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PSYCHOLOGY(8th Edition, in Modules)

David Myers

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Behavior Genetics and Evolutionary

Human Diversity

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Behavior Genetics: Predicting Individual Differences

Behavior Geneticists study our differences and weigh the relative effects

of heredity and environment.

This used to be called the Nature vs. Nurture Debate

Now it is called Nature via Nurture

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Genes: Our Codes for LifeIn the nucleus of a cell chromosomes (46) containing DNA (deoxyribonucleic acid)

are situated.

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Genes: Our Codes for Life

Segments within DNA constitute genes making proteins to determine our development.

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Genome

Genome is the set of complete instructions for making an organism Containing all the

genes in that organism. Thus human genome makes us human and the genome

for drosophila makes it a common house fly.

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Genetics

• Humans have 30,000 genes.

• 99.9% of your DNA matches that of every other human

• Our genes are responsible for predisposing our appearance and behavior.

• Predisposition only means that the possibility of development of (x) exists.

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How do we study the interaction of nature and nurture

• Twin Studies

• Adoption Studies

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Twin Biology

To study the effects of heredity and environment two sets of twins, identical

and fraternal, have come in handy.

MonozygoticTwins

Dizygotic Twins

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Twin and Procedures

Behavior geneticists study the effects of shared and unique environments on total or partial

genetic makeup.

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Separated Twins

A number of studies have looked at identical twins raised separately from birth or close

there after and have found a number of similarities.

Separated Twins

Personality, Intelligence

Abilities, Attitudes

Interests, Fears

Brain Waves, Heart Rate

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Separated Twins

Critics of separated twin studies note that such similarities can be found between strangers. However, researchers point out that differences between fraternal twins are greater than identical twins.

Bob

Sach

a

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Adoption Studies

Opposed to twin studies, adoption studies suggest that adoptees (who may be

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

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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 experiences?

Do siblings, despite sharing half of their genes, have different combinations of the other half genes?

Ultimate question: Does parenting have an effect?

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Parenting

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

Parenting Influences children’s

Attitudes, Values

Manners, Beliefs

Faith, Politics

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Temperament Studies

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

twins express similar temperaments, suggesting heredity predisposes temperament.

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Heritability

Heritability refers to the extent to which the differences among people are

attributable to genes.

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Nature and Nurture

Some human traits are fixed, like having two eyes, most psychological traits are liable to

change with environmental experience.

So genes provide choices to the organism to change its form or traits when

environmental variables change. Therefore genes are pliable or self-regulating.

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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 angry responses from his parents. A stressful

environment can trigger genes to manufacture neurotransmitters leading to

depression.