Why yawning is contagious – The Fresh Toast

Someone starts it and it spreads… Why is yawning contagious?

Whether at work, school, or dinner, if someone yawns once, it's over…more yawning, then someone gets up, and the fun bubble is burst. But what happens? Why is yawning contagious? In 400 BC, Hippocrates believed that yawning clears bad air from the lungs before it causes a fever. In the 17th and 18th centuries, doctors believed that yawning increases oxygen levels in the blood, blood pressure, heart rate, and blood flow itself. So it makes sense that you'd want to follow suit…but what causes the body to involuntarily yawn?

There have been many hypotheses in the past, but in the last century it has been agreed that yawning cools the brain, so yawning attacks become more frequent when environmental conditions and the temperature of the brain increase.

A yawn typically lasts four to seven seconds and occurs in two or three bursts. It involves the following steps:

• A long inhalation (breathing in) through the nose and then through the mouth.
• A brief episode of vigorous muscle stretching around your mouth and throat.
• A quick exhalation through the mouth followed by muscle relaxation.

Yawning is largely involuntary, meaning you have no control over it. And most scientists consider it a reflex.

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And yawning occurs in almost all species. It happens when an animal is tired. In some species, it can be used as a threatening gesture. Yawning can occur in times of social conflict and stress, something researchers call displacement behavior. So it's not just a human response, it's also common in the animal kingdom… so why does it happen and why is it so damn contagious?

Yawning occurs in many animal species – and seems to pass from one to the other. Robert Gramner on Unsplash, CC BY

Yawning is a common but confusing human function. Scientists have several theories but no concrete ones. Common triggers for yawning include tiredness, boredom, waking up, and stress. A current theory on yawning is the arousal hypothesis, which states that yawning activates your brain. This theory is based on the fact that tiredness and boredom most commonly trigger yawning.

If you see or hear other people yawn, it can make you yawn too. The wide-open mouth can be contagious, especially in social species such as humans, chimpanzees, bonobos, macaques, and wolves. In addition, studies on humans show that people who are more empathetic are more prone to contagious yawning. If you see someone else yawn, Networks in your brain responsible for empathy and social skills are activated.

Is yawning contagious for dogs too? In the UK, biologists tested whether yawning is contagious between humans and man's best friend. Although 5 of the 19 dogs studied yawned in response to a stranger's yawn, the researchers could not prove that the yawning was contagious. But cognitive and behavioral researchers at the University of Tokyo again tested contagious yawning in dogs under stress control. This time, the 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 a social rather than a stress-related behavior.

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Psychologists at the University of Nebraska studied contagious yawning in shelter dogs. They found that some dogs yawned when exposed to human yawning and had elevated cortisol levels, an indicator of stress. Dogs that did not yawn in response to human yawning did not experience an increase in cortisol levels. This finding suggests that some dogs find human yawning stressful and others do not. More research is needed to examine this aspect of the human-dog relationship.The true cause of yawning is not yet understood. But when it comes to yawning between species, gather your own anecdotal data. Do an experiment at home, yawn and see if your pet yawns back.