MEASURING HOW WELL WE THINK

Intelligence

History of Intelligence Testing

1904: Alfred Binet created a test to identify mentally sub-normal children in education by measuring a child’s “mental age” This early tests was intended to identify children in

need of special training Mental age: mental ability typical of a child of that

chronological (actual) age Example: If you are told that “Billy” displays the

mental ability of a typical 7 year-old child, you would know his mental age is 7.

History continued…

1916: William Stern suggested an “intelligence quotient (IQ)” IQ = mental age/chronological age x 100 Example: If a child who is 10 years old has a mental

age of 12, the child’s IQ would be 120 Became the most commonly used IQ test worldwide

1939: David Weschler published the 1st IQ test for adults Two major innovations: test less verbally dependent &

introduced a new scoring technique based on normal distribution

What do modern IQ scores mean?

Normal distribution: a symmetrical bell shaped curve (p. 241) that represents the pattern in which many characteristics are dispersed in the population Most cases fall near the center of the distribution, and the

number of cases gradually decline as one moves either direction from the center

Most human traits, ranging from height to running speed to spatial ability to intelligence, follow a normal distribution

100=average (range 85 to 115) 15 point spread between ranges Levels: retarded—borderline—average—superior—gifted

ValidityValidity ReliabilityReliability

Ability to measure what it was designed to measure

Validity of IQ tests usually concentrate on their relationship to grades

Measurement consistency

Yields similar results on repetition

IQ scores should be viewed as estimates that are accurate +/-5 pts 2/3rd of the time

Intelligence Tests

Heredity versus Environment

Early pioneers believed that intelligence was inherited.

However, it has become clear that both heredity and environment influence intelligence.

Heritability of IQ is between 50 to 70 %

Heredity sets certain limits on our IQ and the environment determines where we fall within the limits. (Reaction Range) For most people the range is 20-25

pts

Evidence for Hereditary Influence

Twin Studies: Research on identical

and fraternal twins Share the same

environment—but also genetic factors

Identical twins: IQ has a very high correlation (.86), whereas fraternal twins (.60)

Identical twins reared apart display (.72) greater correlation than fraternal twins raised together

Adoption Studies: Comparison of score

for adopted children to biological parents

Measurable similarity

Evidence for Environmental Influence

Adoption Studies Adopted children show

some resemblance to their foster parents in IQ

Siblings reared together are more similar in IQ than those reared apart

Unrelated children who are raised in the same home show significant resemblance

Environmental Deprivation & Enrichment Environmental

deprivation due to isolation, poverty, neglect led to a predicted decline in IQ scores.

On the other hand, children in circumstances conducive to learning received benefits due to their environmental enrichment.

Generational Changes: Performance on IQ tests

has steadily increased over generations all over the world

WHY? Proposed explanations:

Better nutrition Technological Advances

Visual-spatial Cognitive skills

Better schools Smaller families Better educated parents Higher quality

parenting

The Flynn Effect Name given to the

increase in IQ test scores since the 1930s industrialization.

Changes have been attributed to environmental factors, after all the gene pool could not change that rapidly!

Cultural Differences

IQ scores of minorities (blacks, Native Americans, & Hispanics) in the U.S. are somewhat lower than that of whites

Disparity = 3 to 15 ptsWhy are the differences found?

Jensen argued it is due to heredity (extremely controversial) The Bell Curve (Herrenstein & Murray) contended that IQ is

the primary determinant of an individual’s success in life (implied what Jensen had said) p. 248

Socioeconomic disadvantage-children from lower social classes tend to have IQ’s 15 pts lower below average

Minorities are over-represented in the lower social classes--ethnic differences are most like social class differences.

Expanding our look @ intelligence

Sternberg’s Triarchic theory of human intelligence (mid 1980s) p. 251 He asserts that there are three factors that influence

successful intelligence: analytical intelligence (abstract reasoning, evaluation,

and judgment--typical of most IQ tests) creative intelligence (generating new ideas) practical intelligence (dealing with everyday problems)

New approaches

Howard Gardner’s Multiple Intelligences (1999) Believes traditional tests are too narrow in focus

(primarily verbal and mathematical) Concluded that humans exhibit eight independent

intelligences (p. 252) Difficult to test/prove his theory! Critics argue his use of the term “intelligence” is so

broad that it almost becomes meaningless.

Essay questions:

Describe how the representative heuristic influences your decision making strategies.

OR

Identify and describe four potential problems to IQ testing.