Download UNIT 3C: Biological Bases of Behavior – Genetics, Evolutionary

UNIT 3C: Biological Bases of Behavior – Genetics, Evolutionary Psychology, and Behavior
I.
II.
Overview
A.
Genes – nature
B.
Environments - nurture
Behavior Genetics: Predicting Individual Differences
A.
What are genes, and how do behavior geneticists explain our individual differences?
1.
Behavior geneticists study our differences and weigh the effects and interplay of heredity and
environment
2.
Example
a.
Jaden Agassi, son of tennis stars Andre Agassi and Stephanie Graf
b.
If he grows up to be a tennis star, is this due to genes that make him prone to tennis,
c.
Or is this due to growing up in a tennis-rich environment
B.
Genes: Our Codes for Life
1.
Every cell nucleus in the body contains the genetic master code for the entire body
2.
Analogy: Every room in the Pentagon had a book containing the architect’s plans for the
entire building
a.
Our book contains 46 chapters (23 donated from the egg; 23 donated from the
sperm)
b.
The 46 chapters are the chromosomes
c.
Each chromosomes has a coiled chain of the molecule DNA (deoxyribonucleic acid)
d.
The genes, small segments of the giant DNA molecules, form the words of those
chapters
e.
There are about 30,000 “gene words”
f.
Genes can either be active (expressed) or inactive
g.
Environmental events “turn on” genes (like hot water turning dry tea leaves into a tea
drink)
h.
When “turned on,” genes provide the code for creating protein molecules (the
building blocks of physical development)
3.
Sharing of 96% of DNA with chimpanzees
C.
Twin and Adoption Studies
1.
Identical Versus Fraternal Twins
a.
Identical twins
i.
Have the same egg and sperm
ii.
Usually share the same placenta
iii.
Most identical twins are black, then white, then Asian
b.
Fraternal twins
i.
Have different egg and sperm
ii.
Do not share placenta
iii.
Incidents of fraternal twins has increased with fertility drugs
c.
Findings
i.
Emotional stability is tied to genetics
ii.
Study done on identical twins and divorce rates
2.
Separated Twins
a.
Similarities are strong between identical twins raised apart
b.
Similarities are not as strong between fraternal twins, even those raised together
3.
Biological Versus Adoptive Relatives
a.
Environment shared by a family’s children has virtually no impact on their
personalities
b.
However, adoptive parents influence the child because they tend to be more giving
and are carefully screened
D.
Heritability
1.
What is heritability, and how does it relate to individuals and groups?
a.
III.
Heritability – the extent to which variation among individuals can be attributed to
their differing genes
b.
Cannot say what percentage of an individual’s personality or intelligence is inherited
c.
Heritability refers instead to the extent to which differences among people are
attributable to genes
d.
Explanation: Heritability increases the more SIMILAR the environment. If the
environment is VERY DIFFERENT, heritability decreases
2.
Group Differences
a.
Although genetic differences can dictate individual aggressiveness, the same cannot
be said of groups (sexes, races)
b.
Height and weight are highly heritable, but our height today has more to do with
nutrition
c.
Peaceable Scandinavians carry most of the same genes as their Viking warrior
ancestors
3.
Nature and Nurture
a.
Environment triggers a gene to respond
b.
Breast feeding triggers a gene (not present in all humans) that boosts intelligence
E.
Gene-Environment Interaction
1.
Genes and experience interact
a.
One baby is genetically predisposed to be attractive, sociable, and easy going
b.
Attracts more affection and stimulation
c.
In turn, he grows up to be more affectionate and sociable
2.
Environment triggers gene activity
3.
Humans select environments well suited to our natures
4.
Forget nature v. nurture; think instead nature via nurture
F.
The New Frontier: Molecular Genetics
1.
What is the promise of molecular genetics research?
a.
Specific genes influence behavior
b.
Find genes that trigger specific behavior
c.
Tests can reveal at-risk populations for many diseases
2.
Problems with molecular genetics research
a.
Screening for risks might lead to discrimination
b.
Screening for certain problems may eliminate the possibility of gifts in other areas:
Handel, van Gogh, Churchill, and Lincoln (all problematic people)
Evolutionary Psychology: Understanding Human Nature
A.
How do evolutionary psychologists use natural selection to explain behavior tendencies?
1.
Behavior geneticists explore the genetic and environmental roots of human differences
2.
Evolutionary psychologists instead focus mostly on what makes so much alike as humans
3.
Natural selection
a.
Organisms’ varied offspring compete for survival
b.
Certain biological and behavioral variations increase organisms’ reproductive and
survival chances in their particular environment
c.
Offspring that survive are more likely to pass their genes to ensuing generations
d.
Over time, the population characteristics may change
B.
Natural Selection and Adaptation
1.
Mutations – random errors in gene replication
2.
Genetic leash in humans is looser than in animals
3.
Genes selected during our ancestral history provide us with a great capacity to learn and
therefore to adapt to life in varied environments
4.
Genes and experience together wire the brain
5.
Fitness – our ability to survive and reproduce
C.
Evolutionary Success helps Explain Similarities
1.
Outdated Tendencies
a.
IV.
Stone Age ancestors loved the taste of sweets and fats, and these foods have led to
them being prepared during famines
b.
We no longer live in famine, but our genes crave sweets and fats, resulting in
obesity
2.
Evolutionary Psychology Today – questions …
a.
Phobias
b.
Sexuality
c.
Aggression
D.
An Evolutionary Explanation of Human Sexuality
1.
How might an evolutionary psychologist explain gender differences in sexuality and mating
preferences?
a.
Adaptive challenges that differ have led to the differences
b.
Focus – behaviors related to reproduction
2.
Gender Differences in Sexuality
a.
Males are morel likely than females to initiate sexual activity
b.
Men are more likely than women to attribute friendliness to sexual interest
3.
Natural Selection and Mating Preferences
a.
Women
i.
Pairing wisely – incubates and nurses one infant at a time
ii.
Attractive men – mature, dominant, bold, and affluent
b.
Men
i.
Pairing widely – spread genes to as many women as possible
ii.
Attractive women – young, waists are a 1/3 narrower than their hips (sign of
fertility, ages associated with fertility (young teens are attracted to slightly
older women)
E.
Critiquing the Evolutionary Perspective
1.
Often it starts with an effect and work backward – this can lead to problems in observation
2.
Social consequences
a.
Strikes at progressive efforts to remake society
b.
Undercuts moral responsibility
3.
We are not hard-wired; attraction varies with time and place
a.
Voluptuous women have been replaced with more athletic leaner women
b.
If socialized to value lifelong commitment, men may sexually bond with only one
woman
c.
If socialized to accept casual sex, women may willingly have sex with more than one
partner
4.
Sexes are far more alike than different
Reflections on Nature and Nurture
A.
Influences on individual development
1.
Biological
a.
Shared human genome
b.
Individual genetic variations
c.
Prenatal environment
d.
Sex-related genes, hormones, and physiology
2.
Psychological influences
a.
Gene-environment interaction
b.
Neurological effect of early experiences
c.
Responses evoked by our own personality, gender, etc.
d.
Beliefs, feelings, and expectations
3.
Social-cultural influences
a.
Parental influences
b.
Peer influences
c.
Cultural attitudes and norms
B.
Mind and brain are a holistic system
1.
Psychology is rooted in biology, which is rooted in chemistry, which is rooted in physics
2.
Yet psychology is more than applied physics
3.
How does a group of cells become consciousness?
4.
A brain simple enough to be understood is too simple to produce a mind able to understand it