Sociopaths have an extremely low level of empathy by definition, far on the end of the scale. Not all sociopaths are serial murderers. They do tend to be manipulative, however, seeing other people as part of a system to be optimized. Some, however, do become psychopaths. According to one study (which I can't find right now but will link to if I can dig it up), psychopathic behavior is driven by both genetic predisposition to sociopathy and environmental factors such as childhood abuse. From what I can recall, the paper said that genetic or environmental factors alone don't explain psychopathic behavior in the data - psychopathic behavior requires the combination of the two.
Then I saw this article:
Excerpt: "We found that a hyper-reactive dopamine reward system may be the foundation for some of the most problematic behaviors associated with psychopathy, such as violent crime, recidivism, and substance abuse.”
According to this article, it seems that the wiring of the dopamine system can be modified through environmental factors, such as substance abuse. It made me think: Is it possible that the dopamine system of psychopaths has been altered by a consistent pattern of abuse or trauma, that, when combined with genetic factors result in psychopathic behavior? Perhaps the body is responding to abuse or trauma by increasing the amount of dopamine, as a survival tactic.
I don't know the answer but I sent an email to Joshua Buckholtz, who did the research. Will post if he responds.