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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?.


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?

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Considering people with Asperger's generally have higher than average IQs I rather doubt there's a bias against them. It's possible, but doubtful. IQ tests have evolved over decades to exclude cultural artifacts in questions. –  Ben Brocka Jan 20 '12 at 18:02
I actually suspect, though, that the lower-than-average IQ Aspies simply get diagnosed with autism instead, which could explain why Aspies have higher-than-average IQs. In fact, I suspect that this might be a major reason why they're considering merging Asperger's Syndrome with high-functioning autism in the DSM-V. –  InquilineKea Jan 20 '12 at 22:03
Anecdotal I know, but no, I don't think IQ tests are biased. I was diagnosed with ASD early on in life. And I passed the Mensa IQ test on the first attempt and am now a member. –  Global nomad Jun 8 '12 at 7:45
Just a note: The fact that you passed the test does not necessarily mean that the test is not biased against you. The bias would just result in lower scores, which nevertheless can be higher than the Mensa inclusion criterion. –  H.Muster Jun 8 '12 at 9:33
AFAIK Mensa tests are written so that they are not biased towards native speakers –  FolksLord Jan 30 '13 at 20:43

1 Answer 1

up vote 8 down vote accepted

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, & 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.


  • 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., & Court, J.H. (1998). Raven manual: Section 3. Standard progressive matrices. Oxford, England: Oxford Psychologists Press.
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Raven's is not an IQ test per se, but a measure of fluid intelligence. Can you explain how we can infer how much the WAIS over-/underestimates a population's score based on their results on Raven's? –  Christian Hummeluhr Mar 29 '13 at 6:45

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