June Gruber in Edge:
I thought I'd first start briefly with a tale of positive emotion. It's a really interesting state because in many ways it's one of the most powerful things that evolution has built for us. If we look at early writings of Charles Darwin, he prominently features these feelings of love, admiration, laughter. So early on we see observations of them, and have some sense that they're really critical for our survival, but when you look at the subsequent scientific study of emotion, it lagged far behind. Indeed, most of the research in human emotion really began with studying negative emotions, trying to build taxonomies, understand cognitive appraisals, physiological signatures, and things like anger, and fear, and disgust. For good reason, we wanted to understand human suffering and hopefully try to ameliorate it.
More here.