This is how one of my recent articles begins. It took me a long time to be able to put down in writing "WHY" I personally find research on emotion so fascinating and challenging. This, of course, is probably just a very small part of the "WHY", but it summarizes my thoughts (at the moment) on the matter. So... here is goes :)...
"Research on emotion dates as far back as human civilization, each period giving a distinct explanation and interpretation to the diversity of sentiments [Oatley, 2004]. Moreover, each society used these clues for the definition of social norms, for the detection of anomalies, and even for the explanation of mythical or historical facts (e.g. the anger and wrath of the Greek Gods, the fear of the unknown and the Inquisition in Middle Age, the romantic love in Modern Times) [Ratner, 2000]. The cultural representations concerning emotions are generally ambivalent [Goldie, 2000, Evans, 2001, Oatley et al., 2006]. Emotions were praised for their persuasive power, but also criticised as a “weakness” of the human being, that should ideally be rational. Modernity and the development of technology applied to different fields of science has proven that emotions are given by a compound of biological, neuronal transformations and are the root of all human reactions [Scherer, 1987, Scherer, 2001, Scherer, 2005] and decisions [Goleman, 1995].
Recent studies in Artificial Intelligence have shown that approximations of emotional response outperform the modeling of rational decision making [Jiang and Vidal, 2006]. Studies in neuropsychology [Cytowic, 1989] showed that perception is happening not only in the cortex region of the brain (linked to rational processes), but also below the cortex, in the limbic system, which regulates emotion, memory and attention and helps determine valence (i.e. whether we feel positive or negative about something) and salience (what gets our attention) [Picard, 1997]. For all these reasons, the study of emotion has been an important and challenging research topic around which different theories have been developed in many fields."