smiling - just a thought!!!

Was listening to an interesting radio interview with a guy who was talking about the way the brain works, our thoughts and how they affect our moods.  I was struck by a question he was raising about smiling:

Are you happy when you smile or do you smile when you are happy?

He was saying that the act of smiling can make you feel happy, which in my own experience I can recognise - I suppose if you are genuinely smiling it is difficult NOT to feel okay or even great!!!