Genetics, Environment, and Behavior

1
Genetics, Environment, and Behavior

• How do they interact?

2
Identical twins reared apart

• Elyse Schein and Paula Bernstein

Photo Elena Siebert, 2007
3
Methods of behavior genetics

• Twin studies
• Adoption studies
• Temperament studies
• Heritability Percentage of variability that can
  be connected to genes.
• Molecular genetics

4
Variation

• Genotypes vary, except in identical twins
• Environments vary, even for identical twins
• And this may start at the twinning point.
• Consequently, phenotypes vary We are different
  from one another
• Nonetheless, we are far more similar than we are
  different from one another.

5
Genetics

• Chromosome pairs and meiosis
• Protein synthesis recipes
• Expression of alleles
• Homozygous alleles
• Heterozygous alleles
• Dominant alleles
• Recessive alleles
• Polygenic control
• No genes for behavior

6
Evolutionary psychology

• An old idea is currently popular again
• Emphasis is on natural selection
• Or is it artificial selection?
• Example of mate selection
• Are all men potential rapists?

7
Criticism of evolutionary psychology

• Backward reasoning an effect looking for a cause
• An example of post hoc reasoning.
• Selective use of research results Infidelity is
  overestimated.
• Casual sex has far lower fertility than committed
  sex.
• The theory plays on gender stereotypes

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More criticism

• Other causes socialization pressure, family life
• Female sexuality is highly variable, especially
  across time and situations
• Mate preferences are culture-related (Eagly
  Wood, 1999)
• Male (and female) relatives of females might
  protect or take revengeand women can protect
  themselves, as Martha McGaughey (2008) points out
  in The Caveman Mystique.

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And a new, killer study (Farthing, 2005)

• Men are more impressed by other men who take
  risks.
• Women are not.
• Women prefer altruistic men.
• But, Farthing speculates, perhaps the higher
  status of risk-taking men among other men makes
  them more attractive to women.

10
Gender influences

• Sex-linked traits
• Gene on sex chromosomes
• Sex-influenced traits
• Interaction of genetics and environment
• Hormones are key variables

11
Molecular genetics

• What are the specific genes that influence
  behavior?
• For example, what genes contribute to Bipolar
  Disorder?
• Risk prediction and the genetic test for
  Huntingtons disease Does technology make
  decisions easier?

12
Molecular genetics Genetic abnormalities

• Mutations Hemophilia
• Aberrations Cri-du-chat (5p-) syndrome
• Interaction of genetics and environment
• Genetic disorders
• Down syndrome Genetic but not hereditary
• Huntingtons disease Genetic and hereditary, no
  interaction with environment
• PKU Genetic and hereditary, interaction with
  environment

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Molecular genetics of behavior

• Animal breeding Artificial selection
• Tame foxes (Trut, 1999)
• Eugenics
• Family studies Concordance of bipolar disorder
• Twin studies
• Do you have a missing twin?
• Adoption studies
• An example Schizophrenia

14
Environmental influences

• Prenatal environment
• Monochorionic and dichorionic twins
• Enriched vs. impoverished environments
• Growth vs. pruning
• The second language-learning hypothesis is now
  being questioned
• Peer influence Food choice, accent, smoking
• Time spent
• Access to peers

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More environmental influences

• Parents
• Preferences
• Personality
• Culture
• Norms
• Collective vs. individual emphasis
• Gender
• Aggression, social power, and social connection

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Sociobiology

• Parental investment
• The incest taboo
• Altruism
• Kin selection
• Reciprocal altruism

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Ethnocentrism

• Altruism in the Inuit
• Kin selection
• Familiarity

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Critical thinking about ethocentricity

• How is the question framed? Does it lead us down
  one path of thinking?
• What are our predispositions and assumptions ?
  What pattern of thinking would make us look good
  or feel better about ourselves?
• Avoid fallacious thinking The universality
  fallacy and the naturalistic fallacy

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What do we look for in a mate? (Buss, 1998)

• Men prefer, in order
• 1. Kindness, understanding
• 2. Intelligence
• 3. Physical attractiveness
• 4. Exciting personality
• 5. Good health
• 6. Adaptability
• 7. Creativity
• 8. Desire for children
• 9. College graduate
• 10. Good heredity

• Women prefer, in order
• 1. Kindness, understanding
• 2. Intelligence
• 3. Exciting personality
• 4. Good health
• 5. Adaptability
• 6. Physical attractiveness
• 7. Creativity
• 8. Good earning capacity
• 9. College graduate
• 10. Desire for children