Smiling is the act of curling one's lips upward to expose the teeth, typically in situations of pleasure or amusement. It is a universal facial expression that is used to communicate happiness, pleasure, and amusement. Smiling can also be used as a form of nonverbal communication to express friendliness, politeness, or sarcasm. Studies have shown that smiling can have positive effects on both the person smiling and those around them, such as reducing stress and increasing social bonds.

In some cultures, smiling may lead to negative attributions, such as being judged as less intelligent or less trustworthy. There are cultural differences in the way people perceive smiling. Anecdotal evidence suggests that in some cultures, smiling may be perceived as a sign of stupidity. ¹⁾