Transcript identical versus fraternal twins

 Which
is more
important? What
determines most of
our behavior? Our
genes? Or our
environment?
 Heredity
versus
the environment
NATURE VS. NURTURE

Universal people communicate both verbally and
nonverbally

enforce rules of etiquette

They avoid incest, fear snakes, and exchange gifts.

Universal people demonstrate modesty in sexual
behavior and bodily functions, even if they don’t wear
clothes.

Everywhere labor is divided by age and by gender. Men
are more aggressive than women; women provide more
child care.

Every culture has tools

Everywhere, people form beliefs about death and
disease, they plan for the future.

All cultures have taboos, including tabooed utterances.
Sanctions exist for crimes against society, and
mechanisms for dealing with theft, murder, and rape are
universal.

People everywhere recognize marriage

They mimic, flirt, envy, empathize, joke, and tease

They dance and make music
GENES: OUR CODES FOR LIFE
Chromosome
DNA (deoxyribonucleic
Genes
acid)
BLUE EYES?
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
Identical
Fraternal
twins
twins
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
IDENTICAL VERSUS FRATERNAL TWINS
TWIN AND ADOPTION STUDIES
SEPARATED TWINS
U
of MN studies on
identical twins separated
at birth- two Jims (hobbies,
habits, dog’s name, son’s
name)
 Gerald
 Work
 Like
Levey and Mark Newman, both:
as volunteer firefighters
the same beer (Budweiser)
 Are
attracted to the same kinds of
women
 Gerald
worked in forestry, Mark worked
for the city trimming trees (planned to go
to school for forestry)
 Both
liked to hunt, fish, watch John
Wayne movies and eat Chinese food
 Both
grew the same sideburns and
mustaches
 Used
the same speaking inflections and
hand gestures
Can
you find a twin in
this class?
Anecdotal
“Virtual
evidence
twins”
TWIN AND ADOPTION STUDIES
BIOLOGICAL VERSUS ADOPTIVE
RELATIVES
Genetic
relatives
Environmental
Children
relatives
in the same
family
Are
adopted children more
like their biological parents
or adoptive parents?
 Well,
it depends. Their personality
traits (how outgoing they are, how
friendly, their overall temperament)
were much more similar to their
biological parents.
 Environmental
factors have almost
no impact on your personality
 Do
parents even matter?

Parents influence:

Attitudes (such as toward education)

Values

Manners

Faith

Politics

Less credit, less blame
HERITABILITY
Heritability
“difference
among people”
How much of
the variation
among people
can be
attributed to
genes
IQ:
.22 at age 5, .54 - . 62 at
old age
Interests
(art, science etc.) .36
Psychiatric
illnesses:
Schizophrenia (.80), alcoholism
(.50 to .60)
Religiousness:
.11 to .22
HERITABILITY OF VARIOUS TRAITS
HERITABILITY
GROUP DIFFERENCES
Heritable
differences
between individuals does
not imply heritable group
differences
HERITABILITY
NATURE AND NURTURE
Influence
of adaptation
Nature and nurture work
together
Genes are
self-regulating

They react to the
environment
GENE-ENVIRONMENT INTERACTION
Genes
and experience
interact
Evocative
Mom
interactions
likes you better! 
NATURAL SELECTION AND ADAPTATION
Evolutionary
Natural
psychology
selection
Mutation
Adaptation
Fitness
EVOLUTIONARY SUCCESS HELPS EXPLAIN
SIMILARITIES
Behaviors
that contribute
to survival are found
throughout cultures
Why
are children often
afraid of the dark?
EVOLUTIONARY SUCCESS HELPS EXPLAIN
SIMILARITIES
OUTDATED TENDENCIES
Genetic
traits which helped our
ancestors survive may harm us
today
EXPERIENCE AND FACULTIES
Repeated experiences modify neural tissue. We
can change our brains! When is the brain’s
plasticity highest?
• Pruning
Courtesy of C. Brune
BRAIN DEVELOPMENT AND
ADULTHOOD
Brain development does not stop when we
reach adulthood. Throughout our life, brain
tissue continues to grow and change.
A well-learned finger-tapping task leads to
more motor cortical neurons (right) than baseline.
PEER INFLUENCE
In many ways, peers play a larger role than
parents in shaping our behavior. What causes
people to start smoking? Like a certain type of
music? Wear certain clothes? Talk the way they
talk?
Ole Graf/ zefa/ Corbis
AN EVOLUTIONARY EXPLANATION OF HUMAN
SEXUALITY
NATURAL SELECTION AND MATING
PREFERENCES
Differing
preferences in
partners
Male
preferences
Female
preferences
Men
tend to look for:
Physical
attractiveness and
a youthful appearance
A
man’s ideal women
would look like…
Women
tend to look for:
Maturity,
dominance,
status/affluence, and
boldness
So
a woman’s ideal
man would look like…
Characteristics
Preferred by Males
1. Kindness and
understanding
2. Intelligence
3. Physical attractiveness
4. Exciting personality
5. Good health
6. Adaptability
7. Creativity
8. Desire for children
9. College graduate
10. Good heredity
11. Good earning capacity
12. Good housekeeper
13. Religious orientation
Characteristics
Preferred by Females
1. Kindness and
understanding
2. Intelligence
3. Exciting personality
4. Good health
5. Adaptability
6. Physical attractiveness
7. Creativity
8. Good earning capacity
9. College graduate
10. Desire for children
11. Good heredity
12. Good housekeeper
13. Religious orientation
CRITIQUING THE EVOLUTIONARY
PERSPECTIVE
Backward
Impact
theorizing
of social influence
CULTURAL INFLUENCES
Humans have the ability to evolve culture.
Culture is composed of behaviors, ideas,
attitudes, values and traditions shared by a group.
VARIATION ACROSS CULTURE
Cultures differ. Each culture develops norms –
rules for accepted and expected behavior. Men
holding hands in Saudi Arabia is the norm (closer
personal space), but not in American culture.
Jason Reed/ Reuters/Corbis
VARIATION OVER TIME
Cultures change over time. The rate of this
change may be extremely fast. In many
Western countries, culture has rapidly changed
over the past 40 years or so.
This change cannot be attributed to changes in
the human gene pool because genes evolve
very slowly.
CULTURE AND THE SELF
If a culture nurtures an
individual’s personal
identity, it is said to be
individualist, but if a group
identity is favored then the
culture is described as
collectivist.
can benefit groups who
experience disasters such as
the 2005 earthquake in
Pakistan.
Kyodo News
A collectivist support system
GENDER DIFFERENCES IN
AGGRESSION
Men express themselves and behave
in more aggressive ways than do women.
This aggression gender gap appears
in many cultures and at various ages.
In males, the nature of this aggression
is physical. In the U.S. the male to female arrest
rate is 9 to 1. Men are more likely to support
war as a solution to international problems
GENDER AND SOCIAL POWER
In most societies, men are socially dominant
and are perceived as such.
In 2005, men accounted for 84% of the
governing parliaments.
GENDER DIFFERENCES AND
CONNECTEDNESS
Young and old, women form more connections
(friendships) with people than do men.
Men emphasize freedom and self-reliance.
Dex Image/ Getty Images
Oliver Eltinger/ Zefa/ Corbis
THE NEW FRONTIER: MOLECULAR
GENETICS
Molecular
genetics
Molecular
behavior
genetics
Genetics
and diseases
Genetics
and ethics
THE END
DEFINITIO
N SLIDES
= the study of the relative power and limits of genetic
and environmental influences on behavior.
BEHAVIOR GENETICS
= every non-genetic influence, from prenatal nutrition to
the people and things around us.
ENVIRONMENT
= threadlike structures made of DNA molecules that
contain the genes.
CHROMOSOMES
= a complex molecule containing the genetic information
that makes up the chromosomes.
DNA (DEOXYRIBONUCLEIC
ACID)
= the biochemical units of heredity that make up the
chromosomes; segments of DNA capable of
synthesizing a protein.
GENES
= the complete instructions for making an organism,
consisting of all the genetic material in that organism’s
chromosomes.
GENOME
= twins who develop from a single fertilized egg that
splits in two, creating two genetically identical
organisms.
IDENTICAL TWINS
= twins who develop from separate fertilized eggs. They
are genetically no closer than brothers and sisters,
but they share a fetal environment.
FRATERNAL TWINS
= the proportion of variation among individuals that we
can attribute to genes. The heritability of a trait may
vary, depending on the range of populations and
environments studied.
HERITABILITY
= the interplay that occurs when the effect of one factor
(such as environment) depends on another factor
(such as heredity).
INTERACTION
= the subfield of biology that studies the molecular
structure and function of genes.
MOLECULAR GENETICS
= the study of the evolution of behavior and the
mind,using principles of natural selection.
EVOLUTIONARY PSYCHOLOGY
= the principle that, among the range of inherited trait
variations, those that lead to increased reproduction
and survival will most likely be passed on to
succeeding generations.
NATURAL SELECTION
= the random error in gene replication that leads to a
change.
MUTATION