Oct 3, 2026·Special Population & Related Conditions
How Are Deaf Children Assessed for IQ? Language, Nonverbal Tests and Norms
An IQ test for deaf students is usually a nonverbal test given in the child's own language, such as ASL, where deaf children score close to hearing norms.
Dr. Russell T. WarneChief Scientist
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Deaf and hard of hearing children are usually assessed for IQ with nonverbal tests, or the nonverbal parts of standard batteries, given in the child's own mode of communication, whether that is American Sign Language (ASL) or spoken English. Assessed this way, deaf children's nonverbal IQ scores fall in the average range on hearing norms, so a low score on a verbal test usually says more about the child's access to spoken and written language than about reasoning ability.
This article covers who is being assessed and why language history matters, what the law requires about the language of testing, the problem with translating verbal tests into sign, what the research shows about nonverbal tests, and whether deaf children should be compared with deaf or hearing norms.
Deaf, deaf and hard of hearing: who is being assessed
A short note on language first. Writers about deafness often use "Deaf" with a capital D for people who communicate primarily in a sign language and identify with Deaf culture, and lowercase "deaf" for people who are audiologically deaf but do not identify with that community. A 2026 scoping review by Pratte and colleagues summarizes the convention this way. This page uses lowercase "deaf" for children generally, since a child's cultural and linguistic identity is not something an IQ test can determine.
About 2 to 3 of every 1,000 children in the United States are born with a detectable hearing loss in one or both ears, according to the National Institute on Deafness and Other Communication Disorders. The great majority are born to hearing parents. Using national survey data, Mitchell and Karchmer found that fewer than 5% of deaf and hard of hearing students in special education had at least one deaf parent, well below the 10% figure often repeated.
That fact shapes everything else about testing. A deaf child of deaf parents usually has full access to a signed language from birth. A deaf child of hearing parents may have had late, partial or inconsistent access to any language, and Hall's 2017 commentary in the Maternal and Child Health Journal links that kind of language deprivation to cognitive delays among other harms. Before any test is chosen, a careful evaluation therefore records the child's hearing history, the age of identification, the languages used at home and at school, and any hearing technology.
The language of testing: what the law requires
In United States public schools, 34 CFR 300.304 requires that assessments be given "in the child's native language or other mode of communication and in the form most likely to yield accurate information on what the child knows and can do." For a deaf child, 34 CFR 300.29 defines the mode of communication as "that normally used by the individual (such as sign language, Braille, or oral communication)." When the team plans services, 34 CFR 300.324 also requires it to consider a deaf or hard of hearing child's "language and communication needs."
The same principle governs testing children who speak a language other than English, and our article on how bilingual children are assessed covers it in detail. For deaf children it means two practical things. The evaluator either communicates directly in the child's language, which is the preferred arrangement, or works through a qualified interpreter. And any departure from the test's standard spoken instructions has to be described in the report, because the norms were built under spoken administration.
A 2014 review of intelligence measures for deaf and hard of hearing children by Reesman and colleagues, several of them from Gallaudet University, found that for some widely used tests "there is limited guidance and objective research available" on how deaf children perform, and that clinicians must recognize the difficulties of providing "an accessible and accurate administration of test items."
Why verbal IQ tests are hard to interpret for deaf children
Translating a verbal subtest into sign language changes the test. Maller translated five WISC-III subtests into sign and gave them to 110 severely and profoundly deaf children. Many items "differentially measured intelligence for deaf children," meaning an item's difficulty for deaf children did not match its difficulty in the norm group. In a related analysis comparing deaf children who use sign language with younger hearing children of similar ability, she concluded that verbal subtest scores "should not be used as an indication of delayed verbal ability," and that deaf and hearing children's subtest scores "should not be compared."
The gap between verbal and nonverbal scores is large. In a study of 128 deaf and hard of hearing children tested with the WISC-IV during routine assessments, Krouse and Braden found a mean Verbal Comprehension Index of 80.86 and a mean Perceptual Reasoning Index of 93.21. Reliability was high, so the scores were consistent, but the authors cautioned that for deaf children the Perceptual Reasoning Index may not carry the same meaning the older Performance IQ did.
Verbal tests still have a use. They show how much English vocabulary and knowledge a child has acquired, which matters for school planning. The usual practice is to treat them as measures of English language attainment and avoid letting them stand in for a deaf child's general intelligence.
Nonverbal tests and what the research shows
The most consistent finding in this field is that deaf children reason at about the same level as hearing children when language is taken out of the test. Braden's 1992 synthesis of 285 studies found that Wechsler performance scales were the most common instruments and that the way a test was administered was related to the IQs obtained. His earlier meta-analysis of 85 studies with 43,177 deaf participants concluded that deaf people's nonverbal abilities "were in the average range," that performance tests yielded slightly higher IQs than other nonverbal tests, and that both yielded higher IQs than verbal tests. People whose deafness was genetic had above-average IQs, and Braden concluded that environmental disadvantage holds back the development of verbal intelligence while leaving nonverbal abilities unaffected.
Tests designed to be given without words have held up well. The Universal Nonverbal Intelligence Test is administered by gesture, and Maller found no items that functioned differently for profoundly deaf and hearing children on four of its subtests. A later factor analysis by Maller and French supported the test's structure across deaf and hearing samples, though deaf examinees scored lower than expected on one reasoning subtest. Other batteries built for limited-language administration, such as the Wechsler Nonverbal Scale of Ability, are also common choices.
Nonverbal does not mean free of language, since the child still has to understand what each task asks. Reesman's review describes accommodations, score interpretation and subtest selection as test-specific decisions, which is why an examiner experienced with deaf children matters as much as the choice of test.
Deaf norms or hearing norms?
In the 1970s, Anderson and Sisco produced deaf norms for the WISC-R Performance Scale from 1,228 deaf children, and deaf children scored significantly below hearing children on the Coding and Picture Arrangement subtests. Braden later re-examined the case for separate deaf norms, and his 1992 synthesis found that the use of special norms did not affect IQ. Comparing a deaf child's nonverbal score with the general population answers the question most families and schools are asking: how this child reasons compared with all children of the same age.
Family language background also shows up in the scores. Deaf children of deaf parents have often been found to have higher performance IQs than deaf children of hearing parents, a pattern Braden examined in 1987. In a study of 142 deaf children at a residential school, Paquin and Braden found that performance IQ rose over about three years for all children, with the largest gains among children of deaf parents.
Frequently asked questions
What IQ test is best for deaf students?
No single test is best for every child. Nonverbal tests given by gesture or in the child's sign language, or the nonverbal parts of standard batteries, are the usual choices, and the evaluator picks among them based on the child's age and language history.
Do deaf children have lower IQs than hearing children?
On nonverbal tests, deaf children's scores fall in the average range on average. Their verbal scores tend to be lower, which mainly reflects reduced access to spoken and written language.
Can a sign language interpreter be used during an IQ test?
Yes, though direct communication by an examiner fluent in the child's language is preferred. Interpreted or signed administration departs from the test's standard procedure, so the report should say how the test was given.
Should a deaf child's verbal IQ be used to diagnose an intellectual disability?
Research on signed verbal tests advises against treating those scores as evidence of delayed ability. A diagnosis rests on nonverbal measures and adaptive functioning, read in light of the child's language history.
Who should test a deaf child's IQ?
A school or clinical psychologist experienced with deaf and hard of hearing children, ideally fluent in the child's language. Schools for the deaf and pediatric audiology programs can usually point families to one.
The takeaway
Assessing a deaf child's IQ comes down to matching the test to the child's language. Nonverbal tests given in the child's own mode of communication show that deaf children reason at about the same level as hearing children, while verbal tests mostly measure how much English the child has had access to. A careful evaluation says exactly how the test was given and reads verbal scores in light of the child's language history. For a sense of how reasoning is measured under standardized conditions, readers can try an online IQ test built by psychometricians, which reports scores against a defined norm group with their margin of error.
References
1. Pratte, M. M., Brodeur, M., Perron, M. E., & Hudon, C. (2026). Access to healthcare services for the Deaf: A scoping review of reviews. Health Expectations, 29(1), e70554. doi.org
2. National Institute on Deafness and Other Communication Disorders. (n.d.). Quick statistics about hearing, balance, & dizziness. nidcd.nih.gov
3. Mitchell, R. E., & Karchmer, M. A. (2004). Chasing the mythical ten percent: Parental hearing status of deaf and hard of hearing students in the United States. Sign Language Studies, 4(2), 138-163. doi.org
4. Hall, W. C. (2017). What you don't know can hurt you: The risk of language deprivation by impairing sign language development in deaf children. Maternal and Child Health Journal, 21(5), 961-965. doi.org
5. U.S. Department of Education. (2006). Evaluation procedures, 34 CFR 300.304. law.cornell.edu
6. U.S. Department of Education. (2006). Native language, 34 CFR 300.29. law.cornell.edu
7. U.S. Department of Education. (2006). Development, review, and revision of IEP, 34 CFR 300.324. law.cornell.edu
8. Reesman, J. H., Day, L. A., Szymanski, C. A., Hughes-Wheatland, R., Witkin, G. A., Kalback, S. R., & Brice, P. J. (2014). Review of intellectual assessment measures for children who are deaf or hard of hearing. Rehabilitation Psychology, 59(1), 99-106. doi.org
9. Maller, S. J. (1997). Deafness and WISC-III item difficulty: Invariance and fit. Journal of School Psychology, 35(3), 299-314. doi.org
10. Maller, S. J. (1996). WISC-III verbal item invariance across samples of deaf and hearing children of similar measured ability. Journal of Psychoeducational Assessment, 14(2), 152-165. doi.org
11. Krouse, H. E., & Braden, J. P. (2011). The reliability and validity of WISC-IV scores with deaf and hard-of-hearing children. Journal of Psychoeducational Assessment, 29(3), 238-248. doi.org
12. Braden, J. P. (1992). Intellectual assessment of deaf and hard-of-hearing people: A quantitative and qualitative research synthesis. School Psychology Review, 21(1), 82-94. doi.org
13. Braden, J. P. (1989). Deafness as a natural experiment: A meta-analytic review of IQ research [Report]. ERIC. eric.ed.gov
14. Maller, S. J. (2000). Item invariance in four subtests of the Universal Nonverbal Intelligence Test (UNIT) across groups of deaf and hearing children. Journal of Psychoeducational Assessment, 18(3), 240-254. doi.org
15. Maller, S. J., & French, B. F. (2004). Universal Nonverbal Intelligence Test factor invariance across deaf and standardization samples. Educational and Psychological Measurement, 64(4), 647-660. doi.org
16. Anderson, R. J., & Sisco, F. H. (1977). Standardization of the WISC-R Performance Scale for deaf children (Series T, No. 1). ERIC. eric.ed.gov
17. Braden, J. P. (1985). WISC-R deaf norms reconsidered. Journal of School Psychology, 23(4), 375-382. eric.ed.gov
18. Braden, J. P. (1987). An explanation of the superior performance IQs of deaf children of deaf parents. American Annals of the Deaf, 132(4), 263-266. eric.ed.gov
19. Paquin, M. M., & Braden, J. P. (1990). The effect of residential school placement on deaf children's performance IQ. School Psychology Review, 19(3), 350-355. doi.org
Hero image: Gallaudet University (Chapel Hall), by Bmzuckerman, licensed CC BY 4.0 (creativecommons.org/licenses/by/4.0). Via Wikimedia Commons.
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