1. Outline David Wechsler – some history Wechsler’s Scales IQ scores
Index scores
Verbal subtests
Performance subtests
WAIS Psychometrics

2. David Wechsler (1896 – 1981)
Studied at Columbia University (M.A., 1917; Ph.D., 1925)
Went to France with US Army in 1919, then to London
Studied with Pearson & Spearman
Also with Anna Freud in Vienna
Studied physiological changes related to emotion with researchers Henri Pieron and Louis Lapique in Paris, 1920
His dissertation reported work on psycho-galvanic response and emotion.

3. David Wechsler Worked at NY’s Bellevue Hospital.
Unhappy with the Stanford-Binet
Content appropriate only for children
Rapport problems if used with adults
Produces only a single score
Norms not appropriate for adults
Binet’s emphasis on speed hurt older adults’ scores

4. Wechsler Scales 1939: the Wechsler-Bellevue, later called the WAIS.
1945: the Wechsler Memory Scale
1949: the children’s version, the WISC
1955: Wechsler Adult Intelligence Scale
1967: the WPPSI for children ages 2½ -7
1981: WAIS-R (revised form of 1955 test)
1997: WAIS-III

5. Wechsler Scales
“Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally and to deal effectively with his environment.”
David Wechsler (1939)
global: one score ultimately describes a person’s intellectual ability
aggregate: that one score is composed of a number of sub-scores

6. Wechsler’s original test
Wechsler believed that intellectual ability involves two major types of skills: verbal and performance abilities.
Each of these broad types includes a variety of specific skills that are assessed by the various subtests of the WAIS.
However, all these subtests measure g as well as specific skills

7. Full Scale IQ Verbal IQ Performance IQ 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
Index scores – 2 or more subtests related to an underlying ability can be summed to give an index score
VCI – Verbal Comprehension
WMI – Working Memory
POI – Perceptual Organization
PSI – Processing Speed

8. Wechsler test produced 3 IQ scores
Full-scale IQ:
reflects both verbal and performance IQs
most reliable and valid score extracted from WAIS
why do you think this is the most reliable?

9. Wechsler test produced 3 IQ scores
Verbal IQ:
Responses require person being tested to use language – to understand instructions or to make a response

10. Wechsler test produced 3 IQ scores
Performance IQ:
Performance subtests involve doing something, not just answering questions

11. Structure of the WAIS WAIS-III has four index scores:
verbal comprehension
working memory
perceptual organization
processing speed.
Index scores added recently because, with new subtests, factor analysis suggests these four factors

12. Index scores Verbal comprehension
assesses general verbal skills, such as verbal fluency, ability to understand and use verbal reasoning, and verbal knowledge
based on both formal and informal educational opportunities,

13. Index scores Working memory
“The blackboard of the mind” (Goldman-Rakic, 1992)
Encode information into STM, store it there, retrieve it when needed
Manipulate information (e.g., addition)
Thinking, learning, planning

14. Index scores Perceptual organization
Use visual, spatial, and visually-guided motor skills
Organize thoughts
Assesses comfort with new, unfamiliar situations
ability to examine a problem, draw upon visual-motor and visual-spatial skills, organize thoughts, create solutions, and then test them. It can also tap preferences for visual information, comfort with novel and unexpected situations, or a preference to learn by doing.

15. Index score Processing speed
The speed at which cognitive processes can be carried out
focus, scanning speed, sequentially ordering visual information
sensitive to motivation, difficulty working under time pressure.
biological
cultural factors have little impact

16. WAIS Verbal Tests Vocabulary Similarities Arithmetic Digit Span
Information
Comprehension
Letter-Number Sequencing
Vocabulary – ability to define words; very stable measure; resists deterioration; useful for estimating pre-morbid intelligence
Similarities – identify similarity in 15 pairs of items; increasing difficulty; items in a pair may be superficially different; shows interesting results in psychopathology (e.g., schizophrenia)
Arithmetic – 15 straightforward items; concentration, motivation, memory important
Digit Span – forward and backward; one digit per second; tests short-term memory
Information – test of knowledge; may be influenced by curiousity, interest in learning; alertness to environment
Comprehension – (a) What should be done in a given situation; (b) logical explanations for behavior; (c) define proberbs
Letter-Number Sequencing – new task; optional; 7 items to be reordered.

17. Vocabulary Subject is given one word at a time, asked to define it
Sensitive to word knowledge, linguistic development, acquired knowledge, verbal expression ability, crystallized intelligence
The best single measure of g
Correlation of vocabulary score with g is .83

18. Vocabulary Very stable
Resistant to effects of poor concentration in schizophrenia
Not affected by mild concentration trouble
Of all WAIS subtests, the one most resistant to brain damage
Thus, allows a good estimate of pre-morbid functioning

19. Similarities
Task is to say how two (superficially) dissimilar items might be similar
Evaluating details – which details are “diagnostic”?
Earlier items in series are known through experience (e.g., “In what way are a cake and a pudding alike?”)
Later items require abstract thinking (e.g., “How are affection and approval alike?”

20. Similarities Logical, abstract thinking Concept formation
Crystallized and fluid intelligence
With Information subtest, the second best for measuring g
Correlation with g =.79

21. Similarities
Of VCI (Verbal Comprehension Index) subtests, the one least affected by formal education or learning
Score on this subtest is impacted by psychopathology, and by brain damage – esp. left hemisphere lesions
Especially sensitive to damage in the left temporal and frontal lobes

22. Arithmetic
Assesses working memory, numerical reasoning, computation skill, concentration, retrieval from LTM
Influenced by emotional state
Correlation with g is r = .75
Sequential, acquired knowledge, fluid intelligence, short term memory (esp. auditory), concentration, auditory sequencing, long term memory,

23. Digit Span Repeat a series of up to 7 digits in correct order
Digits presented 1 per second
Tested both Forward (DSF) and Backward (DSB)
Attention, auditory memory and sequencing, short term memory, mental alertness, sequential processing, cognitive flexibility

24. Digit Span Average 6.4 digits forward, 4.7 backwards
DSF – DSB ≥ 5 suggests brain damage
Correlation with g: r=.57 (the worst)

25. Information
Acquired knowledge, crystallized intelligence, fund of information, range of general factual knowledge, long term memory
Affected by formal education opportunities
Correlation with g: r = .79 (2nd best)
Failure on easy items followed by success on harder items suggests retrieval difficulties
Resistant to psychopathology and brain damage – good estimate of pre-morbid functioning
E.g., Who wrote Tom Sawyer?

26. Comprehension 3 different kinds of questions:
Appropriate responses to hypothetical situations
Logical explanations for everyday actions
Proverb interpretations
Assesses social and moral reasoning, judgment, verbal concepts, knowledge of ordinary standards of behavior, practical information

27. Comprehension Rewards conventional responses, not creative ones
R Hem patients may score high (their L Hem intact so they know answers) but still behave inappropriately
g: correlation r = .77

28. Letter-number sequencing
Optional – not needed to compute IQ
Task is to re-order intermixed, randomly-sequenced numbers and letters
Taps STM, sequential reasoning ability, planning
g: correlation r = .65
Impaired by anxiety, weak attention focusing ability
Dropping a letter: attention problem
Mixing up letters: sequencing problem

29. WAIS Performance Tests
Picture completion
Digit symbol-coding
Block design
Matrix reasoning
Picture arrangement
Symbol search (optional)
Object assembly (optional)
Picture Completion – important missing detail to be supplied; 21 cards; pointing response; requires experienced examiner (where exactly is finger pointing?)
Digit-Symbol Coding – copy symbols into appropriate boxes (appropriate by a sort of code); 120 seconds to do as many as you can; dexterity; persistence; speed
Block Design – nine variously colored blocks; subject to rearrange blocks to produce design matching a target; reasoning, spatial relationships, visuo-motor co-ordination
Matrix Reasoning – new test; assess fluid intelligence; identify a pattern or relationship among non-verbal, figural stimuli; also measures abstract reasoning
Picture Arrangement – notice relevant details; notice cause-effect relationships; plan; 11 items, each with 3 related pictures – task: put the pictures in order to tell a story; may also tap social knowledge
Symbol Search – new; optional; taps speed of information processing; look for target geometric figure in set of 5 search figures; 60 items, 120 seconds
Object Assembly – put together puzzles as quickly as possible; see relationships between parts and whole; visual analysis; assembly skills; co-ordination

30. Picture Completion Task: say what detail is missing from a picture.
Timed response
Pointing response is allowed
Raises issue of pointing precision (trained examiner required)
Alertness, attention to detail
LTM (Visual)
Crystallized intelligence
R Hem skill
g: correlation r = .64

31. Digit Symbol Coding … 1 X 2 ╫ 3 9 ÷ 8 … 9 1 6 3

32. Digit Symbol Coding Visual STM Psychomotor speed
Visual-motor coordination
Visual sequencing
Accuracy & speed
g: correlation r = .59
Very sensitive to any kind of brain damage

33. Block Design
Assesses visual-motor coordination, visual analysis & synthesis, spatial visualization
Visual input, motor output
Fluid intelligence
Trial & error learning
g: correlation = .72
Affected by R Hem damage
Bizarre solutions may indicate dementia

34. Matrix Reasoning 4 types of stimuli:
pattern completion
classification
analogy
serial reasoning
Subject given a series of matrices and must say what goes in the empty cell Ō ō Ǒ ?

35. Matrix reasoning
Measures abstract thinking, nonverbal reasoning, analogy skill
Fluid intelligence
Visual organization
g: correlation r = .72

36. Picture Arrangement
Task is to put a series of (randomly-ordered) pictures into narrative order (so they tell a coherent story)
As if you found a comic strip jumbled up and had to order the frames sensibly
Non-verbal reasoning
Possibly social skill
Fluid & crystallized intelligence
Planning
Time concepts

37. Picture Arrangement
Failure may be due to visual problems (compare with Picture Completion)
g: correlation r = .66

38. Symbol Search Optional – not needed to compute IQ
Subject shown two target abstract symbols and asked whether either target appears in a set of ‘probe’ symbols
120 seconds allowed
How many can subject do in that time?

39. Symbol Search
Visual-motor coordination and speed, planning, STM, perceptual speed
Large practice effects in young adults
g: correlation r = .70

40. Object Assembly Subject given pieces of a puzzle
Task is to assemble pieces into a whole
Taps knowledge of part-whole relationships, visual-motor coordination, anticipation of relationships among parts
Fluid intelligence

41. Object Assembly Sensitive to cerebral damage, especially in R Hem
Sensitive to disorder called neglect
g: correlation r = .62

42. Scales and Norms for the WAIS
Determine raw score for each subtest.
Convert raw scores to standard scores, called scaled scores (M=10, SD=3)
Convery to standard scores using tables for age (13 age groups).
Subtest scaled scores are added, then converted to WAIS-III composite scores.
Three composite scores: Verbal, Performance, Full Scale, each with M=100, SD=15

43. Standardization of the WAIS
Standardized on a stratified sample of 2,450 adults representative of the US population aged
There were 200 cases per age group, except for the smaller numbers in the two oldest groups.
Still difficult to know the effects of self-selection since participants had to be invited and accept to be included.

44. Reliability of the WAIS
Internal consistency and test-retest reliabilities .95 or higher for full scale and verbal scores.
About .90 for performance and these index scores: perceptual organization, working memory, and processing speed.

45. Reliability of the WAIS
Internal consistency reliability for the subtests range from upper .70s to low .90s. Test-retest is about .83.
Generally, performance reliabilities are lower than verbal reliabilities on the subtests.
Why might that be?

46. Validity of the WAIS
We have a great deal of information on criterion-related and construct validity.
Factors analyses support use of 4 index scores.
Most widely used ability test today

47. Johnson et al. (2004)
Measured correlation between WAIS scores and two other test batteries:
Comprehensive Ability Battery (CAB)
Hawaii Battery + Ravens
These batteries varied in their subtests, but correlations were essentially perfect
Johnson, W., Bouchard, T.J., Krueger, R.F., McGue, M., Gottesman, I.I., (2004). Just one g: consistent results from three test batteries. Intelligence, 32,

48. Comprehensive Abilities Battery
1. Numerical Ability Computations including fractions, decimal divisions, square roots, etc. 2. Spatial Ability Interpretation of two-dimensional figural rotation or reversal. 3. Memory Span Recall of digits presented aurally. 4. Flexibility of Closure Identification of embedded figures. 5. Mechanical Ability Identification of mechanical principles and tools. 6. Speed of Closure Completion of gestalt. 7. Perceptual Speed Evaluation of symbol pairs. 8. Word Fluency Production of anagrams. 9. Inductive Reasoning Identification of pattern in sequences of letter sets. 10. Associative Memory Rote memorization of meaningless pairings. 11. Meaningful Memory Rote memorization of meaningful pairings. 12. Verbal—Vocabulary Multiple choice among possible synonyms. 13. Verbal—Proverbs Interpretation of proverbs. 14. Spelling Multiple-choice identification of misspellings.

49. Hawaii Battery + Ravens
15. Card Rotations Matching of rotated alternatives to probe. 16. Mental Rotation Identification of rotated versions of 2-D pre-presentation of 3-D objects. 17. Paper Form Board Outline of cutting instructions to form the target figure. 18. Hidden Patterns Identification of probe figures in more complex patterns. 19. Cubes Identification of matched figures after rotation. 20. Paper Folding Identification of unfolded version of a folded probe. 21. Raven Identification of analogous figure to follow a sequence of figures. 22. Vocabulary Multiple choice among possible meanings. 23. Subtractn/Multn Completion of two-digit subtractions and two-digit by one-digit multiplications. 24. Word Beg/Endings Generation of words beginning and ending with specified letters. 25. Pedigrees Identification of familial relationships within a family tree. 26. Things Categories Generation of things that share assigned characteristics. 27. Different Uses Generation of novel uses for specified objects. 28. Immed Vis Mem Recall of illustrations of common objects immediately following presentation. 29. Delay Visl Mem Recall of illustrations of same common objects after delay. 30. Lines and Dots Trace a path through a grid of dots. 31. Identical Pictures Identification of alternative identical to probe.

50. Johnson et al. (2004) Correlations:
WAIS – Hawaii Battery + Ravens 1.00
WAIS – Comprehensive Ability Battery 0.99
Hawaii – CAB
These results constitute strong evidence for g and show that the one-factor result does not depend upon particular tasks

51. WISC-III
Most popular test for assessing intellectual ability of children ages 6 years, 0 months to 16 years, 11 months.
Similar to structure of the WAIS, with easier items
Both tests yield verbal, performance, and full scale IQ and 4 index scores
Most of the subtests are the same
Differences:
Freedom from distractibility replaces working memory.
Subtest composition of the Verbal Comprehension and Perceptual organization index scores are slightly different.
Doesn’t have a letter-number sequencing or matrix reasoning subtest.
WISC-II does have a Mazes subtest.

52. Psychometric Properties of the WISC-III
Standardization program involved 2,200 cases selected to represent the US population of children aged 6-16.
Composite scores generally have internal consistency reliabilities in the mid-.90s and test-retest reliabilities around .90.
Subtest reliabilities are generally in the mid-.80s.
Object Assembly and Mazes are problematic, with reliabilities in the .60s.