The Big Yawn

  • From my big, arms-outstretched morning yawn, to my stifled awkward supressed facial stretches in online meetings, I yawn a lot. From Hippocrates to the modern day, scientists have long pondered over the reasons why we yawn. Here we’ll look at some of the explanations and discover if other species also partake in this strange, highly contagious activity.

    Absolutely everyone yawns. Men, women, children, grandmas, great-uncles and even foetuses in the womb have been known to yawn. It is still debated as to why we yawn, but scientists have a number of theories. The first is one you’ve probably re-told yourself: when we’re tired or bored, we don’t breathe as deeply as we would usually and thus we take in less oxygen because our breathing has slowed. To compensate our body takes a big yawn, bringing in more oxygen and replacing the carbon dioxide in our blood. As I said, the standard answer you would give at a virtual pub quiz. However, this theory would suggest that yawning is a completely involuntary reflex to help regulate the oxygen in our blood. Studies have since shown that breathing in more oxygen doesn’t decrease our yawning, so why else might we yawn?

    Here are three other popular theories:
    1. Stretching our lungs and lung tissue – yawning could present a way to stretch our muscles and joints, increase heart rate and subsequently make us feel more awake, by forcing more blood to our face and brain.

    2. A protective reflex – yawning may redistribute the oil-like substance (i.e. surfactant) which helps to lubricate the inside of our lungs and keep them from collapsing.

    3. Brain temperature – the most scientifically backed theorem to date. In 2014, it was hypothesised that if the brain’s temperature got too far from the norm, a deep inhale could cool it down. If you’re tired or bored, your brain slows down and yawning could help to regulate the temperature, cooling it to within a normal range. The study looked at seasonal changes and the difference in yawning rate between summer and winter months. In colder conditions, the yawning rate was lower than in the warmer summer months suggesting, to the researchers, that the brain liked cooler conditions and required more thermal regulation in the summer. By yawning, our jaw moves and thus our blood moves around the skull, helping to carry away excess heat. A deep breath in then brings cooler air to our sinuses which lead to the brain, cooling it down.

    Why are yawns contagious? About 50% of people who observe a yawn will yawn in response. In fact, yawns are so contagious that even merely mentioning them can trigger them…sorry. Some researchers believe that the contagiousness of yawns could be a clue as to their purpose and possibly linked to primitive communication methods. Could yawns have been a way of syncing a group of people’s biological clocks, telling them when it was time to be tired? If a group has the same routine they can work together more efficiently. Yawns could also help a group of people reach the same level of alertness. If yawns help us stretch and become more alert, and if they’re also highly contagious, this could help a group reach the same level of attention, making them more vigilant to threats (or just equally sleepy at the back of a lecture hall…). Whilst we all acknowledge how contagious yawns can be, it appears most contagious between friends and family, which supports a theory of emotional bias and a close connection to “our group”.