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Genetics, Evolutionary Psychology, and Behavior

3C

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Behavior Genetics: Predicting Individual Differences

Behavior Geneticists - study our differences and weigh the relative effects

of heredity and environment.

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Nurture and Human DiversityEnvironment:

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Genes: Our Codes for LifeDNA (deoxyribonucleic) – complex molecule containing the genetic info that makes up the chromosome. Chromosomes – threadlike structures made up of DNA molecules that contain genes•Any genetic basis for a trait are located in chromosomes •23 from mother and 23 from father

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Genes: Our Codes for LifeGenes - small segments of DNA that are the biochemical units of heredity. •Capable of synthesizing a protein•One or more genes are responsible for expression or repression of a particular trait

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GenomeGenome - set of complete instructions for making an organism, containing all the genes in that organism. • human genome makes us human•the genome for drosophila makes it a common house fly.

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Twins StudiesIdentical twins raised separately

Twin Studies

Caution: any two strangers are likely to share coincidental similarities.

IdenticalTwins and IQ• Bouchard Study• .69 Correlational

coefficient for IQ tests of

• .88

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IdenticalTwins and Personality

Temperament -

•Identical twins express similar temperaments, suggesting heredity predisposes temperament.

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Separated Twins and Personality

•Identical Twins separated at birth – no extreme differences in personality •Differences between fraternal twins are greater than identical twins.

Bob Sacha

Twin StudiesTemperament, Intelligence

Abilities, AttitudesInterests, Fears

Brain Waves, Heart Rate

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Adoption Studies and Personality

•Adoptees - tend to be different from their adoptive parents and siblings.•Environment shared by a family’s children has relatively no impact on their personalities

Personality• Big 5 Traits

– Extroversion– Agreeableness– Conscientiousness– Neuroticism– Openness

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Twins Studies

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Parental Influence• Parents do

influence:– Attitudes– Values– Manners– Faith– politics

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Heritability

Two boys raised in a barrel with identical environmental conditions would have a heritability of ______?

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

Heritability is numerical value with a range from

For human behavior, almost all estimates of heritability are in the moderate range of .30 to .60.

Applies to populations not individuals

Heritability and Big 5

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• Big 5 Traits Heritability– Extroversion– Agreeableness– Conscientiousness– Neuroticism– Openness

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Gene-Environment Interaction

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

interactive effects.

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

Rex Features

Alessia Pierdomenico/R

euters/Corbis

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The New Frontier: Molecular Genetics

Molecular genetics is a branch extension of behavior genetics that asks the

question, “Do genes influence behavior?” It seeks to identify the specific genes

influencing behavior

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Evolutionary Psychology

.Evolutionary psychology - studies the evolution of behavior and mind using principles of natural selection.

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Natural SelectionNatural selection - evolutionary process through which adaptive traits are passed on to ongoing generations because these traits help animals survive and reproduce.

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Artificial SelectionBiologists like Belyaev and Trut (1999) were able to artificially rear and domesticate wild foxes, selecting them for friendly traits.

Any trait that is favored naturally or artificiallyspreads to future generations.

L.N. Trur, Am

erican Scientist (1999) 87: 160-169

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Human SexualityGender Differences in Sexuality

Question (summarized) Male Female

Casual sex 60% 35%Sex for affection 25% 48%

Think about sex everyday 54% 19%

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Mating PreferencesMalesFemales

Criticisms of Evolutionary Psych

• Works backwards to propose and explanation

• Underestimates cultural expectations on human sexual behavior

• Unethical and immoral men could use explanations to rationalize behavior toward women

• Does not consider the importance of individual choices

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