Why we yawn

[00:00.40] It’s a question that has puzzled scientists for a long time: why exactly do we yawn?

[00:06.25] In a recent breakthrough, scientists have discovered the part of the brain responsible for contagious yawning.

[00:12.36] It’s called the primary motor cortex, and controls movement in the body.

[00:16.87] When triggered it makes us yawn. But we can’t choose to yawn – it’s an involuntary imitation of other people.

[00:23.78] You know how it goes: your friend yawns, you yawn.

[00:27.23] Knowing which section of the brain is involved is only part of the answer.

[00:30.68] There is still a deeper question of ‘why’. And we don’t only yawn when others do, we sometimes yawn alone.

[00:37.59] So, let’s start with the physiological theories behind yawning.

[00:42.11] As far back as 400BC, Greek physician Hippocrates speculated that yawning released harmful gases from the body, like “steam escaping from a cauldron”.

[00:52.73] His colourful theory is now, sadly, discounted.

[00:55.65] A more recent idea suggests that we yawn in order to cool down the brain.

[01:00.17] Just like a busy computer processor, our brains can overheat.

[01:04.68] Psychologist Gordon Gallup from the University at Albany has argued that the act of yawning delivers a rush of oxygen to the brain, helping us think more clearly.

[01:15.31] What about the connection between yawning and tiredness?

[01:18.50] We certainly yawn more when we’re feeling sleepy or sluggish, but why is this?

[01:23.28] Theories that it helps give the body extra energy are largely discredited, as we don’t yawn when we exercise, a time when we definitely need more get-up-and-go!

[01:32.84] Psychologist Catriona Morrison from the University of Leeds says yawning is an ancient reflex.

[01:38.68] She told the BBC that it may have started in “the days of cavemen when someone had to be on watch all the time - yawning increases cerebral blood flow so can improve alertness.”

[01:49.84] What about our friends' contagious yawning? Some think it comes down to empathy.

[01:54.62] While all vertebrate mammals yawn, only humans and chimpanzees ‘catch’ yawns from others.

[02:00.20] Studies have shown we yawn more frequently when in the company of close relatives and friends.

[02:05.51] Could yawning actually help us cement our closest relationships?

[02:09.50] If it does, next time you yawn in company, don’t feel too embarrassed.

[02:13.75] You’re just showing off your people skills.