Ch 6 Genetics and Personality

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Ch 6 Genetics and Personality

• 1. Introduction to Behavioral Genetics
• 2. Heritability of
• 3. on Personality

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Ch 6 Genetics and Personality

• Jim twins
• Identical
• Jim Springer Jim Lewis!
• Both 180 pounds, 6 feet tall
• First wives Linda!
• Second wives Betty!

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Ch 6 Genetics and Personality

• Jim twins
• Salem cigarettes
• Miller Lite
• Other
• How much do our genes contribute to
• Personality?
• Attitudes, preferences?

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Ch 6 Genetics and Personality

• Benefits
• 1.
• 2.
• 3.
• Issues
• 1. ? my genes, not me (psychopathy)
• 2. designer babies, weeding out unfit

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Ch 6 Genetics and Personality

• Human genome
• Sequencing the entire genome
• First draft
• (what does this mean?)

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Ch 6 Genetics and Personality

• Human genome
• Most genes are identical
• Yet,
• Brown/blue eyes
• Unique genes must play a role

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Ch 6 Genetics and Personality

• Danny DeVito 5 feet
• Shaquille ONeal 7 feet
• What causes such dramatic diffs?
• In fact

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Ch 6 Genetics and Personality

• Heritability
• Of a
• Height
• Aggressiveness
• Neuroticism
• Due to

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Ch 6 Genetics and Personality

• Size
• Conventionally
• E.g., 1 - .5 .5, suggesting .5 variance due to
  envt

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Ch 6 Genetics and Personality

• Misconceptions
• 1.
• Height is 90 heritable
• Michaels height is 90 heritable
• 2.
• Height in middle ages vs. today

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Ch 6 Genetics and Personality

• Heritabilities matter more for some stuff
• Mate characteristic preferences

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Ch 6 Genetics and Personality

• Behavior genetic methods
• 1. Selective breeding
• 2. Family studies
• 3. Twin studies
• 4. Adoption studies

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Ch 6 Genetics and Personality

• Selective breeding
• Pit bulls - aggression
• Labradors - sociability
• Chesapeake Bay retriever - to fetch
• Selective breeding
• Other methods for humans

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Ch 6 Genetics and Personality

• Family studies
• Trait should be more similar
• For more similar family members
• Parents
• Each parent with a child
• Siblings
• Grandparents
• Potential problem

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Ch 6 Genetics and Personality

• Twin studies
• Identical (100) more similar than fraternal
  (50)?
• But zygote divides into 2 individuals
• Must be same sex
• 2 separate sperm/egg combinations
• Gestated at same time

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Ch 6 Genetics and Personality

• Heritability
• Height
• r
• r
• Plugging in values
• Heritability
• Height 90 heritable
• Rest of 10 given to envt

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Ch 6 Genetics and Personality

• Adoption method
• Adoptive parents
• If envt has effect, children should be similar to
  adoptive parents
• Genetic parents
• If genes have effect, children should be similar
  to biological parents

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Ch 6 Genetics and Personality

• Heritability findings Personality traits
• 50 of E, N predicted by genes
• Typical finding
• Mz
• Dz
• Heritability

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Ch 6 Genetics and Personality

• Heritability findings Temperament-like variables
• 1.
• Spinath et al. (2002)
• Found heritability of movement
• 2. Other temperament
• Emotionality, sociability, persistence

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Ch 6 Genetics and Personality

• Heritability of personality, summary
• 1.
• Those that seem
• Those that seem
• 3. Genes major contributor
• To stability/lack of change for personality

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Ch 6 Genetics and Personality

• Sexual orientation
• Is sexual orientation heritable?
• Conventional wisdom yes
• Early Bailey studies
• But these studies were criticized
• Small n
• Unrepresentative samples

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Ch 6 Genetics and Personality

• Sexual orientation
• Bailey et al (2000)
• 92 exclusively heterosexual
• Significant, but much smaller than previously
  thought

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Ch 6 Genetics and Personality

• If mz twin smokes, 16x more likely to smoke
  oneself
• But heritabilities a bit inconsistent, .3-.5
• More heritable
• .5-.6

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Ch 6 Genetics and Personality

• Marriage
• Whether one marries or stays single
• Marital satisfaction

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Ch 6 Genetics and Personality

• Martin et al (1986) heritable contribution to
• Attitudes toward Sabbath observance
• Divine law
• Interest in becoming religious figure (e.g.,
  priest)

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Ch 6 Genetics and Personality

• Plomin et al (1990)
• 20 due to shared envt (e.g., presence of TV,
  TV-watching parents)

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Lykken Tellegen (1996)

• Predicting happiness
• Education
• SES
• Income
• Marital status
• Demographics

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Lykken Tellegen (1996)

• DZ twins
• Rate happiness
• Age 20 age 30
• Twin 1 20 twin 1 30, r .6
• Twin 1 20 twin 2 30, r .48
• .48/.60 .80

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Lykken Tellegen (1996)

• Conclusions
• 1. The reported WB of ones identical twinis a
  far better predictor than ones own life
  circumstances
• 2. trying to be happier is like trying to be
  tallercounterproductive
• 3. individual differences in human happinessare
  primarily a matter of (genetic) chance

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Ch 6 Genetics and Personality

• Eros love at first sight
• Ludus dont get to serious, just fun
• Storge value reliability in partners
• Pragma pragmatic, mate with similar other
• Mania love-sick (e.g., insomnia when in love)
• Agape selfless enjoy giving

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Ch 6 Genetics and Personality

• But
• 1. Error no test is error-free
• 2. Shared envt
• 3. Unshared envt

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Ch 6 Genetics and Personality

• Same parents
• Same toys
• Same schools, neighborhoods
• E.g., different treatment from parents
• E.g., diff friends at school
• E.g., one at paint chips

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Ch 6 Genetics and Personality

• Shared vs. unshared which matters more?
• Shared
• Unshared

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Ch 6 Genetics and Personality

• Shared envt nothing?
• Religious beliefs
• Political orientation
• Health behaviors (like diet, exercise)

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Behavioral Genetics

• Parenting - not very relevant?
• Which sperm/egg combo was given
• Sorry, wrong sperm!

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Behavioral Genetics

• What about adopting children?
• No genes
• Shared doesnt matter much
• What is the point of adoption then?

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Ch 6 Genetics and Personality

• Challenge to environmentalism
• Must recreate itself
• why are children in same family so diff from
  each other?