1 1 Nature, Nurture, and Human Diversity Chapter 4 2 What is the Nature-Nurture Debate? What accounts for our behavioral proclivities, talents, abilities, personality, pre-dispositions, intelligence, temperament? Are we born with these differences? (Nature) Or, do we acquire these differences from our parents’ influence, societal influence, friends, etc? (Nurture) 3 Nature, Nurture, and Human Diversity Evolutionary Psychology: Understanding Human Nature Natural Selection Are all traits adaptive? An Evolutionary Explanation of Human Sexuality Males: healthy/fertile/nurturing mates Females: healthy/security/strength Critiquing the Evolutionary Perspective Post-hoc? Promotes Status Quo (e.g., infidelity) 4 Nature, Nurture, and Human Diversity Parents and peers Cultural Influences Variations Across Cultures Culture and the Self Collectivistic Individualistic Culture and Child-Rearing Protective Punitive Promote independence 5 Nature, Nurture, and Human Diversity Developmental Similarities Across Groups Personality, language Gender Development Gender roles Gender Similarities and Differences Aggression Social power Social connectedness 6 Nature, Nurture, and Human Diversity Gender Development The Nature of Gender The Nurture of Gender Reflections on Nature and Nurture2 7 Nature, Nurture, and Human Diversity Similarities Differences Genes: Same set of chromosomes Genes: Genetic anomalies may make us different Biology: Organs and body functions same Biology: May change during development Brain: Same brain architecture Brain: Asymmetry of brain across genders Behaviors: Speak language Behavior: Speak different languages 8 Behavior Genetics: Predicting Individual Differences Behavior Geneticists study our differences and weigh the relative effects of heredity and environment. 9 Twin Biology Studying the effects of heredity and environment on two sets of twins, identical and fraternal, has come in handy. 10 Twins and Procedures Behavior geneticists’ effects of shared and unique environments on total or partial genetic makeup. 11 Twins Separated at Birth A number of studies compared identical twins raised separately from birth, or close thereafter, and found numerous similarities. Separated Twins Personality, Intelligence Abilities, Attitudes Interests, Fears Brain Waves, Heart Rate The “James” Twins 12 Separated Twins Critics of separated twin studies note that such similarities can be found between strangers. Researchers point out that differences between fraternal twins are greater than identical twins.3 13 Adoption Studies • Adoption studies, as opposed to twin studies, suggest that adoptees (who may be biologically unrelated) tend to be different from their adoptive parents and siblings. • Personality vs. attitudes, values, religious views 14 Adoptive Studies Adoptive studies strongly point to the simple fact that biologically related children turn out to be different in a family. So investigators ask: Do siblings have differing environmental experiences? Do siblings, despite sharing half of their genes, have different combinations of the other half of their genes? Ultimate question: Does parenting have an effect? 15 Parenting Parenting does have an effect on biologically related and unrelated children, but not all. Parenting Influences children’s Attitudes, Values Manners, Beliefs Faith, Politics 16 Temperament Studies Temperament refers to a person’s stable emotional reactivity and intensity. Identical twins express similar temperaments, suggesting heredity predisposes temperament. 17 Heritability Heritability refers to the extent to which the differences among people are attributable to genes. 18 Group Differences If genetic influences help explain individual diversity in traits, can the same be said about group differences? Not necessarily. Individual differences in weight and height are heritable and yet nutritional influences have made westerners heavier and taller than their ancestors were a century ago.4 19 Nature and Nurture Some human traits are fixed, such as having two eyes. However, most psychological traits are liable to change with environmental experience. Genes provide choices for the organism to change its form or traits when environmental variables change. Therefore, genes are pliable or self-regulating. 20 Gene-Environment Interaction Genes can influence traits which affect responses, and environment can affect gene activity. A genetic predisposition that makes a child restless and hyperactive evokes an angry response from his parents. A stressful environment can trigger genes to manufacture neurotransmitters leading to depression. Outgoing, attractive child vs. introverted, less attractive child. 21 Gene-Environment Interaction Genes and environment affect our traits individually, but more important are their interactive effects. People respond differently to Rowan Atkinson (Mr. Bean) than Orlando Bloom. Rex Features Alessia Pierdomenico/Reuters/Corbis 22 The New Frontier: Molecular Genetics Molecular genetics is a branch extension of behavior genetics that asks the question, “Do specific genes influence behavior?” 23 Molecular Genetics: Promises and Perils Molecular geneticists are trying to identify genes that put people at risk for disorders. With this kind of knowledge, parents can… decide to abort pregnancies in which the fetus is suspected of having such disorders. Take steps to address elevated risk for such disorders (e.g., learning disabilities). However, this opens up a real concern regarding ethical issues involving such choices. 24 Evolutionary Psychology: Understanding Human Nature Molecular genetics studies why we as organisms are distinct. Evolutionary psychology studies why we as humans are alike. In particular, it studies the evolution of behavior and mind using principles of natural selection.5 25 Natural Selection Natural selection is an evolutionary process through which adaptive traits are passed on to ongoing generations because these traits help animals survive and reproduce. Preference for fatty foods & sweets Skin tone vis-à-vis climate 26 Artificial Selection Biologists like Belyaev and Trut (1999) were able to artificially rear and domesticate wild foxes, selecting them for friendly traits. Dogs are
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