Stanford-Binet and Wechsler Tests

Why These Intelligence Tests Matter for Your Career as a Psychologist

You're preparing for the EPPP, which means you're on your way to becoming a licensed psychologist. Here's something that might surprise you: intelligence testing will likely be one of your most frequently used assessment tools, regardless of whether you end up in schools, hospitals, private practice, or forensic settings. The Stanford-Binet and Wechsler tests aren't just abstract academic concepts. They're the workhorses of psychological assessment. Understanding them deeply will help you make life-changing recommendations about educational placements, diagnose cognitive disorders, evaluate brain injuries, and support legal determinations about intellectual disability.

Let's make sense of these tests and the theories behind them in a way that sticks with you through exam day and into your practice.

Understanding Intelligence: The Theoretical Foundation

Before we dive into the tests themselves, we need to understand what different psychologists think intelligence actually is. Think of intelligence theories like different maps of the same city. Each one highlights different features and routes, but they're all describing the same place.

Spearman's Two-Factor Theory: The Foundation

Spearman identified two components of intelligence: g (general intelligence) and s (specific factors). According to this theory, every cognitive task you perform draws on both your overall mental horsepower (g) and specific skills needed for that particular task (s). If your brain were a smartphone, g would be the processor speed that affects everything you do, while s factors would be individual apps optimized for specific tasks.

Crystallized vs. Fluid Intelligence: The Dynamic Duo

Horn and Cattell made a crucial distinction that you'll see echoed throughout intelligence testing:

Crystallized intelligence (Gc) represents what you've learned through experience. Your vocabulary, factual knowledge, and acquired skills. It's like your personal database of information you've collected over the years.

Fluid intelligence (Gf) is your raw ability to solve new problems, see patterns, and think abstractly without relying on previous knowledge. It's your ability to think on your feet when you encounter something completely unfamiliar.

Different abilities peak at different ages. Speeded and novel problem-solving abilities tend to peak earlier than vocabulary and accumulated knowledge. There is no single peak age for all fluid or all crystallized tasks. The pattern depends on the ability and how it is measured (Hartshorne & Germine, 2015).

Carroll's Three-Stratum Theory: The Hierarchy

Carroll organized intelligence into three levels:

• Stratum III: General intelligence (g) at the top
• Stratum II: Eight broad abilities (including Gc, Gf, short-term memory)
• Stratum I: Numerous specific abilities

Picture this like a company org chart with a CEO at the top, department heads in the middle, and specialized workers at the bottom. All levels matter and work together.

CHC Theory: The Modern Framework

The Cattell-Horn-Carroll (CHC) theory combines John Horn's expansion of Raymond Cattell's Gf-Gc dichotomy with John Carroll's three-stratum hierarchical model. Kevin McGrew proposed integrating the two in 1997, and the term "CHC theory" was formalized around 1999-2001 during the development of the Woodcock-Johnson III. The theory currently includes about 16 broad cognitive abilities and over 80 narrow abilities, and it is the backbone of modern intelligence testing.

The Woodcock-Johnson (WJ-III, 2001 and WJ-IV, 2014) was the first major intelligence battery designed explicitly around CHC theory, and it remains the canonical operationalization of CHC in the psychometric literature. The Stanford-Binet 5th Edition (2003) also uses CHC but measures fewer broad abilities and was not designed as a comprehensive CHC battery. Wechsler tests don't officially claim CHC as their framework, but researchers have mapped Wechsler indexes onto CHC abilities.

Here's the practical Wechsler-to-CHC mapping you need to know:

Other Important Theories

PASS Theory focuses on four cognitive functions: Planning, Attention, Simultaneous processing, and Sequential processing. This theory connects to brain structures based on Luria's research.

Gardner's commonly described eight intelligences are linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalistic. These are proposed categories, not eight established independent brain systems. Recognizing the theory does not establish its biological claims or the effectiveness of matching lessons to an intelligence (Waterhouse, 2023).

Sternberg's Triarchic Theory describes three components: analytical intelligence (academic problem-solving), creative intelligence (handling novel situations), and practical intelligence (everyday tasks). Sternberg criticized traditional IQ tests for focusing too heavily on analytical intelligence while ignoring creative and practical abilities.

The Flynn Effect: Why Test Norms Matter

Predictive validity asks how well a test score forecasts a later outcome.

Here's something fascinating: IQ scores increased by about 3 points per decade throughout the 20th century. This "Flynn effect" means that if you took an IQ test with 1980s norms today, you'd score higher than if you took a test with current norms. It's like grade inflation in reverse, the test itself stays the same, but the comparison group gets smarter.

Changes in cognitive scores across generations need not be uniform across ages or ability levels. In a US adolescent study, increases and decreases differed by age and ability; lower-ability groups showed declines in some comparisons. Do not teach that reversals are limited to people above IQ 110 or use one sample to set a universal rule (Platt et al., 2019).

The changes happen too fast to be genetic. They're environmental. Better nutrition, more education, increased cognitive complexity in daily life, and other environmental factors likely drive these changes.

Stanford-Binet Intelligence Scale, 5th Edition (SB5)

Who and What

The SB5 assesses individuals from age 2 to 85+ and measures five cognitive factors derived from CHC theory, each split into verbal and nonverbal domains:

How It Works

Administration begins with two routing subtests: Object Series/Matrices (nonverbal) and Vocabulary (verbal). These routing tests are like a GPS finding your starting position. They determine where to begin testing based on the person's age or estimated ability.

A discontinue rule ends a subtest after its specified pattern of incorrect responses. Research discussing the SB5 describes this type of rule. Use the authorized manual for the exact subtest rule rather than importing a percentage or age-level rule from another test or edition (von Davier et al., 2019).

Scoring provides:

• Subtest scores (mean = 10, SD = 3)
• Full Scale IQ (mean = 100, SD = 15)
• Verbal IQ
• Nonverbal IQ
• Abbreviated Battery IQ (quick estimate from just the two routing subtests)

Woodcock-Johnson Tests of Cognitive Abilities (WJ-IV)

Who and What

If CHC theory had a "home" intelligence test, it would be the Woodcock-Johnson. Kevin McGrew, one of the WJ authors, helped invent CHC theory itself. So when the WJ-III came out in 2001, it was the first major IQ test built directly around CHC from the ground up. Most CHC research today still uses the WJ.

If CHC theory is the blueprint for how intelligence works, the WJ is the building someone actually constructed from it. The SB5 is a nearby building that borrowed parts of the same blueprint.

The current version (WJ-IV, 2014) tests people ages 2 to 90+ and measures seven broad CHC abilities:

How It Works

The WJ-IV gives you a General Intellectual Ability (GIA) score, kind of like an overall IQ. But it's not a simple average of every test. Tests that better predict general intelligence count more than tests that don't.

Think of GIA like a weighted GPA where AP classes count more than electives. Not because AP teachers are nicer, but because those grades say more about how you'll do in college.

Cross-Battery Assessment (XBA)

Sometimes one IQ test doesn't cover everything you want to measure. Cross-Battery Assessment is a method (created by Dawn Flanagan and Kevin McGrew) that lets you mix subtests from different IQ tests to fill in the gaps, all organized around CHC abilities. The WJ is usually the starting point because it covers more CHC abilities than any other single test.

XBA is like mixing tools from different toolboxes. Your WJ wrench fits most bolts, but sometimes you grab a Wechsler screwdriver to finish the job.

Why This Matters for the EPPP

If a question asks which intelligence test is most tied to CHC theory, or was built around CHC, or "operationalizes" CHC, the answer is Woodcock-Johnson. The SB5 also uses CHC but covers fewer abilities and came after the WJ-III.

Wechsler Adult Intelligence Scale, Fifth Edition (WAIS-5)

WAIS-5: Five Primary Indexes

The WAIS-5 is the fifth edition of the Wechsler Adult Intelligence Scale, published in 2024. It assesses cognitive ability from age 16 years, 0 months through 90 years, 11 months. Pearson uses the name WAIS-5, with the number 5.

WAIS-5 has five primary indexes: Verbal Comprehension (VCI), Visual Spatial (VSI), Fluid Reasoning (FRI), Working Memory (WMI), and Processing Speed (PSI). The older WAIS-IV had one Perceptual Reasoning Index (PRI); WAIS-5 separates visual spatial ability and fluid reasoning.

Think of an audio mixer with five channels. Each channel tells you about one part of the sound. A combined score gives a broader picture, but it does not erase the separate channels.

VCI samples word knowledge and verbal reasoning. VSI samples understanding shapes and spatial relationships. FRI samples solving new problems and finding rules. WMI samples holding and working with information. PSI samples speed and accuracy on simple visual tasks.

Sources: Pearson overview; Pearson comparison.

WAIS-5: Primary and Secondary Subtests

Each primary index uses two subtests:

Digit Sequencing and Running Digits are the two primary WMI subtests. Picture Span belongs to the WISC-V, not the WAIS-5. Do not mix the child and adult batteries.

WAIS-5 has 20 subtests: 10 primary and 10 secondary. Its five newly added tasks are Running Digits, Set Relations, Naming Speed Quantity, Symbol Span, and Spatial Addition. Picture Completion and Cancellation were removed. Figure Weights is now a primary FRI subtest. Arithmetic remains available as a secondary subtest.

Primary subtests are the tools in your everyday kit. Secondary subtests are extra tools you select when the referral calls for a closer look. Extra does not mean unimportant.

Sources: Pearson overview; Pearson comparison; Pearson scoring.

WAIS-5: FSIQ and Age-Based Scores

The standard FSIQ uses seven specified subtests: Similarities, Vocabulary, Block Design, Matrix Reasoning, Figure Weights, Digit Sequencing, and Coding. Administering all five primary indexes requires ten subtests. Pearson estimates about 45 minutes for the FSIQ and 60 minutes for the ten primary subtests; individual testing time varies.

FSIQ is derived from the sum of the required subtest scaled scores, using the edition's conversion tables or scoring software. Do not average the five index scores or choose whichever seven subtests look strongest.

Standard scores use age-based norms. An older adult is compared with same-age peers, not simply with young adults. Subtest scaled scores have a mean of 10 and SD of 3; composite scores have a mean of 100 and SD of 15. Raw scores and age-adjusted scores answer different questions.

A race time tells you how fast someone ran. An age-group rank tells you how they did against peers. Those are two different views of the same performance.

Sources: Pearson report; Pearson scoring; Pearson overview.

WAIS-5: Choosing an Ancillary Index

Ancillary indexes are extra score summaries selected for a clear assessment purpose.

The GAI uses Similarities, Vocabulary, Block Design, Matrix Reasoning, and Figure Weights. It samples verbal, visual spatial, and fluid reasoning without the primary working-memory or processing-speed subtests. It is not the sum or average of VCI, VSI, and FRI. Use the five required subtest scaled scores and the proper conversion.

The Nonverbal Index (NVI) reduces the need for spoken answers. It can help when expressive language is limited. Receptive language, culture, and the English-language norm sample still matter.

The Nonmotor Index (NMI) provides a broad estimate with reduced motor demands. The Motor-Reduced Processing Speed Index (MRPSI) focuses specifically on speed with less motor demand, using Symbol Search and Naming Speed Quantity.

The Cognitive Proficiency Index (CPI) uses Digit Sequencing, Running Digits, Coding, and Symbol Search to summarize working memory and processing speed.

The Visual Working Memory Index (VWMI) uses Symbol Span and Spatial Addition. These are secondary subtests; they do not form the primary WMI.

Choose the score like choosing the right microphone. A microphone built for a quiet voice solves a different problem from one built to reduce handling noise. Match the tool to the obstacle.

Sources: Pearson ancillary; Pearson faq.

WAIS-5: Interpreting Differences Carefully

A low index or an uneven profile raises questions; a score pattern alone does not establish ADHD, autism, dementia, or a learning disorder. Look at history, behavior during testing, language, sensory or motor needs, and other assessment findings.

Use confidence intervals, statistical significance, and base rates when judging differences. A confidence interval describes score uncertainty. Statistical significance asks whether a gap exceeds the comparison's error threshold. A base rate tells you how common that gap is in the reference group.

A statistically significant gap can still be fairly common. Pearson's sample report presents both significance and base rates because they answer different questions. Do not use a universal 23-point rule to discard FSIQ or automatically replace it with GAI.

A smoke alarm tells you to investigate. It does not tell you whether the cause is burnt toast or a fire. A score difference works the same way: it guides the next question.

Sources: Pearson report; Pearson faq.

WAIS-5: Keeping Editions Straight

WAIS-IV remains relevant when reading an older report or a question that explicitly names that edition. It used four indexes (VCI, PRI, WMI, PSI) and ten core subtests for FSIQ. WAIS-5 uses five primary indexes and seven specified subtests for FSIQ. Use the edition named in the question.

WAIS-5 is co-normed with WMS-5. WAIS-IV was co-normed with WMS-IV. Co-norming provides a shared basis for studying ability-memory comparisons; it does not make scores from different editions interchangeable.

Follow the current administration manual for start, reversal, discontinue, and substitution rules. These rules depend on the subtest. An old edition's rule is not a safe shortcut for the new edition.

Sources: Pearson comparison; Pearson faq.

WAIS-5: Administration Details

For WAIS-5 Vocabulary, a score below full credit on either of the first two administered items triggers reversal. Partial credit counts as below full credit. Give earlier items in reverse order until the examinee earns full credit on two consecutively numbered items, while also checking the discontinue rule.

Stop WAIS-5 Vocabulary after three consecutive zero scores. Zeros earned during reversal count toward this rule. If the stopping criterion is met while reversing, stop and exclude credit beyond the discontinue point.

These rules are specific to Vocabulary. Some subtests have no reversal rule. Follow the named subtest and starting-point instructions rather than applying one rule to the whole battery.

Source: Wechsler, Raiford, and Presnell (2024), WAIS-5 Administration and Scoring Manual, pp. 36–42 and 111.

Wechsler Intelligence Scale for Children, 5th Edition (WISC-V)

Structure

The WISC-V assesses children and adolescents ages 6-16 and provides:

• Full Scale IQ (FSIQ)
• Five Primary Index Scales: VCI, Fluid Reasoning Index (FRI), WMI, Visual Spatial Index (VSI), and PSI
• Optional Ancillary and Complementary Index Scales for deeper analysis

Each primary index consists of two subtests, but only seven primary subtests are needed to calculate FSIQ.

Clinical Patterns and Their Limits

A Wechsler profile describes performance in the tested domains. It does not by itself diagnose autism, ADHD, mild cognitive impairment, or dementia, and it cannot establish a specific everyday difficulty. A meta-analysis found average processing-speed weaknesses in autistic samples, but the profiles lacked sufficient diagnostic sensitivity and specificity. Use history, daily functioning, and other assessment findings to evaluate the cause of a low score (Wilson, 2024; Shaughnessy et al., 2019).

Wechsler Preschool and Primary Scale of Intelligence, 4th Edition (WPPSI-IV)

This test covers the youngest age range: 2 years, 6 months through 7 years, 7 months.

For ages 2:6-3:11: Three Primary Scales (Verbal Comprehension, Visual Spatial, Working Memory)

For ages 4:0-7:7: All five scales including Fluid Reasoning and Processing Speed

The younger age version has fewer scales because very young children can't reliably perform more complex cognitive tasks.

Common Misconceptions and Pitfalls

Misconception 1: "IQ tests measure innate, unchangeable intelligence."

Reality: IQ tests measure current cognitive performance, which is influenced by genetics, environment, education, health, and motivation. The Flynn effect alone proves IQ can change over time.

Misconception 2: "All clinical groups show the same pattern on intelligence tests."

Reality: Scores can suggest areas to investigate, but a profile alone cannot identify a disorder. Use the person's history and other evidence.

Misconception 3: "Processing Speed isn't that important. It's just how fast someone works."

Reality: Processing Speed reflects the efficiency of cognitive operations. When it's significantly low, it affects nearly everything else, learning, social interaction, and daily functioning. It's often the first thing to decline in neurological conditions.

Misconception 4: "The Full Scale IQ is always the most important score."

Reality: FSIQ gives a broad estimate. Index differences and the referral question may make other scores useful, but no universal gap automatically invalidates FSIQ.

Memory Aids for the Exam

For WAIS-5 Structure

Five channels, ten primary tasks, seven for FSIQ. Keep the counts tied to the score you need.

For Cognitive Aging

Words often hold up better than speed. Learned knowledge is often more stable than processing speed and new problem solving. This is a broad lifespan pattern, not a fixed WAIS-5 profile. Age-based scores already compare a person with peers of the same age.

Episodic memory (recalling events) and processing speed often decline with age, while vocabulary and well-practiced skills tend to be better preserved.

Source: NIA, How the Aging Brain Affects Thinking.

For Stanford-Binet Structure

Five fingers, two hands: Five factors, each with verbal and nonverbal domains

For Intelligence Theory Timeline

SCCH (like "sketch"):

• Spearman: Started it all with g
• Cattell: Crystallized vs. Fluid
• Carroll: Created three strata
• CHC: Combined Carroll and Horn-Cattell

Practical Application in Your Future Practice

A client completes the WAIS-5 and shows stronger verbal reasoning than processing speed. Check whether the gap is statistically significant, how common it is, and whether motor demands or other factors affected the speed tasks. Connect the findings with daily life before making recommendations.

The test is a map, and the interview is a view from the street. Use both before choosing a route.

Key Takeaways

• Healthy aging often affects processing speed and recall more than learned knowledge; it does not imply a fixed WAIS-5 score profile.

• WAIS-5 Verbal Comprehension uses Similarities and Vocabulary.

• WAIS-5 VSI uses Block Design and Visual Puzzles; FRI uses Matrix Reasoning and Figure Weights.

• Figure Weights is a primary Fluid Reasoning subtest on WAIS-5.

• WAIS-5 removed Picture Completion and Cancellation.

• Calculate WAIS-5 FSIQ from the seven required subtest scaled scores, not the average of index scores.

• WAIS-5 standard scores compare performance with same-age peers and do not prove lifelong stability.

• WAIS-5 NVI reduces spoken-answer demands but still requires attention to language and culture.

• WAIS-5 NMI addresses motor demands across broad ability; MRPSI focuses specifically on processing speed.

• WAIS-5 has five primary indexes: VCI, VSI, FRI, WMI, and PSI; VSI and FRI replace the older PRI.

• WAIS-5 primary working memory uses Digit Sequencing and Running Digits; Picture Span is not a WAIS-5 subtest.

• WAIS-5 uses seven specified subtests for FSIQ and ten for all five primary indexes, with scores based on age norms.

• WAIS-5 GAI uses five specified reasoning subtests; NVI reduces spoken-answer demands, while NMI reduces motor demands.

• Interpret WAIS-5 differences with confidence intervals, significance, base rates, and the person's history; a score gap alone does not establish a diagnosis.

• WAIS-5 is co-normed with WMS-5; edition-specific subtests and comparison norms must stay with their own edition.

• Intelligence theories differ in complexity: from Spearman's simple g + s to CHC's 16 broad abilities, but all contribute to how we understand cognition

• Crystallized intelligence (Gc) represents learned knowledge; Fluid intelligence (Gf) concerns novel problem solving. Their tasks can peak at different ages; avoid one fixed age range for every task (Hartshorne & Germine, 2015).

• CHC theory underlies modern intelligence testing. The Woodcock-Johnson (WJ-III/IV) is the canonical CHC battery and was designed around CHC from the ground up, measuring 7 broad abilities (Gf, Gc, Gv, Gwm, Ga, Glr, Gs). The Stanford-Binet 5th Edition also uses CHC but with fewer broad abilities. Wechsler indexes map onto CHC abilities post-hoc (VCI = Gc, FRI = Gf, VSI = Gv, WMI = Gsm, PSI = Gs)

• The Flynn effect caused IQ scores to rise ~3 points per decade in the 20th century, making it critical to use current norms for accurate assessment, especially in intellectual disability evaluations

• Stanford-Binet 5th Edition explicitly uses CHC theory, measures five factors split into verbal/nonverbal domains, uses routing tests to find starting points, and establishes basal and ceiling levels

• WISC-V covers ages 6-16 with five primary indexes; clinical patterns mirror adult patterns (ADHD shows PSI lowest)

• WPPSI-IV for young children (2:6-7:7) has fewer scales for younger children, expanding to five scales at age 4

Understanding these tests isn't about memorizing tables. It's about recognizing patterns that reveal how people think, learn, and function. This knowledge will guide your recommendations and interventions throughout your career.

Keep the WAIS edition and inference separate

WAIS-5 reports Verbal Comprehension, Visual Spatial, Fluid Reasoning, Working Memory, and Processing Speed indexes. WAIS-IV used a combined Perceptual Reasoning Index instead of the separate Visual Spatial and Fluid Reasoning indexes. WAIS-5 FSIQ uses seven core subtests; the prior edition used ten. The indexes concern verbal reasoning, visual-spatial problem solving, reasoning with novel information, holding and using information, and efficient work on speeded tasks. Use the named edition's structure and norms, not a relabeled older score. Research comparing age groups describes group patterns and cannot by itself show how one person changed over time. Similar age-standardized scores describe standing relative to age peers, not identical raw performance across ages. (Winter et al., 2025)

Profiles guide questions rather than diagnoses

A Wechsler profile describes performance in the tested domains. It does not by itself diagnose autism, ADHD, mild cognitive impairment, or dementia, and it cannot establish a specific everyday difficulty. A meta-analysis found average processing-speed weaknesses in autistic samples, but the profiles lacked sufficient diagnostic sensitivity and specificity. Use history, daily functioning, and other assessment findings to evaluate the cause of a low score (Wilson, 2024; Shaughnessy et al., 2019).

Discontinue rules belong to the specific test

A discontinue rule ends a subtest after its specified pattern of incorrect responses. Research discussing the SB5 describes this type of rule. Use the authorized manual for the exact subtest rule rather than importing a percentage or age-level rule from another test or edition (von Davier et al., 2019).

Flynn effects vary across samples

Changes in cognitive scores across generations need not be uniform across ages or ability levels. In a US adolescent study, increases and decreases differed by age and ability; lower-ability groups showed declines in some comparisons. Do not teach that reversals are limited to people above IQ 110 or use one sample to set a universal rule (Platt et al., 2019).

Gardner theory and its evidence limits

Gardner's commonly described eight intelligences are linguistic, logical-mathematical, spatial, musical, bodily-kinesthetic, interpersonal, intrapersonal, and naturalistic. These are proposed categories, not eight established independent brain systems. Recognizing the theory does not establish its biological claims or the effectiveness of matching lessons to an intelligence (Waterhouse, 2023).

WAIS-5 General Ability Index

The WAIS-5 General Ability Index uses Similarities, Vocabulary, Block Design, Matrix Reasoning, and Figure Weights. It samples verbal, visual spatial, and fluid reasoning without the primary working-memory and processing-speed subtests. Derive it from the required subtest scaled scores, not by averaging indexes. Report it alongside other findings; a higher GAI does not automatically invalidate FSIQ or establish a person's true capacity.

WAIS-5 subtest domains

In WAIS-5, Block Design and Visual Puzzles form the Visual Spatial Index. Digit Sequencing and Running Digits form the Working Memory Index. Matrix Reasoning and Figure Weights form the Fluid Reasoning Index. Similarities and Vocabulary form Verbal Comprehension, and Coding and Symbol Search form Processing Speed.

Source: Wechsler, Raiford, and Presnell (2024), WAIS-5 Administration and Scoring Manual, pp. 32–33.

Ceiling effects limit differentiation

A ceiling effect occurs when a test offers too little room to distinguish people near the upper end of performance. If several people reach the maximum, the recorded totals cannot show differences above that maximum. Check whether the item range fits the population rather than treating the maximum as proof of equal ability (Cappelleri et al., 2014).

Age and individual interpretation

Age-related group trends do not establish when one person's abilities began changing. Age-standardized scores compare performance with age peers, and interpretation needs the appropriate edition and reference data. Raw performance and an age-relative score answer different questions (Winter et al., 2025).

Primary Mental Abilities

The Thurstone Primary Mental Abilities approach assesses specific cognitive abilities across domains rather than reducing the assessment question to one general score. Research using this test alongside other cognitive measures has examined abilities such as reasoning, spatial orientation, and verbal and numeric skills (Schaie et al., 1991).

Flag-resolution sources

• Joshua K Hartshorne, Laura T Germine. When does cognitive functioning peak? The asynchronous rise and fall of different cognitive abilities across the life span. Psychological science. 2015 Apr;26(4):433-43. doi:10.1177/0956797614567339. PMID:25770099. https://pubmed.ncbi.nlm.nih.gov/25770099/