The Wechsler The Wechsler Intelligence ScalesIntelligence Scales
The Wechsler Adult Intelligence The Wechsler Adult Intelligence Scale (WAIS)Scale (WAIS)
The first Wechsler intelligence scale, known as The first Wechsler intelligence scale, known as the Wechsler-Bellevue Intelligence Scale, was the Wechsler-Bellevue Intelligence Scale, was developed in 1939, two years after the 1937 developed in 1939, two years after the 1937 version of the Stanford-Binetversion of the Stanford-Binet
Developed in reaction to problems with the 1937 Developed in reaction to problems with the 1937 Stanford-BinetStanford-Binet• SB items had been selected for use with children, & SB items had been selected for use with children, &
weren’t really appropriate for adultsweren’t really appropriate for adults• SB had lots of timed tests, which made it difficult for SB had lots of timed tests, which made it difficult for
older adultsolder adults• SB did not consider that intellectual performance can SB did not consider that intellectual performance can
deteriorate as a person grew olderdeteriorate as a person grew older• SB produced only 1 scoreSB produced only 1 score
Point & Performance Scale Point & Performance Scale ConceptsConcepts
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
Performance Scale ConceptPerformance 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
The Wechsler Adult Intelligence The Wechsler Adult Intelligence Scale III (WAISIII)Scale III (WAISIII)
Most recent version of the adult intelligence scale Most recent version of the adult intelligence scale (there are also child & pre-school versions)(there are also child & pre-school versions)
Published in 1997Published 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
Subtests of WAISIIISubtests of WAISIIIVerbal SubtestVerbal Subtest Major Function MeasuredMajor Function Measured
VocabularyVocabulary Vocabulary levelVocabulary level
SimilaritiesSimilarities Abstract thinkingAbstract thinking
ArithmeticArithmetic ConcentrationConcentration
Digit spanDigit span Immediate memory, Immediate memory, anxietyanxiety
InformationInformation Range of knowledgeRange of knowledge
ComprehensionComprehension JudgmentJudgment
Letter-number Letter-number sequencing*sequencing*
Freedom from Freedom from distractibilitydistractibility
Performance SubtestPerformance Subtest Major Function Major Function MeasuredMeasured
Picture completionPicture completion Alertness to detailsAlertness to details
Digit symbol-codingDigit symbol-coding Visual-motor functioningVisual-motor functioning
Block designBlock design Nonverbal reasoningNonverbal reasoning
Matrix reasoningMatrix reasoning Inductive reasoningInductive reasoning
Picture arrangementPicture arrangement Planning abilityPlanning ability
Symbol search*Symbol search* Information-processing Information-processing speedspeed
Object assembly*Object assembly* Analysis of part-whole Analysis of part-whole relationshipsrelationships
ScoringScoring 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
Scaled score equivalents of raw scores: Scaled score equivalents of raw scores: 20 to 24 year old norms20 to 24 year old norms
Verbal IQ ScoreVerbal 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
Performance IQ ScorePerformance 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
Full-Scale IQ ScoreFull-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
Index ScoresIndex 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]
Structure of the ScaleStructure of the Scale
FSIQFSIQFSIQFSIQ
Digit SpanDigit SpanArithmeticArithmeticLetter–Number Letter–Number
SequencingSequencing
VocabularyVocabularySimilaritiesSimilaritiesInformationInformationComprehensionComprehension
Digit Symbol— Digit Symbol— CodingCodingSymbol SearchSymbol Search
Block DesignBlock DesignMatrix ReasoningMatrix ReasoningPicture CompletionPicture CompletionPicture ArrangementPicture Arrangement
VIQVIQVIQVIQ PIQPIQPIQPIQ
VCIVCIVCIVCI WMIWMIWMIWMI POIPOIPOIPOI PSIPSIPSIPSI
88
Plotting Subtest Scores (IQ)Plotting Subtest Scores (IQ)Plotting Subtest Scores (IQ)Plotting Subtest Scores (IQ)
1515
ReliabilityReliability
Split-HalfSplit-Half Test-RetestTest-Retest
Full ScaleFull Scale .98.98 .95.95
Verbal IQVerbal IQ .97.97 .94.94
Performance IQPerformance IQ .94.94 .88.88
For full-scale IQ, standard error of measurement For full-scale IQ, standard error of measurement is quite small, around 2 to 2.5 IQ pointsis quite small, around 2 to 2.5 IQ points
This means that an examinee’s true score will fall This means that an examinee’s true score will fall within 5 points either side of the obtained score within 5 points either side of the obtained score 95% of the time95% of the time
Reliability of SubtestsReliability of Subtests
Reliabilities for the subtests vary a Reliabilities for the subtests vary a great deal, and are lower than great deal, and are lower than reliabilities of the full-scale, verbal, reliabilities of the full-scale, verbal, performance IQ’s, and the four performance IQ’s, and the four indexesindexes
They range from low .70’s to They range from low .70’s to low .80’s, with some in the .60’slow .80’s, with some in the .60’s
Validity of the WAISValidity of the WAIS WAISIII correlates highly (mid 90’s) with earlier WAISIII correlates highly (mid 90’s) with earlier
versions of the WAISversions of the WAIS Correlation with SBIV is .88Correlation with SBIV is .88 Correlates significantly with grades in high school, Correlates significantly with grades in high school,
universityuniversity IQ and occupational attainment are also IQ and occupational attainment are also
significantly correlatedsignificantly correlated Predictions deriving from theory are borne out; fluid Predictions deriving from theory are borne out; fluid
intelligence supposedly declines more rapidly in old intelligence supposedly declines more rapidly in old age than crystallized intelligenceage than crystallized intelligence• Supported by finding that verbal subtests show minimal Supported by finding that verbal subtests show minimal
decrement with age, while performance subtests drop decrement with age, while performance subtests drop markedlymarkedly
Conry & Plant (1965)Conry & Plant (1965)
Interpreting the WAISInterpreting the WAIS
Verbal-Performance IQ ComparisonsVerbal-Performance IQ Comparisons• Neurological impairmentNeurological impairment may be indicated may be indicated
when one of the scales falls in the low average when one of the scales falls in the low average or lower range, and the other in the average or or lower range, and the other in the average or higher rangehigher range
• Emotional traumaEmotional trauma may be indicated if the may be indicated if the client has a low verbal or performance IQ that client has a low verbal or performance IQ that does not seem to match their past level of does not seem to match their past level of functioningfunctioning
• Language-related learning difficultyLanguage-related learning difficulty may may be indicated by an low verbal IQ and average be indicated by an low verbal IQ and average or high performance IQor high performance IQ
Case Study: Stephen GouldCase Study: Stephen Gould
High Stakes?High Stakes?Atkins vs. the State of Atkins vs. the State of
VirginiaVirginia
The Wechsler Intelligence The Wechsler Intelligence Scale for Children (WISC)Scale for Children (WISC)
First published in 1949First published in 1949 Revised in 1974, 1991Revised in 1974, 1991 Current version is WISC-IV, published Current version is WISC-IV, published
in 2003in 2003
WISC-IVWISC-IV
Measures intelligence from ages 6 through Measures intelligence from ages 6 through 1616
Contains 15 subtestsContains 15 subtests Abandons VIQ-PIQAbandons VIQ-PIQ Instead produces four major indices:Instead produces four major indices:
• Verbal comprehensionVerbal comprehension• Perceptual reasoningPerceptual reasoning• Processing speedProcessing speed• Working memoryWorking memory
Wechsler (1958)Wechsler (1958)
““[The grouping of subtests into Verbal and [The grouping of subtests into Verbal and Performance areas]…does not imply that these Performance areas]…does not imply that these are the only abilities involved in the tests…The are the only abilities involved in the tests…The subtests aresubtests are different measures of intelligence, different measures of intelligence, not measures of different kinds of intelligencenot measures of different kinds of intelligence, , and the dichotomy of Verbal and Performance and the dichotomy of Verbal and Performance areas is areas is only one of several ways in which the only one of several ways in which the tests could be groupedtests could be grouped.”.”
In: The measurement and appraisal of adult intelligence. (pg 64)
The structure of the WISC-IVThe structure of the WISC-IV
The WISC-IV has four specific cognitive domains (Indexes) which The WISC-IV has four specific cognitive domains (Indexes) which together contribute to the Full Scale IQ together contribute to the Full Scale IQ
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FULL Scale IQFULL Scale IQ
Verbal Verbal ComprehensionComprehension
Perceptual Perceptual ReasoningReasoning
Working Working
MemoryMemoryProcessing Processing
SpeedSpeed
WISC-IV Full Scale IQWISC-IV Full Scale IQ
Verbal ComprehensionVerbal ComprehensionIndexIndex
Working MemoryWorking MemoryIndexIndex
Processing SpeedProcessing SpeedIndexIndex
Perceptual Reasoning Perceptual Reasoning IndexIndex
BDBDSISI VCVC COCO PCnPCn MRMR DSDS LNLN CDCD SSSS
The structure of the WISC-IVThe structure of the WISC-IV
Each of the four Index scores is derived from a number of subtest scores. 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 There are five supplemental subtests which can be substituted for a specified
number of core subtests if needed.number of core subtests if needed.
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SIMILARITIES SIMILARITIES (SI)(SI)Individuals are presented with two words that represent common objects Individuals are presented with two words that represent common objects or concepts and asked to say how they are similar. or concepts and asked to say how they are similar.
VOCABULARY VOCABULARY (VC)(VC)Younger individuals are shown pictures and asked to name them. Then Younger individuals are shown pictures and asked to name them. Then individuals are asked to give definitions for words presented orally and individuals are asked to give definitions for words presented orally and visually.visually.
COMPREHENSION COMPREHENSION (CO)(CO)Individuals are asked to respond to questions requiring an Individuals are asked to respond to questions requiring an understanding of social situations, reflecting common sense, social understanding of social situations, reflecting common sense, social judgment, behaviour and conventional standards. judgment, behaviour and conventional standards.
INFORMATION INFORMATION (IN)(IN) (Supplemental subtest)(Supplemental subtest)Individuals answer questions that address a broad range of general Individuals answer questions that address a broad range of general knowledge topics.knowledge topics.
WORD REASONING WORD REASONING (WR)(WR) (Supplemental subtest)(Supplemental subtest)Individuals are asked to identify the common concept Individuals are asked to identify the common concept described in a series of clues. described in a series of clues.
Verbal Comprehension SubtestsVerbal Comprehension Subtests
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Word Reasoning (Word Reasoning (supplementalsupplemental))Verbal Comprehension Index
“Let’s play a guessing game. Tell me what I’m thinking of.”
Let’s test the ceiling item…Let’s test the ceiling item…
This has never been seen or done before…This has never been seen or done before…
and it can make our lives better and easier…and it can make our lives better and easier…
and it is a product of the mind.and it is a product of the mind.
1 point1 point: discovery, invention, innovation, : discovery, invention, innovation, technology, imagination, creativity, technology, imagination, creativity, dreamdream
BLOCK DESIGN BLOCK DESIGN (BD)(BD)Individuals use up to nine red and white blocks to re-create a 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.model or a picture of a design within a specific time limit.
PICTURE CONCEPTS PICTURE CONCEPTS (PCn)(PCn)The individual is presented with two or three rows of pictures and The individual is presented with two or three rows of pictures and chooses one picture from each row with common characteristics. chooses one picture from each row with common characteristics.
MATRIX REASONING MATRIX REASONING (MR)(MR)Individuals look at an incomplete matrix (made up of pictures or Individuals look at an incomplete matrix (made up of pictures or designs)designs)and selects the missing item from five options.and selects the missing item from five options.
PICTURE COMPLETION PICTURE COMPLETION (PCm) (PCm) (Supplemental subtest)(Supplemental subtest)Individuals have to point to or name an important part missing Individuals have to point to or name an important part missing from a picture within a specific time.from a picture within a specific time.
Perceptual Reasoning SubtestsPerceptual Reasoning Subtests
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Picture Concepts (Picture Concepts (corecore))Perceptual Reasoning Index
“Pick one here..
“that goes with one here..”
Sample items only: “Why do they go together?”
Matrix ReasoningMatrix Reasoning
DIGIT SPAN DIGIT SPAN (DS)(DS)Digit Span requires the individual to do two distinct tasks; Digit Span requires the individual to do two distinct tasks; the first is to repeat orally presented numbers in the same the first is to repeat orally presented numbers in the same order. Then the individual is asked to repeat orally order. Then the individual is asked to repeat orally presented numbers in reverse order.presented numbers in reverse order.
LETTER-NUMBERING SEQUENCINGLETTER-NUMBERING SEQUENCING (LN) (LN)Individuals are read a sequence of numbers and letters and Individuals are read a sequence of numbers and letters and are asked to recall the numbers in ascending order and the are asked to recall the numbers in ascending order and the letters in alphabetical order.letters in alphabetical order.
ARITHMETIC ARITHMETIC (AR)(AR) (Supplemental subtest) (Supplemental subtest)Individuals solve a series of orally presented arithmetic Individuals solve a series of orally presented arithmetic problems within a specific time limit.problems within a specific time limit.
Working Memory SubtestsWorking Memory Subtests
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Letter-Number SequencingLetter-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.
CODING CODING (CD)(CD)Individuals copy symbols that are paired with simpleIndividuals copy symbols that are paired with simplegeometric shapes or numbers within a specific time limit.geometric shapes or numbers within a specific time limit.
SYMBOL SEARCH SYMBOL SEARCH (SS)(SS)Individuals scan a search group (of abstract symbols) andIndividuals scan a search group (of abstract symbols) andindicate if a target symbol/s matches any of the symbols inindicate if a target symbol/s matches any of the symbols inthe search group within a specific time limit.the search group within a specific time limit.
CANCELLATION CANCELLATION (CA)(CA) (Supplemental subtest) (Supplemental subtest)Individuals scan both a random and structured arrangement ofIndividuals scan both a random and structured arrangement ofpictures and marks target pictures within a specific time limit.pictures and marks target pictures within a specific time limit.
Processing Speed SubtestsProcessing Speed Subtests
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Cancellation (Cancellation (supplementalsupplemental))Processing Speed Index
Random vs Structured
“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.”
Qualitative Descriptions Qualitative Descriptions (same)(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
Reliability of WISC-IVReliability of WISC-IV
Validity of WISC-IVValidity of WISC-IV
Correlates .89 with WISC-IIICorrelates .89 with WISC-III Good at identifying:Good at identifying:
• Children who are intellectually giftedChildren who are intellectually gifted• Children with mild or moderate mental Children with mild or moderate mental
retardationretardation• Children with reading, written Children with reading, written
expression & math disordersexpression & math disorders• Children with learning disabilities & Children with learning disabilities &
ADHDADHD
Wechsler Preschool & Primary Wechsler Preschool & Primary Scale of Intelligence (WPPSI)Scale of Intelligence (WPPSI)
Downward extension of WAIS & Downward extension of WAIS & WISC, originally for children from 4 to WISC, originally for children from 4 to 6 years of age6 years of age
First published in 1967First published in 1967 Latest version is WPPSI-III (2003), for Latest version is WPPSI-III (2003), for
children from 2 years 6 months to 7 children from 2 years 6 months to 7 years 3 monthsyears 3 months
Similar to WISC-IV, though much Similar to WISC-IV, though much simplersimpler
Psychometric Properties of WPPSIPsychometric Properties of WPPSI
Reliabilities:Reliabilities:• For composite scales: .89 to .96For composite scales: .89 to .96• subtests: .83 to .95subtests: .83 to .95
Validity:Validity:• Correlations with other tests of Correlations with other tests of
intelligence for this age group range intelligence for this age group range from low (.49 with K-ABC) to moderate from low (.49 with K-ABC) to moderate (.74 to .90 with McCarthy, SB & other (.74 to .90 with McCarthy, SB & other scales)scales)