The WISC-V IQ Test for Children

The WISC-V is the fifth edition of the Wechsler Intelligence Scale for Children, an individually administered intelligence test for children aged 6 to 16, published in 2014. A trained examiner gives it one to one in about 45 to 65 minutes. It produces a Full Scale IQ plus five index scores covering verbal comprehension, visual spatial ability, fluid reasoning, working memory and processing speed. This guide explains what each part measures, how the scores work and what they can and cannot tell you about a child.

What is the WISC-V?

The Wechsler Intelligence Scale for Children, Fifth Edition, usually shortened to WISC-V, is the current version of a children's intelligence test first published in 1949. It grew out of the work of David Wechsler, whose adult and child scales became the most frequently used individual IQ tests in the English-speaking world. Wechsler tests have long been described as the "gold standard" of IQ testing, and the fifth edition of the children's scale appeared in 2014.

The test is designed for children between 6 and 16. It is individually administered, which means a qualified examiner sits with one child and works through a series of tasks, recording and scoring the answers by a fixed, standardised procedure. It is not a written exam handed out to a class, and it is not something a child sits alone.

A standard administration takes roughly 45 to 65 minutes. The main outputs are:

• Full Scale IQ (FSIQ), a single figure representing a child's general intellectual ability.
• Five primary index scores, each describing a narrower area of thinking.
• Optional ancillary and complementary scores used for particular clinical or educational questions.

Altogether the WISC-V contains 21 subtests and can yield 15 composite scores, although no child is given all of them in a typical session. The headline number is still called an IQ, and IQ stands for intelligence quotient, even though modern tests no longer calculate it as a literal quotient.

How has the WISC test changed over the years?

The original WISC of 1949 adapted several subtests from the earlier Wechsler-Bellevue Intelligence Scale of 1939 and added some new ones built specifically for children. Those first subtests were grouped into Verbal and Performance scales, giving a Verbal IQ, a Performance IQ and a Full Scale IQ.

Each later edition changed the structure a little more:

• WISC-R (1974) kept the same subtests but moved the age range from 5–15 to 6–16.
• WISC-III (1991) added a processing speed subtest and introduced four index scores, including a Verbal Comprehension Index and a Processing Speed Index.
• WISC-IV (2003) continued the shift towards index scores.
• WISC-V (2014) reorganised the primary indices around recent theory and research on intelligence, and brought in electronic administration.

Every edition has also been re-normed. Scores on intelligence tests tend to drift upwards across generations, a pattern known as the Flynn effect, so old norms can produce inflated results. Fresh norms keep the comparison group representative of children today. Revisions have also reworded questions to reduce bias against minorities and girls.

The WISC is one member of a family. Younger children, from two and a half to seven years and seven months, are tested with the preschool scale, while those of 16 and over can take the adult scale, described in our guide to the WAIS-IV. The age bands overlap at 6 to 7 and at 16, which lets an examiner pick whichever test gives a better floor or ceiling for a particular child.

What does the WISC-V measure?

The WISC-V aims to describe both a child's overall ability and the shape of that ability across separate areas. A published test review notes that the fifth edition reorganised its indices in line with current thinking on the structure of intelligence, and later researchers describe it as closely aligned with the broad abilities in the Cattell-Horn-Carroll framework.

The five primary index scores are:

• Verbal Comprehension Index (VCI): verbal concept formation, or the ability to reason with words, which is also influenced by vocabulary and general knowledge.
• Visual Spatial Index (VSI): visual spatial processing, such as mentally building and rotating shapes.
• Fluid Reasoning Index (FRI): logical and quantitative reasoning with unfamiliar problems.
• Working Memory Index (WMI): holding and manipulating information in mind for a short time.
• Processing Speed Index (PSI): how quickly and accurately a child handles simple visual tasks.

Each index needs two subtests. The split between knowledge built up through learning and reasoning on new material reflects the distinction between fluid and crystallised intelligence, and the WISC-V gives those two areas extra weight in the overall score.

Looking at the five indices side by side is often more informative than the single IQ figure. A child might be strong in verbal reasoning but slower on timed visual tasks, and the profile can help a psychologist suggest practical support at school.

What happens in each WISC-V subtest?

Subtests are labelled primary (needed for the five indices), secondary (optional extras within the same areas) or complementary. Here is what a child actually does.

Verbal Comprehension

• Similarities (primary): explaining how two words are alike.
• Vocabulary (primary): defining words.
• Information (secondary): general knowledge questions.
• Comprehension (secondary): questions about social situations and everyday concepts.

Visual Spatial

• Block Design (primary): arranging red-and-white blocks to copy a model. It is timed, and some harder items give bonus points for speed.
• Visual Puzzles (primary): choosing the three pieces that would make a pictured puzzle.

Fluid Reasoning

• Matrix Reasoning (primary): picking the option that completes an array with one missing square, a classic form of pattern recognition.
• Figure Weights (primary): choosing what keeps a pictured scale balanced.
• Picture Concepts (secondary): selecting one picture from each row that belongs together.
• Arithmetic (secondary): timed spoken word problems.

Working Memory

• Digit Span (primary): repeating number sequences forwards, backwards and in ascending order.
• Picture Span (primary): recalling pictures seen, in order where possible.
• Letter-Number Sequencing (secondary): reordering mixed letters and numbers.

Processing Speed

• Coding (primary): copying a symbol code against the clock; children under 8 do a simpler shape version.
• Symbol Search (primary): marking whether target symbols appear in a row.
• Cancellation (secondary): scanning arrangements of pictures and marking targets within a time limit.

How is the Full Scale IQ worked out?

The Full Scale IQ is not an average of all five indices. It is built from seven of the ten primary subtests: both Verbal Comprehension subtests, one Visual Spatial subtest, both Fluid Reasoning subtests, one Working Memory subtest and one Processing Speed subtest. Because verbal and fluid reasoning each contribute two subtests, they carry more weight, reflecting the importance given to crystallised and fluid abilities in modern models of intelligence.

Raw scores are then converted using the norms gathered from 2,200 children aged 6 to 16 years 11 months. Like all contemporary IQ tests, the WISC-V reports a deviation IQ. That means the score shows where a child sits compared with others of the same age, not a ratio of mental to actual age.

• A score of 100 is the average for the child's age group.
• Each 15 points is one standard deviation, so 115 is one standard deviation above average and 85 is one below.
• About two-thirds of children score between 85 and 115.
• About 5 per cent score above 125.

The index scores use the same scale, so a Working Memory Index of 110 and a Full Scale IQ of 110 mean the same relative position. To see how a particular number fits into named bands, our page on IQ score ranges sets them out, though the exact labels differ from one test to another.

How should you read a WISC-V score report?

A good report will not present a Full Scale IQ as a single, exact truth. Every IQ test carries measurement error, so the examiner should give a confidence interval, a range within which the child's true score probably lies. Treat that range, rather than the central figure, as the real result.

Scores also move. IQ is fairly stable from about age 10 onwards, but some children score quite differently on retesting or on a different test at the same age. About 42 per cent of children change by 5 or more points when re-tested. In Lewis Terman's longitudinal study of gifted children, begun in 1921, pupils retested at high school age had dropped 9 points on average, yet their parents felt they were as bright as ever.

Other points worth knowing:

• Category labels vary by test. Words such as "average" or "superior" are attached to score ranges chosen by each test's authors, and the boundaries are not uniform across tests. A psychologist should say which test was used.
• Some older terms are being replaced. "Borderline", which suggests closeness to intellectual disability (defined as IQ under 70), has alternatives that do not imply a diagnosis.
• Administration matters. If the examiner does not follow standard procedures, the usual result is scoring that is too lenient.

Above all, labels are statistical descriptions. They are useful for communication, but they do not define what a specific child can do.

What are the ancillary and complementary scores?

Beyond the five primary indices, the WISC-V offers extra composites that a psychologist can use for particular questions. You may see some of these abbreviations in a report.

Ancillary index scores published in 2014:

• Quantitative Reasoning Index (QRI)
• Auditory Working Memory Index (AWMI)
• Nonverbal Index (NVI)
• General Ability Index (GAI)
• Cognitive Proficiency Index (CPI)

The NVI, GAI and CPI can be calculated from the ten primary subtests. The QRI and AWMI each need one additional secondary subtest. Two expanded indices followed a year later, the Verbal (Expanded Crystallized) Index and the Expanded Fluid Index, so they are not in the original manuals.

Complementary index scores look at processes linked to school achievement and sensitive to specific learning difficulties:

• Naming Speed Index, measuring rapid automatised naming. It includes Naming Speed Literacy and Naming Speed Quantity, the latter a measure of rapidly naming small quantities that is particularly sensitive to maths achievement.
• Symbol Translation Index, measuring the ability to link visual symbols with words.

Using these options changes the length of the session. A shortened battery can save time, while a full extended assessment with every primary, ancillary and complementary index can take three hours or more.

What is the WISC-V used for, and where are its limits?

The WISC-V is used as an intelligence test and as a clinical tool. Psychologists use it in assessments for giftedness, intellectual disability and learning difficulties, and its scoring software can link intelligence scores statistically to achievement tests to help in identifying learning disabilities. During development, data were collected from many special groups, including gifted children, children with intellectual disability, specific learning disorders, ADHD, autism spectrum disorder and traumatic brain injury, and English language learners.

There are important limits, though. Some practitioners compare subtest scores against each other, a practice called pattern analysis, looking for clusters of low scores. David Wechsler himself suggested this in 1958. Research does not support it as a way of diagnosing ADHD or learning disabilities: most children with ADHD do not show a distinctive dip, and many children who do show such patterns do not have ADHD.

So a WISC-V result should be one strand of evidence, alongside school reports, teacher observations, developmental history and other assessments. IQ classifications are not the last word on how a child will do in life or in school. If you have concerns about a child's learning, attention or development, the right step is to speak to the school and to a qualified educational or clinical psychologist, who can decide whether a full assessment is appropriate.

How is the WISC-V different from an online IQ test?

The differences are substantial, and it helps to be clear about them. The WISC-V is given one to one by a trained examiner, normed on a large, carefully selected sample of children and checked against many other measures of ability, achievement and behaviour. Its validity has been studied through factor analysis and comparisons between clinical and non-clinical groups.

A free online test cannot reproduce that. There is no examiner watching how a child works, no spoken tasks such as Vocabulary or Digit Span, and usually no age-specific norms for children. Online tests are generally written for adults and focus on a narrow slice of ability, often visual reasoning puzzles similar to Matrix Reasoning.

That does not make online tests useless. They can be an interesting, low-stakes way for older teenagers and adults to try reasoning problems and get a rough sense of their strengths. Our guide to online IQ tests and their accuracy explains what they can reasonably tell you. But an online score should never be used in place of a professional assessment, and it should not be compared directly with a child's WISC-V result.

Preparation is also different. A child cannot meaningfully study for the WISC-V, and coaching on its specific tasks would undermine the result. The best help a parent can give is a rested, fed child who knows the session involves puzzles and questions, not a pass-or-fail exam.

Frequently asked questions

Sources

1. IQ classification (Wikipedia)
2. Wechsler Intelligence Scale for Children (Wikipedia)
3. Wechsler Intelligence Scale for Children-V: Test Review | Request PDF