Types of IQ Tests: Wechsler, Stanford-Binet, Raven's and More

Individual versus group tests

The first dividing line is how a test is administered. Individually administered tests are given one-to-one by a trained examiner, who can observe behavior, adjust pacing and follow standardized prompts. They are the gold standard for clinical and diagnostic use but are time-consuming and costly.

Group tests are designed to be given to many people at once — historically on paper, now often online. They trade the examiner's close observation for efficiency, making them suitable for screening, education and research where testing large numbers matters more than individual nuance.

The Wechsler scales (WAIS and WISC)

Developed by David Wechsler, the Wechsler scales are among the most widely used individual tests in the world. The WAIS is for adults and the WISC for children, with a preschool version (WPPSI) for the youngest test-takers. Rather than a single number, they yield index scores across domains such as verbal comprehension, perceptual or fluid reasoning, working memory and processing speed, which combine into a Full-Scale IQ.

Wechsler's key contribution was popularizing the 'deviation IQ' — scoring relative to an age group on a 100-mean, 15-SD scale — instead of the older mental-age quotient. The index-score profile is clinically useful because it can reveal strengths and weaknesses that a single overall number would hide.

The Stanford-Binet

The Stanford-Binet descends directly from Alfred Binet's original 1905 scale, adapted at Stanford University by Lewis Terman. It was the dominant American IQ test for much of the 20th century and remains in use today in revised editions. Modern versions assess several factors — including fluid reasoning, knowledge, quantitative reasoning, visual-spatial processing and working memory — across both verbal and nonverbal tasks.

Historically it was associated with the mental-age quotient that gave 'IQ' its name, but contemporary editions use the deviation-IQ scale like other modern tests. It is often chosen when assessing a very wide ability range, including young children and exceptionally high-scoring individuals.

Raven's matrices and culture-fair tests

Raven's Progressive Matrices is a nonverbal test in which the test-taker identifies the missing piece that completes a visual pattern. Because it requires no reading and minimal cultural knowledge, it is often treated as a relatively strong measure of fluid reasoning — the ability to solve novel problems — and is widely used across languages and settings.

Raymond Cattell's Culture Fair Intelligence Test was built with a similar goal: to reduce the influence of language and acquired knowledge by relying on abstract figures and patterns. The aim of these 'culture-fair' or 'culture-reduced' tests is to lower, though not entirely remove, the cultural and educational loading that more verbal tests carry.

Comparing the major tests

The table below summarizes how the leading tests differ in format, content and typical use. All of the listed tests are normed to a mean of 100 and a standard deviation of 15 in their current editions, so scores are broadly comparable across them even though the underlying tasks differ.