I have spent years wondering if I am autistic, even though I have a Theory of Mind and can pass for neurotypical in many social situations. For one thing, I have a number of other issues that are often labeled autistic, such as attention deficiency, dyspraxia, hypersensitivity, and an approach based on living in my mind and dealing with the world, rather that living directly in the world. Rebecca Burgess shows us that a spectrum is not more-or-less, the way the autistic one is usually described.
Almost forgot: This post on Status 451 seems to cover some of the same questions. (Technical math terminology warning. And I am perversely amused by a measure of autism based on the mathematics of Paul Dirac.)