IDAP L8-10

Defining Intelligence

• Intelligence is a psychological trait that is relatively stable over time and possesses individual differences in specific intellectual abilities.
• It is a general mental capacity that is possessed by everyone, but not at the same level.

Intelligence Tests

• No single test of intelligence is comprehensive, and no test is a pure measure of intelligence.
• Good intelligence tests should have three key features:
  • Variety of tasks to assess overall intelligence and specific strengths.
  • Standardization of administration to allow for comparison between people.
  • Norm-referencing to compare test results to a representative sample.

Binet-Simon Intelligence Test

• Developed by Alfred Binet and Theodore Simon in 1904.
• Original test consisted of 30 short everyday tasks with increasing difficulties.
• Test was designed to match developmental ages (3-10 years, later extended to 12-15) and compare a child's mental age to their chronological age.

Stanford-Binet Intelligence Test

• Revised Binet-Simon test by Lewis Terman to suit US children from 4-14 years old.
• Levels of difficulty correspond to age groups.
• Results were standardized by testing over 1,000 children to identify typical performance.

Intelligence Quotient (IQ)

• Developed by William Stern in 1912.
• Key factor is the way children's mental ages vary in proportion to their chronological ages.
• Average intelligence score is set at 100, regardless of age.

Army Alpha and Beta Tests

• Developed by the APA president during WWI to quickly screen army recruits for intellectual ability.
• Tests were cheap, quick, and designed to be administered to groups.
• Army Alpha test was for literate groups, while Army Beta test was for illiterate and non-English speaking groups.

General Intelligence Theory

• Proposed by Spearman in 1904.
• Suggests that there is a single intelligence that underlies performance on all different ability tests.
• There is a positive manifold, meaning results on different tests are positively correlated.

Two-Factor Theory

• Proposed by Spearman.
• Suggests that there are two factors involved in intelligence: specific abilities (S) and general intelligence (G).
• Performance on a specific test is influenced by both S and G.

Wechsler Test

• Involves one-to-one administration of several subtests with tasks of varying difficulties.
• Individual test scores and full-scale IQ, verbal IQ, and performance IQ are provided.
• Test scores are compared normatively to others, with a representative sample including people from various backgrounds.

Raven's Progressive Matrices

• Developed by John Raven in 1938.
• Assumes that g is an abstract ability to see relationships between objects and information.
• Mostly assesses non-verbal problem-solving and abstract reasoning.

Evidence for G

• Studies have shown a positive correlation between performance on different tests, as predicted by Spearman's g.

Multiple Intelligence Theories

• 7 Primary Abilities Theory: proposes that there are 7 independent factors that people possess to varying degrees.
• Theory of Fluid and Crystallised Intelligence: proposes that g is composed of two related components: fluid intelligence and crystallised intelligence.
• Hierarchical Models of Intelligence: proposes that there are three levels of intelligence: specific levels of intelligence, broad factors, and general intelligence.

Predictive Validity of Intelligence

• Education: correlation between IQ and other indicators of success in school is around 0.50.
• Employment: correlation between IQ scores and job performance is around 0.50.

Stability of Intelligence Measures

• Scottish Mental Survey (1932) found a correlation of 0.50-0.66 between scores at different ages.

Flynn Effect

• Describes the increase in intelligence scores over time.
• Average increase of 14 IQ points during the time period.

Critiques of Intelligence Testing

• Intelligence is too complex to be reduced to a number.
• Tests are not a fair or valid way to measure abilities.
• IQ-achievement discrepancy involves classifying learning disabilities through comparing achievement to IQ scores.

Eugenics

• Theory that the human race can be improved by selective breeding.
• Based on an incorrect understanding of genetics.
• Supporters generally encourage one of two "solutions": positive eugenics or negative eugenics.

History of Eugenics Policies

• Forced sterilisation laws were implemented in several countries, including the USA.
• Nazi Germany's eugenics policies led to the sterilisation of over 20,000 people and the killing of millions of people during the Holocaust.

Heritability Estimates of Intelligence

• Eysenck's theory: 69%
• Carroll's theory: 40%
• APA taskforce on intelligence: 40-80%