So, for many, myself included and apparently other infxs on here (and perhaps others too--not necessarily tying this with type yet), who have the very really experience of having physical expression of intense emotions, it would equate that if I'm experiencing the emotions of others (your empathy definition), that I'm personally having a physical manifestation of that. Which is why I define extreme empathy, for my own experience, as having physical manifestation of the state of another.
Please keep in mind I am attaching no meaning to this concept. Not saying it's good or bad necessarily. Just trying to get the definition straight at this point.
Since empathy involves understanding the emotional states of other people, the way it is characterized is derivative of the way emotions themselves are characterized. If, for example, emotions are taken to be centrally characterized by bodily feelings, then grasping the bodily feelings of another will be central to empathy. On the other hand, if emotions are more centrally characterized by a combination of beliefs and desires, then grasping these beliefs and desires will be more essential to empathy. The ability to imagine oneself as another person is a sophisticated imaginative process. However the basic capacity to recognize emotions is probably innate and may be achieved unconsciously. Yet it can be trained, and achieved with various degrees of intensity or accuracy.
The human capacity to recognize the bodily feelings of another is related to one's imitative capacities, and seems to be grounded in the innate capacity to associate the bodily movements and facial expressions one sees in another with the proprioceptive feelings of producing those corresponding movements or expressions oneself. Humans also seem to make the same immediate connection between the tone of voice and other vocal expressions and inner feeling. See neurological basis below.
Stretching now: If we were all more empathic, would we have some sort of influence on antisocial behavior in a negatively correlated way> Might discourage antisocial behaviors which would lead to more harmonious environments.