1. It makes us seem trustworthy: We generally interpret a genuine smile to mean that this is someone who is honest and trustworthy. Those who smile are rated higher in generosity, in extraversion and in friendliness
2. If you smile when you get caught you’re more likely to get off: Somehow we think that those who smile are really nicer people so we tend to be willing to treat them leniently.
3. It eases embarrassment: If you do something stupid like slip on a banana, or trip and fall in the middle of a mall, people laugh with (not at) you if you laugh or smile. That is, it changes their reaction so they’re less likely to mock.
4. If you smile with others when they share good news, you’re less likely to feel jealous or annoyed at them: Interestingly, even if we smile politely but we feel slightly annoyed, our emotion quickly changes and we feel happy ourselves. Somehow we feel much better for having chosen to be “nice”.