yawning

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Yawning ( self-portrait by Joseph Ducreux , ca.1783)
Yawning Abyssinian tomcat
Yawning fish

The yawning (lat. Oscitatio ) is occurring in animals and humans reflexive behavior. It is often related to fatigue . The process begins with a deep breath, in the course of which the mouth is opened wide, and ends with closing the mouth while exhaling. The possible vocalization can be suppressed.

Since yawning is a sign of tiredness or boredom in western culture , the yawning person is expected to make concealing gestures. So it is common to turn away when yawning or to put a hand over your mouth. Sometimes the recommendation is even given to suppress it completely.

The cause and purpose of the yawning are not clearly understood. In fish that often yawn, it could be used to draw new water into the (paired) nasal cavity , i.e. to check the environment for odorous substances . The science of yawning is called chasmology .

Word history, ethnology

Yawning is derived from the Middle High German genen or ginen , which goes back to the Old High German ginēn ("open your mouth, yawn"): in the beginning of everything there was fire and water. Light and fog formed the chaos of Ginungagap . In the oldest surviving German language, Ginungagap is the "gaping snarling" ( gin : "throat"), still recognizable today in words such as "yawn" and "begin". All words belonging to the Germanic word group come from the Indo-European root ĝhē- (“yawn”, “gape”), which originally imitated the yawning sound. Also related are the Greek cháskein , also in the form of the suffix -chásma , ("gaping opening"), cháos ("empty space, air space, gap"). This root can also be recognized in the English “yawning”, which comes from the old English ganien or ginian , and in the Dutch “gapen”. In Latin, hiare (and Inchoativum hiscere ) only means "to gape", also to "open your mouth, gape"; oscitare stands for "yawn" (from sleepiness, boredom) .

In Greek mythology , chaos arose from the yawning Nyx , and it was believed that the soul wanted to break out of the body when yawning and ascend to the gods in Olympus. A similar belief was shared by the Maya . According to a Celtic legend, the hero Assipattle can defeat the dragon by letting a wave of water wash him down through the yawning mouth into the dark gullet of the monster.

In the Middle Ages, too, yawning was associated with belief in demons and devils - people were afraid that they could penetrate the body through the open mouth or the soul could escape from the body. The habit of covering one's mouth with one's hand stems from this period.

Other assumptions about the origin of this custom are more profane: in earlier times the teeth were often in a bad condition and therefore unsightly to look at. Since it was not common to brush your teeth, bad breath may also be more common.

Della Casa wrote in his "Education Book " Galateo in the middle of the 16th century :

“I have often heard scholars say that 'yawn' in Latin means 'idle' or 'idle'. So avoid this bad habit that offends the ear, eyes and good taste; after all, yawning not only shows that we are not favored by the society present, but it also casts a bad light on ourselves. It looks like we're drowsy and tired of spirit, which doesn't exactly make us kind to those we deal with. "

In other cultures, too, rules of behavior for yawning exist and have been. The Japanese Yamamoto Tsunetomo wrote around 1715 in his code of honor for samurai :

“It is improper to yawn in the presence of others. If you get an unexpected yawn, rub your forehead upwards with your hand, which is usually enough to stifle a yawn. If that doesn't work, hide the yawning from others by licking your tightly closed lips with the tip of your tongue, hiding your yawn behind your sleeve or hand, etc. The same goes for sneezing. Yawning and sneezing usually make you look foolish "

According to the philosophy of yoga , one of the five subsidiary pranas , called devadatta , causes yawning.

In 1768, Simon-Auguste Tissot warned in his advice book On the Health of Scholars for "people who sit and study a lot" against the "effect of drinks on the scholar's body", especially against excessive consumption of tea, as it is "very strong and I have seen healthy men to whom several cups of tea, drunk sober, caused stupidity, yawning, resentment, [...] "

Schopenhauer commented on yawning in 1850:

“Yawning is one of the reflex movements. I suspect that its more distant cause is a momentary depotentiation of the brain brought about by boredom, lethargy or drowsiness, over which the spinal cord is now overweight and now causes that strange spasm by its own means. On the other hand, stretching the limbs at the same time as yawning can no longer be counted as part of the reflex movements, although it occurs unintentionally but remains subject to arbitrariness. I believe that just as yawning ultimately arises from a deficit in sensitivity, so stretching arises from an accumulated, momentary excess of irritability, which one tries to get rid of. Accordingly, it only occurs in periods of strength, not in those of weakness. "

Video clip of a yawning fetus after 30 weeks of pregnancy in 4D ultrasound

In almost all cultures there have been or exist superstitions related to yawning.

  • "Yawning during childbirth is fatal, just as sneezing after coitus causes an abortion." (Gaius Plinius Secundus)
  • "If you yawn at the end of the year, it is widely believed that this is definitely a good omen for the coming year."
  • “When yawning there is danger on the way” (England).
  • “If you don't cover your mouth while yawning, the devil can steal your soul” (Estonia).
  • In some Latin American countries, Asia and Central Africa you think others think of you when you have to yawn (see sneezing !).
  • “Anyone who has to yawn is exposed to the evil eye ” (Greece).

In 1942 the American Joseph Moore was the first to publish on experiments on yawning. With his experiments he had looked for visual and auditory stimuli that trigger yawning. It was a revolution then to conduct experiments under controlled conditions. Trained students yawned “controlled” during lectures, church services and in the reading room of a library. The most common yawning was during the morning prayer. Moore also made subjects see or hear a yawn. Methodologically, his series of experiments had many weaknesses - for example, there was no control group . Their strength lies mainly in their quantitative approach.

For example, recent work on the meaning and cause of yawning comes from Robert Provine , a US neuropsychologist who also deals with laughter .

Yawning in animals

Yawning lion

Most mammals, but probably all vertebrates , are likely to yawn. Charles Darwin mentions in his book The Expression of Emotions in Humans and Animals that baboons yawn to threaten their enemies. Baenninger interprets the behavior of the male Siamese fighting fish in a similar way when they see an opponent or their reflection. On the other hand, opening your mouth wide (to threaten) does not have to have anything to do with yawning, as with the hippopotamus .

Konrad Lorenz still claimed in 1963 that birds and reptiles don't yawn. This opinion can be considered refuted, since South African ostriches were observed yawning as early as 1967 , and since then other birds such as the Adelie penguins have also been observed frequently . For them, yawning is part of their welcoming ceremony. A yawn-like behavior can also be observed in snakes . After the prey is completely devoured, the snake "sorts" its jawbones by yawning several times. In mammals, predators yawn more than herbivores. Giraffes , whales and dolphins have not yet been seen yawning, but monkeys all the more. In baboons and macaques, a distinction is made between real yawning (with eyes closed) and yawning out of affect or emotional tension (with eyes open). The latter can be threatening or have a sexual component. Older monkeys, especially dominant ones, yawn more than younger ones.

Yawning horse

In horses, a distinction is made between yawning and pleading . The former happens with the jaw open, while with flehmen only the upper lip is turned up. Dogs yawn extensively and for various reasons, for example to "get going" after a period of rest, in connection with stretching and stretching. Yawning can express many different behaviors in dogs, from fatigue to insecurity to calming behavior. In 1949, Julian Huxley even described that after waking up ants first stretch their head, then their six legs and then open their jaws in a way that is reminiscent of yawning. Many stories of this kind suffer from their rather casual anecdotal character and are not sufficiently scientifically substantiated.

Yawning in humans

Yawning baby

In humans, yawning, like laughing, is a universally occurring behavior. So far no ethnic group has been described that would not yawn. In contrast to monkeys and many other mammals, no gender-specific difference in frequency can be found in humans.

Theories

When yawning, one cannot speak of a reflex in the strict sense, since the properties attributed to reflexes are missing. Yawning is not a quick and short answer to a simple stimulus .

Essential when yawning are opening the lower jaw , stretching a variety of facial muscles, and squinting or closing the eyes, sometimes accompanied by tearing . Without this feedback, there is no satisfying feeling (see also self-experiments according to Provine ).

The duration of an average yawn is about six seconds but shows a lot of variation. You can yawn for only three and a half seconds or significantly longer than six seconds. Usually you yawn several times in a row, with an interval of around one minute. There is no significant correlation between the frequency and the duration of the process.

The contraction of the facial muscles and the movement of the temporomandibular joints appear to be important to satisfactory yawning. Yawning is also closely related to stretching. Like stretching, yawning increases blood pressure and heartbeat. A number of joints and tendons are also stretched.

Studies by de Vries et al. in the early 1980s show that yawning and stretching are already coupled in the fetus . Yawning could already be observed by scientists from the 11th week of pregnancy. It is very likely that boredom is not the cause here, but that there must be other reasons. It was measured that the pressure in the lungs is reduced and that tissue fragments and secreted secretions are excreted. This counteracts the expansion of the airways and lungs . Thus, yawning before birth is likely to improve lung function after birth. In addition, if joints are to develop properly, they have to be moved in the womb. Of course, this also applies to the temporomandibular joint. It is assumed that yawning and stretching are fed from the same “behavioral pool”. But they don't always appear together. For example, people usually stretch when they yawn, but don't yawn because they are stretching.

One effect of the yawning is certainly the pressure equalization between the middle ear and the surrounding area through the eustachian tube . This is not always open, but opens regularly to establish pressure equalization. Usually this happens unconsciously with chewing or swallowing movements. If you have a cold, the mucous membranes are a little swollen or if pressure fluctuations take place very quickly, for example when flying or diving, it may be that the pressure equalization has to be consciously triggered. This can also be done by yawning. The yawning person hears a “pop” when the pressure equalization is established. There are also reports of people who yawn particularly extensively when a thunderstorm lifts - the cause here could also be the change in air pressure.

No. 23 Area cingularis posterior ventralis

In investigations of yawning with the new imaging methods such as magnetic resonance tomography (MRT) , Platek et al. show that the same areas in the brain are active during yawning as, for example, in self-assessment or autobiographical memory ( cortex cingularis posterior , precuneus ). This finding supports the theory that infection from yawning is related to empathy .

It is certain that the same neurotransmitters are involved in yawning that also influence emotions , moods and appetite . It can therefore be assumed that the cause and effect are also to be found in the same area.

Serotonin , dopamine or glutamic acid increase in the brain increases the yawning frequency. In contrast, an increase in endorphins , for example, reduces the yawning frequency.

Some schools of psychotherapy take the view that yawning, in addition to laughing and crying , accompanies the processing of painful emotions and should therefore be seen as a sign of healing. Another interesting aspect is that in patients with schizophrenia , i.e. impaired self-perception, yawning is significantly reduced.

Andrew and Gordon G. Gallup of the State University of New York at Albany suggest that yawning may help cool the brain. Since mammalian brains work best when they are cool, it seemed plausible to him that cooling mechanisms developed as they developed.

During his experiments, he showed several groups of people yawning videos. If the test subjects held ice packs to their foreheads or breathed through their noses (another way of cooling the brain), they did not yawn. From this point of view, contagious yawning would make sense, since yawning together improves the brain activity and thus the attention of the group in the short term, allowing them to act more successfully in dangerous situations. This is in line with the idea that yawning could be a means of thermoregulating the body in general .

All of these effects of yawning can be seen as a kind of “synchronizing group activity”, comparable to the howling of wolves, for example to prepare for an action. This is supported by observations in other primates who, for example, coordinate their sleep-wake rhythm.

The fact that, as Gallup assumes, the brain is cooled by yawning could therefore be a holdover from our evolutionary past, whereby the whole group comes into a heightened state of attention when yawning together and is thus better able to recognize dangers. The theory that yawning helps to evenly distribute the substance known as surfactant , which "coating" the lung tissue and aids in oxygen exchange, does not contradict this evolutionary interpretation.

Threatening gestures, such as showing teeth while yawning, can serve as a tool to maintain the social structure of primate societies. Studies have been carried out on chimpanzees and stub-tailed macaques.

According to a literature study by Wolter Seuntjens (doctoral thesis, Vrije Universiteit Amsterdam), yawns are also triggered by androgens and oxytocin . It is therefore reasonable to assume that there is also a sexual component involved in yawning. In most mammals, the males yawn more, whereas in humans both sexes yawn equally. In rats, the same chemicals that cause yawning and stretching also cause an erection. Loss of libido is reported as a side effect of some antidepressants ( clomipramine and fluoxetine ). Few patients have reported an exactly opposite side effect, namely increased yawning, which induces orgasms.

Yawning may contain components of all of these behaviors and, in its current form, is a composite neurological program from our traditional fundus. Until now, no sole cause for the yawn could be found. The exact neural process and all neurotransmitters involved are still unknown.

Yawns and diseases

A study from 2007 shows that autistic children, unlike non-autistic children, not mitgähnen when viewing videos with yawning humans. This supports the theory that the "contagious" quality of yawning has something to do with empathy .

A particular demonstration of the connection between yawning and stretching are observations in stroke patients who are paralyzed on one side. The English neurologist Walshe reported as early as 1923 of patients who were paralyzed on one side and who automatically stretched their paralyzed arms when they yawned. Yawning activated apparently intact, unconsciously controlled connections between the brain and the motor system.

Clinical neurologists also report other peculiarities. Some patients with so-called locked-in syndrome , a form of paraplegia, can yawn normally. This behavior has to be controlled by parts of the brain that are historically old, such as the respiratory and vasomotor centers. It can therefore be assumed that at least a second, higher-level brain region is involved in the contagious yawning triggered by a variety of stimuli.

Frequent yawning can rarely appear as a symptom of other diseases.

Medicines and various substances can also cause increased yawning frequency:

On the other hand, people with schizophrenia have reported a decreased tendency to yawn.

Common Claims About Yawning

Yawning improves the blood oxygen saturation

Provine was able to refute the hypothesis that yawning has something to do with increased carbon dioxide or decreased oxygen levels in the blood. Students who received pure oxygen or air with 3 to 5% increased carbon dioxide content to breathe did not yawn significantly more often or differently.

Yawning is a sign of fatigue

This claim is partially true. People yawn when they are sleepy, but also more so when they get up. In experiments in which the subjects kept a “yawn diary” for one week, the subjects yawned significantly more frequently in the hour after getting up and in the evening before going to bed. It was surprising that yawning was often accompanied by stretching in the morning, while it was rarely in the evening. This observation can also be made in pets such as dogs and cats. Noteworthy is the increased flow of tears in the course of yawning, which reflects the increased need for fluid in the eyes while awake. This is important both in staying awake and waking up.

Yawning is a sign of boredom

Provine confirmed the claim that people who were bored yawned significantly more often. Yawning can also be a strong expression of emotion. If someone wants to make their boredom unmistakably clear to others, yawning is also used as an instrument.

Yawning is a sign of stress

There are quite a few anecdotal stories of increased yawning before exciting events. There are reports of “yawning fits” before the first parachute jump, sporting competitions or public appearances. This would perhaps fit in with the theory that yawning can synchronize the behavior and physiological state of a group.

Yawning can also be a sign of stress in dogs.

Yawning is contagious

Yawning is often described as contagious. If one person yawns, everyone else yawns too. Seeing another person yawn encourages yawning, especially when the person's eyes can be seen. This mechanism is also effective when the person is not physically present and is only visible on video, for example. In similar experiments in which test subjects were encouraged to smile along with them, the response was far lower. Even reading about yawning can make you yawn. Attempts by Provine to get a similar response to written hiccups failed.

Results of research on mirror neurons indicate that they are at least involved in the process of yawning. Since mirror neurons are seen as the driving force behind the imitation and thus as the basis of human learning, this assumption is reasonable. In experiments, however, Anderson & Meno found no infected yawns in children up to a few years of age. This suggests that yawning infection is based on at least one other component and that it is of relatively recent evolutionary origin.

Another guess as to the causes of the contagion is the need for a group of species to synchronize this group. Already in 1894 the ethnologist Karl von den Steinen (1855–1929) from Mülheim wrote, who was the first European in Central Australia to make contact with the Bakiri :

“If the chatter got too much for them, everything yawned sincerely and without covering its mouth. It was evident that the beneficial reflex was also contagious here. Then one by one got up and I was left alone with my Dijour.
The infection leads to the fact that all persons get tired and go to sleep at about the same time. Such a synchronization of everyday life is very important. Because if only a few would get sleepy only to fall over from tiredness, while others would move on, for example, the cohesion of the group would be endangered. "

Platek was able to establish a connection between empathy and imitation behavior. People who are not or only with difficulty infected by the yawning of others have a lower ability to put themselves in other people's shoes. This thesis was confirmed by Iacaboni insofar as observing and mimicking the emotions of others arouse almost the same arousal patterns in the brain . It has been observed that chimpanzees are also infected by the yawning of their fellow species. British and Japanese scientists see this as evidence that chimpanzees also have empathy.

In an experiment by Mascheroni, Senju and Shepherd, in which people yawned in front of dogs, 72% of the dogs were also infected to yawn. Another experiment showed that the dogs were also infected by yawning noises and reacted more strongly to the voice of their owners.

The exact neural processes involved in the infection of the yawn are still unclear.

Self-tests according to Provine

In a publication by Provine and Roberts, the reader is offered three small self-experiments that allow an insight into the nature of yawning.

  • The closed-nose yawning: If you notice a tendency to yawn, you should pinch your nose. Most of the subjects can still yawn without any problems. This means that you usually do not need to breathe through your nose to breathe in and out while yawning.
  • The clenched teeth yawn: When you feel the beginning of a yawn, you should clench your teeth, but keep breathing through the open lips. This variant gives most test subjects the feeling of getting stuck in the middle of a yawn. This shows that opening the jaw is an essential component of a complex motor program. If this is "counteracted", the feeling of satisfaction is absent and the program cannot be completed. It can also be seen that yawning is more than just a deep breath.
  • The nasal yawn: Yawning through the nose with the jaw closed is impossible. As with the clenched teeth yawning , the feeling arises of being “stuck” and the subject will not be able to avoid tensing his jaw. Inhaling through your mouth and opening your jaw is essential for a satisfactory yawn. Exhalation can be through the nose or mouth.

literature

  • Lehmann: YAWNING A homeostatic reflex and its psychological significance . 1979.
  • Baenninger: Some comparative aspects of yawning in Betta splendens, Homo sapiens, Panthera leo and Papio sphinx . 1987.
  • Smith: Yawning: an evolutionary perspective . 1999.
  • Anderson, Meno: Psychological influences on yawning in children . 2004.
  • Platek et al .: Contagious yawning: the role of self-awareness and mental state attribution . 2003.
  • Seuntjens: On Yawning or The Hidden Sexuality of the Human Yawn . 2004.
  • Monika Spang, Sonja Bougaeva: The big yawn. A zoo and bedtime story . Atlantis, Orell Füssli, ISBN 3-7152-0530-X .
  • Klaus Schmeh : Why yawning is contagious. On the trail of everyday puzzles . Gondrom, Bindlach 2008, ISBN 978-3-8112-3026-2 .

Web links

Commons : Yawn  - collection of pictures, videos and audio files
Wiktionary: yawn  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ A. Price Heusner: Yawning and Associated Phenomena . In: Physiological Reviews . tape 25 , 1946, pp. 156-168 ( baillement.com ).
  2. ^ J. Lodemann: Siegfried and Krimhild. The Nibelungs . Dtv, 2005, ISBN 3-423-13359-7 .
  3. ↑ Hannah Aitken, Ruth Michaelis-Jena (ed.): Scottish folk tales . Diederichs, 1965.
  4. ↑ Tsunetomo Yamamoto: Hagakure. The way of the samurai . Piper, Munich 2000, ISBN 978-3-8225-0644-8 , pp. 333 (1710-1716).
  5. ^ SAD Tissot: On the health of the learned . Artemis & Winkler Verlag, 1982, ISBN 3-7608-0373-3 , p. 264 .
  6. ↑ Arthur Schopenhauer: Parerga and Paralipomena . In: Zurich edition . Diogenes, 1977, ISBN 3-257-20380-2 .
  7. ↑ Gaius Pliny Secundus: Historia Naturalis . Greno 10/20, No. 17 . Noerdlingen 1987.
  8. ^ Ditte and Giovanni Bandini: Small Lexicon of Superstition . dtv, Munich 1998.
  9. ^ Joseph E. Moore: Some psychological aspects of yawning . In: The Journal of General Psychology . tape 27 , 1942, pp. 289-294 ( baillement.com ).
  10. ↑ a b c d e f g h i Richard Provine: Yawning: the yawn is primal, unstoppable and contagious, revealing the evolutionary and neural basis of empathy and unconscious behavior. In: American Scientist . tape 93 , no. 6 (November – December), 2005, pp. 532 (8) .
  11. ↑ Charles Darwin: The Expression of Emotional Movements in Man and Animals . Eichborn, Frankfurt 2000, ISBN 3-8218-4188-5 (English: The expression of the emotions in man and animals . 1872.).
  12. ^ R. Baenninger: Some comparative aspects of yawning in Betta sleepnes, Homo sapiens, Pantera leo and Papio sphinx . In: Journal of Comparative Psychology . tape 101 , no. 4 , 1987, pp. 349-354 .
  13. ↑ K. Immelmann (Ed.): Dictionary of behavior research . Paul Parey Verlag, Berlin / Hamburg 1982, p. 136-137 .
  14. ^ FC Graves, K, Wallen: Androgen-induced yawning in rhesus monkey females is reversed with a nonsteroidal anti-androgen . In: Hormones and Behavior . tape 49 , no. 2 , February 2006, p. 233-236 .
  15. ↑ Horse knowledge . ( Memento from August 8, 2008 in the Internet Archive )
  16. ↑ Günther Bloch : Wöfisch for dog owners. About alpha, domination and other popular misconceptions . Franckh-Kosmos, Stuttgart 2010, ISBN 978-3-440-12264-8 , pp. 155 .
  17. ↑ a b G. Schino, F. Aureli: Do men yawn more than women? In: Ethol. sociobiol . tape 10 , June 30, 1989, pp. 375-378 .
  18. ^ JI De Vries, GHA Visser, HFR Prechtl: The emergence of fetal behavior: I. Qualitative aspects . In: Early Hum. Dev. Band 7 , 1982, pp. 301-322 .
  19. ^ RR Provine: Behavior of the fetus . In: WP Smotherman, SR Robinson (Ed.): Ethol. sociobiol. tape 10 . Telford Press, Caldwell NJ 1988, pp. 35-46 .
  20. ↑ Thomas de Padova: Why is there pressure on the ear when flying? In: Der Tagesspiegel . May 25, 2005 ( tagesspiegel.de ).
  21. ^ A b S. M. Platek, FB Mohamed, GG Gallup jr .: Contagious yawning and the brain . In: Brain Res Cogn Brain Res . tape 2–3 , January 26, 2005, pp. 448-452 .
  22. ^ AC Gallup, GG Gallup Jr: Yawning as a brain cooling mechanism: Nasal breathing and forehead cooling diminish the incidence of contagious yawning . In: Evolutionary Psychology . tape 5 , no. 1 , 2007.
  23. ^ Schürmann et al .: Yearning to yawn: The neural basis of contagious yawning . In: NeuroImage . tape 24 , no. 4 , 2005, p. 1260-1264 .
  24. ^ Platek et al .: Contagious Yawning and The Brain . In: Cognitive Brain Research . tape 23 , no. 2–3 , 2005, pp. 448-452 .
  25. ^ Gordon G. Gallup: The Science of Yawning . In: Good Morning America . tape 5 , no. 1 , July 30, 2007 ( abcnews.go.com ).
  26. ↑ Anderson JR, Myowa-Yamakoshi M., Matsuzawa T.: Contagious yawning in chimpanzees . In: Proceedings of the Royal Society of London B: Biological Sciences . tape 271 , 2004, p. 468-470 .
  27. ↑ A. Paukner, JR Anderson: Video-induced yawning in stumptail macaques (Macaca arctoides) . In: Biology Letters . tape 2 , no. 1 , 2006, p. 36-38 .
  28. ↑ W. Seunrjens: On yawning or the hidden sexuality of the human yawn . In: Vrije Universiteit Amsterdam (Ed.): Dissertation . 2004.
  29. ^ A. Senju, M. Maeda, Y. Kikuchi, T. Hasegawa, Y. Tojo, H. Osanai: Absence of contagious yawning in children with autism spectrum disorder . In: Biol Lett . 2007.
  30. ↑ RH Shmerling: Medical Myths: What Are You About Yawning? Aetna InteliHealth, January 9, 2006 ( intelihealth.com [accessed August 29, 2007]). Medical Myths: What Are You Yawning About? ( Memento of the original from January 10, 2008 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot / www.intelihealth.com
  31. ^ Postert et al .: Pathological yawning as a symptom of multiple sclerosis . In: J Neurol. , 1996, 243 (3), pp. 300-301. PMID 8936365
  32. Jump up ↑ A. Sommet, M. Desplas, M. Lapeyre-Mestre, JL Montastruc: Drug-induced yawning: a review of the French pharmacovigilance database; Drug Safety . tape 30 , no. 4 , 2007, p. 327-331 .
  33. ↑ Friedrich Paulsen in: Wissenschaft im Dialog  ( page no longer available , search in web archives )  Info: The link was automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Toter Link / www.wissenschaft-im-dialog.de  
  34. ↑ Sean J. O'Hara, Amy V. Reeve: A test of the yawning contagion and emotionally connectedness hypothesis in dogs, Canis familiaris. In: Animal Behavior. 81, No. 1, 2011, pp. 335-340, doi: 10.1016 / j.anbehav.2010.11.005
  35. ↑ Richard Provine: Yawning as a stereotyped action pattern and releasing stimulus . In: Ethology . tape 72 , 1986, pp. 109-122 .
  36. ↑ VS Ramachandran: Mirror Neurons and imitation learning as the driving force behind "the great leap forward" in human evolution . Edge Foundation, 2006, pp. 11-16 ( edge.org ).
  37. ↑ JR Anderson, P. Meno: Psychological influences on yawning in children . In: Current Psychology Letters . tape 11 , 2003 ( revues.org ).
  38. ↑ M. Iacoboni, RP Woods, Brass, M., H. Bekkering, JC Mazziotta, G. Rizzolatti: Cortical mechanisms of human imitation . In: Science . tape 286 , 1999, pp. 2526-2528 .
  39. ↑ Ramiro M. Joly-Mascheroni, Atsushi Senju, Alex J. Shepherd: Dogs catch human yawns . In: Biology Letters , October 23, 2008, pp. 446-448.
  40. ↑ Karine Silva, Joana Bessa, Liliana de Sousa: Auditory contagious yawning in domestic dogs (Canis familiaris): first evidence for social modulation. In: Animal Cognition. April 23, 2012, doi: 10.1007 / s10071-012-0473-2 .
  41. ↑ Empathic animals: Dogs can be infected by yawning noises . Spiegel Online , May 8, 2012.