Wechsler Adult Intelligence Scale (WAIS)
is a general test of intelligence (IQ
), published in February 1955 as a revision of the Wechsler
test (1939), a battery of tests that is composed from subtests Wechsler "adopted" from the Army Tests (Yerkes
Wechsler defined intelligence as "The global capacity of a person to act purposefully, to think rationally, and to deal effectively with his/her environment. The fourth edition of the test was released in 2008 by Pearson.
The full scale IQ
test is broken down into 14 sub tests, comprising the verbal (seven sub tests) and performance scales (seven sub tests).
Wechsler's tests provide three scores:
- a verbal IQ (VIQ)
- a performance IQ (PIQ)
- a composite, single full-scale IQ score based on the combined scores.
WAIS-R was standardised in 1981 on a sample of 1,880 US subjects, ranging from 16 to 89 years of age, broken down into 9 different age groups. The current version is WAIS-III (1997). WAIS-IV is currently undergoing national standardization and has now been released.
The median full-scale IQ is centered at 100, with a standard deviation of 15. In a normal distribution this IQ range (1σ above and below the mean - that is, between 85 and 115) is where approximately 68% of adults would fall.
The WAIS-III measure is appropriate throughout adulthood and for use with those individuals ages 16-89 years of age (this is an expanded age range for adults 74-89, reflecting the increased average life expectancy). For persons under 16, the Wechsler Intelligence Scale for Children (WISC
, 6-16 yrs) and the Wechsler Preschool and Primary Scale of Intelligence (WPPSI
, 2 1/2-7yrs, 3mos) are used.
A short, four-subtest version of the battery has recently been released, allowing clinicians to form a validated estimate of verbal, performance and full scale IQ in a shorter amount of time. The Wechsler Abbreviated Scale of Intelligence (WASI) uses vocabulary, similarities, block design and matrix reasoning subtests similar to those of the WAIS to provide an estimate of full scale IQ in about 30 minutes.
Intelligence tests also are used in populations with psychiatric illness or brain injury, though some regard this use as controversial. Some neuropsychologists use the technique on people suffering brain damage as it leads to links with which part of the brain has been affected, or use specific subtests in order to get an idea of the extent of the brain damage. For example, digit span may be used to get a sense of attentional difficulties. Others employ the WAIS-R NI (Wechsler Adult Intelligence Scale-Revised as a Neuropsychological Instrument), another measure published by Harcourt. Each subtest score is tallied and calculated with respect to non-normal or brain-damaged norms. As the WAIS is developed for the average, non-injured individual, separate norms were developed for appropriate comparison among similar functioning individuals .
14 subtests of the WAIS-III
Information : Degree of general information acquired from culture (e.g. Who is the president of Russia?) Comprehension: Ability to deal with abstract social conventions, rules and expressions (e.g. What does "Kill 2 birds with 1 stone" metaphorically mean?) Arithmetic: Concentration while manipulating mental mathematical problems (e.g. How many 45c. stamps can you buy for a dollar?) Similarities: Abstract verbal reasoning (e.g. In what way are an apple and a pear alike?) Vocabulary: The degree to which one has learned, been able to comprehend and verbally express vocabulary (e.g. What is a guitar?) Digit span: attention/concentration (e.g. given the sequence of digits '123', reverse the sequence.) Letter-Number Sequencing: attention and working memory (e.g. Given Q1B3J2, place the numbers in numerical order and then the letters in alphabetical order)
Picture Completion: Ability to quickly perceive visual details Digit Symbol — Coding: Visual-motor coordination
, motor and mental speed Block Design: Spatial perception, visual abstract processing & problem solving Matrix Reasoning: Nonverbal abstract problem solving, inductive reasoning, spatial reasoning Picture Arrangement: Logical/sequential reasoning, social insight Symbol Search: Visual perception, speed Object Assembly: Visual analysis, synthesis, and construction
Optional post-tests include Digit Symbol - Incidental Learning and Digit Symbol - Free Recall.
WAIS-III subtests grouped according to indices
In addition to the Verbal and Performance IQ scores, the following four indices are derived.
Verbal IQ (VIQ)
Verbal comprehension index (VCI)
Working memory index (WMI)
Performance IQ (PIQ)
Perceptual organization index (POI)
Processing speed index (PSI)
- Digit Symbol-Coding
- Symbol Search
Note: Picture Arrangement, Comprehension, and Object Assembly do not contribute to the Index Scores