Why are yawns contagious?
400444
Why is it when I read your question I instantly yawned????
363390
The 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. Other 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..." The contagion of yawning is interspecific (i.e., try yawning in front of your dog). Ironically, yawning in public is generally regarded as impolite in the West, but came into fashion in polite French society for a brief period in the late 18th century. Oddly, sometimes sympathetic yawning may be caused by simply looking at a picture of a person or animal yawning, or even seeing the word "yawn".\n\nAdelie Penguins employ yawning as part of their courtship ritual. Penguin couples face off and the males engage in what is described as an "ecstatic display," their beaks open wide and their faces pointed skyward.
339257
Yeah, the previous answers are right - lack of oxygen to the brain.\n\nBut the big question is why are yawns contagious? Even experts don't know that.
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.
542822
yawning is usually a result of a slight lack of oxygen. therefore if one person yawns, the same conditions exist for others in the room.
85551
I think this deserves to be a featured question.  Here are a few theories and a link below:\n\nEverybody yawns - from unborn babies to the oldest great-grandparent. Animals do it, too. But why, exactly, do people and animals yawn? No one knows for sure. But there are many theories (ideas) about why people yawn. \n\nOne is that when we are bored or tired, we just don't breathe as deeply as we usually do. As this theory goes, our bodies take in less oxygen because our breathing has slowed. Therefore, yawning helps us bring more oxygen into the blood and move more carbon dioxide out of the blood.\n\nYawning, then, would be an involuntary reflex (something we can't really control) to help us control our oxygen and carbon dioxide levels. Sounds good, but other studies have shown that breathing more oxygen does not decrease yawning. Likewise, breathing more carbon dioxide does not increase yawning. Hmmm. Now what?\n\nAnother theory is that yawning stretches the lungs and lung tissue. Stretching and yawning may be a way to flex muscles and joints, increase heart rate, and feel more awake.\n\nOther people believe that yawning is a protective reflex to redistribute the oil-like substance called surfactant (say: sur-fak-tunt) that helps keep lungs lubricated inside and keeps them from collapsing. So, if we didn't yawn, according to this theory, taking a deep breath would become harder and harder - and that would not be good!\n\nBut there is one idea about yawning that everyone knows to be true. It seems contagious. If you yawn in class, you'll probably notice a few other people will start yawning, too. Even thinking about yawning can get you yawning. How many times have you yawned while reading this article? We hope not many!
607567
Urge to yawn on seeing someone else yawn is called reflex yawning. When you see someone else yawn, it sends a message across your brain that you also need more oxygen and as a response your open your mouth wide in an attempt to get in more air and your lungs expand (i.e you yawn).
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.
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.
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!
272413
It is an instinctual social response.  Yawning signals to others in the social group that it is time to rest.
289289
Between 40 and 60% of the population is susceptible to contagious yawns, but the reason why yawns are catching is unknown.\n\nI yawned once when typing up this answer.
394382
Yawns are contagious because people naturally emulate what they see others doing. For more, read a section in the Tipping Point by Malcom Gladwell.
345712
It is herd behavior, it signals when the herd needs to move on to something else. When one person yawns, it is passed along to 'pass the message.'
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...
371295
Yawns are contagious because most of us when seeing another yawn, we will hold our breath unintentionally...those few seconds cause a lack of oxygen which is what makes people yawn! Try it out next time you see someone yawn...make a point to make sure you breathe regularly and you'll see that you won't yawn.
680125
Here's a theory. Yawning can be caused by lack of oxygen, and if a bunch of people are in the same room which is poorly ventilated (no windows open, no air conditioning, or it's a stiflingly hot room) they could all yawn because of this, as they are all in the same place.\n\nEither that or they are all tired! :D