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Things Yorami know: Why is yawning contagious?

Limor asks: Why do you yawn and why is yawning contagious?

A lion yawns. Filmed in South Africa. Illustration:
A lion yawns. Filmed in South Africa. Illustration:

 According to the Muslim tradition, yawning is the creation of the devil: he opens his door to enter us, as strange as it may sound, to this day science has no better answer to the role of the yawn. Yawning is a universal phenomenon, not only each of us yawns at least 5 times a day, but almost every vertebrate: mammal, bird and even reptile yawns sometimes. It is likely that the behavior that is jealously guarded throughout the animal world will have a role, but as strange as it is, it seems that the secrets of the big bang will be solved before the mystery of the yawn. The oldest and simplest hypothesis is that yawning is a type of deep breathing designed to circulate more oxygen and thus maintain alertness. 

The facts, for their part, insist on spoiling the simple picture. In a study in which the composition of the air was changed from pure oxygen (compared to 21% oxygen in normal air) to mixtures containing carbon dioxide in concentrations 100 times the atmospheric concentration, the subjects maintained a completely normal frequency of yawning. Another theory claims that yawning is a means of cooling the brain: according to this theory, in states of fatigue the control mechanisms that maintain a constant temperature of the brain are weakened and to cool the gray cells we activate the facial muscles and thus increase the blood flow to the head and heat dissipation. This theory is confirmed by the fact that breathing through the nose prevents yawning (here is a scientific tip to prevent embarrassing yawning in boring meetings) as well as cooling the forehead by attaching a handkerchief soaked in cold water.

Impairment of temperature balance in patients with many diseases

Situations in which the brain's ability to balance temperature is impaired are also accompanied by a lot of yawning, such as in patients with multiple sclerosis, epilepsy, migraine and other diseases. And yet apparently this theory also does not provide a complete answer: why do people stretch while yawning and why do cold-blooded animals (which do not bother themselves with maintaining a constant body temperature) also yawn. A yawn is not just a deep breath but a simultaneous stretching of a large group of muscles, starting with the muscles of the face and jaws, the muscles of the neck and of course the muscles of the respiratory system. Yawning occurs, both in humans and in animals, during the transition between wakefulness and sleep and the opposite transition: waking up. The yawning, according to one hypothesis, is a means of the nervous system to receive information about the state of the system and to move from a state of stasis, meaning low muscle tension, to a state of full control and alertness. To use a military image, yawning is a sort of order that the autonomic nervous system conducts for the soldiers who are supposed to carry out the tasks it assigns them. This "order" returns the muscles to a high level of readiness, renews the tension of the muscles that relaxed during the surfing to doze off and updates the brain's information on the state and location of the vital system parts.

Just like orders in the army, all yawns in animals occur in the transitions between states of rest and high alertness, meaning they are a kind of reset operation of the nervous system that allows it to start functioning in the new state. Thus, the theory explains, yawning is common to all animals that have cycles of REM sleep (dream sleep) in which the brain functions vigorously but the muscles relax and become silent so that the dream thoughts are not translated into action. It seems that the REM sleep is the oldest from an evolutionary point of view, therefore the mechanism that allows a good exit from it is shared by all sleepers. The exceptions that do not yawn include the giraffe whose REM sleep is short and can go many days without sleeping at all, as well as the dolphin and the whale who send each half of the brain (hemisphere) to sleep separately. Fetuses yawn in the womb as early as the beginning of the fourth month when the cycles of sleep and wakefulness begin. Fetuses and babies experience much more REM cycles than adults and accordingly also yawn much more.

Yawning just thinking about yawning

And why do we catch a yawn at the sight of a yawning person or even while reading or thinking about yawning? We are social creatures and accordingly our minds are busy deciphering the emotional state of those around us. Neurons called "mirror cells" reproduce for us sensations that we "read" from the transmitters sent to us by other people. This reconstruction sometimes also includes the accompanying physical gestures, a clear example is a parent feeding his child and opening his mouth when he hands the spoon. The more significant the person is to us, the greater the chance that we will "step into their shoes" and yawn along with them, as was demonstrated in an experiment in which the effect of strangers' yawns compared to a partner's yawn was tested. Even in our relatives the chimpanzee and the orangutan, yawning can be induced by showing films showing yawning monkeys. This ability reminds, and not by chance, another point of similarity between us and these monkeys: the ability to recognize oneself in the mirror. Yawning is an expression of empathy, that is, a reflection that the brain makes of a message received from the other person. For the purpose of empathy, it is necessary to have the ability that most animals do not have, and that is to perceive ourselves "from the outside" (like the image reflected in the mirror) and to create an internal image of ourselves as we appear to others.

Yawning as a reflex is very common, but the contagion of yawning is limited to species living in close-knit groups with an organized social structure, such as chimpanzees, wolves, lions, elephant seals, sheep, and even one species of social bird - the parrot  The common common pet (Melopsittacus undulatus). In the animals of these species, yawning is more contagious the more socially relevant the yawn is. Thus, in a group of chimpanzees, the males are more beautiful after the dominant alpha male yawns, while in the bonobo the males will be infected mainly from the yawns of the females.

Dogs have contracted yawning from humans

In an interesting experiment, researchers were able to make dogs yawn when they watched the reflection of a yawning person in a mirror. No less than 72% of dogs have contracted yawning: more than humans (45-60%) or chimpanzees (33%). If this yawn indicates real empathy from the dog to the human, it may be an evolutionary adaptation that allows the dog to increase vigilance together with its owner. Other researchers doubt the idea that the connection to a person is embedded in the reflex reactions of the dog and claim that, similar to the movement of licking the nose, the yawning reaction of the dog is a sign of stress and social anxiety and not identification. Administering oxytocin: a hormone that increases social interaction actually reduced the tendency to contagious yawning in the dogs in the experiment.

 In an experiment that examined personality differences between people who were infected by yawns that were projected onto them and those who remained indifferent, it was found that those who were infected by yawns were able to recognize a picture of themselves from several options more quickly than those who kept their mouths closed. Having characteristics of schizotypal personality (Schizotypal personality) - disorders that are manifested, among other things, in difficulty in creating social relationships Get infected less with yawns. Pregnant women are more prone to yawning than their non-pregnant peers and some attribute this to hormonal and neural changes that increase the ability to bond emotionally before birth. There are those who suggest that yawning was used in our distant past as a means of communication: joint timing of "lights out time" and waking up in our ancestors, this type of social yawning was observed in macaque monkeys.

 If we believe the psychological publications, then about 45% of the readers of this column yawned while reading and the higher this percentage seems, the better their mental state.  

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3 תגובות

  1. I didn't stop yawning from the middle of the article to the end...

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