The study has evolved as a social signal to warn others that we are less alert

Many theories have been proposed to explain why animals yawn, such as replenishing oxygen supplies, cooling the brain, and even lengthening the lungs.

Now, a new study says yawning has evolved as a social signal to warn others that we are less alert, and therefore need to be more alert for predators.

Meanwhile, the phenomenon known as “contagious yawning” – yawning reflexively after seeing or hearing another individual yawn – is thought to have further spread this signal among groups of social animals.

As this behavior evolved on the plains of Africa thousands of years ago and no longer applies to modern humans, it is possible that yawning could become extinct.

Previous analyzes have already suggested a positive correlation between yawn duration and brain size, meaning the larger the brain, the greater the yawn.

The yawn is a trait common to multiple species, but until recently little was known about the actual function of a yawn, according to a researcher at the New York Polytechnic.


A yawn is a reflex involving the simultaneous inhalation of air and the stretching of the eardrums, followed by the exhalation of air.

It is most commonly associated with fatigue and occurs before and after sleep, although boring activities can trigger a yawn, as well as a yawn.

Most vertebrates are known to yawn, and a contagious yawn has been demonstrated in humans, chimpanzees, dogs, cats, birds and reptiles, including between different species.

There have been multiple explanations as to why we yawn and why they appear to be contagious.

A recent study suggests that longer yawns are linked to larger, more active brains getting hotter.

This led the team to suggest yawning to cool the brain.

Rather than fatigue or inattention, we are cooling our minds and preparing for the next activity.

Another study suggests contagious yawning evolved as a mechanism for keeping animals, especially prey animals, alert.

The study was led by Professor Andrew C. Gallup, a behavioral science researcher at the State University of New York Polytechnic Institute, and published in the journal Animal behavior.

“Yawning is a ubiquitous neurophysiological adaptation in vertebrates, and the detection of this pattern of action in others appears to be biologically important across social species,” he says in his paper.

‘[It] it serves as a signal that improves individual alertness and promotes motor synchrony through contagion. ‘

The yawn is a trait common to several species, but until recently little was known about the actual function of a yawn.

To find out more, Professor Gallup conducted a review of previously published scientific studies to evaluate the causes and consequences of yawning in groups of animals.

He explored the “psychological and social significance” of yawning in mammals and birds.

According to the research, recent studies have presented the idea of ​​yawning as a type of social signal, warning observers that the yawning individual is less alert.

Yawns, he says in his article, can be spontaneous or contagious: the former seems to come out of nowhere, while the latter results in seeing someone else yawn.

By definition, any contagious yawn can be traced back to an original spontaneous yawn, and for this reason the contagious yawn must have evolved more recently over time.

‘Evidence suggests that the yawn originally evolved as a spontaneous event, and therefore physiological in nature,’ said Professor Gallup.

Figure 1. Factors known to contribute to spontaneous and contagious yawning and graphic illustrations of the social effects resulting from the observation of yawning in others in both (a) absence and (b) presence of yawning 'contagion'

Figure 1. Factors known to contribute to spontaneous and contagious yawning and graphic illustrations of the social effects resulting from the observation of yawning in others in both (a) absence and (b) presence of yawning ‘contagion’


Elephants can “catch a yawn” from humans they know well, according to a 2020 study.

Researcher Zoe Rossman of the University of New Mexico Worked with a herd of captive elephants at Knysna Elephant Park in South Africa.

Handlers who yawned in front of African elephants found they were more likely to yawn if they saw a human doing it than any other type of human mouth movement.

While spontaneous yawning is common to all classes of vertebrates, contagious yawning is less common and has only been observed in a few species of animals.

“Contagious yawns appeared later and was only documented in social species.”

Contagious yawning has only been documented in social species – those that are genetically prone to clustering – and it doesn’t develop until infancy.

According to Professor Gallup, numerous hypotheses have been proposed to explain the physiological significance of yawning, but most lack empirical support or have proved wrong.

For example, there is a common but erroneous belief that yawning works to balance oxygen levels in the blood.

But experiments on human subjects have shown that the frequency of yawning is not altered by increased or decreased oxygen or carbon dioxide levels of respiration.

‘It was therefore concluded that yawning and breathing are controlled by different mechanisms, and it is now widely accepted in the scientific literature that breathing is not a necessary component of yawning,’ says Professor Gallup.

last year, Utrecht University researchers he said yawning helps cool the brain and doesn’t work to oxygenate our blood.

They collected over 1,250 yawns from more than 100 species of mammals and birds by visiting zoos with cameras.

Other studies in humans, non-human primates, rats and birds have all shown that the frequency of yawning can be reliably manipulated by changes in ambient temperature, lending support to this argument.

Professor Gallup does not think previous yawning theories are necessarily wrong and recognizes such physiological functions of yawning.

But overall, current evidence suggests that yawning primarily serves “as a cue rather than a signal,” according to the author.

“Future studies could further examine whether spontaneous yawns have evolved specifically to communicate internal states and / or alter observer behavior in some species,” he says.

Yawning is contagious even for lions! Animals in South Africa have found that they mimic behaviors to aid group cohesion

Some animals, including humans, will start yawning after someone else nearby yawns, and a new study suggests this “contagious yawn” helps fuel group cohesion.

Lions can trigger each other's yawns, just like humans. But while his

Lions can trigger each other’s yawns, just like humans. But while his “contagious yawning” in humans is a sign of empathy, experts say that for lions it is a way to synchronize behaviors and be a more cohesive pride.

Researchers observe the lions inside South Africa found that animals don’t just mimic each other’s yawns, they copy subsequent behaviors.

If a lion yawned, then got up and moved somewhere else, another cat was almost sure to do the same.

Scientists believe that such synchronized behavior allows pride to work as a team, find food and spot threats to the group.

Animals yawn for various reasons, according to researchers from the University of Pisa: sometimes it is a state of transition from wakefulness to sleep, other times it is a reaction to “high social tension”.

But a number of social animals – from wolves to birds to monkeys – have been observed engaging in “contagious yawns,” in which one member of one group triggers another’s yawn.

“Due to their high social cohesion and synchronized group activity, wild lions are a good model for studying both spontaneous yawning from the physiological domain and, possibly, contagious yawning, from the social communicative domain,” the scientists wrote in a report published in the journal Animal Behavior.

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