about the Wechsler Adult Intelligence Scale
David Wechsler designed intelligence
tests made up of items that are appropriate for a wide range of ages.
There are three main types of Wechsler
Wechsler Pre-school and Primary
Scale of Intelligence (WPPSI) - 3-7 years
Wechsler Intelligence scale for
Children (WISC) - 7-16 years
Wechsler Adult Intelligence Scale
(WAIS) - 16 years and over
The first was the Wechsler-Bellevue
Intelligence Scale (Wechsler, 1939).
Replaced 1955 by the Wechsler Adult
Intelligence Scale (WAIS).
1981 revision is referred to as the
A subsequent revision was conducted in
the US in 1997 and the present scale is the 3rd edition,
known as the WAIS-III. The revised version has almost 80 per
cent of the original form. A number of improvements have been made
including an attempt to make it more culturally fair.
The WAIS(R) was standardised on a sample
of 1,800 U.S. subjects, ranging from 16 to 74 years of age. It was a
highly stratified sample, broken down into 9 different age groups.
Equal numbers of men and women were used, as were white and nonwhite
subjects, in line with census figures. It was further broken down into
four geographic U.S. regions and six occupational categories. There
was also an attempt to balance urban and rural subjects. The mean I.Q.
for each age group on this test is 100, with a standard deviation of
15. The WAIS scales have impressive reliability and validity.
There are different adaptations of the
scale by country. For example, in Australia we have the Australian
adaptation of the WAIS-R (1989).
11 separate subtests, which are broken
into the Verbal scale (6 subtests) and the Performance scale (5
A person taking the test receives a
full-scale IQ score, a verbal IQ score, a performance IQ score, as
well as scaled scores on each of the subtests.
1. Information: 29 questions - a measure
of general knowledge.
2. Digit Span: Subjects are given sets
of digits to repeat initially forwards then backwards. This is a test
of immediate auditory recall and freedom from distraction.
3. Vocabulary: Define 35 words. A
measure of expressive word knowledge. It correlates very highly with
Full Scale IQ
4. Arithmetic: 14 mental arithmetic
brief story type problems. tests distractibility as well as numerical
5. Comprehension: 16 questions which
focus on issues of social awareness.
6. Similarities: A measure of concept
formation. Subjects are asked to say how two seemingly dissimilar
items might in fact be similar.
7. Picture Completion: 20 small pictures
that all have one vital detail missing. A test of attention to fine
8. Picture Arrangement: 10 sets of small
pictures, where the subject is required to arrange them into a logical
9. Block Design: Involves putting sets
of blocks together to match patterns
10. Digit Symbol: Involves copying a
11. Object Assembly: Four small jig-saw
Interpretation of the WAIS (R)
1. Obtain the 3 IQ scores. What
standardized categories do they fall into?
2. Is there a Verbal-Performance
discrepancy? Is it significant?
3. Break WAIS scores down into the
(a) Verbal Comprehension
(b) Spatial Perceptual
(c) Freedom from Distraction
More detailed notes about the WAIS-R
“Intelligence is multifaceted as well as multidetermined…What it
always calls for is not a particular ability but an overall
or global capacity”
(1981, p. 8). So speaks David Wechsler writing in
1981. The WAIS-R is an individual test of intelligence, was a revision
of the original Wechsler-Bellvue Scale created in 1939 and updated in
1955. This revision has subsequently been updated in 1997 but I’ll
talk about this one as it’s the one referred to in tutes this week and
is very similar to the 1997 revision.
According to Wechsler, intelligence is influenced by personality traits
and other nonintellective components, such as anxiety, persistence and
goal awareness. These nonintellective factors are important,
according to Wechsler, but he remarks ”no amount of drive will develop a
dullard into a mathematician” (1981, p.8).
gives a global IQ and also two separate IQ’s for the two scales: verbal
and performance. There are 6 verbal subscales and 5 performance subscales.
Wechsler believes that this test is a good measure of “g”. The two
scales can be used separately to see if a person has particular
strengths or weaknesses. Wechsler suggests that if there is more than 15
IQ points difference between the two main scales then this might be
cause for further investigation. The design of the test, with the two
scales, means that the verbal & performance scales can be used alone.
The Performance section alone can be used with examinees who are unable
to properly comprehend or manage language, or the Verbal scale alone can
be used with examinees who are visually or motor impaired. There is
little emphasis on speed in this test with only some subscales having
time limits and some subscales having bonuses for speed.
So what are
some of the psychometric properties of the test? Well firstly a large
standardization sample was used of 1880 Americans. This sample was 50%
male and 50% female. The individuals who formed the standardization
sample were aged from 16 years 0 months to 74 years 11 months. The
standardization sample was highly representative of the US population in
terms of age, sex, race, geographic region, occupation, education and
urban-rural residence. The individuals in the standardization sample
were tested between Nay 1975 and May 1980 at 115 testing centres across
scores were based on a reference group of 500 subjects in the
standardization sample aged between 20 and 34. Although scaled scores
for each of the 11 subtests are obtained using a single table based on
the reference group, IQs are derived separately for each of the age
groups (there are nine e.g. 16-17, 18-19, 20-24, 25-34….70-74).
The test can be used for people aged 16 and up. It has found to be
appropriate for use with those over 74.
So the WAIS has a good standardization sample and it is also considered
to be reliable and valid.
The reliability coefficients: (internal consistency) are .93 for the
Performance IQ averaged across all age groups and .97 for the Verbal IQ,
with an r of .97 for the full scale. Reliability for the 11 substests is
not as strong.
Split half reliability: .95+ (very strong)
Evidence supports the validity of test as a measure of global
intelligence. It does seem to measure what it intends to measure. It
is correlated highly with other IQ tests (e.g. The Stanford-Binet), it
correlates highly with empirical judgements of intelligence; it is
significantly correlated with a number of criteria of academic and
life success, including college grades, measures of work performance
and occupational level. There are also significant correlations with
measures of institutional progress among the mentally retarded.
One concern we discussed in some of my tutorials was with reference to
the comprehension subscale on the Verbal Scale. Was a question such as
“What is the thing to do if you find an envelope in the street that is
sealed and addressed and has a new stamp?” a valid measure of
intelligence. The only fully correct response to that question (i.e.
score of 2 is if you mail it or return it the post-office or a
postman. You get one point if you recognise it belongs to someone else
and try to give it to say a policeman and you get 0 points if you
suggest opening it, which frankly is not morally correct in our
society but may be a clever thing to do especially if you see some
cash in it! So it’s a culturally and morally loaded question. The
topic of culture-fair tests is a topic we’ll consider in the tutes