Nature, Nurture and Human Diversity

• Our differences as humans include our personalities, interests, cultures, and family backgrounds

• Similarities include our common biological heritage, our shared brain architecture, our ability to use language, and our social behaviors

• Major theme in psych- is it our heredity, called our nature, or external influences, called our nurture. You are smart enough to know it is both- nature via nurture.

Behavioral Genetics

• Researchers who specifically study genetic and environmental influences on behavior are called behavior geneticists

• The term environment refers to nongenetic influence

Behavioral Genetics• Master plan for development-

in chromosomes; 46 total, 23 from each parent, Each is composed of the molecule DNA.

• If Chromosomes are chapters of heredity, genes that make us uniquely distinctive are genes. Complete instructions on making an organism is referred to a as the human genome.

Nature vs. Nurture- Twin and Adoption Studies

• To study genetic influence; researchers use identical and fraternal studies

• Identical- twins that develop from same egg

• Fraternal- twins that develop from different eggs- no more genetically alike than siblings

• Identical twins are more alike than fraternal when it comes to personality

• Twin pairs treated alike; But similarities could not be attributed to treatment

• When twins are raised apart, researchers can see the influence of environment

• Personalities of adopted children do not resemble adoptive parents. However, shows parenting matters by scoring higher than biological parents on intelligence tests

How does temperament influence Heredity?

• Inborn personality that shows emotional excitability- temperament which DOES endur over time.

• From the first weeks of life, difficult babies- irritable, intense, unpredictable, while easy babies display cheerful, relaxed, and predictable

• Faced with a new or strange situation, anxious infants become more physiologically aroused than less excitable infants.

Interaction of Genes and Environment

• The extent to which variation among individuals is attributed to genes is called heritability. Heritable individual differences do not necessary imply heritable group differences.

• Genes are self regulating; rather than acting as a blueprint leading to same result, they react to the environmental context.

• Human differences thus are always the result of genetic and environmental influences

Interaction of Genes and Environment

• Thus, we are the products of the interaction of our genetic predisposition and our surrounding environment

• Environments trigger activity in genes and out genetically influenced traits evoke responses in other people. This may explain why fraternal twins recall greater variations in their early family life than do identical twins

• Molecular genetics- the subfield of biology that seeks to identify some of the many genes that influence normal human traits

Evolutionary Psychology- Understanding Human Nature

• Evolutionary psychologists- Researchers who study natural selection and the adaptive nature of human behavior

• Focus on what makes people alike• Natural Selection- traits that lead

to increased reproduction and survival will be most likely to be passed on to succeeding generations

• Genetic mutations are random errors in genetic replication that are the source of all genetic diversity

Evolutionary Psychology- Understanding Human Nature

• Genetic constraints on human behavior are genetically looser than those on animal behavior. The human species’ ability learn and therefore to adapt in responding to different environments contributes to our fitness, defined as our ability to survive and reproduce. Because of our genetic legacy, we love the tastes of sweets and fats, which we tend to store, even though famine is unlikely in industrialized societies.

•

Gender Differences in Sexuality and Mating Preferences

• Gender- characteristics that make us Male of Female- These characteristics are subject to social and biological influences.

• Males are more likely to engage in casual impulsive sex, and they are more likely to initiate sexual activity. This is an example of a gender difference.

• Cross cultural research reveals that men judge women as more attractive if they have a youthful appearance, whereas women judge men who appear dominant, bold, affluent as more attractive.

Criticism of Evolutionary Psychology

• Critics argue that it often works backward to propose a hindsight explanation

• Gender differences in mate preferences are largest in cultures characterized by greater gender inequality.

• Evolutionary Psychologists counter the criticisms by noting the sexes, having faced similar adaptive problems, are more alike than they are different. They also note that evolutionary principles offer testable predications.

Parents and Peers• Prenatal Development-

Environmental influences began during this period.

• Rosenweig and Krech- discovered that rats raised from a young age in enriched environments had thicker brain cortexes than animals raised in isolation.

• Experience shapes the brain by preserving activated neural connections and allowing connections degenerate. This process called pruning, results in a massive loss of unused connections by puberty

Whose more important? Parents and Peers

• The idea that parents shape their children’s futures come from Freudian psychiatry and psychology

• Parents influence- political attitudes, personal manners, and religious beliefs

• In areas such as personality , the environment siblings share at home accounts for less than 10 percent of their differences.

• Experiments with peers have powerful effect on how children develop, partly as a result of a selection effect by which kids seek out others with similar attitudes and interests.

Cultural Influences • Culture- the enduring behaviors,

ideas, attitudes, values, and traditions of a group of people and transmitted from one generation to the next

• Human culture preserves innovation, which is deprived of our mastery of language, so that we can pass it on to future generations. Culture also enables an efficient division of labor.

• All cultural groups evolve their own rules for expected behavior, called norms

• One such rule involves the buffer zone that people maintain around their bodies, called personal space

• The speed at which culture changes is much faster than the pace of evolutionary changes in the human gene pool

Individualist vs. Collectivist Cultures

• Cultures based on individualists value personal control and individual achievement. These cultures include North America, Western Europe, and Australia

• In contrast, cultures based on collectivism value interdependence, tradition, and harmony. Examples of these cultures include Korea, Japan, and China.

• Picture represents collectivist act

Individualist vs. Collectivist Cultures

• Individualist culture cons- more loneliness, homicide, stress

• Individualist foster independence, while collectivist cultures value emotional closeness

• Collectivist grow up with a sense of family self which states that what shames or honors the person also shames or honors the family.

• In general, differences between groups are smaller than person- to- person differences within a group

Gender Development• Among your 46

chromosomes, 45 are uni-sex. • Woman’s characteristics-

more fat, less muscle, few inches shorter – More likely to suffer depression, anxiety, and eating disorders.

• Men’s Characteristics- more suicide, alcohol dependence, autism, color blindness, ADHD, antisocial personality disorder

Gender Development• Aggression is defined as physical or

verbal behavior that is intended to hurt someone.

• Throughout the world, men are likely than women to engage in hunting, fighting, and warring.

• The aggression gender gap pertains to physical rather than verbal aggression.

• Men’s Perception vs. Women's Perception- Men- dominant, forceful, independent, directive vs. Women’s- deferential, nurturing, affiliative

• These perceived differences occur throughout the world.

Gender Development• According to Carol Gilligan, women

are concerned than men in making connections with others

• This difference is noticeable in how children play, and it continues throughout the teen and adult years. Girls play in groups that are smaller and less competitive than boys’ groups.

• Because they are more interdependent, women are likely to use conservation to explore relationships, while men are likely to use conversation to communicate relationships.

Gender Development

• Women tend and befriend- for example, they turn to others for support, especially when coping with stress.

• Gender differences in power, connectedness, and other traits peak in late adolescence and early adulthood. By age 50, the differences have decreases

Role of Sex Hormones in Biological Development

• The 23rd pair of chromosomes determines the developing person’s sex. Mother contributes a X chromosome; Father contributes Y, the testes begin producing the hormone testosterone. In about the seventh, this hormone initiates the development of external male organs.

• Sex chromosomes control hormones that influence the brain’s wiring. In adulthood, part of the frontal lobe, an area involved verbal fluency, is thicker in women. Part of the brain’s parietal cortex, a key area for space perception, is thicker in men.

Importance of Gender Roles• Our expectations about the

way men and women behave define our culture’s gender roles.

• Gender roles are not rigidly fixed by evolution, as evidenced by the fact that they vary across cultures and over time. Nomadic society- minimal division of labor by sex; by contrast, in agricultural societies, women remain close to home while men roam freely, herding cattle or sheep.

Importance of Gender Roles• Our individual sense of being male or

female is called our gender identity. The degree to which we exhibit traditionally male of female traits is called gender typing.

• According to social learning theory, children learn gender- linked behaviors by observing and imitating others and being rewarded or punished. When families discourage gender typing, children do organize themselves into boy and girl worlds.

• Children also learn from their gender schemas what it means to be male or female and adjust their behavior accordingly, thereby demonstrating that cognition is important in the formation of gender identity

Reflections on Nature vs. Nurture• As brute strength becomes less

relevant to power and status, gender roles are converging.

• We are the product of both nature and nurture, but we are also s system that is open. We know this because a biopsychosocial approach to development shows that no single factor is all powerful.

• The principle that we should prefer the simplest of competing explanations for a phenomenon called Occam’s Razor

25

Nature, Nurture, and Human Diversity

Similarities Differences

Genes: Same set of chromosomes

Genes: Genetic anomalies may make us

different

Biology: Organs and body functions same

Biology: May change during development

Brain: Same brain architecture

Brain: Asymmetry of brain across genders

Behaviors: Speak language

Behavior: Speak different languages

26

Culture and the Self

27

Reflections on Nature and Nurture