contagiousity (is that even a word?)

everyone knows germs are contagious, but did u ever realize that when you hear someone singing a song (or you may hear a song on the radio), you automatically start to sing along with the person singing. with no hesitation. you just do it. or what about when u see someone yawn, you yawn too. and chances are, even if you see someone lick their lips, you will too. we do all these things so easily and quite involuntarily. it just happens without us even giving thought to it. its actually pretty funny, contagiousity is all around us. but it seems as if some things that should be contagious, really arent! so heres a thought... why not add smiling to the list? or a hint of love in the form of a kind guesture. you know,  it just may make someone's day, or even their life. i mean, singing is fine and yawning is cool, but lets try making something that is significantly worthwhile contagious.