Intelligence & Intelligence Testing

Psychometrics is a very sophisticated field which uses applied mathematics to measure psychological and behavioral attributes and make predictions. Psychometricians construct, standardize, validate tests. Many people who criticize tests do not understand test theory or the mathematics behind test construction.

Types of Reliability TypeDescription Test-Retest Test-Retest Alternate Form Alternate Form Internal Internal Interrater or Interjudge Interrater or Interjudge Test produces similar results when given at two points in time. Two versions of the same test produce similar results. Different parts of the same test produce similar results. Two or more raters or judges who administer and score a test to an individual come to similar conclusions.

Types of Validity TypeDescription Face Face Content Content Concurrent Concurrent Predictive Predictive Construct Construct Test appears to measure what it is supposed to measure. Test assesses all important aspects of phenomenon. Test yields the same results as other measures of the same behavior, thoughts or feelings. Test predicts the behavior it is supposed to measure. Test measures what it is supposed to measure and not something else.

The Psychometric Approach How do you define “Intelligence”? How do you define “Intelligence”? Theorists use narrow, operational definitions Theorists use narrow, operational definitions Psychometricians do not claim that what is measured by an intelligence test is a good representation of “real-world” intelligence which is a broader concept Psychometricians do not claim that what is measured by an intelligence test is a good representation of “real-world” intelligence which is a broader concept Is it useful? Is it useful?

Wechsler’s definition Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally, and to deal effectively with the environment. Intelligence is the aggregate or global capacity of the individual to act purposefully, to think rationally, and to deal effectively with the environment.

Theories of Intelligence Spearman – g factor & s factor Spearman – g factor & s factor Cattell – crystallized and fluid intelligence Cattell – crystallized and fluid intelligence Gardner – 8 separate “intelligences” Gardner – 8 separate “intelligences” Sternberg – triarchic theory of intelligence Sternberg – triarchic theory of intelligence Contextual Contextual Experiential Experiential Componential Componential

Does “g” exist? One of the longest-running debates in psychology: One of the longest-running debates in psychology: global intelligence, a general ability global intelligence, a general ability specific abilities specific abilities …..More a matter of emphasis …..More a matter of emphasis “Intelligence is what intelligence tests measure” Edward Boring Edward Boring

Invention of IQ Tests Sir Francis Galton – published Hereditary Genius in 1869 – believed that “eminence” ran in families (genetic). - interested in studying “eminence” (and presumably intelligence – established a number of anthropometric laboratories. - measured eyesight, reaction time - related to his cousin Charles Darwin’s idea of “species’ fitness”

Invention of IQ Tests Alfred Binet: 1904 Mental Age Alfred Binet: 1904 Mental Age Theodore Simon Theodore Simon Lewis Terman:1916StanfordIQ Lewis Terman:1916StanfordIQ Divided child’s mental age by the Divided child’s mental age by the child’s chronological age to yield an child’s chronological age to yield an Intelligence Quotient (IQ) (idea originally from William Stern, a German psychologist) Intelligence Quotient (IQ) (idea originally from William Stern, a German psychologist) All average children, regardless of age, All average children, regardless of age, would have an IQ of 100 would have an IQ of 100

Binet Test comes to America Lewis Terman revised Binet’s test Lewis Terman revised Binet’s test Devised norms for American kids Devised norms for American kids Stanford- Binet Intelligence Scale: 1916 Stanford- Binet Intelligence Scale: 1916 Been updated many times Been updated many times David Wechsler: Wechsler Adult David Wechsler: Wechsler Adult Intelligence Scale (WAIS) (WISC) Intelligence Scale (WAIS) (WISC) ---Probably the best IQ test for adults ---Probably the best IQ test for adults ---Different subscales (Verbal vs.. Performance) ---Different subscales (Verbal vs.. Performance) “He had a WAIS IQ of …..”

Intelligence Measured Most popular and most frequently administered are the Wechsler Scales Most popular and most frequently administered are the Wechsler Scales Wechsler Adult Intelligence Scale (WAIS III) Wechsler Adult Intelligence Scale (WAIS III) WAIS-R as a Neuropsychological Instrument (WAIS- RNI) WAIS-R as a Neuropsychological Instrument (WAIS- RNI) Wechsler Intelligence Scale of Children (WISC-IV) Wechsler Intelligence Scale of Children (WISC-IV) Wechsler Primary and Preschool Scale-Revised (WPPSI-R) Wechsler Primary and Preschool Scale-Revised (WPPSI-R) Stanford-Binet V Stanford-Binet V Kaufman Assessment Battery Kaufman Assessment Battery Woodcock-Johnson Psychoeducational Battery III Woodcock-Johnson Psychoeducational Battery III

Wechsler system Verbal subtests Verbal subtests Information Information Similarities Similarities Arithmetic Arithmetic Vocabulary Vocabulary Comprehension Comprehension Digit span Digit span Letter-number sequencing Letter-number sequencing Performance subtests Picture arrangement Picture completion Block design Object assembly Matrix reasoning Digit symbol Symbol search

Wechsler System Mean score of 100; SD of 10 (15 in WISC and WPPSI) Mean score of 100; SD of 10 (15 in WISC and WPPSI) average range average range < 70 is in mentally deficient range < 70 is in mentally deficient range > 130 is in the very superior range > 130 is in the very superior range Individual tests have a mean score of 10; SD of 3 Individual tests have a mean score of 10; SD of 3 All form the basis for subtle observations about relative strengths and limitations All form the basis for subtle observations about relative strengths and limitations Observe patterns of scores Observe patterns of scores Interpreted in the context of other test results and variety of biopsychosocial factors Interpreted in the context of other test results and variety of biopsychosocial factors

Correlations in IQ Henderson, 1982 Relationshipr# of pairs Relationshipr# of pairs Individual with self: Individual with self: MZ twins MZ twins MZ apart.75 MZ apart.75 DZ twins DZ twins Siblings Siblings Sibs apart Sibs apart

IQ tests cont. Today’s tests based on norms rather than MA Today’s tests based on norms rather than MA Average is still set at 100 Average is still set at 100 SD usually 15 SD usually 15 2/3 score between 85 and 115 2/3 score between 85 and 115

New uses in America New uses in America Binet thought the tests could be useful for identifying children with learning problems--not to rank normal children Binet thought the tests could be useful for identifying children with learning problems--not to rank normal children In America, the original purpose was lost In America, the original purpose was lost The tests came to be used to categorize people in school and in the armed services according to their “natural ability”. The tests came to be used to categorize people in school and in the armed services according to their “natural ability”. Army alpha Army alpha Army beta (no English required) Army beta (no English required)

Intelligence testing Arguments for  reliable measure of individual differences – important for identifying need, allocating resources  reliable predictor of school achievement  identify discrepancies between expected and actual performance  allow for accountability, measurement of change and evaluation of program effectiveness

IQ tests Arguments against  measure samples of behavior, i.e. are not exhaustive  not theory driven – less true now  potential for cultural, SES bias  IQs change, reflecting both measurement error + actual performance differences  different tests yield different IQs  not a magical manifestation of a child’s innate potential