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You know the feeling. It's impossible to resist. You just need to yawn.
A yawn is a prolonged yawn of the mouth followed by a faster closing. In mammals and birds, a long breath and shorter expiration follow the gaping mouth, but in other species such as fish, amphibians and snakes, there is no breath
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In the past, people have had a lot of badumptions. From 400 BC BC, Hippocrates thought that yawning removed bad air from the lungs before fever. In the 17th and 18th centuries, doctors believed that yawning increased oxygen in the blood, blood pressure, heart rate and blood flow itself.
More recently, the consensus has shifted to the idea that yawning cools the brain, so when ambient conditions and brain temperature increase, yawning episodes increase.
Despite all these theories, the truth is that scientists the true biological function of a yawn
What we do know is that yawning occurs in just about every species. It happens when an animal is tired. It can be used as a threat in some species. Yawning can occur during periods of social conflict and stress, what researchers call displacement behavior.
This open mouth can be contagious, especially in humans, chimpanzees, bonobos, macaques and wolves. Watching someone yawn – heck, even reading about yawning – can cause you to yawn yourself. Why?
Research on humans tells us that people who are more empathetic tend to be more susceptible to contagious yawning. When you see someone else yawning, the networks in your brain responsible for empathy and social skills are activated.
Is yawning also contagious for dogs? In 2011, British biologists tested a contagious yawn between people and the best friend of man. Although 5 of the 19 dogs studied yawned in response to a yawn from an unknown person, the researchers could not prove that the yawning was contagious.
In 2013, cognitive and behavioral scientists from the University of Tokyo again tested contagious yawn. canines while controlling stress. This time, researchers found that dogs were more likely to yawn in response to a familiar person.
They concluded that dogs can "catch" a yawn from humans and that yawning is social behavior rather than stressful.
In 2014, psychologists from the University of Nebraska observed contagious yawning in shelter dogs.
They found that some dogs that yawned when exposed to human yawning had high levels of cortisol – an indicator of stress. Cortisol stress hormone levels have not increased in dogs who have not yawned in response to a human yawn. This discovery suggests that some dogs find human yawning stressful and others do not. More research is needed to evaluate this aspect of the dog-human relationship.
So the jury is still on the true why yawns. But when it's inter-species yawning, you can collect your own anecdotal data. Try an experience at home: Yawn and see if your pet bounces.
This article has been reprinted with permission of The Conversation.
Christine Calder is Assistant Clinical Professor of Behavior at the College of Veterinary Medicine, Mississippi State University.
© Nine Digital Pty Ltd 2018
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