The Science of Yawning

Ever wondered why seeing or hearing someone else yawn can set you off? Does even looking at the word yawn make you want to yawn yourself? It’s easy to assume it’s down to fatigue or drowsiness, but it turns out that there is more to yawning than we originally thought.

The Science of Yawning

One of the very first theories for yawning came from the godfather of medicine himself, Hippocrates, who thought that yawning helped to clear bad air from the lungs and was the body’s way of indicating that a fever was imminent. 

This theory started to be challenged by the 17th century, when scientists started to notice links between yawning and the circulatory system, suggesting that a yawn increased blood pressure, heart rate, and oxygen which in turn improved motor function and alertness. This has since been disproved by modern science, though the reason for yawning is still not yet fully agreed upon. There are 4 main theories as to why we do it:

  • Boredom
    Most people might notice that they yawn if they are finding something dull or tiresome. Though this does not explain why athletes yawn before a race, or why dogs yawn before they want to attack something.
  • Brain-cooling
    There is some evidence to suggest that outside temperatures might have an effect on the rate of yawning. When the outside temperatures are warmer, the body yawns more frequently. This could be the body’s way of regulating brain temperature and making sure that it is not too hot.
  • Evolution
    Yawning could be linked to our natural circadian rhythms, potentially as a way of indicating the stages of our sleep-wake cycle. There are also theories that we use yawning as an ancient way of communicating stress or anger to a group.
  • Physiological
    An obvious explanation is that our bodies are trying to draw in more oxygen, to remove a build-up of carbon dioxide. This would explain why groups of people tend to set off a yawning chain reaction – where there are more people in a room, there is likely to be more carbon dioxide.

Although yawning has been observed in all vertebrates (even fish yawn), contagious yawning has only been observed in chimpanzees, humans over the age of five, and dogs. This has been described by evolutionary psychologist Gordon Gallup as a “primitive empathic mechanism related to mental state attribution”, in other words, it indicates the level of empathy felt by that individual because it activates the social behaviour part of the brain. This theory has led to the early diagnosis of cognitive disabilities such as autism in young children.

So, how many times did you yawn reading this? 

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