Why Do People Smile?It's not entirely clear whether smiling is an innate or learned expression. Even babies have been shown to smile while still in the womb. However, people who have little or no social interaction growing up seem to lose the ability, or at least the understanding of how, to smile. This suggests that smiling may be influenced both by the mind and by social situations, though there isn't any way to know for sure.
People have different personal reasons for smiling as well. You might smile because you've just encountered a friend whom you haven't seen in a long time. Funny books, movies and television shows invoke a lot of smiles. Laughing at yourself for doing something silly provokes a smile too, and it can also help you to feel better about an otherwise negative situation.
Not every person will react with a smile to the same things. Similarly, not everyone who is happy will smile, and not everyone who smiles is happy. Despite research and study into this common expression, there doesn't seem to be any concrete answer as to why smiling is such an integral part of the human experience.