Laughing lessens the risk of a heart attack.

Laughter Really Contagious, According to New Study

A new study found that the brain responds to the sound of laughter and preps the muscles in the face to move in a way that corresponds to the sound. Researchers played a series of sounds to volunteers and measured their brain responses with an fMRI scanner. All the sounds triggered responses in the premotor cortical region of the brain, but the response was much higher for positive sounds like laughter, suggesting they are more contagious than negative sounds.More on the subject...