Wechsler scales (WAIS/WISC)
The Wechsler scales are the most widely used clinical IQ assessments in the English-speaking world. The Wechsler Adult Intelligence Scale (WAIS-IV, now WAIS-IV) is used for adults aged 16–90; the Wechsler Intelligence Scale for Children (WISC-V) covers ages 6–16; the Wechsler Preschool and Primary Scale of Intelligence (WPPSI-IV) covers ages 2:6–7:7.
The WAIS-IV produces a Full Scale IQ from four index scores: Verbal Comprehension, Perceptual Reasoning, Working Memory, and Processing Speed. The WISC-V adds a Visual Spatial index and a Fluid Reasoning index. These multi-dimensional profiles are one of the key advantages of the Wechsler scales — they reveal not just a single number but a pattern of cognitive strengths and weaknesses.
Stanford-Binet
The Stanford-Binet is one of the oldest standardised intelligence tests, with origins in Alfred Binet's 1905 work in France. The current edition (Stanford-Binet 5, or SB5) covers ages 2–85+. It uses a mean of 100 and SD of 15, consistent with the Wechsler scales.
The SB5 is often preferred for assessing individuals at the extremes of the ability distribution — it has better ceiling and floor effects than the WAIS-IV, making it more informative for very gifted individuals (where the WAIS can be too easy) and for those with significant intellectual disability (where the WAIS can be too hard).
Raven's Progressive Matrices
Raven's Progressive Matrices (RPM) is not a full-scale IQ test but rather a measure of fluid intelligence and abstract reasoning. It uses nonverbal, culture-reduced visual pattern problems where the test-taker must identify the missing element in a matrix. There is no language requirement, making it suitable for cross-cultural comparisons and for individuals with verbal or hearing impairments.
RPM scores correlate very highly with full-scale IQ (r≈0.7–0.8) and are among the most widely used research measures of general fluid intelligence. However, as a single-domain test, RPM scores are not equivalent to full-scale IQ — they should not be interpreted as Full Scale IQ estimates.
Cattell Culture Fair Intelligence Test
The Cattell Culture Fair Intelligence Test (CFIT) uses a mean of 100 but a standard deviation of 24 rather than 15. This is an important difference: a score of 148 on the Cattell scale corresponds to approximately 130 on the Wechsler scale (both are top 2%). Mensa accepts Cattell scores of 148+, which is equivalent to Wechsler 130+.
Like Raven's, the Cattell CFIT uses nonverbal, culture-reduced items. It is frequently used as the basis for Mensa entry testing in several countries, including parts of the UK and Europe.
Other notable tests
The Woodcock-Johnson Tests of Cognitive Abilities (WJ-IV) is widely used in educational settings and provides a particularly rich profile of CHC (Cattell-Horn-Carroll) cognitive abilities. The Cognitive Assessment System-2 (CAS2) is based on Luria's neuropsychological theory and is particularly useful for assessing children with learning difficulties. The Kaufman Assessment Battery for Children (KABC-II) was designed with cultural fairness as a primary goal and is used with children from diverse backgrounds.
Which test is right for which purpose
For clinical diagnosis and educational placement: Wechsler scales or Stanford-Binet 5, administered by a licensed psychologist. For Mensa qualification: Cattell CFIT, Wechsler, or Stanford-Binet under proctored conditions. For cross-cultural research or when language barriers exist: Raven's Progressive Matrices or Cattell CFIT. For educational assessment of diverse learners: KABC-II or Woodcock-Johnson IV. For online estimation only (not clinical use): well-designed, honestly normed online tests interpreted with ±10 point uncertainty.