Psychologists have long pointed to the evolutionary need for negativity. But positive emotions? They chalked them up to the mechanics of mating and moved on. “That could not be the whole story,” said Barbara Fredrickson, UNC’s Kenan Distinguished Professor of Psychology. “There had to be an adaptive function beyond reproduction.” Twenty years of emotions research later, her bestselling book, "Positivity," makes a solid claim: not only do we need positive emotions to survive — we need them to flourish, to survive well. [courtesy of www.unc.edu]