This is an interesting thing because most people don’t know what a smile actually entails. Most animals that are capable of expressing emotions do it with their eyes, ears, and body language. But we get told a smile is something you do with your mouth, which is wrong.

If somebody smiles at you with only their mouth, they are lying through their teeth. Genuine smiles always involve the eyes.

YESSSS.  Duchenne smiles happen spontaneously due to joy or amusement, and they involve the eye-wrinkly thing like andalites are described as doing.  Non-Duchenne smiles are the kind we do to be polite, to be photographed, to create a smile outside of amusement/joy — it’s not necessarily lying, but usually about trying to smile on command.

There’s also a FASCINATING cultural discrepancy wherein people from more individualistic cultures (U.S., Australia, Germany, South Africa, etc.) look more at the mouth to detect smiles, whereas people from more collectivistic cultures (Japan, Venezuela, Kenya, India, etc.) look more at the eyes.  So the idea of “smile is something you do with your mouth” is way more common in the U.S. than, say, South Korea.

That’s why the U.S. emoticon for a smiley is this...

:)

And the Japanese emoticon for a smiley is this...

^_^

Well that makes COMPLETELY PERFECT SENSE now that you point it out!