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The Stanford-Binet IQ Test, From Binet to the SB5
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The Stanford-Binet IQ test is one of the oldest intelligence tests still in use. It began in France as Alfred Binet and Théodore Simon’s test for schoolchildren, and Lewis Terman of Stanford University turned it into an American scale. Its fifth edition, the SB5, is published by PRO-ED, covers ages 2 to 85+ and is given one to one by a qualified examiner12.
Where did the Stanford-Binet come from?
It started with a practical problem in French schools. Alfred Binet wanted a way to find children who could not keep up. With the physician Théodore Simon he built a scale in 1905 to assess French children’s intellectual ability1. Each task sat at the age at which typical children could first manage it, so a child’s results could be read as running ahead of or behind their age3.
Lewis M. Terman, a professor at Stanford University, brought the scale to the United States as a revision and extension in 1916, which is where the double name comes from1. Terman revised it again with Maud Merrill in 1937 and 1960. Robert Thorndike, Elizabeth Hagen and Jerome Sattler published the next revision in 1986, and the SB5, developed by Gale H. Roid, followed in 2003 as the fourth revision1.
Terman also left a second, less intended legacy. His long-term study of gifted children enrolled those who scored above 140, and that entry rule later hardened into the popular “genius” line4. The story is told in what IQ is considered genius.
How did the old Stanford-Binet calculate IQ?
The early versions used a ratio. The psychologist William Stern proposed dividing a child’s mental age by their real age, and Terman multiplied the result by 100 for the Stanford-Binet3. A 6-year-old who performed like an average 9-year-old got 150.
The ratio works only while abilities keep growing with age, which holds in childhood and fails for adults3. A 40-year-old does not have a “mental age” in the same sense. Modern tests, the SB5 included, instead compare each person with others of the same age and place the result on a scale with a mean of 1002. Our IQ calculator works through both formulas.
Why do old and new Stanford-Binet scores differ?
Because the spread changed. Older Stanford-Binet forms used a standard deviation of 16, while the SB5 uses 1524. The same rank therefore carries a slightly bigger number on an old form: a 130 on the SB5 sits where an old Stanford-Binet would print about 132.
Mensa’s admission lines show this in practice. American Mensa lists 130 for the SB5 and 132 for older Stanford-Binet forms, the same top 2% on two different scales5.
What does the SB5 measure?
The SB5 measures 5 cognitive factors, each with one verbal and one nonverbal subtest2:
- fluid reasoning
- knowledge
- quantitative reasoning
- visual-spatial processing
- working memory
That pairing is the test’s signature. Every ability is sampled twice, once with words and once with little or no speech needed. The two halves give separate Verbal and Nonverbal IQs alongside the full-scale IQ12. The publisher points to the nonverbal half for people with limited English or hearing loss. It also says the test was built to reach both very high and very low levels of ability2.
For how batteries like this compare in general, see what is on an IQ test.
How is the SB5 given?
One to one, with an examiner and a set of item books and materials; the kit includes blocks, toys and other objects that help with young children2. Testing starts with two subtests, matrices and vocabulary. Their results set where the nonverbal and verbal sections begin, so the rest of the session is pitched near the person’s level2. The same two subtests can also stand alone as a short Brief IQ2.
The whole battery runs about 5 minutes per subtest, 10 subtests in all2. PRO-ED lists the SB5 as a level C test, sold to qualified professionals such as psychologists2.
How is the SB5 scored?
In two layers. Each subtest gets a scaled score with a mean of 10 and a standard deviation of 3. These combine into the factor indexes, the Verbal and Nonverbal IQs, the Brief IQ from 2 subtests, and the full-scale IQ. All of them use a mean of 100, a standard deviation of 15 and a range of 40 to 1602.
The norms come from 4,800 people aged 2 to 85+2, and the full-scale, verbal and nonverbal IQs have reliabilities from .95 to .986. Reliability runs from 0 to 1, so values that close to 1 mean the scores are highly consistent. A report should still show a range around each score; why that matters is covered in are IQ tests accurate.
Who uses the Stanford-Binet?
Psychologists, school psychologists among them, across an age range that runs from preschool well into old age. The publisher describes it as one of the major instruments for assessing intellectual giftedness and says it can document a person’s strengths and weaknesses under US special education law2. Mensa accepts an SB5 score of 130 for admission5.
For parents, our guide to IQ tests for kids explains when a school or a psychologist would choose a test like this, and how the route works.
How is it different from the WAIS and from our test?
The WAIS is Pearson’s adult test, from age 16 upward, and reports five index scores without the SB5’s paired verbal and nonverbal design. The SB5 covers early childhood to old age with one kit2. Both are individually given clinical tests, and both report IQs with a mean of 100 and a standard deviation of 15.
Our free test is something else again: 30 reasoning questions online in up to 25 minutes, without an examiner and with provisional norms. It estimates reasoning, not the broad profile a Stanford-Binet produces, and it is not accepted in place of one. You can still try it to get a sense of where your reasoning sits.
FAQ
Is the Stanford-Binet still used?
Can I take the Stanford-Binet online?
No, not legitimately. It is sold only to qualified professionals and is given one to one with physical materials2. A site offering a free “Stanford-Binet” is offering something else under a borrowed name.
What is a good Stanford-Binet score?
There is no good or bad score in the grading sense. On the SB5, 100 is the middle of your age group, and the standard deviation is 15, so about two people in three score between 85 and 115. What each band means is set out on the IQ scale.