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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
rr..
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
n mach
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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