What is the function/purpose of a yawn and why is it contagious?
365189
The popular theory is that yawning is for oxygen boosting/carbon dioxine expulsion. Hwoever, this is contended, see http://en.wikipedia.org/wiki/Yawning for some other theories.\nThe fact that it is contagious is far more interesting though.\nThere were theories that it was related to the environment being the same, or even an exchange of chemicals. However, there is more debate now, as if you have a video conversation with someone on a webcam: same thing happens. You could be on different sides of the world, at different times of day, and you're still both yawning.\nAnother theory is that it's a subconscious psychological effect. You see someone yawning, and your subconscious thinks that it would rather like to do that, Interestingly, I have yawned quite a lot whilst I've been writing this, and I'm not tired at all.\nThere's a similar question to yours here http://www.straightdope.com/classics/a2_309.html\nBut the truth is, no-one really knows the answer.
255818
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".
337591
because yawns are catching and a yawn is when you are tired and need a hugeee gulp of air so of course if someone in your group has yawned and inhaled alll the air then you nearly suffocate cause you've got no air so you have to yawn to try get some air before you collapse. so blame you friends for snatching the air from your lungs making you yawn !!!!!!!!!!!!!!!!!!!!
64755
Personally, I think it's a sub-conscience action since you don't have to be aware of someone else yawning. Think of it this way, you weren't hungry until you saw, smelled, or someone mentioned food. So as you idle your body equates lack of action as rest. As we all know, rest is equated to sleep, so your idle body wasn't tired until someone yawned. \n\nI know it sounds odd but, have you ever yawned while your cardio system was working harder than compared to sitting idle?
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.
346467
Yawns are not contagious, its an urban legend. Watch 'Mythbusters' on the Discovery channel.
249771
Compounding the mystery is the odd way in which the contagious power of yawning is largely unconscious. We can see someone yawn, yearn to replicate the action ourselves, and do it, all without thinking about it. Other times we’re aware it is happening, though it still floats somewhere beneath the realm of reason and of purposeful actions.\n\nSo what gives? In an effort to find the answer, the Finnish government recently funded a brain scanning study. The results turned up some hard-to-interpret, possible clues. It also confirmed the obvious: 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.
123342
This might help\n\nhttp://www.world-science.net/exclusives/050309_yawnfrm.htm
17567
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.
445199
This is one of the best responses that I have seen in the questions that I have read regarding yawning.  Those you opine that there is nothing but the physical automatically exclude themselves from understanding so much about life.\nOne of the functions of yawning is to release energy from the back of the head, or occipital region.  The entire body has negative and positive polarized areas, and the negative areas allow for release of energy that comes in through the positive receptor locations.  Major positive areas are the head and heart.  Major negative areas are the jaw, the pelvis and the feet.  Negative does not mean "bad", just that it is a place where spent energy is released.  The phenomenon of "catching" a yawn is in my own observation, related to the matching of energy by individuals.  Whatever is heing matched in terms of thoughts and feelings cycles or releases itself from the back of the head.  The explanations given by brianarnold12 are also good, as there are various nuances and dimensions dealt with.  Understanding the importance of matching energy, and understanding the value of release are major spiritual steps! :0)
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.
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!
414199
Yawning, like laughter, can be infectious. As to why this should be, there is little hard evidence, although yawning may be an arousal response that arose early in evolution and whose aim is to improve oxygenation of brain tissue and increase alertness, with a view to enhanced survival. In social groupings, the sight of one member yawning might act as a signal to cause other members to yawn - in some way the yawn is a warning that attention is slipping and the group may be at risk…\n\nResearch into the physiology and pathology of yawning appears to be quite limited. However, I have come across a couple of useful references. The first gives a general description of what happens when we yawn:\n\n"Yawning is a response to a wide variety of stimuli, including sleepiness and an awakening from sleep, hunger, boredom, nervousness, and intracranial disease. It is infectious, occurs more frequently in the newborn, and is likely to be more vigorous (especially the accompanying stretch) in early morning than late at night."\n\n"A yawn consists of an expansion of the chest, descent of the diaphragm and larynx, elevation of the ala nasi and soft palate, downward and backward movement of the tongue, abduction of the vocal cords, wide opening of the mouth, contraction of the tensor veli palatini muscle, closing of the eyes, lacrimation, pulling the head backwards, stretching of the upper arms sideward and the lower arms upward, and, less frequently, stretching of the legs. Vasoconstriction in the digits and cardiac acceleration have also been found to accompany the yawn. The whole act occupies 5 to 10 seconds, most of which time is spent in the inspiratory phase."\n\n"Although yawning certainly is an effective way of fully expanding the lungs and increasing the venous return to the heart, its psychic implications are also of great interest. The author finds that merely writing this is a potent stimulus towards yawning, and perhaps the reader is similarly stimulated." (Fenn and Rahn 1964)\n\nA good review of yawning is provided by Askenasy (1989), and the points that follow are derived from this source. Apparently, yawning movements have been observed in fetuses as early as the 15th week after conception, and continue to occur sporadically throughout the remainder of pregnancy. The newborn baby yawns a few minutes after birth. The frequency of yawning gradually diminishes as the baby matures\n\n\nSeveral causes of yawning are discussed in the review:\n\n psychological - this includes boredom, drowsiness, fatigue, separation, imitation, and autosuggestion \n\n hormonal - ACTH and MSH \n\n neurological - various brain pathologies including coma, encephalitis, hypoxia, and neoplasms \n\n psychiatric - for example schizophrenia, psychosis, depression and withdrawal \n\n general pathologies - ear disorders, gastric and biliary disorders, and motion sickness \n\n drug overdose - for example naloxone, valproate, imipramine, clomipramine, seratonin, and pentobarbital \n\n drug withdrawal - from heroin, morphine, lefetamine, methadone, and pentazocin.
635799
1. because your body needs oxygen\n2. becaus you are bored and it is a way for your body to tell you to do something else\n3. becaus other people yawn. it is a social behavior that makes a group "stay together" \n\nhow? not sure, but I think your brain open your mouth and make your lungs draw in lots of air without letting you know first.
321997
Cause when you yawn, you are thought to release carbon dioxide, and when somebody else gets the carbon dioxide, then they have to release it.  Another theory is, a long time ago when humans first existed, it meant it was time to go to sleep, so everyone would know toy go to sleep.  Isn't that so cute?  ^.^
977252
From Wikipedia:\n\n"A previous 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. It is almost certain, however, that this hypothesis is not correct. One study has documented that this effect does not exist."\n\nGoes on to newer, updated theories.\n\nAlso:\n\n"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."\n\nGoes on to give other reasons for contagion. <Yawn!> Enough!
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.