The Nature & Nurture of Behavior The Nature vs. Nurture Debate The Big Question: How much are who we are— how we think, act and behave—shaped by nature (our genes) versus nurture (our environment)? The Nature Nurture Debate Make two columns on a sheet of paper - 1) nature; 2) nurture Write characteristics you believe are mostly nature or mostly nurture in the appropriate column If the characteristic was nurture, what seemed to be the influences? The Nature vs. Nurture Debate The Simple View Behavior = genes + parental influence The Realistic View Behavior = genes + prenatal influence + parental influence + nutrition + family income + education + culture + traumas + luck … The Nature vs. Nurture Debate Two ways to determine the effects of nature versus nurture: Twin studies Adoption studies The Nature vs. Nurture Debate Identical twins are genetically identical. – They share 100% of their genes. Fraternal twins are no more genetically similar than two siblings. – They share 50% of their genes. Nature: Twin studies Identical twins are more similar than fraternal twins in – Abilities – Interests – Personality traits Extraversion (outgoing) Neuroticism (emotional instability) Nature: Identical twins reared apart Even identical twins reared apart have similarities in – Personality – Abilities – Interests Twin Studies Comparing identical twins separated at birth with those reared together Twin studies video Nature: Adoption Studies Q: Are adopted kids more like their biological parents or their adopted parents? Adopted children’s personalities are much more similar to their biological parents’ personalities than to their adoptive parents’ personalities. Nurture: Environmental Influences Prenatal environment Nurture: Environmental Influences Parents matter because they provide experiences that can lead to better brain development. Impoverished environment After 60 days in an enriched environment with more toys, more companions, and more to explore, young rats had: •7 – 10% bigger brains •20% more synapses Enriched environment Nurture: Other ways parents matter Parents may not influence their children’s personalities much, but parents do influence their children’s: •Attitudes •Interests •Values •Education •Manners •Discipline •Faith •Responsibility •Politics Nurture: Other ways parents matter Parental influence is also more evident at the extremes. – Abused children versus very loved children Nurture: Peer influence Peer influence may exceed parental influence, especially as children and adolescents begin to spend more time outside the home. Siblings are also important “With us for the whole journey” Are Gender Differences Due to Nature or Nurture?? Gender Differences— Evidence for Nature Testosterone – Linked to desire for status and dominant behavior – Leads to muscle growth – Females exposed to excess testosterone in utero prefer more masculine toys, activities, and careers – Related to spatial ability Gender Differences— Evidence for Nature Animal studies – Males found to be more aggressive among many species – Vervet monkeys show similar gender preference with toys as humans – Evidence for sex differences in spatial ability Gender Differences— Evidence for Nature Baby studies – Girls respond more to sounds of distress, have greater pain sensitivity and make more eye contact than boys in first week of life – Compared to girls, newborn boys more interested in looking at a physical object and less interested in looking at a face Gender Differences— Evidence for Nature The sad story of David Reimer (AKA John/Joan) Gender Differences— Evidence for Nurture Parents of boys more likely to report that they have mathematical talent than parents of girls (despite similar grades) Children with male names are more likely to be rated as strong, intelligent, and active Gender Differences— Evidence for Nurture Some evidence that differences in cognitive abilities have decreased over time Other societal attitudes, expectations, prejudices Evolutionary Psychology Natural Selection Mutation Evolutionary Psychology Goal of organism is to spread genes. Behavior will reflect this goal. Is used to answer the “why’s” of human behavior. Evolutionary Psychology 1. You are on a boat that overturns. It contains your 5-year-old and 1-year-old children (of the same sex). The boat sinks and you can save only one. Whom do you choose to save? 2. That same boat (you are slow to learn lessons) contains your 40-year-old and 20- year-old children (both of the same sex). Neither can swim. As the boat sinks, whom do you choose to save? Evolutionary Psychology 3. Would you rather marry (or have married) someone older or younger than yourself? 4. Of the following six, which three are most important in the selection of your mate? Circle the answers. a. good financial prospects b. physical attractiveness c. good looks d. ambition and industriousness e. a caring and responsible personality f. an exciting personality Evolutionary Psychology 5. You and your spouse are the proud parents of a new child. The grandparents are ecstatic. Who do you think will be kinder to the child? a. The mother of the mother b. The mother of the father 6. Who will mourn more at the death of a child? Give the answer for each pair. a. father or mother b. parents of the father or parents of the mother c. younger parents or older parents Evolutionary Psychology Across cultures, men are more sexually promiscuous and more likely to initiate sexual contact than women. Buss cross-cultural study Evolutionary Psychology • Buss cross-cultural study • Men preferred attractive physical features suggesting youth and health Women preferred resources and social status Study of 37 different cultures: Characteristics Characteristics preferred preferred by males: by females: 1. Kindness and 1. Kindness and understanding understanding 2. Intelligence 2. Intelligence 3. Physical attractiveness 3. Exciting personality 4. Exciting personality 4. Good health 5. Good health 5. Adaptability 6. Adaptability 6. Physical attractiveness 7. Creativity 7. Creativity 8. Desire for children 8. Good earning capacity 9. College graduate 9. College graduate 10.Good heredity 10. Desire for children 11.Good earning potential 11. Good heredity 12.Good housekeeper 12. Good housekeeper 13.Religious orientation 13. Religious orientation Singh Waist-to-hip Ratio Study – Which of these figures did men rate as most attractive across cultures? True or False? 1. People’s differing divorce risks are about 50% attributable to genetic factors 2. Adopted children’s personality traits are more similar to their adoptive parents than to their biological parents. 3. Two children in the same family are on average as different from one another as are pairs of children selected randomly from the population. 4. In many places around the world, females are more likely than males to initiate sexual activity. 5. A child who hears English spoken with one accent at home and another at school will end up with the same accent as his or her peers, not his or her parents. 6. Even when families discourage traditional gender-typing, children still organize themselves into “boy worlds” and “girl worlds,” each guided by rules for what boys and girls do.
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