My definition of reduced empathy is when we cease to treat another person as a person, with their own feelings, and start to treat them as an object. But it could be reasonably asked: Don’t we all do this all of the time to each other? We enjoy a friendship because the person gives us something, we enjoy a sexual relationship because the person’s body is an object, we employ a person because they provide a service we need, and we might enjoy watching someone for their beauty or athletic grace. These all involve aspects of the person as an object.
My reply to this would be that if our empathy is turned on, then all the while we are treating the person as an object, we are simultaneously aware of their feelings. If their emotional state changed, such that they were suddenly upset, we would not just continue with our current activity, but we would check what was wrong and what they might need. If the friendship is based purely on what we gain from the relationship, such that we abandon the person when they are unable to still provide that, that would be not just a shallow relationship, but an unempathetic one. But I should qualify the definition of empathy by adding that the point at which we objectify another person while simultaneously switching off our sensitivity to his emotions is the starting point toward zero degrees of empathy. It is not the end point because as we have seen in the catalog of crimes that people commit, such a state of mind simply makes it possible to behave in more and more hurtful ways.
The Science of Evil
Simon Baron-Cohen 2011