WISC-V Index Scores Explained: Ranges, Descriptors and GAI

The WISC-V reports a Full Scale IQ (FSIQ) and five primary index scores: Verbal Comprehension (VCI), Visual Spatial (VSI), Fluid Reasoning (FRI), Working Memory (WMI) and Processing Speed (PSI). All six are standard scores with a mean of 100 and a standard deviation (SD) of 15, for children aged 6:0 to 16:11. The FSIQ runs from 40 to 160, each primary index from 45 to 155, and Pearson treats 90 to 109 as average. The FSIQ is not the average of the five indexes: it is built from seven of the test's ten primary subtests. A full report adds ancillary and complementary indexes, including the General Ability Index (GAI) and the Cognitive Proficiency Index (CPI), covered below.

What are the five WISC-V index scores?

Each primary index is built from two subtests. Pearson's sample report also lists secondary subtests, shown here in brackets, that can substitute for or add context to the primary ones.

• Verbal Comprehension (VCI): Similarities and Vocabulary (secondary: Information, Comprehension), measuring verbal reasoning and acquired word knowledge
• Visual Spatial (VSI): Block Design and Visual Puzzles, measuring the ability to analyze and assemble visual detail
• Fluid Reasoning (FRI): Matrix Reasoning and Figure Weights (secondary: Picture Concepts, Arithmetic), measuring pattern-based and quantitative reasoning on new problems
• Working Memory (WMI): Digit Span and Picture Span (secondary: Letter-Number Sequencing), measuring how much information can be held and manipulated for a few seconds
• Processing Speed (PSI): Coding and Symbol Search (secondary: Cancellation), measuring how quickly simple visual decisions are made

Every index sits on the same mean-100, SD-15 scale as the FSIQ, which makes the numbers directly comparable. On the bell curve about 68% of children score between 85 and 115 and about 95% between 70 and 130; our IQ bell curve page and IQ percentile calculator turn any score into an exact percentile, and our explainer on IQ z-scores shows the arithmetic. For what the abilities mean outside the WISC, see our guides to processing speed, memory and verbal and non-verbal scores, and our Raven's matrices explainer for the kind of reasoning Matrix Reasoning samples.

WISC-V score ranges and descriptors: what counts as high, average or low?

Pearson's reports attach a descriptor to every composite. Its sample reports use Extremely High, Very High, High Average, Average, Low Average, Very Low and Extremely Low, and its published scoring guide states the average band outright: scores from 90 to 109 are typically considered average for the FSIQ and the primary indexes. The other cut points below fit every score printed on Pearson's sample reports, although we could not read the table in the manual itself, so treat the boundaries at 80 and 120 as inferred. The percentiles come from the normal curve.

• Extremely High: 130 and above, the 98th percentile and up (the top 2%)
• Very High: 120 to 129, about the 91st to 97th percentile
• High Average: 110 to 119, about the 75th to 90th percentile
• Average: 90 to 109, about the 25th to 73rd percentile
• Low Average: 80 to 89, about the 9th to 23rd percentile
• Very Low: 70 to 79, about the 2nd to 8th percentile
• Extremely Low: 69 and below, below about the 2nd percentile

Pearson's own technical report gives the same percentile ranks for round scores: a composite of 70 is the 2nd percentile, 80 the 9th, 100 the 50th, 110 the 75th, 120 the 91st, 130 the 98th and 140 the 99.6th. Other tests and older editions use different labels, as our guide to IQ classifications shows, so a descriptor only means something alongside the test that produced it.

How high and how low can WISC-V scores go?

On the standard norms the FSIQ ranges from 40 to 160 and the primary index scores from 45 to 155. Three ancillary indexes, the Nonverbal Index, the GAI and the CPI, also run from 40 to 160; the others, including the Quantitative Reasoning Index, the Auditory Working Memory Index and the complementary indexes, run from 45 to 155. Each subtest scaled score runs from 1 to 19 with a mean of 10 and an SD of 3, and 8 to 12 is typically considered average. In November 2019 Pearson published extended norms, developed after requests from the National Association for Gifted Children, that raise the ceiling to 28 for subtests and 210 for composites for children who reach a scaled score of 19. Pearson reports that only 16 of the 2,200 children in the normative sample obtained any composite score of 150 or higher, and that on the bell curve one child in 20,000,000 would be expected to reach an FSIQ of 180 or higher. Those tail figures are model output, not headcounts, a point our piece on the highest IQ score a test can report develops.

How is the WISC-V Full Scale IQ calculated?

The FSIQ is built from seven of the ten primary subtests: Similarities and Vocabulary from Verbal Comprehension, Block Design from Visual Spatial, Matrix Reasoning and Figure Weights from Fluid Reasoning, Digit Span from Working Memory and Coding from Processing Speed. The examiner adds the seven scaled scores and looks the sum up in a norm table, which returns the composite score, its percentile rank and a 95% confidence interval. It is a lookup of a sum, not an average of the indexes. Verbal Comprehension and Fluid Reasoning supply two subtests each and the other three indexes one apiece, so the FSIQ leans on verbal and fluid reasoning roughly twice as hard as on visual-spatial skill, working memory or processing speed; Pearson puts the fluid reasoning share of the FSIQ at 28%, against 20% on the WISC-IV. At most one substitution is allowed when deriving the FSIQ, and none for any other composite.

What are the WISC-V ancillary index scores, and how is the GAI calculated?

Beyond the five primary indexes, the WISC-V offers ancillary indexes that regroup the same subtests. Pearson's public documents give the index names and the number of subtests in each; we worked out which subtests go where by matching the sums on Pearson's own sample score report, and the result agrees with the composition that is widely published.

• General Ability Index (GAI), five subtests: Similarities, Vocabulary, Block Design, Matrix Reasoning and Figure Weights. Pearson describes it as an estimate of general intellectual ability that is less affected by working memory and processing speed than the FSIQ, and says it does not replace the FSIQ as the best estimate of overall ability
• Cognitive Proficiency Index (CPI), four subtests: Digit Span, Picture Span, Coding and Symbol Search, all drawn from working memory and processing speed. Pearson describes it as the efficiency with which information is processed in the service of learning and problem solving
• Nonverbal Index (NVI), six subtests that need no spoken answers: Block Design, Visual Puzzles, Matrix Reasoning, Figure Weights, Picture Span and Coding
• Quantitative Reasoning Index (QRI): Figure Weights and Arithmetic. Auditory Working Memory Index (AWMI): Digit Span and Letter-Number Sequencing
• Expanded indexes: the Verbal (Expanded Crystallized) Index and the Expanded Fluid Index, added in a 2015 technical report, and the Expanded General Ability Index, eight subtests with no working memory or processing speed, added in 2019

How is the GAI calculated? Add the scaled scores of the five GAI subtests and look the sum up in the GAI norm table in the manual or the scoring software; as with the FSIQ, there is no formula to apply by hand. The GAI is the usual choice when a child's working memory or processing speed is unusually weak relative to their reasoning, because those scores can pull the FSIQ down in a way that understates reasoning ability. In its 2019 technical report on the Expanded GAI, Pearson notes that giftedness experts advocated that either the FSIQ or the GAI be used for gifted admissions evaluations. Our guides to twice-exceptional children and to gifted cut-off scores cover how those numbers are used in practice.

What are the complementary index scores?

Three complementary indexes, the Naming Speed Index, the Symbol Translation Index and the Storage and Retrieval Index, come from five complementary subtests added in 2014 to help assess children with suspected learning disabilities in reading, maths and writing. Pearson states that these tasks are not designed as measures of intellectual ability, and they do not enter the FSIQ.

What changed from the WISC-IV?

The fifth edition, published in 2014, restructured the test rather than simply re-norming it. The WISC-IV combined visual-spatial and fluid-reasoning ability in one Perceptual Reasoning index. The WISC-V split it into Visual Spatial and Fluid Reasoning, and Pearson says Matrix Reasoning is the only subtest the new Fluid Reasoning index shares with the old one: Block Design moved to Visual Spatial and Picture Concepts became a secondary subtest. Three primary subtests are new: Visual Puzzles (Visual Spatial) and Figure Weights (Fluid Reasoning), which support the split, and Picture Span, a visual working-memory task that makes the Working Memory index less purely auditory than before. Digit Span itself now has forward, backward and ascending orders, and five complementary subtests were added.

When two indexes pull apart: what a big gap means

Our explainer on full-scale IQ versus index scores makes the general case. Pearson puts a number on it in its own FAQ: it is quite typical to have a gap of 1.5 standard deviations, 23 points or more, between two primary indexes, and 56.6% of the normative sample (1,246 of 2,200 children) had one. Among children in Pearson's special-group studies the figure was 52.5% (261 of 497). So a Verbal Comprehension score of 120 (the 91st percentile) beside a Processing Speed score of 90 (the 25th), 30 points and about 66 percentile points apart, is common rather than rare.

Whether a given gap is statistically reliable depends on the pair of indexes and the child's age. In Pearson's sample report for an 8-year-old, the .01 critical values for the ten pairs run from 14.5 points (Visual Spatial against Fluid Reasoning) to 19.0 (Verbal Comprehension against Processing Speed). A gap bigger than that is unlikely to be measurement error, but it can still be common, and it is a description of the child's profile, not a diagnosis; that judgment belongs to the examiner working from the full report. A different individually administered test, the DAS-II, builds its composite from reasoning subtests only; see DAS-II scores explained.

How reliable are WISC-V scores?

Pearson reports average internal-consistency reliabilities of .96 for the FSIQ, .92 for the Verbal Comprehension Index, .93 for the Fluid Reasoning Index, .95 for the Nonverbal Index and .96 for the GAI. Its efficacy page gives .88 to .93 for the primary indexes and a corrected test-retest figure of .92 for the FSIQ; the two kinds of figure should not be swapped. Every score comes with a 95% confidence interval that Pearson builds from the standard error of estimation, so the band is not centred on the obtained score: in Pearson's sample report a Fluid Reasoning score of 94 has an interval of 87 to 102, and a GAI of 124 has an interval of 117 to 129. Our piece on the IQ margin of error explains why one score should be read as a range.

Age range, norms and the WISC-6

The WISC-V covers ages 6:0 through 16:11 and was published in 2014. Pearson standardized it on 2,200 children in the United States, tested between April 2013 and March 2014, and scores compare a child with US children of the same age. Pearson has not re-normed the test: it has added extended norms and expanded indexes on the same sample. Its US product page now carries a "WISC-6 is coming" banner and its field-research page lists a sixth edition among upcoming studies, but no release date appears on any page we read; see what Pearson has said about the WISC-6.

The adult scale, the WAIS-5 of 2024, covers ages 16 to 90:11, so a 16-year-old sits in an overlap where the examiner chooses between the two tests; our guide to WAIS-IV and WAIS-5 index scores covers the adult side. For children aged 2:6 to 7:7 the equivalent Wechsler scale is the WPPSI-IV, covered in our guide to WPPSI-IV scores.

A different tool than a school screener

The WISC-V is an individually administered clinical instrument, given one child at a time. Pearson lists about 60 minutes for the core subtests, offers paper-and-pencil and digital administration, and requires purchasers to hold qualification level C. That is a different tool, for a different purpose, than the group-administered screeners in our piece on CogAT and NNAT scores, which are built to screen many students quickly rather than to give the depth of profile a WISC-V report contains.

Six numbers, one report: that is the WISC-V's core structure, and it is worth reading past the first one. Our IQ test reports its own result the same way, with the percentile attached rather than a bare score.

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