What Is the Leiter Test? The Nonverbal IQ Scale Explained

The Leiter test, formally the "Leiter International Performance Scale," is the leading completely nonverbal IQ test. In its current third edition, the Leiter-3, published by Stoelting in 2013, the entire test can be given and completed without a single spoken word: instructions are demonstrated rather than said, and the examinee answers by moving and matching physical materials. It is normed for ages 3 to 75 and older and yields a Nonverbal IQ on the standard scale with a mean of 100 and a standard deviation of 15.

Most intelligence tests lean on language twice: the examiner explains tasks out loud, and many subtests require spoken answers or word knowledge. The Leiter-3 removes language from both sides of the table. The examiner teaches each task by pantomime and demonstration, and the examinee responds by placing, matching, or indicating materials. That design means a deaf child, a minimally verbal autistic examinee, or an adult who speaks no English is measured on reasoning rather than on English proficiency.

The Leiter-3 streamlines the twenty subtests of the previous edition down to ten, split across two batteries.

• Cognitive battery: Sequential Order, Form Completion, Classification and Analogies, Figure Ground, and an optional Matching/Repeated Patterns subtest measure fluid reasoning and visualization. These produce the Nonverbal IQ score. The cognitive battery takes about 20 to 45 minutes.

• Attention/Memory battery: Forward Memory, Reverse Memory, Attention Sustained, Attention Divided, and a Nonverbal Stroop subtest take roughly 30 more minutes and yield nonverbal memory and processing speed scores useful in neuropsychological work.

Composites sit on the familiar IQ metric (mean 100, standard deviation 15), subtests on scaled scores with a mean of 10, and the norms come from a sample of more than 1,600 people matched to U.S. Census statistics. Growth scores are also provided, which let clinicians track progress over time in examinees whose standard scores change slowly.

• Deaf and hard-of-hearing examinees: The Leiter line was originally designed for deaf children and adolescents, and hearing status has no bearing on administration.

• Autistic and speech-impaired examinees: Stoelting describes the format as ideal for individuals with autism and speech or language disorders, since no verbal response is ever required.

• Non-English speakers: Recent immigrants and English learners can be assessed without translation. The publisher reports psychometric studies showing what it calls exceptional fairness across cultural and ethnic backgrounds.

• Motor and attention conditions: Clinical comparison data cover ADHD, traumatic brain injury, severe cognitive delay, and severe motor delay, among other groups.

Psychologist Russell G. Leiter began building an experimental nonverbal scale in 1929, aimed at examinees with hearing or speech impairments and those who spoke no English, and the original scale was published in 1940 with a revision following in the late 1940s. That makes the Leiter one of the oldest continuously revised performance scales in psychology, created decades before "culture-fair" testing became a mainstream concern. The revised Leiter-R reported a correlation of .85 with the WISC-III, evidence that a wordless test can still track general intelligence closely.

The Leiter-3 occupies the same territory as other nonverbal measures such as the NNAT and the group-administered Beta-III and Beta-4, but as a full individually administered battery with attention and memory add-ons. Against a verbal-loaded test like the WISC, the trade-off is honest and worth stating: a nonverbal IQ omits verbal and crystallized abilities, which are among the strongest predictors of academic outcomes. Nonverbal tests are best understood as fairness-driven alternatives for when language would contaminate measurement, rather than as better IQ tests across the board.

Yes. It is an individually administered, norm-referenced intelligence test. Its Nonverbal IQ uses the same scale as mainstream IQ tests, so results plug directly into gifted, disability, and clinical decisions.

Professionals with graduate training in tests and measurement (qualification level B). It is given one-on-one with physical materials and is not available as a self-test.

The cognitive battery takes about 20 to 45 minutes; the optional Attention/Memory battery adds roughly 30 minutes.

It is one of the most commonly recommended IQ tests for autistic examinees with limited speech, because neither instructions nor answers require language.

Verbal and crystallized knowledge. Those abilities predict school performance strongly, which is why examiners often pair a nonverbal test with other measures, and why culture-fair testing involves trade-offs rather than free wins.

1. Roid, G. H., & Koch, C. (2017). Leiter-3: Nonverbal cognitive and neuropsychological assessment. In R. S. McCallum (Ed.), Handbook of nonverbal assessment (2nd ed., pp. 127-150). Springer. doi.org/10.1007/978-3-319-50604-3_8

2. Mazurek, M. O., & Kanne, S. M. (2018). Leiter International Performance Scale, Third Edition. In Encyclopedia of Clinical Neuropsychology. Springer. doi.org/10.1007/978-3-319-57111-9_1562

3. Hooper, V. S., & Bell, S. M. (2006). Concurrent validity of the Universal Nonverbal Intelligence Test and the Leiter International Performance Scale-Revised. Psychology in the Schools, 43(2), 143-148. doi.org/10.1002/pits.20136

4. Roid, G. H., Miller, L. J., Pomplun, M., & Koch, C. (2013). Leiter International Performance Scale, Third Edition (Leiter-3). Stoelting. stoeltingco.com