Why Do We Smile?
You've probably heard that when you're smiling, the whole world smiles with you. In reality, that's not exactly the case.
According to researchers, Americans smile more than residents of other countries, and those other countries don't seem eager to follow our grins. For some, persistent American smiling can be disconcerting.
To learn more, we talked to David Matsumoto, professor of psychology at San Francisco State University. He studies micro-expressions and non-verbal behavior.