Well, as far as I know, metal retardation and autism are two different things. The first have a low IQ (although it's probably not as simplistic as that). Autists have a problem communicating, expressing themselves. (and not all of them have autism to such an extreme degree as that girl)

There are plenty of intelligent, less intelligent and even brilliant people with autism (although not in the classical sense, given their flaws) . I remember seeing this docu about an autistic guy who could draw an almost exact map of a huge part of Rome (Pantheon, Colosseum, etc...) after just seeing it once from a helicopter.

[video=youtube]http://youtube.com/watch?v=jVqRT_kCOLI[/video]