Portia Iversen explains that it is a misconception that the majority of autistic individuals are mentally retarded.
The literature about autism tells us that the majority, usually you see the number of 80%, of people with autism are mentally retarded. I don’t think this true and as a matter of fact, in the last couple of years a paper came out Maclean University that did a survey of every time this figure was recited in the literature and went to look to see if there was any empirical data and in the great majority of cases there wasn’t. It almost became, one paper would quote another that quoted another that quoted another, but there was actually no basis for this.
The truth is for at least half, if not more, of people with autism, we don’t even know how to test their intelligence because they have such severe communication problems.
So, no, I think that’s wrong, I think the majority of people with autism are probably not retarded. There are going to be a certain subgroup that are mentally retarded and that’s because there is a subgroup of autism, probably made up of many disorders. If you think about it, anything that could disrupt that critical period where you’re going to get in sync with other people, there are a lot of things that can do that, from epilepsy to an inborn error of metabolism to genetic disorders.