Wechsler Adult Intelligence Scale (WAIS)

The Wechsler Adult Intelligence Scale (WAIS) is a tool that is widely recognized and extensively used to assess adult cognitive functioning. The WAIS comprehensively evaluates intellectual abilities, including verbal comprehension, perceptual reasoning, working memory, and processing speed. It is often used in neuropsychological assessments, educational evaluations, and diagnostic processes to better understand an individual’s cognitive strengths, challenges, and intellectual potential.

What Is the Wechsler Adult Intelligence Scale? 

The Wechsler Adult Intelligence Scale (WAIS) is a standardized test that measures adult intelligence across multiple cognitive domains ^[1]. Created by psychologist Dr. David Wechsler, the WAIS assesses verbal comprehension, reasoning, memory, and processing speed, offering a detailed picture of an individual’s intellectual functioning. It is now the most widely used intelligence test for adults in clinical and research settings.

How the WAIS was Developed 

The Wechsler Adult Intelligence Scale (WAIS) originated in 1939 with the Wechsler-Bellevue Intelligence Scale (WB). Unlike the dominant Stanford-Binet test, the WB introduced a dual-score format that measured verbal and performance abilities, setting a new standard in intelligence testing ^[2].

The first official WAIS was released in 1955, followed by major updates: WAIS-R (1981), WAIS-III (1997), and WAIS-IV (2008). These versions, published by Pearson, added more refined subtests and scoring systems. The WAIS-III introduced key scores for verbal comprehension, perceptual organization, working memory, and processing speed ^[2].

The WAIS-IV streamlined administration and aligned the test with modern neuroscience, maintaining a four-index model. The latest version, WAIS-V (2024), expanded this structure to include five indices: verbal comprehension, visual-spatial reasoning, fluid reasoning, working memory, and processing speed ^[3]. The WAIS-V remains the most widely used tool for comprehensively assessing adult intelligence.

Key Components of the WAIS

The Wechsler Adult Intelligence Scale Fifth Edition (WAIS-V) provides a robust assessment of adult cognitive functioning through a Full-Scale IQ (FSIQ) score and five primary index scores that represent core areas of intellectual ability ^[3]. These indices offer a more nuanced understanding of an individual’s strengths and challenges across different domains of thinking and reasoning. The five key indices measured by the WAIS-V are:

Verbal Comprehension

This index includes two primary tests: similarities and vocabulary. These subtests assess verbal skills, including the ability to reason with verbal information and to define words. The verbal comprehension index is a raw measure of verbal skills ^[4].

Visual Spatial Reasoning

Visual spatial reasoning refers to the ability to make sense of distance and direction, including perception of spatial features and mental rotation of images. The subtests under this index include block design and visual puzzles ^[5].

Fluid Reasoning

Fluid reasoning assesses logical capabilities and the ability to apply problem-solving skills to abstract situations. The subtests under the fluid reasoning index include matrix reasoning and figure weights [6].

Working Memory

Working memory is at the halfway point between short-term and long-term memory. The working memory subtests measure the ability to hold information in memory for long enough to do something with it, including digit sequencing and running digits ^[6].

Processing Speed

Finally, processing speed measures the ability to quickly recognize patterns and respond to them after taking in pieces of information. Processing speed subtests include coding and symbol search ^[6].

How Does the WAIS Work?

Wechsler’s intelligence test is a standardized assessment, meaning professionals administer the test following consistent procedures. An examiner must administer the test using these standard procedures, strictly adhering to the directions provided by the test’s producer. They can administer and score the WAIS with a paper form or use the Q-interactive software program for assistance ^[3].

Examiners using the Wechsler Intelligence Scale can order the scale directly from the publisher, Pearson. Pearson provides instructions for test administration, and the examiner must adhere precisely to the instructions. The examiner’s role is to administer test items and record the examinee’s exact response. To make scoring and interpretation easier, Pearson also offers testing software, which will provide a score report showing an examinee’s composite scores, their percentile rank, and a qualitative description of the score (ie, above average, average, below average) ^[7].

Interpreting WAIS Results

WAIS results are typically scored using specialized computer software. Each subtest generates a scaled score, which reflects an individual’s performance compared to a standardized mean. These scores are then converted to percentile ranks to show how an individual compares to the general population. For example, a score at the 95th percentile means the person performed better than 95% of test-takers ^[7].

In addition to individual subtest scores, the WAIS provides composite scores for each of its five indices: verbal comprehension, visual-spatial reasoning, fluid reasoning, working memory, and processing speed, as well as a Full-Scale IQ (FSIQ), which measures overall intellectual functioning. The mean composite score is 100, with a standard deviation of 15, meaning most people score within 15 points of the average ^[7].

The software also offers qualitative descriptors (e.g., average, above average, very high, low) to contextualize each score. These results help identify an individual’s cognitive strengths and weaknesses, screen for potential learning disabilities or intellectual giftedness, and guide clinical, educational, or workplace decisions.

Uses of the WAIS

WAIS has a variety of uses. For instance, this assessment may be used in neuropsychological testing to assess for brain impairment in cases of dementia or amnesia. Because the WAIS can detect deficits in processing speed, working memory, and learning, it helps identify brain impairment that occurs with these disorders ^[8].

Intelligence tests can also be used to evaluate overall cognitive functioning, to determine whether a person has a developmental delay or a disability ^[9]. If results indicate someone is of low intelligence, they may qualify for services or benefits related to a disability. Identifying disabilities can also be helpful when planning learning. For instance, an adult with a cognitive disability may qualify for accommodations if they seek a college degree.

Additionally, the results of an IQ test like the WAIS can be used for career-related purposes. For instance, results can reveal patterns of strengths and weaknesses that help an individual make a career decision. Employers may also use IQ testing to reveal patterns of strengths and weaknesses and predict whether a job candidate will be a high performer in a job they have interviewed ^[10].

How Reliable Is the WAIS?

Research consistently shows that the WAIS is a reliable assessment tool across age groups and cognitive profiles. It produces stable and consistent scores over time, making it suitable for individuals who are cognitively gifted, as well as those with intellectual disabilities, traumatic brain injuries, or Alzheimer’s disease ^[2].

However, while the WAIS is reliable, it does have limitations. The test does not measure every aspect of intelligence. Key skills such as goal-setting, planning, and persistence are not assessed. As such, the WAIS should not be used in isolation. To form a comprehensive understanding of an individual’s cognitive functioning, results should be interpreted alongside other behavioral, emotional, and functional assessments ^[7].

WAIS vs. Other Intelligence Tests

The WAIS is not the only tool used to assess general intelligence. The Stanford-Binet Intelligence Scales, another widely used IQ test, includes different subtests and scoring structures. For example, the Stanford-Binet uses tasks like the Block Span Test, where the examiner taps a sequence of blocks and the examinee must repeat the sequence, and the Last Word Test, which requires the examinee to repeat the final word of a spoken question—both of which are unique to the Stanford-Binet ^[11].

The index structure also differs. While the WAIS includes indices like verbal comprehension and processing speed, the Stanford-Binet measures fluid reasoning, knowledge, quantitative reasoning, visual-spatial processing, and working memory. Like the WAIS, the Stanford-Binet is considered a highly reliable intelligence test. It is frequently used to assess individuals at both ends of the cognitive spectrum, with gifted individuals often scoring high and those with intellectual disabilities scoring lower ^[12].

Final Takeaways

The WAIS is a cornerstone of psychological assessment, offering a detailed and standardized evaluation of cognitive abilities in adults. Its evolution from the Wechsler-Bellevue Intelligence Scale to the latest WAIS-V reflects the continuous advancements made in understanding human intelligence and cognitive neuroscience. The test allows for valuable insights into an individual’s strengths and weaknesses, making it a crucial tool in the diagnosis of mental health conditions like dementia, ADHD, and learning disabilities.

However, despite its reliability and versatility, the WAIS is not without limitations, focusing primarily on measurable cognitive abilities and not assessing the broader aspects of intelligence. Therefore, it should only be used with other assessments and clinical observations to provide a comprehensive understanding of an individual’s abilities.