Intelligence

Intelligence: The Role of Heredity and Environment in IQ

Dr. Angie Makri

Page 1

  • Introduction to the topic of intelligence and its measurement.

Page 2: Today’s Questions

  • What is intelligence and how is it measured?

  • Is intelligence a single construct?

  • Does intelligence depend on heredity or the environment?

  • Can intelligence change over the lifespan?

Page 3: Background on IQ

  • IQ (Intelligence Quotient): Index of an individual's intelligence score.

  • Types of IQ Tests:

    • Verbal tests

    • Non-verbal tests

  • Advantages of Non-Verbal Tests:

    • Eliminate language issues, verbal abilities, and cultural differences.

Page 4: Key Figures and History of Intelligence

  • Francis Galton:

    • Proposed intelligence is a product of natural selection; possibly genetically determined.

    • Saw potential in evolution for planned human betterment.

  • Binet & Simon:

    • Developed the first IQ tests for educational measurement.

Page 5: Lewis Terman and Maud Merrill

  • Stanford-Binet Scale: Developed by Terman.

  • Conducted a longitudinal study on "gifted" children, found high intelligence in stable individuals rather than misfits.

Page 6: Military Applications and Eugenics

  • Lewis Terman’s Military Tests: Alpha and Beta tests assigned soldiers to suitable tasks during WWI.

  • Eugenics Advocacy: Promoted selective breeding for desirable traits.

Page 7: Cyril Burt's Controversies

  • Advised UK government on aptitude tests for grammar school placement.

  • Suggested intelligence tied to social class and hereditary levels, but faced allegations of data fabrication.

Page 8: Cultural Bias in Intelligence Testing

  • Intelligence tests often favor affluent groups, leading to discrimination against marginalized groups.

Page 9: Raven's Progressive Matrices

  • Visual reasoning test: Identify the missing shape in a matrix.

Page 11: Recent IQ Tests

  • WISC (Wechsler Intelligence Scale for Children)

  • WASI (Wechsler Adult Scale of Intelligence)

    • Incorporate verbal and non-verbal tests.

    • Target both crystallized and fluid intelligence.

Page 12: Basic Concepts

  • Genotype: Genetic makeup of an organism.

  • Phenotype: Observable traits influenced by genotype and environment.

  • Only phenotype can be measured; many factors affect performance.

  • Assess genetic relatedness for understanding genetic concepts.

Page 13: Normal Distribution of IQ

  • Visualization of IQ scores along a normal distribution curve.

Page 14: Atheoretical Definition of Intelligence

  • IQ tests are the measure of intelligence, lacking a comprehensive theoretical basis.

  • High correlation between IQ tests and other performance measures (e.g. academic performance, reasoning).

Page 15: Is Intelligence a Single Construct?

  • Generalized Intelligence:

    • Influences all cognitive functioning, shown through performance correlations.

    • Tests include Stanford-Binet and Raven’s matrices.

Page 16: Is Intelligence a Multiple Construct?

  • Multiple Constructs of Intelligence (Cattell, 1987):

    • Fluid Intelligence (FI): Unaffected by environment, stable over time.

    • Crystallized Intelligence (CI): Learned knowledge, responsive to education.

    • Interaction between FI and CI noted.

Page 18: Heredity vs. Environment in Intelligence

  • Twin studies allow analysis of genetic vs. environmental influences on intelligence.

  • Difficulty arises in separating these factors distinctly.

Page 19: Bouchard & McGue (1981) Findings

  • Study Data:

    • Different pairings of twins and correlation of IQ scores presented.

    • Identical twins showed highest correlation, with adopted children showing lower correlations.

Page 20: Environmental Factors

  • Factors influencing IQ during fetal development and family environment.

  • Enriched environments correlate positively with IQ outcomes.

Page 21: Elardo et al (1975) Family Environment Quality

  • Key elements of nurturing family environments that enhance child development.

Page 22: IQ Correlation with Family Environment

  • Strong correlation of family environment quality with children's IQ at various ages.

Page 23: Considerations on Inheritance and Environment

  • Interaction of intelligent children with intelligent parents enhances the enriched environment.

  • The transactional process complicates the distinction between genetic and environmental influence on intelligence.

Page 24: Popular Conceptions of IQ

  • Claims regarding intelligence enhancement:

    • Vitamins, cognitive training, and birth order effects.

    • Only limited support for these statements in research.

Page 25: Diet and Nutrition Study by Benton and Roberts (1988)

  • Study comparing IQ changes in children through vitamin supplements versus placebos.

Page 26: Nutritional Impacts on IQ

  • Positive IQ score increases noted primarily in children with poor nutrition, minimal effects in well-nourished children.

Page 27: Effectiveness of Cognitive Training

  • Owen et al. (2010) study indicating training improvements do not transfer to general cognitive tasks.

Page 28: Birth Order Implications on Intelligence

  • Discussion on why first-born children may display higher IQ compared to younger siblings.

Page 29: Confluence Model (Zajonc, 1976)

  • First-born interactions with adults are more intellectually stimulating than interactions with siblings.

Page 30: Dilution Model (Blake, 1981)

  • As family size increases, individual attention from parents decreases, leading to less stimulating environments for later-born children.

Page 31: The Flynn Effect

  • Increase in IQ scores over generations; linked to educational improvements, better nutrition, and supportive parenting.

Page 32: Conclusions

  • Studies indicate intelligence is highly heritable, with factors spanning across lifespan.

  • Genetic influences on intelligence are complex and intertwined with environmental factors.

  • Recognition of environmental impacts is crucial in avoiding biases in IQ assessments.