Let's say it's getting late, you're studying with a group of friends around a table, and you see one of them stretch and yawn.
You don't feel especially tired, but soon enough — without even realizing it — you yawn too.
Then, the yawn spreads around the table, with more and more of your friends picking it up unconsciously.
This sort of contagion can happen with other things, like sniffing or laughter, and it has baffled psychologists for a while.
Most scientists agree that these so-called echophenomena exist, but there are a couple different hypotheses about why they happen.
Several clues come from studies looking at what kinds of animals and people actually catch yawns.
We've only seen contagious yawning in certain species, like humans, chimpanzees, baboons, and, in response to us, dogs.
These are all very social animals — creatures whose survival depends on working together and being sensitive to each other's needs.
And that might not be a coincidence.
One idea is that contagious yawning is related to empathy, or the ability to put yourself into someone else's shoes.
