Wechsler Adult Intelligence Scale (WAIS)
Introduction
The WAIS-III is a test battery composed of a heterogenous group of 14 subtests organized into verbal & performance scales. (The WAIS-R had 11 subtests)
Procedure
Verbal subtests:
- retention of previously acquired information
- components
- information
- comprehension
- similarities
- arithmetic
- digit span
- vocabulary
- letter-number sequencing*
- emphasizes visuospatial capacity & visuomotor speed
- relative novel problems
- components
- digit symbol
- picture completion
- picture arrangement
- block design
- object assembly
- matrix reasoning*
- symbol search*
* Not included in WAIS-R; new to WAIS-III
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Description of components: (maximum raw score)
Information: (28)
- a series of orally presented questions that test the patient's knowledge of common events, objects, places & people
Comprehension: (33)
- a series of orally presented questions that require the patient to understand & articulate social rules & concepts or solutions to everyday problems
Similarities: (33)
- a series of orally presented pairs of words for which the patient explains the similarity of the common objects or the concepts they represent
Arithmetic: (22)
- a series of arithmetic problems that the patient solves mentally & responds to orally
Digit span: (30)
- a series of orally presented number sequences that the patient repeated verbatim for digits forward & in reverse for digits backward
Vocabulary: (66)
- a series of orally & visually presented words that the patient orally defines
Letter-number sequencing: (21)
- a series of orally presented sequences of letters & numbers that the patient simultaneously tracks & orally repeats, with the numbers in ascending order & the letters in alphabetical order
Digit symbol: (133)
- a series of numbers, each of which is paired with its own hieroglyphic-like symbol; using a key, the patient writes the symbol corresponding to its number
Picture completion: (25)
- a set of color pictures of common objects & settings, each of which is missing an important part that the patient must identify
Picture arrangement: (22)
- a set of pictures presented in a mixed up order that the patient rearranges into a logical story sequence
Block design: (68)
- a set of modeled or printed 2-dimensional geometric patterns that the patient replicates using 2-color cubes
Object assembly: (52)
- a set of common puzzles, each presented in a standardized configuration, that the patient assembles to form a meaningful whole
Matrix reasoning: (26)
- a series of incomplete gridded patterns that the patient completes by pointing to or saying the number of the correct response from 5 possible choices
Symbol search: (60)
- a series of paired groups, each pair consisting of a target group & a search group; the patient indicates, by marking the appropriate box, whether a target symbol appears in the search group
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Interpretation
From the raw scores (see above), scaled scores are determined by age-adjusted tables. Scaled scores range from 1-19 for each verbal & performance subtest. Thus the maximum summed scaled score for the verbal & performance subsets is (x 7 19) = 133. The maximum total scaled score is 266.
Full scale IQ scores (FSIQ) are determined from a table using total scaled score. The average score (50th percentile) is a total scaled score of 110-111 or an FSIQ of 100. The table maximizes at a total scaled score of 209 with an FSIQ of 155 (> 99.9 percentile).
The performance scale is less dependent on educational back- ground & more sensitive to normal aging.
General indicators of cognitive impairment in the elderly:
- a verbal - performance discrepancy of > 15 points
- increased inter-test scatter of subtest scores
The pattern of subtest scores is informative of the type of cognitive disturbance.
Disportionate impairment on the verbal scale is associated with left hemisphere damage with aphasia.