What the Fluid Reasoning Index combines and why it is disputed

0 The short answer

The Fluid Reasoning Index (FRI) is a composite standard score that the Wechsler scales introduced by splitting the old Perceptual Reasoning Index, and on both the WISC-V (2014) and the WAIS-5 (2024) Pearson builds it from only two subtests, Matrix Reasoning and Figure Weights. Independent factor analyses of the WISC-V and the WAIS-5 standardization data found that fluid reasoning and visual spatial ability did not separate cleanly, while a different analysis of the WISC-V found five factors with fluid reasoning almost identical to general ability, so the index is best read with its confidence interval and beside the Full Scale IQ. An adult can obtain a normed FRI from a psychologist who gives the WAIS-5, or online: ACIS reports an FRI from five subtests on its Full Scale form (50 dollars, about 175 minutes, prices read October 29, 2026), and the decisive limit is that an online, unsupervised, English only index is neither a clinical nor a diagnostic result.

1 What is the Fluid Reasoning Index?

The Fluid Reasoning Index is a summary score for a person's performance on a small set of reasoning subtests, and the word "index" tells you it is a composite built from several scaled scores, not the result of one test. An index is made by adding the scaled scores of its subtests and converting the sum to a standard score with a mean of 100 and a standard deviation of 15. The page on how IQ scores are normed explains the conversion, and the page on why the standard deviation is 15 explains the units.

The ability behind the label is fluid reasoning, abbreviated Gf in the Cattell-Horn-Carroll (CHC) model. Cattell's 1963 paper in the Journal of Educational Psychology carries the title "Theory of fluid and crystallized intelligence: A critical experiment," which is where the contrast between fluid and crystallized ability enters the testing literature. Riverside Insights, which publishes the Woodcock-Johnson V, defines Gf in its description of the cognitive battery, read October 29, 2026, as the broad ability to reason, form concepts and solve problems using unfamiliar information or novel procedures. The same document adds that it requires deliberate and flexible control of attention to solve on-the-spot problems. The page on what a fluid intelligence test measures covers the ability itself, its narrow abilities and its task families. This page stays on the index as a score.

Keeping the two apart matters because a name can promise more than a score delivers. Pearson's WAIS-5 overview brochure, read October 29, 2026, describes the fluid reasoning domain as covering "verbal, visual, inductive, quantitative, and logical" reasoning. The primary index that carries the domain's name, however, is built from two subtests. The domain is broader than the index, and the index is narrower than the ability. A person who reads "Fluid Reasoning Index 105" on a report is reading how two tasks went, expressed against the people of the same age who took them.

The label is also not the property of one design. The Cattell-Horn-Carroll model is a framework that several publishers follow, and each decides which subtests stand for each broad ability. The same three words can therefore sit on an index built from two subtests at one publisher and from five at another. Reading the subtest list behind an index is the first thing to do with any report, and the rest of this page assumes you will.

2 Where did the Fluid Reasoning Index come from?

The Fluid Reasoning Index is recent: it exists because the Wechsler batteries stopped treating visual spatial ability and fluid reasoning as one thing, first for children in 2014 and then for adults in 2024. Before that, the adult batteries reported a single Perceptual Reasoning Index. The page on the Perceptual Reasoning Index describes that earlier score, and the page on what changed between the WAIS-IV and the WAIS-5 follows the adult transition.

The idea was tried in research first. Weiss, Keith, Zhu and Chen compared four and five factor models of the WAIS-IV in the Journal of Psychoeducational Assessment in 2013, using the test's sample of 1,800 normative adults and 411 clinical adults. Their abstract reports that when all 15 subtests were considered both models were suitable, but the five factor model fit better. In their solution the Perceptual Reasoning Index differentiated into a visual composite of Block Design, Visual Puzzles and Picture Completion, and a fluid reasoning composite of Matrix Reasoning, Arithmetic and Figure Weights. That was a research finding about the published test, not a score the WAIS-IV printed.

The publisher made the change with the child battery. Canivez, Watkins and Dombrowski, writing in Psychological Assessment in 2017, state that one major revision goal of the WISC-V (Wechsler, 2014) was to divide the former Perceptual Reasoning factor into distinct Visual Spatial and Fluid Reasoning factors, and that Visual Puzzles and Figure Weights, adapted from the WAIS-IV, were added to measure visual spatial ability and fluid reasoning respectively. Pearson's WISC-V product page, read October 29, 2026, lists a 2014 publication date and ages 6:0 to 16:11, and says separate visual spatial and fluid reasoning composite scores result in greater interpretive clarity.

The adult scale followed ten years later. Pearson's WAIS-5 product page, read October 29, 2026, lists a 2024 publication date, describes the move from four to five factors, and presents separate visual spatial and fluid reasoning indexes as a purer measure of both constructs. The overview brochure, read the same day, gives the age range as 16 through 90:11 and says the normative samples were collected in 2023 and 2024 to match census data on five demographic variables. That is Pearson's own description, and the next sections test it against independent evidence.

3 Which subtests build the FRI on the WISC-V and the WAIS-5?

On both Wechsler scales the primary Fluid Reasoning Index adds exactly two scaled scores, Matrix Reasoning and Figure Weights, and every other fluid reasoning subtest sits outside it. Pearson's WISC-V page says Matrix Reasoning is the only subtest common to the old WISC-IV Perceptual Reasoning Index and the new FRI, that Figure Weights is new and contributes to the FRI, and that Block Design and Picture Concepts, which fed the old index, are not included. Canivez and colleagues confirm that each of the five WISC-V factor indexes uses two subtests. The WAIS-5 brochure prints the same pairing under its primary index scales.

Sources: Pearson WISC-V and WAIS-5 product pages and the WAIS-5 overview brochure, read October 29, 2026; Canivez, Watkins and Dombrowski (2017).

The brochure lists two more subtests under fluid reasoning in the full test framework, Arithmetic and Set Relations, and neither is one of the two primary subtests. Pearson's product page describes Set Relations as a new subtest designed to measure logical deductive reasoning, fluid intelligence and simultaneous processing. The brochure also names an Expanded Fluid Index among the ancillary scores. It is a separate score that Pearson reports in addition to the primary index, and this page does not describe how it is built because the brochure does not say.

Two consequences follow. The first is that a two subtest index is sensitive to each subtest. If one of the two tasks went badly because of a lapse or a misread instruction, half of the index moved with it. Pearson's brochure speaks to the same issue when it lists, among the benefits of its expanded index scores, insight into discrepancies between two subtests in a primary index. The second is that the index inherits the properties of its two tasks. Pearson's product page says Matrix Reasoning needs no strict time limit, while Figure Weights has one because higher ability examinees tend to respond faster, so speed of response can enter a score that is meant to describe reasoning. The FRI is a compact sample of matrix style induction and quantitative reasoning, and it is narrower than the sum of what the CHC model calls Gf. The ACIS pages on Matrix Reasoning and Figure Weights describe the same two task families in ACIS's own versions, and the page listing the WAIS-5 subtests follows each Wechsler subtest to the indexes it feeds.

4 How is the FRI different from the old Perceptual Reasoning Index?

The FRI is not a renamed Perceptual Reasoning Index: it keeps one of the old subtests, drops the construction and spatial tasks, and adds a quantitative reasoning task, so a score from one edition cannot be read as a score from the other. The WISC-V comparison is the cleanest because Pearson states it. Matrix Reasoning is the only subtest the WISC-IV Perceptual Reasoning Index and the WISC-V FRI share, Figure Weights is new, and Block Design, which contributed to the old index, is not part of the FRI and belongs with the Visual Spatial Index. For adults, Pearson describes the WAIS-5 separation as new relative to the WAIS-IV, and the page on the Perceptual Reasoning Index sets out what that older score combined.

What the split removed is the more important change. A combined index adds a task about reasoning on pictured rules to tasks about assembling or mentally manipulating shapes. A person who is stronger on one than the other receives the same sum as a person who is average on both, which is the case for separating them. That argument is a statement about how people differ, and it needs evidence that the two abilities do differ, which is what the next section examines. The page on the Visual Spatial Index covers the other half of the split.

The change also affects how old and new reports compare. A WAIS-IV report has no FRI. The only way to see one for that edition is the research composite that Weiss and colleagues derived, which put Arithmetic inside the fluid reasoning composite along with Matrix Reasoning and Figure Weights. On the WAIS-5, Pearson lists Arithmetic under fluid reasoning but outside the primary index. Anyone comparing a WAIS-IV result with a WAIS-5 result should compare the full scale scores and the subtests they share before comparing indexes that carry similar names and different contents. The ACIS comparison of the two editions takes that further.

5 Does the FRI measure something the Visual Spatial Index does not?

The evidence is split: the publisher says the two indexes are purer measures, independent factor analyses of the standardization data say they do not separate cleanly, and one rival analysis says five factors are needed while placing fluid reasoning almost on top of general ability. The dispute is about the structure of the data, and a reader should hold three studies in mind, with the limits of each.

Canivez, Watkins and Dombrowski tested the WISC-V in Psychological Assessment in 2017 using confirmatory factor analysis on the 2,200 child standardization sample. Their abstract reports that all higher order models with five group factors (Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory and Processing Speed) produced model specification errors in which the Fluid Reasoning factor had negative variance, and that a bifactor model with four group factors, in which Visual Spatial and Fluid Reasoning appear as one perceptual reasoning factor, fit best. They also point out that the publisher's final model carried a standardized path of 1.00 between general intelligence and the Fluid Reasoning factor, which suggests the two may be redundant. Their conclusion is that the attempt to divide the Perceptual Reasoning factor appears unsuccessful and that primary interpretive emphasis belongs on the Full Scale IQ.

The same group repeated the exercise on adults. Canivez, Watkins, McGill and Dombrowski analyzed the 20 WAIS-5 subtests of the 2,020 person standardization sample in Assessment, published online in 2026. Their abstract reports that exploratory analyses did not support five factors with separate Visual Spatial and Fluid Reasoning factors, that a four factor model with those two merged and a general factor dominating was supported instead, and that a bifactor model with four group factors fit best. The authors conclude that primary, if not exclusive, interpretation of the Full Scale IQ is supported. The abstract adds that the WAIS-5 technical manual did not include exploratory analyses or rival bifactor models, which is the gap they set out to fill.

The third study points the other way, with a twist. Reynolds and Keith, in Intelligence in 2017, tested whether the WISC-V measures the same constructs across ages 6 to 16 with first order, higher order and bifactor models. They found evidence of age invariance and concluded that both a general factor and five broad abilities, including Visual Spatial and Fluid Reasoning, are needed to explain the subtest covariances, with Fluid Reasoning and Visual Spatial correlated beyond general ability. The twist is that they also report Fluid Reasoning to be nearly equivalent to general ability, so even the study that keeps the factor says the factor is mostly g.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) frame what the publisher owes in this situation. Standard 1.14 says that when interpretation of subscores, score differences or profiles is suggested, the rationale and relevant evidence for it should be provided, and its comment adds that the distinctiveness and reliability of the separate scores should be demonstrated. The comment also says that evidence for the validity of separate scores would not necessarily justify interpreting the difference between them. The practical reading is modest. Both sides agree that the Fluid Reasoning Index is strongly tied to general ability. Where they differ is on how much it adds beyond the Full Scale IQ and beyond the Visual Spatial Index. The page on the Cattell IQ test shows how the older fluid and crystallized tradition handled the same question of what a fluid score adds.

6 How is a Fluid Reasoning Index score calculated and reported?

A Fluid Reasoning Index is the sum of its subtests' scaled scores converted to a standard score, and the report should print that score with a percentile and a 95 percent confidence interval. Each subtest is first reported as a scaled score with a mean of 10 and a standard deviation of 3 in the norm group. The two scaled scores are added, and a conversion table turns the sum into the index.

Pearson's WAIS-5 sample score report, dated September 16, 2024 and read October 29, 2026, shows the sequence for a sample examinee. Matrix Reasoning is printed as a scaled score of 12 (75th percentile) and Figure Weights as 10 (50th percentile), the sum of scaled scores is 22, and the FRI is printed as 105, at the 63rd percentile, with a 95 percent confidence interval of 98 to 111 and the descriptor Average. The Visual Spatial Index in the same report is 103 from a sum of 21. That is a publisher's sample for one examinee, not a norm and not a typical person, and it is useful only to show how the pieces of a report fit together.

Three details of that line matter. The index is not the average of the two scaled scores, and it is not the average of their percentiles, because scaled scores and percentiles are on different scales. The page on why you cannot average an IQ score and a percentile explains the error. The interval, 98 to 111, spans 13 points (our arithmetic), and it is the honest statement of what a two subtest sum can tell you: the single number 105 is the middle of a band, not a point. And the norm group matters, because every scaled score is relative to the reference group that Pearson describes in its brochure, so the same performance can convert to a different score on a different test with a different group.

The Standards ask for exactly this transparency. Standard 2.3 says that for each total score, subscore or combination of scores that is to be interpreted, estimates of relevant reliability and precision should be reported, and its comment says it is not sufficient to report reliabilities and standard errors only for total scores when subscores are also interpreted. Standard 2.13 asks that the standard error of measurement be provided in the units of each reported score, which is why an index printed without an interval tells you less than one printed with it. The page on reliability and validity explains the terms.

7 What does a given FRI score mean?

A Fluid Reasoning Index on the mean 100, standard deviation 15 scale describes where a person falls among same age peers on the tasks that built it, and the percentile follows from the normal curve. An index of 100 is the median of the reference group. An index of 115 is one standard deviation above it, and 85 is one below. Because the scale is a normal curve, those points translate into fixed percentiles.

Our arithmetic on the normal curve for a mean of 100 and a standard deviation of 15; the 105 row matches the percentile Pearson prints.

The page on the IQ percentile calculator converts any score. The question that people type, "what is the score range of the fluid reasoning index," has two answers. The scale is defined by its mean and standard deviation, and no index has a theoretical limit. The lowest and highest values a given test can print, however, are set by that test's norm tables and are listed in its manual. This page quotes no floor or ceiling for any publisher. A reader aiming at the top of the scale should read the page on tests built to measure above the usual ceiling before choosing an instrument.

Descriptors are a publisher's choice. Pearson's sample report labels 105 as Average and a Verbal Comprehension Index of 124 as Very high. Another publisher can use different words for the same numbers, so the number and its interval are the stable part of a report.

8 How should you read the FRI beside the other indexes?

An FRI should be read against the person's own other indexes and the Full Scale IQ, and a gap between two indexes must clear measurement error before it deserves a story. The Standards say so directly. Standard 2.4 states that when a score interpretation emphasizes differences between two observed scores of an individual, reliability and precision data, including standard errors, should be provided for those differences, and its comment says that when interpretation centers on the peaks and valleys of a profile, the reliability of score differences is critical.

Pearson's sample report shows what that looks like. In its index level comparisons, the Visual Spatial Index of 103 and the FRI of 105 differ by 2 points and the printed critical value for that pair is 10.99, so the difference is not significant at the .05 level, and the printed base rate is above 25 percent. The Verbal Comprehension Index of 124 and the FRI of 105 differ by 19 points against a critical value of 10.60, which is significant, with a base rate of 10 percent or less. The report prints the critical value for each pair separately, and the values run from 10.60 to 14.39 across the pairs listed. Those are the publisher's sample figures for one examinee, not rules for anyone else.

The logic behind a critical value is simple. If two indexes each carried a standard error of measurement of 3 points, the standard error of their difference would be about 4.2 points, the square root of 3 squared plus 3 squared, and a 95 percent interval around the difference would be about plus or minus 8 points. That is an illustration with invented standard errors, not any publisher's figure, and it shows why a 5 point gap between indexes is ordinary noise. The page on index score differences shows how often ordinary profiles contain large gaps once every pair is compared, and the page on the General Ability Index explains a composite that sets working memory and processing speed aside when those domains pull a profile in another direction.

Reading the FRI beside its neighbors also means asking what else a low or high result could reflect. The ACIS page on Logic Grid notes that its tasks lean on attention control and temporary information management, and the technical manual says fluid reasoning tasks can still be influenced by task format, visual clarity, quantitative notation and working memory demands. A fluid reasoning score that falls well below a person's other indexes is a reason to look at the neighboring scores, including processing speed and the Quantitative Reasoning Index, before drawing a conclusion. Group findings about how indexes relate never diagnose an individual.

9 How can an adult get a normed Fluid Reasoning Index?

An adult gets a normed Fluid Reasoning Index only from a battery that has a norm group and reports the index with an interval, which means a psychologist's battery or a published online battery, and a single puzzle or a free quiz does not supply one unless it states a norm group. The table compares the real options on what each reports for fluid reasoning, who it is normed against, whether it is supervised, how long it takes and what it costs, with prices and facts read on October 29, 2026.

Sources: Pearson WAIS-5 overview brochure; Riverside Insights Woodcock-Johnson V description; ACIS pricing and technical manual, all read October 29, 2026. Prices can change.

Three points make the table usable. The WAIS-5 row is the benchmark for this index because the FRI is Pearson's construction, but a clinician gives it for a clinical or legal question, and the page on where to take an IQ test lays out the in person and online routes. The Woodcock-Johnson V row shows that the same ability can be reported as a cluster built from other tests, which is the practical meaning of "a name can sit on different contents." And the single matrix test row is the one most readers meet first: the pages on a pattern recognition test and an abstract reasoning test explain how much one such format tells you about the whole ability, and why it is a task and not an index.

For readers choosing among online tests, the page on IQ tests for adults explains what to look for before paying. The question to ask of any product is the one this page began with: which subtests build the fluid reasoning score, what is it normed against, and does the report print an interval.

10 What does the ACIS Fluid Reasoning Index contain?

The ACIS Fluid Reasoning Index is built from five subtests, not two, and the technical manual defines it as induction, general sequential reasoning and quantitative reasoning within Gf. The five are Matrix Reasoning, Figure Weights, Visual Number Series, Logic Grid and Complex Relations, and the manual, read October 29, 2026, describes each one as follows.

The mixture is deliberate. Matrix Reasoning and the Visual Number Series subtest sample induction in visual and numeric material, Figure Weights samples quantitative reasoning, Logic Grid samples sequential deduction from explicit constraints, and the Complex Relations subtest samples relational reasoning in words. The ACIS pages describe each subtest's CHC placement, and the Figure Weights and Visual Number Series pages place those two between Gf and Gq. Because two of the five tasks require typed answers and one of them, Complex Relations, uses words, the index is not free of language, and the manual notes that fluid reasoning can still be influenced by task format, visual clarity, quantitative notation and working memory demands.

Which forms report the index differs, and the manual says so. Its form table marks the FRI as partial on Quick and Optimized and complete on the Full Scale form, where the full FRI requires all five subtests. The report script that builds the example reports, read the same day, forms the Quick FRI from Matrix Reasoning and Figure Weights and adds Logic Grid for Optimized. The Custom Test returns a domain's full index when the domain is completed, so choosing the five fluid subtests, at 5 dollars each, returns the complete FRI. The free trial lets a reader see the interface before paying, and the index itself comes from a paid form or the Custom Test.

The technical manual lists two composites that rearrange the same subtests. The Inductive Reasoning Index, IRI, combines Visual Number Series, Matrix Reasoning and Complex Relations and is described as useful when the question concerns rule inference and abstraction across novel stimuli. The Complete Fluid Reasoning Index, CFRI, adds Figure Weights, Logic Grid, Arithmetic and Mathematical Achievement to those, which the manual describes as expanding fluid reasoning with quantitative components. Both are reported on the Full Scale form. Their statistics sit in the manual, and this page quotes none of them.

An ACIS FRI is not a WAIS-5 FRI. The two share a name and two subtest names, but the items, the subtest lists and the reference groups differ, so the two numbers should never be subtracted or treated as interchangeable. The Wechsler version tells you how two tasks went. The ACIS version samples five formats, and a score built that way is less exposed to a bad hour on one task. It is still an online, unsupervised measurement.

11 What conditions should an unsupervised session meet?

A fluid reasoning score is only as good as the sitting that produced it, so the conditions matter more for an unsupervised session than for a supervised one. Fluid reasoning subtests are timed. For the five ACIS subtests the manual lists per item limits of 30 to 45 seconds for four of them and a 20 minute total for Logic Grid, which has no visible countdown. A device with a clear screen helps, because the manual names visual clarity as something that can influence performance on these tasks, and colors, shapes and sizes carry the information in Figure Weights.

The five fluid subtests are not among the three ACIS subtests that present items as audio (Digit Span, Alphanumeric Sequencing and Arithmetic), so working sound matters for a full battery but not for these five. The CFRI does include Arithmetic, which needs sound. A quiet room matters for every subtest. ACIS allows breaks, saves progress between subtests and gives 30 days to complete, so there is no reason to sit a reasoning task while tired or interrupted. Taking the five fluid subtests on separate occasions is allowed, and a person who notices a poor session can pause and return rather than finish a subtest in a bad state.

Do not rehearse the format. The index is meant to describe reasoning on material that is new to the person, as the Gf definition above says. A retake or a prior run through similar puzzles makes the tasks less novel, and the resulting score then describes familiarity as well as reasoning. This is a reading of the construct, not a measured effect size. Rest, a quiet room and a clear screen are the preparations that help without changing what the score describes.

12 Where ACIS sits, and what a buyer should do

ACIS sells a competing paid assessment, so treat this section as a disclosure: an ACIS Fluid Reasoning Index is an online, unsupervised, English only score that can describe your standing on five reasoning tasks and cannot diagnose, certify or replace a clinician's evaluation. ACIS is one option among those in the comparison above, and it is the only row in that table that returns a normed FRI at home for 25 or 50 dollars. It is not a WAIS-5, it does not produce WAIS-5 scores, and it is not for hiring decisions, school accommodations or admission to high IQ societies. The manual states that verbal and knowledge tasks are affected by English proficiency and educational exposure, and the Complex Relations task uses words. Anything that needs a clinical, educational or legal answer belongs with a qualified examiner.

The Standards for Educational and Psychological Testing (AERA, APA and NCME, 2014) are the benchmark this page applies to every index, including ACIS's. Standard 1.14 asks for the rationale and evidence behind any interpretation of subscores, differences or profiles, Standard 2.3 asks for reliability and precision estimates for each score that is interpreted, Standard 2.4 asks for such data for differences between scores, and Standard 2.13 asks for standard errors in the units of each reported score. Standard 5.1 asks that test users be given clear explanations of the characteristics, meaning and intended interpretation of scale scores, and of their limitations. The ACIS technical manual is where ACIS documents its own evidence, and a reader should check it against those standards, not against this page.

The American Psychological Association gives psychologists matching guidance in its Ethical Principles of Psychologists and Code of Conduct, effective January 1, 2017. Standard 9.02 asks psychologists to use assessments in ways that fit the research on their usefulness and proper application and to use instruments whose validity and reliability have been established for the population tested, and Standard 9.06 asks them to take account of test factors and personal, linguistic and cultural characteristics when interpreting results and to state significant limitations. Those standards bind psychologists, not a self administered online test, but they describe how any index should be read: with its purpose, its reference group and its limits in view.

What a buyer should do follows from that. If one index is the question, the Custom Test with the five fluid subtests costs 25 dollars and returns the full FRI; if the question is the whole profile, the Full Scale form costs 50 dollars and returns the six indexes together with the Full Scale IQ, so the FRI can be read beside the others. Look at an example report first, because it shows how the index, percentile and interval are printed. ACIS states a refund rule that should be read literally: "Full refund within 5 days if the report does not deliver the features described at checkout or a technical issue prevents you from accessing your results." Prices were read on October 29, 2026 and can change. For a reader who suspects the result will matter for a clinical or legal decision, the next step is a conversation with a psychologist, with the ACIS profile as a starting point and not as evidence.

13 Sources Behind This Page

Every figure above is traceable to one of the following, and each is linked at the point where it is used. Web pages were opened on October 29, 2026, and our own arithmetic is labeled as such in the text.

• AERA, APA and NCME. Standards for Educational and Psychological Testing. American Educational Research Association, 2014, Standards 1.14, 2.3, 2.4, 2.13 and 5.1.
• American Psychological Association. Ethical Principles of Psychologists and Code of Conduct, effective January 1, 2017, Standards 9.02 and 9.06.
• Pearson. Wechsler Adult Intelligence Scale, Fifth Edition (WAIS-5) product page, read October 29, 2026.
• Pearson. WAIS-5 overview brochure, 2025, read October 29, 2026.
• Pearson. WAIS-5 sample score report, sample examinee, dated September 16, 2024, read October 29, 2026.
• Pearson. Wechsler Intelligence Scale for Children, Fifth Edition (WISC-V) product page, read October 29, 2026.
• Canivez G L, Watkins M W and Dombrowski S C. Structural validity of the Wechsler Intelligence Scale for Children, Fifth Edition: Confirmatory factor analyses with the 16 primary and secondary subtests. Psychological Assessment, 2017, volume 29, issue 4, pages 458 to 472.
• Canivez G L, Watkins M W, McGill R J and Dombrowski S C. Construct validity of the WAIS-5: Complementary exploratory and confirmatory factor analyses of the 20 primary and secondary subtests. Assessment, 2026, published online, volume and issue not yet assigned in the Crossref record read October 29, 2026.
• Reynolds M R and Keith T Z. Multi-group and hierarchical confirmatory factor analysis of the Wechsler Intelligence Scale for Children, Fifth Edition: What does it measure? Intelligence, 2017, volume 62, pages 31 to 47.
• Weiss L G, Keith T Z, Zhu J and Chen H. WAIS-IV and clinical validation of the four- and five-factor interpretative approaches. Journal of Psychoeducational Assessment, 2013, volume 31, issue 2, pages 94 to 113.
• Riverside Insights. Woodcock-Johnson V Tests of Cognitive Abilities: CHC abilities and test descriptions, read October 29, 2026.
• Cattell R B. Theory of fluid and crystallized intelligence: A critical experiment. Journal of Educational Psychology, 1963, volume 54, issue 1, pages 1 to 22.

14 Frequently Asked Questions