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Nature vs. Nurture and Intelligence Early pioneers of intelligence…

63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Nature vs. Nurture and Intelligence Early pioneers of intelligence… Maintained the nature view of intelligence Today’s nature theorists…

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Nature vs. Nurture and Intelligence Early pioneers of intelligence…

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  1. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Nature vs. Nurture and Intelligence • Early pioneers of intelligence… • Maintained the natureview of intelligence • Today’s nature theorists… • Assert that a child’s intelligence CANNOT be changed; genetic destiny • Many argue that this downplays the value of special education programs for underprivileged groups

  2. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Nature vs. Nurture and Intelligence • Today’s nurture theorists… • Assert that traits with a strong genetic component are not necessarily unchangeable • Argue that even MORE funds be allocated for remedial programs, especially in lower-income areas

  3. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. • Family Studies • Can determine only whether genetic influence on a trait is plausible • Twin Studies • The average correlation for identical twins is +0.86 • The average correlation for fraternal twins is +0.60 • Adoption Studies • Studies indicate that there is more than chance similarity between adopted children and their biological parents

  4. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. • Heritability: the proportion of variation among individuals that we can attribute to genes. The heritability of a trait may vary, depending on the range of populations and environments studied. • Heritability Ratio • Can be estimated for any trait • 90% for height • 85% for weight • Intelligence?

  5. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Heritability • Heritability estimates for intelligence vary considerably • High Estimate: 80% • 20% of the variation in intelligence is attributable to environmental factors • Low Estimate: 40% • 60% of the variation in intelligence is attributable to environmental factors

  6. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Heritability • Limitations of heritability estimates • Heritability is a group statistic; CANNOT be meaningfully applied to individuals • A trait’s heritability may vary from one group to another • “There really is no single fixed value that represents any true, constant value for the heritability of IQ or anything else…”

  7. 63.1 – Discuss the evidence for a genetic influence on intelligence and explain what is meant by heritability. Genetic Influences • Studies of twins, family members, and adopted children support the idea that there is a significant genetic contribution to intelligence.

  8. 63.2 – discuss the evidence for environmental influences on intelligence. • Twin Studies • The average correlation for identical twins raised together is +0.86 • The average correlation for identical twins raised apart is +0.72 • Adoption Studies • There is some resemblance between adoptive parents and their children • Siblings reared together are more similar in IQ than siblings reared apart (0.48, as opposed to 0.23)

  9. 63.2 – discuss the evidence for environmental influences on intelligence. Sandra Scarr (1991) • Reaction-Range Model • Heredity sets certain limits on intelligence and environmental factors determine where individuals fall within these limits • Genetic makeup places an upper limit on a person’s IQ • Cannot be exceeded; even when environment is ideal • Genetic makeup places a lower limit on a person’s IQ except in extreme cases

  10. 63.2 – discuss the evidence for environmental influences on intelligence. Environmental Influences on Intelligence • Malnutrition, sensory deprivation, and social isolation can retard normal brain development. • Schooling is an experience that pays dividends: increased schooling correlates with higher intelligence scores. • having a “growth mindset” results in a focus on learning and growing.

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