Chapter 4: Nature, Nurture, and Human Diversity

Chapter 4: Nature, Nurture, and Human Diversity
I. Introduction
What makes you, you?
Is who we are the result of our genes (nature) or is it the result of our upbringing (nurture)?
Nature: the result of our genes
Nurture: everything else other than genes, the culture you were brought up in, the country and family you were brought up in, the school you went to
There is an interaction between nature and nurture
II. The Nature Component
A. Genes: Our biological blueprint

Our body is made up of millions of cells, in every cell, except egg and sperm, we have 46 chromosomes, 23 pairs
We have thousands of genes, which are considered to be the basic unit of heredity
Genes are segments of DNA that carry the instruction that give an organism its traits or characteristics
Different size of animals and people depends on a single gene (chromosome 15)
Sometimes multiple genes (gene complexes) are responsible for something such as obesity
Genes are made up of nucleotides
There are four nucleotides: Adenine, Guanine, Thymine, Cytosine - They always come in pairs, A with T and G with C
The sequence determine what a gene will do and what it will not do
Changing just one letter in a sequence changes what the gene does
Common analogy: chromosomes are like books, genes are the words in a book, and nucleotides are the letters in a book
Human genome: we have roughly 30 thousand genes in our DNA
They discovered based on the mapping of the human genome that every human on earth is 99.99% genetically similar to every other human being on earth
Repartition of the0.01% difference: 5% difference among races, 95% differences within a race
Nature genetics, 2004: race does NOT exist biologically; there is no white, black, Arab, Asian race, and it is just a social concept
We share: 95-98% of our DNA with chimps, 90% of our DNA with mice, 50% of our DNA with bananas, 44% of our DNA with fruit flies

B. Evolutionary Psychology

B1. What is Evolutionary Psychology (EP)?

Newest perspective in psychology, heavily influenced by Darwin's principals of the Theory of Evolution
According to Darwin, the main goal is to survive and to transmit our genes into the future, although not every organism that is born will survive (natural selection); many organisms die out due to survival of the fittest
Survival of the Fittest: when there is a match between characteristics of organism and demands of the environment
Evolutionary psychologists took the theories of Darwin to explain human behaviour; they study behaviours that are universal and common to all human beings; they study adaptive behaviours (adaptation is essential for survival)
Any behaviours, traits, or emotions that our ancestors had are what we see in humans today
We are in the post-antibiotic era, bacteria are smart B2. Application of EP to Sexuality
Surveys: men think more about sex, masturbate more, want sex more than women, are more likely to interpret friendliness as a come-on, and are more likely to make sacrifices for sex
Clark and Hatfield (1978): recruited average-looking men and women to go around campus saying: "Hey, I've noticed you around campus, want to go to bed tonight?"
Different attitudes about sex: majority of women were offended, majority of men would say yes or "why wait till tonight?"
According to EP: both men and women have the same goal, but have different strategies to achieve the goal due to physiological differences
It takes women 9 months to produce a baby, so relational sex enhances survival; it doesn't take men long to plant their seeds, so recreational sex is best strategy B3. Critique of EP
Professor's Critique: this is offensive because most men, like most women, want to be in healthy relationships
There are at least 18 societies today that encourage women to have multiple partners because they believe that a child can have multiple fathers (women in these societies are less likely to have a miscarriage, women with multiple partners were more likely to have children that made it to age of 15 years)
How evolutionary psychologists explain gender differences in sexuality: EPs theorize that women have inherited their ancestors' tendencies to be more sexually cautious because of the challenges associated with incubating and nurturing offspring, whereas men inherited an inclination to be more casual about sex because their act of fathering requires a smaller investment
Three main criticisms of the evolutionary explanation of human sexuality: (1) it starts with an effect and works backward to propose an explanation, (2) unethical and immoral men could use such explanations to rationalize their behaviour toward women (3) this explanation may overlook the effects of cultural expectations and socialization

C. Behaviour Genetics C1. Introduction
Behaviour genetics: a field of study where the main goal and purpose is to determine the extent to which differences between individuals are due to genetics; BGs are interested in INDIVIDUAL DIFFERENCES
Why we differ and how genes affected this: see below C2. Twin Studies
Monozygotic (Identical) Twins: one sperm fertilizes one egg and then the egg splits, always the same gender, and 100% genetically similar
Dizygotic (Fraternal) Twins: two different eggs fertilized by two different sperms, can be same or opposite sex, 50% genetically similar
Rationale: if a trait or behaviour has a genetic component to it, identical twins should be more similar on this trait than fraternal twins
1 identical twin has Alzheimer's, other twin has 60% chance
1 fraternal twin has Alzheimer's, other twin has 30% chance
1 identical twin divorces, other has 5.5% chance
1 fraternal twin divorces, other has 1.6% chance studies find that identical twins are more similar than fraternal twins in extraversion (outgoingness) and neuroticism (emotional instability)
MAKE LIST OF GENETIC COMPONENTS AND OTHER COMPONENTS
Genetic components: extraversion, neuroticism, agreeableness, personality traits, temperament (emotional excitability)
Other components: attitudes, values, manners, faith, politics
Criticism: these twins have similar environments, they come into this world at the same time, are exposed to the same things, same home, same school, maybe this is why they are similar
Solution: started studying twins who were separated and reared apart; identical twins who are reared apart are more similar than fraternal twins who are reared apart
Bouchard et Al.,: studied over 100 twins, results indicate that for certain traits there is a genetic component
Conclusion: identical twins reared together are more similar to each other than identical twins reared apart; identical twins are more similar to each other (reared together or apart) than fraternal twins (reared together or apart) C3. Adoption Studies
Rationale: we have one adopted child with two sets of parents - biological and adoptive parents
Clear evidence to indicate that adopted children, when it comes to personality, are more similar to their biological parents, even if they have never met them, than they are to their adoptive parents (personality has a strong biological component)
CREATE TWO COLUMNS: BIOLOGICAL PARENTS VS. ADOPTIVE PARENTS
Genetic components: extraversion, neuroticism, agreeableness, personality traits, temperament (emotional excitability)
Other components: attitudes, values, manners, faith, politics C4. Family Studies
Rationale: family members are more genetically similar to each other than strangers, if a trait has a genetic component to it then family members should be more similar on that trait than strangers are
Within a family we have different degrees of genetics, therefore if a trait has a genetic component to it, then family members who are ore similar to each other genetically should be more like each other then family members who are less genetically similar to each other
Regular siblings: 50%
Parents and children: 50%
Grandparents and grandchildren: 25%
1st cousins: 12.5% C5. Temperament Studies
Definition: a temperament is your typical emotional reactivity (the way you respond to life) and the typical intensity of that response.
Do you respond with fear and anxiety? Or are you excited and bold? Or are you shy?
Temperament is a component of personality, has a genetic component
Babies come to this world equipped with a temper; four different types of temperaments:
Easy babies (40%): positive emotions, easy to sooth, regular and predictable patterns of eating, sleeping, and eliminating
Slow-to-warm babies (15%): shy, guarded in their expression, takes the awhile to adapt to new environments and strangers
Difficult babies (10%): strong emotional reactions, fussy, cry a lot, patterns are unpredictable and irregular, not easy to soothe
Physiological studies show that difficult babies have a more "revved up"/aroused nervous system
Combination babies (35%): sometimes easy, sometimes difficult, sometimes shy, sometimes bold
Twin studies indicate that identical twins are more similar in their temperament than fraternal twins
Temperament seems to endure, and stay stable throughout time
Through nurture we can modify and reshape temperament; parenting does make a difference C6. Heritability
Definition: the percentage of variation within a given population that is due to heredity (the degree to which differences between/amongst individuals are due to genetics) h2 = heritability coefficient (heritability can be quantified by a heritability coefficient) h2 = VARIANCEgenes / (VARIANCEgenes + VARIANCEenvironment) h2 varies between 0 and 1
If h2 = 0.0 -> no genetic influence
If h2 = 1.0 -> all variance is due to genetic influence
If h2 = 0.4 -> 40% genes (60% environment) if h2 = 0.6 -> 60% genes (40% environment)
Points to know and remember about heritability:
Sometimes for the same trait, different studies come up with a different h2 (due to environment)
When environment is similar, h2 will be higher
When environment is different, h2 will be lower
Just because individual differences are heritable, it does NOT necessarily mean that differences between races, gender, generations are heritable C7. Nature and Nurture Interaction
Just because you have inherited a gene does not mean that this gene is going to affect you, this gene may remain dormant for the rest of your life, genes MAY need the environment to turn them on, this is not always the case
Self-regulating: the same gene will act differently in a different environment
Both male and female rats have a gene that makes them very nurturing and loving towards baby rats, however this does not turn on till they can hear, see, and smell the baby rat
We don't just transmit genes to our offspring, we transmit the pattern of activation as well
The environment is one of the most important factors influencing gene
Genome
Epigenome: tells a genome to activate/turn on/turn off
Methyl groups: chemicals that, when present, inactivate/silence a gene
Acetyl groups: tell the gene to turn on, express itself
Epigenetics (simplified definition): study the factors that influence/affect gene expression with affecting DNA
Epigenetics studies the molecular mechanisms by which environments trigger genetic expression; study of environmental factors that affect how our genes are expressed (life experiences beginning in the womb lay down epigenetic marks, organic methyl molecules, that can block the expression of any gene in the associated DNA segment)
D. Behaviour Genetics
Definition: a field of research where scientists are trying to identify the genes responsible for characteristics, illness, and traits.
How they do it: If a family is prone to heart disease and everyone has heart disease except for a few people, study one person who has it and one person who doesn't; find the gene that varies and you'll know which gene is responsible for high cholesterol and heart disease.
Relevance to psychology: we study both mental illness and mental health and part of helping people become healthy is knowing which genes we need to fix; intervention, prevention, therapy.
Promises and dangers: dangers if employers can tell that you have heart disease or something they may fire you, if parents can tell their baby is going to have a problem they may abort it; promises they can go into the chromosome and snip the gene that is problematic.
Midterm Question
Use one of the principles of evolutionary psychology to answer the following question: Each one of us has 4 grandparents. Using the principles of evolutionary psychology which one of those grandparents is going to spend the most time, money, energy and resources on you.
III. The Nature Component
A. Prenatal Development
The baby in the womb is very well protected, however this protection is not 100%, the baby remains vulnerable in the womb because lots of germs and infections can pass through the placenta; this baby can be harmed due to mother's environment (living near a nuclear plant) or mother's diet (the food she is eating).
Even though twins, identical and fraternal, share the same womb, they may not be sharing the same environment.
Example: one twin may be getting the better nutrition, better protection from viruses, better blood and oxygen supply.
Fraternal twins have different placentas, identical twins can have the same or different placentas; identical twins with different placentas are less similar to each other than identical twins who share the same placenta.
Marked for life (?): what happens in the womb can influence and effect our life later on; cancer, blood pressure and heart diseases all could have been rooted in nutrition of the mother when she was pregnant.
Two twins in the womb touch each other and are aware of each other's presence, this brings up the question of "when does awareness begin?"
B. Experience and Brain Development B1. Experience Facilitates Brain Development
Nurture is essential and vital for proper brain development
They need stimulation, proper nurture, to hear sounds and feel touch for proper brain development B2. Experience Changes the Brain
For the longest time researchers believed that when the brain reaches maturity it will stay the same until it gets hit by diseases and begins to deteriorate
However, we learned that even after the brain reaches maturity it continues to change through experience; learning new skills could cause your brain to change for the better: if you start taking new drugs and are always stressed that will change the brain for the worse
They took a bunch of rats and treated them the same until they were 70, then they divided them into two groups: poor rats and rich rats; the poor rats were stuck in a cage and just given food and water, the rich rats were given food, water, big cages, freedom to interact with each other, new toys to explore all the time; at 90 they killed the rats and studied the brains, realizing the rich rats' brains developed more.
C. How Much Credit or Blame do Parents Deserve?
Parenting does matter, as is evident at the extremes: abused children who become abusive, neglected children who become neglectful, etc.
In personality measures, shared environmental influences from the womb onward typically account for less than 10% of children's differences; two children are (apart from their shared genes) as different as two random children.
Parents should be given less credit for kids who turn out great and blamed less for kids who don't; children are not easily sculpted by parental nurture.
D. Peer Influence
Definition: individuals who are the same age or have the same level of maturity as us
It is clear to researchers that peers are important to one's life (peers go all the way back to infancy)
If one does not have peers, they create imaginary ones because peers are needed
Children who are bullied or rejected by their peers end up being depressed and may kill themselves in the future
As we age we interact with peers more and more; growing interaction with friends leads to growing influence by peers such as music taste, the way you dress
Peers and risk-taking behaviour: children and young teenagers are more likely to have risk-taking behaviour when their peers also take risks or if they think their peers are taking risks; is it selection of friends?
Parents also influence us
Lifestyle choices: your parents choose what neighbourhood you live in, what school they put you in
The quality of parent-child interaction influences and effects the quality of peer-child interaction; for example, boys who bully others are more likely to have parents who are aggressive and dominate them, boys who get bullied are more likely to have parents who are overbearing and protective of them
Advice: you are affected by the advice parents give you about relationships, life, or anything else
Bottom line: parents and peers both influence you by distinct and complementary
MAKE A CHART: PARENTS' INFLUENCE VS. PEER INFLUENCE
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E. Culture
Definition: the enduring behaviours, ideas, attitudes, values, and traditions shared by a group of people and transmitted from one generation to the next
Norm: an understood rule for accepted and expected behaviour; norms prescribe "proper" behaviour
When we don't understand what's accepted or expected, we may experience culture shock; two great culture shocks are the differing pace of life and people's differing senses of punctuality
Cultures vary and compete for resources, and thus evolve over time; many changes have occurred since 1960
There have been positive changes (middle-class people travel more, eat out more, women have economic independence) and negative changes (increase in divorce, depression, and work hours); we cannot explain these rapid culture changes by changes in the human gene pool; cultures vary, change, and shape our lives
Individualism: giving priority to one's own goals over group goals and defining one's identity in terms of personal attributes rather than group identifications; behaviour reflects one's personality and attitudes, confrontation acceptable
Collectivism: giving priority to the goals of one's group (often one's extended family or work group) and defining one's identity accordingly; behaviour reflects social norms and roles, harmony valued
IV. The Nature and Nurture of Gender
CREATE A COLUMN FOR MEN AND WOMEN AND COMPARE
(Not on first midterm, but definitely on final exam)
Men
Women
Tend to feel better about their appearance
Four times more likely to commit suicide or suffer alcohol dependence
More often diagnosed with colour-blindness, autism, attentio-deficit hyperactivity disorder (as children), and antisocial personality disorder (as adults)
In surveys, men admit to more (direct, physical) aggression than do women
Male-to-female arrest ratio for murder is 9 to 1 in the United States and 8 to 1 in Canada
Express more support for war (hunting, fighting, and warring are primarily men's activities)
Perceived as being more dominant, forceful, and independent (place more importance on power and achievement)
Tend to be more direct, even autocratic
Talk assertively, interrupt, initiate touches, stare more, smile less, apologize less
Boys typically play in large groups with an activity focus and little intimate discussion
Male answer syndrome: men are more likely than women to hazard answers rather than admit they don't know
Part of the parietal cortex (key area for space perception) is thicker in men
Tend to feel better about their behaviour and ethics
The average woman enters puberty two years earlier, lives five years longer, carries 70 percent more fat, has 40 percent less muscle, and is 5 inches shorter
Can become sexually re-aroused immediately after orgasm
Smell fainter odours
Express emotions more freely
Offered help more often
Doubly vulnerable to depression and anxiety, risk of developing eating disorders is 10 times greater
Women are perceived as being more deferential, nurturant, and affiliative
Tend to be more democratic, more welcoming of subordinates' input in decision making
Girls usually play in smaller groups, often with one friend (play is less competitive than boys' and more imitative of social relationships)
Females are more open and responsive to feedback than are males
Females are more interdependent than males
Women are more likely to tend and befriend (are more open with each other, desire intimacy)
Parts of the frontal lobe (involved in verbal fluency) are reportedly thicker in women

Gender similarities and differences
2 of the 46 chromosomes are sex chromosomes; these sex chromosomes determine whether a baby is genetically male or female
The major sex chromosomes are X and Y; mother always contributes an X, father can contribute an X or Y (if he contributes a Y the baby is male, X the baby is female)
If the baby only ends up with one chromosome and it is an X the baby can survive but will have trouble later in life; if the baby only ends up with a Y it cannot survive and is terminated immediately in the womb
There is a gene on chromosome Y called TDF that kicks in at 7 months in the womb, forming testes and testosterone (for female babies the absence of testosterone leads to the development of female body parts)
Hormones influence and effect behaviour
Female rats or monkeys: if injected with testosterone when they are pregnant the female babies behave like the males of the species, going after women and being more aggressive
Human cases: the girls are more tomboyish, they don't like jewellery and dolls, they like guns and like to play war; the bodies of men who are genetically male produce testosterone but their cells don't respond to testosterone, so their bodies don't develop male genetilia and they become more like girls
Normal hormone levels = average women
Higher levels of progesterone = more feminine
Higher levels of testosterone = more masculine
The role of culture and society
Parents describe their baby girl as being delicate, little, sweet; they describe baby boys as being firm, strong, and well-coordinated
Medically, there are not differences in strength, alertness, and coordination between baby boys and girls
Study: a baby boy was dressed in pink (parents held the baby for a long time, walked and rocked the baby, gave the baby teddy bears and bunnies to play with, cooed the baby) then the baby was dressed in blue (parents gave the baby a truck and hammer to play with, held the baby for a bit, then put him on the floor and encouraged him to start to crawl).
Gender identity: a strong sense of being male or female
Gender roles: expectations from society linked and associated with being a male or female; these gender roles vary from one culture to the next
Gender typed: adopting a traditional masculine role or a traditional feminine roll
There are many theories in psychology attempting to explain gender
Social learning theory: we learn about a gender through observation, we learn through modelling, we have a role model and we imitate that role model, we learn through observation, modeling, rewarding and punishing
Gender schema theory: they do accept what social learning theory is, saying yes there is observation, modeling, rewarding and punishing, but they take it several steps further; children are not learning passively, rather they are actively taking this information, drawing conclusions about this information, and they organize it into boys, girls, men, and women; those schemes become a rule in their life (boys do not play with Barbies, I am a boy and I cannot play with Barbies)
Schema: a mental model
V. Reflections