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While the creepiest thing Americans have done recently is accidentally electing a nonverbal old man who has openly lusted after his own daughter to the presidency, the truth is, we’re pretty creepy people all around. We have been weirding out our global neighbors for years, it turns out, with one habit in particular: that is, our insane penchant to walk around smiling at each other constantly.

An article on The Atlantic digs into this curious phenomenon, investigating not just how we smile but why we do it—and why other cultures do not. A huge part of it comes down to our nation’s rich history of immigration, which has built nonverbal communication (like smiling!) into the fabric of our culture as a way of letting other people know that we are friendly and mean no harm. Of course, today those smiles to people with whom we do not share a common language have come to mean, “You are not an American and I will see to your swift apprehension by authorities,” but our customs change slowly. We are still going around generally thinking it is okay, appropriate, and encouraged to smile at each other all the time, whereas in more homogenous countries smiling can be seen as a threat. As author Olga Khazan puts it:

In the countries with more immigrants, people smiled in order to bond socially. Compared to the less-diverse nations, they were more likely to say smiles were a sign someone “wants to be a close friend of yours.” But in the countries that are more uniform, people were more likely to smile to show they were superior to one another. That might be, the authors speculate, because countries without significant influxes of outsiders tend to be more hierarchical, and nonverbal communication helps maintain these delicate power structures.

That all sort of makes America sound like a much happier, more tolerant place to live, but Khazan goes on to dig into the type of smile we insist on showing to the world. We prefer what scientists have determined is an “excited smile,” showing a sort of high-energy enthusiasm for whatever it is we’re currently doing. The fact that this is not an organic response to everyday life and is instead something we manufacture drastically at odds with our current internal emotional state is probably what makes the whole thing so eerie to the rest of the world. It’s obviously extremely anecdotal, but something like this Reddit thread, which asks people for giveaways that someone is American, cites over and over again how often people can pick American out by their incongruously enthusiastic smiles.

That, and our inability to use the metric system. We are an obstinate people.