Psychology Chapter 4: Nature, Nurture, and Human Diversity

Identical Twins Qualifications

- Although identical twins have the same genes, they do not always have the same number of copies of those genes. That helps explain why one twin may be more at risk for certain illnesses. - Most identical twins share a placenta during prenatal development, but one of every three sets has two separate placentas. One twins placenta may provide slightly better nourishment, which may contribute to identical twin differences.

Persistent Temperaments of Infants

- The most emotionally creative newborns tend also to be most reactive 9-month-olds. - Exceptionally inhibited and fearful 2 year olds are still relatively shy as 8-year olds; about half will become introverted adolescents. - The most emotionally intense preschoolers tend to be relatively intense young adults. In one study of more than 900 New Zealanders, emotionally reactive and impulsive 3-year olds developed into somewhat more impulsive, aggressive and conflict-prone 21-year olds.

What are the 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 towards women. 3. This explanation may overlook the effects of cultural expectations and socialization.

Family-Self

A feeling that what shames the child shames the family, and what brings honour to the family brings honour to the self.

Mutation

A random error in gene replication that leads to change.

Chromosomes

Composed of a coiled chain of the molecule DNA (deoxyribonucleic acid).

More twins

Curiously, twinning rates vary by race. The rate among Caucasians is roughly twice that of asians and half that of africans. In Africa and Asia, most twins are identical. In western countries, most twins are fraternal, and fraternal twins are increasing with the use of fertility drugs.

Evolutionary Psychology Today

Darwin's theory of evolution has been an organizing principle for biology for a long time. Today, Darwin's theory lives on in the second Darwinian Revolution: the application of evolutionary principles to society.

Natural Selection and Adaption

Over time, traits that are selected confer a reproductive advantage on an inducible or species and will prevail. Animal breeding experiments manipulate genetic expression and show its power. Nature has indeed selected advantageous variations from the new gene combinations produced at each human conception and the mutations that sometimes result. The genes selected during our ancestral history endow us with a great capacity to learn and therefore adapt to life in varied environments. Genes and experience work together to wire our brain. Our adaptive flexibility in responding to different environments contributes to our fitness; our ability to survive and reproduce.

Aggression

Physical or verbal behaviour intended to hurt someone.

Identical vs. Fraternal Twin Behaviours

Studies of thousands of twin pairs find that on both extraversion (outgoingness) and neuroticism (emotional instability), identical twins are much more similar than fraternal.

Experience and Development

We are formed by nature and nurture. The formative nurture that conspires with the nature begins at conception, with the prenatal environment in the womb, as embryos receive differing nutrition and varying levels of exposure to toxic agents. Nurture then continues outside the womb, where our early experiences foster brain development.

Culture Shock

When we don't understand whats expected or accepted, we experience a culture shock.

Gender and Social Connectedness

A gender difference in social connectedness surfaces early in childrens play. Boys typically play in large groups with an activity focus and little intimate discussion. Girls usually play in smaller groups, often with one friend. Their play is less competitive and more imitative of social relationships. Both in play and other settings, females are more open and responsive to feedback than are males. Females are more interdependent than males. As teens, girls spend more time with friends and less time alone. As adolescents, they spend more time on social networking sites. As adults, women take more pleasure in talking face to face and tend to use conversation more to explore relationships. These gender differences are sometimes reflected in patterns of phone-based communication.

Role

A set of expectations (norms) about a social position, defining how those in the position out to behave.

Gender Role

A set of expected behaviours for males or females.

A trained brain

A well learned finger tapping task activates more motor cortex neurons than were active in the same brain before training.

Humans vs. Chimpanzees

Actually we aren't that different from our chimpanzee cousins; with them we shared about 96% of our DNA sequence. At "functionally important" DNA sites, reported one molecular genetics team, the human-chimpanzee DNA similarity is 99.4%. Yet, that wee difference matters. Despite some remarkable abilities, chimpanzees grunt. Small differences matter among chimpanzees, too. Two species, common chimpanzees and baboons, differ much less than by 1% of their genomes, yet they display markedly differing behaviours. Chimpanzees are aggressive and male dominated. Baboons are peaceable and female led.

What is the selection effect and how might it affect a teen's decision to join sports teams at school?

Adolescents tend to select out similar others and sort themselves into like-minded groups. This could lead to a teen who is athletic finding other athletic teens and joining school teams together.

Prenatal Screening

Aided by inexpensive DNA-scanning techniques, medical personnel are becoming able to give would-be parents a readout on how their fetus's genes differ from the normal pattern and what this might mean. With this benefit come risks. Might labelling a fetus "at risk for learning disorder" lead to discrimination? Prenatal screening poses ethical dilemmas. In China and India, where boys are highly valued, testing for an offsprings sex has enabled selective abortions resulting in millions of "missing women".

Gene-Environment Interactions

Among our similarities, the most important- the behavioural hallmark of our species- is our enormous adaptive capacity. Some human traits, such as having two eyes, develop the same in virtually every environment. But other traits are expressed only in particular environments. Go barefoot for summer and you will develop toughened, callused feet, a biological adaption to friction. Meanwhile, your shod neighbour will remain a tenderfoot. The difference between the two of you is, of course, an effect of environment. But it is also the product of a biological mechanism- adaption. Our shared biology enables our developed diversity.

Gender Similarities and Differences

Among your 46 chromosomes, 45 are unisex. Compared with the average man, the average woman enters puberty sooner, five years longer, carries 70 percent more fat, has 40 percent less muscle, and is 5 inches shorter. Women and doubly more vulnerable to depression and anxiety, and their risk for developing eating disorders is 10 times greater. But then men are some four times more likely to commit suicide or exhibit alcohol use disorder. They are far more often diagnosed with autism, colour blindness, ADD/ADHD, and anti-social personality disorder as adults.

Transgender

An umbrella term describing people whose gender identity or expression differs from that associated with that of their birth sex.

Norm

An understood rule for accepted and expected behaviour. Norms prescribe proper behaviour.

Peer Influence

At all ages, but especially during childhood and adolescence, we seek to fit in with our groups and are influenced by them. - Preschoolers who disdain a certain food often eat that food if put at a table with a group of children who like it. - Children who hear english spoken with one accent at home and another at the neighbourhood and school will invariably adopt the accent of their peers, not their parents. Accents (and slangs) reflect culture, and children get their culture from their peers. -Teens who start smoking typically have friends who model smoking, suggests its pleasures, and offer and cigarette. Part of this peer similarity may result from the selection effect, as kids seek out peers with similar attitudes and interests. Those who smoke (or don't) may select friends who also smoke (or don't).

Our codes for Life

Behind the story of our body and our brain is the hereditary that interacts with our experience to create both our universal human nature and our individual and social diversity. Barely more than a century ago, few would have guessed that every cell nucleus in your body contains the genetic master code for your entire body. The plans for your own book of life run to 46 chapters-23 donated by your mothers egg and 23 by your fathers sperm. Each of these 46 chapters, called a chromosome.

Culture and Child-Rearing

Child-rearing practices reflect cultural values that vary across time and place. Such diversity in child-rearing cautions us against presuming that our cultures way is the only way to rear children successfully.

Gender Differences in Sexuality

Consider men's and women's sex drives. Males are more likely than females to initiate sexual activity. This is the largest gender difference in sexuality, but there are others. Casual, impulsive sex is more frequent in males with traditional masculine attitudes. In surveys, gay men (like straight men) report more interest in uncommitted sex, more responsiveness to visual stimuli, and more concern with their partners physical attractiveness than do Lesbian women. Gay male couples also report having sex more often than do lesbian couples. Although men are roughly two-thirds of the gay population, they were only about one-third of those electing legal male partnership. Men also have a lower threshold for perceiving warm responses as a sexual come on. Men more often than women attribute a women's friendliness to sexual interest. Misattributing women's cordiality as a come on helps explain, but does not excuse, mens greater sexual assertiveness. The unfortunate result can range from sexual harassment to date rape.

Natural selection and mating preferences

Evolutionary psychologists use natural selection to explain why, worldwide, women's approach to sex is usually more relational, and mens more recreational. While women usually incubates and nurses one infant at a time, a male can spread his genes to other females. Our natural yearnings are our genes way of reproducing themselves. In our ancestral history, women most often sent their genes into the future by pairing wisely, men by paring widely.

Behaviour Genetics

Explore the genetic and environmental roots of human differences.

Identical Twins

Develop from a single (monozygotic) fertilized egg that splits in two. Thus, they are genetically identical-natures own human clones. Indeed, they are clones that not only share the same genes but the same conception and uterus, and usually the same birth date and cultural history with two slight qualifications.

Fraternal Twins

Develop from separate (dizygotic) fertilized eggs. As womb-mates, they share a fetal environment, but they are genetically no more similar than ordinary brothers and sisters.

Epigenetic Molecules

Environmental factors such as diet, drugs, and stress can affect the epigenetic molecules that regulate gene expression. Humans who have committed suicide exhibit the same epigenetic effect if they had suffered a history of child abuse. Researchers now wonder if epigenetics might help solve some scientific mysteries, such as why only one member of an identical twin may develop a genetically influenced mental disorder, and how experience leaves its fingerprints in our brains. So, from conception onward, we are the product of a cascade of interactions between our genetic predispositions and our surrounding environments. Our genes effect how people react to and influence us. Biological appearances have social consequences.

Environment

Every non-genetic influence; from prenatal nutrition to the people and things around us.

How do evolutionary psychologists explain gender differences in sexuality?

Evolutionary psychologists theorize that women have inherited their ancestors tendencies to be more cautious, sexually, because of the challenges associated with incubating and nurturing offspring. Men have inherited an inclination to be more casual about sex, because their fathering requires a smaller investment.

Collectivism

Giving priority to the goals of one's group (often one's extended family or work group) and defining one's identity accordingly.

Evolutionary Psychologists

Focus mostly on what makes us so much alike as humans. They use Charles Darwins principle of natural selection to understand the roots of behaviour and mental processes.

Biological versus Adoptive Relatives

For behaviour geneticists, natures second real like experiment, adoption, creates two groups: genetic relatives (biological parents and siblings) and environmental relatives (adoptive parents and siblings). For any given trait, we can therefore ask if adoptive children are more like their biological parents, who contribute their genes, or their adoptive parents who contribute a hime environment. While sharing that home environment, do adopted siblings also come to share traits. The stunning finding from studies of hundreds of adoptive families is that people who grew up together, whether biologically related or not, do not much resemble one another in personality. In such traits such as extraversion and agreeableness, adoptees are more similar to their biological parents than to their caregiving adoptive parents.

Gender Differences in Social Connectedness

Gender differences in social connectedness, power and other traits peak in late adolescents and early adulthood. As teenagers, girls become progressively less assertive and more flirtatious; boys become more domineering and unexpressive.

Genes and environment/Nature and Nurture

Genes and environment- nature and nurture- work together like two hands clapping. Genes are self-regulating. Rather than acting as blueprints that lead to the same result no matter the context, genes react. An african butterfly that is green in the summer turns brown in the fall, thanks to the temperature controlled genetic switch. The genes that produce brown in one situation produce green in another. So, too, people with identical genes but with differing experiences will have similar but not identical minds. One twin may fall in love with someone quite different from the co-twins love.

Genetic Tests

Genetic tests can now reveal at-risk populations for many dozens of diseases. The search continues in labs worldwide, where molecular geneticists are teaming with psychologists to pinpoint genes that put people at risk for such genetically influenced disorders as specific learn disorder, depression, schizophrenia, and alcohol use disorder. To tease out the implicated genes, molecular behaviour geneticists find families that have had the disorder across several generations. They draw blood or take cheek swabs from both affected and unaffected family members. Then they examine their DNA, looking for differences.

Geneticists and Psychologists

Geneticists and Psychologists are interested in the occasional variations found at particular gene sites in human DNA. Slight person-to-person variations from the common pattern gives clues to our uniqueness-why one person has a disease that another does not, why one person is short and another is tall, and why one is outgoing and another is shy. Most of our traits are influenced by many genes. How tall you are for example, reflects the size of your face, vertebrae, leg bones, and so forth-each of which may be influenced by different genes interacting with your environment. Complex traits such as intelligence, happiness and aggressiveness are similarly influenced by groups of genes.

Individualism

Giving priority to ones own goals over group goals and defining ones identity in terms of personal attributes rather than group identifications.

Evolution and Human Sexuality

Having faced many similar challenges throughout history, men and women have adapted in similar ways. Whether male or female, we eat the same foods, avoid the same predators, and perceive, learn and remember similarly. It is only in those domains where we have faced differing adaptive challenges, most obviously in behaviours related to reproduction, that we differ, say evolutionary psychologists.

Early Childhood Learning and Brain Development

Here at the junction of nature and nurture is the biological reality of early childhood learning. During childhood development, while excess connections are still on call, youngsters can most easily master such skills such as the grammar and accent of another language. Lacking any exposure to language before adolescence, a person will never master any language. Likewise, lacking visual experience during the early years, those whose vision is restored by cataract removal never achieve normal perceptions. The brain cells normally assigned to vision have died or diverted to other uses. The maturing brains rule: use it or lose it. Although normal stimulation during those early years is critical, the brains development does not end with childhood. Our neural tissue is ever changing and new neurons are born. If a monkey pushes a level with his finger several thousand times a day, brain tissue controlling that finger changes to reflect the experience. Human brains work similarly. Whether learning to keyboard or skateboard, we perform with increasing skill as our brain incorporates the learning.

Temperament and Heredity

Heredity predisposes one quickly apparent aspect of personality; Temperament, or emotional excitability. From the first weeks of life, some infants are reactive, intense and fidgety. Others are easygoing, quiet and placid. Difficult babies are more irritable, intense and unpredictable. Easy babies are cheerful, relaxed, and predictable in feeding and sleeping. Slow-to-warm-up infants tend to resist or withdraw from new people and situations. And temperament differences typically persist.

Heritable individual differences

Heritable individual differences need not imply heritable group differences. If some individuals are genetically disposed to be more aggressive than others, that needn't explain why some groups are more aggressive than others. Putting people in a new social context can change their aggressiveness .

Human Genome Research

Human Genome researchers have discovered the common sequence within human DNA. It is this shared genetic profile that makes us humans, rather than chimpanzees or tulips.

Variations across cultures

Human nature manifests human diversity. We see our adaptability in cultural variations among our beliefs and our values, in how we raise our children and bury our dead, and in what we wear (or whether we wear anything at all). When cultures collide, their differing norms often befuddle.

Separated Twins

Identical twins share an appearance, and the responses it evokes. Adoption agencies also tend to place separated twins in similar homes. Despite these criticisms, the sting twin study results helped shift scientific thinking towards greater appreciation of genetic influences. Separated fraternal twins do not exhibit similarities comparable to those of separated identical twins.

Genes

Our codes for life. Small segments of giant DNA molecules. All told, you have 20,000 to 25,000 genes. Genes can either be active (expressed) or inactive. Environmental events "turn on" genes, rather like hot water enabling a tea bag to express its flavour. When turned on, genes provide the code for creating protein molecules, our bodies building blocks.

Culture and Self

If as our solidarity traveler you prove yourself on your individualism, a great deal of you identity would remain intact. Individualists give relatively greater priority to personal goals and define their identity mostly in terms of personal attributes. They strive for personal control and individual achievement. Individualists share the human need to belong. They join groups, but they are less focused on group harmony and doing their duty to the group and being more self-contained, they more easily move in and out of social groups. Marriage is often for as long as they both shall love. If set adrift in a foreign land as a collectivist, you might experience a great loss of identity as you would lose those connections that have defined who you are. In a collectivist culture, group identifications provide a sense of belonging, a set of values, a network of caring individuals, an assurance of security. In return, collectivists have deeper more stable attachments to their groups: their family, clan or company.

Social Influences of Genes with Twins

If you have a fraternal twin who is divorced, your odds of divorcing are 1.6 times greater than if you have a non-divorced twin. If you have an identical twin who is divorced, the odds of your divorcing are 5.5 times greater. From such data, McGue and Lykken estimate that peoples differing divorce risks are about 50% attributable to genetic factors. Identical twins, more than fraternal twins, also report being treated alike. So, do their experiences rather than their genes account for their similarities? No, Studies have shown that identical twins whose parents treated them alike were not psychologically more alike than identical twins who were treated less similarly. In explaining individual differences, genes matter.

In what ways do parents and peers shape children's development?

In procreation, a women and a man shuffle their gene decks and deal with a life-forming hand to their child-to-be, who is then subjected to countless influences beyond their control. Parents, nonetheless, feel enormous satisfaction in their children's success, and feel guilt or shame over their failures. Freudian psychiatry and psychology have been among the sources of such ideas. Society has reinforced such parent blaming: Believing that parents shape their offspring as a potter molds clay, people readily praise parents for their children's virtues and blame them for their children's vices.

Gender

In psychology, the biologically and socially influenced characteristics by which people define male and female.

Gender and Aggression

In surveys, men admit to more aggression than women do. The aggression gender gap pertains to direct physical aggression, rather than verbal (relational) aggression. The male murder rate is higher for men. Throughout the world, hunting, fishing, and warring are primarily men's activities.Men also express more support for war

Individualism Outcomes

Individualism's benefits can come at the cost of more loneliness, higher divorce and homicidal rates, and more stress-related disease. Demands for more romance and personal fulfillment in marriage can subject relationships to more pressure.

How do individualist and collectivist cultures differ?

Individualists give priority to personal goals over group goals and tend to define their identity in terms of their own personal attributes. Collectivists give priority to group goals over individual goals and tend to define their identity in term of group identifications.

How does the biopsychosocial approach explain our individual development?

It considers all the factors that influence our individual development.

Variation of culture over time

Like biological creatures, cultures vary and compete for resources, and thus evolve over time. With a greater economic independence, todays women more often marry for love and less often endure abusive relationships. Although, today there is more divorce and depression. We are spending more hours at work and less hours with friends and family, and fewer hours asleep. And we cannot explain these changes by the human gene pool, which evolves far to slowly to account for high speed cultural transformations. Cultures vary, cultures change, and cultures shape our lives.

Developmental Similarities across groups

Mindful of how other differ from us, we often fail to notice the similarities predisposed by our shared biology. National stereotypes exaggerate differences that, although real, are modest. Regardless of our culture, we humans are more alike than different. Across the world, the children of warm and supportive parents feel better about themselves and are less hostile than are the children of punitive and rejective parents. Even difference within a culture are often easily explained by an interaction between our biology and our culture. To the extent that family structure, peer influences, and parental education predict behaviour in one these ethnic groups, they do so for the others as well. Cross-cultural research can help us appreciate both our cultural diversity and our human likeness.

Adoptive Homes

Moreover, in adoptive homes, child neglect and abuse and even parental divorce are rare. (Adoptive parents are carefully screened, natural parents are not.) So it is surprising that, despite a somewhat greater risk of psychological disorder, most adopted children thrive, especially when adopted as infants. Seven in eight report feeling strongly attached to one or both adoptive parents. As children of self-giving parents, they grow up being more self-giving and altruistic than average. Many score higher than their biological parents on intelligence tests, and most grow into happier and more stable adults. Regardless of personality differences between parents and their adoptees, most children benefit from adoption.

Our genetic Legacy

Our behavioural and biological similarities arise from our shared human *genome*, our common genetic profile. No more than 5% of the genetic differences among humans arise from population group differences. Some 95% of genetic variation exists within populations. Early humans disposed to eat nourishing rather than poisonous foods survived to contribute their genes to later generations. Similarly successful were those whose mating helped produce and nurture offspring. Over generations, the genes of individuals no so disposed tended to be lost from the human gene pool. The success enhancing genes continued to be selected, behavioural tendencies and thinking and learning, capacities emerged the prepared our stone age ancestors to survive and reproduce and send there genes into the future, and not you.

Gender Development

Our biological sex helps define our gender, the biological and social characteristics by which people define male or female. In considering how nature and nurture interact, gender is a prime example as nature and nurture together create our commonalities and differences, by considering other gender variations.

Experience and Brain Development

Our genes dictate our overall brain architecture, but experience fills in the details. Developing neural connections and preparing our brain for thought and language and other later experiences. Stimulation by touch our massage also benefits infant rats and premature babies. Handled infants of both species develop faster neurologically and gain weight more rapidly. By giving preemies massage therapy, neonatal intensive care units not help them go home sooner. Both nature and nurture sculpt our synapses. After brain maturation provides us with an abundance of neural connections, our experiences trigger a pruning process. Sights and smells, touches and tugs activate and strengthen connections. Unused neural pathways weaken. The result by puberty is a massive loss of unemployed connections.

Genetic Predispositions

Our genetically influenced traits, help explain both our shared human nature and our human diversity.

Gender Identity

Our sense of being male or female.

Moral Instincts

Our shared moral instincts survive from a distant past where we lived in small groups in which direct harm doing was punishment. For all such universal human tendencies, from our intense need to give parental care to our shared fear and lusts, evolutionary theory proposes a one-stop shopping explanation. As ancestors of this prehistoric genetic legacy, are predisposed to behave in ways that promoted our ancestors surviving and reproducing. But in some ways we are biologically prepared for a world that no longer exists. We love the taste of sweets and fats, which prepared our ancestors to survive famines, and we heed their call from store shelves, fast food outlets, and vending machines. With famine now rare in wester society, obesity is truly a growing problem. Our natural dispositions, rooted deep in history, are mismatched with todays junk food environment and todays threats such as climate change.

Parenting and the family environment

Parents to matter. The power of parenting is clearest at the extremes: the abused children who become abusive, the neglected who become neglectful, the loved but firmly handled who become self confident and socially competent. Yet in personality measures, shared environmental influences from the womb onward typically account for less than 10 percent of children's differences. The power to select a child's neighbourhood and schools gives parents an ability to influence the culture that shapes the child's group peers. And because neighbourhood influences matter, parents may want to become involved in intervention programs that aim at a school or neighbourhood.If the vapours of a toxic climate are seeping into that child's life, that climate- not just the child- needs reforming. Even so, peers are but one medium of cultural influence.

Gender and Social Power

People worldwide have perceived men as more dominant, forceful, and independent. Women are perceived as more deferential, nurturant, and affiliative. As leaders, men tend to be more directive, even autocratic; women tend to be more democratic. When people interact, men are more likely to utter opinions, women express support. Such behaviours help sustain social power inequalities. Men's power hunger is more expected and accepted.

The nurture of nature

Research reveals that nature and nurture together shape our development-every step of the way.

How do researchers use twin and adoption studies to learn about psychological principles?

Researchers compare the traits and behaviours of identical twins and fraternal twins. They also compare adopted children with their adoptive and biological parents. Some studies compare twins raised together or separately. These studies help us determine how much variation among individuals is due to genetic makeup and how much to environmental factors.

The nature of gender: our biology

Seven weeks after conception, you are anatomically indistinguishable of someone of the other sex. In adulthood, parts of the frontal lobes, an area involved in verbal fluency, are reportedly thicker in women. Part of the parietal cortex, a key area for space perception is thicker in men.

Shared Genes in Twins

Shared genes can translate into shared experiences. A person whose identical twin has Alzheimers disease, for example, has a 60% risk of getting the disease; if the affected twin in fraternal, the risk is 30%. To study the effects of genes and environments, hundreds of researchers have studied some 800,000 identical and fraternal twin pairs.

Heterosexuality and Attractiveness

Some desired traits, such as a women's youthful appearance, cross place and time. Evolutionary psychologists say that men who were drawn to healthy, fertile-appearing women; women with smooth skin and a youthful shape suggesting many childbearing years to come, stood a better chance of sending their genes into the future. And sure enough, men feel most attracted to women whose waists (thanks to their genes or their surgeons) are roughly a third narrower than their hips- a sign of future fertility. Moreover, just as evolutionary psychologists predicts, men are attracted to women whose ages in the ancestral past (when ovulation begins later than today) would be associated with peak fertility. Thus, teen boys are most excited by women several years older than themselves, mid-twenties men prefer women around their own age, and older men prefer younger women.

Cultural Neuroscience

Studies how neurobiology and cultural traits influence each other. People in collectivist cultures tended to carry a version associated with greater anxiety, though living in such cultures helps protect people from anxiety. Biological, psychological and social-cultural perspective intersect as we are biopsychosocial creatures.

Testosterone

Th most important of male sex hormones. Both males and females have it, but the additional testosterone in males stimulates the growth the male sex organs in the fetus and the development of the male sex characteristics during puberty.

Gender Typing

The acquisition of a traditional masculine or feminine role.

Genome

The complete instructions for making an organism, consisting of all the genetic material in that organism's chromosomes.

Culture

The enduring behaviours, ideas, attitudes, values, and traditions shared by a group of people transmitted from one generation to the next. Other animals exhibit the rudiments of culture. Primates have local customs of tool use, grooming and courtship. Younger chimpanzees and macaque monkeys sometimes invent custom and pass them on to their peers and offspring. But human culture does more. It supports our species survival and reproduction by enabling social and economic systems that give us an edge. Thanks to our mastery of language, we humans enjoy the preservation of innovation. Moreover, culture enables efficient division of labour. Across cultures, we differ in our language, our monetary systems, our sports, which fork-if any-we eat with, even which side of the road we drive on. But beneath these differences is our great similarity, our capacity for culture. Culture transmits the customs and beliefs that enable us to communicate, to exchange money for things, to play, to eat, and to drive with agreed upon rules and without crashing into one another.

Adoption and personalities

The environment shared by a family's children has virtually no discernible impact on their personalities. Two adopted children reared in the same home are no more likely to share personality traits with each other than with the child down the block. Heredity shapes other primates personalities, too. Macaque monkeys raised by foster mothers exhibit social behaviours that resemble their biological rather than their foster mothers. Add all this to the similarity of identical twins, whether they grew up together or apart, and the effect of a shared reared environment seems shockingly modest.

The Genetic Effect

The genetic effect appears in physiological differences. Anxious, inhibited infants have high and variable heart rates and a reactive nervous system. When facing new or strange situations, they become more physiologically aroused. One form a gene that regulates the neurotransmitter serotonin predisposes a fearful temperament and, in combination with unsupportive caregiving, an inhibited child. Such evidence adds tot he emerging conclusion that our biological rooted temperament helps from our enduring personality.

Interaction

The interplay that occurs when the effect of one factor (such as environment) depends on another factor (such as heredity).

Cultural Influences

The mark of our species is our ability to learn and adapt. We come equipped with a huge cerebral hard drive ready to receive many gigabytes of cultural software.

Shared-Environment Effect

The minimal shared-environment effect does not mean that adoptive parenting is a fruitless venture. The genetic leash may limit the family environments influence on the personality, but parents to influence their children's attitudes, values, manners, faith, and politics. A pair of adopted children or identical twins will, especially during adolescence, have more similar religious beliefs if reared together.

The human building blocks

The nucleus of every human cell contains chromosomes, each of which is made up of two strands of DNA connected in a double helix. Genetically speaking, every other human is nearly your identical twin.

Natural Selection

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.Organisms varied offspring compete for survival. Certain biological and behavioural variations increase their reproductive and survival chances in their environment. Offspring that survive are more likely to pass their genes to ensuing generations. Thus, overtime, population characteristics may change.

Heritability

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. Using twin and adoption studies, behaviour geneticists can mathematically estimate the heritability of a trait, the extent to which variation among individuals can be attributed to their differing genes.It means that the genetic influence explains 50% of the observed variation among people. We can never say what percentage of an individuals personality or intelligence is inherited. It refers to the extent to which difference among people are attributable to genes. Difference due to genes.

X Chromosome

The sex chromosome found in both men and women. Females have two X chromosomes and males have one. An X chromosome from each parent produces a female.

Y Chromosome

The sex chromosome found only in males. When paired with an X chromosome from the mother, it produces a male child.

Epigenetics

The study of molecular mechanisms by which environments trigger genetic expression. Although genes have the potential to influence development, environmental triggers can switch the on of off. The study of influences on gene expression that occur without a DNA change.

Evolutionary Psychology

The study of the evolution and the behaviour and the mind, using principles of natural selection.

Behaviour Genetics

The study of the relative power and limits of genetic and environmental influences on behaviour. The study of our differences and weigh the effects and interplay of heredity and environment.

Molecular Genetics

The subfield of biology that studies the molecular structure and function of genes. It seeks to identity specific genes influencing behaviour. Most human traits are influenced by genes. For example, twin and adoption studies tell us that heredity influences body weight, but there is no single "obesity gene". More likely, some genes influence how quickly the stomach tells the brain it is full. Others might dictate how much fuel the muscles need, how many calories are burned off by fidgeting, and how efficiently the body converts extra calories into fat. Given that genes typically are not solo players, a goal of molecular behaviour genetics is to find of the genes that together orchestrate traits such as body weight, sexual orientation, and extraversion.

Social Learning Theory

The theory that we learn social behaviour by observing and imitating and by being rewarded or punished. Assumes that children learn gender identity

Gene interaction

To say the genes and experience are both important is true. But more precisely, they interact. Environments trigger gene activity. And our genetically influenced traits evoke significant responses in others. Evocative interactions may help explain why identical twins raised in different families recall their parents warmth as remarkably similar- almost as if they had the same parents. Fraternal twins have more differing recollections of their early life- even if reared in the same family. Moreover, a selection effect may be at work. As we grow older, we select environment s well suited to our natures.

Twin and Adoption Studies

To scientifically tease apart the influences of environment and hereditary, behaviour genetics would need to design two types of experiments. The first would control the home environment while varying hereditary. The second would control heredity while controlling the home environment. Such experiments, with human infants, would be unethical, but happily for our purposes, nature has done this work for us.

Communal Solidarity

Valuing communal solidarity means placing a premium on preserving group spirit and ensuring that others never lose face. What people say not only reflects what they feel but also what they presume. Avoiding direct confrontation, blunt honesty, and uncomfortable topics, collectivists often differ to others wishes and display a polite, self-effacing humility.

Women and Male Attractiveness

Women prefer stick-around dads over lively cads. They are attracted to men who seem mature, dominant, bold, affluent, with a potential for long term mating and investment in their joint offspring. From an evolutionary perspective, such attributes connote a man's capacity to support and protect a family. There is a principle at work here, say evolutionary psychologists: Nature selects behaviours that increase the likelihood of sending ones genes into the future. As mobile gene machines, we are designed to prefer whatever world out for our ancestors in there environments. They were predisposed to act in ways that would leave grandchildren; had they not been, we wouldn't be here. And as carriers for their genetic legacy, we are similarly predisposed. Without disputing natures selection of traits that enhance gene survival, critics see some problems with this explanation of our mating preferences. They believe that the evolutionary perspective overlooks some important influences on human sexuality

Gender Schema

Your framework for organizing boy-girl characteristics. This gender schema then became a lens for which you viewed your experiences. Social learning shapes gender schemas.