Wednesday, January 28, 2009

Another article on Wechsler and Raven's with autism

For those interested in the research by Michelle Dawson and her group on assessing intelligence in autistics on the Raven's versus the Wechsler, I have just found out that one of the IMFAR abstracts that dealt with the issue of the Raven's in autistics has actually been published online. The article is here Though I may have beaten this issue to death somewhat lately, I was interested to find out that this was not just a conference abstract but an article that was actually available online, and I have just read the entire article and found it interesting. Testing was done on a group of autistic children and children with other disorders as well as typical controls. The autistic group scored higher on the Raven's than on the Wechsler. However, the high scores were just specific to the lower functioning group (lower functioning being defined as having a full scale IQ of less than 85) who scored about 20 IQ points higher on the Raven's than on the Wechsler. There was no difference between the two tests in the group of higher functioning autistics. I won't comment further but I just thought that everyone who, like myself, has an interest in the work the Mottron lab has done on intelligence in the Ravens versus Wechsler might like to read this article.

1 comment:

Anonymous said...

I read "The Level and Nature of Autistic Intelligence" by Dawson, Soulieres, Gernsbacher and Mottron.

This is an enterprising study, but it has flaws, so some of its conclusions are not justified.

Here are some technical problems. First, sampling. The autistic group has few females. (But it may be very difficult to get samples of autistics, so this flaw is understandable). But second, the autistic group was obtained in a quite different fashion from the comparison group. To draw conclusions from a comparison, the groups should be as similar as possible except the factor under study. If you have too many differences between the groups, it opens the results up to alternative explanations. For instance, in this study, if the control group had been composed of people going through testing for autism and diagnosed as neurotypical, that would be a much better comparison. Instead, they are folks recruited from a newspaper ad. That makes them different from the focus group in lots of ways.

Third, the control group is not "neurotypical" as claimed. It is a self-selected sample with an IQ of around 75th percentile (this applies to both the children and the adults.) Regrets, but 75th percentile of any distribution is never "typical."

The suspicion is that if the control group started out with an average (Weschler) IQ as low as the autistic group’s, maybe they would show the same odd pattern with the Raven’s too. Maybe not. And maybe people with a 75th percentile IQ are anomalous in other ways, because they are certainly another unusual group.

So this study is comparing one unusual group with another unmatched, unusual group. For sure, this makes it hard to draw deductions.

Fourth, the authors never explain what these IQ tests measure. (Not surprisingly, because psychology is agreed they measure some cognitive skills, but whether those skills translate into life performance is debated.) So, do the differences in IQ scores between Weschler and Ravens mean anything practical?

Dawson et al. go on to claim: look, the Ravens scores are higher, so the autistic subjects aren't dysfunctional after all.

Really? And what life skills do the improved Ravens score correlate with - ability to have a relationship, run a factory, sail a ship, or make rent? Probably not.

So that claim is odd. (I didn’t use the word specious.)

So where is the authors’ practical point? What do autistics gain by scoring better on the Raven's - more independence of life-style? Probably not. Basically, this study just discovers one more complexity in the cognitive patterns of autistics.

But in the debate around neurodiversity, that’s not how the conclusion is being used.

If the authors’ conclusion is not justified, but people use this study to back their policy recommendations and the future non/treatment of autistics, then they are running a risk of different dimensions.