That question is what I thought about 4 years ago during my family pictue when the photographer and my mother asked me to smile and I asked why and they both said it means happiness and brings you joy well if so I did smile and I was not any more happier than the minute before I smiled . Is it that people demand a smile in photograhs to display the false feeling of joy and hapiness. Well some author that I don't know the name of once said a smile confuses an approaching frown well, that may apply externally but internally you still are frowning. And about the happiness "the grand essentials in this life to it are something to do , something to love and for something to hope for." I guess what I am trying to say is that if a simple action such as smiling is supose to make you happy why am I not ,I guess that's a question we all will never know the answer to. So smile if you think it will make you happy and to the people like me just look for " something to do, something to love and something to hope for" and let's see if it will truly make us happy. Oh and about the main question what does a smile reveal,anything you want to.
PEACE AND LOVE
PRIMADONNA