Just a thought this morning, but I think the “autism spectrum” would be better characterized as a “matrix” with intelligence running along one axis and impairment on the other.
We can divide this into four useful quadrants, representing high IQ & high impairment, high IQ & low impairment, low IQ & high impairment, and low IQ and low impairment.
Of course these are not entirely unrelated measures–the impairment that causes autism can also cause low IQ, but it makes a functional distinction because different quadrants suffer different challenges and limitations.
The traditional distinction was between “autism” and “asperger’s,” with asperger’s generally reserved for the smarter, higher functioning kids. Asperger’s has been dropped as a diagnosis due to this distinction being not the most useful–there are high-functioning dumb kids with autism and low-functioning smart kids. (And adults.)
Just a little thought.