I see the spectrum as a bit more complex, encompassing other non-empathic states of mind.
(Damn, I've got no photobucket account so I can't put up a nice diagram, so bear with me.)
Instead of just one spectrum running left to right, imagine a second one, going up and down.
In the middle is our old friend, the neurotypical.
------- Magical thinking ---------->
Extrovert:
PSYCHOPATH---------------BORDERLINE
In the middle:-----------
NEUROTYPICAL
Introvert:
AUTIST----------------SCHIZOPHRENIC
The horizontal axis is magical thinking. Do you perceive things precisely, from the outside, or vividly, from the inside? Is someone's smile a heartwarming experience, or just the tightening and loosening of face muscles?
The vertical axis is extroversion. Are your emotions turned on mainly by people (extrovert) or by the world that surrounds people (introvert)?
Putting these together, we get four divisions.
At the top are the extroverts. Psychopaths are fascinated by people, but can't see them as magical - just as another kind of animal. And that's how they tend to treat people. Borderlines are people persons, too, but have difficulty handling the intensely magical experience that comes with personal interactions.
At the bottom are the introverts. Autists are fascinated by the predictable patterns of nature, but tend not to see them as alive in any meaningful sense. Schizophrenics, however, find the entire non-human world magical. Trees and furniture talk to them. The clouds are omens. Even their own thoughts echo magically, as the voices of gods or demons.
Note that this is a very broad-brush picture. There may be other tribes of mutants. Tribes shade into one another, with some people having traits of more than one. And there's no clear line where they shade into the general population. However, a good benchmark is empathy. Can you look at someone and feel in your bones the same emotions as they're having?
Autists and schizophrenics feel no empathy, because most of the stuff that attracts their attention has no feelings to be read. Psychopaths feel no empathy, but give a perfect imitation of it. Borderlines feel no empathy, but have enormous sensitivity. NOTE! they are not the same thing. If you drop a microwave oven on your foot, you'll feel an enormous personal reaction to the oven. That does not mean you understand how the oven works.