Wechsler Intelligence Scale Third Edition

“ The global capacity to act purposefully, to think rationally, and to deal effectively with one's environment”

“Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally and to deal effectively with his environment.”

◦Global because it characterizes individual’s behavior as a whole

◦Aggregate because it is composed of elements or abilities that are qualitatively differentiable

Why did Wechsler create his own test if Binet already made one?

Binet’s test does not go with his philosophy of what intelligence is..

Opposition on Binet’s focus on language and verbal skills to measure intelligence

Capitalized that since Binet’s intelligence scale if for children he concluded that it lacked validity when answered by adults

Binet’s emphasis on time handicaps older adults It did not consider that intellectual performance

deteriorates as a person grows older Mental age norms clearly did not apply to adults

Goal 1: Continuity and FamiliarityGoal 2: Updating of NormsGoal 3: Extension of Age RangeGoal 4: Age-Corrected NormsGoal 5: Improved Item ContentGoal 6: Improved Stimulus MaterialsGoal 7: Improved Diagnostic and

Descriptive Utility

Goal 8: De-emphasis on Performance SpeedGoal 9: Enhancement of Fluid Reasoning AssessmentGoal 10: Linkage with WMS–III and WIATGoal 11: Extensive Validity StudiesGoal 12: Enhancement of Scoring Rules

Individual Administration Assessment of Cognitive Functioning in

Adults, Aged 16–89 Years Scale Composition

◦ 11 Subtests to Obtain IQ Scores◦ 11 Subtests to Obtain Index Scores◦ New Subtests: Matrix Reasoning, Symbol Search,

Letter–Number Sequencing◦ Optional Subtest: Object Assembly

Age Sex Race/Ethnicity Education Level Geographic Region

66

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

WAIS–III

200 200 200 200 200 200 200 200 200 200 200 150 100

WMS–III

100 100 100 100 100 100 100 100 100 100 100 75 75

45–54

- Credits or points are assigned to each item- An individual receives a specific amount of

credit for each item passed unlike Binet- This scale makes it easier to group items of

particular content together- The test yielded not just an overall score

but also a score for each individual ability in a variety of content area

A measure for nonverbal intelligence Individual’s comparison of verbal and non-

verbal intelligence Used to overcome biases in language,

culture and educational background. Provides clinician an opportunity to observe

behavior in standard setting because performance test requires longer interval of sustained effort, concentration and attention than verbal tasks

Structure of WAIS IIIStructure of WAIS III

FSIQFSIQFSIQFSIQ

- Digit Span- Digit Span- Arithmetic- Arithmetic- Letter–Number - Letter–Number

SequencingSequencing

- Vocabulary- Vocabulary- Similarities- Similarities- Information- Information- Comprehension- Comprehension

- Digit Symbol— - Digit Symbol— CodingCoding- Symbol Search- Symbol Search

- Block Design- Block Design- Matrix Reasoning- Matrix Reasoning- Picture Completion- Picture Completion- Picture Arrangement- Picture Arrangement

VIQVIQVIQVIQ PIQPIQPIQPIQ

VCIVCIVCIVCI WMIWMIWMIWMI POIPOIPOIPOI PSIPSIPSIPSI

Verbal Scales - consists of subsets that requires verbal response

Performance Scales - consists of subsets that require the individual to respond by performing such as pointing to a missing detail

Vocabulary Similarities Arithmetic Digit span Information Comprehension Letter-number sequencing

Is the ability to define words The most stable measure of intelligence Individuals that show deterioration because of

emotional or brain damage shows that the vocabulary subtests to be the last one affected.

Mild concentration difficulties that lower optimal performance do not affect vocabulary until they become severe.

Used to evaluate premorbid intelligence in some cases

Measures the degree to which one has learned, been able to comprehend and verbally express vocabulary 

Consists of 15 paired items of increasing difficulty

Easier items just need responses from previously learned associations i.e. ( How is bread and water alike?) while difficult items require abstract thinking as they are already dissimilar objects i.e. (how is an ant and rose alike?)

Character of person’s thought processes is seen in many cases i.e. (schizophrenic giving idiosyncratic concepts)

Measures abstract verbal reasoning

Contains 15 relatively simple problems Retaining figures in memory while

manipulating it is the challenge Sample of ninth most difficult question: “A person with $28 spends $.50, how much

does he have left?” The main aspect measured is concentration,

memory and reasoning

Requires the subject to repeat digits, given at the rate of one per second, forward and backward.

Measures short-term auditory memory Some non intellective factors that might

influence the results are anxiety Measures attention, concentration and

mental control 

Measure subject range of knowledge Factors that tends to influence the test

scores are subjects curiosity and acquisition of knowledge, alertness to environment and alertness to cultural opportunities.

Asks three type of questions: - What should be done in a given situation - Provision of a logical explanation for a rule

or phenomenon - Definition of proverbs Measures judgment and common sense Emotional difficulties may affect the score

of a subject

One of the newest of WAIS III subtest Not required to obtain verbal IQ score Made up of seven items in which subject is

asked to reorder lists of numbers and letters.

It measures working memory and attention

Picture completion Digit symbol-coding Block design Matrix reasoning Picture arrangement Object assembly Symbol search

Subject is shown a picture wherein some important detail is missing while timed

Visual discrimination is measured Some factors that may affect the score are

visual-perceptual difficulties or environmental awareness

Subjects are given 120 seconds to copy numbers from 1-9 each paired with a symbol as much as they can

Measures visual-motor dexterity, degree of persistence, speed of performance and ability to learn an unfamiliar task

Age, inadequate visual acuity and motor capabilities may affect the results

Materials used are nine variously colored blocks and a booklet with specific geometric design or configuration

Subject must arrange the block in increasingly difficult designs

Measures nonverbal concept formation, abstract thinking and neurocognitive impairment

Enhances WAIS III assessment of fluid intelligence

Subject is presented with a nonverbal, figural stimuli and is tasked on finding a pattern or relationship between the stimuli

Measures abstract reasoning, information processing and fluid intelligence

Requires subjects to notice relevant details, cause and effect relationships.

The test consists of 11 items, which consists of related pictures similar to comic strips, the subject must arrange the pictures in the right order to tell a story

Measures nonverbal reasoning ability and interpretation of social situations

Consists of puzzles that the subject have to put together as quickly as possible

Measures visual assembly and its coordination with simple assembly skills

Subject is shown two geometric figures. The task is then to search from among a set of 5 additional search figures and determine whether the target appears in the search group. There are 60 items for which they are given 120 sec.

It measures cognitive processing abilities

FSIQ, VIQ, PIQ and Index Scores

Obtained by summing the age-corrected scaled scores of the verbal subtests with the performance subtests and comparing the subject to the standardization sample

Raw scores from the 5 performance scores are converted to scaled scores

PIQ is obtained by summing the age-corrected scaled scores on the performance subtests and comparing it with the standardization sample

VIQ is obtained by summing the age-corrected scaled scores on the verbal subtests and comparing it with the standardization sample

Vocabulary Similarities Information

• Arithmetic• Digit Span• Letter–

Number Sequencing

• Picture Completion

• Block Design• Matrix Reasoning

• DigitSymbol—Coding

• Symbol Search

Verbal Comprehensio

n

Perceptual Organization

WorkingMemory

ProcessingSpeed

Measures acquired knowledge and verbal reasoning (crystallize intelligence)

“Purer” measure for verbal IQ because of exclusion of arithmetic and digit span test

Measures Fluid Intelligence Factors that influence performance are

attentiveness to details and visual motor integration

Measures  the ability to actively hold information in the mind needed to do complex tasks such as reasoning, comprehension and learning

Measures How fast your mind works

Standardization, Validity and Reliability

Consisted of 2450 adults divided into 13 age groups from 16-17 through 85-59 then the sample is stratified according to gender, race, education and geographic region.

Split Half method used on all subtests except speeded test

Average coefficients are .98 FSIQ, .97 VIQ and .94 PIQ

Test retest coefficients are .95 FSIQ, .94 VIQ and .88 PIQ

Standard error of measurements are 2.29 FSIQ, 2.50 VIQ and 3.75 PIQ

95% confidence interval i.e. ( 95% with a 110 IQ score has a true score between 105.42 and 114.58 and only 5% do not.

It rests on its correlation with the earlier WAIS-R and WISC-III (where the ages overlap)

WAIS III correlate with the third edition of WISC with .94 VIQ, .86 PIQ and .93 FSIQ.

Verbal and Performance Comparisons Pattern Analysis

Provides a measure of nonverbal intelligence in conjunction with verbal intelligence

i.e. Subject has VIQ of 55 but has PIQ of 100 even though the FSIQ falls into 70 it doesn't mean the individual is retarded rather the difference might be attributed to environmental variables (language, cultural and educational factors)

Evaluation of relatively large differences between subtest scaled scores

As stated earlier different factors might affect the performance of the subject in a subtest thus using pattern analysis this factors can be isolated.

Raw scores are converted to scaled scores with a mean of 10 and SD of 3

The norms derived for this conversions are: age adjusted and reference group norms

Age adjusted norms are created by preparing a normalized cumulative frequency distribution of raw scores from each age group.

Reference group norms are based from the performance of participants in the standardization sample

SUBTESTS Raw Score VERBAL PERF. VC PO WM PS

Reference Group Scaled Scores

Age-Adjusted Scaled Scores

Picture Completion 22 12 12 12 Vocabulary 56 13 13 15

Digit-Symbol Coding 54 7 7 6

Similarities 28 12 12 13 Block Design 41 11 11 10Arithmetic 11 8 8 9

Matrix Reasoning 20 13 13 12

IQ/Index Scores VIQ PIQ FSIQ

Sums of Scaled Scores

62 55 117

IQ/Index Scores 101 106 103

Percentiles 53 66 58

Confidence Intervals95%

96-106 99-112 99-107

13 9.57 3.43 2.10 5 <5%

12 9.57 2.43 2.77

8 9.57 –1.57 2.63

7 9.57 –2.57 2.40 W >25%

1 1 9.57 1.43 2.34

1 1 9.57 1.43 2.96

SUBTESTSScaled Score

Vocabulary

Similarities

Arithmetic

Digit Span

Information

Mean Score

Difference from Mean

Statistical Significance .

05 LevelStrength

(+)Weakness

(–)

Frequency of Difference in

Standardization Sample

Total

÷ No. of SubtestsMean Score

67 70 = 137

7 7 ÷ 14

9.57 10 9.79Overall Mean

Comprehension

101 106 -5 8.48

110 111 -1 9.78

110 80 30 9.08 2.3%

111 79 32 12.13 2.6%

DISCREPANCY COMPARISONS

Verbal IQ

–Performance IQ

Verbal Comprehension – Perceptual Organization

Verbal Comprehension

– Working Memory

Perceptual Organization – Processing Speed

Score1

Score2

DifferenceStatistical Significance .05 Level

Frequency of Difference in

Standardization Sample

VIQ PIQ

VCI POI

VCI WMI

POI PSI

Digits Forward – Backward 7 5 2 60%

FWD BKWD