Vampires!

I have a long-time interest in folklore, including vampires. For a fantasy novel in progress I have come up with what I think is a novel explanation of the whole "undead" thing. My vampires are living creatures (not an uncommon premise in itself) but because the process of becoming a vampire burns out most of the human social instincts they give the impression of not being truly alive.

Think about it. When you are talking with someone both of you are making small movements, non-verbal noises, with all sorts of instinctive social cues flowing back and forth between you.

Now, imagines you're sitting with someone who only speaks - only makes a _sound_ - when they have a conscious reason to. Who makes none of the little social movements, no gestures no twitches, but just _sits_ there. Barely breathing. Occasionally blinking. Otherwise still as a corpse. You might not consciously notice what was wrong, but you would definitely think something was wrong. Even a social klutz like me would find that unnerving.

My vampires can learn to mimic these social instincts, but doing so well enough to pass as human for more than a casual encounter requires enormous effort. It doesn't become second nature without centuries of practice.

Does this idea work?

Does it resemble some extreme forms of autism, or some other brain-function disorder?