Wechsler scales: David Wechsler

1

• Wechsler scales (David Wechsler)
• Wechsler-Bellevue (W-B) Intelligence Scale (1939)
  for adults 17 years of age
• WAIS (1955) -- Wechsler Adult Intelligence Scale
• WAIS-R (1981) all had six verbal and five
  performance scales VIQ, PIQ, FIQ
• WAIS-III (1997) Canadian version 2001
• Ages 16-89 years
• VIQ, PIQ, FIQ plus 4 index scores  Verbal
  Comprehension, Perceptual Organization, Working
  Memory, and Processing Speed

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• WAIS-III scales and subtests
• Verbal Scale
• Vocabulary give definition of words
• Similarities given pairs of words, how are they
  similar? (e.g., swimming pool/ baseball field)
• Arithmetic solve arithmetic problems
• Digit Span repeat series of numbers (forward or
  in reverse order)
• Information answer questions on knowledge
• Comprehension provide solution to problems
• Letter-number sequencing repeat sequence of
  letters and numbers in order (alphabetical or
  ascending numbers)

3

• Performance Scale
• Picture completion show missing part on picture
• Digit Symbol Coding match symbols to list of
  numbers using a key
• Block Design arrange coloured blocks to match
  design in picture
• Matrix Reasoning choose design to complete
  pattern of designs
• Picture Arrangement place pictures in logical
  order
• Symbol Search check off if target symbol occurs
  in a group of symbols
• Object Assembly puzzle assembly

4

• Interpretation
• Start broad then more specific
• FSIQ, then VIQ PIQ (differences), then factor
  scores
• Crystallized intelligence (learned) Vocabulary,
  Information
• Fluid intelligence (novel problem solving) Digit
  Span, Matrix Reasoning
• Examine percentile rank (compares to normative
  group)
• Differences between VIQ and PIQ can be due to
  education, brain damage, etc.

5

• Wechslers Scales for children (ages 6-17)
• WISC (1949) -- Wechsler Intelligence Scale for
  Children
• WISC-R (1974)
• WISC-III (1991) new norms, updated items
  subgroups of tests for factors of Verbal
  Comprehension, Perceptual Organization, and
  Freedom from Distractibility
• WISC-IV (2003)
• Verbal Comprehension Index (VCI)
• Perceptual Reasoning Index (PRI)
• Working Memory Index (WMI)
• Processing Speed Index (PSI)

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• WISC-IV Indexes and Subtests
• Verbal Comprehension Index
• Similarities
• Vocabulary
• Comprehension
• Information
• Word Reasoning (presented with clues, child
  describes underlying common concept)
• Perceptual Reasoning Index
• Block Design
• Picture Concepts
• Matrix Reasoning
• Picture Completion

7

• Working Memory Index
• Digit Span
• Letter-Number Sequencing
• Arithmetic
• Processing Speed Index
• Coding
• Symbol Search
• Cancellation (marks target pictures in a series
  that include certain arrangements)

8

• WWPSI-III (Wechsler Preschool and Primary Scale
  of Intelligence ages 2.5 to 7 years
• 14 subtests (not all are used each time)
• Similar content to WISC-IV but more age
  appropriate, less verbal, less timing of tests
• Main tests used for ages 4-7 years
• Information, Vocabulary, Word Reasoning (VIQ)
• Block Design, Matrix Reasoning, Picture Concepts
  (PIQ)
• Coding
• Can also assess processing speed and general
  language

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• Other Related Measures
• Kaufman Assessment Battery for Children and
  Kaufman Adolescent and Adult Intelligence Test
• Assesses style of learning rather than knowledge
  or skill areas
• E.g., Sequential Processing, Simultaneous
  Processing, Mental Processing Composite, and
  Achievement

10

• Wechsler Memory Scale (WMS-III)
• Immediate Memory
• Auditory Immediate
• Visual Immediate
• General Memory (delayed)
• Auditory delayed
• Visual delayed
• Auditory Recognition Delayed
• Working Memory

11

• WIAT-II (Wechsler Individual Achievement Test)
• For assessing academic and problem solving skills
• Helpful to compare to intelligence tests to
  determine discrepancies between intellectual
  functioning and academic achievement (to diagnose
  learning disabilities)
• Covers reading, math, written language, oral
  language skills

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Reliability Validity of the Wechsler scales

• Strong internal consistency reliability for the
  IQ scores (FSIQ, VIQ, PIQ) and factor scores for
  intelligence scales
• Slightly lower values for some individual scales
  (4 on the WAIS-III, 2 on the WISC-IV), hence,
  interpretation should rely less on these
• Canadian norms for the WAIS-III, WWPSI-III, and
  WISC-IV