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1 mai 2010
French doctor seeks to unravel mystery of the yawn
Vicky Buffery


PARIS, April 28 (Reuters Life!) - We do it when we're tired, when we're bored or when we're hungry; parachutists have been seen to do it before a jump, and research has even suggested a link between yawning and sexual arousal.
But the exact causes and function of yawning remain a mystery, and one that until recently was surprisingly under-documented in the scientific world.
Now a French family doctor, Olivier Walusinski, has published what is billed as the first ever textbook on the subject, "The Mystery of Yawning in Physiology and Disease" a collection of the latest research on this baffling and uncontrollable behaviour.
The book will be followed up on June 24-25 with the First International Conference on Yawning in Paris, which will address issues such as the role of yawning as a brain-cooling mechanism and the hidden sexuality of the yawn.
"There are a number of theories, but there's no formal proof as yet of why we yawn," Walusinski told Reuters.
What is known is that the average human will yawn around 250,000 times over the course of his life, and that babies in the womb do it from as early as 12-14 weeks, suggesting it plays an important neurophysiological role.
"If a foetus weighing just 60 g (2.116 oz) can expend the amount of energy needed to yawn and stretch, then it must be absolutely vital to its development," Walusinski said.
Birds do it, fish do it, in fact nearly all cold and warm-blooded vertebrates do it, with the exception of giraffes and whales which have not yet been caught gaping involuntarily. In humans, yawning is still widely believed to increase oxygen levels in the blood and eliminate excess carbon dioxide, but this theory was ruled out as far back as the 1980s.
"The idea dates back to the 17th century, but studies by the American Robert Provine... showed that the concentrations of gases in the blood remained exactly the same before and after yawning," said Walusinski.
Instead, the fact we yawn when we're sleepy or bored has led recent research to suggest it is used to increase vigilance.
Yawning when hungry is thought to support this theory although, unlike lions and other carnivores, humans no longer need heightened instincts to hunt down their prey.
As for why parachutists yawn before a death-defying jump, this again could be to increase vigilance, but there is also speculation it could help counter a rise in stress.
Rats subjected to stressful stimuli in cages have certainly been found to yawn more frequently, however exactly what function their mouth gaping serves has yet to be shown.
Another theory is that yawning helps to cool the brain, protecting cerebral activity and boosting efficiency.
But before you use this excuse in the next boring meeting, it's worth noting that the idea raises a number of questions, such as why we don't yawn more during a fever, and why snakes yawn when they have no temperature regulating mechanism.
What is certain is that yawning is catching, Walusinski said, and this has been linked to empathy in humans.
Neuroimagery has shown the same parts of the brain light up when we feel empathy as when we "catch" a yawn, while personality tests have shown people with schizophrenia or autism are less likely to be affected.
A Dutch researcher has also suggested a link between yawning and sexuality in humans, based on circumstantial evidence such as representations of yawning in literature and the visual arts.
Popular imagery, for example, frequently shows a gaping mouth, stretching and thrusting out of the chest as an erotic posture in women, supporting the idea that yawning has a sexual side and could indeed be an invitation to sex.
In animals, Walusinski noted, the link is far more obvious.
"In macaque monkeys, the dominant male yawns before and after mating, and this is testosterone-dependent," said Walusinski.
Castration, he said, causes the male to lose his dominant status, and the yawning stops. (Editing by Paul Casciato)

1°) (NT) I am a retired journalist living in New Zealand. I have just read of your book on yawning and the forthcoming international conference on this subject, which has long interested me as an amateur.
I am not an expert, but one thing I have noticed from practical observation is that when I yawn repeatedly during daytime, the way to stop it is to drink water. I am sure there are multiple causes for yawning, but I suggest that possibly thirst (or need for liquid) is one.
During my working career I have often been in meetings where people have yawned and then said: "I'm sorry - that's strange, I had plenty of sleep last night and I'm not tired or bored, so I don't know why I'm yawning". I have then suggested that they drink a glass of water, and it usually works immediately. Sometimes they say "But I've just had a cup of coffee!", and I say "No, your body wants water, not coffee". So they drink water, and stop yawning. The water needs to be cool, i.e. natural.
I do not discount the possibility that there may be a psychological factor in this - that the subject stops yawning after drinking water because he/she BELIEVES this will stop the yawning. Or perhaps it is due to a cooling of the respiratory organs rather than due to the intake of liquid. All I know is that it seems to work with me, and with toal strangers whom I give this advice to.
2°) (DK) I have read some of your conclusions regarding yawning in  However, it seems obvious to me that yawning stretches out the facial muscles and causes it to relax.  This is much like stretching any other part of your body.  You do this before sleep to help you relax and prepare for sleep.  Apolo Ohno, US speed skater, yawns before each race in order to relieve tension and calm his nerves.  As another example, there exists a relaxation technique of pressing your tongue hard against the roof of your mouth for 10 seconds or so, and then releasing.  Some people use this technique to relax at bedtime and to prepare for sleep.  This again releases tension and causes your face to relax.  There are so many muscles in your face, that if you can relax your face, your entire body will relax.  You can also hold other muscles in your body - in your arms and legs, for example - tense for several seconds, and then release them to relax the muscles and to prepare for sleep.  Many people will stretch their arms as they yawn.

Un médico francés trata de develar el misterio del bostezo
28 de abril de 2010 • 09:19
Por Vicky Buffery
PARIS (Reuters) - Lo hacemos cuando estamos cansados, cuando estamos aburridos o cuando tenemos hambre; hasta los paracaidistas tienden a hacerlo antes de saltar. Ahora, un nuevo estudio sugirió un posible vínculo entre el bostezo y la estimulación sexual.
Sin embargo, las causas exactas y la función del bostezo siguen siendo un misterio, y, hasta hace poco, había sido escasamente documentado en el mundo científico.
Un médico de familia francés, Olivier Walusinski, publicó lo que algunos han proclamado como el primer libro de texto sobre la materia, 'The Mystery of Yawning in Physiology and Disease', una colección de los últimos hallazgos sobre este desconcertante e incontrolable comportamiento.
El libro será tratado el 24 y 25 de junio en la Primera Conferencia Internacional sobre el Bostezo en París, que abordará, entre otras cosas, su papel como mecanismo que enfría el cerebro y su sexualidad oculta.
'Hay varias teorías, pero no hay una prueba formal hasta ahora de por qué bostezamos', dijo Walusinski a Reuters.
Lo que se sabe es que el humano medio bostezará unas 250.000 veces a lo largo de su vida y que los bebés en el útero lo hacen ya en la semana 12 a 14 de gestación, lo que sugiere que juega un importante papel neurofisiológico.
'Si un feto que pesa sólo 60 gramos puede gastar la cantidad de energía necesaria para bostezar y estirarse, debe ser algo absolutamente vital para su desarrollo', dijo Walusinski.
Los pájaros lo hacen, los peces también, de hecho, casi todos los vertebrados de sangre fría y caliente lo hacen, con excepción de las jirafas y las ballenas, que no han sido captadas aún abriendo la boca involuntariamente.
En los humanos, el bostezo aún se considera una forma de incrementar los niveles de oxígeno en la sangre y eliminar el exceso de dióxido de carbono, aunque esta teoría fue descartada ya en la década de 1980.
En su lugar, el hecho de que bostecemos cuando tenemos sueño o estamos aburridos ha llevado a recientes investigaciones a sugerir que se utiliza para aumentar la vigilia.
Se supone que bostezar cuando tenemos hambre respalda esta teoría aunque, a diferencia de los leones y otros carnívoros, los humanos ya no necesitamos tener los instintos alerta para cazar una presa.
En cuanto a por qué los paracaidistas lo hacen antes de saltar, también se cree que podría estar relacionado con un estado de alerta. Pero además se especula con que puede ayudar a contrarrestar un aumento del estrés.
Lo que es seguro es que es contagioso, dijo Walusinski, y esto se ha vinculado a la empatía en los humanos.
Un investigador holandés también sugirió un vínculo entre el bostezo y la sexualidad en los humanos, basándose en pruebas circunstanciales, como representaciones de bostezos en la literatura y artes visuales.
En los animales, subrayó Walusinski, la relación es mucho más obvia.
'En los macacos, el macho dominante bosteza antes y después de aparearse, y esto está condicionado por la testosterona', dijo Walusinski.
La castración, declaró, lleva a que el macho pierda su estatus dominante, con lo cual se acaba el bostezo.
(Traducido por la Redacción de Madrid)