why is yawning contagious?
963394
Heere are excerpts from the source:\nIn 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. \n\nMirror neurons typically become active when a person consciously imitates an action of someone else, a process associated with learning. But they seem to play no role in yawn contagiousness, the researchers in the new study found. The cells are have no extra activity during contagious yawning compared with during other non-contagious facial movements, they observed.\n\nBrain activity “associated with viewing another person yawn seems to circumvent the essential parts of the MNS [mirror neuron system], in line with the nature of contagious yawns as automatically released behavioural acts—rather than truly imitated motor patterns that would require detailed action understanding,” wrote the researchers, with the Helsinki University of Technology and the Research Centre Jülich, Germany. The findings are published in the February issue of the research journal Neuroimage.\n\nBut if seeing someone yawn doesn’t activate these centers, what does it do to the brain? The researchers found that it appears to strongly activate at least one brain area, called the superior temporal sulcus. But this activation was unrelated to any desire to yawn in response, so it may be irrelevant to the contagion question, the researchers added.\n\nPossibly more significant, they wrote, was the apparent deactivation of a second brain area, called the left periamygdalar region. The more strongly a participant reported wanting to yawn in response to another person’s yawn, the stronger was this deactivation. \n\n“This finding represents the first known neurophysiological signature of perceived yawn contagiousness,” the researchers wrote.\n\nExactly what the finding means is less clear, they acknowledged. The periamygdalar region is a zone that lies alongside the amygdala, an almond-shaped structure deep in the brain in the area of the side of the head. The periamygdalar region has been linked to the unconscious analysis of emotional expressions in faces. Why it would be deactivated in tandem with yawn contagion is unclear, the researchers said.\nFurther details can be had from the site.\nVR
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.
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!
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.
41848
I have a theory on this to share.\nMay be yawning is not a chain reaction at all.\nIts just our reaction to the state of things, outside as well as inside our body.\nFor instance, we feel sleepy when our brains are tired or refuse to process. Result is that we all yawn when after a tired game, after a boring speech.\nMay be even when there is lack of sufficient oxygen.\nWe all have different reaction times though. Thats probably the reason why its being mistaken to be a chain reaction.
37416
I asked the same question KIND OF go to the website below and it gives you the answers to the most common myths. Yawning is included in one of them.
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".
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.
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.
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.
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.
404224
Yawning is not, technically, contagious... and this is the 363rd time this, or a similar question, has been asked.
198710
When you yawn, you are attempting to take in as much air as possible, more oxygen gives more energy.  People in the immediate area are in competition for this air too and yawn as a response to retrieve air themselves
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...
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.
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.
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.