why are yawns contagious?
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.
1051186
When a person yawns it is usually due to the lack of oxygen to the brain. When we see a person yawning our brain interprets  it as low level of oxygen in the air.As a result we yawn.
922965
THE TRUTH IS that we don’t completely understand why people, or animals for that matter, yawn. It’s widely assumed that yawning occurs because we are tired or bored or because we see someone else doing it, but there isn’t any hard evidence to support these beliefs.\n\nThe most plausible explanation, and the one that is taught in medical school, is that we yawn because oxygen levels in our lungs are low. Studies have shown that during normal, at-rest breathing, we don’t use anywhere near our lung capacity; for the most part, we just use the air sacs at the bottom of the lungs. If the air sacs, called alveoli, don’t get fresh air, they partially collapse and the lungs stiffen a bit. As a result, it’s believed, our brain prompts the body to either sigh or take a yawn to get more air into the lungs\nalso when we someone else yawn if someone else yawns, we are naturally competitive so if someone else is getting more oxygen, our body wants more.
276956
When working out the blood flow is increased to the working muscles. As a result there is less blood and oxygen flowing to the brain triggering the yawn. This is your body's way of increasing the oxygen level in the brain to compensate.\nAs your body accomodates the increased physical demand, the yawning should become less.
461426
Seeing running water makes you want to go, it's the same with yawning, it's an involuntary reaction to seeing someone else do it before you. \nAn Auto suggestive sequence and it can spread.
967357
The answer is, no one really knows why yawning is "contagious". Or why we yawn at all. One popular explanation is that yawning allows you to get rid of too much carbon dioxide in your system and increase your oxygen supply. This was disproved by Dr. Robert Provine and his research team in 1987.\n\nNow scientists are wondering if yawning is from our deep past -- part of our evolutionary history. Did a yawn signal to the group that it was time for everyone to retire to the trees and snooze? Did a yawn signal that we were all feeling cozy and warm about each other? Did a yawn signal something more like, "Gee, I know how you're feeling, I feel that way too."\n\nBetween 40 and 60 percent of the population seems to find yawning contagious. Researchers at the State University of New York conducted a series of yawning experiments. They determined that being self-aware (the ability to recognize oneself) and having the ability to see things from someone else's viewpoint means a person is more likely to find yawning contagious.\n\nNow you're thinking, what humans are not self-aware? Schizophrenics sometimes have trouble with self-recognition so they will not find yawning contagious. Babies won't yawn contagiously until they're more than a year old.\n\nSome birds and reptiles yawn. Most mammals yawn. My dog yawns, but that doesn't make me yawn -- I obviously cannot put myself in her paw prints. (But who can empathize with a creature that sleeps all day, then when she does bother to get up and join you on a walk, suddenly bolts after a squirrel and nearly tears your arm out of your socket? I have no idea what's going on in that dog's mind.)\n\nChimpanzees yawn too, and in fact, if they watch other chimps yawn, they're more likely to yawn too.\n\nSo, I guess the real answer is: who knows?
462731
Cover your mouth if you want to, but it won't keep the next guy from "catching" your yawn.\nContagious yawning is real, scientists say, and it's "probably programmed into us," according to Dr. William Broughton, director of the Sleep Disorders Center at the University of South Alabama Knollwood Hospital.\n\nThe action of a mouth opening is not what compels others to yawn, Broughton said. Studies have demonstrated that showing someone a photo of a wide-open mouth does not induce a yawn.\n\nConversely, holding a hand over the mouth while yawning doesn't prevent it from being contagious, Broughton said.\n\nContagious yawns appear "basically to be a visual response," Broughton said.\n\nBetween 40 and 60 percent of people who watch videos or hear talk about yawning also end up doing the deed, according to Nature News Service.\n\nResearchers from the State University of New York in Albany tested people to find out why some are susceptible to contagious yawning and deduced that self-aware or empathetic people are more likely to catch yawns, according to the news service.\n\n"Identifying with another's state of mind while they yawn may trigger an unconscious impersonation....The findings also explain why schizophrenics, who have particular difficulty in doing this, rarely catch yawns," Nature News Service reported.\n\nBroughton said contagious yawning may be a social phenomenon, allowing groups of humans to coordinate their times of sleep.\n\nRonald Baenninger, a professor in the psychology department at Temple University in Pennsylvania, has studied yawning and said that the contagiousness is the part we know the least about.\n\nOne hypothesis is that the phenomenon came about when ancestral humans lived in troops, and it was important for them to wake up at the same time. Yawning may have been a way for them to communicate the level of alertness among different group members, Baenninger said.\n\nToday, contagious yawning is just the result of evolution, an instinctive action, Baenninger said.\n\nThough other creatures yawn - including dogs, cats and even snakes - contagious yawning is a "purely human occurrence," Broughton said. It begins around age 2.\n\nBaenninger and his students conducted a study to see if the contagion works between species. The students went to the zoo to observe whether humans would yawn when the animals did. A few people yawned in response to a lion's yawn, but the lion never replicated the humans' behavior, Baenninger said.\n\nThere is some evidence that when one ape yawns, others will too, the professor said.\n\nBroughton said it's not clear what causes yawns. He defined yawning as "slow, involuntary gaping movements of the mouth," and said the word is derived from the Old English word ganien, which means "to gape."\n\nSpontaneous yawning begins in the embryonic stage, so it is not learned behavior, Broughton said.\n\nThe idea of a fetus yawning while in the womb goes along with the notion of the action being a way to prepare for something, Baenninger said.\n\nYawning appears to be associated with sleepiness, though the idea that it has to do with boredom is not necessarily true, Broughton said. It's an unconscious effort to keep your alertness level elevated, Baenninger said.\n\n"I'm a professor. All professors are used to having students yawn at them," Baenninger said. But the yawns are an attempt to stay awake, rather than an affront, he said.\n\nA few notions about why we yawn have been debunked: "Because breathing takes in oxygen and removes carbon dioxide, theories in the past about why we yawn centered on the assumption that it was a reflex in response to low oxygen or high carbon dioxide levels," writes Dr. Robert H. Shmerling, an associate physician at Beth Israel Deaconess Medical Center and an associate professor at Harvard Medical School.\n\n"This theory lost favor
558756
As far as you should know yawning is contagious. Sorry I couldn't read that five-letter word you tried to put in it.
1002474
The yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.[2] The reasons for this are unclear; however, recent research suggests that yawning might be a herd instinct.[3] 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. This phenomenon has been observed among various primates. The threat gesture is a way of maintaining order in the primates' social structure. The contagion of yawning is interspecific (i.e., try yawning in front of your dog). 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".
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.
335882
It is a "associative" reaction. You see someone yawn and it triggers the same reaction because in our experience yawning represents being tired. We therefore associate yawning by others or ourself with being tired.\n\nI get a similar associative reaction when my daughters and I say the Lord's Prayer every night at bedtime. Halfway thru the prayer they will both yawn like clockwork. They both associate the prayer with being sleepy. Puts them right to sleep every time!
329034
We yawn because of a lack of Oxygen. Think about it: when you yawn more air comes in and sometimes after a yawn you feel rejuvenated for a little while. But this is contagious because if you yawn you are probably in an Oxygen-deprived environment and everyone around you is going through the same lack of Oxygen. And yawning is related to sleep because when you're asleep you're barely doing more than breathing, beating your heart and dreaming which doesn't take up much oxygen but you still get the same amount of oxygen as you would awake in the same room so there's more oxygen to relax your brain and mind and everything else that might be tired.
1159613
Ahhh... the age old question. lol\n\nThere are a number of theories. One is that when someone yawns, they take oxygen out of the air, and we need the oxygen so we yawn to get the oxygen we need. I'm not sure about that one. I think its just a joke.\n\nA more likely theory is that it relates back to the herd instinct. You know, monkey see, monkey do.
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...
313357
Every time you yawn a big cloud of microscopic yawnbots spread out from your mouth and are breathed in by those around you, infecting them and causing them to yawn too.
246554
Yes. The mere suggestion of yawning can induce a yawn in some people. (In fact I'm yawning right now from reading your question.) So if you sent an email saying "I'm yawning" to such a sensitive person, even if (s)he couldn't see or hear you that person could yawn.\nAlso, two people might yawn excessively if they shared an environment that is conducive to yawning, i.e., low in oxygen or high in carbon dioxide, but that wouldn't really be contagion.
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".