A reader asked me how a sociopath could seemingly feel one way about something one day and feel something entirely inconsistent another day. I responded:
Sociopaths seem to be exceptionally good at compartmentalizing, which would explain why it is possible for him both to have cared (and perhaps still care) for you very much but seem to not be at all interested in you now. A good way for normal people to understand the extent to which this works is to think of a vivid dream, perhaps an anxiety dream in which you dream of things that need to happen, projects that need to get done, problems that need to get solved. During the dream you get very caught up in the urgency of things, whatever it is that you are dreaming about becomes very important to you, you can't imagine a world in which this was not a primary concern for you. When you wake up from the dream there are still lingering feelings of the dream. Perhaps you just have the feeling that you need to do something, or maybe you actually remember specifics of what you supposedly "need" to do. Within the first fifteen minutes or so of wakefulness, however, you eventually realize that it was just a dream, that you really don't have to worry about those things at all, and so you continue living this other life and quickly forget about the dream life. That is how much sociopaths can compartmentalize. The dream world never fully goes away, maybe they remember some of it, or something will remind them of it, but for the most part it and the feelings felt are a faint memory. Those feelings associated were "real" in that they reflect how the sociopath would feel under the circumstances of the dream, but those circumstances just turned out not to be true.
I wonder whether the mechanism of compartmentalizing for the sociopath is the same as the mechanism that allows people with multiple personality disorder to have separate personalities each living essentially independent lives, sometimes unaware of each other.