ;)
936410
because your brain thinks the other person is stealing all the air so makes you yawn to try and get some yourself, therefore staying alive.\n\nThere's also that it's merely the power of suggestion.\n\nFound this also http://in.answers.yahoo.com/question/index?qid=20061031003314AAoMMUh
65932
From straightdope:\n\n"nobody really knows. Fact is, we don't know why people yawn, period.\n\nIt was long believed you yawned when there was too much carbon dioxide and not enough oxygen in your blood. A part of your brain called the brain stem detected this and triggered the yawn reflex. Your mouth stretched wide and you inhaled deeply, shooting a jolt of oxygen into the lungs and thence to the bloodstream.\n\nSubsequently, you exhaled a lot of CO2. Often you'd stretch while yawning, which seemed to temporarily improve circulation. You yawned and stretched a lot more when you got tired because your breathing slowed down.\n\nOr so people thought. In recent years, though, a few radicals have said the preceding is all malarkey. Who knows, they say, maybe we yawn because it's too warm in the room.\n\nCecil isn't about to settle the issue here, and he doesn't need to. We merely observe that whatever yawn-inducing conditions prevail for you also apply to your friends.\n\nIf you're out late in some crowded dive, you're probably all tired, all warm under the collar, and all breathing the same stale air. You're probably all on the verge of a yawn, too, and the power of suggestion from seeing one person do it is enough to push everybody else over the edge.\n\nAdults rarely catch a case of the yawns from a child or animal, which tends to corroborate this idea.\n\nChildren usually have different sleep schedules and respiration rates from adults, so you would expect them to yawn at different times. Animals, on the other hand, often yawn not for physiological reasons but as a display of hostility, to which humans are evidently unresponsive."
355807
It is possible that yawns are contagious because at one time in evolutionary history, the yawn served to coordinate the social behavior of a group of animals. When one member of the group yawned to signal an event, all the other members of the group also yawned. Yawns may still be contagious these days because of a leftover response (a "vestigial" response) that is not used anymore. None of this has been proven true and yawns are still one of the mysteries of the mind.
775112
It's a sympathetic reaction that makes them contagious.  A yawn happens when your body is not receiving enough oxygen.  You yawn when someone else yawns because of this sympathetic reaction.  Mythbusters did an experiment on this topic on one of their shows.
1177906
Yawning is your body's attempt to get more oxygen.  When you are tired, your breathing tends to get more shallow, and your body tries to compensate by making you yawn - bringing in more oxygen.\n\nHere's some more information on yawning, and why it's "contagious".
604697
lolol...yawns are contagious..u just made me yawn reading ur question...brat!!!
449198
Not contagious but we are affected by an others yawning. This is called "Alolomimea" funny name but its what its called. Scientists believe that the reason we react to other people yawning is because in our early history ("caveman times") we needed to regulate our sleeping patterns so we could all survive together. Kinda like one for all and all for one deal. So if one of our cavemen buddies was tired we would all need to rest so we could all effectively hunt as a unit. It served  us as a natural "hey dude im tired lets take a break so we can hunt better and not die" It's a true story!
56870
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.\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.
326667
Here are some very cool links about yawning in general and why it is contagious:\n\nhttp://www.howstuffworks.com/question572.htm\n\nhttp://staff.washington.edu/~chudler/yawning.html\n\nhttp://www.world-science.net/exclusives/050309_yawnfrm.htm\n\nBy the way, excellent question.  Hope this helps.\n\nGod Bless!  :)
346467
Yawns are not contagious, its an urban legend. Watch 'Mythbusters' on the Discovery channel.
226680
Because when someone else yawns, it pops your ears. So to pop them back, you yawn. \n\n*No, I'm not making this up. Really. I saw it on Beakman's World when I was like ten. I just have a freaky memory.*
476267
I have no idea, but it happens every time I yawn LOL. I have seen people do it intentionally though.
288559
A yawn is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from boredom. \n\nThe yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn. The reasons for this are unclear; however, recent research suggests that yawning might be a herd instinct.\n\nHerd instinct\n------------\nThe so-called herding instinct is a social tendency in humans to identify with and model many behaviors and beliefs after a larger group of individuals with whom they identify.\n\n\nOther theories suggest that the yawn serves to synchronize mood behavior among gregarious animals, similar to the howling of the wolf pack during a full moon. It signals tiredness to other members of the group in order to synchronize sleeping patterns and periods of activity. It can serve as a warning in displaying large, canine teeth, thus proclaiming, "don't attack while I am sleeping...
410453
we yawn b/c our body is craving more oxygen.. this is fact
337700
From a lack of oxygen. Yawning is when your blood circulation slows down i.e at high altitude average people yawns at least 7 times per minutes.\n\nAlso a sign that adrenaline is slowing down and if inactive, the body will shut down.  Involuntary but necessary, seeing people doing so reminds us that the body needs it...