Experts generally agree that there is no single mental condition called autism. Rather, there is a spectrum of autistic disorders, with different forms of autism taking different positions on this spectrum. But in certain circles of the autism community, this concept of a spectrum is being questioned. If differences in development are purely a function of differences in skill acquisition, then attempting to distinguish between degrees of severity may be dangerously misleading. A person may be subjected to unrealistic expectations, or even denied life-saving services, based solely on very superficial observations made by others in the community.
In the 1940s, Leo Kanner and Hans Asperger, working independently in the United States and Austria, identified essentially the same population, although Asperger's group was perhaps more "socially functional" than Kanner's as a whole. Some of Kanner's originally identified autistic children might today get an Asperger syndrome diagnosis, and vice versa. It is a mistake to say that a "Kanner autistic" is a child who sits and rocks and does not communicate. Kanner's study subjects were all along the spectrum.
Traditionally, Kannerian autism is characterized by significant cognitive and communicative deficiencies, including delays in or lack of language. Often it is clear that these people do not function normally. On the other hand, a person with Asperger's will not show delays in language. It is a more subtle disorder, and affected people often appear only to be eccentric.
Researchers are grappling with the problem of how to divide the spectrum. There are many potential divisions, such as autistic's who speak versus those who do not, autistic's with seizures versus those without, autistic's with more "stereotypical behaviors" versus those with fewer, and so forth. Some researchers are trying to identify genes associated with these traits as a way to make logical groupings. Eventually, one may hear autistic's described as being with or without the HOXA 1 gene, with or without changes to chromosome 15, etc. Leo Kanner identified another form of autism around the same time as Hans Asperger.
Some clinicians believe that communicative or cognitive deficiencies are so essential to the concept of autism that they prefer to consider Asperger's a separate condition from autism. This opinion is a minority one. Uta Frith (an early researcher of Kannerian autism) has written that people with Asperger's seem to have more than a touch of autism to them. Others, such as Lorna Wing and Tony Attwood, share in Frith's assessment. Dr. Sally Ozonoff, of the University of California at Davis's MIND institute, argues that there should be no dividing line between "high-functioning" autism and Asperger's, and that the fact that some people do not start to produce speech until a later age is no reason to divide the two groups because they are identical in the way they need to be treated.