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Nature/Nature/NurtureNurture

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Behavior Genetics: Behavior Genetics: Predicting Individual Predicting Individual

DifferencesDifferencesBehavior GeneticistsBehavior Geneticists study our study our

differences and weigh the relative effects differences and weigh the relative effects of heredity and environment.of heredity and environment.

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Genes: Our Codes for LifeGenes: Our Codes for Life

ChromosomesChromosomes containing DNA containing DNA ((deoxyribonucleic aciddeoxyribonucleic acid) are situated in ) are situated in

the nucleus of a cell.the nucleus of a cell.

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Methods for studying Methods for studying Nature Vs. NurtureNature Vs. Nurture

Twin StudiesTwin Studies Adoption StudiesAdoption Studies

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Twin BiologyTwin Biology

Studying the effects of heredity and Studying the effects of heredity and environment on two sets of twins, environment on two sets of twins,

identical and fraternal, has come in identical and fraternal, has come in handy.handy.

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Twins and ProceduresTwins and Procedures

..

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Separated TwinsSeparated Twins

A number of studies compared identical A number of studies compared identical twins raised separately from birth, or twins raised separately from birth, or close thereafter, and found numerous close thereafter, and found numerous

similarities.similarities.Separated TwinsSeparated Twins

Personality, Personality, IntelligenceIntelligence

Abilities, AttitudesAbilities, Attitudes

Interests, FearsInterests, Fears

Brain Waves, Heart Brain Waves, Heart RateRate

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Separated TwinsSeparated Twins

Critics of separated twin studies note Critics of separated twin studies note that such similarities can be found that such similarities can be found

between strangers. Researchers point out between strangers. Researchers point out that differences between fraternal twins that differences between fraternal twins

are greater than identical twins.are greater than identical twins.

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Adoption StudiesAdoption Studies

Adoption studies, as opposed to twin Adoption studies, as opposed to twin studies, suggest that adoptees (who may studies, suggest that adoptees (who may

be biologically unrelated) tend to be be biologically unrelated) tend to be different from their adoptive parents and different from their adoptive parents and

siblings.siblings.

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Adoptive StudiesAdoptive Studies

Adoptive studies strongly point to the Adoptive studies strongly point to the simple fact that biologically related simple fact that biologically related children turn out to be different in a children turn out to be different in a

family. So investigators ask:family. So investigators ask:

Do siblings have differing 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?

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ParentingParenting

Parenting does have an effect on Parenting does have an effect on biologically related and unrelated biologically related and unrelated

children.children.

Parenting Influences Parenting Influences children’schildren’s

Attitudes, ValuesAttitudes, Values

Manners, BeliefsManners, Beliefs

Faith, PoliticsFaith, Politics

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Temperament StudiesTemperament Studies

Temperament refers to a person’s stable Temperament refers to a person’s stable emotional reactivity and intensity. emotional reactivity and intensity.

Identical twins express similar Identical twins express similar temperaments, suggesting heredity temperaments, suggesting heredity

predisposes temperament.predisposes temperament.

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Gene-Environment Gene-Environment InteractionInteraction

Genes can influence traits which affect Genes can influence traits which affect responses, and environment can affect responses, and environment can affect

gene activity.gene activity.

A genetic predisposition that makes a A genetic predisposition that makes a child restless and hyperactive evokes an child restless and hyperactive evokes an

angry response from his parents. A angry response from his parents. A stressful environment can trigger genes stressful environment can trigger genes

to manufacture neurotransmitters to manufacture neurotransmitters leading to depression.leading to depression.

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Gene-Environment Gene-Environment InteractionInteraction

Genes and environment affect our traits Genes and environment affect our traits individually, but more important are their individually, but more important are their

interactive effects.interactive effects.

People respond differently toRowan Atkinson (Mr. Bean) than Orlando bloom.

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