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  1. 1. Genetics, Environment, and Behavior How do they interact?
  2. 2. Identical twins reared apart <ul><li>Elyse Schein and Paula Bernstein </li></ul>Photo: Elena Siebert, 2007
  3. 3. Methods of behavior genetics <ul><li>Twin studies </li></ul><ul><li>Adoption studies </li></ul><ul><li>Temperament studies </li></ul><ul><li>Heritability: Percentage of variability that can be connected to genes. </li></ul><ul><li>Molecular genetics </li></ul>
  4. 4. Variation <ul><li>Genotypes vary, except in identical twins </li></ul><ul><li>Environments vary, even for identical twins </li></ul><ul><ul><li>And this may start at the twinning point. </li></ul></ul><ul><li>Consequently, phenotypes vary: We are different from one another </li></ul><ul><li>Nonetheless, we are far more similar than we are different from one another. </li></ul>
  5. 5. Genetics <ul><li>Chromosome pairs and meiosis </li></ul><ul><li>Protein synthesis recipes </li></ul><ul><li>Expression of alleles </li></ul><ul><ul><li>Homozygous alleles </li></ul></ul><ul><ul><li>Heterozygous alleles </li></ul></ul><ul><ul><ul><li>Dominant alleles </li></ul></ul></ul><ul><ul><ul><li>Recessive alleles </li></ul></ul></ul><ul><li>Polygenic control </li></ul><ul><li>No genes for behavior </li></ul>
  6. 6. Evolutionary psychology <ul><li>An old idea is currently popular again </li></ul><ul><li>Emphasis is on natural selection </li></ul><ul><ul><li>Or is it artificial selection? </li></ul></ul><ul><ul><li>Example of mate selection </li></ul></ul><ul><ul><li>Are all men potential rapists? </li></ul></ul>
  7. 7. Criticism of evolutionary psychology: <ul><li>Backward reasoning: an effect looking for a cause </li></ul><ul><ul><li>An example of post hoc reasoning. </li></ul></ul><ul><li>Selective use of research results: Infidelity is overestimated. </li></ul><ul><li>Casual sex has far lower fertility than committed sex. </li></ul><ul><li>The theory plays on gender stereotypes </li></ul>
  8. 8. More criticism <ul><li>Other causes: socialization pressure, family life </li></ul><ul><li>Female sexuality is highly variable, especially across time and situations </li></ul><ul><li>Mate preferences are culture-related (Eagly & Wood, 1999) </li></ul><ul><li>Male (and female) relatives of females might protect or take revenge—and women can protect themselves, as Martha McGaughey (2008) points out in The Caveman Mystique . </li></ul>
  9. 9. And a new, killer study (Farthing, 2005): <ul><li>Men are more impressed by other men who take risks. </li></ul><ul><li>Women are not. </li></ul><ul><li>Women prefer altruistic men. </li></ul><ul><li>But, Farthing speculates, perhaps the higher status of risk-taking men among other men makes them more attractive to women. </li></ul>
  10. 10. Gender influences <ul><li>Sex-linked traits </li></ul><ul><ul><li>Gene on sex chromosomes </li></ul></ul><ul><li>Sex-influenced traits </li></ul><ul><ul><li>Interaction of genetics and environment </li></ul></ul><ul><ul><li>Hormones are key variables </li></ul></ul>
  11. 11. Molecular genetics <ul><li>What are the specific genes that influence behavior? </li></ul><ul><li>For example, what genes contribute to Bipolar Disorder? </li></ul><ul><li>Risk prediction and the genetic test for Huntington’s disease: Does technology make decisions easier? </li></ul>
  12. 12. Molecular genetics: Genetic abnormalities <ul><li>Mutations: Hemophilia </li></ul><ul><li>Aberrations: Cri-du-chat (5p-) syndrome </li></ul><ul><ul><li>Interaction of genetics and environment </li></ul></ul><ul><li>Genetic disorders </li></ul><ul><ul><li>Down syndrome: Genetic but not hereditary </li></ul></ul><ul><ul><li>Huntington’s disease: Genetic and hereditary, no interaction with environment </li></ul></ul><ul><ul><li>PKU: Genetic and hereditary, interaction with environment </li></ul></ul>
  13. 13. Molecular genetics of behavior <ul><li>Animal breeding: Artificial selection </li></ul><ul><ul><li>Tame foxes (Trut, 1999) </li></ul></ul><ul><li>Eugenics </li></ul><ul><li>Family studies: Concordance of bipolar disorder </li></ul><ul><li>Twin studies </li></ul><ul><ul><li>Do you have a missing twin? </li></ul></ul><ul><li>Adoption studies </li></ul><ul><li>An example: Schizophrenia </li></ul>
  14. 14. Environmental influences <ul><li>Prenatal environment </li></ul><ul><ul><li>Monochorionic and dichorionic twins </li></ul></ul><ul><li>Enriched vs. impoverished environments </li></ul><ul><ul><li>Growth vs. pruning </li></ul></ul><ul><ul><li>The second language-learning hypothesis is now being questioned </li></ul></ul><ul><li>Peer influence: Food choice, accent, smoking </li></ul><ul><ul><li>Time spent </li></ul></ul><ul><ul><li>Access to peers </li></ul></ul>
  15. 15. More environmental influences <ul><li>Parents </li></ul><ul><ul><li>Preferences </li></ul></ul><ul><ul><li>Personality </li></ul></ul><ul><li>Culture </li></ul><ul><ul><li>Norms </li></ul></ul><ul><ul><li>Collective vs. individual emphasis </li></ul></ul><ul><li>Gender </li></ul><ul><ul><li>Aggression, social power, and social connection </li></ul></ul>
  16. 16. Sociobiology <ul><li>Parental investment </li></ul><ul><li>The incest taboo </li></ul><ul><li>Altruism </li></ul><ul><ul><li>Kin selection </li></ul></ul><ul><ul><li>Reciprocal altruism </li></ul></ul>
  17. 17. Ethnocentrism <ul><li>Altruism in the Inuit </li></ul><ul><li>Kin selection </li></ul><ul><li>Familiarity </li></ul>
  18. 18. Critical thinking about ethocentricity <ul><li>How is the question framed? Does it lead us down one path of thinking? </li></ul><ul><li>What are our predispositions and assumptions ? What pattern of thinking would make us look good or feel better about ourselves? </li></ul><ul><li>Avoid fallacious thinking: The universality fallacy and the naturalistic fallacy </li></ul>
  19. 19. What do we look for in a mate? (Buss, 1998) <ul><li>Men prefer, in order: </li></ul><ul><ul><li>1. Kindness, understanding </li></ul></ul><ul><ul><li>2. Intelligence </li></ul></ul><ul><ul><li>3. Physical attractiveness* </li></ul></ul><ul><ul><li>4. Exciting personality </li></ul></ul><ul><ul><li>5. Good health </li></ul></ul><ul><ul><li>6. Adaptability </li></ul></ul><ul><ul><li>7. Creativity </li></ul></ul><ul><ul><li>8. Desire for children </li></ul></ul><ul><ul><li>9. College graduate </li></ul></ul><ul><ul><li>10. Good heredity </li></ul></ul><ul><li>Women prefer, in order: </li></ul><ul><ul><li>1. Kindness, understanding </li></ul></ul><ul><ul><li>2. Intelligence </li></ul></ul><ul><ul><li>3. Exciting personality </li></ul></ul><ul><ul><li>4. Good health </li></ul></ul><ul><ul><li>5. Adaptability </li></ul></ul><ul><ul><li>6. Physical attractiveness* </li></ul></ul><ul><ul><li>7. Creativity </li></ul></ul><ul><ul><li>8. Good earning capacity+ </li></ul></ul><ul><ul><li>9. College graduate </li></ul></ul><ul><ul><li>10. Desire for children </li></ul></ul>

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