IQ Tests and Measuring the Nonverbal Autistic Child

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Anyone who receives an IQ score of 70 or less on specific tests is labeled Intellectually Disabled (ID). ID, for readers who have not yet heard, is simply the new term for Mentally Retarded. Until relatively recently, it was assumed that most children with autism (and just about all nonverbal children with autism) were intellectually disabled for the simple reason that their IQ scores fell under (often far under) 70.

In recent years, however, it has become clear that typical IQ tests are very poor tools for measuring intellectual ability in children with autism--particularly when those children are non-verbal. The reasons are fairly obvious when you think about it. Here are just a few:

  1. IQ tests, for the most part, depend upon the test taker's ability to quickly understand and respond to verbal information. Non-verbal children with autism obviously have challenges in those areas that may or may not have any connection to basic intelligence.
  2. Most IQ tests require an ability to understand and respond to social norms and expectations, and to respond within a specific period of time--both of which are challenging to kids with autism, whether verbal or not.
  3. Sensory issues that don't cause issues for typical children may distract children with autism. Nonverbal children with autism don't have the ability to let testers know about such issues.
  1. Children with autism often have difficulty with transitions (especially unique and surprising transitions) and may need preparation in order to manage the new setting and relationship associated with IQ testing. Yet such preparation is rarely provided.
  2. Children with autism often have very strong "splinter" skills, so that sub-tests may be much higher than is suggested by the overall composite test number. But determination of ID does not take sub-test scores into account.
  1. Testers are rarely trained to work with, engage with, or "read" children with special needs -- especially children who are non-verbal. If they can't engage the child, it is very unlikely that the child will present their highest level of ability. 

Not only are these and related issues a concern, but it also seems clear that IQ tests are skewed in favor of people who are ethnically white. According to a 2014 CDC report: 31% of children with ASD were classified as having IQ scores in the range of intellectual disability (IQ ≤70), 23% in the borderline range (IQ = 71–85), and 46% in the average or above average range of intellectual ability (IQ >85). The proportion of children classified in the range of intellectual disability differed by race/ethnicity. Approximately 48% of non-Hispanic black children with ASD were classified in the range of intellectual disability compared with 38% of Hispanic children and 25% of non-Hispanic white children.

How, then, should IQ be measured among nonverbal children with autism? Ideally, the answer should include both non-verbal IQ tests and non-test-related observations. 

The TONI -- Test of Non-Verbal Intelligence -- is one example of a non-verbal IQ test that is usually a better option for non-verbal children and for children with autism in general.

Observation of non-verbal children in familiar settings can also provide evaluators with real-world information about abilities versus test-taking skills. Often, while non-verbal autistic children may fail to cooperate with or fully grasp the intent of standardized tests, they are quite capable of handling intellectual challenges such as solving complex math problems or puzzles.

Of course, neither school districts nor agencies are likely to accept the outcomes of these evaluations anytime soon, but research suggests that they are much more likely to reveal a child's true potential.


Baio, Jon, EdS, National Center on Birth Defects and Developmental Disabilities, CDC. Autism and Developmental Disabilities Monitoring Network Surveillance Year 2010 Principal Investigator

Bardikoff, N. et al. Testing nonverbal IQ in children with Autism Spectrum Disorders.Research in Autism Spectrum Disorders. Volume 8, Issue 9, September 2014, Pages 1200–1207

, . IQ scores not a good measure of function in autism. Spectrum News, 6 January 2011.

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