Everybody isn't naturally emotional. Some people are more emotional than others, though it doesn't mean either is more or less compassionate, empathetic or otherwise. Some people just simply don't experience emotions at the same level as others, or they experience different emotions. A majority of males will express emotion through anger. A majority of females will express emotion via crying. Both are in fact incorrect, because emotion should be expressed by understanding of the feeling. Responses are just that, responses. They have a time and place, which isn't just for the sake of it because you feel something so you get angry or start crying.
You can learn emotion. You do it by looking up emotions and then learning their meanings. You can't often express a feeling because you don't understand what it is you're feeling. When you understand what an emotion is specifically, you can then identify that understanding with what is going through you head, then put it into a single emotional term.
You would be surprised how many people screwup emotion as it is... they think they know what they feel, but feel other.