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Are IQ Tests Really Useful When Evaluating A Child With Autism?

October 2, 2023

Standardized cognitive testing is a complicated subject when it comes to assessing children with autism spectrum disorder (ASD). Their social, communication, sensory and behavior problems compound the difficulties in administering a standardized measure.

Are IQ Tests Really Useful When Evaluating A Child With Autism?

The tests rely heavily on the subject’s language skills, ability to interact with others, motor planning and execution, and behavioral regulation. Typically, the assessor is a person the child does not work with or know. As a child with autism tends to thrive on the familiar and predictable, the novelty of the testing situation may create anxiety and significantly compromise the results.

The first modern IQ test was developed by a French psychologist, Alfred Binet, in the early 1900s with the purpose of identifying children who needed special education support. Standardized testing became a common practice in identifying individuals with mental impairment. The heavy reliance on a single IQ quotient to determine one’s true potential continues to be a controversial topic in the scientific literature.

Individuals possess many different types of intelligence, some of which are not measurable or quantifiable. Standardized IQ testing utilizing common tools such as the Wechsler scales or Stanford-Binet, may be a good predictor of academic success in more typical learners. This type of measurable intelligence assesses a person’s ability to solve novel problems, think abstractly, plan, reason, and learn from their environment. The validity and reliability of these measures to predict academic outcomes are less clear in individuals with autism.

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In addition to IQ measures, a determination of intellectual disability always includes assessing a person’s adaptive functioning or skills necessary to function in everyday life, such as communication, social skills, personal care, and overall independence. Oftentimes, individuals with autism, including those who attain high scores on the cognitive measures, experience significant deficits in adaptive functioning. For example, a person with a high IQ score on a standardized measure may struggle with day-to-day activities, such as personal hygiene, interpersonal skills, or balancing a checkbook and meal preparation.

The commonly used labels of “high functioning” and “low functioning” may be misleading and confusing for that very reason. An average to above-average IQ score does not encompass the global functioning or reflect some of the daily struggles of the “high functioning” autists, who may have difficulty holding on to a job, paying bills, or establishing and maintaining interpersonal relationships. Similarly, nonverbal children with autism may not have the means to express what they know and end up with the label of “low functioning.”

Historically, there has been an increase in IQs reported by researchers in individuals with autism. This trend appears to be due to better measures and understanding of the confounding factors that interfere with the actual test-taking. The difficulties associated with autism include communication and social deficits in addition to repetitive and stereotyped patterns of behaviors, interests, and activities.

These characteristics of autism influence not only the IQ score but also the person’s ability to participate in the standardized assessment. Up until the late 1990s, the research indicated that only about one-fifth of autists functioned in the “normal range” of intelligence. A more recent study conducted in the US in 2014 indicated that less than a third of the children with ASD had a comorbid intellectual disability.

In a landmark study conducted by Dr. Laurent Mottron and associates, individuals with autism were assessed using two measures of intelligence, The Wechsler Intelligence Scale for Children-Third Edition and Raven’s Progressive Matrices. The children with autism scored on the average 30 points higher on the Raven’s Matrices than on the Wechsler scale, whereas the typical children attained similar scores on both measures. The study replicated with autistic and non-autistic adults yielded similar findings.

The data addresses not only the level but also the nature of autistic intelligence. The Raven’s Progressive Matrices measures ‘fluid intelligence’-the ability to think and reason abstractly and solve problems that are considered independent of learning, experience, and education. The study questions the assumption of a “simple autistic intelligence” that used to dominate the scientific literature.

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In my experience as a school psychologist, I have assessed many students with autism utilizing both verbal and nonverbal measures of intelligence. I have found that many students’ IQ scores change with their age. Typically, they attain higher scores as they get older. Some of the changes may be due to their progress in the language, social and even test-taking skills due to the interventions provided and time spent in school. I have found that in some instances, IQ scores are not always accurate predictors of academic functioning in students with ASD. Some of the students function better academically than what the IQ scores would predict.

The standardized IQ measures appear especially inaccurate in assessing students with major language challenges. Even when being administered the nonverbal tests of intelligence, many of these children experience discomfort, confusion, anxiety, motor planning, and sensory challenges. Typically, these students perform better with familiar adults, in a sensory-friendly environment, and when working for incentives.

Oftentimes, anecdotal data including observations, teacher and parent input, and actual classroom performance may provide a more accurate estimate of ability than standardized testing. It is important to understand the child’s growth over time versus using statistical comparisons to the typically developing peers. Youngsters with autism tend to follow their own developmental trajectories that do not reflect the typical development. Students who do not have appropriate communication and language support are unable to express what they know. Addressing these students’ communication needs and providing access to a robust language system needs to become the top priority.

The scientific literature on the topic of measuring intelligence in autism, including the most recent studies, questions many stereotypes and assumptions that undermine the often hidden and not easily measurable potential in individuals with ASD. Standardized measures of intelligence so commonly used in the schools and by the private practitioners, may have undesirable and unintended outcomes for children with ASD, including underestimates of ability. The inaccurate estimate of learning potential can lead to low expectations or inappropriate educational placement of students.

The results of any standardized assessment with this population of learners need to be interpreted with caution so that they do not hinder access to appropriate educational opportunities. An IQ measure in and of itself should never be used alone in assessing overall ability or in educational planning. Information and data need to be collected over time, from different sources, and across different environments and include informal data such as observations in different settings, information from parents and providers, and informal and functional assessments of what the child demonstrates in his/her day to day functioning.

The objective of any evaluation process is to gain helpful, valid, and reliable information and glean a better understanding of an individual’s current needs, strengths, and challenges. The professionals, educators, and parents need to be aware of the limitations of standardized IQ testing in individuals with ASD. A low IQ score that could be invalid should never become an obstacle to a child’s educational prospects, lower the bar of expectations, or limit the child’s access to appropriate opportunities. Everyone responsible for educating students with autism needs to presume competence, raise the bar high, and provide appropriate supports to enable the students to reach their full potential.


  1. Duncan, A. W. & Bishop, S.L. (2015) Understanding the Gap between Cognitive Abilities and Daily Living Skills in Adolescents with Autism Spectrum Disorders with Average Intelligence. Autism, 19(1): 64-72.
  2. Sarris, M. (2015) Measuring Intelligence in Autism. Interactive Autism Network at Kennedy Krieger Institute
  3. Dawson, M., Soulieres, I., Morton, A. G. & Mottron, L. (2007) The Level and Nature of Autistic Intelligence. Psychological Science, 18: 657-662.
  4. Eveleth, R. (2011) The Hidden Potential of Autistic Kids – what Intelligence tests might be overlooking when it comes to autism. Scientific American, November 30, 2011.

This article was featured in Issue 85 – Top Strategies for Supporting your Family

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