Robert Hare's Without Conscience is probably the best book commonly available on psyopathy. I'd been curious as to whether or not there actually was such a thing or whether it was just a term which was overused and badly defined. It turns out the concept is sufficiently real.
I noticed on page 44 of Hare's book:
And something pretty much just clobbered me over the head in that I've read that same sort of language before in Julian Jaynes' description of the development of the ability to "narratize" or form mental images of sequences of events.Many of the characteristics displayed by psychopaths -- especially their egocentricity, lack of remorse, shallow emotions, and deceitfulness, are closely associated with a profound lack of empathy (an inability to construct a mental and emotional "facsimile" of another person). They seem unable to "get into the skin" or to "walk in the shoes" of others, except in a purely intellectual sense.
Naturally enough, Hare notes that sort of thing is also a problem for psychopaths; he notes that they have difficulty visualizing consequences and keep on doing things which they know will produce bad consequences for themselves ("that's tommorrow, this is today") and that they frequently make statements in which a second part of a sentence will contradict the first part etc. Hare assumes some sort of a left brain/right brain thing is involved, i.e. some sort of a problem of who's in charge of the computer, and that's precisely the sort of thing which Jaynes was talking about.
My own thoughts are that in an age in which consciousness was planetary and not individualized and the other person's "ka" was right there to let you know how they felt about something, the kind of modeling ability which Hare speaks of as missing in the psychopath would not be necessary.
In other words, the thing missing in a psychopath would be some new feature which the human race had developed very rapidly and out of dire necessity, after the breakdown of the bicameral mind.