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

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.

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

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

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

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

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

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?

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

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

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

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,

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

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.

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

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.

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

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

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?”

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

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

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,

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

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

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?

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

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

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

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

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

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

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

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

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 ?

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

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

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

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?

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

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

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

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

Standardization of the WAIS Standardized on a stratified sample of 2,450 adults representative of the US population aged 16-89. 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.

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.

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?

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

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, 95-107.

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.

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.

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

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.

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.