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… 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

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

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

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?

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

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…”

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.

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)

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

63.2 – discuss the evidence for 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.