No one looks pretty doing it yet somehow, when we see someone compulsively distort their face into a yawn, we feel inclined to do the same. We share this odd behaviour with a whole bunch of animals, who each do it for different reasons. Dogs do it when they’re confused, snakes do it to realign their jaws, lions do it to feign indifference in the face of combat, male penguins yawn to woo a mate and guinea pigs do it to scare enemies with their fierce incisors.
Ancient Greeks and Mayas believed that yawning was the soul trying to escape the confines of the body and that it could only be stopped by covering your mouth. In Hinduism, yawning is considered a religious offense that must be repented by snapping your fingers and thumb and pronouncing the name of Raina. A more ‘sciency’ (yet equally unproven) notion is that yawning helps replenish blood oxygen.
In truth, yawning has only quite recently been husked of some of its mystery:
Us humans, as it turns out, are literally just cooling our brains (try yawning with a cool pack on your forehead). The reason for this is that our brains work best within a narrow temperature range. Staying awake longer than we should can heat up your brain as processes can get a bit out of control. When we go to sleep our brain temperature drops, allowing our brains to deal with some of the damage done during our waking hours. So perhaps yawning is just a quick fix until we can take a nap or sleep
The balance of chemicals in your brain also affects how much you yawn. Endorphins (increased by exercise, orgasms and horror movies) and adrenaline, generally prevent you from yawning while serotonin (increased by most antidepressants and MDMA) makes you yawn more. Why these chemicals affect yawning the way they do is still a bit of a mystery.
Yawning is contagious. In fact, just hearing someone yawn or reading about it (sorry…) will do the trick. Amazingly, yawning even breaks the species barrier, with studies showing that dogs and chimps will both mimic a human yawn! The degree of contagiousness amongst humans depends on how emotionally close you are to the yawner. Also, individuals with autism/asbergers syndrome don’t yawn in response to others; leading to the suggestion that this mimicry is based on empathy and may be an accurate index of your empathetic capacity. It certainly makes an interesting way of testing friendships…
So why is it contagious?
It all comes down to mirror neurons in your brain. Generally when you see someone move, certain cells in your brain tend to mimic the action. This helps us to imitate the actions of others, but also to understand them. Actually acting out whatever other people do is usually suppressed (see here for a fascinating talk on mirror neurons and their importance). In the case of yawning, it’s not. The reason it’s not suppressed might not be a coincidence – it smells of evolution. One idea is that it gets social animals to increase their vigilance as a group – so all of them keep a cool brain when on the look out for predators. It could also help signal tiredness to fellow group member, a non-verbal way of saying “it’s bed-time kids”.
So don’t feel bad about yawning. You’re boosting your brain power and showing you care. But you should still cover your mouth. 🙂
Post by: Isabel Hutchison