Transcript Chapter Four Part One - K-Dub

General
Psychology
Scripture
• Matthew 5:9
Blessed are the peacemakers, for they will be
called children of God. .
Those who strive to prevent contention, and strife,
and war. Who use their influence to reconcile
opposing parties, and to prevent hostilities, in
families and neighborhoods. Every man may do
something of this; and no man is more like God
than he who does it.
Thanks for Everything Dad
Overview:
Nature/Nurture/Diversity Questions
 How do we explain traits that all humans may
have in common?
 How do we explain the origins of diversity,
the source of differences in the traits:
• between genders?
• among cultures?
• among individuals?
 But first, how do we investigate these issues?
Behavior Genetics:
Predicting Individual Differences
The topics in the text:
1. genes
2. twin and adoption
studies
3. temperament and
heredity
4. molecular genetics
5. heritability
6. gene/environment
interaction
Behavior geneticists
study how heredity
and environment
contribute to human
differences.
Let’s start by looking
at GENES.
GENES:
The Building Blocks of
Heredity and
Development
Genes are
parts of DNA
molecules,
which are
found in
chromosomes
in the nuclei of
cells.
DNA
(Deoxyribonucleic Acid)
Chromosomes are made of DNA,
which are made of genes.
Chromosome:
threadlike structure
made largely of DNA
molecules
DNA:
a spiraling, complex
molecule containing
genes
}
Chromosomes and Inheritance
 The human genome includes 46
chromosomes in 23 sets
matched sets; each
chromosome has the same
gene locations.
 This includes the X and Y
chromosomes, not a matched
set in males, who are missing
some genes on the Y.
 A biological parent donates half
his/her set of chromosomes to
his/her offspring.
 We received half a set of
chromosomes from each
biological parent.
The Human Genome:
20,000 to 25,000 Genes
 Human genomes are so nearly
identical that we can speak of one
universal human genome.
 Yet tiny genetic differences make a
difference. If there is a:
 .001 percent difference in
genome, your DNA would not
match the crime scene/you are
not the baby’s father.
 0.5 to 4 percent difference in
genome, you may be a
chimpanzee.
 50 percent difference in
genome, you may be a banana.
The genome: an
organism’s entire
collection of genes
How Genes Work
 Genes are not blueprints;
they are molecules.
 These molecules have the
ability to direct the
assembly of proteins that
build the body.
 This genetic protein
assembly can be turned on
and off by the
environment, or by other
genes.
 Any trait we see is a result
of the complex interactions
of many genes and
countless other molecules.
Next step for behavior geneticists:
Controlling Variables
Can we design an
experiment to keep genes
constant and vary the
environment and see what
happens?
Or vary the genes in the
same environment?
Fraternal and Identical Twins
Fraternal “twins” from separate
eggs are not any more genetically
alike than other siblings.
Identical twin: Same sex only
Fraternal twin: Same or opposite sex
Twin and
Adoption Studies
To assess the
impact of nature
and nurture, how
do we examine
how genes make a
difference within
the same
environment?
 study traits of
siblings vs.
identical twins
 see if the
siblings vary
more than
twins
Identical vs. Fraternal Twins
Studies of twins in adulthood
show that identical twins are
more alike than fraternal twins in:
 personality traits such as
extraversion (sociability) and
neuroticism (emotional
instability).
 behaviors/outcomes such as
the rate of divorce.
 abilities such as overall
Intelligence test scores.
Twin and
Adoption Studies
How do we find
out how the same
genes express
themselves in
different
environments?
We can study the
traits of identical
twins as they grow
up, or if they were
raised separately
(e.g., the
Minnesota Twin
Family Study).
Studies of Identical Twins Raised Apart
Critiques of Twin Studies
Similarities found in
identical twins despite 1. In the more recent years of the
Minnesota Twin Family Study, twins
being raised in
have known about each other and
different homes:
may influence each other to be more
similar.
 personality, styles of
happen; some
thinking and relating 2. Coincidences
randomly chosen pairs of people will
have similar traits, including even
 abilities/intelligence
spouses, children, and dogs with
test scores
identical names.
 attitudes
3. Environments may be similar;
adoptive families tend to be more
 interests, tastes
similar than randomly selected
families in education, income, and
 specific fears
values.
 brain waves, heart
BUT none of these factors explains,
better than the genetic explanation,
rate
why fraternal twins have more
differences than identical twins.
Searching for Parenting Effects:
Biological vs. Adoptive Relatives
Studies have been performed with adopted children for
whom the biological relatives are known.
Findings: Adopted children seem to be more similar to
their genetic relatives than their environmental/nurture
relatives.
Given the evidence of genetic impact
on how a person turns out,
does parenting/nurture
make any difference?
Does the home environment have
any impact?
Parenting Does Matter
Despite the strong impact of
genetics on personality,
parenting has an influence on:
 religious beliefs
 values
 manners
 attitudes
 politics
 habits
If parenting has an influence,
why are siblings so different?
 Siblings only share
half their genes.
 Genetic differences
become amplified as
people react to them
differently.
 Siblings are raised in
slightly different
families; the youngest
has more older
siblings and has older
(wiser? more tired?)
parents.
Temperament is another difference
not caused by parenting.
 From infancy into adulthood,
most people do not seem to
change temperament (defined
as a person’s general level and
style of emotional reactivity).
 According to some researchers,
three general types of
temperament appear in infancy:
• “easy”
• “difficult”
• “slow to warm up”
Molecular Genetics
 Molecular genetics is the study of the molecular
structure and function of genes.
 Molecular genetics might help us see exactly
how specific genes have an influence on
behavior.
 Genetic tests can reveal which people are at risk
for many physical diseases, and may soon
identify people at risk of mental health
disorders.
 Ethical conundrum: should people use genetic
tests to select sperm, eggs, and even embryos?
Heritability
 When you see a variation
of some trait within a
population, the
heritability of that trait is
the amount of variation
in the population that is
explained by genetic
factors.
 This DOES NOT tell us
the proportion that
genes contribute to the
trait for any one person.
 The heritability of a trait
also does not tell us
whether genetics explain
differences between
groups/populations.
Clarifying Heritability
 If five unrelated people
had nearly identical
upbringing, but differed
in a trait such as shyness,
then the heritability of
this trait for them is
close to 100 percent.
 Nurture may have
influenced how shy they
are, but because it
influenced them all in
the same way, any
differences are almost
certainly caused by
genes.
Nature and nurture working together
Interaction of Genes and Environment
 Some traits, such as the overall design of our bodies, are set by
genes.
 Other traits, such as physical and mental abilities, develop in
response to experience.
How does the interaction of genes and environment work?
 Genetic traits influence the social environment, which in turn
affects behavior.
Evolutionary Psychology:
Natural Selection: How it Works
Begin with a
species’ genome,
which contains a
variety of versions
of genes that
shape traits.
Conditions make it
difficult for
individuals with
some traits (some
versions of those
genes) to survive
long enough to
reproduce.
Other individuals
thus have their
traits and genes
“selected” to
spread in the
population.