Studies find that people in more diverse countries, countries with great numbers of immigrants, rely on smiling to build trust and to build cooperation. A simple reason for this is the fact that we don’t all speak the same language. But there is a different, and I think, more meaningful reason for smiling in countries with more immigrants, and that is that smiling is a way to bond socially. A smile is a rather universally understood thing. Surely we can recognize a fake smile, a genuine smile, a wicked smile, a forced or sarcastic smile. But we know a smile when we see it.