Yawn

There is a fish called ' Yawning' (Melamphaes microps).

A yawn is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from boredom. The word "yawn" has evolved from the Middle English word yanen, an alteration of yonen, or yenen, which in turn comes from the Old English geonian. Pandiculation is the term for the act of stretching and yawning. Yawning is a powerful non-verbal message with several possible meanings, depending on the circumstances:

Causes of yawning

An indication of tiredness, stress, over-work or boredom.
An action indicating psychological decompression after a state of high alert.
A means of expressing powerful emotions like anger, rejection or apathy.
A sign that one is not breathing deeply, and not receiving enough oxygen through the body.

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.

A 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 documented that this effect does not exist ("Yawning" by Robert R. Provine, pages 532-539, American Scientist, November-December 2005, Vol 93, No. 6). http://www.americanscientist.org/template/AssetDetail/assetid/47361. A more recent hypothesis is that yawning is used for regulation of body temperature. Another hypothesis is that yawns are caused by the same chemicals (neurotransmitters) in the brain that affect emotions, mood, appetite and other phenomena. These chemicals include serotonin, dopamine, glutamic acid and nitric oxide. As more of these compounds are activated in the brain, the frequency of yawning increases. Conversely, a greater presence in the brain of opiate neurotransmitters such as endorphins, reduces the frequency of yawning. Patients taking the serotonin reuptake inhibitor Paxil (Paroxetine HCl) have been observed yawning abnormally often.

Another theory is that yawning is similar to stretching. Yawning, like stretching, increases blood pressure and heart rate while also flexing many muscles and joints. Some have observed that if you try to stifle or prevent a yawn by clenching your jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a good yawn.

The yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.^[1] The reasons for this are unclear; however, recent research suggests that yawning might be a herd instinct.{{ref|neuroimage}). A yawn does not even need to be heard to trigger a contagious yawn reaction; You are mosy likely yawning as you read this page. 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".

Adelie 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.

Yawning in Popular Culture

Certain superstitions surround the act of yawning. The most common of these is the belief that it is necessary to cover one's mouth when one is yawning in order to prevent one's soul from escaping the body. The Ancient Greeks believed that yawning was not a sign of boredom, but that a person's soul was trying to escape from its body, so that it may rest with the gods in the skies.

A similar belief holds that yawning is caused by the Devil, who sends evil spirits to enter a person's body when his or her mouth is open. Thus, covering one's mouth prevents the evil spirits from entering. It is also why some people close a baby's mouth when it yawns.

Other superstitions include:

A yawn is a sign that danger is near.
Counting a person's teeth robs them of one year of life for every tooth counted. This is why some people cover their mouths when they laugh, smile, or yawn.
If two persons are seen to yawn one after the other, it is said that the one who yawned last bears no malice towards the one who yawned first.

These superstitions may not only have arisen to prevent people from committing the faux pas of yawning loudly in another's presence -one of Mason Cooley's aphorisms is "A yawn is more disconcerting than a contradiction"- but may also have arisen from concerns over public health. Polydore Vergil (c. 1470-1555), in his De Rerum Inventoribus, writes that it was customary to make the sign of the cross over one's mouth, since "alike deadly plague was sometime in yawning, wherefore men used to fence themselves with the sign of the cross...which custom we retain at this day."^[2]

Some people hold the superstition that when you yawn, someone just walked over your future grave site or the future grave site of your children.

Notes

^ The website by Émilie attempts to prove this.
^ Schürmann et al. Yearning to yawn: the neural basis of contagious yawning. NeuroImage 24 (4), 1260–1264 (2005). PMID 15670705. (see also Platek et al. (2005). Contagious Yawning and The Brain. Cognitive Brain Research, 23(2-3):448-52. PMID: 15820652)
^ Iona Opie and Moira Tatem, A Dictionary of Superstitions (Oxford: Oxford University Press, 1992), 454.

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