The Wechsler Adult Intelligence Scale (WAIS) is the most commonly used adult IQ test for measuring intelligence. A previous version of the test was known as the Wechsler-Bellevue Intelligence Scale (WBIS), which was published in 1939. This test was composed of elements of other intelligence tests such as the Binet-Simon scale which was the precursor to the Stanford-Binet Intelligence Scale. This first true version of the WAIS Wechsler test was originally published in 1955 by its namesake David Wechsler. The first edition of the WAIS test included both verbal and non-verbal items within the test, with the non-verbal items known as “performance scales”. To an extent, this was new territory in intelligence testing, and by the 1960s the WAIS test had become the most popular intelligence test in use.
The decades since its inception have seen the Wechsler Adult Intelligence Scale revised multiple times:
- WAIS-R. This revised version of the original WAIS test was released in 1981 and consisted of six verbal and five non-verbal subtests. The verbal sections included: Information, Comprehension, Arithmetic, Digit Span, Similarities, and Vocabulary. The Performance subtests were: Picture Arrangement, Picture Completion, Block Design, Object Assembly, and Digit Symbol. The results of the subtests were grouped to provide a verbal IQ score, performance IQ score, and full-scale IQ score.
- WAIS-III. The next edition of the Wechsler Adult Intelligence Scale was launched in 1997. has seen several revisions over the year the WAIS was updated most recently in 2008, and it is now available in a fourth edition. In addition to the verbal IQ score, performance IQ score, and full-scale IQ score, the WAIS-III provided scores for four secondary indices: Verbal comprehension, working memory, perceptual organization, and processing speed.
- WAIS-IV. The current version of the test and is comprised of the 10 core subtests and five supplemental subtests listed in the table below. In addition, a new index was added which was the General Ability Index, or GAI. This index consists of the scores from the Similarities, Vocabulary, Information, Block Design, Matrix Reasoning, and Visual Puzzles subtests.
| Task | Index | Core Subtest |
|---|---|---|
| Similarities | Verbal Comprehension | x |
| Vocabulary | Verbal Comprehension | x |
| Information | Verbal Comprehension | x |
| Comprehension | Verbal Comprehension | |
| Block Design | Perceptual Reasoning | x |
| Matrix Reasoning | Perceptual Reasoning | x |
| Visual Puzzles | Perceptual Reasoning | x |
| Picture Completion | Perceptual Reasoning | |
| Figure Weights | Perceptual Reasoning | |
| Digit Span | Working Memory | x |
| Arithmetic | Working Memory | x |
| Letter-Number Sequencing | Working Memory | |
| Symbol Search | Processing Speed | x |
| Coding | Processing Speed | x |
| Cancellation | Processing Speed |
What Does the WAIS-IV Test Measure?
The Wechsler Adult Intelligence Scale returns scores on four separate indexes of adult intelligence, each with its own subsets:
1. The Perceptual Reasoning Index (PRI)
The PRI contains several subsets. Block design tests an adult’s visual-motor construction, visual-spatial processing, and visual problem-solving. Matrix reasoning measures inductive reasoning and one’s ability to solve problems in nonverbal, abstract ways. Visual puzzles reveal the subject’s visual-spatial reasoning. Through picture completion, psychologists measure how quickly the subject can perceive visual details. And quantitative reasoning is tested using figure weights.
2. The Verbal Comprehension Index (VCI)
For the VCI, test takers must describe how various concepts and words are similar. They also define vocabulary words and answer general knowledge questions. These tests are used to evaluate semantic knowledge, verbal comprehension, abstract verbal reasoning, and verbal expression.
3. The Working Memory Index (WMI)
WMI essentially evaluates how well you can remember things. To measure WMI, participants will be asked to recall a list of numbers in the order that they were given (digit span) and a series of numbers and letters in order (letter-number sequencing). These tests evaluate attention, mental control, auditory processing, and working memory. The WMI also uses arithmetic to measure concentration, quantitative reasoning, and mental manipulation.
4. The Processing Speed Index (PSI)
PSI is essentially a measure of how fast your brain works. Through symbol search, cancellation, and coding, the test evaluates graphomotor speed, associative memory, and processing speed. Graphomoter skills combine perceptual, cognitive, and motor skills and enable a person to write.
How Are Scores Calculated?
Scores are calculated on each of the four indices of the Wechsler Adult Intelligence Scale. They are then combined to create a Full-Scale IQ (FSIQ). Test takers will also be given a score on the General Ability Index (GAI), which uses the six subsets of the PRI and VCI: similarities, vocabulary, information, block design, matrix reasoning, and visual puzzles.
What’s A Good Score on the WAIS-IV IQ Test?
The Wechsler Adult Intelligence Scale is normed so that 100 is the median score for the adult population. Scores of 90-109 are considered to be in the average range, and the average IQ of all high school graduates is 105. College graduates have an average IQ of 115, which means that people in the “high average” range of IQ, 110-119, have a good chance of succeeding in college. Scores of 120-129 are considered “superior,” and this is the average IQ range for most successful Ph.D. candidates. A full-scale IQ score of 130 or above on the WAIS-IV will qualify you for Mensa, the high IQ society for people in the top 2% of intelligence.
The “low average” IQ range is 80-89, and people in this range will likely struggle with academics. Those scoring in the 71-80 range tend to exhibit what is called “borderline intellectual functioning.” Moderate retardation occurs from about 50-70, and severe retardation at IQs below 50.
How Reliable are the Scores?
The Wechsler Adult Intelligence Scale is one of the most trusted intelligence testing apparatuses, and therefore, most commonly used IQ test in counseling practice. However, it is not perfect. The latest revision aimed to adjust the average score back to 100 to account for the fact that IQ tends to rise over time. (This is called “the Flynn effect.”) According to David W Loring and Russell M. Bauer in their paper “Testing the limits,” The WAIS-IV eliminated some subtests, modified others, and introduced new subtests. It decreased the emphasis on performance speed, and since psychomotor slowing is a component of various forms of brain injury, the WAIS-IV will probably yield fewer low-range scores than the earlier version. This will likely mean a decline in the number of students who qualify for disability services and special education and will make it difficult to make historical comparisons with people who tested on earlier scales.