It was widely accepted that emotion such as fear, anger and pleasure could not be studied using a modern scientific tools. During the very early periods of emotion researches, psychologists, but not biologist, dominated in studying emotion and its disorders. Intuitively, one may think that emotion arises from brain first and then bodily responses follow. For example, we are sad first, and then cry. However, groups of psychologists suggested a proposal that our feeling follows bodily responses; that is, we feel sad because we cry! This proposal seems counterintuitive but became a popular hypothesis for emotion. Another example for this hypothesis is as follows. When you accidentally confront a large bear in a mountain, what would be your responses?; you may feel terrified first, and then run, or you may run first, and then feel terrified later on. In fact, the latter explanation is correct! You feel fear after you run (even because you run?). Or, you can imagine that you date with your girl friend who you love so much. Your heart must be beating fast and your body temperature must be elevated! In this situation, if you take a very cold bath, what would you expect? Your hot feeling is usually calmed down after this cold bath; that is, you feel hot because your heart and bodily temperature change. While some evidence supported this hypothesis, others do not. In the case of patients whose cervical vertebrae were severed with an accident, they still retained significant amount of emotion (feelings!) in some cases (but other patients lost most of emotional experience). In addition, one can imagine that there would be a specific set of physical responses for specific emotion if the original hypothesis is correct (e.g. fasten heart beating and redden face for anger etc.). However, some psychologists failed to find any specific set of physical responses for specific emotion, though others insisted that there existed such specific responses. Based on these controversial observations, another hypothesis was proposed; that is, we feel first, and then have physical responses. These two hypotheses seem contradictory to each other, but detailed examination on these hypotheses waited for the development of new analytical tools.