(http://www.all.org/pdf/McDonaldPaul2010.pdf) over at The Misbehaviour of Behaviourists (http://www.quicktopic.com/27/H/vJvhV4fDnBgw7) Michelle Dawson queries the article's assumption that "criteria for the specific diagnosis of autism have stayed about the same since 1978".
I fully appreciate that that claim's a bit dodgy, but I don't think that differences in diagnosis are an additional problem over and above the problem that the DSM-whatever criteria are so vague and ambiguous that if taken literally they vastly overselect. I mean, you might even accept that in Venn diagram terms the circle of "People who have autism" is entirely within the circle "People who fit DSM criteria for autism", but the difficulty is finding a way to check whether the expansion or contraction of either is particularly related to expansions or contractions in the other. Unless, of course, you take the view that autism actually is "whatever fits the criteria", without any further interpretive strategies.
Which then brings one up against the problems in assessing (say) "preoccupation with .. restricted patterns of interest that is abnormal..." when there are no measures attached, and if there were measures there would still be no documentation of how much 'preoccupation' falls within the normal range for three-year-olds.