Weschler Flashcards
difference with wechsler tests
One of the most influential advocates of the role of nonintellective factors in these tests
Emphasized that factors other than intellectual ability are involved in intelligent behavior
3 Wechsler Scales today
Wechsler Adult Intelligence Scale - 4th ED
Wechsler Intelligence Scale for children - 5th ed
Wechsler Preschool and primary scale of intelligence fourth edition
2 years after the Binet 1937 revision
Wechsler-Bellevue Intelligence scale challenged its supremacy as a measure of human intelligence
Objected to the single score offered by the 1937 binet scale
Did not directly measure nonintellective factors - took them into careful account in its underlying theory
Weshcler criticisms of Binet
- Binet scale items- selected for use with children W: lacked validity when answered by adults
- Examiner subject rapport was often impaired when adults were tested with the binet scale
- Correctly noted that binet scale emphasis on speed with timed tasks scattered throughout the scale - handicapped older adults
- Mental age norms clearly did not apply to adults
- Binet scale did not consider that intellectual performance could deteriorate as a person grew older - Modern binet has addressed these
2 critical differences between wechsler and binet:
1. Point Scale vs. Age Scale
1908 - 1972 Binet grouped by age level
Tasks that could be passed by ⅔-¾ of individuals at that age level
Age scale format: arrangement of items has nothing to do with their content
—–At a particular year level - reasoning, memory, numerical data
——Various types of content are scattered throughout the scale
On earlier binet scale - subjects did not receive a specific amount of points or credit for each task completed - need to pass 3 if you only pass 2 - no credit
Point scale - credits assigned to each item - easy to group items of a particular content together - wechsler did this
So powerful that a similar concept was used in the 1986 binet scale
Arranging items according to content and assigning a specific number of points to each item - intelligence test that yielded a total overall score and scores for each content area
Permitted analysis of individual’s ability in a variety of content areas - wechscler is standard today
2 critical differences between wechsler and binet:
Wechsler’s inclusion of a nonverbal performance scale
Binet criticized for emphasis on language and verbal skills
Wechscler included an entire scale that provided a measure of nonverbal intelligence - a performance scale —-Require subjects to do something rather than merely answer questions
Binet had some performance tasks but mostly at younger age levels - results of a subjects response to a performance task on binet were difficult to separate from the results for verbal tasks
Could not determine the precise extent to which a subject’s response to a nonverbal performance task increased or decreased the total score
Wechsler - 2 separate scales
First to offer the possibility of directly comparing an individual’s verbal and nonverbal intelligence - verbal and performance standardized on the same sample and expressed in comparable units
Performance scale
what does a performance scale do?
Performance scale attempts to overcome biases caused by language, culture and education,
provide a richer and more varied context,
require a longer interval of sustained effort,
concentration and attention than verbal tasks,
measure intelligence and provide clinician with a rich opportunity to observe behavior in a standard setting
Wechsler advantages: 3
- measure adult intelligence
-Items have content validity for adults
- Does not handicap older adults
- Considers intellectual deterioration with age - Separate scores based on category
-Credit received for each item passed
-Items grouped by content
-Yields multiple scores - Performance scale
Nonverbal measure of intelligence
Nonverbal/performance tasks grouped to
Wechsler-Bellevue Intelligence Scale to the WAIS-IV
First effort to measure adult intelligence - Wechsler-Bellevue scale was poorly standardized
Normative sample was not representative - 1081 whites from eastern US
1955 - revised into modern form Wechsler adult intelligence scale WAIS which was revised in 1981 WAIS-R, again in 1997 WAIS-III and again in 2008 WAIS-IV
Scales Subtests and Indexes
Like binet- Wechsler defined intelligence as the capacity to act purposefully and to adapt to the environment
Wechsler; intelligence comprised specific elements that one could individually define and measure - elements were interrelated - not entirely independent - global and aggregate
–Definition implies that intelligence comprises several specific interrelated functions or elements - general intelligence results from the interplay of these elements - modern research supports
—Theoretically - measuring each of the elements, one can measure general intelligence by summing the individuals capacities on each element
—-Wechsler tried to measure separate abilities - binet tried to avoid this when he adopted general mental ability
In all tests - wechslers basic approach is maintained
–Individual subtests - each related to a basic underlying skill or ability
–Each of the various subtests also part of a broader index
–WAIS IV 4 index - verbal comprehension, perceptual reasoning, working memory and processing speed. - Full scale is then based on the summed scores of these 4 indexes
—Index is created where two or more subtests are related to a basic underlying skill
Vocab Subtest
Ability to define words - not only one of the best single measures of intelligence but also the most stable
—-Appear on nearly every individual test that involves verbal intelligence
Deterioration bc of emotional factors or brain damage - vocab one of the last functions to be affected - stable
—-Mild concentration difficulties lower optimal performance on arithmetic and digit span tasks - such difficulties generally do not affect vocab until they become quite severe
—–Because its stable - use to estimate baseline or premorbid intelligence - what intellectual capacity was before an illness, brain injury etc.
Similarities Subtest
Consists of paired items of increasing difficulty
Subject must identify similarity between the items in each pair
Individuals with schizophrenia may give idiosyncratic concepts - concepts that have meaning only to them
Arithmetic Subtest
15 simple problems in increasing difficulty order
Few cases - intellectually disabled - artithmetic skills can play a significant role - but concentration, motivation and memory are the main factors underlying performance
Digit Span Subtest
Requires the subject to repeat digits, given at the rate of one per second, forward and backward
Measures short term auditory memory and is one of the core subtests in the working memory index
Nonintellective factors ie. attention, anxiety often influence the results
The Information Subtest
Items appear in order of increasing difficulty
Like all subtests, information subtest involves both intellective and nonintellective components including the abilities to comprehend instructions, follow directions and provide a response
Non-intellective factors such as curiosity and interest in the acquisition of knowledge tend to influence scores
Comprehension Subtest
3 types of questions
1. What should be done in a given situation
2. Provide a logical explanation for some rule or phenomenon
3. Define proverbs
Measures judgment in everyday practical situations or common sense
Emotional difficulties frequently reveal themselves on this subtest and lower the person’s score - ie. find an injured person and tell them i didnt do it
The Letter-Number Sequencing Subtest
Supplementary on the working memory index - not required to obtain an index score but may be used as a supplement for additional information about intellectual functioning
Made up of items - individual must reorder lists of numbers and letters
Related to working memory and attention
Digit symbol coding test
Subject copy symbols
After a short practice - 120 seconds to copy as many symbols as possible - measures ability to learn an unfamiliar task, visual motor dexterity, degree of persistence, speed of performance
Must have adequate visual acuity and appropriate motor capabilities to complete this subtest successfully and factors affect these capabilities such as age may affect the results
The Block Design Subtest
9 variously coloured blocks, booklet with pictures of the blocks arranged according to a specific geometric design or configuration
Subject must arrange the blocks to reproduce increasingly difficult designs
Requires subject to reason, analyze spatial relationships, integrate visual and motor functions
Input information - picture - visual but output response is motor
Excellent measure of nonverbal concept formation, abstract thinking, neurocognitive impairment - core measures of perceptual reasoning index scale in the WAIS-IV
Matrix Reasoning Subtest
Core subtest n perceptual reasoning index scale - enhance assessment of fluid intelligence - involves ability to reason
Subject presented with nonverbal, figural stimuli
Identify a pattern or relationship between the stimuli
Subtest is a good measure of information processing and abstract reasoning skills
Symbol Search Subtest
Relatively new subtest - core measure in the processing speed index scale - added in recognition of the role of speed of info processing in intelligence
Subject is shown two target geometric figures - task is then to search from among a set of 5 additional search figures and determine whether the target appears in the search group
The faster a subject performs this task, the faster their info processing speed will be
From Raw Scores to Scaled and Index Scale Scores
Each subtest produces a raw score - total number of points - has a different max total
To compare scores on individual subtests - raw scores can be converted to standard or scaled scores with a mean of 10 and a sd of 3
Deriving a subtest scaled score for the WAIS- IV - used inferential norming
Variety of statistical indexes or moments such as means and sds were calculated for each of the 13 age groups of the stratified normative sample
Plotted across age groups to derive estimates of age group midpoint population moments
Test developers were able to derive reference group norms - allow the test user to compare subjects at the subtest level
Four composite index scales are then derived by summing the core subtest scores
—Verbal comprehension index is determined from scaled scores on the vocabulary, similarities and information subtests
——Each of the four index scores was normalized to have a mean of 100 and a standard
Index Scores - Four scores
Four scores: verbal comprehension, perceptual organization, working memory and processing speed
Index - Verbal comprehension
Verbal comprehension index might be best thought of as a measure of crystallized intelligence
This index is a more refined, purer measure of verbal comprehension than is the verbal IQ because it excludes the arithmetic and digit span subtests - have attentional or working memory components
Perceptual reasoning index
- visual puzzles, block design and matrix reasoning - measure of fluid intelligence
Other factors influencing performance on this group of tests are attentiveness to details and visual motor integration
working memory index
Notion of working memory is perhaps one of the most important innovations on the modern WAIS
Working memory - information that we actively hold in our minds in contrast to our stored knowledge or long-term memory
Processing speed index
- attempts to measure how quickly mind works
20 sec vs 5 sec to solve problem
FSIQs
Follows the same principles of index scores
Obtained by summing the age-corrected scaled scores of all four index composites
Represents a measure of general intelligence
WAIS IV follows a hierarchical model with general intelligence at the top
Index scores form the next level with the subtests providing the base
General factor at the top followed by group factors and individual abilities
Interpretive Features of the Wechsler Tests
Index Comparisons
Wechsler offers a useful opportunity not offered by Binet - measures of nonverbal intelligence in conjunction with a nonverbal IQ measure
Nonverbal measures aid in the interpretation of the verbal measures - verbal comprehension subtest
VIQ in low ranges confirmed by a performance IQ in the low ranges - intellectually disabled but this diagnosis can not be made by IQ alone
Must also show significant deficits in adaptive functioning as well as an FSIQ below 70
If PIQ exceeds 100 but VIQ is 55 - unlikely that they are mentally disabled
Language, cultural or educational factors might account for the differences
—African american and caucasian groups - higher verbal than performance IQs
—Reverse for Filipinos
—No difference for Hispanics
—Not appropriate to make sweeping generalizations about the meaning of index discrepancies and should provide a warning as new research begins to look at comparisons among index scores
Pattern Analysis
Evaluate relatively large differences between subtest scaled scores
Wechsler reasoned that different types of emotional problems might have differential effects on the subtests and cause unique score patterns
Conversion disorders use denial and repression - lapses in long-term store of knowledge - low score on the information subtest
Schizophrenia - poor concentration and judgment - low on arithmetic and comprehension
Pattern analysis must be done cautiously - at best should be used to generate hypotheses - must be corroborated or refuted by other sources of data, such as historical information, medical records, family interviews and direct observation
Psychometric Properties of the Wechsler Adult Scale
Standardization
WAIS VI standardization sample consisted of a stratified sample of 2200 adults divided into 13 age groups
Stratified according to gender, race, and geogrphic region
Psychometric Properties of the Wechsler Adult Scale
Reliability
Impressive reliability coefficients for the WAIS IV attest to the internal and temporal reliability of the four index scores and full-scale IQ
Test-retest coefficients in manual only slightly lower
The technical manual reports an overall standard error of measurement of 2.16 for the FSIQ and 2.85 for the verbal comprehension index.
all tests possess a certain degree of measurement error. The standard error of measurement (SEM) is the standard deviation of the distribution of error scores- error score is the difference between the score actually obtained by giving the test and the score that would be obtained if the measuring instrument were perfect
SEM = SDsqrt1-rxx(reiiablity coefficient)
the SEM can be used to form a confidence interval within which an individual’s true score is likely to fall. More specifically, we can determine the probability that an individual’s true score will fall within a certain range a given percentage of the time. To be roughly at the 68% level, an obtained score must fall within the range of one SEM. The 95% confidence interval is approximately two SEMs
smaller SEM for the verbal comprehension index and full-scale IQs means that we can have considerably more confidence that an obtained score represents an individual’s true score than we can have for the other indexes. Thus, given an FSIQ of 110, we can assume that 95% of the time the subject’s true score would fall at (1/2) 4.32 (two SEMs) of the true score. In other words, 95% of subjects with a score of 110 have a true score between 105.68 and 114.32, and only 5% do not
Psychometric Properties of the Wechsler Adult Scale
Validity
validity of the WAIS-IV rests heavily on its correlation with earlier versions of the test. However, the Wechsler tests are considered among the most valid in the world today for measuring IQ
Evaluation of the Wechsler Adult Scales
reliability of the individual subtests is lower and therefore makes analysis of subtest patterns dubious for the purpose of making decisions about individuals.
WISC-V:
measures intelligence from ages 6 through 16 years, 11 months.
can be administered and scored by two coordinated iPads, one for the examiner and one for the subject being tested
administration is faster and more efficient
Standardization, reliability, and validity support provided in the interpretative manual are as good as or better than those of its predecessor, the WISC-IV, and most other individual test
heavily based on speed of a response based on the findings that faster responding is associated with higher ability for most tasks.
Descriptive classifications, such as very superior and borderline, have been replaced with more neutral sounding terms such as extremely high and very low
WISC-V: MODEL
Hierarchical structure - top of the hierarchy is FSIQ
Next- FIVE INDEXES or primary scores.
five indexes are called verbal comprehension, visual spatial, fluid reasoning, working memory, and processing speed.
Each index is associated with at least two subtest scores
FIVE ANCILLARY SCALES, each based on two or more subtests - is it really five different factors, or perhaps only four, three, two, or even one
f the factors are unstable, then comparing the index scores to make diagnostic conclusions would be dubious.
quantitative reasoning, auditory working memory, nonverbal, general ability, and cognitive processing
THREE COMPLEMENTARY SCALES
naming speed, symbol translation, and storage and retrieval.
number of special group studies, which support its validity
various specific learning disabilities, attention-deficit/hyperactivity disorder (ADHD), traumatic brain injury, and autism spectrum disorders. Numerous tables and findings are presented in the interpretative manual to aid clinicians
WPPSI-IV -
first published in 1967, revised in 1989 and 2003, and most recently in 2012, measures intelligence in children from 2.5 to 7 years, 7 months.
more flexible than its predecessors and gives the test user the option of using more or less subtests depending on how complete an evaluation is needed and how young the child is
Younger children required less testing.
General mental ability, or g, is at the top and reflected in the full-scale IQ.
Then, there are three group factors, represented by index or primary scores: verbal comprehension, visual spatial, and working memory.
—Finally, each of the indexes is composed of two or more subtest scores
—-the larger issue relates to the stability and validity of all three indexes factor analysis of the standardization sample best fits a bifactor structure. These authors concluded that the general g factor as represented by fullscale IQ accounted for more variance in every subtest than did its corresponding domain-specific factor, that is, index.
