Lecture Outline What is Development? Themes/Issues in Developmental Psychology

1. Lecture Outline • What is Development? • Themes/Issues in Developmental Psychology • Developmental Systems Theories

2. What is development? • Development refers to systematic, successive changes in the individual that occur over time from conception to death

3. Themes/Issues in Developmental Psychology • Is development due to nature (genes) or nurture (environment)? • Genetic and environmental factors influence all aspects of development • But still debate about the role of genetic and environmental factors in development • Should we be asking “How much?” or “How?”

8. Family Studies • Compare individuals with different degrees of genetic relatedness on a particular characteristic • Exs: twin studies, adoption studies

9. Twin Studies: • Compare identical twins to fraternal twins on a particular characteristic • Identical twins share 100% of their genes and fraternal twins share 50% of their genes • If identical twins are more similar than fraternal twins with respect to a particular characteristic, assumed that genes influence the characteristic

10. Concordance Rate: • The percentage of instances in which both twins show a trait when it is present in one twin • Used for categorical traits (present/absent) • Ex: schizophrenia, depression • If concordance rate is higher for identical than for fraternal twins, assumed that genetic factors influence the trait

11. Heritability Coefficient: • Estimates the extent to which individual differences in characteristics are due to genetic influence • Used for continuous characteristics • Ex: IQ, personality traits • Ranges from 0 to 1 • 1 – H = environmental influence

13. Important Points (Heritability Coefficients): • Apply to populations (groups), not individuals • Correct: 50% of the variation in IQ in a specific population is due to genetic factors • Incorrect: 50% of my IQ is due to my genes

14. Heritability coefficients are specific to a particular population and cannot be generalized • G + E = 1 • The more environments vary, the lower heritability estimates will be (and vice versa) • Ex: Heritability of IQ is higher in middle- and upper-class samples than in low-income samples • Less variability in the environments of middle- and upper-class children

15. Characteristics that are heritable can also be modified by the environment • Ex: Height is highly heritable, but average height has increased across successive generations due largely to environmental factors such as improved nutrition

17. Criticisms of (Traditional) Behavior Genetics • Does not explain how specific genetic and specific environmental factors affect development • Assumes that effects of genes and environment are independent and additive—i.e., that genetic and environmental influences can be separated • Does not account for interactions between genetic and environmental factors very well • Does not account for correlations between genes and environment very well

18. Children’s genes are correlated with the environments they experience • Some researchers (e.g., Rowe, 1994; Scarr & McCartney, 1983) argue that genetic factors drive development because they influence the environments that children experience or select for themselves

19. Developmental systems theorists argue • Genetic and environmental factors are fused in development • There are bidirectional influences between genetic/biological factors within the individual and all levels of the environment

20. Alternative Perspectives • Genes may affect the environments that children experience and select for themselves • But the expression of genes is also affected by the type of environment(s) available to a child • Environmental influences can affect genetic activity

21. Developmental continuity and discontinuity

22. Continuous (Quantitative) • Gradual, small, steady increases in skills/abilities

23. Discontinuous (Qualitative) • Relatively abrupt changes (stages) that involve a re-organization of skills/abilities