I've heard it said that it's a combination of genes and enviroment, but that the parent providing the genes often also provides the environment.
Sociopathic traits exist on a scale, but it seems childhood trauma can exacerbated these traits. I know a child with traits, among them a facility with lying that is quite uncommon among small children. I think it would be easier for them to be a nice person if the adults in their life were more kind, and life was more predictable.
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I sometimes leave conversations and return after a long time. I am sorry about it, but I need a lot of time to think about it when I am not sure how I feel.