Are IQ tests "biased" against individuals with Asperger's Syndrome? One person makes the claim over at his response to the Quora question Do people with Asperger's have above-average IQs simply because the ones with below-average IQs simply get diagnosed with autism instead?.


  No. 
  
  Intelligence testing as most neurologically typical people understand
  it, is heavily biased toward individuals with expressive and receptive
  language ability which is often impaired in persons with autism to a
  greater degree than in persons with Asperger's. 
  
  As an example: imagine an intelligence test that was written in
  English being administered to a person who grew up speaking French.
  That person might be quite bright but would likely score very low.
  There have been numerous documented studies of the effect of language
  bias in intelligence testing that makes the idea of standardized
  intelligence testing a questionable endeavor. 
  
  From personal experience, my own son has rather severe language
  impairments and, if tested with a written or verbal test, would almost
  certainly have an MR diagnosis in addition to his autism. However,
  when tested with strictly non-language based testing methods, has
  proven himself to be quite bright (in the empirical sense, that is.
  Watching him spend 30 seconds on a strange computer before finding his
  favorite YouTube videos shows that he knows quite well what he's
  doing). 


Is he right when he says that "Intelligence testing as most neurologically typical people understand it, is heavily biased toward individuals with expressive and receptive language ability which is often impaired in persons with autism to a greater degree than in persons with Asperger's."?

And could IQ tests be biased against Aspies in other ways? Could they also be biased in favor of Aspies in certain ways as well?
Depends which IQ test you use - individuals with ASDs show a typical "pattern" on the WAIS, which can cause it to appear like they have lower IQs. When tested with tests which aren't biased in this way, they appear to have the same IQ range as neurotypicals.

The assumption that those with an ASD are cognitively impaired pervades both popular and scientific literature - those who are minimally verbal or non-verbal (i.e. those who do not show fluency in their speech) are often labelled as ‘low-functioning’. The characteristic cognitive profile shown by the WAIS is commonly interpreted as a unified deficit known as ‘weak central coherence’, the tendency to focus on low-level details as opposed to the higher-level ‘whole’ (Happé, 1999). Much of the recent research regarding the neuroanatomical signature of autism relies on the untested assumption that cognitive strengths of autistic individuals as shown by the WAIS are nothing more than low-level by-products of high-level deficits. Dawson et al. (2007) have shown using Raven’s Progressive Matrices (Raven, Raven, &amp; Court, 1998), a complex yet general test of intelligence, that the WAIS severely underestimates autistic intelligence (by an average of 30 percentile points). It is therefore recommended that though the WAIS has a number of useful psychometric properties which can be applied in the diagnosis of autism, it is not used as a measure of intelligence in such populations.

References


Dawson, M., Soulieres, I. Gernsbacher, M., Mottron, L. (2007). The Level and Nature of Autistic Intelligence. Psychological Science. PDF
Happe, F. (1999). Autism: Cognitive deﬁcit or cognitive style? Trends
in Cognitive Sciences, 3, 216–222.
Raven, J., Raven, J.C., &amp; Court, J.H. (1998). Raven manual: Section 3.
Standard progressive matrices. Oxford, England: Oxford Psychologists Press.