Wechsler Adult Intelligence Scale 3rd Edition (WAIS-III)

Purpose: Designed as a comprehensive test of cognitive ability for adults.

Population: Ages 16-89.

Score: Verbal IQ, Performance IQ, and Full Scale IQ.

Time:  (60 - 90) minutes.

Author: David Wechsler.

Publisher: The Psychological Corporation.

Description: The Wechsler Adult Intelligence Scale-Third Edition updates the WAIS-R, represents contemporary updated norms, and extends the age range. Some items have been modified, and there is greater discrimination for individuals in the mild to moderate mental retardation range as the floor has been extended. The artwork has been updated, but has been criticized as being distracting and overly detailed and discriminating against disadvantaged individuals, while the colors are thought to be potentially unfair to color blind individuals. There is less emphasis on timed performance, the new Matrix Reasoning subtest provides a better measure of fluid intelligence, the Letter-Number Sequencing subtest measures working memory, and the Symbol Search subtest (adapted from the WISC-III) measures processing speed. These changes strengthen the theoretical basis and statistical linkage to other measures of achievement and cognitive functioning.

Scoring: There are 14 subtests making up the Verbal and Performance Scales with 7 subtests each, however three of the subtests are supplemental or optional.  Letter-Number Sequencing is a supplementary subtest for the Verbal Scale but must be administered for computing the Working Memory Index Score.  Matrix Reasoning and Symbol Search are additions to the Performance Scale, and are also parts of the Perceptual Organization and the Processing Speed Indexes respectively.  Eleven subtests are used to compute the IQ scores. There are four index scores, Verbal Comprehension, Perceptual Organization, Working Memory and Processing Speed Indexes also comprised of eleven subtests. While scoring rules and reverse rules are implemented consistently, and improvements in the presentation, scoring criteria and queries and prompts, are noted, some items seem to be marked arbitrarily for query, and complex judgments are sometimes required for scoring.

Reliability: Extensive testing of reliability was an emphasis of the WAIS-III. The split-half reliability coefficients are outstanding for the Full Scale IQ, the Verbal IQ, and the VCI, and are excellent for the Performance IQ, POI, and WMI.  For most of the subtests the split-half reliabilities are excellent, however for the Object Assembly and the Picture Arrangement is below .75 for many of the age levels.  There is less than excellent test-retest stability for the Letter-Number Sequencing, Picture Arrangement, or Object Assembly, and the PO and PS factors do not appear as separate constructs for the oldest age group.  The WAIS-III helps to provide information about the interrelationships of a broad array of cognitive abilities as it is statistically linked to the WIAT and the WMS-III.

Validity:   Evidence of concurrent validity of the WAIS-III and WAIS-R, WISC-III, WIAT, SB: FE has been provided, and the criterion-validity of .88 for the SB: FE and a range of .53-.81 with WIAT composites.

Norms: The normative sample was stratified for many key variables and was consistent with the latest census data. Oversampling was done for research on educational level and cognitive abilities, and to perform item bias analyses for African-American and Hispanic individuals.  Another strength of the WAIS-III standardization sample was that the FSIQ was extended to 45 to 155 from 46 to 150.

Suggested use:  The WAIS-III can be used for assessment of learning disabilities. A sample of LD adults administered the WAIS-III and the WMS-III had low scores on the ACID profile, (Arithmetic, Coding [Digit Symbol-Coding], Information, and Digit Span).  Discrepancies among index score were found with LD adult population using the WAIS-III, and may be a stronger way to identify LD.  In LD groups, WMI<VCI, and PSI <POI.  Therefore combining the WMI and the PSI as in the SCALD profile (Symbol Search, Coding, Arithmetic, Letter-Number Sequencing, Digit Span) may be useful for investigating LD in adults.  The WAIS-III is used for understanding ADHD, for assessment of mental retardation, and interpretation of age related differences in ability, such as age trends in working memory and intelligence.