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It's a question that has puzzled scientists for a long time: why exactly do we yawn?
In a recent breakthrough, scientists have discovered the part of the brain responsible for contagious1 yawning. It's called the primary motor cortex, and controls movement in the body. When triggered it makes us yawn. But we can't choose to yawn – it's an involuntary imitation of other people. You know how it goes: your friend yawns, you yawn.
Knowing which section of the brain is involved is only part of the answer. There is still a deeper question of 'why'. And we don't only yawn when others do, we sometimes yawn alone.
So, let's start with the physiological2 theories behind yawning. As far back as 400BC, Greek physician Hippocrates speculated that yawning released harmful gases from the body, like "steam escaping from a cauldron". His colourful theory is now, sadly, discounted.
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