Why do tears come in the eyes of a person who has yawned?
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When you yawn, you compress your tear sacs  or lacrimal glands which secretes the tears
792582
A yawn is in response to too much CO2 in the blood stream.  When you yawn there is a negative feed back loop in operation which tells the diaphram to contract (take a breath) because there is too much CO2......the yawn actually increases CO2.\nThe sneeze is due to irritation in the beginning of the respiratory tract, it expells such things as dust, bacteria and other irritants from your nose and sinuses.\nA hiccup is a sligh malfunction or mistiming if you will of the glottis which is a membrane that closes in your throat to prevent food from going into your lungs when you swallow.  Whenyou ge tthe hiccups it starts to close while you are taking a breath or expelling a breath.  It just takes a bit of time for your body to reset when it closes
55666
I saw something on this before..it said that if you yawn when other people yawn..your a sympathetic person.  In my observing this..I've noticed it's kind of true..particularly..there is a guy that I work with who NEVER yawns when he is around other people who are yawning.  He is not a very sympathetic person at all about anything..kind of rude..or short..I don't know..not very people friendly.  However my friend and I at work are very sympathetic..and we always yawn at the other's yawn! :)
636140
Crying or weeping: Is increased lacrimation due to strong emotional stress or pain. This practice is not restricted to negative emotions; many people have been known to cry when extremely happy. In humans, emotional tears can be accompanied by reddening of the face and sobbing — cough-like, convulsive breathing, sometimes involving spasms of the whole upper body. Tears brought about by emotions have a different chemical make up than those for lubrication. \n\n\nSome claim that humour cannot or should not be explained. Author E. B. White once said that "Humor can be dissected as a frog can, but the thing dies in the process and the innards are discouraging to any but the pure scientific mind." However, attempts to do just that have been made, as follow.
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To begin with, something upsetting has happened to bring you to the point of tears.  This in itself is stressful.  Stress and tension break down the ammune system and can lead to illness over time.  So, when you cry, and I mean really sob, your body is releasing stress, sadness, perhaps anger, and all around tension.  It isn't just the crying that is tiring, it is the emotional drainage.  Did you know it takes more muscles to frown than to smile?  I've cried quite a bit, I'm kind of an expert, tee hee.
27456
i used to cry in one i too sometimes.....i think its normal maybe the other eye is just slow in secreting tears.....
476267
I have no idea, but it happens every time I yawn LOL. I have seen people do it intentionally though.
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.
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Yawning is one of those bodily mysteries that scientists haven't completely figured out yet.  The best theory I could find was that you yawn because you're not getting enough oxygen to the brain (maybe there is a lack of oxygen in the space you're standing).  Whenever you're aware of someone yawning, it activates a reaction in your subconscious mind that acts as a threat response.  Basically, whenever you see someone yawn, it makes you body think there is a shortage of oxygen too, and you yawn in response.  No one knows if this is actually the case, but I think that it is a good theory.
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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
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its neurogical response to ur inner state of mind. when u are happy or sad the nerves get activated as a result of which ur tear glands activates and hence the tears.
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Yawns are contagious because people naturally emulate what they see others doing. For more, read a section in the Tipping Point by Malcom Gladwell.
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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. This is sometimes referred to as "following the herd." Such people are sometimes labelled with the derogatory term "sheeple."\n\nSince the herding instinct includes both behavior and belief, the term 'herd behavior' describes only a part of this complex phenomenon in humans.
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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".
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Eye boogers are dried tears.  Tears have a great deal of salt and protein in them (think about how you have to clean contact lenses), so when the water evaporates as you sleep without blinking to clear the tears down your ducts, it leaves behind the salt and protein.
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A yawn is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from boredom.\n\nYawning is a powerful non-verbal message with several possible meanings, depending on the circumstances. It is also claimed to help increase the state of alertness of a person.\n\nCauses of yawning:\n1. An indication of tiredness, stress, over-work or boredom. \n2. An action indicating psychological decompression after a state of high alert. \n3. A means of expressing powerful emotions like anger, rejection or apathy. \n4. A sign that one is not breathing deeply, and not receiving enough oxygen through the body. \n5. A yawn can express strong anti-social messages, and so in some cultures people try to mute or mask them by placing a concealing hand over the yawning mouth.\n\nA long-standing hypothesis is that yawning is caused by an excess of carbon dioxide and lack of oxygen in the blood. The brain stem detects this and triggers the yawn reflex. The mouth stretches wide and the lungs inhale deeply, bringing oxygen into the lungs and hence to the bloodstream
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This is science.\n\nWhen you yawn, it is because your brain lacks oxygen and need to get more oxygen. This is done by yawning where you inhale deeply to take in more air and oxygen. \n\nWhat you mentioned is especially true, especially in crowded places or enclosed palces.\n\nWhen you yawn, you take in large amount of air from the surrounding, depriving the other of the oxygen. Thus, the others will need more oxygen too. So, they yawn to take in more air. And when they yawn, they take in even more air from the surrounding and the others will have to yawn to get sufficient oxygen.\n\nOne yawn will spark off a chain reaction of yawning.\n\nUnderstand now?