Intelligence and Intelligence Testing Definitions of intelligence: Terman: the ability to carry on abstract thinking. Wechsler: The capacity of an individual to act purposefully and think rationally and to deal effectively with the environment.

Definitions continued Burt: innate general cognitive ability Robinson & Robinson: All of the knowledge a person has acquired. Piaget: a basic life function that helps the organism (person) to adapt to its environment.

Major Questions Is intelligence a general characteristic? Intelligence conceptualized as products that arise from activity or the processes people use to solve problems? How stable is intelligence? What do IQ scores predict? What factors influence IQ scores?

Origins of Intelligence Testing Alfred Binet (psychologist) and Theodore Simon (physician) in France, 1904 –Requested to identify children who needed special instruction –Devised a test that examined a variety of cognitive tasks (e.g., carry out multiple instructions, identify the missing part of a picture, remember a string of random digits, etc.)

Post Binet & Simon Lewis Terman (at Stanford) modified the Binet-Simon scales to create the Stanford- Binet Intelligence Scale David Wechsler developed tests both for adults and for children (e.g., WISC…) Raven’s Progressive Matrices were designed to assess reasoning about perceptual patterns…

Calculating IQ William Stern (Germany) developed concept of IQ, in which IQ=(MA/CA) * 100 Now use “deviation IQ” based on the normal distribution… Tests evaluate verbal and nonverbal abilities.

Achievement Tests IQ Test: underlying competence Achievement Test: performance Is this distinction realistic?

Is IQ a stable attribute? Infant IQ predicting later IQ? Preschool IQ predicting later IQ? Validity of IQ test? –IQ and grades in school –IQ and amount of schooling

Limitations of IQ tests Cannot tell us about a fixed underlying intellectual capacity Do not measure other skills important to adaptive living.

Terman study (1922) Stereotypes of the “gifted child”? 1500 California school children with IQ’s 140 or higher.

How do we explain IQ differences? Twin studies and adoption studies. Bouchard & McGue (1981). –Identical twins reared together.85 –Identical twins reared apart.67 –Fraternal twins reared together.58 –Siblings.24 What does this data suggest?

Adoption Studies Texas Adoptiin Study (Loehlin et al.,1994) Minnesota Transracial Adoption study (Scarr et al., 1993) TexasMinnesota biological mother adoptive mother adoptive father.06.08

Capron & Duyme, 1989 Adoptive parent HighLow BiologicalHigh Parent Low

Environmental Influences National US study: n=50,000 children; SB IQ scores Family characteristics associated with IQ? –Family climate –Number of children in the family –Birth order –Zajonc: intellectual climate

Interaction of heredity and environment Reaction range Normal range of environments