Yawn

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For other uses, see Yawn (disambiguation).
A dog yawning
A dog yawning

A yawn (synonyms chasma, oscitation from the Latin verb oscitare, to open the mouth wide[1]) is a reflex of deep inhalation and exhalation associated with being tired, with a need to sleep, or from lack of stimulation. 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. It is also claimed to help increase the state of alertness of a person. It could possibly be from lack of oxygen. The exact causes of yawning are still unknown.

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[edit] Origin of the word

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.

[edit] Hypothesized causes of yawning

  1. An indication of tiredness, stress, over-work, lack of directed attention or boredom.
  2. An action indicating psychological decompression after a state of high alert.
  3. A means of expressing powerful emotions like anger, apathy, apprehension, remorse or tedium.
A cat yawning
A cat yawning

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 incorrect. One study has documented that this effect does not exist.[2]

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. Stretching, like yawning, increases blood pressure and heart rate while also flexing many muscles and joints. It is also theorized that yawning helps redistribute an oil-like substance which coats the lungs and aids breathing. Some have observed that if one tries to stifle or prevent a yawn by clenching one's jaws shut, the yawn is unsatisfying. As such, the stretching of jaw and face muscles seems to be necessary for a satisfactory yawn.

Yet another theory is that yawning occurs to stabilize pressure on either side of the ear drums. The deep intake of air can sometimes cause a popping sound that only the yawner can hear; this is the pressure on the inner ear stabilizing. This commonly occurs in environments where pressure is changing relatively rapidly, such as inside an airplane and when travelling up and down hills, which cause the eardrums to be bent instead of flat.

Some movements in psychotherapy such as Re-evaluation Counseling or co-counselling believe that yawning, along with laughter and crying, are means of "discharging" painful emotion, and therefore can be encouraged in order to promote physical and emotional healing.

[edit] Contagiousness

The yawn reflex is often described as contagious: if one person yawns, this will cause another person to "sympathetically" yawn.[3] Mythbusters attempted an experiment documenting this effect in episode 2.28, "Is Yawning Contagious?", with a conclusion of partly confirmed. 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.[citation needed]

[edit] Injuries

Injuries can occur from excessive or mal-positioned yawning.

In the typical case, a bored person may experience a yawn whilst their jaw is resting on their hand, which in turn is resting on a desk. The pressure of the head's weight resting on the hand creates an opposing force on the jaw joint, which is in its weakest state when wide open, thereby pushing the joint out of position and straining the ligaments and cartilage. This can result in sharp pain lasting days, stiffness of the jaw, pain when chewing and, ironically, painful yawning.

[edit] Trivia

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. This trait has also been seen among Emperor Penguins. Researchers have been attempting to discover why these two different species share this trait, despite not sharing a habitat.[citation needed]

In about 5% of patients, the antidepressant drug Clomipramine can cause inadvertent orgasms when yawning.[6]

In captivity, the Leopard Gecko has been observed "yawning". Whether this is akin to human yawning has not been confirmed.

[edit] Superstitions

Joseph Ducreux yawning; self-portrait ca 1783
Joseph Ducreux yawning; self-portrait ca 1783

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. This belief was also shared by the Maya.[citation needed]

Some say that yawning is caused by the Devil, who sends evil spirits to enter a person's body when their 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.[citation needed]

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.
  • If you don't cover your mouth while yawning, then the devil will come and rob your soul (Estonia).
  • In some Latin American and east Asian countries yawning is said to be caused by someone else talking about you.
  • A yawn may be a sign that one is afflicted by the evil eye (Greece).

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."[7]

Others hold the superstition that when a person yawns, someone just walked over that person's future grave site or the future grave site of his or her children.


[edit] Notes and references

  1. ^ A. Price Heusner. YAWNING AND ASSOCIATED PHENOMENA. Physiological Review 1946: 25; 156-168. Online pdf-version
  2. ^ "Yawning" by Robert R. Provine, pages 532-539, American Scientist, November-December 2005, Vol 93, No. 6 [1]
  3. ^ The website by Émilie attempts to prove this.
  4. ^ V.S. Ramachandran, Mirror Neurons and imitation learning as the driving force behind "the great leap forward" in human evolution. Retrieved on November 16, 2006.
  5. ^ 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)
  6. ^ "Yin, Yang and Yawn" - Snopes article on Clomipramine
  7. ^ Iona Opie and Moira Tatem, A Dictionary of Superstitions (Oxford: Oxford University Press, 1992), 454.

[edit] External links

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