Intelligence Testing: Yesterday and Today
- Due to under-education, and to measure mental abilities, intellectual tests were developed.
- Binet-Simon test looked at individual differences in mental functioning (focus academic ability).
- 1971: Court Case Larry P. vs. Wilson Riles—California supreme court in 1975 placed a moratorium on using IQ tests on African-Americans.
Review of Reliability
- Reliability—consistency with which individuals respond to test stimuli. The types are:
- Test-Retest: Consistency of responses to the same test stimuli on repeated occasions.
o May lead to “test-wiseness” that influences their scores the second time or clients may show practice effects.
- Equivalent-Forms: Equivalent or parallel forms of a test are developed (ex: test forms A, B, C with different colors for an exam).
- Split-Half: Test is divided into halves (or odd numbered items vs. even numbered items) & participant's scores on the two halves are compared (allows for internal-consistency reliability).
- Internal Consistency: Do the items on a test measure the same thing? Index of internal consistency, average of split half correlations is made (Cronbach's alpha).
- Inter-Rater: Independent observers agree about their ratings of an aspect of someone's behavior.
- Reliability needs to be consistent in all forms, otherwise it won't be valid at all; and reliability does not automatically equal validity.
Measures for Reliability
- Test-Retest reliability: Pearson's r and Interclass correlation
- Equivalent forms reliability: Person's r
- Split-half reliability: Pearson's r
- Internal consistency reliability: Cronbach's alpha and Kuder-Richardson-20
- Inter-rater reliability: Person's r and Interclass correlation Kappa
Review of Validity
- Validity: An assessment technique measures what it is supposed to measure
- Content Validity: Measures comprehensiveness in assessing the variable of interest (does it measure all areas of the construct of interest).
- Predictive Validity: Type of criterion-related validity. Extent to which test scores indicate some behavior or event in the future.
- Concurrent Validity: Type of criterion-related validity. Extent to which test scores correlate with scores on other relevant measures given at the same time.
- Construct Validity: Extent to which test scores demonstrates all aspects of validity in a consistent manner (involves both convergence and discriminant validity demonstration).
Definitions of Intelligence—3 Classes Emphasize (are not mutually exclusive definitions):
- Adjustment or adaptation to the environment—adapting to situations or dealing with situations.
- Ability to learn—educability in the broad sense of the term
- Abstract thinking—ability to use a wide range of symbols and concepts, ability to use verbal and numerical symbols.
Theories of Intelligence
Factor Analytic Approaches
- Spearman—general intelligence g (general tests) and specific intelligence s (unique test aspects).
- Spearman viewed intelligence as a broad generalized entity. Used principal components.
- Thrustone—viewed intelligence as a series of “group factors” not the basic Used principal factors.
o 7 factors (Thurstone's Primary Mental Abilities)
- Spearman and Thurstone also used different data sets (broad range vs. academic institutions).
Cattell's Theory (Hierarchical Model of Intelligence)
- Emphasized He developed 17 ability concepts. Divided Spearman's g into 2 components:
o Fluid Ability: Genetically based intellectual capacity
o Crystallized Ability: Capacities that are tapped by intelligence tests, (culture based learning).
Guilford's Classification (Viewed as a classification or taxonomy; not really a theory)
- Structure of Intellect Model (SOI)—used model as a guide in generating data.
- Intelligence components can be divided into 3 areas: operations, contents and products.
- Operations: Cognition, memory, constructing logic alternatives, arguments, evaluation.
- Content: Areas of information in which the operations are performed (figural, symbolic, semantic and behavioral).
- Products: When a mental operation is applied to a context there are 6 types of products.
o Units, classes, systems, relations, transformations and implications.
Gardner's Theory of Multiple Intelligences (Viewed as "Talents" not intelligences)
- Gardner—theory of multiple intelligences (8 intelligences):
o Linguistic, Musical, Logical-Mathematical, Spatial, Bodily-Kinesthetic, Naturalistic, Interpersonal and Intrapersonal.
Sternberg's Triarchic Theory of Intelligence
- People function on the basis of three aspects of intelligence: componential, experiential and contextual.
- Emphasis on planning responses and monitoring them and de-emphasis on speed & accuracy.
- Componential: Analytical thinking (good test-taker)
- Experiential: Creative thinking (combine separate elements of experience
- Contextual: “street smart”—practical, can play the game and manipulate the environment.
Today's Focus—More on Spearman + Thurstone Contributions
- Focus is largely still on a single IQ or Spearman's
- Current intelligence tests are made up of subtest scores (Thurstone factors).
The IQ: It's Meaning and It's Correlates—The Intelligence Quotient (IQ)
- Mental Age (MA): Index of mental performance (X items passed)
- Chronological Age (CA): Individual's given age
- IQ: Used to overcome differences cause by CA and MA to express deviance
- IQ= MA/CA x 100
- IQ measurement is not one of equal-interval measurement and we can't add & subtract (so IQ of 100 is not twice IQ of 50).
- Ratio IQ is limited and not fully applicable to older age groups.
- Compares an individual's performance on IQ test with his/her same age peers .
- Same IQ has a different meaning for different ages (ex: same IQ for 22 year vs. 80 year old).
Correlates of the IQ: School Success, Occupational Status and Success, Demographic Group Differences
o General IQ shows success in school and specific tests measure what area.
o IQ scores + grades correlation—.50
o Based on educational level acquired (income, race, prestige...)
o IQ also good predictors of job performance
- Demographic Group
o Differences between sexes for specific abilities; males on spatial and quantitative ability and females on verbal ability.
o Hispanic & African Americans have lower IQ scores than North or European Americans.
Heredity and Stability of Intelligence
- Intelligence is influenced by genetic factors (behavioral genetics)
- Similarity in intelligence is a result of the amount of genetic material shared (monozygotic more similar than dizygotic twins or siblings).
- IQ variance associated with genetics varies from 30% to 80%.
- Environment plays a role—biological relatives raised together are more similar.
- Heritability of intelligence is not stable; 20% in infancy and 60% in young adults, 80% in old age.
Stability of IQ Scores and the Flynn Effect
- IQ Scores tend to be less stable for children and more stable for adults and more influenced at a younger age for children than for adults (i.e. environment).
- Flynn Effect: From 1972 onwards Americans IQ scores on average have increased 3 points each decade.
The Clinical Assessment of Intelligence Scale 1: The Stanford-Binet Scales
Stanford-Binet 1972 revised test kit version followed a fourth revision in 1986 and the most recent revision in 2003—Stanford-Binet Fifth Edition (SB-5)
- Hierarchical Model of Intelligence; 5 factors that tap non-verbal & verbal abilities.
- Fluid Reasoning: Ability to solve new problems. Measured by sub-tests
- Quantitative Reasoning, Visual-Spatial Processing, Working Memory and Knowledge
- Each sub-test is made up of items of varying difficulty (age 2-adulthood)
- Multistage Testing: Two routing subtests the Object-Series Matrices and Vocabulary subtest
o Routing: Examinee's performance on these two sub-tests determine which item to start with for each remaining subtest.
Standardization and Reliability and Validity:
- Included 4,800 participants aged 2-96 years old; participants were tested using various areas.
- SB-5 administered to individuals with disability, mental retardation to ensure utility of scores.
- Comparing Stanford-Binet to other scales like Wechsler Scales; the scale has strong validity.
The Clinical Assessment of Intelligence Scale 2: The Wechsler Scales
- Wechsler-Bellevue Intelligence Scale; developed to correct flaws in Stanford-Binet Scale.
- Test was designed for adults and items were groups into subtests not according to age level.
- Used a deviation IQ concept; intelligence is normally distributed, compare with same-age peers.
- 1955—Wechsler-Adult Intelligence Scale (WAIS); revised version 1981 (WAIS-R).
- 1997—(WAIS-III); and most recent version 2008 (WAIS-IV)
- Inclusion of reversal items in the subtests introduced first in WAIS-III
o Two examinee's both begin with the same base items then based on performance subsequent items are presented in reverse sequence until a perfect score on two consecutive items is obtained.
- WAIS-IV—provided Index scores in addition to the Full Scale IQ Scores.
Obtaining the Full Scale IQ Score and Index Scores + Standardization:
- Raw scores converted to standardized scores for a given age group.
- Full IQ Score and Index score—adding scale scores of each subtest and converting sums to IQ equivalents.
Reliability and Validity
- Scores from previous WAIS-III and WISC-IV are strongly correlated with WAIS-IV scores (good).
- Over relying on global IQ scores can thus be misleading (Full Scale IQ)
The Wechsler Intelligence Scale for Children (WISC-IV)—Description and Standardization
- 1949—WIC; multiple revisions since then and the latest version WISC-IV was published in 2003.
- Used to test children age 6-16 years old; has 10 core and 5 sub-tests. A reduced version of WAIS.
- Individual subtests define 4 major indices and make up the Full Scale IQ (*see pg. 212).
o Verbal Comprehension Index (VCI), Perceptual Reasoning Index (PCI), Working Memory Index (WCI), The Processing Speed Index (PSI)
The Wechsler Preschool and Primary Scale of Intelligence (WPPSI-III)
- 1967—WPPSCI developed; a revised version since then and the latest WPPSI-III in 2002.
- Similar to the WISC-IV but targeted towards youth; so children below the age of 6.
- Only 3 indices—Full Scale IQ, Verbal IQ and Performance IQ; addition of PSI for age 4+; but also has several subset scales specific for children only.
Clinical Use of Intelligence Tests
Estimating General Intelligence Level
- Determining the person's g level—what is the patient's intellectual potential?
- Intellectual ability level can also assist with helping individuals recover cognitive abilities following head trauma, injury.
- IQ scores need to be interpreted and placed in an appropriate context.
Prediction of Academic Success and Appraisal of Style
- Intelligent tests should predict academic success in school.
- Intelligence tests allow us to observe patient at work (observations; help with interpretation).
- Some clinicians made diagnosis of mental disorders from intelligence tests (intertest scatter) but this is not at all reliable.
Final Observations and Conclusions—IQ is an Abstraction
- Look at IQ as “present functioning” not innate potential; it is an abstraction that allows us to predict specific behaviors.
- Most believe that there is a “true IQ” and intelligence tests assess these.
Final Observations and Conclusions—Generality Versus Specificity of Measurement
- Intelligence tests can provide broad general index of intellectual functioning across a range of situations. Can thus be used to compare similar individuals in same situations.