Download Twin Studies - Solon City Schools

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
Environment:
Parents
Prenatal
Experience
Peer Influence
Culture
Gender
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Genes: Our Codes for Life
DNA (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 Life
Genes - 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.
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The threadlike structures that
contain genes are called
Genomes
Synapses
Neurons
Chromosomes
Hormones
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DNA is a complex
Molecule
Synapse
Gene
Genome
Neuron
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The biochemical units of heredity that
make up the chromosomes are called
Genomes
Molecular genetics
Heredity
Behavior geneticists
genes
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Twin Biology
Studying the effects of heredity and environment on
twins
1. 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 environment
3. 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
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coincidental similarities.
IdenticalTwins and IQ
• Bouchard Study
• .69 Correlational
coefficient for IQ tests
of identical twins raised
apart.
• .88 raised together.
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.
Twin Studies
Temperament, Intelligence
Abilities, Attitudes
Interests, Fears
Bob Sacha
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
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Personality
• Big 5 Traits
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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:
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Attitudes
Values
Manners
Faith
politics
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Heritability
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 1.0
0 = genes do not contribute at all to individual differences
 High environmentability
1.0 = 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
Two boys raised in a barrel with
identical environmental conditions would
have a heritability of ______?
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Heritability and Big 5
• Big 5 Traits
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Extroversion
Agreeableness
Conscientiousness
Neuroticism
Openness
Heritability
.67
.52
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.63
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Gene-Environment Interaction
Genes and environment affect our traits
individually, but more important are their
interactive effects.
Alessia Pierdomenico/Reuters/Corbis
Rex Features
People respond differently to
Rowan Atkinson (Mr. Bean) than Orlando bloom.
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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 24
influencing behavior
Studies of identical twins who had been reared apart
most clearly highlight the importance of ________ in
personality development.
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Natural selection
Mutation
Adoptive relatives
Home environments
Genetic predispositions
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Adoptive parents are most likely to influence
the ________ of their adopted children.
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Adult height
Political attitudes
Adult weight
Extraversion
personality
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Heritability refers to the extent to
which
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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
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
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.
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Examples
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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.
L.N. Trur, American Scientist (1999) 87: 160-169
Any trait that is favored naturally or artificially
spreads to future generations.
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Human Sexuality
Gender 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 Preferences
Females
•Select one male because
of the higher costs
involved with pregnancy,
nursing and childcare.
•Look for maturity,
dominance, affluence and
boldness
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
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women a few yrs. older
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
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of individual choices
• Explain how an evolutionary psychologist
might explain why humans developed into
omnivores, eating both meat and plants.
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