When we talk about an "IQ test," we are not referring to a single exam, but rather a family of tests that measure different abilities in various ways. Some assess both verbal and numerical skills in depth, while others focus purely on visual reasoning. In this article, we explain the three most well-known professional IQ tests, what they measure, how they work, and the key differences between them.
WAIS (Wechsler Adult Intelligence Scale)
WAIS is the most widely used intelligence test for adults in the world. Administered individually by a professional, it is a comprehensive battery that measures intelligence across four separate domains instead of reducing it to a single number:
- Verbal Comprehension: vocabulary and verbal reasoning
- Perceptual Reasoning: visual-spatial problem solving
- Working Memory: holding and processing information in mind
- Processing Speed: how quickly you complete simple tasks
These four domains combine to yield a full-scale IQ score. WAIS has very high reliability (around 0.96) and correlates significantly with real-life outcomes such as academic success and job performance.
Stanford-Binet
As one of the first modern intelligence tests in history, Stanford-Binet popularised the concept of "IQ." Unlike the WAIS, it covers a broad age range suitable for both children and adults. Its current version scores five factors across both verbal and non-verbal domains. It remains widely used in clinical evaluations and giftedness assessments. We explained how intelligence is measured in children in our article on intelligence testing in children.
Raven's Progressive Matrices
This test takes a very different approach: Raven's is completely non-verbal. It consists solely of visual patterns; you are shown an incomplete pattern and asked to find the logical piece that completes it. Therefore, it specifically measures fluid intelligence (the ability to solve new problems). Because it contains no verbal content, it comes closest to being "culture-fair," making it more equitable across different languages and cultures. We explored fluid intelligence in detail in our article on fluid and crystallized intelligence.
However, Raven's does not measure vocabulary, general knowledge, or verbal reasoning; it focuses on just one aspect of reasoning. As a result, it provides a measure of a specific skill rather than a full intelligence profile.
Which Test Is "Best"?
There is no single "best" test; the right choice depends on your purpose. For a comprehensive profile, WAIS or Stanford-Binet is preferred. For a quick, culture-fair measurement of fluid intelligence, Raven's is ideal. What they all have in common is that they are professional tests normed on large sample populations, with proven reliability, administered under expert supervision.
Are online IQ tests as reliable as these professional tools? We answered this important question in detail in our article on IQ test reliability. To see what test scores mean, check out our IQ levels chart, read our article on MENSA for high-IQ societies, or try our free IQ test right away.