IQ TEST AND INTELLIGENCE

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

TYPES OF RELIABILITYType Description Test-Retest

Alternate Form

Internal

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

Type Description Face

Content

Concurrent

Predictive

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”? 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

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.

THEORIES OF INTELLIGENCE Spearman – g factor & s factor Cattell – crystallized and fluid intelligence Gardner – 8 separate “intelligences” Sternberg – triarchic theory of intelligence

Contextual Experiential Componential

DOES “G” EXIST? One of the longest-running debates in

psychology: Global intelligence, a general ability Specific abilities …..More a matter of emphasis

“Intelligence is what intelligence tests measure” Edward Boring

INVENTION OF IQ TESTSSir 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

Theodore Simon Lewis Terman: 1916Stanford IQ

Divided child’s mental age by the child’s chronological age to yield an Intelligence Quotient (IQ) (idea originally from William Stern, a German psychologist) All average children, regardless of age, would have an IQ of 100

BINET TEST COMES TO AMERICA Lewis Terman revised Binet’s test Devised norms for American kids Stanford- Binet Intelligence Scale: 1916 Been updated many times David Wechsler: Wechsler Adult Intelligence Scale (WAIS) (WISC) ---Probably the best IQ test for adults ---Different subscales (Verbal vs..

Performance)

“He had a WAIS IQ of …..”

INTELLIGENCE MEASURED Most popular and most frequently

administered are the Wechsler ScalesWechsler Adult Intelligence Scale (WAIS III)WAIS-R as a Neuropsychological

Instrument (WAIS-RNI)Wechsler Intelligence Scale of Children

(WISC-IV)Wechsler Primary and Preschool Scale-

Revised (WPPSI-R) Stanford-Binet V Kaufman Assessment Battery Woodcock-Johnson Psychoeducational

Battery III

WECHSLER SYSTEM Verbal subtests

Information Similarities Arithmetic Vocabulary Comprehension Digit span 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)90-110 average range< 70 is in mentally deficient range> 130 is in the very superior range

Individual tests have a mean score of 10; SD of 3

All form the basis for subtle observations about relative strengths and limitations

Observe patterns of scores Interpreted in the context of other test

results and variety of biopsychosocial factors

CORRELATIONS IN IQHENDERSON, 1982

Relationship r # of pairs

Individual with self: .87 456 MZ twins .86 1417

MZ apart .75 DZ twins .62 1329 Siblings .41 5350

Sibs apart .21 203

IQ TESTS CONT.

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

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 behaviour, 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

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