I’m wondering how common it may be for people to misunderstand autism as some form of intellectual disability. To the extent that someone were to misunderstand autism in this way, we might predict that he or she would find it hard to believe that a given autistic person actually has any sort of disability at all, given the lack of an intellectual one.
I suppose the argument would look something like, “Mr. Autistickish may have autism, but he clearly does not have any sort of intellectual disability, therefore he’s not disabled.” Such a conclusion may seem especially warranted if the skeptic believes the commonly held false belief that mere intellectual prowess (a.k.a. “intelligence”) — is the beginning and end of successful achievement.
According to a 2008 study by the Center for Disease Control, it does appear that some 38% of autistic children also have an intellectual disability, which suggests that if all you know about a person is that they are autistic, and you simply guess that the person also has an intellectual disability, you’d be correct about 38% of the time, and those aren’t terrible odds. But it also implies you’d be wrong 62% of the time, which is to say that autism predicts normal to superior intellectual functioning much more often than not.
The upshot here is that autism — however often it may be associated with intellectual disability — is not at all the same thing.