I don't know, because I show so many of the factors that have at one time or another been theorized. Technically, I'm an Aspie, if that matters.
Let's see... Dad's on the spectrum, check. I was late, check. Stressful birth, check.
The earliest evidence for my being atypical is neither worrisome nor conclusive, but as a baby, I wouldn't cry, and I gave myself a mohawk by pulling out my hair.
Further evidence occurs in early childhood, when I had difficulty perceiving that someone had greeted me, and was very shy around non-family. I usually preferred solitary play, although it was often pretend play. I had my first special interest then, too. It was dinosaurs. I wonder what percentage of children, both on and off the spectrum, are obsessed with dinosaurs when they're five. It's probably very high. That may be the last time I was ever typical.
Yes, I was vaccinated, and yes, they contained mercury, and yes, my mother blames the vaccines.
So we see that I was probably always like this, although we can't know for sure.
However, I also demonstrated definite tendencies toward extraversion. Not to a huge degree, but I valued my friends and liked playing with other kids. I sought out such experiences.
However, I had to change schools a couple of times. No group of children ever accepted me after third grade. I was homeschooled following that, and essentially never left the house. I had very little social contact.
Following this period, we find that I am much more introverted and have fallen further behind my peers in social skills, although I understand relationships better than before. I credit some of my most significant improvements to videogames.
So there you have it. Theoretically, it could be due to any of these factors. Dad remains convinced that I got it by reading about it. Mom remains convinced that that's how I developed stims. (In a triumph of common sense, she blames my touching everything on watching Monk, which I didn't start doing until after I started touching everything. It is true that I never rocked until after I'd read about it, but rocking is a vestibular stim, and I had a different vestibular stim-- spinning-- before, which has been entirely extinguished.)
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I'm using a non-verbal right now. I wish you could see it. --dyingofpoetry
NOT A DOCTOR