People smile involuntarily when they feel affection, cute or pride.
Smiling involuntarily means the corners of the mouth are turned up. It does not necessarily include showing teeth.
Affection makes people smile when they see a loved one or old friend. Cute makes people smile when they see babies. Pride makes people smile when they win a contest.
People are generally comfortable with affection-smiling and cute-smiling, but not pride-smiling. Contest winners, for example, will often hide their pride-smiles with their hands.
Affection-smiling and cute-smiling often become laughter. People often smile and then laugh, for example, when seeing old friends or babies despite not feeling humor. Laughter seems to be a natural progression from smiling.
Seeing affection-smiling and cute-smiling makes people feel affection.
Affection-smiling is caused by affection and causes affection. When people see familiar people and feel affection, they smile. When familiar people see them smile, they feel affection and smile back.
Cute-smiling is caused by cute and causes affection. When people see a baby, they feel cute and smile at the baby. The baby sees the smiling, feels affection and smiles back at the adults.
Seeing pride-smiling makes peers feel envy.
When winners smile they make their fellow contestants feel envy. Their smiling is unavoidable proof of the higher rank which also makes envy unavoidable.
People also smile voluntarily.
If you look closely at someone's face, you can usually intuitively tell whether a smile is involuntary or voluntary. We describe a voluntary smile as a salesman's smile.
People smile voluntarily to pretend they feel a positive emotion or to say yes without using words.
Smiling is not a good indication of what others feel.
If someone smiles, you don't know if it's voluntary or involuntary. Even if you know it's involuntary, you don't know which emotion caused it - affection, cute or pride. A friend maybe smiling because he is pretending to be happy, feeling affection from being with you or feeling pride thinking about his promotion.
Smiling is a good indication of what you feel.
You know if your smiles are voluntary or involuntary. If you smiled involuntarily, you either felt affection, cute or pride. By recalling what you were thinking about when you smiled, you can identify which emotion caused it. If you were focused on a friend, it was affection. If you were looking at a puppy, it was cute, If you were looking at your new shoes, it was pride.
Understanding what makes you smile involuntarily can help you identify moments of happiness to replicate.
For more about emotions, visit: Happiness Dissected