http://en.wikipedia.org/wiki/Pathos The ancient greeks were right about lot of things, that's for sure. Also, this was something I heard on NPR recently, putting this phenomenon in layman terms. "If we stated how many children in Africa died of starvation or disease today, what would be your reaction? Would you really care? What if we filmed a documentary or film, following only one child and his attempts to survive, which ultimately fail? Wouldn't that get you to cry?" the human brain is so imperfect in the most beautiful way.. We're not and will never be truly logical or analytical. EDIT: for instance, the human brain thinks logarithmically while a true AI might not.
That emotional response is why the Kony 2012 campaign worked so well, as the director was taking advantage of our willingness to hear sad stories of Kony's horror