Why do people often place their hands over their mouths when smiling joyfully? Is it cultural? I notice that Asians seem do this more commonly than other groups but that could just be my own perception. I know that almost everyone does it to some extent. Is there some more basic, primal need to cover your teeth so as to not seem threatening? It looks like humans are embarrassed by expressing joy. I find the ear-to-ear grinning contagious and it seems a shame to cover it up.
In some cultures, such as Japanese, it’s considered rude to laugh out loud with an open mouth. Children are taught early on to cover their mouths when they snicker. I believe it’s culturally based. Why it’s considered rude I can’t say. Nowadays women seem to do it more than men do.
In America, people cover their mouths when they are surprised. If they are surprised by something pleasant, they might be smiling also but that’s coincidental.
Think about a jewelry commercial-- the woman isn’t covering her mouth because she’s happy, she’s covering it because the ring was a surprise and just happens to also be happy.
Then watch a horror movie, and you’ll see the same mouth covering due to the surprise of the ghost appearing, but now the emotion is fear and there’s no smile.
EDIT: and no I don’t know why covering the mouth is a reaction to surprise, I’m just reporting what I’ve observed.
I know someone who covers her mouth because her teeth are so horrible.
I know at least two women who cover their genuine smiles because they believe they look unattractive when they smile that way. They censor pictures of themselves, allowing only the ones where they’ve got their “camera face” on and the angle is right.
There are also people who never open their mouths when they smile. I’m assuming it’s mostly because of bad-looking teeth, but I can think of at least a couple of celebrities with good teeth who do it most of the time.