Scenerio 1:
The soul is an immortal being living behind time. It might just stay there looking blankly in the space but thats pretty boring, isn't it? So it chooses to limit some of its senses and incarnate. At first it might choose common, easy lifes but soon (remember, it is an immortal soul, it can repeat a live milions of times) it will get bored with that and decide to try something else. Then it gets born as an aspie or any other sicko/wierdo.
Scenerio 2:
The soul spent a lot of its past lives on another planet. The environment, the social rules were other there, the soul got used to it. Then it is sent to be born on Earth. The soul is naturally attracted to the body with genes that remind it of the race it was before so it incarnates there, changing the body even more when the body grows (it's not like a body is independed of the mind). Then an aspie is born. An alien soul in unusually developed but still human body.
Scenerio 3:
The soul wants to research human interactions. You can't do it if it comes naturally to you because you won't even realize it is something unusual so you won't pay attention. So it is born an aspie - lacking the natural social ability. Now it can learn about the human interactions without preconceptions.
Scenerio 4:
The soul is sick of social interaction. Maybe it got badly hurt in the past live by other people so it decided to not longer care about them. "And the easier way to not care about other people is not being able to see their emotions on their faces" - it thought. So it incarnated into an aspie.
Scenerio 5:
The soul was hurting people badly in the past life by intentionally playing with their emotions. So, thanks to the Karma it is now unable to show its own emotions and understand/manipulate others even if it wants but is easy to be manipulated by others.
Scenerio 6:
The soul hurt an aspie in the past life. So thanks to Karma it is also an aspie now.
BTW. I believed in reincarnation for some time and I even made an afford to "see my past lifes".
- My 1st life on earth was in ancient civilization (I can't identify which one: priests wearing red gowns and people believing in bird-faced gods). I was a son from the ruling family and died about 20 year old. My coffin had bird-face on it.
- My 2nd life was a short one. Victorian Era, rich family. I died as a baby(boy) in my crib. I was genetically sick, my head was too big for my body. I was lying there, dead and my sisters and brothers were playing in the same room, thinking I am just sleeping.
- My 3rd life was a long one. I died as an old man on a comfortable chair in his home library. It was 19/20 century. There was noone around. I never started any family.
- My 4th life is now. I'm first time a woman.
Of course I don't give it too much thought. It could be just a dream.