6 Everyday Things That We Still Don’t Know How To Explain

Why We Yawn, and Why It’s Contagious

You’d think by now we’d have a solid answer for yawning, but nope—the leading theories (cooling the brain, changing alertness) are still just guesses. Even weirder, seeing someone yawn can trigger your own yawn, and scientists aren’t sure why empathy or mirror neurons are involved. So congratulations: reading this sentence might have already made you yawn.