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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 on behavior

and personality.

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Nurture and Human Diversity

Parents Prenatal Experience

Peer Influence

Culture Gender

Environment:

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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•Located within bone cells

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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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Genome

Genome - 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.

The threadlike structures that contain genes are called

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Genomes

Synapse

s

Neuro

ns

Chromoso

mes

Horm

ones

0% 0% 0%0%0%

1. Genomes

2. Synapses

3. Neurons

4. Chromosomes

5. Hormones

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DNA is a complex

8 Molecu

le

Synapse

Gene

Genome

Neuro

n

0% 0% 0%0%0%

1. Molecule

2. Synapse

3. Gene

4. Genome

5. Neuron

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The biochemical units of heredity that make up the chromosomes are called

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Genomes

Molecu

lar gene...

Here

dity

Behavior genet..

.

genes

0% 0% 0%0%0%

1. Genomes

2. Molecular genetics

3. Heredity

4. Behavior geneticists

5. genes

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Twin BiologyStudying the effects of heredity and environment

on twins1.Identical twins raised together - share the same portion of the chromosomes that determines a single trait or ____________2.Identical twins raised apart – same genes, different environment3.Fraternal twins – different genes, same environment

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Identical Twins Studies

Twin Studies

Temperament, Intelligence

Abilities, Attitudes

Interests, Fears

Brain Waves, Heart Rate

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

IdenticalTwins and IQ• Bouchard Study• .69 Correlational

coefficient for IQ tests of identical twins raised apart.

• .88 raised together.

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Twins and Personality

Temperament - a person’s stable emotional reactivity and intensity…part of your personality that you are born with. •Extroverted (outgoing) & fearless v. Introverted (shy) & cautious•Identical twins express similar temperaments

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Separated Identical Twins and Personality

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

Bob

Sach

a

Twin Studies

Temperament, Intelligence

Abilities, Attitudes

Interests, Fears

Brain Waves, Heart Rate

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Adoption Studies

•Adoptees - Personalities are 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 – outgoing– Agreeableness - cooperative and

compassionate– Conscientiousness – self-disciplined– Neuroticism – negative emotions– Openness – willingness to experience new things

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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 0.0 to 1.00 = genes do not contribute at all to individual differences

High environmentability1.0 = genes are the only reason for individual differences

High heritability

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

Applies to populations not individuals

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Heritability and Big 5

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• Big 5 Traits Heritability– Extroversion .67– Agreeableness .52– Conscientiousness .59– Neuroticism .48– Openness .63

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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 F

eatu

res

Ale

ssia P

ierd

om

en

ico/R

eu

ters/C

orb

is

Twins Studies

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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

Studies of identical twins who had been reared apart most clearly highlight the importance of ________

in personality development.

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Natu

ral s

election

Muta

tion

Adoptive re

lative

s

Home envir

onments

Genetic p

redisp

ositions

0% 0% 0%0%0%

1. Natural selection

2. Mutation

3. Adoptive relatives

4. Home environments

5. Genetic predispositions

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Adoptive parents are most likely to influence

the ________ of their adopted children.

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Adult height

Politica

l atti

tudes

Adult weigh

t

Extra

version

personali

ty

0% 0% 0%0%0%

1. Adult height

2. Political attitudes

3. Adult weight

4. Extraversion

5. personality

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Heritability refers to the extent to which

27 Unrelate

d individuals s

h...

An obtain resu

lt occu

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Nurtu

re contro

ls a tr

ait ...

Infan

t perso

nality dete

r...

Variation among i

ndivid...

0% 0% 0%0%0%

1. Unrelated individuals share common genes

2. An obtain result occurred by chance

3. Nurture controls a trait rather than nature

4. Infant personality determines adult personality

5. Variation among individuals can be attributed to their differing genes

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Molecular genetics seeks to

28 Identify

specifi

c genes i

n...

Assess

the re

lative contr.

..

Focu

s mainly on w

hat m...

Treat individuals

with m

...

Desig

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ines that in

...

0% 0% 0%0%0%

1. Identify specific genes influencing behavior

2. Assess the relative contributions of nature and nurture

3. Focus mainly on what makes us so much alike as humans

4. Treat individuals with mental disorders

5. Design machines that interact best with people

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Evolutionary Psychology

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Evolutionary psychology - studies the evolution of behavior and mind using principles of natural selection.•Adaptive behaviors are those that promote reproductive success

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Natural Selection

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

Examples

• Fear of Heights

• Fear of the Dark

• Fear of ostracism

• Overeating

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Artificial Selection

Biologists 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

. Tru

r, Am

erica

n S

cien

tist (19

99

) 87

: 16

0-1

69

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Human SexualityGender Differences in Sexuality

Question (summarized) MaleFemal

e

Casual sex 60% 35%

Sex for affection 25% 48%

Think about sex everyday 54% 19%

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Mating Preferences

Males•Mate with multiple females to spread genes•Look for youthful appearance and at ages associated with peak fertility.•If older wants younger women •IF teenager want women a few yrs. older

Females•Select one male because of the higher costs involved with pregnancy, nursing and childcare.•Look for maturity, dominance, affluence and boldness

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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• Explain how an evolutionary psychologist might explain why humans developed into omnivores, eating both meat and plants.

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