Intelligence and Intelligence Intelligence and Intelligence TestingTesting

Definitions of intelligence:Definitions of intelligence:

Terman: the ability to carry on abstract Terman: the ability to carry on abstract thinking.thinking.

Wechsler: The capacity of an individual to Wechsler: The capacity of an individual to act purposefully and think rationally and to act purposefully and think rationally and to deal effectively with the environment.deal effectively with the environment.

Definitions continuedDefinitions continued

Burt: innate general cognitive abilityBurt: innate general cognitive ability

Robinson & Robinson: All of the Robinson & Robinson: All of the knowledge a person has acquired.knowledge a person has acquired.

Piaget: a basic life function that helps the Piaget: a basic life function that helps the organism (person) to adapt to its organism (person) to adapt to its environment.environment.

Major QuestionsMajor Questions

Is intelligence a general characteristic?Is intelligence a general characteristic?

Intelligence conceptualized as products Intelligence conceptualized as products that arise from activity or the processes that arise from activity or the processes people use to solve problems?people use to solve problems?

How stable is intelligence?How stable is intelligence?

What do IQ scores predict?What do IQ scores predict?

What factors influence IQ scores?What factors influence IQ scores?

Origins of Intelligence TestingOrigins of Intelligence Testing

Alfred Alfred BinetBinet (psychologist) and Theodore (psychologist) and Theodore SimonSimon (physician) in France, 1904 (physician) in France, 1904– Requested to identify children who Requested to identify children who

needed special instructionneeded special instruction– Devised a test that examined a Devised a test that examined a

variety of cognitive tasks (e.g., carry variety of cognitive tasks (e.g., carry out multiple instructions, identify the out multiple instructions, identify the missing part of a picture, remember missing part of a picture, remember a string of random digits, etc.)a string of random digits, etc.)

Post Binet & SimonPost Binet & Simon

Lewis Terman (at Stanford) modified the Lewis Terman (at Stanford) modified the Binet-Simon scales to create the Binet-Simon scales to create the Stanford-Stanford-Binet Intelligence ScaleBinet Intelligence Scale

David Wechsler developed tests both for David Wechsler developed tests both for adults and for children (e.g., adults and for children (e.g., WISCWISC…)…)

Raven’s Progressive MatricesRaven’s Progressive Matrices were were designed to assess reasoning about designed to assess reasoning about perceptual patterns…perceptual patterns…

Calculating IQCalculating IQ

William Stern (Germany) developed William Stern (Germany) developed concept of IQ, in which concept of IQ, in which IQ=(MA/CA)IQ=(MA/CA)**100100

Now use Now use “deviation IQ”“deviation IQ” based on the based on the normal distribution…normal distribution…

Tests evaluate verbal and nonverbal Tests evaluate verbal and nonverbal abilities.abilities.

Achievement TestsAchievement Tests

IQ Test: underlying competenceIQ Test: underlying competence

Achievement Test: performanceAchievement Test: performance

Is this distinction realistic?Is this distinction realistic?

Is IQ a stable attribute?Is IQ a stable attribute?

Infant IQ predicting later IQ?Infant IQ predicting later IQ?

Preschool IQ predicting later IQ?Preschool IQ predicting later IQ?

Validity of IQ test?Validity of IQ test?– IQ and grades in schoolIQ and grades in school– IQ and amount of schoolingIQ and amount of schooling

Limitations of IQ testsLimitations of IQ tests

Cannot tell us about a fixed underlying Cannot tell us about a fixed underlying intellectual capacityintellectual capacity

Do not measure other skills important to Do not measure other skills important to adaptive living.adaptive living.

Terman study (1922)Terman study (1922)

Stereotypes of the “gifted child”?Stereotypes of the “gifted child”?

1500 California school children with IQ’s 1500 California school children with IQ’s 140 or higher.140 or higher.

How do we explain IQ differences?How do we explain IQ differences?

Twin studies and adoption studies.Twin studies and adoption studies.

Bouchard & McGue (1981).Bouchard & McGue (1981).– Identical twins reared togetherIdentical twins reared together .85.85– Identical twins reared apartIdentical twins reared apart .67.67– Fraternal twins reared togetherFraternal twins reared together .58.58– Siblings Siblings .24.24

What does this data suggest?What does this data suggest?

Adoption StudiesAdoption Studies

Texas Adoptiin Study (Loehlin et al.,1994)Texas Adoptiin Study (Loehlin et al.,1994)Minnesota Transracial Adoption study Minnesota Transracial Adoption study (Scarr et al., 1993)(Scarr et al., 1993)

TexasTexas MinnesotaMinnesota

biological motherbiological mother.44.44 .29.29adoptive motheradoptive mother .03.03 .14.14adoptive fatheradoptive father .06.06 .08.08

Capron & Duyme, 1989Capron & Duyme, 1989

Adoptive parentAdoptive parent

HighHigh LowLow

BiologicalBiological HighHigh 119.60119.60 107.50107.50

ParentParent

LowLow 103.60103.60 92.4092.40

Environmental InfluencesEnvironmental Influences

National US study: n=50,000 children; SB National US study: n=50,000 children; SB IQ scoresIQ scores

Family characteristics associated with IQ?Family characteristics associated with IQ?– Family climateFamily climate– Number of children in the familyNumber of children in the family– Birth orderBirth order– Zajonc: intellectual climateZajonc: intellectual climate

Interaction of heredity and Interaction of heredity and environmentenvironment

Reaction rangeReaction range

Normal range of environmentsNormal range of environments