WHEN I give talks about my work, I know that before too long the audience will start to yawn. Just thinking about yawning makes us do it, but the mechanisms behind this everyday behaviour are a mystery.
Yawning is often the first thing we do when we wake up, but we also do it when we are bored, tired or anxious. It is a primitive reflex that we share with other animals, from fish to mammals. We first start yawning in the womb, at around 20 weeks gestation, and as we age, we yawn less frequently. It happens most in the morning, but despite yawning being universal, the reason we do it is still unclear.
Boredom leads to yawning, so it has long been assumed that the action is an arousal reflex that makes us feel more awake by stretching the muscles surrounding the lungs, or by bringing more oxygen ...
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