macloudt - I bet if you watch your son's movements closely, that he does exactly the same sequence of movements again and again and again, moving along the rows in an orderly fashion, reflecting the fact that the solution is pure repetition rather than insight. It's even possible that his autism may have helped him spot this fundamental computational pattern quickly!
Definitely. Like a lot of autistic kids his spatial reasoning is very good, as is his memory. Also his visual processing ability is faster than average, another reason why he can do these puzzles so quickly. Never ceases to amaze me, this kid.
