We've just finished exam time, which has meant I've spent quite a few late nights grading papers. And late nights mean yawns. Big, wide, gaping yawns....
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How many of you yawned just reading that?
We all know yawns are contagious. Your co-worker walks down the hallway towards you, yawning. Next thing you know you're yawning too. You're having coffee with your best friend, they yawn.
We all know yawns are contagious. Your co-worker walks down the hallway towards you, yawning. Next thing you know you're yawning too.
Next thing you know you're yawning too. It happens when we see people on TV yawn. It can happen when we see our pets yawn.
Even reading about yawning can make you yawn.
So why does this happen?
Scientists have been studying yawning for quite a while, but we still don't know exactly why we do it.
It's commonly thought it's to get more oxygen to our brain, and to remove excess carbon dioxide. So sort of like a special type of breathing.
This might be triggered by chemical messengers in our brain when oxygen and carbon dioxide levels are too low or high.
Another theory is that it's used to cool our brains down.
But even if we don't know exactly why it happens, it seems clear that there is some purpose to yawning.
But then there is contagious yawning - yawning that is triggered not from being tired, but just by seeing (or hearing, or reading about) someone else yawning.
Contagious yawning is an example of echophenomena - where we unconsciously copy other peoples words or actions.
It seems to be a primitive reflex - something we can't really control.
Studies have found that even if you tell people not to yawn when they see someone else yawn, they still can't help it, they'll yawn anyway.
Scientists have tracked down contagious yawning to a specific part of the brain.
It's controlled by our motor cortex - the region of the brain that, as its name suggests, controls our movements.
Within the motor cortex we find specialised neurons called mirror neurons. Mirror neurons control our movements, but are also activated - mirror-like - when we see other people doing the same movement.
Studies have found that these mirror neurons are active when we experience contagious yawning. We see it - and our brain mirrors it.
Some psychologists have looked at the relationship between contagious yawning and empathy, and have suggested that the more "cold-hearted" someone is (that is, the less empathy they have) the less likely they are to experience contagious yawning.
Some have gone as far as to suggest that a lack of contagious yawning might be a sign that someone is a psychopath.
It seems that we all have different abilities to resist contagious yawning, but it's probably linked less to our psyche and more to how excitable our brain is.
Researchers have found that stimulating the motor cortex of the brain with electrical currents can increase contagious yawning.
If you've been yawning while reading this, you might be someone with a more excitable brain.
If you rarely find yourself yawing while others around you are, yours might just be less excitable.
Or maybe you're a psychopath.
