11Nature, Nurture, andHuman DiversityFall 2008Chapter 32What is the Nature-Nurture Debate?What accounts for our behavioralproclivities, talents, abilities,personality, pre-dispositions,intelligence, temperament? Are we born with these differences?(Nature) Or, do we acquire these differencesfrom our parents’ influence, societalinfluence, friends, etc? (Nurture)3What is the Nature-NurtureDebate? What accounts for our behavioralproclivities, talents, abilities,personality, pre-dispositions,intelligence, temperament? Are we born with these differences?(Nature) Or, do we acquire these differences fromour parents’ influence, societal influence,friends, etc? (Nurture)4Nature, Nurture, and HumanDiversityEvolutionary Psychology:Understanding Human Nature Natural Selection An Evolutionary Explanation of Human Sexuality Males: healthy/fertile/nurturing mates Females: healthy/security/strength Critiquing the Evolutionary Perspective Post-hoc? Promotes Status Quo5Nature, Nurture, and HumanDiversityParents and peersCultural Influences Variations Across Cultures Culture and the Self Collectivistic Individualistic Culture and Child-Rearing Protective Punitive Promote independence6Nature, Nurture, and HumanDiversity Developmental Similarities AcrossGroups Gender Development Gender Similarities and Differences27Nature, Nurture, and HumanDiversityGenderDevelopment The Nature of Gender The Nurture of GenderReflections onNature and Nurture8Nature, Nurture, and HumanDiversityBehavior: Speak differentlanguagesBrain: Asymmetry of brainacross gendersBiology: May changeduring developmentGenes: Genetic anomaliesmay make us differentDifferencesBrain: Same brainarchitectureBehaviors: Speak languageBiology: Organs and bodyfunctions sameGenes: Same set ofchromosomesSimilarities9Behavior Genetics: PredictingIndividual DifferencesBehavior Geneticists study our differences andweigh the relative effects of heredity andenvironment.10Genes: Our Codes for LifeChromosomes containing DNA (deoxyribonucleic acid)are situated in the nucleus of a cell.11Genes: Our Codes for LifeSegments within DNA consist of genes thatmake proteins to determine our development.12GenomeGenome is the set of complete instructions formaking an organism, containing all the genes inthat organism. Thus, the human genome makesus human, and the genome for drosophila makesit a common house fly.313Twin BiologyStudying the effects of heredity andenvironment on two sets of twins, identical andfraternal, has come in handy.14Twins and ProceduresBehavior geneticists’ effects of shared and uniqueenvironments on total or partial genetic makeup.15Twins Separated at BirthA number of studies compared identical twinsraised separately from birth, or close thereafter,and found numerous similarities.Interests, FearsBrain Waves, Heart RateAbilities, AttitudesPersonality, IntelligenceSeparated Twins16Separated TwinsCritics of separated twin studies note that suchsimilarities can be found between strangers.Researchers point out that differences betweenfraternal twins are greater than identical twins.Bob Sacha17Adoption StudiesAdoption studies, as opposed to twin studies,suggest that adoptees (who may be biologicallyunrelated) tend to be different from theiradoptive parents and siblings.18Adoptive StudiesAdoptive studies strongly point to the simplefact that biologically related children turn out tobe different in a family. So investigators ask:Do siblings have differing environmental experiences?Do siblings, despite sharing half of their genes, havedifferent combinations of the other half of their genes?Ultimate question: Does parenting have an effect?419ParentingParenting does have an effect on biologicallyrelated and unrelated children, but not all.Faith, PoliticsManners, BeliefsAttitudes, ValuesParenting Influenceschildren’s20Temperament StudiesTemperament refers to a person’s stableemotional reactivity and intensity. Identicaltwins express similar temperaments, suggestingheredity predisposes temperament.21HeritabilityHeritability refers to the extent to which thedifferences among people are attributable to genes.22Group DifferencesIf genetic influences help explain individualdiversity in traits, can the same be said aboutgroup differences?Not necessarily. Individual differences inweight and height are heritable and yetnutritional influences have made westernersheavier and taller than their ancestors were acentury ago.23Nature and NurtureSome human traits are fixed, such as havingtwo eyes. However, most psychological traitsare liable to change with environmentalexperience.Genes provide choices for the organism tochange its form or traits when environmentalvariables change. Therefore, genes are pliable orself-regulating.24Gene-Environment InteractionGenes can influence traits which affectresponses, and environment can affect geneactivity.A genetic predisposition that makes a childrestless and hyperactive evokes an angryresponse from his parents. A stressfulenvironment can trigger genes to manufactureneurotransmitters leading to depression.525Gene-Environment InteractionGenes and environment affect our traitsindividually, but more important are theirinteractive effects.People respond differently toRowan Atkinson (Mr. Bean) than Orlando Bloom.Rex FeaturesAlessia Pierdomenico/Reuters/Corbis26The New Frontier:Molecular GeneticsMolecular genetics is a branch extension ofbehavior genetics that asks the question, “Dogenes influence behavior?”27Molecular Genetics:Promises and PerilsMolecular geneticists are trying to identifygenes that put people at risk for disorders. Withthis kind of knowledge, parents can decide toabort pregnancies in which the fetus issuspected of having such disorders.However, this opens up a real concernregarding ethical issues involving such choices.28Evolutionary Psychology:Understanding Human NatureMolecular genetics studies why we asorganisms are distinct.Evolutionary psychology studies why we ashumans are alike. In particular, it studies theevolution of behavior and mind usingprinciples of natural selection.29Natural SelectionNatural selection is an evolutionary processthrough which adaptive traits are passed on toongoing generations because these traits helpanimals survive and reproduce.30Artificial SelectionBiologists like Belyaev and Trut (1999) wereable to artificially rear and domesticate wildfoxes, selecting them for friendly traits.Any trait
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