1. The Wechsler Intelligence Scales

2. The Wechsler Adult Intelligence Scale (WAIS)
The first Wechsler intelligence scale, known as the Wechsler-Bellevue Intelligence Scale, was developed in 1939, two years after the 1937 version of the Stanford-Binet
Developed in reaction to problems with the 1937 Stanford-Binet
SB items had been selected for use with children, & weren’t really appropriate for adults
SB had lots of timed tests, which made it difficult for older adults
SB did not consider that intellectual performance can deteriorate as a person grew older
SB produced only 1 score

3. Point & Performance Scale Concepts
point scale concept
with earlier SB tests, there were a number of different kinds of tasks & items at different age levels; more verbal at older ages
in Wechsler scales, all items of a particular type are grouped together, and are presented in order of increasing difficulty
points are assigned to each item, allowing for a calculation of a score for each type of task, or for each content area

4. Performance Scale Concept
earlier forms of SB largely dependent on verbal ability, especially in the test for the older age ranges
Wechsler scales include measures of PERFORMANCE (reflecting non-verbal abilities), as well as scales reflecting VERBAL abilities
comparison of verbal & performance scores provides a great deal of information, for example, in identifying children with learning disabilities
performance scale is less affected by language and cultural factors

5. The Wechsler Adult Intelligence Scale III (WAISIII)
Most recent version of the adult intelligence scale (there are also child & pre-school versions)
Published in 1997
developed for use with individuals aged 16 through 89
takes 60 to 90 minutes to administer
Wechsler believed in a single factor of intelligence, but thought that it consisted of specific, interrelated elements
to get a measure of overall intelligence, simply aggregate the capabilities on each of the separate elements

6. Subtests of WAISIII Verbal Subtest Major Function Measured Vocabulary
Vocabulary level
Similarities
Abstract thinking
Arithmetic
Concentration
Digit span
Immediate memory, anxiety
Information
Range of knowledge
Comprehension
Judgment
Letter-number sequencing*
Freedom from distractibility

7. Major Function Measured Picture completion Alertness to details
Performance Subtest
Major Function Measured
Picture completion
Alertness to details
Digit symbol-coding
Visual-motor functioning
Block design
Nonverbal reasoning
Matrix reasoning
Inductive reasoning
Picture arrangement
Planning ability
Symbol search*
Information-processing speed
Object assembly*
Analysis of part-whole relationships
Review verbal subtests first, starting with vocabulary
letter-number sequencing subtest is one of three newest subtests (also matrix reasoning and symbol search, which are performance subtests)
not required to obtain a verbal IQ score

8. Scoring
each subtest produces a raw score – i.e., a total number of points – and has a different maximum total – e.g., vocabulary has 33 items, scored 0, 1 or 2 for a maximum of 66 points
raw score for each subtest (total no. of points) is converted to a scaled score with a mean of 10 and a standard deviation of 3
there are separate norms for ages 16-17; 18-19; 20-24; 25-29; 30-34; 35-44; 45-54; 55-64; 65-69; 70-74; 75-79; 80-84; 85-89

9. Scaled score equivalents of raw scores: 20 to 24 year old norms

10. Verbal IQ Score
to obtain a verbal IQ score, 6 of the 7 verbal scaled scores are summed (letter-number sequencing is not included)
then a table formed from a standardization sample of individuals from all groups used to get verbal IQ
resultant IQ is a deviation IQ with a mean of 100 and s.d. of 15

11. Performance IQ Score
to obtain a performance IQ score, 5 of the 7 performance scaled scores are summed (symbol search & object assembly not included)
then a table formed from a standardization sample of individuals from all groups used to get performance IQ
resultant IQ is a deviation IQ with a mean of 100 and s.d. of 15

12. Full-Scale IQ Score
to obtain full-scale IQ, sum scaled scores of 11 verbal and performance non-optional subtests, and use table based on standardization sample

13. Index Scores
in addition to grouping tests into verbal and performance categories, can group them into four different skill areas:
verbal comprehension [crystallized intelligence]
perceptual organization [fluid intelligence]
working memory
processing speed [how quickly mind works]

14. Structure of the Scale FSIQ VIQ PIQ VCI WMI POI PSI Vocabulary
Similarities
Information
Comprehension
Digit Span
Arithmetic
Letter–Number Sequencing
Block Design
Matrix Reasoning
Picture Completion
Picture Arrangement
Digit Symbol— Coding
Symbol Search 8

15. Plotting Subtest Scores (IQ)15

16. Reliability Split-Half Test-Retest Full Scale .98 .95 Verbal IQ .97
.94
Performance IQ
.88
For full-scale IQ, standard error of measurement is quite small, around 2 to 2.5 IQ points
This means that an examinee’s true score will fall within 5 points either side of the obtained score 95% of the time

17. Reliability of Subtests
Reliabilities for the subtests vary a great deal, and are lower than reliabilities of the full-scale, verbal, performance IQ’s, and the four indexes
They range from low .70’s to low .80’s, with some in the .60’s

18. Validity of the WAIS
WAISIII correlates highly (mid 90’s) with earlier versions of the WAIS
Correlation with SBIV is .88
Correlates significantly with grades in high school, university
IQ and occupational attainment are also significantly correlated
Predictions deriving from theory are borne out; fluid intelligence supposedly declines more rapidly in old age than crystallized intelligence
Supported by finding that verbal subtests show minimal decrement with age, while performance subtests drop markedly

19. Conry & Plant (1965)

20. Interpreting the WAIS Verbal-Performance IQ Comparisons
Neurological impairment may be indicated when one of the scales falls in the low average or lower range, and the other in the average or higher range
Emotional trauma may be indicated if the client has a low verbal or performance IQ that does not seem to match their past level of functioning
Language-related learning difficulty may be indicated by an low verbal IQ and average or high performance IQ

21. Case Study: Stephen Gould

22. High Stakes? Atkins vs. the State of Virginia

23. The Wechsler Intelligence Scale for Children (WISC)
First published in 1949
Revised in 1974, 1991
Current version is WISC-IV, published in 2003

24. WISC-IV Measures intelligence from ages 6 through 16
Contains 15 subtests
Abandons VIQ-PIQ
Instead produces four major indices:
Verbal comprehension
Perceptual reasoning
Processing speed
Working memory

25. Wechsler (1958)
“[The grouping of subtests into Verbal and Performance areas]…does not imply that these are the only abilities involved in the tests…The subtests are different measures of intelligence, not measures of different kinds of intelligence, and the dichotomy of Verbal and Performance areas is only one of several ways in which the tests could be grouped.”
In: The measurement and appraisal of adult intelligence. (pg 64)

26. The structure of the WISC-IV
The WISC-IV has four specific cognitive domains (Indexes) which together contribute to the Full Scale IQ
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

27. The structure of the WISC-IV Each of the four Index scores is derived from a number of subtest scores. There are five supplemental subtests which can be substituted for a specified number of core subtests if needed.
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

28. Verbal Comprehension Subtests
SIMILARITIES (SI)
Individuals are presented with two words that represent common objects or concepts and asked to say how they are similar.
VOCABULARY (VC)
Younger individuals are shown pictures and asked to name them. Then individuals are asked to give definitions for words presented orally and visually.
COMPREHENSION (CO)
Individuals are asked to respond to questions requiring an understanding of social situations, reflecting common sense, social judgment, behaviour and conventional standards.
INFORMATION (IN) (Supplemental subtest)
Individuals answer questions that address a broad range of general knowledge topics.
WORD REASONING (WR) (Supplemental subtest)
Individuals are asked to identify the common concept
described in a series of clues.
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

29. Word Reasoning (supplemental)
Verbal Comprehension Index
“Let’s play a guessing game. Tell me what I’m thinking of.”

30. Let’s test the ceiling item…
This has never been seen or done before…
and it can make our lives better and easier…
and it is a product of the mind.
1 point: discovery, invention, innovation, technology, imagination, creativity, dream

31. Perceptual Reasoning Subtests
BLOCK DESIGN (BD)
Individuals use up to nine red and white blocks to re-create a model or a picture of a design within a specific time limit.
PICTURE CONCEPTS (PCn)
The individual is presented with two or three rows of pictures and chooses one picture from each row with common characteristics.
MATRIX REASONING (MR)
Individuals look at an incomplete matrix (made up of pictures or designs)
and selects the missing item from five options.
PICTURE COMPLETION (PCm) (Supplemental subtest)
Individuals have to point to or name an important part missing from a picture within a specific time.
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

32. Picture Concepts (core)
Perceptual Reasoning Index
“Pick one here..
“that goes with
one here..”
Sample items only: “Why do they go together?”

33. Matrix Reasoning

34. Working Memory Subtests
DIGIT SPAN (DS)
Digit Span requires the individual to do two distinct tasks; the first is to repeat orally presented numbers in the same order. Then the individual is asked to repeat orally presented numbers in reverse order.
LETTER-NUMBERING SEQUENCING (LN)
Individuals are read a sequence of numbers and letters and are asked to recall the numbers in ascending order and the letters in alphabetical order.
ARITHMETIC (AR) (Supplemental subtest)
Individuals solve a series of orally presented arithmetic problems within a specific time limit.
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

35. Letter-Number Sequencing
“Tell me the numbers first, in order, starting with
the lowest number. Then tell me the letters in
alphabetical order.”
Credit is given if produced “in order”
(i.e., correct sequence), even if letters are listed first.

36. Processing Speed Subtests
CODING (CD)
Individuals copy symbols that are paired with simple
geometric shapes or numbers within a specific time limit.
SYMBOL SEARCH (SS)
Individuals scan a search group (of abstract symbols) and
indicate if a target symbol/s matches any of the symbols in
the search group within a specific time limit.
CANCELLATION (CA) (Supplemental subtest)
Individuals scan both a random and structured arrangement of
pictures and marks target pictures within a specific time limit.
© Text, format, graphics and data Copyright Dr John Worthington all rights reserved ©

37. Cancellation (supplemental)
Processing Speed Index
“When I say go, draw a line through each animal. Work as
quickly as you can w/out making any mistakes. Tell me
when you are finished.”
Random vs Structured

38. Qualitative Descriptions (same)
Score
Classification
130 and above
120–129
110–119
90–109
80–89
70–79
69 and below
Very Superior
Superior
High Average
Average
Low Average
Borderline
Extremely Low

39. Reliability of WISC-IV

40. Validity of WISC-IV Correlates .89 with WISC-III Good at identifying:
Children who are intellectually gifted
Children with mild or moderate mental retardation
Children with reading, written expression & math disorders
Children with learning disabilities & ADHD

41. Wechsler Preschool & Primary Scale of Intelligence (WPPSI)
Downward extension of WAIS & WISC, originally for children from 4 to 6 years of age
First published in 1967
Latest version is WPPSI-III (2003), for children from 2 years 6 months to 7 years 3 months
Similar to WISC-IV, though much simpler

42. Psychometric Properties of WPPSI
Reliabilities:
For composite scales: .89 to .96
subtests: .83 to .95
Validity:
Correlations with other tests of intelligence for this age group range from low (.49 with K-ABC) to moderate (.74 to .90 with McCarthy, SB & other scales)