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Behavior Genetics and Evolutionary Psychology
Module 5
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Behavior Genetics and Evolutionary Psychology
Behavior Genetics: Predicting Individual Differences Genes: Our Codes for Life Twin and Adoption Studies Temperament and Heredity Nature and Nurture Gene-Environment Interaction
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Behavior Genetics and Evolutionary Psychology
Evolutionary Psychology: Understanding Human Nature Natural Selection An Evolutionary Explanation of
Human Sexuality
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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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Genes: Our Codes for Life
Chromosomes containing DNA (deoxyribonucleic acid) are situated in
the nucleus of a cell.
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Genes: Our Codes for Life
Segments within DNA consist of genes that make proteins to determine our
development.Dominant vs. Recessive Genes:
Examples
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Genome and Phenome
GENOTYPE
The genetic makeup, as distinguished from the physical appearance, of an organism or a group of organisms.
*How ugly you are supposed to be.
PHENOTYPE
The observable physical or biochemical characteristics of an organism, as determined by both genetic makeup and environmental influences.
How ugly you actually are.
--can change your phenotype-colored hair, contacts, etc..
.
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Twin and Adoption Studies: Handout 5-1Studying the effects of heredity and
environment on two sets of twins, identical and fraternal, has come in
handy.
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Separated Twins
Critics of separated twin studies note that such similarities can be found
between strangers. Researchers point out that differences between fraternal twins
are greater than identical twins.
Bob
Sach
a
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MINNESOTA TWIN STUDY
Thomas Bouchard—good name to remember!
Part 1: 1979—week-long medical and psychological assessment of Identical and Fraternal twins separated in early life and reared apart.
Part 2: --10 year __________study of aging. Adult twins between ages of 24 and 66 at 1st assessment asked to return.
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Minnesota Twin Study Cont. This study showed examples of similarities. Jerry and Mark Newman (separated at birth). Shared characteristics-firefighters, same
mustache and sideburns, same glasses, One studied forestry in college-other wanted to but worked for city trimming trees instead.
One installed fire alarms-other installed sprinklers.
Both bachelors and attracted to same type of woman.
Both only drink Budweiser ETC>>>
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Separated Twins
Separated Twins
Personality, Intelligence
Abilities, Attitudes
Interests, Fears
Brain Waves, Heart Rate
A number of studies compared identical twins reared separately from birth, or close thereafter, and found numerous
similarities.
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Minnesota Twin Study
Studies show that Identicals have 85% similarity in IQ and Fraternals-60%.
Behavior geneticists say ½ the variation for IQ is because of genetics.
Critics: Same prenatal environment Spend avg. of 5 mths together b/f
being separated Avg. of 2 years together before
second study.
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Biological Versus Adoptive Relatives
Adoption studies, as opposed to twin studies, suggest that adoptees (who may
be biologically unrelated) tend to be different from their adoptive parents and
siblings.
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Adoptive StudiesAdoptive 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 of their genes?
Ultimate question: Does parenting have an effect?
Parenting
Parenting Influences Children’s
Attitudes, Values
Manners, Beliefs
Faith, Politics
Parenting does have an effect on biologically related and unrelated
children.
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Temperament and Heredity-Handout 5-2
Temperament refers to a person’s stable emotional reactivity and intensity.
Psychologists argue that temperaments are largely inherited based on twin
studies: Identical twins express more similar temperaments, in comparison to
fraternal twins. Examples: activity, emotionality, sociability
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Nature and Nurture
Some human traits are fixed, such as having two eyes. However, most
psychological traits are liable to change with environmental experience.
Genes provide choices for 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.Three types:
1. Passive genotype correlation.2. Reactive genotype-environment
correlation3. Active Genotype-environment
correlationA genetic predisposition that makes a child restless and hyperactive evokes an angry
response from his parents. A stressful environment can trigger genes to manufacture
neurotransmitters leading to depression.
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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
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Evolutionary Psychology: Understanding Human Nature-Handout 5-3
Evolutionary psychology studies why we as humans are alike. In particular, it studies the evolution of behavior and
mind using principles of natural selection.
This approach is helpful in raising the “why of behavior” question that is so
central to the discipline of psychology.
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Natural Selection
Natural selection is an 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 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
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: 16
0-1
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Human Traits
A number of human traits have been identified as a result of pressures
afforded by natural selection.
Why do infants fear strangers when they become mobile?
Why do people fear spiders and snakes and not electricity and guns?
How are men and women alike? How and why do men’s and women’s sexuality differ?
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Human Sexuality
Question (summarized) MaleFemal
e
Casual sex 58% 34%
Sex for affection 25% 48%
Think about sex everyday 54% 19%
Males and females, to a large extent, behave and think similarly. Differences in
sexes arise in regards to reproductive behaviors.
Gender Differences in Sexuality
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Natural Selection & Mating Preferences-Handout 5-4
Natural selection has caused males to send their genes into the future by mating with multiple females since males have lower
costs involved. THERE IS A GENETIC ARGUMENT AS TO WHY MEN ARE “PLAYERS”—just trying to
spread their genetic code.However, females select one mature and caring male because of the higher costs involved with pregnancy and nursing.
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Mating Preferences
Males look for youthful appearing females in order to pass their genes into the future.
Females, on the other hand, look for maturity, dominance, affluence, and
boldness in males.
Data based on 37 cultures.
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THE COOLIDGE EFFECT
In certain animal species, a male that has become sexually exhausted from repeated copulation with the same female will demonstrate renewed vigor if presented with a succession of new females.
This phenomenon is called the Coolidge Effect b/c of exchange b/w Pres. And Mrs. Calvin Coolidge.
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Critiquing the Evolutionary Perspective
Evolutionary psychologists take a behavior and work backward to explain it in terms of natural selection.
Evolutionary psychology proposes genetic determinism and undercuts morality in establishing society.
Where genders are unequal, gender preferences are wide, but when they are closely equal, preferences
narrow down.
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Evolutionary Psychologists Reply
Evolutionary psychologists argue that we need to test behaviors that expound evolutionary principles.
Evolutionary psychologists remind us how we have adapted, but do not dictate how we ought to be.
Males and females are more alike than different, and if we study these differences we can establish their
causes.
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ALTRUISM
Exercise - Essay by Lewis Thomas Assignment
Is altruism a genetic predetermined factor. Or is it, in the words of Richard Dawkins. “[that] we are born selfish. If we find that human behavior is altruistic, we will be faced with something that needs explaining.”