We have all heard these platitudes: "just put on a happy face" or "turn that frown upside down."  Can the simple act of smiling actually make us feel better?  Might we even become addicted to smiling?  The answer may have everything to do with the evolution of the frontal facial bones and that popular feel-good neurotransmitter dopamine. Our face is formed by a variety of rather thin bones that are made somewhat fragile due to the presence of large air pockets called sinuses.  The muscles that attach to these bones contract when we are happy or when we want to laugh.  The resulting facial expression is universally recognized as a smile and indicates our positive emotional status.  Sometimes, people present fake smiles; these can also be universally recognized as being counterfeit. 

We can all tell the difference between a real smile and a fake one.  When we see someone showing a fake smile we know they lack sincerity in what their faces is trying to convince us about their underlying true emotions.  But how does the brain achieve both types of smiles using the same facial muscles?  It all depends upon which part of the brain initiates the smile.  If the brain's dopamine neurons initiate the smile, then the smile looks sincere.  If the brain's motor cortex initiates the smile, i.e. if we are consciously willing ourselves to smile, then a slightly different set of facial muscles are activated.  It can be difficult to describe precisely how real and fake smiles differ, but we are all very capable at knowing the difference.  But can forcing yourself to smile produce the same kinds of good feelings as a real smile does?