WAIS-IV and WAIS-5 Index Scores Explained: What Each Number Means

A WAIS report does not hand back one number. It hands back a table: composite scores, percentile ranks and confidence intervals for a set of index scores, plus a Full Scale IQ (FSIQ). Two editions are in use in 2026, the WAIS-IV from 2008 and the WAIS-5 from 2024, and they slice the same abilities differently. This guide sets the two structures side by side, using Pearson's own published documents, and explains what each number can and cannot tell you.

WAIS-IV: four index scores and a Full Scale IQ

The fourth edition, published by Pearson in 2008, covers ages 16:0 to 90:11 and is sold only to qualified professionals (Pearson lists it at qualification level C). Its core battery is 10 subtests, and every one of them counts toward the FSIQ. They roll up into four index scores:

• Verbal Comprehension (VCI): Similarities, Vocabulary, Information
• Perceptual Reasoning (PRI): Block Design, Matrix Reasoning, Visual Puzzles
• Working Memory (WMI): Digit Span, Arithmetic
• Processing Speed (PSI): Symbol Search, Coding

Because all ten core subtests feed the total, four of the ten, 40%, come from working memory and processing speed. Our look at what the WAIS-IV items measure shows how differently those ten subtests relate to general ability: Arithmetic and Vocabulary load highest on g, Coding and Symbol Search lowest.

WAIS-5: five primary indexes, and only seven subtests in the total

The WAIS-5 was published in 2024 for the same age range, with new norms collected between February 2023 and January 2024 on 2,020 people aged 16 to 90 (Winter, Trudel and Kaufman, Journal of Intelligence, 2024). The biggest structural change is that the old Perceptual Reasoning index was split in two, and working memory and processing speed each lost a subtest from the total. The five primary indexes are:

• Verbal Comprehension (VCI): Similarities, Vocabulary
• Visual Spatial (VSI): Block Design, Visual Puzzles
• Fluid Reasoning (FRI): Matrix Reasoning, Figure Weights
• Working Memory (WMI): Digit Sequencing, Running Digits
• Processing Speed (PSI): Coding, Symbol Search

The FSIQ uses seven of those ten primary subtests: Similarities, Vocabulary, Block Design, Matrix Reasoning, Figure Weights, Digit Sequencing and Coding. Pearson lists about 45 minutes for the FSIQ and about 60 minutes for all ten primary subtests, against 60 to 90 minutes for the WAIS-IV core battery. Information, Comprehension and Arithmetic have not vanished. They are still in the battery as secondary subtests, and Pearson's sample report lists 20 subtests in all, 10 primary and 10 secondary.

The arithmetic of the change is worth a line. Working memory and processing speed made up 40% of the WAIS-IV total (four of ten subtests) and make up 28.6% of the WAIS-5 total (two of seven). The same split into visual-spatial and fluid reasoning happened on the children's scale in 2014, which our explainer on WISC-V index scores covers, and both follow the broad-ability model described in our piece on CHC theory.

How an index score is built

Each subtest is first converted from raw points to a scaled score (mean 10, standard deviation 3). The scaled scores in an index are added, and the sum is converted through the norm tables into a composite score on the familiar scale with a mean of 100 and a standard deviation (SD, the typical spread of scores) of 15, as our guide to the 15 versus 16 SD question explains. Each composite then gets a percentile rank and a 95% confidence interval.

Pearson's WAIS-5 sample score report shows the mechanics. The examinee's Verbal Comprehension scaled scores sum to 29, which converts to a VCI of 124 (95th percentile, interval 115 to 130). The seven FSIQ subtests sum to 82, which converts to an FSIQ of 111 (77th percentile, interval 106 to 116). The five index scores in that report average 107.4, not 111. The FSIQ is a conversion of its own seven-subtest sum, not the mean of the indexes, a point our article on full-scale IQ versus index scores makes in general.

Fifteen more scores: the ancillary indexes

The WAIS-5 goes further than the WAIS-IV by adding 15 ancillary index scores, so a full report can carry 21 composites: five primary indexes, the FSIQ and the 15 ancillary ones. Pearson groups them in three families.

• Expanded indexes (5): wider versions of each primary index, such as Expanded Fluid, which adds Arithmetic and Set Relations to Matrix Reasoning and Figure Weights
• Domain-specific indexes (6): Verbal Reasoning, Quantitative Reasoning, Visual Working Memory, Auditory Working Memory (Registration), Auditory Working Memory (Manipulation) and Motor-Reduced Processing Speed
• Summary indexes (4): Nonverbal, Nonmotor, General Ability and Cognitive Proficiency

The General Ability Index is built from five subtests (Similarities, Vocabulary, Block Design, Matrix Reasoning and Figure Weights), leaving out working memory and speed. The Cognitive Proficiency Index is the mirror image, built from Digit Sequencing, Running Digits, Coding and Symbol Search. Pearson's flyer says the expanded indexes help when two subtests inside one primary index disagree. In the sample report the General Ability Index is 115 against an FSIQ of 111, a gap of 4 points that the report marks as not statistically significant.

Reading the gaps between indexes

Index scores are meant to be compared, and the WAIS-5 report does the arithmetic. It compares each index with the mean of the five and every pair of indexes, printing a critical value (how big a gap must be to count as statistically significant at the .05 level) and a base rate (how common a gap that size is). In the sample report the critical values for the ten index pairs run from 10.60 to 14.39 points, so there is no single 15-point rule.

• Verbal Comprehension 124 vs Visual Spatial 103: gap 21, critical value 12.81, base rate 10% or less
• Verbal Comprehension 124 vs Working Memory 97: gap 27, critical value 12.47, base rate 5% or less
• Verbal Comprehension 124 vs Processing Speed 108: gap 16, critical value 14.10, significant, base rate 25% or less
• Working Memory 97 vs Processing Speed 108: gap 11, critical value 14.10, not significant

The 16-point gap is the useful one. It is statistically significant, yet Pearson prints base rates in bands (5%, 10%, 15%, 25% or more than 25%) and this gap lands in the second-widest band, so it is not rare. The report also notes that base rates are reported by ability level. Significant is not the same as unusual, and neither is a diagnosis. That reading belongs to the examiner who gave the test.

The descriptive labels changed too

The names attached to composite scores differ between editions. The bands usually printed for the WAIS-IV are 130 and above Very Superior, 120 to 129 Superior, 110 to 119 High Average, 90 to 109 Average, 80 to 89 Low Average, 70 to 79 Borderline and 69 and below Extremely Low. Pearson's WAIS-5 sample report prints different words: composites of 124 and 126 are labelled Very high, 111 and 115 Above average, and 97 to 109 Average. The full set of WAIS-5 band edges was not in the documents we could read, so check the manual before quoting a label. For the older bands, see our IQ classification table.

WAIS-5 scores run a little lower

New norms shift scores, and this edition shows it. In a counterbalanced comparison of 186 people aged 16 to 90, the average FSIQ was 101.6 on the WAIS-IV and 99.7 on the WAIS-5, a difference of 1.9 points. The authors put the implied Flynn effect (the long-run rise in raw test performance between norm samples) at about 1.2 IQ points per decade, well below the roughly 3 points per decade usually quoted for the twentieth century. They also caution that a separate comparison in 16-year-olds does not generalize beyond that age. Our piece on why old IQ norms inflate scores explains why a newer test tends to read lower.

What this means for online "WAIS" tests

The WAIS is an individually administered clinical instrument. It is given one-to-one by a trained examiner, takes 45 to 90 minutes and is restricted to qualified professionals, so an online quiz that calls itself a WAIS test is not the Pearson instrument and cannot report its norm-based scores. What a well-built online test can do is report a score against its own stated norms, with a percentile and a range; our guides to how IQ tests work and IQ test accuracy explain what to check. The percentile calculator converts any composite on the mean-100, SD-15 scale into a rank, and our piece on the ceiling on an IQ test explains why reported scores stop near 160.

In short: read the index scores as separate measurements, treat the FSIQ as its own calculation, and read any gap against a critical value and a base rate, never a rule of thumb. The IQ Metrics test reports its score with a percentile for the same reason.

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