The best analysis of all of this stuff that I have seen is from high to low functioning:
Introvert: We all know what this is, can function markedly well ->
Severe Introvert: Possibly odd but can be robustly healthy psychologically otherwise ->
Schizoid Personality Traits: Some coldness, apathy, distance re: human relations and lowered sex drive, otherwise can function very well, reduced functioning ->
Schizoid Personality Disorder: Marked coldness, apathy, and distance re: human relations and strongly lowered, apathetic, confused and baffled sex drive, “something is off about them but you can’t put a finger on it because they seem otherwise healthy,” otherwise some can function extremely well ->
High-functioning Autism or Asperger’s: Something seems very much off, possibly just looks like extreme introversion with marked anxiety but others can appear markedly normal and the condition only becomes noticeable after a few hours with them, problems with excessive seriousness, “sciency” type explanations for emotions, emotions seem off, some flapping, etc, baffled by human emotions, somewhat robot-like behavior, rocking motions, baffled by social skills, do odd things that violate social rules because they don’t understand them, possible gender identity confusion, often denies or minimizes their condition, can have strong sex drive, many females) ->
Medium functioning Asperger’s/Autism: Very weird, something is extremely off, can still function well at certain jobs, often low sex drive and desire for human relations, can be distracted by say a strobe light to where they seem to be entranced, weird ordering rituals with objects, very robotic to the point of being un-human or android-like, possible gender identity confusion, often male ->
Lower functioning autism/Asperger’s: Can still work, maybe a computer job for family, nonexistent friendships, sex drive or romantic partners, keeps asking the same question endlessly in an obsessive fashion, strange to the point where they need help understanding stoplights, severe meltdowns, possibly dangerous or criminal at times, markedly “nerdy,” something very clearly off about them, sex drive retained, possibly sexual orientation or gender identity confusion, some simply cannot work or live on their own at all. ->
Nevertheless, all Aspies often display a strong core of human feelings. Can get their feelings hurt. Capable of righteous anger, sense of pathos or tragedy about situation, in other words, there are times when you realize that they are just as “human” as any of us, and they can seem sad or tragic at these times.
“Pure autism” category: Appear mentally retarded, strong decline in intelligence/IQ, marked repetitive actions, cannot function or work, must live in group homes and have things done for them, nevertheless, a hard core of human awareness such that they can tell if you are ignoring them or not being nice to them and they get their feelings hurt, desire for human action, strange, retarded-like speech, weird body movements.