Why and how are yanwns contagious?
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.'
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.
811887
its so funny i read your question and it made me yawn and made me wonder so i looked it up for ya\n\n\n\nThe yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.[3] The proximate cause for contagious yawning may lie with mirror neurons, i.e. neurons in the frontal cortex of certain vertebrates, which upon being exposed to a stimulus from conspecific (same species) and occasionally interspecific organisms, activates the same regions in the brain[4]. Mirror neurons have been proposed as a driving force for Imitation which lies at the root of much human learning, e.g. language acquisition. Yawning may be an offshoot of the same imitative impulse. At a distal level (in terms of evolutionary advantage), yawning might be a herd instinct.[5] 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, for example a human yawning in front of a pet dog can incite the dog to yawn as well. 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.
857869
They probably think it's contagious. LOL.  Who knows?  But it's pretty stupid the way people act about it.
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.
56869
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."
659397
Contagious in the normal sense - no.  If, however, someone else touches the part that still has the sap on it then it can get passed on.  This is a contact type of problem - no contact, no problem.
873121
NOPE !!!\n\nIT'S MORE SERIOUS THAN THAT !!!\n\nIT CONSISTS OF MENTAL DISORDERS !!!\n\nAND IT IS SOMETHING YOU CAN NOT INDUCE UPON YOURSELF NOR IS IT CONTAGIOUS !!!
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.
1005855
(1)"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.\n\nStudies partially explain the reason for yawning. Although we yawn more when sleepy or bored, it is unclear whether yawning increases alertness. And scientific evidence refutes one of the most popular myths of yawning? that it happens in response to low oxygen or high carbon dioxide levels in the blood or brain. Test subjects do not yawn more when breathing air with enhanced levels of carbon dioxide nor do they yawn less when breathing pure oxygen. One fact explains a lot of apparently inconsistent data. People yawn most during behavioral transitions, such as just after waking and shortly before bedtime. Yawning may help facilitate those changes. Contagious yawning may synchronize a group's behavior so that, for instance, a whole family goes to sleep together."\n\n(2)  "Professor Andrews told Scientific American yawns may be contagious because we human animals are trying to communicate changing environmental conditions to others, possibly as a way to synchronize behavior. Obviously, this would be one of those caveman-type mechanisms that is no longer needed that our bodies remember and still do.\n\nWhen we yawn, we draw in more oxygen and remove a build-up of carbon dioxide. Larger groups produce more carbon dioxide. So one theory holds that we yawn when we're in large groups of people to purge the carbon dioxide--and in so doing, we set off a chain reaction. But Robert Provine, a psychologist at the University of Maryland, Baltimore County, tested the theory and says it's bunk. Giving people additional oxygen didn't decrease yawning and decreasing the amount of carbon dioxide in a subject's environment also didn't prevent yawning, notes the How Stuff Works Web site.\n\nWhatever the reason for yawns being contagious, How Stuff Works reports that 55 percent of people will yawn within five minutes of seeing someone else yawn. In addition, blind people will yawn after hearing others yawning. And we're sure that reading and writing about yawns is enough to induce one!"
295331
Contagious is the wrong word. \nBut they are a suggestion, almost hypnotic, to yawn.\nAs is the word "itch", just the talk of creepy crawlies and itches is enough to start you itching somewhere on your body.\nHope this helps
962189
Basically it spreads from contact.  Most of the time from touching something someone who had this touched and then touching your own eye.
239646
It's contagious to only those with an empathetic mind. Not everyone has one, so not everyone is going to yawn if someone else does.\n\nDon't listen to that Brisbane Roo character--he's full of it. It's true what he said about periods, but that has nothing to do with yawning.
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.
859228
I don't know if contagious is the right word.  I do know that in some studies that were done in college dormitories, girls that live together/spend a lot of time together tend to have their periods adjusted, to the point where they literally have the same cycle! they found that in some situations the hormone changes in one triggers the hormone changes in another.
216325
No.  It is very contagious.
766538
Yawning individuals are exposed to the same atmospheric oxygen concentration this could fall marginally to set off the masseteric reflex to pump more blood to the brain from within the masseter muscles,so when this happens it appears to be contagious.