Why do we yawn and is it really contagious? The science of yawning explained by experts

Yawning is something we all do many times a day, and there are many theories around why. Some people think that yawning happens simply because people are bored or tired, but there is more to it than that.

The act of yawning unites those of all ages, and even different species. Humans and animals do it all the way through their life, and begin doing so before they are even born. Another common theory linked to yawning is that it is contagious and so people and animals who see their peers do it will also mirror back this action.

To find out the truth behind the science of yawning and discover if it really is contagious, we spoke to three doctors to get all the information you need.

What is a yawn?

To start with the most simple question, a yawn is a common, uncontrollable reflex where you open your jaw wide, take in a deep breath, and then quickly exhale. It usually lasts between five and ten seconds, and can happen many times during the day. Doctor Hana Patel, a GP specialist in sleep, says that people yawn on average five to ten times a day.

Why do we yawn?

Dr Patel explains that there are several reasons why people yawn, including to regulate ear pressure, for example when on an aeroplane or swimming, or when we are feeling tired or sleepy and perhaps haven’t got the amount of sleep we need.

Doctor Ross Perry adds that yawning happens when we make the transition between waking and sleep either first thing in the morning or last thing at night, and also when we are bored, when we feel the need to be alert, and also if our brain temperature suddenly increases.

What’s happening in our brains and bodies when we yawn?

Yawning is a semi-voluntary action and partly a reflex controlled by chemical substances called neurotransmitters in an area of the brain called the hypothalamus, according to clinical psychologist Dr Patapia Tzotzoli. It is thought as a mechanism that helps ‘thermoregulate’ the brain. 

 Dr Tzotzoli adds: “During a yawn the jaw stretches out, the mouth opens wide, facial muscles move and contract and the lungs take in a lot of air before it is slowly exhaled. In the meantime, the eardrums stretch, the eyes might water to release heat, the heartbeat gets more rapid which increases the blood flow in the face and releases even more heat. Yawning may also act as a physiological function that helps cool down the brain that has become too hot as this can maintain its core temperature.”

Is yawning really contagious?

Yes, yawning really is contagious. That means if you see or hear someone else yawning you are very likely to yawn yourself. This will be an involuntary reaction to seeing or hearing someone else do it.

“There are a couple of different theories as to why yawning is contagious,” explains Dr Perry. “One is that when people yawn it often causes others in close proximity to yawn and this is due to something called echopraxia, which is when we see a person do a certain behaviour and our mirror neurons in the brain mimic the action.

“Another theory is that when other people yawn we can also become more sensitive to our own physiological state, so we may be tired and didn’t realise it until someone yawns near us. It’s also possible that the yawning sound can also trigger a sympathetic yawn, which again is caused by the brain mimicking the response.”

Dr Patel adds that it’s not just humans who yawn when they see someone else do it - dogs and chimpanzees do it too. 

Could yawning be a sign of a health problem?

Yawning is a natural bodily function which happens to everyone, so it’s not necessarily a cause for concern. Dr Patel adds, however, that excessive yawning beyond the average amount outlined above could be a possible sign of a health problem or sleep related disorder.

She said: “I would encourage patients to make an appointment with their GP to have a further discussion about their concerns, as it may be a sign of underlying sleep deprivation, insomnia, sleep apnoea, narcolepsy, or a side effect of medicines that cause sleepiness.” She added that a particularly excessive amount of yawning would be 100 yawns per day.